DD234141A3 - METHOD FOR PRODUCING ZINC ACETATE ACTIVE CARBON CATALYSTS FOR VINYL ACETATE SYNTHESIS - Google Patents

Abstract

Improved zinc acetate activated carbon catalysts for vinyl acetate synthesis from acetylene and acetic acid are obtained through the use of special activated charcoal carriers. The carrier activated charcoal used had an inner BET surface area of 1 250-1 700 m2 / g, a mesopore volume (40 Arp500 A) of 0.1-0.25 cm 3 / g, a macropore volume (500 Arp 10 000 A) of 0.15%. 0.5 cm3 / g, and a gas chromatographically determined retention volume for benzene of 0.3 l / g at 200C. The zinc acetate activated carbon catalyst obtained by the conventional production process from this activated carbon has a life span increased by 50%.

Description

Field of application of the invention

The invention relates to a process for the preparation of zinc acetate activated carbon catalysts for vinyl ester synthesis. The zinc acetate activated carbon catalysts are used, for example, in the production of vinyl acetate from acetylene and acetic acid in the gas phase in a fixed bed.

Characteristic of the known technical solutions

It is known that zinc acetate activated carbon catalysts are used for the synthesis of vinyl acetate from acetylene and acetic acid in the gas phase (Ohmae, T., Chemical economy and engineering review 4 (1972), 11, 46-57).

It is also known that the initial activity and the lifetime of these catalysts depend strongly on the type of activated carbon used as a catalyst support. (U.S. Patent 2,485,044)

However, which characteristic parameters of the activated carbon make it suitable as a carrier material for the vinyl acetate catalyst is not exactly known.

Hints on the influence of surface chemical groups of the carrier activated carbon are in Siedlewski et al. (Przemysl chemiczny 54, 12, 694-697, (1975)).

The SU-PS 276919 describes a zinc acetate activated carbon catalyst for the production of vinyl acetate with greatly increased catalytic activity, which is used, for example, in a fluidized bed process. The proposed as a catalyst support activated carbon has a pore volume of preferably 0,06cm ³ / cm ³ in the pore radius range of 100-1 000Ä.

Despite the high activity, the use of these catalysts is in practice associated with disadvantages. When used in fixed bed reactors, these catalysts place high demands on the removal of the heat of reaction from the catalyst bed, which can be achieved only to a certain degree in an economical manner. Another disadvantage is the short life of these catalysts.

Object of the invention

The aim of the invention is to extend the life of zinc acetate activated carbon catalysts and increase the space-time yield of vinyl acetate with simultaneous reduction of the specific catalyst consumption by the use of new zinc acetate activated carbon catalysts in vinyl acetate synthesis and a stable driving to ensure the reactors.

Statement of the nature of the invention The technical problem of the invention

The invention has for its object to develop a process for the preparation of zinc acetate activated carbon catalysts with improved service life, by suitable zinc acetate activated carbon catalysts vinyl acetate, preferably acetylene and acetic acid, in a fixed bed in a simple and economical manner without additional apparatus Effort can be made with increasing the space-time yield and simultaneous reduction in the catalyst consumption.

Features of the invention

The technical object of the invention is achieved in that specially selected carrier activated carbons are used for the preparation of zinc acetate activated carbon catalysts for vinyl acetate synthesis.

The carrier activated carbons according to the invention have an internal surface area greater than 1,000 m ² / g, preferably from 1,250 to 1,700 m ² / g (determined by the BET method), a mesopore volume (40 Å <r _p <500 Å) greater than 0.1 cm ³ / g,

preferably from 0.1 to 0.25 cm ³ / g, a macro pore volume (500 Å <r _p <10000Ä) of greater than 0.15 cm ³ / g, preferably from 0.15 to 0.50 cm ³ / g and a gas chromatographically determined Retention volume for benzene greater than 0.3 l / g.

The retention volume of the benzene to the carrier activated carbon was determined by gas chromatography using the method of frontal technique at 220 ⁰ C. The values obtained were based on O ⁰ C and 760 Torr.

Meso- and macropore volumes are determined by the commonly used method of high-pressure mercury porosimetry.

The catalysts prepared by the process according to the invention are obtained by impregnation of the above-characterized activated carbon with aqueous zinc acetate solution according to the conventional preparation processes in a known manner.

The catalyst of the invention has a 50% increased lifetime. When using this catalyst, the specific catalyst consumption is lowered by the corresponding value. At the same time, the reduction in the frequency of the contact change reduces the consequent downtimes of the reactors. In addition to an increase in the average space-time yield or the reactor capacity, this leads to a stable operation of the system.

The use of the catalyst according to the invention is preferably carried out in all known production processes of vinyl acetate from acetylene and acetic acid in a fixed bed reactor.

The invention will be explained in more detail by the following examples.

embodiments example 1

From the activated carbon A, a zinc acetate activated carbon catalyst with a zinc content of 12% by weight of Zn was prepared by impregnation with aqueous zinc acetate solution

 The activated carbon A has the following parameters:

inner surface: 1340m ² / g

Volume of mesopores: 0.07cm ³ / g

Volume of macropores: 0.32cm ³ / g

Retention volume of benzene: 0.7 l / g

The catalytic testing of the zinc acetate activated carbon catalyst was carried out in a laboratory reactor, which consists of a V2A steel tube with 25mm inner diameter and is tempered from the outside by a silicone oil bath. The temperature measurement in the catalyst layer was carried out by an axially displaceable Fe-Ko thermocouple in the center of the reactor tube. The activity test was carried out at an oil bath temperature of 200 ° C over a period of 150 hours. The volume of the built-in catalyst is 200 ml.

The molar initial ratio of acetylene: acetic acid is 4. The catalyst loading is 500V / V · h. The acetic acid conversion was determined by means of a gas chromatographic analysis. As a measure of the aging of the catalyst, the decrease in acetic acid conversion is used after a period of 150 hours.

The activated carbon A catalyst achieved an initial acetic acid conversion of 40%; this corresponds to an initial space-time yield of 154 g vinyl acetate / 1 catalyst · h. This conversion value will be used as a standard value and defined as a reference value with a value of 1. After 150 hours, the catalyst still achieved a relative acetic acid conversion of 0.67.

Example 2

From the activated carbon B, a zinc acetate activated carbon catalyst was prepared in the same way as in Example 1. The activated carbon B has the following properties:

inner surface: 750m ² / g

Volume of mesopores: 0.1 cm ³ / g

Volume of macropores: 0.1 cm ³ / g

Retention volume of benzene: 0.084 l / g

The testing of the catalyst was carried out analogously to Example 1.

The relative initial conversion of acetic acid was 0.55; After 150 hours, a relative conversion of 0.36 was reached.

Example 3 (according to the invention)

An activated carbon C catalyst achieved an initial relative acetic acid conversion of 1.1; after 150 hours the relative conversion was still 0.83.

The activated carbon C has the following properties:

Surface: 1400m ² / g

Volume of mesopores: 0.13cm ³ / g

Volume of macropores: 0.27cm ³ / g

Retention volume of benzene: 0.38 l / g

Example 4

A catalyst prepared from activated carbon D achieved a relative initial acetic acid conversion of 0.33; after hours running time still a value of 0.21 was obtained. The activated carbon D is characterized by the following parameters:

Surface: 350m ² / g

Mesopore volume: 0.13cm ³ / g

Macro pore volume: 0.19cm ³ / g

Retention volume of benzene: 0.09 l / g

Example 5 (according to the invention)

Activated carbon E gave a catalyst with a relative initial conversion of 1.05 and a relative acetic acid conversion of 0.86 after 150 hours.

The activated carbon E has the following properties:

Surface: 1580m ² / g

Volume of mesopores; 0.22cm ³ / g

Volume of macropores: 0.48cm ³ / g

Retention volume of benzene: 0.36 l / g

Claims (1)

Invention claim: Process for the preparation of zinc acetate activated carbon catalysts for the synthesis of vinyl acetate by impregnating activated carbons with zinc acetate solutions, characterized in that the activated carbons have an internal surface area greater than 1 000 m ² / g, preferably from 1 250 to 1700 m ² / g, a pore volume of the mesopores greater than 0.1 cm ³ / g, preferably from 0.1 to 0.25 cm ³ / g, a pore volume of the macropores greater than 0.15 cm ³ / g, preferably from 0.15 to 0, 5 cm ³ / g, and a gas chromatographically determined retention volume for benzene greater than 0.3l / g.