CS197922B1 - Method of preparation of the zincate catalyser on the active coal as carrier - Google Patents

Description

The invention relates to a process for the preparation of a zinc catalyst for the industrial production of vinyl acetate, on activated carbon as a support.

The presently known production processes for the vinyl acetate synthesis catalyst are almost exclusively based on impregnation of activated carbon, catalyst salt solutions as the active ingredient by various technological processes in part of the carbonation itself, as well as subsequent drying and final product treatment.

However, the quality of the resulting catalyst varies a lot, depending on the characteristics and type of the carrier, but mainly due to the technological operations of the impregnation itself, which is relatively complex and expensive. These drawbacks can be largely eliminated by the preparation of the catalyst according to U.S. Pat. of the author's certificate no. 191 The process in which the impregnation process was replaced by the addition of the active ingredient (zinc oxide) directly to the starting wood feedstock of the activated carbon production, resulting in the finished product being a finished catalyst for the synthesis of vinyl acetate instead of activated carbon. However, further measurements have shown that many of the advantages that this process undoubtedly brings (higher and uniform quality, substantial lower production costs) are relatively sensitive to fluctuations in permissible theological parameters during the water vapor activation phase. It is the most demanding technological node and it is not always possible to prevent partial reduction! of the present metal oxide, which can then clog the device and reduce its content in the product.

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The aforementioned drawbacks are eliminated by a process for the preparation of a zinc catalyst on activated carbon as a carrier which is based on a production process such that a mixture consisting of 100 parts by weight of powdered activated carbon, 10 to 100 parts by weight of wood tar and 5 to 10 parts by weight of zinc oxide and / or ootane. The zinc is homogenized and the mixture is formed into cylinders of 1.5 to 8 mm in diameter and 3 to 15 in lengths. 0 ° C and carbonize at a temperature of up to 600 ° C for 2 to 5 hours. The use of activated carbon eliminates the need for high temperature water vapor carbonation, which represents a substantial difference from known similar preparation methods. The advantages of the proposed method of production are, above all, the simplification of the technology itself, while attaining a high product quality.

The qualitatively higher effect of the catalyst thus produced is manifested in its use in the production of vinyl acetate, where, as a result of its higher surface area, the working time of the individual batches is prolonged and thus the consumption standard of the catalyst per unit monomer production is reduced.

In the case of the use of zinc acetate, a favorable effect on quality is achieved in that, after the bulk of the decomposition substances in the range of 210 to 400 ^° have been separated, decarboxylation of the acetate present to zinc oxide is carried out. the internal parts of the catalyst granules. The proposed method of manufacture can be carried out on a conventional existing manufacturing plant, ensuring consistent / uniform / product quality by perfectly distributing the active ingredient throughout the mass, while maintaining the original porous structure. The simplification of the actual technology compared to the production process in which the required amount of cartalytocyte active substance is added to the basic mixture of charcoal and tar is that the most difficult technological operation, namely the steam vaporisation to be carried out, is excluded from the catalyst production process. at high temperatures in a reducing atmosphere and where there is the greatest risk of possible reduction of a portion of zinc oxide with a negative impact on the quality of the resulting product. The production process is economical and no waste water containing zinc is produced.

Example 1

A screw homogenizer is charged with 100 g of powdered activated carbon with a spheroidal surface area of 1400 m / g and 7 g of zinc oxide powder. After mixing the mixture, 52 g of wood tar are added successively and stirring is continued until the paste is completely homogeneous. The mixture thus prepared is pressed by means of a screw press to rollers with a diameter of 5 mm. Serial granules are sprinkled with powdered activated carbon and do not mature freely for 6 hours. The granules thus prepared are dried in a gentle stream of nitrogen by indirect heating at temperatures up to 120 ° C for 1 hour. The temperature of the feed rises between 95 ° C and 120 ° C in accordance with the amount of gas escaping. After this time, the temperature is gradually raised to 525 ° C, the amount of leakage springs

117 822 gradually decreases with increasing temperature. After reaching this temperature, the batch was cooled with a stream of nitrogen. 106.4 g of catalyst with a content of 5% by weight of zinc and a specific surface area of 1280 m / g were obtained.

During testing in vinyl acetate synthesis, 90 g of vinyl acetate per liter of catalyst per hour was obtained.

Example 2

The base mixture, which consists of 100 g of activated carbon as in Example 1, 35 grams of crystalline zinc ootane powder and 90 grams of wood tar, is treated in the same manner as in Example 1.

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After the batch was cooled, 134 g of catalyst were obtained. The specific surface area was 10,000 m / g by analysis to determine a zinc content of 10.1% by weight and an activity of 140 g of vinyl acetate per liter of catalyst per hour.

The invention can be used in the production of a zinc activated carbon catalyst as a carrier used for the industrial synthesis of vinyl acetate from ethylene and oeto acid.

Claims (1)

OBJECT OF THE INVENTION A process for the preparation of a zinc catalyst on activated carbon as a carrier, characterized in that a mixture consisting of 100 parts by weight of powdered activated carbon, 40 to 100 parts by weight of wood tar and 5 to 40 parts by weight of zinc oxide and / or zinc acetate is homogenized and mixed. It is shaped into cylinders with a diameter of 1.5 to 8 mm and lengths of 3 to 15 nm, which are dusted with powdered activated carbon, aged for 6 to 10 hours, then dried for 1 to 3 hours at temperatures up to 170 ° C and carbonized at temperatures. to 600 ° C over 2 to 5 hours.