BRPI0620717A2 - process for separating at least one propylene glycol from a mixture - Google Patents

Abstract

PROCESS TO SEPARATE AT LEAST ONE GLYCOL PROPYLENE FROM A MIXTURE. The present invention relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising: (I) evaporating a mixture in at least two stages of evaporation and / or distillation at decreasing operating pressures of the evaporators and / or distillation columns obtaining mixture (M ') and mixture (M "); (II) separating a mixture (M') obtained in (I) in at least one other distillation step , obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than 30% by weight of water.

Description

"Process for Separating at Least a Propylene Glycol from a Mixture"

Of the publications on the subject of propylene oxide preparation, there are only a few that address wastewater treatment and recovery of by-products from the reaction mixture.

WO 2004/000773 relates to a process for separating 1-methoxy-2-propanol and 2-methoxy-1-propanol from aqueous compositions, comprising: removing water from the aqueous composition comprising 1-methoxy-2-propanol and 2- methoxy-1-propanol to a concentration of 1-methoxy-2-propanol and 2-methoxy-1-propanol of at least 90 weight percent in total and isolation of 1-methoxy-2-propanol, 2-methoxy-1 -propanol or mixtures thereof by distillation. According to WO 2004/000773, removal of water from aqueous composition can be accomplished by membrane separation. Thus the aqueous composition comprising 2-methoxy-propanol and 1-methoxy-2-propanol is contacted with a semi-permeable hydrophilic membrane in a suitable apparatus in either a liquid phase as a pervaporization step or a gas phase as a phase. vapor permeation. Through the semipermeable membrane a pressure difference is established. The permeate will substantially contain water and only a minor amount of del-methoxy-2-propanol and 2-methoxy-1-propanol. According to WO 2004/000773, the largest amount of 1-methoxy-2-propanol and 2-methoxy-1-propanol fed to the apparatus will not pass through the membrane and can be collected as a trap with a reduced water content.

US 5,599,955 provides an integrated process for the production of propylene oxide from an alternative feed stream such as synthesis gas. In the process, propylene oxide is produced from a feed stream comprising hydrogen and a carbon oxide. The propylene stream is epoxidized with hydrogen peroxide that has been produced from hydrogen separated from a portion of the feed stream. The water stream used by the epoxidation reaction is treated to remove heavy components and returned to the hydrogen peroxide production zone. Recycling waste water from the epoxidation reaction zone and removing heavy compounds eliminates a low value water stream and recovering heavy hydrocarbons from it produces a valuable by-product. The wastewater stream is passed into a separation zone such as an evaporator, a distillation zone or a sorption zone.

US 2002/010378 describes a composite process for subjecting ethylene to gas phase catalytic oxidation thereby obtaining ethylene oxide and causing this ethylene oxide to react with water thereby obtaining ethylene glycol. In ethylene glycol production by providing the aqueous ethylene glycol solution to a multi-effect evaporator concentration treatment, the method contemplated by US2002 / 010378 for the production of ethylene glycol comprises use as the heating source of hair. least one specific step of the current generated in the multi-effect evaporator.

US 6,288,287 describes a process for preparing a glycerol from a crude glycerol comprising a glycerol, a diol and water, comprising feeding the crude glycerol to a preparation apparatus comprising two or more serially connected rapid vaporizing towers and a tower of distillation connected to a final rapid vaporization tower, in which a bottom fraction of each rapid vaporization tower is fed to a subsequent rapid vaporization tower. According to US 6,288,287, there is provided a process for preparing a glycerol from a crude glycerol comprising two or more serially connected rapid vaporizing towers and a distillation tower connected to a final rapid vaporizing tower, in which a fraction The bottom of each Quick Vapor Tower is fed to a subsequent Quick Vapor Tower.

US 5,269,933 and EP 0,532,905 A describe a method for separating a mixture of an organic fluid and water, such as carboxylic acids, including, for example, acetic acid, propionic acid, aromatic amines, including, for example aniline, phenol, and glycerin. The method is a combination of distillation, selective pervaporization of water and reverse osmosis and is particularly suitable for glycol and water separation. The process according to US 5,269,933 comprises distilling the mixture, performing selective pervaporization of water to bottom product obtained from the distillation step to obtain a residue and permeate, applying a reverse osmosis to at least one distillate to obtain a residue and permeate, and feeding the residue obtained from reverse osmosis to perform the distillation step thereon, such that the secreted organic fluid is present as the selective water pervaporization residue, and the secreted water is present as the permeate of the permeate. selective water pervaporization step as well as the reverse osmosis step permeate.

According to EP 0 324 915 A, valuable materials may be separated from aqueous solutions by extraction and / or distillation; The solution may be previously concentrated by reverse osmosis. Valuable materials are separated only by distillation after solution concentration by optionally multistage reverse osmosis. According to the process described in EP 0.324.915 A, the valuable material leaves the distillation column with the bottom stream or the top stream.

US 6,712,882 describes a process for treating wastewater from an industrial process to produce propylene oxide, the process of which involves the steps of: (a) subjecting wastewater to a multi-effect evaporation treatment resulting in a top fraction aqueous and a liquid bottom fraction containing the nonvolatile contaminants; and (b) condensing at least part of the vaporous top fraction into a liquid stream that is subjected to an extraction treatment resulting in a top stream containing volatile residual organic material and purified water as the liquid stream.

Accordingly, the prior art describes various options for treating wastewater comprising organic compounds.

An object of the present invention is to provide a process for recovering propylene glycol from a mixture comprising propylene glycol and water.

Still another object of the present invention is to provide a process for recovering propylene glycol from a mixture comprising propylene glycol and water with improved yield and improved long lasting performance.

Still another object of the present invention is to provide a process for recovering propylene glycol from a mixture comprising propylene glycol and water, wherein this mixture is obtained as a byproduct of an epoxidation process wherein propene is oxidized to obtain propylene oxide.

Summary of the invention

Therefore, the present invention provides a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating the mixture in at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixture (M ");

(II) separating the mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water,

wherein the mixture (M ") is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than that 30% by weight of water;

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixing

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water,

wherein the mixture (M-I) is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixing

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water,

wherein the mixture (M ") and mixture (MI) are combined and further separated into mixture (M-Ia) comprising at least 90 wt.% water and mixture (M-Ib) comprising less than 95 wt.%. water through reverse osmosis.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixing

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (IVI-I) comprising at least 70% by weight of water and a mixture (M-II) comprising less than 30% by weight of water;

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step,

wherein the mixture (M-I) is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixing

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water,

wherein the mixture (M) is obtained as a byproduct in a propylene epoxidation process comprising the step of

(a) reacting propylene with a hydroperoxide in the presence of at least one solvent and at least one catalyst to obtain a mixture (M-a) comprising propylene oxide.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture in at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixing (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water,

where in stage (I) three stages of evaporation (El) through (E3) are performed at decreasing operating pressures in the ranges of

(El) 150 to 550 kPa at a temperature of 111 to 155 ° C,

(E2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(E3) 70 to 400 kPa at a temperature of 90 to 144 ° C.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns giving mixture (M ') and mixture (M "); (II) separate a mixture ( M ') obtained in (I) in at least one further distillation step, obtaining a mixture (MI) comprising at least 70 wt% water and a mixture (M-II) comprising less than 30 wt% water ;

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step;

where in stage (I) three stages of evaporation (El) through (E3) are performed at decreasing operating pressures in the ranges of

(El) 150 to 550 kPa at a temperature of 111 to 155 ° C,

(E2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(E3) 70 to 400 kPa at a temperature of 90 to 144 ° C.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than that 30% by weight of water;

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step,

wherein the mixture (M-I) is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis,

where in stage (I) three stages of evaporation (El) through (E3) are performed at decreasing operating pressures in the ranges of

(El) 150 to 550 kPa at a temperature of 111 to 155 ° C,

(E2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(E3) 70 to 400 kPa at a temperature of 90 to 144 ° C.

The present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than that 30% by weight of water;

wherein the mixture (M-I) is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis;

wherein the mixture (M) is obtained as a byproduct in a propylene epoxidation process comprising the step of

(a) reacting propylene with a hydroperoxide in the presence of at least one solvent and at least one catalyst to obtain a mixture (M-a) comprising propylene oxide; and

where in stage (I) three stages of evaporation (El) through (E3) are performed at decreasing operating pressures in the ranges of

(El) 150 to 550 kPa at a temperature of 111 to 155 ° C,

(E2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(E3) 70 to 400 kPa at a temperature of 90 to 144 ° C. Detailed Description of the Invention

According to the present invention, the process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol comprises two steps. In a first step (I), a mixture (M ') is obtained, which is then subjected to a second step (II). According to the present invention, the process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol comprises

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water.

In step (I), a mixture (M ") is obtained which may be further separated by reverse osmosis.

The present invention therefore also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than 30% by weight of water;

wherein the mixture (M ") is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis.

According to step (I), the mixture is evaporated in at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixture (M "). Preferably, the mixture is evaporated at 2 to 6 stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns, in particular 3, 4 or 5 stages of evaporation and / or distillation, preferably 3 stages. evaporation and / or distillation It is also possible to combine the last stage of evaporation or distillation according to step (I) with distillation according to step (II).

Evaporators and / or distillation columns are operated at decreasing operating temperatures and pressures. Preferably a first stage of evaporation or distillation is operated at a pressure of 150 to 550 kPa, preferably 200 to 500 kPa, in particular 250 to 450 kPa, for example 280, 290, 300, or 320 kPa bar; and at a temperature of 111 to 156 ° C, preferably 120 to 152 ° C, in particular 127 to 148 ° C, more preferably 130 to 140 ° C.

Preferably a second stage of evaporation or distillation is operated at a pressure of 130 to 500 kPa, preferably 140 to 400 kPa, in particular 150 to 300 kPa, for example 180, 190, 200, 210, or 220 kPa; and at a temperature of from 107 to 152 ° C, preferably 110 to 144 ° C, in particular IIIa to 134 ° C, more preferably 118 to 125 ° C.

Preferably a third stage of evaporation or distillation is operated at a pressure of 70 to 400 kPa, preferably 80 to 300 kPa, in particular 90 to 200 kPa, for example 100, 110, 120, 130, or 140 kPa; and at a temperature of 90 to 144 ° C. preferably 95 to 135 ° C, in particular 90 to 125 ° C, more preferably 105 to 1150 ° C.

In case a fourth stage of evaporation and / or distillation is carried out, the fourth stage of evaporation and / or distillation is preferably operated at a pressure of 100 to 150 kPa, preferably 20 to 120 kPa, in particular 30 to 100 kPa, for example. 40, 50, 60, 70, or 80 kPa; and at a temperature of 70 to 115 ° C, preferably 75 to 110 ° C, in particular 75 to 100 ° C.

Mixture (M) is treated in a series of subsequent evaporation and / or distillation treatments at progressively lower pressures.

Due to the pressure gradient between the subsequent stages there is a resulting decrease in boiling temperature in successive stages. This gradient allows condensing vapors from one section to be used as the heating medium for the next stage. Thus, a stage as used in this context is a section of a multi-stage evaporator heated preferably by steam, preferably water vapor, and also releases steam to a subsequent section, where it is used to provide at least part of the required evaporation heat. . The remaining liquid product from one stage is preferably the most concentrated liquid feed for the next stage.

The at least two stages of evaporation and / or distillation used for the purpose of the present invention may be operated in a so-called feed mode hereinafter: the feedstock feed is introduced in the first stage and is passed from stage to stage parallel to steam flow, preferably water vapor flow, while the liquid "product" is removed from the last stage. It is also possible to operate the evaporation process in a so-called back current mode. Alternatively, multistage evaporation may be performed in a so-called parallel mode, which involves dividing the wastewater supply over the different stages of the evaporation train.

In general, a stage will have a vapor outlet and a liquid outlet as well as heating means to provide the evaporative heat. Such heating means could, for example, be in the form of a re-evaporator arranged in the liquid (i.e. bottom) portion of the stage. Alternatively, heating means may be in the form of heating surfaces such as plates or tubes. All such heating means have in common that their heat input is provided by the steam from the previous stage. Heat supply to the first stage of a multi-stage evaporator will normally be provided by fresh water vapor or another process stream capable of providing heat at the correct temperature. Water vapor recovered as the top fraction of the last stage is suitably condensed with cooling water. The condensate stream thus obtained can then be passed on in the subsequent step, while the recovered condensation heat can be applied elsewhere in the process or removed by a cooling means.

Generally, all evaporators and distillation columns may be used for the process of the invention. Preferably downward film evaporators such as re-evaporators and tray-equipped towers, especially Thormann® trays are used.

In accordance with the present invention, mixture (M) comprises water and propylene glycol. Preferably, the mixture (M) comprises less than 99.9 wt% of water, for example 70 to 99.5 wt% of water, preferably 80 to 99.0 wt% of water, more preferably 90 to 98 % by weight of water. Mixture (M) further preferably comprises less than 30 wt% propylene glycol, for example 0.01 to 25 wt% propylene glycol, preferably 0.1 to 20 wt% propylene glycol, more preferably 0.5 to 15 wt% propylene glycol, in particular 1.0 to 10 wt% propylene glycol, much more preferably 1.5 to 5 wt% propylene glycol.

Mixture (M) may additionally comprise organic solvents or additionally organic compounds, preferably in an amount of less than 10 wt%, in particular less than 5 wt%.

Mixture (M ') obtained in step (I) comprises propylene glycol and water. Preferably mixture (M ') comprises 80 to 99.9 wt% water and 2.5 to 15 wt% propylene glycol, more preferably 85 to 99.0 wt% water and 5 to 12.5 wt%. propylene glycol, in particular 88 to 95 wt.% water and 6 to 10 wt.% propylene glycol.

Mixture (M ") obtained in step (I) comprises at least 70% by weight of water. Preferably mixture (M") comprises 90 to 99.99% by weight of water and 0.01 to 0.5% by weight of water. propylene glycol, more preferably 95 to 99.9 wt% water and 0.05 to 0.25 wt% propylene glycol, in particular 98 to 99.5 wt% water and 0.07 to 0.1 % by weight of propylene glycol.

According to step (II), mixture (M ') obtained in (I) is separated into at least one further distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M -II) comprising less than 30% by weight of water.

Distillation according to step (II) may be performed on a suitable distillation column. Preferably a descending film evaporator such as re-evaporator and a tower equipped with trays, especially Thormann trays is used.

Preferably, mixture (M-I) is obtained as the top stream and mixture (M-II) is obtained as the distillation bottom stream.

According to the present invention, mixture (M-I) comprises at least 70 wt% water and a mixture (M-II) comprises less than 30 wt% water. Preferably mixture (MI) comprises 90 to 99.99 wt% water and 0.01 to 0.5 wt% propylene glycol, more preferably 95 to 99.9 wt% water and 0.05 to 0, 25 wt% propylene glycol, in particular 98 to 99.5 wt% water and 0.07 to 0.1 wt% propylene glycol.

Preferably mixture (M-II) comprises 2.5 to 20 wt% water and 50 to 90 wt% propylene glycol, more preferably 5 to 15 wt% water and 60 to 80 wt% propylene glycol, in particular 7 to 12% by weight of water and 65 to 75% by weight of propylene glycol.

In accordance with the present invention, step (II) of the process according to the present invention may be carried out directly after step (I). It is also possible that mixture (M ') obtained in step (I) is further treated before step (II). The mixture may be heated or cooled, or otherwise suitably treated.

It is also possible according to an alternative embodiment that mixing (M ') is directly introduced into a reverse osmosis separation step. It is also possible that mixture (M ') obtained in step (I) is further treated prior to the separation step by reverse osmosis. The mixture may be heated or cooled, or otherwise suitably treated.

The present invention therefore provides a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water.

According to an alternative embodiment, the present invention relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixing

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than that 30% by weight of water;

wherein the mixture (M ") is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis.

According to an alternative embodiment, the present invention relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water,

wherein the mixture (M ") and mixture (MI) are combined and further separated into mixture (M-Ia) comprising at least 90 wt.% water and mixture (M-Ib) comprising less than 95 wt.%. water through reverse osmosis.

According to another embodiment of the present invention, the process may further comprise step (III) of:

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step.

According to step (III), the at least one propylene glycol is separated from the mixture (M-II) in at least one other distillation step. Preferably, step (III) is performed using a partition wall column. In step (III), mixture (M-III) and a mixture containing essentially propylene glycol are obtained. In a preferred embodiment, in step (III), mixture (M-IIIa), mixture (M-IIIb) and a mixture (M-IIIc) containing essentially propylene glycol are obtained. Preferably, mixture (M-III) or mixture (M-IIIa) comprises 10 a. 70 wt% water, preferably 15 to 55 wt% water, in particular 20 to 40 wt% water, for example 30 to 35 wt% water.

Preferably the at least one propylene glycol, preferably as a mixture (M-IIIc), is obtained in a purity of greater than 95%, preferably greater than 98%, in particular greater than 99%, for example 99.1%. 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 100%, much more preferably within a 99.5 to 99.9% range. Preferably mixture (M-IIIc) is obtained as a side stream.

Distillation according to step (III) may be performed in one, two, three or more stages, preferably in one or two stages, more preferably in one stage.

All suitable distillation columns may be used for distillation according to step (III). Preferably a split wall column equipped with 500 m 2 / m3 gauze filling provided by Koch Glitsch, Montz, Sulzer and a 1,600 kPa water vapor operated down-film evaporator.

The distillation column used in step (III) is preferably operated at a pressure of 1 to 15 kPa, preferably 3 to 10 kPa, for example 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, or 9 kPa; and a background temperature of from 120 to 200 ° C, preferably 140 to 180 ° C, in particular from 160 to 170 ° C.

Preferably, propylene glycol, preferably as a mixture (M-IIIc), is obtained as a distillation side stream. Preferably, mixture (M-IIIa) is obtained as a top stream of distillation. It is also possible in the context of the present invention that other currents are obtained as background currents. Preferably mixture (M-IIIb) is obtained as background stream.

In accordance with the present invention, step (III) of the process according to the present invention may be performed directly after step (II). It is also possible that mixture (M-II) obtained in step (II) is further treated prior to step (III). The mixture may be heated or cooled or otherwise suitably treated. It is also possible for mixture (M-II) to be combined with at least one other mixture obtained in the process according to the present invention prior to step (III).

Therefore, the present invention also provides a process as described above, wherein the process further comprises the step of

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step. In accordance with the present invention, the mixture (MI) obtained in step (II) may be further separated into mixture (M-Ia) comprising at least 90% by weight of water and mixture (M-Ib) comprising less than 95%. % by weight of water by reverse osmosis.

In accordance with the present invention, it is also possible that mixture (M ") obtained in step (I) is directly subjected to an additional separation step by reverse osmosis. In this case, mixture (M") is separated into mixture ( M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis.

It is also possible to combine mixture (M ") and mixture (M-I) and then subject the combined mixtures to reverse osmosis separation.

The reverse osmosis separation step is preferably performed at an operating pressure of 3,000 to 12,000 kPa, preferably from 6,000 to 11,000 kPa, more preferably from 8,000 to 10,000 kPa, especially about 9,000 kPa. The reverse osmosis separation step is preferably carried out at a temperature of from 20 to 80 ° C, more preferably from 30 to 60 ° C, preferably from 35 to 45 ° C especially from about 38 to 42 ° C, for example. 39 ° C, 40 ° C, or 41 ° C.

In accordance with the present invention, the reverse osmosis separation step is preferably performed using 2 to 8 stages. Reverse osmosis is preferably performed using 2 to 8 module stages connected in parallel, preferably using 4 to 6 module stages, for example 5 module stages.

At each stage, the feed to hold ratio is preferably from about 20 to about 60, for example 25 to 55 or 50.

Preferably, one of four different types of reverse osmosis modules, which are generally used for reverse osmosis processes, are used for the process of the present invention. Preferably tubular, plate and frame, spiral, and hollow fiber modules. they're used.

Tubular membranes are non self-supporting membranes. They are located on the inner side of a tube, they are made of a material that is the support layer for the membrane. Because the location of tubular membranes is within a tube, flow in a tubular membrane is usually from the inside out. Tubular membranes generally have a diameter of about 5 to 15 mm.

With capillary membranes the membrane serves as a selective barrier that is strong enough to withstand filtration pressures. Because of this, the flow through the capillary membranes can be both inside out and inside out. The diameter of capillary membranes is much smaller than that of tubular membranes, namely 0.5 to 5 mm. Because of the smaller diameter the obstruction probabilities are much higher with a capillary membrane.

Spiral membranes consist of two membrane layers, positioned over a permeate collecting tissue. This membrane envelope surrounds a centrally positioned permeate drain. This makes the filling density of the membranes higher. The feed channel is positioned at a moderate height to prevent clogging of the membrane unit.

Pressurized mixture flows along the outer surface of the membrane sleeves. A solution penetrates and flows into the spiral sleeve toward the center tube leading out of the module.

Membranes consisting of flat plates are called pad-shaped membranes. The name cushion-shaped membrane comes from the cushion-like shape that the two membranes have when packaged together in a membrane unit. Inside the 'cushion' is a support plate, which provides solidity.

Within a module, multiple pillows are positioned at a certain distance between them, which depends on the dissolved solids content of the solution. The solution flows through the membrane from the inside out. When treatment is performed, the permeate is collected in the space between the membranes, where removed away through drains.

Hollow fiber membranes are membranes with a diameter of below about 0.1 μηι.

As membranes, all membranes with sufficient stability against organic compounds for example membranes having an active layer of cellulose acetate, composite or polyamide may be used. Preferably polyamide active layer membranes as spiral membrane modules are used.

According to a preferred embodiment of the present invention, the mixture (MI) obtained in step (II) - or according to an alternative embodiment mixture (M ") obtained in step (I") or mixture (M ") combined with mixture ( MI) - may be separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis.

Mixture (M-Ia) comprises at least 90% by weight of water. Preferably mixture (M-Ia) comprises at least 95 wt% water, more preferably at least 98 wt% water, in particular at least 99 wt% water, for example 99.3 wt%, 99%. 4 wt%, 99.5 wt%, 99.6 wt%, 99.7 wt%, 99.8 wt%, 99.9 wt% or 99.99 wt%, much more preferably. within a range of 99.8 to 99.95% by weight.

Mixture (M-Ia) preferably comprises less than 1 wt% of other organic or inorganic compounds, more preferably less than 0.5 wt%, in particular less than 0.25 wt%.

Mixture (M-Ib) comprises less than 95% by weight of water. Preferably mixture (M-Ib) comprises 80 to 95 wt% water, in particular 82 to 92 wt% water, more preferably 85 to 90 wt% water. Mixture (M-Ib) further comprises less than 25 wt% of other organic or inorganic compounds, preferably 1 to 20 wt%, in particular 2.5 to 15 wt%, more preferably 5 to 10 wt%.

Therefore, the present invention also provides a process as described above, wherein the mixture (MI) or mixture (M ") or mixture (M") combined with mixture (MI) is further separated into mixture (M-Ia) comprising at least 90% by weight of water and mixture (M-Ib) comprising less than 95% by weight of water by reverse osmosis.

According to the present invention, the process described above may also comprise step (III) and additionally reverse osmosis separation.

Therefore, the present invention also provides a process as described above, wherein mixture (MI) is further separated into mixture (M-Ia) comprising at least 90% by weight of water and mixture (M-Ib) comprising less than 95% by weight of water by reverse osmosis, and the process further comprises the step of

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step.

Mixture (I-b) preferably comprises less than 5% by weight of organic compounds such as monopropylene glycol, dipropylene glycol, methoxy propanols, or hydroxy acetone.

Therefore, according to another embodiment of the present invention, this mixture (M-Ib) may be combined with mixture (M-II) prior to step (III), thus preferably resulting in an improved yield of propylene glycol.

Therefore, the present invention also provides a process as described above wherein the mixture (M-Ib) and mixture (M-II) are combined prior to step (III).

In accordance with the present invention, in step (I), the mixture is evaporated in 2 to 6 stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns, in particular 3 to 5 stages of evaporation. and / or distillation, preferably 3 or 4 stages of evaporation and / or distillation.

Therefore, the present invention also provides a process as described above, wherein in step (I) three stages of evaporation (E1) to (E3) or three stages of distillation (D1) to (D3) are performed.

Preferably the three stages of evaporation are performed at decreasing operating pressures.

Preferably the three stages of evaporation are performed at decreasing operating pressures in the range 150 to 550 kPa at a temperature of 111 to 156 ° C, 130 to 500 kPa at a temperature of 107 to 152 ° C, 70 to 400 kPa at a temperature from 90 to 144 ° C.

Therefore, the present invention also provides a process as described above, wherein the three stages of evaporation according to step (I) are performed at decreasing operating pressures in the ranges.

(El) 150 to 550 kPa at a temperature of 111 to 155 ° C,

(E2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(E3) 70 to 400 kPa at a temperature of 90 to 144 ° C.

The present invention also provides a process as described above, wherein the three distillation stages according to step (I) are performed at decreasing operating pressures in the ranges of

(Dl) 150 to 550 kPa at a temperature of 111 to 155 ° C,

(D2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(D3) 70 to 400 kPa at a temperature of 90 to 144 ° C.

In accordance with the present invention, mixture (M) comprises at least one propylene glycol. Preferably, mixture (M) comprises at least one propylene glycol in an amount of: less than 30 wt%, for example 0.01 to 25 wt%, preferably 0.1 to 20 wt%, more preferably 0, 5 to 15 wt%, in particular 1.0 to 10 wt%, most preferably 1.5 to 5 wt%.

Therefore, the present invention also provides a process as described above wherein the mixture (M) comprises 0.01 to 25 wt% propylene glycol.

For example, mixture (M) may further comprise hydroxy acetone in an amount of about 0.2 wt% and dipropylene glycol in an amount of about 0.4 wt%.

Suitable mixtures may for example be obtained as by-products of industrial processes, for example in a propene epoxidation. Preferably, mixture (M) is obtained as a byproduct in a propene epoxidation process. In the system of the present invention it is also possible for any mixture obtained as a byproduct in a propene epoxidation process to be further treated prior to being introduced into step (I) of the process according to the present invention.

Therefore, the present invention also provides a process as described above wherein the mixture (M) is obtained as a byproduct in a propene epoxidation process.

Preferably, propene epoxidation is performed using a hydroperoxide in the presence of a catalyst. According to another embodiment of the present invention, mixture (M) may be obtained as a byproduct in a propene epoxidation process. Preferably, the propene epoxidation process comprises a stage (a) of

(a) reacting propylene with a hydroperoxide in the presence of at least one solvent and at least one catalyst to obtain a mixture (M-a) comprising propylene oxide.

Therefore, the present invention also provides a process as described above, wherein the mixture (M) is obtained as a byproduct in a propylene epoxidation process comprising the stage of

(a) reacting propylene with a hydroperoxide in the presence of at least one solvent and at least one catalyst to obtain a mixture (M-a) comprising propylene oxide.

In the context of the present invention the term "hydroperoxide" refers to a compound of formula ROOH. Details relating to the preparation of hydroperoxides and related to hydroperoxides which may be used, inter alia, in the method of the present invention can be found in DE-A-198.35.907, the content of which is incorporated in the context of the present invention by reference. Examples of hydroperoxides which may be used for the purposes of the present invention are, inter alia, tert-butyl hydroperoxide, ethyl benzene hydroperoxide, tert-amyl hydroperoxide, cumene hydroperoxide, cyclohexyl hydroperoxide, methyl hydroperoxide. cyclohexyl, tetrahydro-naphthalene hydroperoxide, isobutyl benzene hydroperoxide, ethyl naphthalene hydroperoxide, peracids such as peracetic acid and hydrogen peroxide. Mixtures of two or more hydroperoxides may also be used in accordance with the present invention. Preference is given to the use of hydrogen peroxide as hydroperoxides in the method of the present invention, and further preference is given to the use of an aqueous hydrogen peroxide solution. More preferably, the aqueous hydrogen peroxide solution comprises hydrogen peroxide in a concentration within the range from 1 to 90, more preferably from 10 to 70 and especially preferably from 30 to 50% by weight, based on the total weight of the solution. It is also possible to use a mixture of two or more different hydroperoxides.

Preferably, hydrogen peroxide is used as hydroperoxide.

Therefore, the present invention also provides a process as described above, wherein in stage (a) the hydroperoxide is hydrogen peroxide.

According to stage (a), propylene is reacted with a hydroperoxide to obtain a mixture (M-a) comprising propylene oxide.

According to process step (a), propylene is reacted with a hydroperoxide in the presence of a solvent. In accordance with the present invention, all suitable solvents known to the person skilled in the art may be used. A suitable solvent is for example methanol.

Therefore, the present invention also provides a process as described above, wherein stage (a) the solvent is methanol.

The reaction according to stage (a) may be performed in one or more stages. It is also possible to separate one or more components of the reaction mixture between the reaction stages.

Consequently, it is possible to perform the reaction stages in batch mode or semi-continuous mode or continuous mode and independently of it, the other reaction stage in batch mode or semi-continuous mode or continuous mode.

The epoxidation reaction in stages (a) is preferably performed in the presence of at least one zeolite catalyst. Therefore, the present invention also provides a process as described above, wherein in stage (a) the catalyst is at least one titanium zeolite catalyst.

Preferably, at stage (a) at least one titanium zeolite catalyst is used as a catalyst and the solvent is methanol.

Therefore, the present invention also provides a process as described above, wherein in stage (a) catalyst is at least one titanium zeolite catalyst and the solvent is methanol.

Zeolites are, as is known, crystalline aluminosilicates having ordered cage and channel structures and containing micropores which are preferably smaller than about 0.9 nm. The network of such zeolites is composed of SiO4 and AlO4 tetrahedra which are joined via shared oxygen combs. An overview of known structures can be found, for example, in W.M. Meier, D.H. Olson and Ch. Baerlocher, "Atlas of Zeolite Structure Types", Elsevier, 5th edition, Amsterdam 2001.

Zeolites in which aluminum is not present and in which part of Si (IV) in the silicate reticulum is replaced by titanium as Ti (IV) are also known. These titanium zeolites, in particular those having an MFI type crystalline structure, and possible modes of their preparation are described, for example, in EP 0.311983 A2 or EP 0.405 978 A1. Apart from silicon and titanium, such materials they may further comprise additional elements such as aluminum, zirconium, tin, iron, cobalt, nickel, gallium, germanium, boron or small amounts of fluorine. In zeolite catalysts which have preferably been regenerated by the process of the invention, part or all of the zeolite titanium may have been replaced by vanadium, zirconium, chromium or niobium or a mixture of two or more thereof. The molar ratio of titanium and / or vanadium, zirconium, chromium or niobium to the sum of silicon and titanium and / or vanadium and / or zirconium and / or chromium and / or niobium is generally within the range 0.01: 1 to 0.1: 1. Titanium zeolites, in particular those having an MFI type crystalline structure, and possible modes of their preparation are described, for example, in WO 98/55228, EP 0.311983 A2, EP 0.405.978 A1, EP 0.200.260 A2 .

It is known that titanium zeolites having the MFI structure can be identified via a particular X-ray diffraction pattern and also via an infrared (IR) lattice vibration band at about 960 cm -1 and thus differ from each other. alkali metal titanates or crystalline and amorphous T1O2 phases.

Specific mention may be made of zeolites containing titanium, germanium, tellurium, vanadium, chromium, niobium, zirconium having a pentasil-zeolite structure, in particular the types which may be crystallographically X-rayed with structures ABW, ACO, ΑΕΙ, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATT, ATV, AWO, AWW, BCT, ΒΕΑ, BEC, BIK, BOG, BPH, BRE, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GIU, GON, GOO, HEU, IFR, ISV, ITE, ITH, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LOS, LOV, LTA, LTL, LTN, SEA, MAZ, MEI, HONEY, MEP, MER, MMFI, MFS, MON, MOR, MSO, MTF, MTN, MTT, MTW, MWW, NAB, NAT, NEES, NON, NPO, OBW, OFF, OSI, OSO, PAIR, DICK, PHI, PON, RHO, RON, RRO, RSN, RTE, RUT, RWR, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SFO, SGT, SOD, SSY, STF, STI, STT, TER, THO, TS TSC, UEI, UFI, UOZ, USI, UTL, VET, VFI, NIV, VSV, WEI, WEN, YUG and ZON, as well as mixed structures of two or more of the above mentioned structures. In addition, titanium containing zeolites having the structure ITQ-4, SSZ-24, TTM-1, UTD-1, CIT-I or CIT-5 are also conceivable for use in the process of the invention. Additionally titanium-containing zeolites which may be mentioned are those having the structure ZSM-48 or ZSM-12.

For the purposes of the present invention, preference is given to the use of Ti zeolites having an MFI structure, a MEL structure, a mixed MFI / MEL structure or a MWW structure. Another preference is given to Ti-containing zeolite catalysts which are generally referred to as "TS-1", "TS-2", TS-3 ", and also Ti zeolites having a beta-zeolite isomorphic frame structure. is given to the use of TS-I and Ti-MWW structure zeolite catalysts.

titanium zeolite catalysts and even more preferably catalysts having TS1 or MWW structure can be employed as powder, as granules, as microspheres, as molded bodies having, for example, the form of pellets, cylinders, wheels, stars, spheres and and so forth, or as extrudates such as extrudates having, for example, a length of about 1 to 10, more preferably 1 to 7 and even more preferably 1 to 5 mm, and a diameter of about 0.1 to 5, more preferably from 0.2 to 4 and especially preferably from 0.5 to 2 mm. In order to increase the bulk density of the extrudates, it is preferred to cut the extrudates with a stream consisting essentially of an inert gas.

For each of these forming methods, at least one additional binder and / or at least one filler and / or at least one pore forming agent may be used. Prior to the use of the catalyst in the epoxidation reaction of the present invention, it is suitably possible to pretreat the catalyst. In the case of catalyst if used as a supported catalyst, a support which is inert, i.e. unreacted with hydrogen peroxide, olefin, and olefin oxide may preferably be used. More preferably, a Ti-TS 1 or Ti-MWW catalyst is employed which is first produced by the formation of microspheres, for example microspheres formed according to EP 0.200.260 A2, and then transformation of said microspheres to obtain molded, preferably extruded bodies. as described above.

Therefore, the reactions in stages (a) are preferably performed in suspension or fixed bed mode, most preferably in fixed bed mode.

It is possible to perform one of the reaction stages in an isothermal or adiabatic reaction and the other reaction stage, independently of it, in an isothermal or adiabatic reactor. The term "reactor" as used herein refers to a single reactor, a cascade of at least two serially connected reactors, at least two reactors that are operated in parallel, or a multitude of reactors in which at least two reactors are serially coupled. and in which at least two reactors are operated in parallel.

Each of the reactors described above, especially reactors according to the preferred embodiment, may be operated in down flow mode or in up flow mode.

In case reactors are operated in downflow mode, the use of fixed bed reactors which are preferably tubular, multi-tube or multi-plate reactors, much more preferably equipped with at least one cooling jacket, is preferred. In this case, the epoxidation reaction is performed at a temperature of 30 to 80 ° C, and the temperature profile in the reactors is kept at a level such that the temperature of the cooling medium in the cooling jackets is at least about 40 °. C and the maximum catalyst bed temperature is about 60 ° C. In case of reactor down mode operation, it is possible to choose reaction conditions such as temperature, pressure, feed rate and relative quantities of starting materials such that the reaction is carried out in a single phase, more preferably in one phase. liquid or in a multiphase system comprising, for example, 2 or 3 phases. As for the downflow mode of operation, it is especially preferred to conduct the epoxidation reaction in a multiphase reaction mixture comprising a methanol-containing hydrogen peroxide rich aqueous liquid phase and an olefin rich organic liquid phase, preferably a rich phase. in propylene.

In case reactors are operated in upstream mode, it is preferred to use fixed bed reactors. Further preferred is the use of at least two fixed bed reactors. According to yet another preferred embodiment, the at least two reactors used are serially connected or operated in parallel, more preferably operated in parallel. Generally, it is necessary to equip at least one of the reactors used with a cooling medium such as a cooling jacket. Especially preferably, at least two reactors are employed which are connected in parallel and can be operated alternately. In case the reactors are operated in upstream mode, the two or more parallel connected reactors are particularly preferably tubular reactors, multi-tube reactors or multi-plate reactors, more preferably multi-tube reactors and especially preferably multi-tube reactors. shell-and-tube comprising a multitude of tubes such as from about 1 to 20,000, preferably from 10 to 10,000, more preferably from 100 to 9,000, more preferably from 1,000 to 8,000 and particularly preferably from 3,000 to 7,000, tubes. To regenerate the catalyst used for the epoxidation reaction, it is possible for at least one of the parallel connected reactors to be taken out of operation for the respective reaction stage and the catalyst present in this reactor to be regenerated, with at least one reactor always available for reaction of starting material or starting materials at each stage during the course of the continuous process.

As a cooling medium used to cool the reaction medium in aforementioned reactors equipped with cooling jackets, there are no specific restrictions. Especially preferred are oils, alcohols, liquid salts or water, such as river water, brackish water and / or sea water, which in each case may, for example, preferably be taken from a river and / or a pond and / or a sea near the chemical plant in which the inventive reactor and the inventive process are used and, after any necessary suitable removal of suspended material by filtration and / or sedimentation, be used directly without further treatment to cool the reactors. Secondary cooling water that is preferably conveyed around a closed loop is particularly useful for cooling purposes. This secondary cooling water is generally essentially deionized or demineralized water in which at least one antifouling agent has preferably been added. More preferably, this secondary cooling water circulates between the reactor of the invention, for example a cooling tower. Preference is also given to secondary cooling water being, for example, counter-cooled in at least one countercurrent heat exchanger by, for example, river water, brackish water and / or sea water.

According to a preferred embodiment, hydrogen peroxide is used in the process according to the invention in the form of an aqueous solution having a hydrogen peroxide content of generally from 1 to 90% by weight, preferably from 10 to 70% by weight. weight, more preferably from 10 to 60% by weight. A solution having at least 20 to less than 50 wt% hydrogen peroxide is particularly preferred.

According to another embodiment of the present invention, a crude aqueous hydrogen peroxide solution may be employed, as a crude aqueous hydrogen peroxide solution, a solution which is obtained by extracting a mixture with essentially pure water in

which mixture results from a process known as the process of

th

anthraquinone (see, e.g., Ullmann's Encyclpedia of Industrial Chemistry, 5 edition, volume 3 (1989) pages 447-457). In this process, the hydrogen peroxide formed is usually separated by extraction from the working solution. This extraction can be performed with essentially pure water, and crude aqueous hydrogen peroxide is obtained. According to one embodiment of the present invention, this crude solution may be employed without further purification. The production of such a crude solution is described, for example, in European Patent Application EP 1,122,249 A1. The term "essentially pure water" refers to paragraph 10, page 3 of EP 1,122,249 A1 which is incorporated as reference.

In order to prepare hydrogen peroxide which is preferably used, it is possible to employ, for example, the anthraquinone process whereby virtually all worldwide peroxide production is produced.

of hydrogen. An overview of the anthraquinone process is given in

th

Ullmann's Encyclopedia of Industrial Chemistry, 5 edition, volume 13, pages 447 to 456.

It is also conceivable to obtain hydrogen peroxide by converting sulfuric acid to peroxodisulfuric acid by anodic oxidation with simultaneous release of hydrogen into the cathode. Hydrolysis of peroxodisulfuric acid then leads via peroxomonosulfuric acid to hydrogen peroxide and sulfuric acid which is thus obtained back.

Of course, the preparation of hydrogen peroxide from the elements is also possible.

Before hydrogen peroxide is used in the process of the invention, it is possible to release, for example, a commercially available hydrogen peroxide solution from unwanted ions. Conceivable methods are, inter alia, those described, for example, in US 5,932,187, DE 42,22,109 A1 or US 5,397,475. It is also possible to remove at least one salt present in the hydrogen peroxide solution by ion exchange in an apparatus containing at least one non-acid ion exchange bed having a cross-sectional area F and a height H which are such that the height H of the ion exchange bed is less than or equal to .2,5 · F1 / 2, in particular less than or equal to 1,5 · F1 / 2. For the purposes of the present invention, it is in principle possible to use all non-acid ion exchanger beds comprising cation exchangers and / or anion exchangers. It is also possible that cation and anion exchangers are used as mixed beds within an ion exchange bed. In a preferred embodiment of the present invention, only one type of non-acid ion exchangers is used. Additional preference is given to the basic ion exchanger, particularly preferably to a basic anion exchanger and more particularly preferably to the weakly basic anion exchanger.

The overall process selectivity according to stage (a) with respect to hydrogen peroxide is preferably within the range of 78 to 99%, more preferably within the range of 88 to 97% and particularly preferably within the range of 90 to 96%. .

The total conversion to hydrogen peroxide is preferably at least 99.5%, more preferably at least 99.6%, much more preferably at least 99.7% and particularly preferably at least 99.8%.

The mixture (Ma) obtained in stage (a) preferably has a solvent, preferably a methanol content of from 50 to 90% by weight, more preferably from 60 to 85% by weight and especially preferably from 70 to 80% by weight, based on at total weight the reaction mixture. Additionally it may contain water, propylene oxide, or propene.

The mixture (M-a) obtained from stage (a) must be adequately treated to obtain mixture (M). Mixture (M) according to the present invention is essentially free of an organic solvent such as methanol and propylene or propylene oxide. Mixture (M-a) may be suitably treated to separate any organic solvent, propylene or propylene oxide. Suitable methods for solvent, propylene or propylene oxide separation are known to the person skilled in the art.

For example it is possible to separate unreacted propylene from the mixture (M-a) by distillation at one stage (b).

It is also possible to separate propylene oxide from the mixture by distillation at stage (c), preferably after separation of unreacted propylene.

Preferably, after these two separations according to stages (b) and (c), the mixture comprises water and the solvent, preferably methanol.

The mixture obtained may additionally contain certain by-products resulting from one or more stages of the total epoxidation process having boiling points lower than that of propylene oxide. Examples of such by-products are aldehydes such as, for example, acetaldehyde and / or formaldehyde. These by-products may be contained in an amount of up to 0.3% by weight, preferably up to 0.20% by weight and especially preferably up to 0.15% by weight, based on the total weight of the mixture and referring to the sum of their respective weights. low boiling compounds.

The mixture comprising water and a solvent, preferably methanol, may be further separated in another distillation separation process at a stage (d) wherein a mixture (M-di) comprising at least 85% by weight of methanol and up to 10% by weight of water, and a second mixture (M-dii) comprising at least 90% by weight of water is obtained. Stage distillation (d) can be performed on one, two, three or more distillation columns.

The mixture (M-dii) comprises at least 90 wt% water, more preferably at least 95 wt% water and especially preferably at least 97 wt% water. Preferably (M-dii) is essentially free of methanol, i.e. has a methanol content of less than 5 ppm, more preferably less than 1 ppm. In addition to water, (M-dii) may comprise certain by-products resulting from one or more stages of the total epoxidation process. Examples of such byproducts are glycol compounds such as propylene glycols. These by-products may be contained in (M-dii) in an amount of up to 4 wt%, preferably up to 3 wt%.

According to the process of the present invention, it is possible that the mixture introduced in stage (d) comprises byproducts produced in at least one stage of the total epoxidation process such as glycol ethers as methoxy propanols.

Stages (b), (c) and (d) may be applied to the mixture (M-a) separately or in combination. Preferably, mixture (M-a) is first subjected to stage (b), the resulting mixture is subjected to stage (c) and the resulting mixture of stage (c) is subjected to stage (d). Further, it is possible to treat the resulting mixtures between stages (a), (b), (c) and (d), for example by heating or adding or separating them into any other components.

Preferably, a water vapor which has been treated according to stage (a), (b), (c), and (d) is used as a mixture (M) for the process according to the present invention.

In the following, further preferred embodiments of the present invention are described.

According to a preferred embodiment, the present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixing

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than that 30% by weight of water;

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step.

According to a further preferred embodiment, the present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water,

wherein the mixture (M-I) is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis. According to a still further preferred embodiment, the present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixing

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than that 30% by weight of water;

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step,

wherein the mixture (M-I) is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis.

According to a still further preferred embodiment, the present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixing

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water,

wherein the mixture (M) is obtained as a byproduct in a propylene epoxidation process comprising the step of

(a) reacting propylene with a hydroperoxide in the presence of at least one solvent and at least one catalyst to obtain a mixture (M-a) comprising propylene oxide.

According to a still further preferred embodiment, the present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising ».

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water,

where in stage (I) three stages of evaporation (El) through (E3) are performed at decreasing operating pressures in the ranges of

(El) 150 to 550 kPa at a temperature of 111 to 155 ° C,

(E2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(E3) 70 to 400 kPa at a temperature of 90 to 144 ° C.

According to a still further preferred embodiment, the present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one further distillation step, obtaining a mixture (M-I) comprising

at least 70 wt% water and a mixture (M-II) comprising less than 30 wt% water;

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step;

where in stage (I) three stages of evaporation (El) through (E3) are performed at decreasing operating pressures in the ranges of

(El) 150 to 550 kPa at a temperature of 111 to 155 ° C,

(E2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(E3) 70 to 400 kPa at a temperature of 90 to 144 ° C.

According to a still further preferred embodiment, the present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of the

evaporators and / or distillation columns obtaining mixture (M ') and mixture

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (M-I) comprising at least 70% by weight of water and a mixture (M-II) comprising

less than 30% by weight of water;

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step,

wherein the mixture (M-I) is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis, and

where in stage (I) three stages of evaporation (El) through (E3) are performed at decreasing operating pressures in the ranges of

(El) 150 to 550 kPa at a temperature of 111 to 155 ° C, (E2) 130 to 500 kPa at a temperature of 107 to 152 ° C, (E3) 70 to 400 kPa at a temperature of 90 to 144 ° C . According to a still further preferred embodiment, the present invention also relates to a process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporating a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns to obtain mixture (M ') and mixture (M ");

(II) separating a mixture (M ') obtained from (I) into at least one further distillation step, obtaining a mixture (Ivl-I) comprising at least 70% by weight of water and a mixture (M-II) comprising less than 30% by weight of water;

wherein the mixture (M-I) is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt% water by reverse osmosis;

wherein the mixture (M) is obtained as a byproduct in a propylene epoxidation process comprising the step of

(a) reacting propylene with a hydroperoxide in the presence of at least one solvent and at least one catalyst to obtain a mixture (M-a) comprising propylene oxide; and

where in stage (I) three stages of evaporation (El) through (E3) are performed at decreasing operating pressures in the ranges of

(El) 150 to 550 kPa at a temperature of 111 to 155 ° C,

(E2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(E3) 70 to 400 kPa at a temperature of 90 to 144 ° C.

Hereinafter, preferred processes of the present invention are listed resulting from the following embodiments 1 to 13 including combinations of these embodiments as explicitly given.

A process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, said process comprising

(I) evaporate a mixture at at least two stages of evaporation and / or distillation at decreasing operating pressures of evaporators and / or distillation columns obtaining mixture (M ') and mixing

(M ");

(II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water.

2. The process of embodiment 1 wherein the mixture (M ") is further separated into mixture (M-Ia) comprising at least 90 wt% water and mixture (M-Ib) comprising less than 95 wt%. of water through reverse osmosis.

3. The process of embodiment 1 or 2, wherein the process further comprises the step of

(III) separating at least one propylene glycol from the mixture (M-II) in at least one other distillation step.

The process of any one of embodiments 1 to 3, wherein mixture (MI) is further separated into mixture (M-Ia) comprising at least 90% by weight of water and mixture (M-Ib) comprising less than 95% by weight of water by reverse osmosis.

The process of any one of embodiments 1 to 4, wherein the mixture (M ") and mixture (MI) are combined and further separated into mixture (M-Ia) comprising at least 90% by weight of water and mixture ( M-Ib) comprising less than 95% by weight of water by reverse osmosis.

The process of any of embodiments 1 to 5, wherein the mixture (M-Ib) and mixture (M-II) are combined prior to step (III).

The process of any one of embodiments 1 to 6, wherein in step (I) three stages of evaporation (E1) to (E3) or three stages of distillation (D1) to (D3) are performed.

8. The process of embodiment 7, wherein the three stages of evaporation according to step (I) are performed at decreasing operating pressures in the ranges of

(El) 150 to 550 kPa at a temperature of Illa 155 ° C,

(E2) 130 to 500 kPa at a temperature of 107 to 152 ° C,

(E3) 70 to 400 kPa at a temperature of 90 to 144 ° C.

The process of any one of embodiments 1 to 8, wherein mixture (M) comprises 0.01 to 25% by weight propylene glycol.

The process of any one of embodiments 1 to 9, wherein the mixture (M) is obtained as a byproduct in a propene epoxidation process.

The process of any one of embodiments 1 to 10, wherein the mixture (M) is obtained as a byproduct in a propylene epoxidation process comprising the stage of

(a) reacting propylene with a hydroperoxide in the presence of at least one solvent and at least one catalyst to obtain a mixture (M-a) comprising propylene oxide.

12. The process of embodiment 11, wherein in stage (a) the hydroperoxide is hydrogen peroxide.

13. The process of embodiment 11 or 12, wherein in stage (a) the catalyst is at least one titanium zeolite catalyst and the solvent

is methanol.

The invention is illustrated with the following examples.

Examples

Example 1: Distillation combined with reverse osmosis

From a storage tank, 1,000 kg / hr of a waste stream from a process for preparing propylene oxide of the following composition:

water 97.45% by weight,

methoxypropanol (MOP) 0.05% by weight,

hydroxy acetone (HA) 0.09% by weight,

monopropylene glycol (MPG) 2.04 wt%,

dipropylene glycol monomethyl ether (DPGME) 0.32 wt%, high boiling compounds (HBC) 0.05 wt%,

They are subjected to distillation in four successive columns which are thermally coupled. The streams obtained at the top of the distillation columns with a water content of about 99.6 to 99.7% by weight are mixed together, cooled to 40 ° C and subjected to reverse osmosis (polyamide membrane, spiral modules, with a membrane area of 96 m2 operating at a pressure of 9,000 kPa, T = 40 ° C). The retentate obtained after reverse osmosis and the bottom product of the last distillation column are combined and subjected to further treatment.

The columns are coupled in a way that the first column is heated with water vapor and each of the following columns is heated with the vapors of the previous column.

The columns are operated at the following pressures and reflux ratios (RR):

Column 1 (diameter 0.3 m, height 8 m, 7 trays): SlOkPa RR = 0.13 Column 2 (diameter 0.3 m, height 8 m, 7 trays): 200 kPa RR = O, 12 Column 3 (diameter 0.3 m, height 8 m, 7 trays): IlOkPa RR = 0.15 Column 4 (diameter 0.6 m, height 8 m, 8 trays): 9.5 kPa RR = 0.25

For current above 1 t / h, water vapor of 175 kW was required for distillation.

The currents obtained are listed in table 1.

Table 1

water MOP's HA MPG DPGME HBC Mass flow [kg / h] feed [% w] 97.45 0.05 0.09 2.04 0.32 0.05 1000 bottom Cl [% w] 96.78 0.04 0.10 j 2.65 0.39 0.04 767 top Cl [% pl 99.64 0.08 0.06 0.03 0.08 0.09 0.03 233 bottom C2 [% pl 95.35 0.03 0 .11 3.91 0.53 0.06 516 top C2 [% w] 99.74 0.06 0.07 0.03 0.10 0.00 250 bottom C3 [% p 91.19 0.02 0, 14 7.62 0.91 0.12 264 top C3 [% w] 99.72 0.04 0.08 0.03 0.13 0.00 252 bottom C4 [% pl 8.51 0.00 0.13 82.64 7.33 1.30 24 top C4 [% w] 99.57 0.02 0.14 0.01 0.26 0.00 227 RO feed [% w] 99.67 0.05 0.09 0.03 0.14 0.02 976 retained RO [% w] 91.24 1.38 1.94 0.73 4.07 0.64 32 permeate RO [% w] 99.96 0.00 0.03 0.00 0.01 0.00 944

Example 2 (Comparative): Distillation without Reverse Osmosis

From a storage tank, 1,000 kg / hr of a waste stream from a propylene oxide preparation process of a composition according to example 1 is distilled into four columns which are thermally coupled to obtain top streams of the four columns with a water content of about 99,9% by weight.

The columns are coupled in a way that the first column is heated with water vapor and each of the following columns is heated with the vapors of the previous column.

The columns are operated at the following pressures and ratios of

reflux (RR):

Column 1 (diameter 0.3 m, 25 m height): 300 kPa RR = 0.7 Column 2 (diameter 0.3 m, 25 m height): 220 kPa RR = 0.75

Column 3 (diameter 0,3 m, height 25 m): 150 kPa RR = 0.8

Column 4 (diameter 0.6 m, height 18 m): 9.0 kPa RR = 0.6

Columns 1 to 3 use 16 m of 250 m2 / m3 sheet metal, column 4 uses 10 m of 500 m2 / m3 mesh filling.

For current above 1 t / h, steam with 256 kW water was required for distillation.

The currents obtained are listed in table 1.

The energy costs (water vapor and electricity) for the process according to the invention are about 20% lower combined with an investment that is about 10% lower than for the state of the art process.

The currents obtained are listed in table 2.

Table 2

<table> table see original document page 48 </column> </row> <table>

Claims (12)

Process for separating at least one propylene glycol from a mixture (M) comprising water and said propylene glycol, comprising (I) evaporating a mixture at at least two stages of evaporation and / or distillation at pressures. decreasing operational levels of evaporators and / or distillation columns obtaining mixing. (M ') and mixture (M "), wherein mixture (M") is further separated into mixture (M-Ia) comprising at least 90% by weight of water and mixture (M-Ib) comprising less than 95%. % by weight of water by reverse osmosis; (II) separating a mixture (M ') obtained from (I) into at least one other distillation step, obtaining a mixture (MI) comprising at least 70% by weight of water and a mixture (M-II) comprising less than than 30% by weight of water. Process according to Claim 1, characterized in that the process further comprises step (III) separating at least one propylene glycol from the mixture (M-II) into at least one other distillation step. Process according to either claim 1 or claim 2, characterized in that the mixture (MI) is further separated into mixture (M-Ia) comprising at least 90% by weight of water and mixture (M-Ib). comprising less than 95% by weight of water by reverse osmosis. Process according to any one of claims 1 to 3, characterized in that the mixture (M ") and mixture (MI) are combined and further separated into mixture (M-Ia) comprising at least 90% by weight of water and mixture (M-Ib) comprising less than 95%) by weight of water by reverse osmosis. Process according to any one of Claims 1 to 4, characterized in that the mixture (M-Ib) and mixture (M-II) are combined prior to step (III). Process according to any one of claims -1 to 5, characterized in that in step (I) three stages of evaporation (E1) to (E3) or three stages of distillation (D1) to (D3) are carried out. . Process according to Claim 6, characterized in that the three stages of evaporation according to step (I) are carried out at decreasing operating pressures in the ranges from (El) 150 to 550 kPa at a temperature of 111 to 155 ° C, (E2) 130 to 500 kPa at a temperature of 107 to 152 ° C, (E3) 70 to 400 kPa at a temperature of 90 to 144 ° C. Process according to any one of claims 1 to 7, characterized in that the mixture (M) comprises 0.01 to 25% by weight propylene glycol. Process according to any one of Claims 1 to 8, characterized in that the mixture (M) is obtained as a by-product in a propene epoxidation process. A process according to any one of claims 1 to 9, characterized in that the mixture (M) is obtained as a by-product in a propylene epoxidation process comprising the stage of (a) reacting propylene with a hydroperoxy in the mixture. presence of at least one solvent and at least one catalyst to obtain a mixture (M-a) comprising propylene oxide. Process according to Claim 10, characterized in that in stage (a) the hydroperoxide is hydrogen peroxide. Process according to Claim 10 or 11, characterized in that in stage (a) the catalyst is at least one titanium zeolite catalyst and the solvent is methanol.