DK151007B - FLUIDIZABLE POWDER-SHAPED CONTACT MASS USED BY OXYHALOGENATION OF IN-GAS PHASE CARBON MONOXIDE AND CARBON HYDROIDES - Google Patents

Description

151007

The present invention relates to a fluidizable powder contact mass for use in carbon monoxide gas phase oxygenation and the hydrocarbons mentioned in the preamble of claim 1 containing a fluidizable oxyhalogenation catalyst.

It is known e.g. preparing 1,2-dichloroethane by gas phase oxychlorination in the presence of a fluidized catalyst bed which is generally based on copper chlorides and oxychlorides deposited on a support such as activated alumina, silica, magnesia, silica and diatomaceous earth.

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Since the oxyhalogenation reactions of halogenated or non-halogenated hydrocarbons are highly exothermic, the process using flulized bed has, theoretically, the advantage of continuously ensuring perfect isothermia in the reaction zone and a very good contact between the various reactants - halogenated or not. -rough allogeneic hydrocarbons, hydrogen or ammonium halides, and the gas containing oxygen, and this thanks to the intense stirring of the catalyst which is kept in a fluidized state. Thus, it is the homogeneous structure of the fluidized catalyst bed that is a major factor enabling a good selectivity with respect to the desired product and, consequently, high yields.

In the continuous process performed on an industrial scale, i.e. however, with large volumes of fluidized catalyst bed, certain conditions interfere with the operation of the reactor, and in particular the hydrodynamics of the bed, making the process unusable. One has e.g. observed that the preferred passages of gaseous reactants through the bed cause a decrease in the thermal exchange coefficient near the walls, and sometimes even a decrease in the isotherm of the bed and its reactivity. Formation of very large bubbles of the reacting gases or motionless catalyst zones in the fluidized bed has been found, which also decreases the reactivity of the bed and can interfere with the operation of the solid-state gas separators, which are usually disposed after the fluidized bed in the reactor. , as well as the return or recycle means, as well as the feed and take-out means for the catalyst particles. A further tendency has been observed for some of the catalyst particles, especially the finest, to adhere to one another or to the metal walls of the reactor and the adjacent areas, thus resulting in a catalyst loss, a permanent change in the granulometry distribution of the catalyst particles, and a decrease in the heat exchange coefficient. Thus, it is extremely difficult to maintain a stable granulometry distribution during operation. In particular, the catalyst losses, which are particularly pronounced for the finest particles, by entraining them from the bed to the solid-gas separation means will continuously modify the granulometry distribution. The decrease in the amount of fluid particles in the form of fine particles more or less quickly results in a destruction of the fluidization which from time to time can completely disrupt the operation of the process using fluidized bed.

Another cause of the catalyst losses is wear and crushing of the particles due to shock between them and contact with the walls. This phenomenon, which can be called attrition, also causes a evolution in the particle size of the catalyst. On the one hand, the degree of wear may vary depending on the granulometry section, and on the other hand, the wear products are either ultra-fine particles that disappear from the bed and cannot be recycled, or sufficiently large particles to remain in the bed, thus enriching certain granulometry sections. Thus, according to the circumstances, the attrition results in either a prohibitive loss of solids or an enrichment of fine particles, which may result in an ever-expanding expansion of the fluidized bed, a disturbance in the function of the solid-gas separators, an adhesion or. agglomeration of fine particles and / or a decrease in the heat exchange coefficient at the walls, which necessitates lowering the feed to the reactor and thereby its productivity.

In order to increase the productivity of fluidized bed reactors, it has been proposed to raise the gas flow rates and pressure, and consequently the heat exchange coefficient. In order to maintain the same useful cross-section of the gas passage, it is necessary to increase the height of the reactor, and thus use a bed height greater than that which gives the best chemical yield of the desired product.

Furthermore, the excess portion of the bed is the site of parasite reaction, such as a post-combustion to form CC 2 and CO, and a formation of post-chlorinated and oxygenated hydrocarbons which significantly lowers the yield of the useful products. Thus, a zone of higher temperature can be observed in the lower part of the fluidized bed in the vicinity of the gaseous reactant distributor, especially when operated under pressure or with oxygen-enriched gas with air. This phenomenon poses a risk to the safety of the process and diminishes the selectivity of the useful reaction product.

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All of the above-described phenomena associated with the use of fluidized bed are extremely detrimental to the good operation of an industrial plant, e.g. for the preparation of 1,2-dichloroethane, especially obtained by selective oxychlorination of ethylene.

The object of the present invention is, to a large extent or completely, to remedy the above-mentioned disadvantages in a very simple and effective manner, in other words enabling a considerable reduction in attrition, suppressing the adhesion of fine catalyst particles, greatly reducing the consumption of these fine particles, reduce the temperature difference between the lower and upper part of the bed, and adjust the reactivity of the catalyst contact mass so that the height of the bed corresponds to the best yield, especially with regard to 1,2-dichloroethane in the case of gas phase oxychlorination of ethylene.

This is achieved by using the fluidizable powdered contact mass according to the invention, which is characterized by the characteristic part of claim 1.

Among the catalytically and chemically inert substances which can be used as a diluent, but in no case as a carrier for the catalyst, are in particular microspheres of glass or silicon dioxide, tk-alumina, and preferably quartz sand found in the natural state, and if the particle size granulometry distribution is adapted to the requirements of fluidisation.

The granulometry distribution of the catalyst itself on the one hand and of the catalytically and chemically inert substance on the other hand is chosen such that the diameter and particle size distribution of the mixture are favorable for good fluidization and are 20-200 µm with an average diameter of 40-90 ^ um.

It has been found that in order to obtain the above advantages, it is preferable that the largest particles in the mixture to be fluid consist, for the most part, of the catalyst, while the finer particles for the majority "consist of the inert solid, especially quartz sand, with which excellent results have been obtained.

The fluidizable contact mass of the invention is used as indicated above in an oxyhalogenation reaction in the gas phase, preferably oxychlorination of carbon monoxide, saturated or unsaturated aliphatic hydrocarbons having 1-20 carbons, cycloaliphatic hydrocarbons having up to 12 carbons and aromatic hydrocarbons having up to 4 condensed rings bromo-substituted and especially chloro-substituted derivatives thereof, but especially of ethylene.

As gas containing oxygen, air or oxygen-enriched air is most often used, and as a carrier gas for halogen, preferably chlorine or bromine, a hydrogen and / or ammonium halide can be used.

If desired, in addition to the free chlorine formed in situ by the reaction between oxygen and hydrogen and / or ammonium halide, additional free chlorine can be introduced into the reactor together with the carbon monoxide or hydrocarbon.

The general conditions for the oxyhalogenation reaction are, for the temperature, usually 170-500 ° C and for the pressure 1-20 absolute bar. The molar ratio of O 2 / hydrocarbon and / or halogenated hydrocarbon and / or carbon monoxide / hydrogen and / or ammonium halide may vary within very wide ranges according to the desired result. Thus, if one wishes to be selective with respect to a specific compound, reactant ratios approaching the stoichiometric approach are employed, whereas if one seeks to obtain a mixture of halogenated hydrocarbons, relatively smaller amounts of the carbonaceous starting materials are used.

In general, any fluidizable oxyhalogenation catalyst can be used in the dilution with the inert solid to obtain the fluidizable powdered contact masses of the invention. However, if an oxychlorination of ethylene is preferred, catalysts consisting essentially of a carrier of activated alumina having a specific surface area of 150-400 m / g, in particular 200-350 m / g, upon which a copper salt is deposited 6 151007 of a mineral acid, preferably copper (II) chloride in amounts of 3-10 wt. copper relative to the finished catalyst.

Of the following examples, Examples 1 and 2 illustrate the invention.

EXAMPLE 1

A gas phase oxychlorination of ethylene to 1,2-dichloroethane is carried out in a cylindrical reactor with a diameter of 120 mm and a height of 7 m. A heat exchanger extends 4 m up from the bottom of the reactor and cyclones with return pipes continuously recycle the fluidized particles of contact mass entrained by the reaction gases to the bottom of the bed. This fluidized bed consists of a mixture of 70% by weight. natural quartz sand particles having a mean diameter of 50 µm and 30% by weight of a catalyst consisting of activated alumina having a mean diameter

ISLAND

of 95 µm, the specific surface area of which is 300 m / g, on which 6 wt. copper in the form of CuCl2, 2 ^ 0.

The granulometry distribution of this particle mixture was 20-150 µm with a mean diameter of 63.5 µm.

The reactants HCl, ethylene and air are continuously fed in the molar ratios of O 2 / C fluidized contact mass. The temperature of the reactor was 225 ° C and the pressure was 4 absolute bar

The linear velocity of the gaseous reactants in the reactor was 20 cm / sec.

After 1,000 hours of continuous operation, the following conversion rates of ethylene to other compounds have been obtained: 1.2-dichloroethane 96.8% 1.1.2-trichloroethane 0.8% 1.1.2.2-tetrachloroethane 0.6% cis- and trans-dichloroethylene 0.2 % Trichlorethylene 0.2% CO + CO 1.2% 7 151007

Thus, the total conversion rate of ethylene is 99.8%.

After these 1,000 hours of operation, the granulometry distribution of the catalyst has practically not varied, the coefficient of heat exchange has remained constant, and no catalyst particles have stuck together, just as the wear was negligible.

Reduced catalyst losses were achieved: 0.5% by weight. per. day of continuous operation.

Comparative Example 1

Example 1 was repeated except that the fluidized bed contained only 30 kg of non-sand diluted catalyst and had a mean diameter of 63.5 µm, as was the mixture of Example 1.

After 300 hours of operation, the catalyst was severely worn and the bed had been continuously enriched with particles smaller than 40 µm, which is why the mean diameter had dropped from 63.5 to 40 µm.

The coefficient of expansion of the fluidized bed (the ratio of the fluidized height to the height of the bed at rest) is increased and the heat exchange coefficient is greatly decreased.

The conversion rates of ethylene to other compounds were as follows: 1.2- dichloroethane 89% CO + CO2 7% 1.1.2- trichloroethane 1.35% 1.1.2.2- tetrachloroethane 0.75% cis- and trans-dichloroethylene 0.4% trichloroethylene 0, 5%

Thus, the total conversion rate of ethylene was 99%.

The catalyst losses after 300 hours of operation were 15 kg, corresponding to 4% by weight. per. day, which is a significant loss.

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Operation had to be interrupted due to the rapid change of the granulometry, which caused numerous disruptions due to the significant enrichment with catalyst particles, with sizes of less than 40 µm.

EXAMPLE 2

An oxychlorination of ethylene to 1,2-dichloroethane is carried out in an industrial scale reactor with a diameter of 2 m and a height of 15 m.

The fluidizable contact mass consisted of 20 t of the mixture of catalytically and chemically inert sand and catalyst described in Example 1

Cyclones with return tubes continuously recycle the entrained particles.

The reactants C 2 H 2, HCl and oxygen (in the form of air) at a molar ratio 1/2 / 0.65 were introduced at the bottom of the reactor through the fluidized bed. The linear velocity of the gaseous reactants was 30 cm / sec.

The temperature of the reactor was 230 ° C and the pressure was 4.5 absolute bar. The conversion rates of ethylene to other compounds were as follows: 1.2- dichloroethane 97.0% 1.1.2- trichloroethane 0.3% 1.1.2.2- tetrachloroethane 0.1% trichloroethylene 0.15% cis- and trans-dichloroethylene 0.15% CO + CO 2 0.93%

Thus, the total conversion rate of ethylene was 98.63%.

After 8,000 hours of continuous operation, the granulometry, fluid coefficient expansion coefficient, and heat exchange coefficient had practically not changed.

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Catalyst wear was negligible and the catalyst loss was reduced to the order of 0.4% by weight. per. day.

The above examples clearly illustrate the significant advantages of using the present fluidizable contact mass, the most significant of which are the following: a) a significant improvement in the catalyst economy over the composition of the known fluidizable contact mass and the consumption of continuous operation; b) Stabilization of the granulometry, thereby avoiding numerous disadvantages such as clogging the cyclones and sticking the catalyst which can be catastrophic; c) Improving the yield of the main reaction.

Claims (3)

15100 / 1. Fluidizable powder contact mass for use in gas-phase oxyhalogenation of carbon monoxide, aliphatic hydrocarbons of 1-20 carbons, cycloaliphatic hydrocarbons of up to 12 carbons and aromatic hydrocarbons of up to 4 condensed benzene rings, and bromine substituted and halo substituted halogenated derivatives , characterized in that it consists essentially of a mixture of 5-50% by weight particles of said catalyst and 95-50% by weight particles of at least one catalytic and chemically inert solid selected from microglass balls, JL alumina, quartz sand and / or microspheres of silica acting as a diluent and not as a carrier for the catalyst, and that the particle size of the mixture is 20-200 µm with an average diameter of 40-90 µm. Fluidizable contact mass according to claim 1, characterized in that the catalytically and chemically inert material is quartz sand. Fluidizable contact mass according to claim 1 or 2, characterized in that the coarsest particles in the mixture consist predominantly of catalyst particles, while the finer particles consist predominantly of the catalytically and chemically inert solid.