DE3936744A1 - Catalytic oxidative decomposition of halogenated organic cpds. - by passing cpd. mixed with oxygen and gas which burns in oxygen through fluidised bed of catalyst - Google Patents

Abstract

Process for the catalytic oxidative decompsn of halogenated organic cpds (I) comprises passing a mixt contg (I), oxygen and a gas or vapour (II) which burns exothermically with oxygen through a catalytic fluidised bed. Reaction is carried out at 400-800 deg C using a supported noble metal catalyst and the gas mixt is preheated to not above 100 deg C; (II) is a 1-20C hydrocarbon, and the gas mixt contains at least 1000 (pref 2000-20,000) ppm (II); concn of (I) in the mixt (waste gas is 10-10,000 (pref 100-5000) ppm; residence time in the fluid bed is 0.1-1 sec; part of the heat energy released is removed from the fluid bed; the solids removed in the stream of gas from the process are sepd from the gas and partly or completely returned to the fluid bed if required; in continuous operation, some of the catalyst is removed from the fluid bed and replaced with a corresp amt of fresh catalyst. USE/ADVANTAGE - The process is useful for purifying waste gas from vinyl chloride synthesis and liq residues from epichlorhydrin synthesis (claimed). The invention provides an opt continuous process for the purification of gas mixts contg high concns of noxious substances, wtihout thermal overload or inactivation of catalyst.

Description

The invention relates to a method for catalyzing tables oxidative decomposition of halogenated orga African compounds and the application of the Invention according to the procedure.

The emission of organic compounds and esp special halogenated organic compounds for example wise in industrial exhaust gases, e.g. B. in the exhaust gases of the Vinyl chloride synthesis, is for environmental reasons problematic.

For the decomposition of exhaust gases, the halogenated organi contain cal compounds, it is known these exhaust gases heat to high temperatures, d. H. on temperatures up to 1500 ° C, making it a thermal oxidative To cause decomposition. In addition to such uneconomical thermal processes are also catalytic Process for the decomposition of halogenated organic Connections known. This is usually halogenated exhaust gas containing organic compounds to about 300 ° C. heated and passed through a fixed catalytic bed. It is easy to do at high concentrations thermal overload of the catalysts used.

The object of the present invention was to provide a ver improved process for catalytic oxidative decomposition halogenated organic compounds.  

This object is achieved by the method according to the invention solved. The inventive method for catalyzing tables oxidative decomposition of halogenated organi connections is characterized in that one Gas mixture, which is a halogenated organic compound dung, oxygen and an oxygen exothermic burn contains gas or steam to decompose the halo Generated organic compound by a catalytic Fluidized bed conducts.

All known catalysts known for the oxidative decomposition of halogenated organic compounds can be used as catalysts. A variety of metals, in particular noble metals, such as platinum, palladium, ruthenium or rhodium and metal oxides, in pure form or as a mixture can be used as a full contact catalyst or, preferably, as a supported catalyst with known ceramic mixed carrier material. Is well suited, e.g. B. α-alumina, γ-alumina, silicon dioxide or aluminosilicate. Preference is given to using noble metal catalysts, in particular as a noble metal carrier catalyst. Preferred supported catalysts contain platinum on γ-aluminum oxide, silicon dioxide, corderite, zeolite or aluminosilicate as the support. The specific surface area of the carrier materials can be in the range from 1 m ² / g to 500 m ² / g. the noble metal content can be in the range from 0.01 to 1% by weight, based on the total weight of the supported catalyst, and is advantageously about 0.1 to 0.5% by weight.

The catalytically active component, especially one Precious metal such as platinum, can be in a homogeneous distribution or inhomogeneous distribution on the carrier material gen. The supported catalysts can, for. B. in granulated Form or spherical. Preferably used supported catalysts in the process according to the invention Ball shape.  

The particle size of the catalysts or the carrier Catalysts must be chosen so that the one to be cleaned Gas flow still swirling the particles with formation formation of a fluidized bed. In selecting the appropriate particle size must be the volume flow of the cleaning gas, the shape (air resistance) of the particles, the spatial shape of the reactor, the specific weight of the Supported catalyst u. a. Influencing factors take into account who the. If desired, the person skilled in the art can use orientie trials for a special application determine the optimal particle size.

Catalyst particles or supported catalyst particles in a size of up to 2 mm, preferably from 0.1 to 1 mm are generally very suitable.

The organic compound to be decomposed can it is a pure substance or a mixture of several act halogenated organic compounds. As kata Halogenated organic compound to be decomposed lytically come partially or fully halogenated aliphatic, aroma table or araliphatic compounds in question, esp special saturated or unsaturated, partially or fully halo branched, branched or unbranched aliphatic Koh Hydrogen oils. This is particularly suitable moderate process for the catalytic decomposition of alipha tables, partially or fully halogenated hydrocarbons with 1 to 12 carbon atoms. Halogen preferably means chlorine. The method according to the invention is extremely suitable for the decomposition of exhaust gases, which are chloromethane, dichlor methane, chloroform, ethyl chloride, ethylene dichloride, vinyl contain chloride, propyl chloride or butyl chloride. Of course Lich you can also mixtures of halogenated organic Decompose compounds in the process according to the invention.

The term "burning exothermic with oxygen Gas or steam "includes halogen-free, especially alipha table hydrocarbons with 1 to 20 carbon atoms. Prefers  is added in the context of the present invention Normal conditions of gaseous substances continue to be such Substances that have a vapor pressure under normal conditions of more than 10 mbar, for example aliphatic Hydrocarbons with 1 to 8 carbon atoms. Preferably around this term summarizes short-chain aliphatic hydrocarbons substances with 1 to 6 carbon atoms, especially methane, ethane, Ethylene, propane, propene, butane, pentane and hexane.

It goes without saying that the exhaust gas next to one or more halogenated organic compounds and the gas that burns exothermically with oxygen is also acidic must contain substance. Appropriately, the sour substance to be present in an amount that is stoichiometric for complete oxidation of the halogenated compound and the exothermic burning gas is necessary. A Limitation on the maximum content of oxygen there is not any. Particularly preferred exhaust gas in the fiction In addition to the halogenated orga African compound and the exothermic ver with oxygen burning gas as the remaining component air.

The halogenated organic compound or the Ge Mixture of such compounds can be in a concentration from 10 to 10,000 ppm, preferably in a concentration tion of 100 to 5000 ppm, contained in the exhaust gas. In In a preferred embodiment, this is with oxygen exothermic gas or vapor in one concent tration of at least 1000 ppm in the gas mixture. That with Oxygen can burn exothermic gas or steam in a concentration of up to 20,000 ppm, preferably be contained in the exhaust gas from 2000 to 20,000 ppm.

In many exhaust gases, for example exhaust gases from the Vinyl chloride synthesis, are halogen-free, with oxygen contain exothermic gases. Depending on the existing Concentration does not need to be exothermic with oxygen to be added to burning gases. If desired  halogenated organic compounds holding exhaust gas that burns exothermic with oxygen Gas or steam in such an amount that exothermic oxygen-burning gas in a total concentration tration from 1000 to 20,000 ppm, preferably from 2000 to 20,000 ppm is contained in the exhaust gas.

The catalytic decomposition of the halogenated organi connections in the process according to the invention at temperatures of 400 to 800 ° C in the fluidized bed.

In many cases, the exhaust gases need before entering in the fluidized bed at most to a moderately high temperature ren, for example heated to no more than 100 ° C. to become. Often, for example with exhaust gases from the vinyl chloride production, preheating to only 40 ° C is not necessary agile. If desired, the exhaust gas to be cleaned can can also be preheated to higher temperatures. The for any preheating that may be necessary Energy can be transferred through suitable heat exchangers Heat dissipation from the catalytic fluidized bed and / or cause the cleaned exhaust gas, obtained from the process be or by preheating using a burner, heat jet lung or the like from external sources.

In the method according to the invention, the feed ex ternal energy only necessary to the catalytic vortex layer on the light off temperature of at least 150 ° C bring to. The catalyst material and / or heat up the gas mixture to be decomposed accordingly. The supply of external energy is not necessary if the energy content of the exhaust gases to maintain the Minimum temperature in the catalytic fluidized bed of about 400 ° C is sufficient.

The method according to the invention can Normal pressure and overpressure up to 1 MPa  the. Technically simple and therefore preferred Carried out at normal pressure (ambient pressure).

The dwell time of the exhaust gas to be cleaned in the fluidized catalytic bed can be less than 0.1 seconds be. The residence time is preferably between 0.1 and 1 second.

Advantageously, a part is carried out, for example way up to 50% of the implementation of the invention According to the process released thermal energy from the Fluidized bed.

By installing suitable devices, e.g. B. from Cooling jackets or heat exchangers in the fluidized bed react You can ensure effective heat dissipation and increase the throughput of exhaust gas to be cleaned.

It is known that there are different fluidized beds types there. A distinction is made between fluidized beds with moderate Bed movement and low solids discharge (in the following Called fluid bed), furthermore the strongly expanded vertebrae layer with strong solid movement and predominant or complete solids discharge ("flash reactor") as well as the zir cumulating fluidized bed with complete solids carry and return. The procedure of the present Er invention is preferably operated as a fluidized bed. With the cleaned exhaust gas discharged solids, here it is more or less crushed kata lysator material, are advantageously in a solid material separator, for example a cyclone from the exhaust gas separated. You can now see the separated solids return all or part of the fluidized bed. The not circulated, but removed Part of the separated solid can be recovered of the metal, especially precious metal content carry out appropriate processing. One can now ent  speaking of the amount of solid matter discharged fresh catalyst or supported catalyst in the circle bring in the run.

The inventive method for catalytic oxidative decomposition of halogenated organic ver Bonds can also be done in a continuous manner be performed. This variant of the invention Process for the catalytic oxidative decomposition of Halogenated organic compounds are characterized by this records that one in a continuous procedure Gas mixture, which is the halogenated organic compound dung, oxygen and an oxygen exothermic burn contains a gas or a vapor, through a catalyze table fluidized bed conducts, where one sentence or continuously part of the catalyst from the vortex ejected layer and correspondingly from the vortex layer of fresh catalyst discharged into the layer Introduces fluidized bed.

This discharge from the fluidized bed or on can bring into the fluidized bed by separate removal tion facilities or feed facilities happen. Appropriately, however, one proceeds that one Volume flow of the exhaust gas regulated so that in batches or preferably continuously with the catalyst material cleaned exhaust gas is discharged from the fluidized bed and separated from the exhaust gas in a solids separator becomes. The fluidized bed is then operated temporarily or constantly as an expanded fluidized bed. To the amount of Catalyst material in the fluidized bed essentially keeping the fluidized bed becomes a catalyst mate rial supplied in an amount equal to the amount discharged corresponds. It is then returned to the fluidized bed part of the discharged and separated solid or the entire separated solid by fresh Catalyst supplements or fresh supported catalyst puts.  

The catalytic process described above oxidative decomposition of halogenated organic Connections that are also operated continuously can see a one-step treatment of the exhaust gases in a catalytic fluidized bed, preferably with subsequent solid separation from the exhaust gas and solid material return. This will already work very high degrees of sales (<99%) achieved.

If desired, you can still change the degree of sales increase further. For this you can, for example, part return the exhaust gas to the fluidized catalytic bed. One can also look at the catalytic vortex, for example layer another preferably catalytic treatment Connect the level. In particular, the gas can be in one catalytic fixed bed can be treated further. As Kataly come the precious metal or described above Metal oxide catalysts as full contact or support catalyst analyzers in question. This can be bulk goods per such as granules, pellets or balls, or to carry in Act monolithic.

To separate the finest constituents of the exhaust gas a fine dust separation can be provided.

In addition to HCl, CO ₂ and optionally air, the exhaust gases purified by the process according to the invention contain only very small amounts of halogenated organic hydrocarbons. Even with one-step procedure, these are often no longer detectable by gas chromatography. The HCl content can be separated from the exhaust gas using customary methods. For example, you can pass the exhaust gas over solid adsorbent for HCl and recover the adsorbed HCl. It is also possible to absorb HCl, e.g. B. with solvents, such as water, wash out of the exhaust gas. Finally, chemisorption with bases, for example, is also possible. The exhaust gas obtained is then free of pollutants.

The method according to the invention is suitable, as before already described, very good for cleaning of exhaust gases from a wide variety of industrial processes. It is particularly suitable for cleaning of exhaust gases from vinyl chloride synthesis and liquid back of epichlorohydrin synthesis. Another counter State of the invention is thus the application of the inventions process according to the invention in the purification of the exhaust gases vinyl chloride synthesis and liquid residues from Epi chlorohydrin synthesis.

Exhaust gases of this type also contain vinyl chloride other halogenated organic compounds such as methylene chloride and ethylene chloride that are used in the application of the he inventive method are also decomposed. Oxi The hydrocarbons that are also present are also dated substances methane, ethylene and ethane as well as carbon monoxide.

The inventive method has surprising Advantages: Continuous process management is possible Lich, the exhaust gas to be cleaned often only has to be moderate Temperatures, for example up to 60 ° C, are preheated the, the exhaust gas to be cleaned, e.g. B. Exhaust of vinyl chloride Synthesis, can have high pollutant concentration without that the thermal overload of the catalysts, ins particular of the precious metal catalysts would be feared so that any dilution of the harmful gas is often not necessary is. Although you have exhaust gases with higher pollutants can use concentrations, the degree of sales is very high high and accordingly the residual levels of pollutants very low.

Here are the last two effects of the method according to the invention, namely the possibility ability to work at high pollutant concentrations  and still achieve a high level of sales, completely unexpected and unpredictable. It is part of Knowledge of the skilled person that catalyzed chemical conversion tongues also in a catalytic fluidized bed can be performed. As is known, however, is falling the degree of conversion in the catalytic fluidized bed. Expectation according to the degree of sales should of course decrease all the more, if a catalytic to be implemented, for example, ab building compound in a mixture with another, even if catalytically degradable component, namely one gas reacting exothermically with Sauerertof is present. Just however, this is the case in the method according to the invention. This effect of the inventive method that in to oxidatively remove a catalytic fluidized bed building halogenated organic compound especially in ge mix with one that is also oxidatively degradable, with Oxygen exothermic gas with a particularly high Degree of turnover can be decomposed is completely surprising and also not to explain. The application of the kataly table fluidized bed in the decomposition of such gas Mixtures are therefore not obvious and are out of date beneficial effects.

The following examples are intended to illustrate the invention Explain the procedure further without reducing its scope to restrict.

Example 1: Decomposition of dichloromethane in one catalytic fluidized bed 1.1 Preparation of the supported catalyst used

Commercial α-Al ₂ O ₂ carrier material (from Kali-Chemie, carrier "GS 1039") was used as the carrier material. The carrier material had a specific surface area of 90 m ² / g, a pore volume of 484 mm ³ / g and was used in the form of spherical granules with a particle diameter of about 0.5 to 1 mm.

The carrier material was washed with an aqueous tetra amminoplatin hydroxide solution in an impregnation drum in impregnated. After taking up the impregnation solution the carrier material was dried on the supported catalyst and calcined. The finished supported catalyst contained 0.2 wt% platinum.

1.2 Oxidative decomposition of dichloromethane in a ka analytical fluidized bed using the according Example 1.1 supported catalyst prepared

The device used consisted of heat exchanger for electrical preheating of the used pollutant-containing gas mixture, one with gas supply and gas discharge pipe reactor and a solid fabric separator. The jacket of the cylindrical reactor was designed as a double jacket and was used for indirect heating or cooling of the inner reactor jacket. The Reactor had an inner diameter of 50 mm and one Volume of 500 ml.

The reactor was filled with 300 ml (resting volume) of the Example 1.1 obtained supported catalyst filled. That too Purifying gas mixture was air with a content of 12,000 ppm ethylene and 600 ppm dichloromethane.

The supported catalyst material was first brought to the light-off temperature (about 150 ° C.). After setting the equilibrium, the gas mixture to be cleaned, which had been preheated to about 40 ° C. in the heat exchanger before being passed into the reactor, was passed through the catalytic fluidized bed which formed at a space velocity of about 30,000 h ^-1 . About a third of the heat energy released was dissipated via the coolable jacket of the reactor and used to preheat the exhaust gas. The temperature of the fluidized bed was about 434 ° C. The exhaust gas leaving the reactor was fed to a solids separator, in which small amounts of very fine dust was separated off. The gas chromatographic examination (separation conditions: column: silica capillary column; temperature program: 50 ° C isothermal; column length: 50 m; detector: FID) of the exhaust gas leaving the reactor showed that the halogenated organic compound (CH ₂ Cl ₂ ) was not gas chromatographic was more detectable. The degree of conversion of ethylene was 99.13%.

Example 2: Decomposition of vinyl chloride in the catalyze table fluidized bed

In the device described under 1.2, again using 300 ml (resting volume) of the supported catalyst described under 1.1, a gas mixture containing air and 13,500 ppm ethene and 300 ppm vinyl chloride was treated according to the invention. The preheating temperature was 40 ° C, the space velocity 33 333 h ^-1 and the temperature in the fluidized bed after equilibrium was about 532 ° C. As the gas chromatographic examination of the gas leaving the reactor proved, the chlorinated hydrocarbon compound was completely converted. More than 99.5% of the ethene was mined.

Example 3: Decomposition of butyl chloride in the catalytic fluidized bed

As described in Example 1, air containing 6000 ppm ethylene and 750 ppm butyl chloride was treated by the process according to the invention. The preheating temperature was 260 ° C, the space velocity 33 333 h ^-1 , the fluidized bed temperature 429 ° C. The gas mixture leaving the reactor was examined by gas chromatography. The chlorinated hydrocarbon compound was no longer detectable, the ethylene was broken down by more than 99%.

Example 4: Decomposition of chlorinated liquid residue epichlorohydrin synthesis in the catalytic fluidized bed

As described in Example 1, air containing 6000 ppm ethene, 750 ppm n-hexane and 750 ppm chlorinated hydrocarbons (liquid residues from the production of epichlorohydrin) was treated according to the invention. The preheating temperature was 130 ° C, the space velocity 26 670 h ^-1 and the fluidized bed temperature 510 ° C. Gas chromatographic examination of the gas mixture leaving the reactor showed that the chlorinated compounds had been completely implemented. The total content of hexane and ethene was determined to be 6 ppm in total.

Claims (12)

1. A process for the catalytic oxidative decomposition of halogenated organic compounds, characterized in that a gas mixture which contains a halogenated organic compound, oxygen and a gas or steam which burns exothermically with oxygen is passed through a catalytic fluidized bed to decompose the halogenated organic compound. 2. The method according to claim 1, characterized in that that as a catalyst, a noble metal supported catalyst used. 3. The method according to claim 1 or 2, characterized records that the oxidative decomposition in the cataly table fluidized bed at temperatures between 400 and 800 ° C. 4. The method according to any one of claims 1 to 3, because characterized in that the gas mixture before the one no longer lead into the catalytic fluidized bed than about 100 ° C preheated. 5. The method according to any one of claims 1 to 4, characterized in that the exothermic with oxygen burning gas or steam containing a hydrocarbon 1 to 20 carbon atoms. 6. The method according to claim 5, characterized in that the hydrocarbon in a concentration of min at least 1000 ppm, preferably in a concentration of 2000 ppm to 20 000 ppm is contained in the mixture.   7. The method according to any one of the preceding claims, characterized in that the halogenated organic Compound in a concentration of 10 ppm to 10,000 ppm, preferably 100 ppm to 5000 ppm in the exhaust gas is included. 8. The method according to any one of the preceding claims, characterized in that the residence time of the mixture in the catalytic fluidized bed between about 0.1 sec and is 1 sec. 9. The method according to any one of the preceding claims, characterized in that one part of the free dissipates the thermal energy from the fluidized bed. 10. Method according to one of the preceding Claims, characterized in that one from the vertebrae layer of solids removed from the exhaust gas with the exhaust gas flow separated and, if desired, partially or completely returns to the fluidized bed. 11. Method according to one of the preceding Claims, characterized in that one in continuous Licher procedure part of the catalyst from the Fluid bed removes and a corresponding amount of introduces fresh supported catalyst into the fluidized bed. 12. Application of the method according to one of the claims 1 to 11 for cleaning the exhaust gases from the vinyl chloride Synthesis and liquid residues from the epichlorohydrin Synthesis.