DE2038120C3 - Process for the production of allyl acetate - Google Patents

Description

The production of alkenyl esters by reacting olefins with carboxylic acids and oxygen ειιι Precious metal-containing catalysts in the gas phase are known. So z. B. when using Ethylene vinyl acetate, if propylene is used, allyl acetate. The reaction is generally carried out at temperatures carried out between 150 and 250 ° C and pressures between 1 and 10 bar. Used as catalysts Precious metal salts or - precious metals of the 8th subgroup of the periodic table such as palladium. Platinum. Ruthenium, rhodium, iridium with specific additives used such as cadmium, gold, bismuth, copper, manganese. The catalysts also contain alkali or Alkaline earth salts. As a carrier material, for. B. silica. Aluminum oxide, aluminum silicate can be used. A large number of different catalysts is known.

When carrying out the process industrially, the carboxylic acid is generally used with the olefin and oxygen passed over the catalyst under the abovementioned reaction conditions. The one in the Reaction zone unconverted fractions are returned to it in the circuit. The question of whether for this Process for the production of alkenyl esters, technical crude olefins can also be used, was used for the production of vinyl acetate from ethylene, Acetic acid and oxygen checked. However, it was found that this was used for the vinyl acetate reaction Ethylene may only contain traces of by-products. The ethylene used for this is of the same quality! the ethylene used for polymerisation purposes.

Is z. B. Ethylene used, which still little; Percent contains ethane, so will the vinyl acetate reaction because of the accumulation of ethane in the cycle, which leads to a considerable reduction in the number of catalysts stung leads, economically unprofitable. Continue to take with decreasing ethylene concentration in the reaction tank. the amount of ethylene which in a side reaction to COj and water is burned, which in addition leads to a decrease in the ethylene yield.

There would be a process for the preparation of allyl acetate by reacting acetic acid with propylene and oxygen in the presence of CO ₂ biii. Temperatures between 140 and 250 ° C and pressures «; between 1 and 10 bar in the gas phase on catalysts: found the noble metals or noble metal compounds!

which is characterized in that the reaction is carried out at a propylene concentration in the reaction gas below 30% by volume in the presence of the 0.2 to 5.0 times the amount of propane, based on the amount of propylene, performs. Preferably 0.5 to 2.0 times the amount of propane is present.

The method according to the invention surprisingly runs smoothly without the disadvantages mentioned above, which occur in the reaction of ethylene to vinyl acetate.

It was also surprising that the AHyl acetate reaction without a significant drop in the allyl acetate space-time yield and propylene yield can be carried out at a propylene concentration in the reaction gas, in which the vinyl acetate reaction compares with an ethylene content corresponding to that of propylene almost extinguished. It was also surprising that the propylene yield was not the same as the ethylene yield the production of vinyl acetate drops and that a propane content exceeding the propylene concentration in the reaction gas to the Aüyiacetatreaktion practically has no effect, while too high a proportion of ethane in the vinyl acetate process already leads to undesirable side reactions to lead.

The possibility of the allyl acetate reaction at low Propylene concentrations in the presence of large amounts of propane or a.iderer hydrocarbons such as Being able to carry out butane or isobutane increases the economic efficiency of the process.

Instead of pure, high-purity propylene, such as is used for polymerization, can be used significantly cheaper impure propylene, e.g. B. 10% propane or more can be used. the due to the high possible propane content in the reaction gas with that necessary for propane removal The amounts of propylene lost from exhaust gas are low. This also gives you the option of using the propane to be discharged is the secondary product formed by propylene burn-off during the reaction

■ to _{remove CO 2} with. The effort for an additional absorption _{wash for CO 2} -niferniing can be saved. The removal of propane and CO ₂ from the reaction system can be carried out in a simple manner via that dissolved in the liquid products during the condensation

• »5 gas components take place when the Outgassing condensates.

The following examples show that the allyl acetate reaction works even with very low propylene concentrations in the reaction gas in the presence of an amount of propane in excess of the amount of propylene present economically interesting allyl acetate volume yield can be carried out.

For carrying out the process according to the invention, a reaction procedure according to Figure proved to be useful. The circulating gas stream 1 is passed through the acetic acid evaporator 2, in which the added acetic acid 3 is evaporated. The gas mixture laden with acetic acid passes through the Line 4 to reactor 5. The reactor is 5.60 m long and has an internal diameter of 32 mm. the Temperature regulation takes place via an outer jacket in which the boiling water, its temperature is regulated by an automatic pressure lock, is located. The reactor outlet gas is fed via line 6 to the condenser 7, in which the condensable Components, essentially allyl acetate, unreacted acetic acid and water, are liquefied. That Residual gas mixture is via line 8 and compressor

on 3 «ι on

10 led back to the reaction. Fresh propylene is fed in via line 9 via a Pressure retention on the suction side of the compressor. Fresh oxygen is fed to the cycle gas via line 11. The liquid product runs from the condenser 7 in a storage vessel 12 with automatic standstill. The condensates are depressurized in container 13. the Gas components released under pressure and released during the expansion are released via line 14 discharged Via line 15, exhaust gas can be taken from the ι ο gas circuit.

example 1
(Comparative experiment) _{] 5}

The reactor is filled with 4.4 liters of catalyst, 1.4 percent by weight of palladium acetate and 3 Contains percent by weight potassium acetate on a silica support (spheres) 5 to 6 mm in diameter The percentages given relate to the metal content.

At a pressure upstream of the reactor of 7.0 aa and a catalyst temperature of 193 ° C., 9.4 Nm ^{3 of} a gas mixture of the following composition are passed over the catalyst per hour:

Propylene
acetic acid
oxygen
Carbon dioxide

67 percent by volume

15 percent by volume

8 percent by volume

10 percent by volume

Example 2
(Comparison test)

30th

The carbon dioxide concentration is adjusted via the exhaust gas in the cycle gas

In the condensation vessel 13 there are 5 kg of liquid product per hour, the 50 percent by weight acetic acid, 9.2 percent by weight water, 40 percent by weight allyl acetate, and about 0.8 percent by weight by-products contain. The allyl acetate space-time yield is 455 g / l per hour.

In the reaction, 1 mole of water is formed per mole of allyl acetate.

The amount of water exceeding this stoichiometry results from the total oxidation of propylene, hereinafter referred to as propylene burnup. 3 moles of water (and 3 moles of CO ₂ ) are formed per mole of propylene. A propylene burn-up (based on allyl acetate plus burn-off) of 8.4% is calculated from the allyl acetate / water ratio in the raw condensate.

50

The reaction conditions are as in Example 1. However, the exhaust gas in the gas circuit is set so that the C0 ₂ concentration in the reactor inlet gas is 30 percent by volume, corresponding to a propylene concentration of 47 percent by volume. 4.9 kg of raw condensate are produced per hour. The allyl acetate concentration is 38.5%. the water concentration 9.1 percent by weight, the amount of by-products 0.9 percent by weight. The allyl acetate space time is 430 g / l per hour, the propylene burn-up is 9%.

Example 3
(Comparison test)

The reaction conditions are as in Example 1, except that the exhaust gas is used except for those for analyzers required amount taken away. The CO2 concentration in the reactor inlet gas is 48 percent by volume, corresponding to a propylene concentration of 29 percent by volume. 4.7 kg of raw condensate fall per hour at. The allyl acetate concentration is 34.5 percent by weight, the water concentration 7.9% accordingly an allyl acetate space-time yield of 370 g / l per hour and a propylene burn-off of 9.1%, the concentration of other by-products is 0.7 percent by weight

Example 4
(Comparison test)

The reaction conditions are as in Example 3, ie the exhaust gas is removed except for the amount required for AnaK-sen devices. As much CO ₂ is added to the circulating gas from a CO ₂ -FIasche that the C0 ₂ concentration in the reactor inlet gas be'rägt 65 volume percent, the propylene concentration 12 per cent by volume

The hourly amount of raw condensate is 4.6 kg, the allyl acetate concentration is 32 percent by weight, the by-product concentration 0.7 weight percent. The water concentration 73 percent by weight, corresponding to an allyl acetate space-time yield of 325 g / l per hour and propylene burn-off of 7.9%.

Example 5

The reaction conditions are as in Example 1, but the amount of exhaust gas is regulated so that the C0 ₂ concentration in the reactor inlet gas is 30 percent by volume. So much propane is added to the cycle gas from a propane bottle that the propane concentration in the reactor inlet gas is 20 percent by volume. The propylene concentration is 27 percent by volume; h “the ratio of propane to propylene is 0.75. Every hour, 4.6 kg of crude condensate are obtained, the allyl acetate concentration is 33.1 percent by weight, the by-product concentration 0.8 percent by weight, the water concentration 7.7 percent by weight, corresponding to an allyl acetate space-time yield of 350 g / l per hour and a propylene burn-off of 9.5%.

Example 6

The reaction conditions are analogous to Example 5. However, ^w: rrl the given to the circulating gas of propane increased so that the propane concentration in the reactor inlet gas is 31 volume percent. The propylene concentration drops to 15%, the ratio of propane to propylene is 2.0. 4.5 kg of crude condensate are produced per hour, the allyl acetate concentration is 31% by weight, the by-product concentration 0.7% by weight, the water concentration 7.4% by weight, the allyl acetate space-time yield 318 g / l per hour, the propylene loss 9.7% ,

1 sheet of drawings

Claims (2)

Claims; 1. A process for the production of allyl acetate by reacting acetic acid with propylene and oxygen in the presence of CO ₂ at temperatures between 140 and 250 ⁰ C and pressures between 1 and 10 ata in the gas phase on catalysts which skin noble metals or noble metal compounds, characterized in that, that the reaction is carried out at a propylene concentration in the reaction gas below 30 percent by volume in the presence of 0.2 to 5.0 times the amount of propane, based on the amount of propylene. 2 The method according to claim 1, characterized in that that the reaction in the presence of di; r 05 to 2.0 times the amount of propane, based on the Amount of propylene