CS240318B1 - Method of vinyl acetate production - Google Patents

Abstract

The solution relates to the production of vinyl acetate from acetic acid and acetylene; to acetic acid used for the preparation and / or the synthesis mixture chlorinated before entering the reactor hydrocarbons having carbon numbers 1 to 3 in an amount of 0.001 to 5 wt to the added acetic acid in the synthesis mixture.

Description

The present invention relates to a process for the production of vinyl acetate from acetic acid and acetylene, wherein chlorine hydrocarbons having a carbon number of 1 to 3 in an amount of 0.001 to 5 are added to the acetic acid used to prepare the synthesis mixture and / or to the synthesis mixture before entering the reactor. % by weight, calculated on the acetic acid added in the synthesis mixture.

The invention relates to a process for the production of vinyl acetate from ccic acid and acetylene in the presence of chlorinated hydrocarbons under defined liquid and vapor phase conditions.

Production of vinyl acetate on an industrial scale is not associated with any technological difficulties. However, it has been shown that the evaporation of acetic acid in the evaporator over time leads to frequent clogging of the exchange surfaces and connecting lines in the liquid phase as well as to a reduction of the free pore volume of the catalyst by clogging of the pores with polymeric and other undefined substances. These negative effects both lead to an increase in energy consumption, a reduction in the working time fund, and a reduction in the catalyst cycle time, which all results in a decrease in vinyl acetate production. In operation, it has also been shown that the use of active catalysts causes a sudden increase in the reaction temperature ("drift of reaction"), resulting in the destruction of the feedstocks with excessive heat release, resulting in an uncontrollable reaction that may trigger an emergency This condition in the production of vinyl acetate is very dangerous, because during a longer period of time, some parts of the technological equipment are heated up to the red glow.

According to the invention, the process for producing vinyl acetate from acetic acid and acetylene in the presence of a polymerization inhibitor is carried out by adding chlorinated hydrocarbons having a carbon number of 1 to 3 to the acetic acid used to prepare the synthesis mixture and / or to the synthesis mixture before entering the reactor. % of trichlorethylene, in an amount of 0.001 to 5 wt. calculated on the acetic acid added in the synthesis mixture.

In the event of an uncontrolled reaction ("drift") in vinyl acetate production, the reaction can be handled without shutting down the vinyl acetate production by adding 1,1,2-trichlorethylene directly to the synthesis mixture before entering the reactor at 20 to 200 ppm to the total amount of synthesis mixture. .

The main advantage of the method according to the invention is to ensure the long-term, uniform and also efficient operation of the acetic acid evaporator for the preparation of the synthesis mixture in both the liquid and the gas phase. Another advantage is that on the catalyst surface in the reactor, the presence of 1,1,2-trichlorethylene prevents clogging of the catalyst pores by the products of polymerization and condensation reactions. and thus prolongs the production activity of the catalyst. At the same time, the low concentration of 1,1,2-trichlorethylene in the synthesis mixture in the amount of 2 to 15 ppm stabilizes the activity of the very active catalytic centers at a lower level and thus prevents their rapid deactivation, thereby achieving higher catalyst production. At the same time, by its stabilizing effect on the active centers of 1,1,2-trichlorethylene, it reduces the risk of “drift” of the reaction, which increases the uniformity of production and in particular its safety.

Particularly over the safety of vinyl acetate production, the process according to the invention has the considerable advantage that it is possible to complete the reaction without stabilizing the production in the event of uncontrolled reaction by adding 1,1,2-trichlorethylene over 0.5 1.0 wt. .

The addition of 1,1,2-trichlorethylene has a complex effect in the process by preventing the formation of undesirable substances. in the liquid and gaseous phases, it also stabilizes the activity of the catalyst and prevents uncontrolled reaction, which saves energy, streamlines production, and increases working time.

Some embodiments of the invention are illustrated by the following examples. EXAMPLE

A continuous reactor for the production of vinyl acetate with a reactor containing 100 ml of catalyst (zinc acetate on activated carbon) is fed continuously to an acetic acid evaporator of 5 g / h of pure acetic acid and 5 g / h of regenerated acetic acid from vinyl acetate production. 0.27 wt. % of vinyl acetate as well as 0.07 wt. 1,1,2-trichlorethylene.

After 96 hours of continuous operation of the acetic acid evaporator, the residue in the flask content is increased by 69.3% by weight. in a comparative experiment without the addition of 1,1,2-trichlorethylene, the residue was increased over the same time at the same acetic acid flow rate by 142.7 wt%.

Example 2

In the same apparatus as in Example 1, 10 g of acetic acid (composition, 1 d. Of pure acetic acid and 1 d. Of regenerated acetic acid with a vinyl acetate content of 0.27 wt.%) With a content of 0.01 wt. . 1,1,2-trichlorethylene and 25 N l / h of acetylene at a catalyst temperature of 170-185 ° C.

After 240 hours of continuous operation, the total pore volume of the catalyst decreased by 7.2%. In a comparative experiment under the same conditions but without 1,1,2-trichlorethylene, the total catalyst volume decreased by 10.6%.

Example 3

In the same apparatus as in Example 1, 10 g of acetic acid, composition as in Example 2, containing 0.002 wt. 1,1,2-trichlorethylene and 25 N l / h of acetylene. Under the above conditions, a 2.1 wt. more vinyl acetate than in the comparative experiment under the same conditions without the addition of 1,1,2-trichlorethylene.

example

In the same apparatus as in Example 1, 10 g of acetic acid of the same composition as in Example 2 are charged per 100 ml of catalyst.

B and 25 N l / h of acetylene. A gradual increase in temperature results in a sudden temperature rise in the catalyst. At a temperature of 210 ° C in the catalyst, 1,1,2-trichlorethylene is fed continuously to the synthesis preheater so that its concentration in the total synthesis mixture is 170 to 190 ppm. The catalyst temperature was stabilized at 180 ° C for 45 minutes, following the reaction conditions given at the beginning of the example.

Claims (2)

SUBJECT Process for producing vinyl acetate from acetic acid and acetylene in the presence of a polymerization inhibitor, characterized in that chlorinated hydrocarbons having a carbon number of 1 to 3 are added to the acetic acid used to prepare the synthesis mixture and / or to the synthesis mixture before entering the reactor. %, preferably trichlorethylene, in an amount of 0.001 to 5 wt. calculated on the acetic acid added in the synthesis mixture.