DE2411901A1 - Ethyl esters of unsatd. monocarboxylic acids from ethylene and acid - in presence of satd. carboxylic acid or ester, giving rapid reaction and avoiding polymerisation - Google Patents

Abstract

Ethyl esters of 3-4C unsatd. monocarboxylic acids are prepd. by reaction of ethylene with the unsatd. acid (I) in presence of acid catalysts at 70-250 degrees C and 5-500 atmos., in presence of a satd. carboxylic acid (II) and/or its ethyl ester. High reaction rates are achieved, without polymerisation occurring. Distillative sepn. of the ethyl ester of I requires low energy consumption. Acid catalysts include (poly)phosphoric acids, HCl, H2SO4 and/or sulphonic acids, opt. on carriers. Strong acid cation-exchangers or de-cationised zeolites are pref. the amt. of catalyst is 0.1-20 (1-10) wt.% Cu, Ag, Ru, Pd or Pt, as metals or complexes, may be used as promoters, in amt. of 0.1-20 (0.5-5) wt.% w.r.t. acid catalyst. Mono- or di-carboxylic acids which are liquid at reaction temp. and which easily form ethyl esters which can be trans-esterified, are used as II, e.g. beta-ethoxy- or beta-acetoxy-propionic acid or acetic acid. Pref., the b.pt. of the thyl ester of II is higher than that of the ethyl ester of I. Halogenated acids, e.g. chloroacetic aced are pref. Reaction is pref. continuous, esp. by the trickle process. The reaction mixt. esp. contains 2-60 (10-30) wt.% I.

Description

Process for the preparation of ethyl esters of unsaturated monocarboxylic acids The invention relates to a process for the preparation of ethyl esters of unsaturated ones Monocarboxylic acids from ethylene and the corresponding unsaturated carboxylic acid with up to 4 carbon atoms.

It is known to produce olefins and unsaturated carboxylic acids of esters to use. However, these processes are only for the synthesis of esters secondary and tertiary alcohols, e.g. for the production of t-butyl acrylate from acrylic acid and isobutylene (see e.g. USP 3,088,969 and 3,087,962). Ethylene gives namely, in contrast to the higher olefins only under very drastic temperature and pressure conditions with saturated carboxylic acids ethyl ester, which is when using unsaturated organic acids leads to high yield losses. For example, in USP 2 174,985 saturated carboxylic acids with ethylene in the gas phase on various catalysts reacted at a temperature of 200 to 2500C and under a pressure of 50 to 150 atm. Also with catalysts such as hydrogen fluoride or boron fluoride (see USP 2 414 999) or peroxides (cf. USP 2,585,723) must be carried out under high pressure.

The Japanese Patent Application Laid-Open No.

28 969/1970 described ethyl acrylate synthesis from acrylic acid vapors and ethylene at increased pressure on acidic cation exchangers only leads to proportionally low yields.

In addition, the evaporation of acrylic acid at pressures above 1 at difficulties due to polymer formation.

Also the synthesis of the ethyl esters of unsaturated carboxylic acids by Conversion of e.g. acrylic acid with ethylsulfuric acid esters, which are also carried out in situ Reaction of ethylene with sulfuric acid can be formed shows disadvantages, since the sulfuric acid attaches itself to the double bond of the unsaturated Carboxylic acid adds, whereby by-products are formed and the yield decreases will.

It has now been found that ethyl esters of unsaturated monocarboxylic acids can be used by reacting 3 to 4 carbon atoms containing unsaturated monocarboxylic acids with Ethylene in the presence of acidic catalysts at temperatures from 70 to 2500C below Pressures from 5 to 500 at can be produced if one is in the presence of a saturated one Carboxylic acid and / or its ethyl ester works are particularly suitable for this purpose acidic carboxylic acids such as halocarboxylic acids, e.g., chloroacetic acid. Advantage of strong acidic carboxylic acids is the increased reaction rate during esterification and transesterification. A mixture of saturated carboxylic acid and its ethyl ester can advantageously be used as it results from the saturated carboxylic acid and ethylene under the reaction conditions, e.g. as an equilibrium mixture. The new method is preferably used at temperatures from 120 to 2000C and pressures from 30 to 200 at. As acidic catalysts come acids such as phosphoric acid, polyphosphoric acids, hydrogen chloride, sulfuric acid and / or sulfonic acids in question, which may be supported on carriers such as silicon dioxide, Boron phosphate, aluminum phosphate or carbon can be applied. With advantage strongly acidic cation exchangers or decationized zeolites are used. The amount of acidic catalysts is generally from 0.1 to 20, preferably 1 to 10% by weight, based on the weight of the reaction mixture. With one continuous operated reaction with fixed catalyst can be the solution to be converted Acid come into contact with a larger amount of catalyst depending on the residence time. Activators for the catalysts can be copper, silver, ruthenium, palladium or platinum in the form of their optionally complex compounds or in metallic form Form added to the reaction mixture or fixed on the solid catalysts. The activators can be used at the new process usually in quantities of 0.1 to 20%, preferably from 0.5 to 5% by weight, based on the weight of the acidic Catalysts are used.

The process according to the invention is preferably carried out continuously. You can either choose from the saturated carboxylic acid, its ethyl ester or one Mix of the two go out.

The reaction mixture generally contains 2 to 60 wt. Ffi of unsaturated monocarboxylic acid to be esterified, preferably 10 to 30% by weight, but can in some cases also at a concentration of the unsaturated carboxylic acid from over 60% up to 85% by weight, based on the reaction mixture, can be worked.

With continuous operation and with recycling of the reactants after separation of the ethyl ester of the unsaturated monocarboxylic acid in a desired The extent and addition of the converted unsaturated monocarboxylic acid is established Equilibrium between the carboxylic acids and their ethyl esters.

In the new process, the unsaturated carboxylic acids and their esters by dilution with the saturated carboxylic acid and their esters protected from polymerization without affecting the rate of ethylene deposition is decreased. Practically all saturated carboxylic acids come as saturated carboxylic acids, especially mono- and dicarboxylic acids, in question, under the reaction conditions are liquid and stable, which easily with ethylene under the reaction conditions Form ethyl esters and their ethyl esters can be easily transesterified, with as much as possible no by-products should be formed. Examples are ß-ethoxypropionic acid (which is a by-product of the process in the production of ethyl acrylate), also acetic acid and ß-acetoxypropionic acid. Those are of particular interest Carboxylic acids, the ethyl esters of which boil higher than the ethyl esters of the unsaturated ones Monocarboxylic acid. This has the following advantages associated with working up by distillation: The unsaturated compounds are in a reduced state until just before they are isolated Form before, causing the formation of oligomers or addition compounds is decreased. The energy required for the separation of the reaction mixture by distillation is lower than when using a lower boiling saturated carboxylic acid ethyl ester, since only the resulting unsaturated ethyl ester has to be distilled off.

Suitable as a particular embodiment of the method according to the invention the trickle mode. Here, the mixture of unsaturated carboxylic acid, saturated carboxylic acid and / or its ethyl ester under ethylene pressure over the solid in the reaction chamber arranged contact or in the case of liquid acid catalysts Let trickle over internals in the reaction space. The liquid flows in these palls Phase expediently together with ethylene over the catalyst. You can do that with ethylene but also pass through the reaction chamber in countercurrent to the liquid phase.

You can also do it in light flow in a highly loaded packed column work.

In another embodiment, the catalyst can be in the reaction mixture dissolved or suspended together with ethylene are passed through the reaction zone. Finally, you can also use the so-called swamp mode by going over a fixed catalyst in the reaction space, the reaction mixture together with ethylene conducts. The catalyst always remains covered by the liquid phase.

Refer to the parts and percentages given in the following examples focus on the weight.

Example 1 In a rolling autoclave (empty volume 0.8 liters) with Hastelloy-C lining a mixture of 40 wt.% 2-ethylhexanoic acid, 40 ffi ethylhexanoic acid ethyl ester and 14% acrylic acid with 6% of a commercially available strongly acidic cation exchanger in the form (for Dowex 50 WX 8) previously obtained by azeotropic distillation with benzene was dewatered, heated with ethylene under a pressure of 200 at for 4 hours at 1500C. After cooling down, the Discharge of the acrylic acid conversion by gas chromatography determined to be 51%. Ethyl acrylate was produced with a selectivity of 74%.

Example 2 In the rolling autoclave given in Example 1, a Mixture of 78 parts of 2-ethylhexanoic acid and 14 parts of acrylic acid with 8 parts of 85 % aqueous phosphoric acid under an ethylene pressure of 160 at 2 hours at 2000C heated. After cooling, the acrylic acid conversion is 49 by gas chromatography certainly; Ethyl acrylate selectivity: 56.

Example 3 In a sump furnace with Hastelloy-C lining (empty volume 3 liters) become more than 1.0 liter of dehydrated, commercially available, strongly acidic cation exchanger in the H (3-Form (Dowex 50 WX 8) in the liquid phase 1.0 liter of mixture per hour 20 parts of acrylic acid and 80 parts of ethyl acetate and 600 liters of ethylene passed. The temperature is 150ob and the pressure is 80 atm. A conversion of acrylic acid is obtained of 70% with an ethyl acrylate selectivity of 75% (determined by gas chromatography).

Example 4 In a trickle furnace with a stainless steel lining (empty volume 3 titer) are dehydrated, strongly acidic, macroporous cation exchanger over 2.1 liters in the -F9rm (for Lewatit CA 9259) an hourly 0.6 liter mixture of 10 parts acrylic acid, 17 parts of 2-ethylhexanoic acid and 73 parts of 2-ethylhexanoic acid ethyl ester in countercurrent led to 310 liters of ethylene. The temperature is 14,000, the pressure 60 at 2-Ethylhexanoic acid concentration is chosen so that it is reflected in the passage through did not change the oven. An average acrylic acid conversion is obtained over 150 operating hours of 52 / o with an ethyl acrylate selectivity of 95% (determined by gas chromatography).

Example 5 In a 0.3 liter sump furnace with a stainless steel lining More than 0.2 liters of dehydrated acidic cation exchanger in the H # form (# Dowex 50 WX 8) in trickle mode an hourly 0.3 liter mixture of 12.5% acrylic acid, 7.5% chloroacetic acid and 90% ethyl chloroacetate and 200 liters of ethylene directed.

The temperature is 1400C at a pressure of 60 at. The acrylic acid conversion is 87 with an ethyl acrylate selectivity of 96.

Claims (1)

Claim Process for the preparation of ethyl esters of unsaturated monocarboxylic acids with 3 to 4 carbon atoms due to the addition of ethylene to the unsaturated carboxylic acids in the presence of acidic catalysts at temperatures from 70 to 2500C and under pressure from 5 to 500 at, characterized in that in the presence of a saturated Carboxylic acid and / or its ethyl ester works.