PL215801B1 - Method for preparing 1,2-propanediol in the hydrogenolysis reaction of glycerol - Google Patents

Description

The subject of the invention is a method for the production of 1,2-propanediol by hydrogenolysis of glycerol in the presence of the CuZAl2O3 catalyst

The increasing production of biofuel by transesterification of vegetable oils with methanol causes the formation of significant amounts of waste glycerol. About 110 kg of waste glycerol is produced per 1 ton of produced biofuel. In 2010, the production of biodiesel in the European Union was around 22 Mt, which is around 2.42 Mt of glycerol waste. The discharge of waste glycerol to wastewater requires purification of the transesterification catalyst (acid or base) and methanol, which increases the cost of biodiesel production. The use of glycerol for the production of 1,2-propanediol can reduce the costs of biofuel production. 1,2-propanediol is used as a cooling agent, deicer and a precursor in the synthesis of unsaturated polyester resins and pharmaceuticals. Due to its non-toxic properties, it is used in the cosmetic industry as a skin moisturizing ingredient and thinner, giving the cosmetic the desired emulsion consistency, and in the food industry as a preservative and emulsifier, and a component of dyes and flavors.

Currently, propylene is used for the production of 1,2-propanediol, obtained in the pyrolysis of hydrocarbons and as a result of catalytic fluid cracking (FCC) of low-octane gasolines. The production of 1,2-propanediol from petrochemical raw materials is based on the oxidation of propylene to propylene oxide and hydration of the formed oxide to 1,2-propanediol. Hydration of propylene oxide can take place without the use of a catalyst, but then the process is carried out at a high temperature of 200-220 ° C. Another way of hydration of propylene oxide is the use of catalysts: an ion exchange resin, sulfuric acid or a base. In this case, the process takes place at a lower temperature of 150-180 ° C. Obtaining 1,2-propanediol by hydrogenolysis of waste glycerol produced during biodiesel production is a new approach to the production of 1,2-propanediol.

The hydrogenolysis of glycerol to 1,2-propanediol takes place in two steps. In the first, glycerol is dehydrated to an intermediate product - acetol, in the second - acetol is hydrogenated to

1,2-propanediol:

ΟΗ _0Η ΟΗ ή ₂ ο

H ₂ CC—

Η

Glycerol

CH,

ΟΗ Ο

I II h ₂ c — c — ch ₃

Acetol

OH OH

H,

H ₂ C — C — CH ₃ H

1.2-Propanodlol

Hydrogenolysis of glycerol to 1,2-propanediol is carried out in the presence of heterogeneous catalysts - metals or their oxides, deposited on inorganic supports. Copper catalysts, e.g. Cu / Al2O3, CuCr2O4, CuO / ZnO, Cu / SiO2 have high activity and selectivity for this reaction. These catalysts show a poor ability to cleave the C-C bond and high efficiency of hydrogenation-dehydrogenation of the C-O bond. The hydrolysis of glycerol to 1,2-propanediol catalyzed by a copper catalyst is disclosed in WO 2009/145691. A commercial catalyst was used in the form of granules with the composition: 56 wt. CuO, 34 wt. % Al2O3 and 10 wt. MnO2. It was reduced with hydrogen for 3 h before the reaction. at 200 ° C. Hydrogenolysis was carried out in a reactor containing two or more stationary catalyst beds. Glycerol containing less than 3 wt. water. The hydrogenolysis parameters were as follows: temperature 210 ° C, 10 wt. catalyst, reaction time 16 h, hydrogen flow 11 g / h (pressure was kept constant at 44-49 atm). During the reaction, the water formed by dehydration was removed. The yield of 1,2-propanediol was 37.2% with conversion of glycerol to 66.4%. The disadvantage of this process is low efficiency

1,2-propanediol, which results from the use of a concentrated glycerol solution, i.e. with a water content of less than 3%. Performing hydrogenolysis at a high concentration of glycerol causes the formation of by-products due to the formation of polyglycerins and breaking the C-C bonds. In the described process, a relatively high catalyst concentration was used - 10% by weight. with respect to the glycerol introduced. Hydrogenolysis of glycerol to 1,2-propanediol in the presence of a copper catalyst is also shown in patent WO 2011/009936. The process was carried out continuously. The apparatus consisted of a heater, reactor and a waste water tank. The glycerol solution was fed by an HPLC pump, hydrogen was introduced into it, and the resulting mixture was passed through an electrically heated

PL 215 801 B1 coil. The mixture was then passed over a catalyst bed placed in a double mantle heating reactor. The resulting wastewater passed through the pressure-maintaining valve in the system and was then directed to a metal tank. The product was collected under a nitrogen atmosphere.

A solution with the composition of 9 wt.% Was subjected to hydrogenolysis. % glycerol, 1 wt. % water, 90 wt. methanol. 3 g of catalyst with the composition of: 64 wt. % copper oxide, 27 wt. alumina,

5% lanthanum oxide, 5 wt. copper. The catalyst was in the form of a 100-200 µm sieve fraction. Under the reaction conditions: temperature 282 ° C, hydrogen pressure 246.7 atm, the conversion of glycerol was 99.8% and the selectivity of conversion to 1,2-propanediol was 84.8%. The process was also carried out at a higher concentration of glycerol: 27 wt. % glycerol, 3 wt. % water and 70 wt. methanol in the presence of a catalyst consisting of copper oxide, alumina and manganese oxide. The process was carried out at the temperature of 297 ° C, under the hydrogen pressure of 246.7 atm, obtaining the conversion of glycerol 99.7%, selectivity of the conversion to 1,2-propanediol 89.0%. Both processes produced by-products: 1-propanol, 2-propanol, acetol, butanediol isomers and methyl propionate. The disadvantage of this process is the harsh reaction conditions - high temperature and very high pressure of hydrogen, which increase operating costs. In addition, glycerol was used significantly diluted with an organic solvent. The use of a highly diluted substrate significantly reduces the average yield per unit time and volume of the reactor, increases energy consumption and makes the process ineffective. Hydrogenolysis of glycerol to

1.2-propanediol was also carried out in the presence of copper catalysts: CuO / ZnO, Cu / SiO2, Cu / ZnO / Al2O3: Bienholz A .. Hofmann H., Claus P., Applied Catalysis, A: General 2011, 391, 153-157. The process was carried out in a 300 ml stainless steel reactor filled with Teflon. Commercial catalysts were used without pretreatment and obtained under laboratory conditions. 177 g of pure glycerol, 1.7 wt.%. catalyst and hydrogen at a pressure of 49.3 atm. The process was carried out in the liquid phase at a temperature of 200 ° C. Vigorous mixing at 1000 rpm was used. The reaction time was 1 hour. In the presence of a Cu / ZnO catalyst containing 60 wt. CuO and 40 wt.%. With ZnO, the glycerol conversion was 52.0% and the selectivity of the conversion to 1,2-propanediol was 98.0%. The use of the CU / SiO2 catalyst with the composition: 70% CuO and 30% SiO2 led to the conversion of glycerol 27.0% and selectivity of the conversion to 1,2-propanediol 97.0%. In the reaction catalyzed by Cu / ZnO / Al2O3 (36% CuO, 48% ZnO, 16% Al2O3) the glycerol conversion reached 17.0% and the selectivity of the conversion to 1,2-propanediol was 95.0%. By-products of hydrogenolysis were acetol and ethylene glycol.

This process was also carried out in the gas phase, in the presence of copper catalysts obtained by the ion exchange method. An aqueous 40% glycerol solution was fed to the heated evaporator at a rate of 5 ml / h. and 300 ml / min of hydrogen. The reaction was carried out at a temperature of 255 ° C, pressure in the range 0.1-1.0 MPa in a fixed bed reactor. The amount of the catalyst was 1 g. In the presence of CuZSiO2, the conversion of glycerol was 100.0% and the selectivity of the conversion to 1,2-propanediol was 87.0%. By-products during the reaction were acetol, ethylene glycol, 2-propanol, carbon dioxide and propane. This liquid-phase process achieved low conversion of glycerol. In the gas phase it was higher, but the selectivity of the conversion to

1.2- propanediol. In both cases a low concentration of glycerol in the aqueous solution was used. Introducing significant amounts of water with the substrate is disadvantageous because the presence of large amounts of water shifts the equilibrium of the reaction in the opposite direction. The separation of the product (1,2-propanediol) by distillation is more expensive in this case. The Polish patent application No. P 391674 discloses a method for the production of 1,2-propanediol by hydrogenolysis of glycerol, carried out in the presence of a Ru / C catalyst, obtained by the impregnation method, in which a Ru / C catalyst previously reduced with hydrogen is used. Prior to the reaction, the autoclave containing the aqueous glycerol solution and Ru / C catalyst is flushed with hydrogen.

Unexpectedly, it turned out that the use of a hydrogen-reduced copper catalyst CuZAl2O3 obtained by the co-precipitation method allows to obtain 1,2-propanediol with high selectivity and high conversion of glycerol at the same time. The process according to the invention is characterized in that a catalyst obtained by the co-precipitation method is used, which is reduced with hydrogen prior to the hydrogenolysis reaction. It is then introduced into a pressurized reactor containing an 80% solution of glycerol in water, and the air is then purged from the reactor by refilling it several times with hydrogen and reducing the pressure to atmospheric. Next, the hydrogenolysis reaction is carried out at the temperature of 200-220 ° C, under the pressure of 30 atm, for 8-24 hours with intensive stirring, and then the reactor is cooled down to room temperature. Preferably a catalyst

The mixture is prepared by using aqueous solutions of copper (II) nitrate and aluminum (III) nitrate in a 1: 1 molar ratio. Potassium carbonate is used to precipitate. The amount of catalyst, based on the introduced glycerol, is 4-8% by weight. The molar ratio of hydrogen to glycerol is 1.5: 1-3.0: 1. The mixing intensity expressed by the rotation of the magnetic stirrer is 100-500 rpm. The reduction of the catalyst prior to the hydrogenolysis reaction was performed at a temperature of 300 ° C for 8 hours.

It is also possible to use a catalyst obtained from other salts in the process according to the invention. It is known from the literature to prepare the catalyst by co-precipitation from solutions of copper chloride and aluminum chloride using sodium hydroxide to precipitate, and also from solutions of copper acetate and aluminum nitrate using such precipitating agents as sodium carbonate and ammonium hydroxide.

The method for producing 1,2-propanediol by glycerol hydrogenolysis is shown in the working examples.

P r z k ł a d I

The Cu / Al2O3 catalyst was prepared by the co-precipitation method. To the aqueous solution of nitrate ₃ copper (II), Cu (NO3) 2 * SH2O a concentration of 0.05 mol / dm ³ Aqueous solution of aluminum nitrate (III), ₃

Al (NO3) 3 * 9H2O with a concentration of 0.05 mol / dm ^{3, with} intense stirring, at room temperature. Then ₃ is added a precipitating agent, potassium carbonate K2CO3 at a concentration of 0.33 mol / dm ^3. The formed precipitate was left for 24 hours. After 24 hours the precipitate was filtered off, washed with deionized water until neutral pH, dried in an oven at 90 ° C for 8 hours. and calcination at 600 ° C for 8 hours. The formed catalyst was pre-reduced with hydrogen. The powder catalyst was placed in a sintered glass washer with a thermocouple. The washer and the thermocouple were placed in the oven. Hydrogen was passed through the catalyst bed at 300 ° C at a rate of 300 ml / min. The reduction time was 8 hours. The catalyst composition was determined by means of X-ray microanalysis: 68.9% Cu, 31.1% Al.

Hydrogenolysis reactions were carried out in a 140 ml autoclave made of stainless steel with a PTFE insert. The reactor was equipped with a pressure gauge, magnetic stirrer, electronic temperature controller, connected to a thermostatic electric heating mantle. 20 ml of an 80% by weight aqueous glycerol solution was introduced into the reactor. and 6 wt.%. catalyst with respect to glycerol. The reactor was flushed with hydrogen by filling to 20 atm five times and reducing the pressure to atmospheric. During the last filling, the pressure of hydrogen in the reactor was increased to 30 atm, magnetic stirring was turned on - stirring speed 300 rpm and the reaction mixture was heated at 220 ° C. The reaction temperature was measured with a thermocouple placed in an autoclave connected to a temperature controller. After 8 hours During hydrogenolysis, the reactor heating was turned off and cooled in ice water. This caused the pressure to drop to 20 atm. After carefully opening the pressure reduction valve on the autoclave, the amount of hydrogen and the gaseous products formed in the reaction were measured. The liquid post-reaction phase was separated from the catalyst by centrifugation and decantation. The content of 1,2-propanediol, unreacted glycerin and by-products: ethylene glycol and acetol were determined by means of gas chromatography using the method of an internal standard. Moreover, the content of: methanol, ethanol, 2- and 1-propanol, methane, ethane and propane was determined in the gas phase by the absolute calibration method.

In the process carried out in this way, the conversion of glycerol was 77.1%, and the selectivity of the conversion to 1,2-propanediol was 89.5%. The selectivity of the transformation to individual by-products contained in the liquid phase was: ethylene glycol 3.3%, acetol 1.9%, methanol 0.8%, ethanol 0.4%, 2-propanol 0.2%, 1-propanol 0, 5%. The selectivity to gas phase products was: methanol 0.5%, ethanol 0.4%, ethane 0.01%, propane 0.1%. Additionally, by gas chromatography coupled with a mass spectrometer, by-products were detected: glycerol aldehyde, lactic acid, propionaldehyde, glycolaldehyde.

P r z x l a d II

20 ml of an aqueous glycerol solution with a concentration of 80% and 8% by weight were introduced into the autoclave. of a Cu / Al2O3 catalyst prepared as presented in Example 1. The autoclave was flushed five times with hydrogen by successive filling to a pressure of 10 atm and slowly reducing the pressure to atmospheric. After filling the autoclave under the pressure of 20 atm and activating the magnetic stirrer, the heating was turned on. Hydrogenolysis was carried out at the temperature of 200 ° C, under the pressure of 30 atm, for 24 hours, with the mixing intensity of 500 rpm. After the reaction was completed and the reactor cooled down to room temperature, the pressure was reduced to 15 atm.

PL 215 801 B1

The glycerol conversion was 62.3%, and the selectivity of the conversion to 1,2-propanediol was 90.8%. The selectivity of the transformation to by-products contained in the liquid and gas phases was: ethylene glycol 1.6%, acetol 3.5%, methanol 0.5%, 2-propanol 0.6%, 1-propanol 0.5%, methane 0 , 3%. The process also produced 1,3-propanediol with a selectivity of 1.9%. The following by-products were detected by gas chromatography coupled to a mass spectrometer: glycerol aldehyde, lactic acid, propionaldehyde, glycolaldehyde.

P r x l a d III

20 ml of an aqueous glycerol solution with a concentration of 80% and 5% by weight was introduced into the autoclave. of Cu / Al2O3 catalyst prepared as described in Example 1. The autoclave was flushed five times with hydrogen by filling to a pressure of 20 atm and slowly reducing the pressure to atmospheric. After filling the autoclave under pressure of 30 atm and activating the magnetic stirrer, its heating was turned on. Hydrogenolysis was carried out at the temperature of 210 ° C for 24 hours, with a stirring intensity of 100 rpm. After said reaction time, the reactor was cooled to room temperature, which reduced the pressure to 25 atm.

The glycerol conversion reached 71.9% and the selectivity of the conversion to 1,2-propanediol reached 93.3%. The selectivity of the transformation to by-products was: 1,3-propanediol 1.3%, ethylene glycol 1.2%, acetol 1.1%, methanol 0.8%, ethanol 0.4%, 2-propanol 0.2%, 1-propanol 0.4%, methane 0.4%, ethane 0.1%. At the concentration level below 0.1%, the presence of: glycerol aldehyde, lactic acid, propionaldehyde, glycolaldehyde was found using the GC / MS method.

Claims (6)

1. The method for the production of 1,2-propanediol by hydrogenolysis of glycerol, carried out in the presence of the CuZAl2O3 catalyst, characterized by the use of a catalyst obtained by co-precipitation, which is reduced with hydrogen prior to the hydrogenolysis reaction, and then fed to a pressurized reactor containing 80% solution of glycerol in water, then the air is removed from the reactor by repeatedly filling it with hydrogen and reducing the pressure to atmospheric, and then the reaction is carried out at the temperature of 200: 220 ° C under the pressure of 30 atm, for 8:24 hours, with intensive stirring and the reactor is cooled to room temperature. 2. The method according to p. The method of claim 1, characterized in that the catalyst is prepared by using aqueous solutions of copper (II) nitrate and aluminum (III) nitrate in a molar ratio of 1: 1 and potassium carbonate as the precipitating agent. 3. The method according to p. The process of claim 1, wherein the amount of the catalyst with respect to the glycerol used is 41: 8 wt.%. 4. The method according to p. The process of claim 1, wherein the molar ratio of hydrogen to glycerol is 1.5: 1: 3.0: 1. 5. The method according to p. The method of claim 1, characterized in that the intensity of stirring expressed by the revolutions of the magnetic stirrer is 100-500 rpm. 6. The method according to p. The process of claim 1, wherein the reduction of the catalyst is carried out at a temperature of 300 ° C for 8 hours.