RU2029758C1 - Process for preparing methyl tert-butyl ether - Google Patents

Abstract

FIELD: organic chemistry. SUBSTANCE: methyl tert-butyl ether is prepared by contacting an isobutylene-containing C₄- fraction and methanol in a liquid phase at elevated temperature in the presence of a sulfocationite catalyst in H-form in two reaction zones at a total methanol to isobutylene molar ratio of 0.90-0.99:1 by feeding the starting 85-95% C₄ fraction into the first reaction zone and the remaining amount into the second zone at maintaining 20-40 C and subsequently separating the reaction mixture and recovering the desired product. EFFECT: lower power consumption at the stage of recovery of methanol from the spent C₄-fraction and greater efficiency of the catalyst. 1 tbl

Description

 The invention relates to methods for producing methyl tert-butyl ether (MTBE) by reacting methanol with isobutylene on a sulfocationite catalyst. It can be used in the refining and petrochemical industries to obtain high-octane additives to motor fuels.

A known method of producing MTBE by selective interaction of methanol with isobutylene contained in the butane-butylene fraction of catalytic cracking [1]. The process of ether synthesis is carried out in a distillation column in a reactive distillation mode. Sulfocationic catalyst is placed in the middle of the column using a special placement method, excluding its contact with the walls of the apparatus. Methanol is fed to the bed, the initial C ₄ fraction is placed under the catalyst bed. Plates located above and below the catalyst layer provide the allocation of an azeotropic mixture of methanol / C ₄ - (overhead) and a commercial product - MTBE- (VAT residue). This technology requires a special catalyst and device for its placement and is quite complex. The steam consumption in the production of MTBE from the butanbutylene fraction of catalytic cracking is 1.33 tons per 1 ton of ether, and the energy consumption is almost completely accounted for by the unit for washing the spent hydrocarbons and the separation of methanol from the aqueous solution.

Closest to the proposed invention in technical essence and the achieved results is a method for producing MTBE by direct-flowing a mixture of methanol and isobutylene-containing C ₄ fractions through a catalyst bed - macroporous sulfocationionite [2]. The process is conducted in the liquid phase at a temperature of 30-100 ^{° C} and a molar ratio of methanol: isobutylene equal to 1.2: 1, in two reaction zones which are maintained at different temperatures. The reaction mass leaving the reactor containing the spent C ₄ fraction, methanol and MTBE is sent to the first distillation column, where an azeotrope of hydrocarbons with methanol is distilled off at a pressure of 6 atm. Excess methanol is distilled off in a second column operating at a pressure of 1.3-30 atm, an azeotrope with MTBE, and returned to the MTBE synthesis stage.

The disadvantage of this method is the high energy consumption at the stages of separation of excess methanol from MTBE and spent C ₄ hydrocarbons, the content of which in the latter is 3.8 wt.%. Energy consumption for the separation of methanol from spent hydrocarbons is significantly increased when using C ₄ fractions with a low content of isobutylene, for example, butane-butylene fraction of catalytic cracking. Besides conducting ether synthesis process at a temperature of 30-50 ^{° C} and said molar ratio of the starting reactants reduces the reaction rate and thus the performance of the catalyst.

The aim of the invention is to reduce energy consumption at the stage of separation of methanol from the spent C ₄ fraction and increase the productivity of the catalyst.

The goal is achieved by the proposed method for the production of methyl tert-butyl ether by contacting an isobutylene-containing C ₄ fraction and methanol in the liquid phase in two reaction zones at an elevated temperature in the presence of a catalyst - macroporous sulfocationionite in H form with a molar ratio of methanol: isobutylene equal to 0.90-0-0 , 99: 1, 85-95% of the original feed C ₄ fraction to the first reaction zone and maintaining the temperature in the second reaction zone in the range of 20-40 ° ^C.

When comparing with the prototype, it is seen that maintaining the molar ratio of methanol: isobutylene is equal to M 0.90-0.99: 1, supplying 85-95% of the initial C ₄ fraction to the first reaction zone and maintaining the temperature in the second reaction zone in the range of 20 ^-40 ° C are the hallmark and, therefore, the proposed technical solution meets the criterion of "novelty."

It is known [1] that, in the synthesis of MTBE, in order to achieve a high degree of conversion of the starting reagents, it is necessary to maintain a low temperature, however, the reaction rate decreases and it is impossible to reach a state close to equilibrium for the contact time of the reaction mixture with the catalyst acceptable under industrial conditions. It was found that with a molar ratio of methanol: isobutylene equal to 0.90-0.99: 1, after contacting 85-95% of the initial C ₄ fraction of its total amount with methanol at an elevated temperature in the presence of a catalyst - macroporous sulfocationion H form significantly increases the rate of synthesis of MTBE over the temperature range 20-40 ^{° C,} which improves the catalyst productivity and lower energy consumption for the steps of isolating methanol from the spent C ₄ fraction by achieving a high conversion of starting 's reactant. The above synthesis process of MTBE under the proposed conditions is unknown and differs from similar methods for producing ether, therefore, the invention meets the criterion of "significant differences".

The process of obtaining MTBE is carried out in the liquid phase according to a continuous technological scheme. The flow of methanol and 85-95% of the initial C ₄ fraction of its total amount taken in a molar ratio of methanol: isobutylene equal to 0.90-0.99: 1 is continuously mixed, then the mixture is heated in a heat exchanger and sent to the first reaction zone reactor in which the temperature is maintained at 50-100 ^C. The remaining 5-15% of the original C ₄ fraction is metered into effluent from the first reaction zone effluent, which is cooled and fed to the second reaction zone where the temperature is maintained within 20-40 ^{° C} Macroporous Sulphocati Used as Catalyst it is in H-form. The reaction mass exiting the reactor is fed to a distillation column, on top of which spent hydrocarbons containing a small amount of methanol are distilled off, and commercial MTBE is removed from the cube.

 The invention is illustrated by the following examples.

PRI me R 1. The synthesis of MTBE is carried out on a continuous installation in a metal reactor with an inner diameter of 20 mm, equipped with a thermostatic jacket. The reactor has two reaction zones, between which an intermediate heat exchanger is located. The catalyst used is sulfonic cation exchanger KU-23 in the H-form (GOST 20298-74). Methanol (GOST 2222-78, premium) and two streams — the isobutanisobutylene fraction containing 14.0 wt.% Isobutylene — are continuously fed into the reactor. The C ₄ fraction is spent after the synthesis of dimethyldioxane by reacting formaldehyde and isobutylene. The total molar ratio of methanol: isobutylene is maintained at 0.97: 1. The first reaction zone serves 95% of the initial C ₄ fraction of its total quantity, the temperature is maintained 50-100 ^{° C} by circulation of the coolant in the reactor jacket and temperature control at inlet, the volumetric feed rate of the initial mixture is 40 h ^-1 . Then, the remaining 5% of the initial C ₄ fraction of its total amount is added to the reaction mass, cooled and sent to the second reaction zone with a space velocity of 5 h ⁻¹ . The temperature in the second reaction zone is maintained at 25 ^° C. The pressure in the reactor is 2 MPa (20 kg / cm ² ).

The reaction mass exiting the reactor is fed to a distillation column, where, at a pressure of 0.5 MPa (5 kg / cm ² ), unreacted hydrocarbons are distilled off, which contain 0.1 wt.% Methanol and 0.66 wt.% Isobutylene. This C ₄ fraction can be further used without water washing of methanol, which is necessary for the prototype, and thereby eliminate significant energy consumption. Cube columns withdraw commodity MTBE, which contains trace amounts of isobutylene dimers. The productivity of the catalyst is 0.46 kg MTBE / l˙cat˙ch, which is 0.24 kg MTBE / l˙cat˙ch higher compared to the prototype (see example 5 of the prototype).

PRI me R 2. The synthesis of MTBE is carried out according to the technology described in example 1. Methanol and isobutylene contained in the isobutane-isobutylene fraction, served in a molar ratio of 0.90: 1. The first reaction zone is sent 85% of the initial C ₄ fraction of its total quantity, the second reaction zone - the remaining 15% and the temperature is maintained at 40 ° ^C.

Leaving the reactor, the reaction mass is fed into a distillation column and the unreacted C ₄ hydrocarbons, which contain 0.1 wt. % methanol and 1.77 wt.% isobutylene. Cube columns withdraw commodity MTBE, which contains trace amounts of isobutylene dimers. Catalyst productivity 0.43 kg MTBE / lЭcat˙ch.

PRI me R 3. The synthesis of MTBE is carried out according to the technology described in example 1. Methanol and isobutylene contained in the isobutane-isobutylene fraction, served in a molar ratio of 0.99: 1. The first reaction zone is sent 95% of the initial C ₄ fraction of its total quantity, the second reaction zone - the remaining 5% and the temperature is kept 25 ° ^C.

Leaving the reactor, the reaction mass is fed into a distillation column and the unreacted C ₄ hydrocarbons, which contain 0.1 wt. % methanol and 0.34 wt.% isobutylene. Cube columns withdraw commodity MTBE, which contains trace amounts of isobutylene dimers. The productivity of the catalyst is 0.46 kg MTBE / l˙cat˙ch.

PRI me R 4. The synthesis of MTBE is carried out according to the technology described in example 1. Methanol and isobutylene contained in the isobutane-isobutylene fraction, served in a molar ratio of 0.94: 1. The first reaction zone is sent 93% of the initial C ₄ fraction of its total quantity, the second reaction zone - the remaining 7% and the temperature was maintained at 20 ° ^C.

The reaction mass leaving the reactor is fed to a distillation column and the unreacted C ₄ hydrocarbons, which contain 0.1 wt. % methanol and 1.14 wt.% isobutylene. Cube columns withdraw commodity MTBE, which contains trace amounts of isobutylene dimers. The productivity of the catalyst is 0.44 kg MTBE / l˙cat˙ch.

PRI me R s 5-8 (comparative). The synthesis of MTBE is carried out according to the technology described in example 1. Methanol and isobutylene contained in the isobutane-isobutylene fraction are fed, respectively, in a molar ratio of 0.85: 1, 0.88: 1, 1: 1 and 1.05: 1. The first reaction zone is sent 90% of the initial C ₄ fraction of its total quantity, the second reaction zone - the remaining 10% and the temperature is maintained at 30 ° ^C. The volumetric feed rate of the reaction mass in the second reaction zone at a molar ratio of 1: 1 is 3 hours ^-1 , at 1.05: 1 - 2 h ^-1 .

 Leaving the reactor, the reaction mass is fed to a distillation column to separate the synthesis products.

 The results of the experiments are shown in the table.

PRI me R s 9-12 (comparative). The synthesis of MTBE is carried out according to the technology described in example 1. Methanol and isobutylene contained in the isobutane-isobutylene fraction are fed in a molar ratio of 0.94: 1. In the second reaction zone is maintained at a temperature ^of 30 C. In the first reaction zone is sent, respectively 80, 83, 97 and 100% of the original C ₄ fraction of its total quantity, the second reaction zone - the remaining amount.

 Leaving the reactor, the reaction mass is fed to a distillation column to separate the synthesis products.

 The results of the experiments are shown in the table.

PRI me R s 13-16 (comparative). The synthesis of MTBE is carried out according to the technology described in example 1. Methanol and isobutylene contained in the isobutane-isobutylene fraction are fed in a molar ratio of 0.94: 1. 90% of the initial C ₄ fraction of its total amount is sent to the first reaction zone, and the remaining 10% to the second reaction zone. In the second reaction zone is maintained at temperature respectively 15, 18, 42 and 45 ° ^C.

 Leaving the reactor, the reaction mass is fed to a distillation column to separate the synthesis products.

 The results of the experiments are shown in the table.

PRI me R 17. The synthesis of MTBE is carried out according to the technology described in example 1. Methanol and a pyrolysis butylene-isobutylene fraction are fed to the reactor after separation of divinyl with an isobutylene content of 45.0 wt.% In a molar ratio of 0.98: 1. 94% of the initial C ₄ fraction of its total amount is sent to the first reaction zone, the volumetric feed rate of the initial mixture is 40 h ^-1 . In the second reaction zone is directed remaining 6% of the original C ₄ fraction, the temperature is kept 25 ° ^C, the WHSV of 5 hr ^-1.

Leaving the reactor, the reaction mass is fed into a distillation column and the unreacted C ₄ hydrocarbons, which contain 0.2 wt. % methanol and 1.9 wt.% isobutylene. Cube columns withdraw commodity MTBE, which contains trace amounts of isobutylene dimers. The productivity of the catalyst is 1.37 kg MTBE / l˙cat˙ch.

The process of synthesis of MTBE at a molar ratio of methanol: isobutylene above 0.99: 1 leads to a decrease in the productivity of the catalyst and an increase in the methanol content in spent hydrocarbons (see examples 7, 8), with a molar ratio of less than 0.90: 1, the degree of conversion is significantly reduced isobutylene and the formation of isobutylene dimers increases (see examples 5, 6). When less than 85% of the initial C ₄ fraction is fed into the first reaction zone, the degree of conversion of the starting reagents decreases and the methanol content in the spent hydrocarbons increases (see examples 9, 10), when more than 95% of the initial C ₄ fraction is fed, isobutylene dimers are formed, the methanol content in the spent hydrocarbons increases (see examples 11, 12). Conducting the synthesis of ester process, the second reaction zone at a temperature below 20 ° ^C leads to reduction in the degree of conversion of the initial reagents and to increase the methanol content in the exhaust hydrocarbons (see. Examples 13, 14), at a temperature above ^{40 °} C increases methanol content in the exhaust hydrocarbons and isobutylene dimers in commercial MTBE (see examples 15, 16).

Claims (1)

METHOD FOR PRODUCING METHYL-TER-BUTHYL ETHER by contacting isobutylene-containing C ₄ -fraction and methanol in the liquid phase at elevated temperature in the presence of a catalyst - macroporous sulfocationionite in H-form in two reaction zones, followed by separation of the reaction mixture and isolation of the target product, characterized in said contacting is carried out at a total molar ratio of methanol: isobutylene 0.90 - 0.99: 1 with a feed of 85 - 95% of the initial C ₄ fraction to the first reaction zone and the remaining quantity to a second, supported Ivanov temperature in the second reaction zone is 20 - 40 ^o C.

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