CS213089B1 - Vinyl acetate synthesis catalyst - Google Patents

Abstract

The invention relates to a catalyst for the synthesis of vinyl acetate with a low content of active skin in a mixture with an anticuprene additive. In the synthesis of vinyl acetate from acetylene and acetic acid by the vapor phase method, a catalyst is usually used, which consists of activated carbon as a carrier and a catalytically active substance in an amount of 30% or more by weight. Zinc acetate is almost exclusively used as an active substance, possibly in a mixture with promoters. Catalysts prepared in this way, as a result of a very low specific surface area, work only for a very limited time, their activity rapidly decreases, which reduces the achieved capacity of the production equipment and increases production costs per unit amount of product. The subject of the invention is a catalyst for the synthesis of vinyl acetate with a low content of the active ingredient in the mixture and an anticuprene additive. Its essence is that the catalyst consists of 72 to 80 parts by weight of activated carbon, 20 to 28 parts by weight of zinc acetate β with two water molecules and 0.01 to 0.09 parts by weight of bismuth acetate based on the dry product. In this way, the lifetime of the catalyst will be extended, which will increase the productivity of the equipment and significantly reduce the cost of producing a unit amount of monomer.

Description

The invention relates to a catalyst for the synthesis of vinyl acetate with a low content of active ingredient in a mixture with an anticuprene additive.

In the synthesis of vinyl acetate from acetylene and acetic acid by the vapor phase method, a catalyst is usually used, which consists of an activated carbon support and a catalytically active substance in an amount of 30% or more by weight. Zinc acetate is used almost exclusively as the active substance, or in a mixture with promoters. Due to the very low specific surface area, the catalysts prepared in this way only work for a very limited time, their activity decreases rapidly, which reduces the achieved capacity of the production equipment and increases the production costs per unit amount of product. Despite many attempts, there is no known industrial use of catalysts with a lower content of active substance than 30% by weight, expressed as zinc acetate and water of crystallization molecules, and all commercially available catalysts have a minimum acetate content of 30% by weight.

The above-mentioned shortcomings are eliminated according to the invention by a catalyst for the synthesis of vinyl acetate with a low content of the active component in a mixture with an anticuprene additive. Its essence lies in the fact that the catalyst consists of 72 to 80 parts by weight of activated carbon, 20 to 28 parts by weight of zinc acetate with two molecules of water and 0.01 to 0.09 parts by weight of bismuth acetate based on the dry product. The essence of the invention lies in a suitable combination of the content of the active component with the anticuprene additive. While the low content of zinc acetate ensures the necessary prerequisite for an extended service life due to a high residual specific surface and therefore a sufficient porous structure of the catalyst particles while maintaining activity, the addition of bismuth acetate prevents the formation of deposits, which maintains the aforementioned porous structure for a sufficiently long time.

The effect of the method according to the invention lies primarily in extending the service life of the catalyst in industrial use in the production of vinyl acetate, while maintaining high activity and selectivity. Based on successful performance tests on a laboratory scale, the catalyst prepared in this way was successfully tested directly in production as described in the following examples.

Example 1

In a laboratory apparatus, the synthesis of vinyl acetate was carried out at a temperature of 200 °C.

200 ml batch of two catalyst samples. The first sample represented a traditional catalyst and had a composition of 30.39 wt. % zinc acetate and a specific surface area of 108 m/g.

The second sample was prepared by the process according to the invention with a non-trace active ingredient content of 24.54 wt. % zinc acetate, 0.034 wt. % bismuth acetate and a specific surface area of 405 m/g.

The synthesis was carried out in both examples without interruption for 50 hours. The synthesis mixture consisting of 22 l/hour of acetylene and 14 g/hour of acetic acid was condensed at the reactor outlet by cooling to a temperature of -30 °C and subjected to analytical analysis, from which the catalyst productivity was calculated. The catalyst samples after the experiment were subjected to analysis for specific surface area and content of polymeric substances. The following results were measured:

213,088

Sample cat. Cat.by PV gVAC/hour kg cat. 106 138 0 specific surface area (m/g) 0 87 Polymer content (% by weight) 8.6 0.8 average acid conversion to vinyl acetate 64.3' 74.5

Example 2

Under operating conditions, vinyl acetate was produced using a catalyst prepared according to the invention. The working conditions and technological regime of production were maintained in accordance with the valid technological regulations. To exclude the influence of fluctuations in the quality of raw materials and technological conditions within the permissible ranges, long-term monitoring of several production cycles was carried out. The average catalyst life time increased from the original 41 days to 48 days.

Claims (1)

Catalyst for the synthesis of low active ingredient vinyl acetate in an anti-cuprene additive composition, characterized in that the catalyst consists of 72 to 80 parts by weight of activated carbon, 20 to 28 parts by weight of zinc acetate with two water molecules and 0.01 to 0.09 parts by weight of bismuth acetate based on dry product. Printed by Moravian Printing Works,