CS256540B1 - A method for producing a cycloaliphatic ketone mixture - Google Patents

Abstract

The purpose of the invention is a method for producing methylcyclohexanone, i.e. a mixture of cycloaliphatic ketones with a content of 70 to 85 wt. % ketone, based on methylcyclohexanone, by catalytic dehydrogenation of a mixture of methylcyclohexanol and dimethylcyclohexanol. The purpose is achieved by passing methylcyclohexanol vapors with a content of 5 to 20 wt. % dimethylcyclohexanol over two separate layers of copper catalysts at a space velocity of 0.5 to 1.5 h-1 and at a temperature of 260 to 320 6C.

Description

The present invention relates to a process for the preparation of a mixture of cycloaliphatic ketones having a content of 70-85% by weight, based on methylcyclohexanone, by catalytic dehydrogenation of a mixture of methylcyclohexanol and dimethylcylclohexanol. ° C,%

Technical methylcyclohexanone (hereinafter M * on) containing 70 to 70 wt. is a mixture of its three isomers, less cyclohexanone and increased cycloaliphatic ketones. It is used as a low volatile solvent especially in the paint industry and as a raw material for the production of organic peroxides. Its composition is influenced by the composition of the starting Icrezol obtained by distillation of both coal and brown coal tars. Recently, the content of sulfur compounds and xylenols has been increasing in technical cresol. While sulfur and other catalytic poisons are trapped during hydrogenation on a nickel catalyst, xylenols pass into technical methylcyclohexanol (hereinafter M * ol) as dimethylcyclohexanols (hereinafter di-M * ol) and impair the dehydrogenation process to technical M * on.

The actual dehydrogenation reaction of secondary cycloaliphatic alcohols to ketones is endothermic (δ.Η = 50 kJ / mol) and is associated with an increase in the volume of reaction products. Thus, it is favorably influenced by an increase in the reaction temperature and a decrease in pressure (or a decrease in the urinary pressure of the constituents), both in terms of equilibrium and in terms of reaction kinetics. In gaseous poles however under no conditions can be achieved .100 conversion no. ketone.

Catalysts for dehydrogenation. according to reaction temperature can be divided into three groups:

Nickel and cobalt catalysts operate at temperatures up to 200 ° C, but are unsuitable for the production of cycloaliphatic ketones because they are not sufficiently selective and catalyze the formation of cresols.

The exchanged catalysts have an optimum at temperatures of 260 to 320 ° C and lose activity at higher temperatures. Cycloaliphatic ketones with a content of up to 85% are produced industrially.

Catalysts no. Zn, Fe base, their alloys and some acids. The catalysts (MgO, ZnO) are used at temperatures of about 400 ° C and achieve conversions of R-ol no. R-ons above 90% · They are also the most used catalysts mainly for the production of cyclohexanone.

Recently, copper-based catalysts are gaining in importance for good selectivity, lower energy consumption (280 ° C) and thus safer conduction by means of heat exchangers that can be used up to 360 ° 0.

Prior art copper-based industrial technologies have preferred to recycle the dehydrogenation reaction products to remove hydrogen, then re-evaporate and blow the vapor through the catalyst when the cycle has been repeated on average three times for 72% M * on and 82% five times for M * on. . A reactor with a length of 2 to 2.5 m and a loading of about 100 kg of catalyst was used. The reason for this technology was to increase the chemical equilibrium of the reaction by removing hydrogen and difficult to clean tubular reactors long (4-5 m) while changing the catalyst. The disadvantage of the process is energetic, the difficulty of repeated evaporation of the mixture of phiol and lithium and the imperfect use of the initial part of the tubular reactom in the length of approx. 0.5 m, since the optimal reaction temperature of inlet vapors 280 to 320 ° C ! products.

Under these conditions, the ketone content increased after individual flow rates of 50, 65, 73, 79, 83% by weight.

According to the invention, the above mentioned disadvantages eliminate the process for the production of technical M * on (a mixture of cycloaliphatic ketones) with a content of 70 to 85% by weight. ketone, based on M * on, by gas-phase catalytic dehydrogenation on copper catalysts at a temperature of 260 to 320 ° C, such that M * ol vapors containing 5 to 20 wt. M * di-ol was passed over two separate catalyst layer at a space velocity of '0.5 to 1.5 hours ,.' ^1.

The advantage of the process according to the invention is, in particular, a lower energy consumption for the evaporation of the feedstock and for the heating of the reactors and an increase in the capacity of the plant per evaporator.

Serial connection of two tubular reactors of length 2 to

2.5 m, a ketone having a 73 wt. at a space velocity of 1.25 hours. at a space velocity of 0.7 h, the transfer reactor must be well insulated as well as the heat exchanger to preheat the vaporized M * ol vapor reaction products.

The process according to the invention demonstrates that shifting the chemical equilibrium of the reaction by removing hydrogen in the production of techn. % M * on to 85 wt. it has less influence on the course of the reaction than on the optimal one. temperature along the entire catalytic bed. The equilibrium constant of the reaction at 2.80 to 320 ° C is high even without hydrogen removal, since the conversion of methanol to 1.1'on OO / hr was achieved in the integral reactor in the laboratory. As a result, the resulting hydrogen has a low relative adsorption coefficient, so that it acts as an inert, diluting reaction product. Significant acceleration of the reaction by removing the resulting ketone is not possible in the gas phase as well as the separation of the starting materials and products by distillation due to small differences in the boiling points of the components. Connection of the third reactor in series to achieve a ketone content above 85 wt%. would be “possible”.

however, it is no longer economically advantageous.

Example 1

Technical i / ol containing 4% cyclohexanol, 12% di-M * ol (0.1% water, 0.5% ii-cyclohexane) and 63.4% fc / ol was fed to the evaporator at 240 lcg / h . After evaporation at 185 ° C, the feedstock vapors were preheated in a heat exchanger on the evaporator head to 240 ° C (12 kPa pressure) and passed through two tubular reactors connected in series. Each of the reactors is 2.1 m long, the shell is filled with a salt bath (mixture of ITalKL ·, NaNOp and KNO ^). The reactors are heated to 285 ° C using pressurized water from a gas furnace. The tubesheet of each reactor is filled with 100 kg of tableted catalyst which contains 50% CuO and 50% diatomaceous earth prior to hydrogen reduction. The transfer reactor is insulated with skelnoxx and asbestos insulation, the evaporator and the reactors by concrete insulation. The pressure at the transducer is 6 kPa. Reaction vapors warm 280 ° C are passed through the reactors to the evaporator head, where they preheat the incoming feedstock vapor, then to a tube heat exchanger where they partially condense and preheat the liquid feedstock before entering the evaporator and finally are condensed and cooled in a water cooler. temperature approx. 30 ° 0. The resulting reaction hydrogen is passed to the atmosphere via a barometric cap. The condensed dehydrogenation product contained 72.3% of f *,

0.3 water, 10% H-cyclohexene / M-cyclohexane and 0.8% cresol.

The rectified technical Mon '(fraction 155-173 ° C) contains 74.4% ketone based on H * on and 0.02 cresol.

The ketone content was determined by titration of hydrochloric acid by the reaction of Itilone with hydroxylamine hydrochloride, the cresol content by colorimetric reaction with aminoantipirine, and the fractions by weighing the rectified fraction to 110 ° C.

Example 2

The same raw material as in Example 1) was fed to the evaporator at a rate of 130 kg / hr. The evaporator head temperature was 235 ° C and 10 kPa pressure. The procedure was the same as in Example 1. The condensate was 02.1 $ H 2 -one, 0.3 $ water, 1.2 ‘4 of a mixture of U-cyclohexene and 14-cyclohexane and cresol.

The rectified technical M * he obtained contained 84.8 wt. ketone, based on M * on, and 0.01% cresol.

Example 3

Technical Ι / Ϊ * ol containing 2.5% cyclohexanol, 9% di-M ol, 0.1 ⁽ /> water, 0.4% M-cyclohexane and 88% M * ol) was fed into the evaporator in an amount of 180 kg / hr. The next procedure was the same as in Example 1., except that the catalyst contained 60% GUO on magnesium silicate carrier.

The rectified technical M * he contained 76 wt. ketone, based on 1'-one, 91 no cresol.

Claims (1)

Process for preparing a mixture of cycloaliphatic ketones having a content of 70 to 85% by weight. % ketone, based on methylcycloliexanone, by gas-phase catalytic dehydrogenation of a mixture of methylcyclohexanol and dimethylcyclohexanol on copper catalysts at a temperature of 260 to 320 ° C, characterized in that the methylcyclohexanol vapors containing 5 to 20 wt. dimetylcyklohexanolu'se passed over two separate catalyst layer at a space velocity of 0.5 to 1.5 hr. ^"1 · ·.