RU2798601C1 - Method for producing vinyl n-butyl ether - Google Patents

Abstract

FIELD: production of vinyl n-butyl ether.

SUBSTANCE: invention is related to the process for production of vinyl n-butyl ether used as an intermediate for production of (co)polymers and plasticizers, for example, in the medical industry or in the production of agricultural chemicals. The method consists of a gas-phase catalytic dealkoxylation of dibutyl acetal in presence of a catalyst containing palladium deposited on the base. The mass fraction of palladium in the catalyst deposited on the base in form of aluminium γ-oxide, is 1.5%, and the process is carried out at a volumetric feed rate of raw materials of 44 hours^-1 and a process temperature of 275°C.

EFFECT: increase in the selectivity of formation of the target product.

2 cl, 1 tbl, 6 ex

Description

The present invention relates to a process for the production of vinyl n-butyl ether (VBE) used as an intermediate for the production of (co)polymers and plasticizers, for example in the medical industry or in the production of agricultural chemicals.

The processing of acetals into vinyl alkyl ethers is carried out by decomposition of acetals on various catalysts (Yanovskaya L.A., Yufit S.S., Kucherov V.F., Chemistry of acetals, M.: Nauka 1975. - 275 S.). As a rule, the activity of catalysts used in decomposition processes does not ensure efficient processing of acetal into the target product, and in the crude ether removed from the reaction mass during the reaction, along with alcohol, unreacted acetal is present, which, after separation from the decomposition products, is returned to recycle to the dealkoxylation step. The presence in the recycling of a significant amount of "return" acetal as a whole complicates the processing of acetal due to additional technological operations.

Known methods of obtaining VBE by decomposition of dibutyl acetal (DBA) under conditions of liquid-phase catalysis: sulfanilic acid at 200°C, providing a yield of the target product of 65%; a mixture of quinoline and phosphoric acid, where the WBE yield is 97.8% with a DBA conversion of 52%; tributylbenzylammonium chloride (patent RU2144021) or hydrochloric acid tributylamine (patent RU2179967) at 160-180°C for 6-7 hours. The amount of added catalyst is 2.5-5.0% by weight of DBA. These components of the catalytic system yield WBE 97-98%.

However, when using liquid catalytic systems, there is a long induction period for the process to reach the distillation mode of the target fraction, instability of the system, the difficulty of constantly maintaining a high level of DBA conversion, and the presence of trace amounts of catalyst in the target WBE.

Known gas-phase method for producing vinyl esters (patent US4014941A) by dealkoxylation in the presence of calcium phosphates or products formed during their calcination, at a temperature of 200-350 ^o C and a pressure of 1-50 atm and feedstock feeds of 0.001-0.1 mol/hour per 1 g of catalyst in a stream of inert carrier gas (nitrogen, helium, argon, etc.). The selectivity for the formation of vinyl esters is 89%, however. the method is implemented by a complex scheme of the technological process and the need to create an effective system for trapping the reaction products.

Known methods of gas-phase splitting of acetals to obtain vinyl esters under conditions of heterogeneous catalysis in the presence of: calcium oxide at 200-300°C (patent US4396782A), apatite (patents US20090227818A1, JP5209941B2), apatite, barium oxide on silica gel (obtained by heating a mixture of barium hydroxide and silica gel) at 200-350°C at an acetal space velocity of 0.2-10.0 mol/hour per 1 g of catalyst (GB681059A patent), calcium chloride at 225°C (US3546300A patent).

An analysis of the available methods for the production of vinyl ethers by dealkoxylation of acetals indicates that they are characterized by the need for the presence of such catalysts, which imply a complex and lengthy technology for their use, the need to use additional reagents, which makes the industrial process unprofitable. Most of the considered methods for obtaining vinyl ethers by gas-phase cleavage of acetals are characterized by selectivity, which does not exceed 70-75%.

Traditionally, various supported catalysts are used in industry as selective catalysts (Avetisov A.K., Bruk L.G. Applied Catalysis, M.: Lan 2020. - 200 p.) allowing to increase the surface of the active component, prevent sintering and save expensive metal. As active components of supported catalysts, platinum group metals are used in industry: Pt, Rh, Ru, Pd supported on carbon, aluminum oxide, silicon oxide and other carriers. In addition to the platinum group metals, copper, cobalt, and nickel deposited on various carriers are also used.

The closest analogue of the proposed method is the production of WBE by dealkoxylation of DBA when heated with a catalytic substance containing a precious metal deposited on a base, consisting of, for example, 400 g of asbestos, on which 10% of its mass of palladium is deposited (patent US1931858A). A pair of acetaldehyde diethyl acetal is passed over the catalyst at a temperature of 270° C. at a rate of about 500 grams per hour (reverse feed rate is about 4.3 h ^-1 ). The fraction below 40°C is almost pure vinyl ethyl ether, and the fraction of the reaction product, which boils above 40°C, consists of ethanol and unchanged (unreacted) acetal, which reduces the overall conversion.

When implementing this method, heat-resistant substances from metals other than alkali metals can be used as activating or stabilizing additives. The dealkoxylation process can be carried out in the presence of a volatile inert diluent, such as nitrogen, carbon dioxide, methane, a small amount of water vapor or vapors of alcohols, ethers or hydrocarbons such as benzene or gasoline. Depending on the implementation of the method and the catalyst used, the method provides the yield of the target product at the level of 60-75%.

The technical problem, the solution of which is proposed in the present invention, is to optimize the technological process, namely, to develop a method for obtaining WBE by gas-phase catalytic dealkoxylation of DBA, which is characterized by an increase in the yield of the target product without complicating the technology of its production and even simplifying it. This problem is solved by the fact that a method is proposed for obtaining WBE by gas-phase dealkoxylation of DBA in the presence of a catalyst, which is a palladium mass fraction of not more than 1.5%, deposited on a base in the form of γ-alumina (for example, hydrogenation catalyst RK-415, TU 2172- 031-14648393-2004). The purity of the original reagent dibutylacetal - 96-97% (mass.) The process is carried out in a flow type reactor at a temperature of at least 275°C, a pressure of 1 atm and a feed rate of the reagents of at least 44 h ^-1 . The selectivity of the resulting target WBE during the implementation of the technological process is 84-99%, which is a relevant parameter for modern large-tonnage production. The absence of additional technological procedures for the isolation and purification of the final product, a significant reduction in the amount of residual fractions, the minimum content of the palladium component in the catalyst ensures an increase in conversion.

The technical result is an increase in the selectivity of the formation of the target product up to 84-99%, an increase in the conversion.

The implementation of the proposed method for obtaining WBE is illustrated by the examples below.

Example 1. A catalyst containing palladium with a mass fraction of 1.5%, deposited on a base in the form of γ-alumina, is put into operation by heating to 275°C at a rate of 5°C/min and kept at the process temperature for 30 min. Next, 100 ml of DBA is supplied with a volumetric feed rate of 350 hours^-1. The reaction mixture is cooled and discharged from the reactor. The content of WBE is determined by the chromatographic method. The selectivity of WBE formation is 99%.

Example 2. A catalyst containing palladium with a mass fraction of 1.5%, deposited on a base in the form of γ-alumina, is brought into operation by heating to 275°C at a rate of 5°C/min and kept at the process temperature for 30 min. Next, 100 ml of DBA is supplied with a volumetric feed rate of 90 hours^-1. The reaction mixture is cooled and discharged from the reactor. The content of WBE is determined by the chromatographic method. The selectivity of WBE formation is 89%.

Example 3. A catalyst containing palladium with a mass fraction of 1.5%, deposited on a base in the form of γ-alumina, is brought into operation by heating to 275°C at a rate of 5°C/min and kept at the process temperature for 30 min. Next, 100 ml of DBA is supplied with a volumetric feed rate of 44 hours^-1. The reaction mixture is cooled and discharged from the reactor. The content of WBE is determined by the chromatographic method. The selectivity of WBE formation is 94%.

Example 4. A catalyst containing palladium with a mass fraction of 1.5%, deposited on a base in the form of γ-alumina, is put into operation by heating to 275°C at a rate of 5°C/min and kept at the process temperature for 30 min. Next, 100 ml of DBA is supplied with a volumetric feed rate of 350 hours^-1. The reaction mixture is cooled and discharged from the reactor. The content of WBE is determined by the chromatographic method. The selectivity of WBE formation is 76%.

Example 5. A catalyst containing palladium with a mass fraction of 1.5%, deposited on a base in the form of γ-alumina, is put into operation by heating to 275°C at a rate of 5°C/min and kept at the process temperature for 30 min. Next, 100 ml of DBA is supplied with a volumetric feed rate of 22 hours^-1. The reaction mixture is cooled and discharged from the reactor. The content of WBE is determined by the chromatographic method. The selectivity of WBE formation is 70%.

Example 6. A catalyst containing palladium with a mass fraction of 1.5%, deposited on a base in the form of γ-alumina, is put into operation by heating to 300°C at a rate of 5°C/min and kept at the process temperature for 30 min. Next, 100 ml of DBA is supplied with a volumetric feed rate of 350 hours^-1. The reaction mixture is cooled and discharged from the reactor. The content of WBE is determined by the chromatographic method. The selectivity of WBE formation is 84%.

The results of WBE synthesis are shown in Table 1.

Table 1.

experience number Volumetric feed rate of raw materials, hour ^-1 Temperature, °С WBE selectivity, % 1 350 275 99 2 90 275 89 3 44 275 94 4 350 250 76 5 22 275 70 6 350 300 84

The table shows that the process is carried out at a feed space velocity of 44 h ^-1 and a process temperature of 275°C for at least 30 min, in the presence of a catalyst containing palladium deposited on the base in the form of γ-alumina and mass shares of not more than 1.5%, allows you to achieve selectivity VBE 84-99%.

Claims (2)

1. A method for producing vinyl-n-butyl ether by gas-phase catalytic dealkoxylation of dibutyl acetal, in the presence of a catalyst containing palladium deposited on the base, characterized in that the mass fraction of palladium in the catalyst deposited on the base in the form of γ-alumina is 1.5 %, the process is carried out at a volumetric feed rate of 44 hours ^-1 and a process temperature of 275°C. 2. The method according to p. 1, characterized in that the process is carried out for at least 30 minutes.