Catalytic treatment system exhaust gas to reduce emissions of volatile chemicals

 

(57) Abstract:

The invention can be used for processing the exhaust gas to reduce emissions of volatile chemicals. Adjustable quantity of the combustible fluid is dispersed in the stream of exhaust gas, simultaneously oxidize combustible fluid environment and organic contaminants on the catalyst, which contains at least one compound selected from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, silicon dioxide-aluminum oxide, zirconium dioxide and aluminum oxide. The invention allows to achieve the degree of degradation of pollutants 80 - 95%. 10 C.p. f-crystals, 1 Il.

The invention relates to catalytic systems for the processing of exhaust gas to reduce emissions of volatile chemicals. More specifically, this invention relates to a device and methods for reducing emissions of carbon monoxide and volatile organic compounds in the implementation of processes involving the removal of a gas stream containing potential contaminants.

This invention provides for the treatment of exhaust gas, which comprises (A) dispersing in the flow of exhaust g of the food and the decomposition of a significant part of harmful volatile organic compounds by oxidation on the oxidation catalyst at elevated temperatures, and (C) regulation of the quantity of the combustible fluid supplied into the flow of exhaust gas in such a way as to provide sufficient reagents for catalytic oxidation in order to maintain a suitable interval the reaction temperature.

Some aspects of the present invention relate to methods of industrial production of organic acids, especially aromatic dibasic acids, formed from the corresponding methylsiloxanes aromatic compounds by liquid-phase oxidation of methyl groups in contact with the source of oxygen, such as compressed air, in the presence of a catalytic oxidation system containing one or more compounds which are galoidoproizvodnykh. United processing system according to this invention are preferably used to reduce emissions of carbon monoxide and volatile organic compounds in the implementation processes for aromatic acids by liquid-phase oxidation.

In accordance with the present invention methods usually lead to the attainment of the degree of decomposition of carbon monoxide in the range from about 90% to about 95% and higher degree razlozheny is atarov oxidation in accordance with this invention can lead to the achievement of the degree of decomposition of alkylhalogenide in the range from about 50% to about 85% and more.

Both thermal and catalytic incineration is widely known and used for the decomposition of harmful volatile organic compounds detected in the exhaust air and other gas streams which are obtained by the implementation of various industrial processes. These threads are formed during the implementation of the methods of preparation of organic chemicals and polymers and ways in which volatile organic solvents are used for cleaning purposes and obtirania when processing and finishing materials. While the catalytic combustion can be performed at much lower temperatures and much shorter time than thermal incineration, to create the desired elevated temperatures to obtain catalytic activity, to carry out the decomposition of harmful volatile organic compounds in various industrial processes, the required additional equipment, including a microwave and/or other heat exchangers.

In the case of any industrial application of catalytic combustion requires especially careful to choose the catalytic oxidation system suitable for volatile organic compounds, which are preferably subjected to gastroplasty. Many gas streams that must be processed, contain significant amounts of Halogens and/or halogenated compounds. However, some precious metals used in conventional catalytic combustion are subject to significant inhibition of atoms halides formed during the degradation of these compounds, and this method usually cannot be used with the use of such catalysts for these gas streams.

About the constantly growing interest in reducing pollution of the atmosphere by internal combustion engines used in automobiles and other vehicles, numerous publications about the device for the operation. Usually it is argued that the reduction of atmospheric pollution and/or the achievement of some of the regulated standard can be achieved using this described device. The achievement of significant improvements, however, may depend on the combination of the particular device and the modified motor and special fuel. Improving fuel quality usually includes the removal of fuel compounds, which are known precursors of specific pollutants, VNO issued by the U.S. patent N 5193340 (in the name of Tetsuya Kamihara, Nissan Motor Co. Ltd.) the described example of the exhaust gas system for internal combustion engines. Most diesel engines are now equipped with a filter-trap in the exhaust pipe for capturing particles and other impurities, which are emitted by a diesel engine. When the back pressure in the engine increases due to the accumulation of particles captured by the filter trap these particles are periodically burned to regenerate the filter. In the device Kamihara strainer contains an oxidation catalyst that promotes combustion of the particles collected in the filter to regenerate. Provided by needle nozzle for injection of diesel fuel into the exhaust pipe upward flow for supply of diesel fuel in the filter trap. Diesel fuel is burnt in the filter-trapped under the action of the oxidation catalyst, while the burned particles and regeneration of the filter. In the process, the amount of injected diesel fuel is adjusted upward, as the intake air entering the engine increases and decrease as the temperature of the exhaust gas increases, in order to limit or avoid heat, the pressure in the engine, due to the accumulation of particles captured by the filter trap is reduced, thereby eliminating the effect of back pressure on the engine. Unknown quantities of gaseous pollutants emitted into the atmosphere from the system during the stage of regeneration by combustion of the added diesel fuel.

Other methods of filtering combustible particles contained in the exhaust gases, and updates the filtering layer and the catalytic part is described, for example, in U.S. patent N 4322387, U.S. patent N 4359862 and U.S. patent N 4372111 in the name of Kashmir S. Kirk and Martin Alperstein, and U.S. patent N 4359863 in the name of Kashmir S. Kirk and Robert C. Burns, Texaco Inc.

An example of a device for catalytic combustion, in which the gas-permeable layer of solid particles adapted for heat exchange with a stream of gas is alternately heated by the hot stream exiting the oxidation catalyst, and is cooled by the gas in this layer, by periodically changing the direction of flow of gas passing through the layer described in U.S. patent N 2946651 in the name of Eugene J. Houdry, Oxy-Catalyst, Inc. In the process, as indicated in the patent, a sufficient quantity of diesel fuel injected into a stream of heated gas and evaporates, and then ispolzuemyi the catalyst was in the form of granules of activated alumina, soaked in 5% of the oxides of copper and chromium, the amount of 0.1 inch (2.54 mm). The layer of the heat exchanger consisted of pellets of the same size from a dense fused alumina (Corhart).

Other ways of using pre-heating and/or changing the direction of flow for the catalytic purification of exhaust gases is described, for example, in U.S. patent N 4059676 in the name of Yang Kang and James D. Reedy, Continental Oil Company; U.S. patent N 4877592 in the name of Juri S. Matros, Viktor A. Chumachenko, Ljudmila J. Zudilina, Alexandr S. Noskov and Evgeny S. Bugdan (Institute of catalysis, Siberian branch of the USSR Academy of Sciences; Special design technological Bureau with pilot plant) and in U.S. patent N 4966611 in the name of John C. Schumacher, Joseph S. McMenamin, Lawrence C. Anderson, Harold R. Cowles and Stephen M. Lord, Custom Engineered Materials Inc.

Regardless of the device used and how any successful industrial application depends on the choice of the oxidation catalyst suitable for volatile compounds, which are preferably subjected to destruction, and the viability of the catalyst in this system. The lifetime of the catalyst is often limited due to the effect on catalytic oxidation of compounds that destroy their catalytic activity. Historically, the presence of significant quantities of Halogens and/or organic and neo who was panstwowego using catalytic oxidation for this purpose. Believed that the presence of Halogens and/or galoidoproizvodnykh, regardless of are these compounds degrade, degrade and temporarily poisons the catalysts on the basis of some precious metals.

Catalytic combustion of combustible substances containing a noble metal (platinum) or its mixture with other metals, is described in U.S. patent N 3378334 in the name of Herman S. Bioch, Universal Oil Product Company. Also described catalysts hydrated oxide of metals. For example, in U.S. patent N 4059677 in the name of Edward J. Sare and Jerome M. Lavanich, PPG Industries, Inc. States that waste containing halogenated2-C4hydrocarbons, especially unsaturated chlorinated hydrocarbons such as vinyl chloride, are burned in the presence of a mixture of hydrated oxides of manganese and cobalt. The catalytic system on the media containing a metal of group VIII (platinum), as described in U.S. patent N 5145826 in the name of Eugene N. Hirschberg, and George A. Huff, Jr., Amoco Corporation.

In U.S. patent N 5292704 in the name of George R. Lester, Allied-Signal Inc. States that waste containing halogenated C1compounds that do not have carbon-hydrogen bonds, burned with obtaining carbon dioxide and haloesters acids (HCl, HBr, and so on) in the presence of combinations of precious metal (the mA and perhaps a good amount of water. However haloesters acids are very corrosive contaminants.

The main purpose of this invention to provide improved devices and methods that allow to solve the above problems encountered in the implementation of known methods, associated with the reduction of emission of carbon monoxide and volatile organic compounds in the chemical process, when the formation of gaseous waste or exhaust gas containing a mixture of potential pollutants.

More specifically, the purpose of this invention is to create integrated systems for catalytic treatment of exhaust gas, which reduce air pollution by reducing particle concentration in the exhaust gas emitted into the atmosphere.

Another purpose of this invention is the creation of integrated systems for catalytic treatment of exhaust gas, which provide low content of carbon monoxide and potential pollutants at lower operating temperatures.

Another objective of this invention is the creation of integrated systems kata is nisit requirements for this fuel by regulating the amount of carbon monoxide and potential pollutants.

Another objective of this invention is to provide an integrated catalytic processing systems, off-gas, which allow to extend the period of operation of the furnace for burning waste, reduce installation costs and reduce the frequency and duration of downtime.

Another objective of this invention is to create integrated systems for catalytic treatment of exhaust gas with a reduced cost of energy consumption.

While the above goals can be achieved using integrated systems for catalytic treatment of exhaust gas in accordance with the invention, other objectives and advantages of the invention will become apparent from the following detailed description and claims.

The invention

The proposed cost-effective treatment system for reducing emissions of carbon monoxide and volatile organic compounds in the chemical industries, which provide for the removal of off-gas flow containing potential pollutants and excess oxygen. Methods according to this invention include (A) dispersing a controlled amount of ventrucci a significant part of organic pollutants by oxidation on the oxidation catalyst at elevated temperatures, and (C) regulation of the quantity of the combustible fluid introduced into the flow of exhaust gas, thereby to provide sufficient reagents for catalytic oxidation to maintain the reaction temperature in a suitable range of values.

According to this invention provides a method of reducing emissions of volatile chemical compounds from industrial installations where the exhaust gas contains oxygen, carbon monoxide, hydrocarbons and other organic compounds comprising one or more C1-C5alkylhalogenide, including:

(A) dispersing flammable fluid selected from the group consisting of carbon monoxide, hydrogen, C1-C5hydrocarbon, C1-C5organic compounds containing at least one oxygen atom in the molecule and mixtures thereof, in the off-gas flow at a pressure ranging from atmospheric to 20 atmospheres;

(C) oxidation of the combustible fluid and the destruction of at least 90% of carbon monoxide, at least 80% of the hydrocarbons, and at least 50% of alkylhalogenide in the flow of the exhaust gas by oxidation over a solid oxidation catalyst, which is at Mei, zirconium oxide and aluminum oxide, and optionally at least one member of the group consisting of tungsten oxide, vanadium oxide, tin oxide, and metals - platinum, palladium and rhodium;

(C) regulation of the quantity of the combustible fluid introduced into the flow of exhaust gas, thereby to provide sufficient reagents for catalytic oxidation to maintain suitable for the oxidation reaction temperature in the range from 200 to 600oC with the formation of the exit stream of the oxidation product containing unreacted oxygen, carbon dioxide and water;

(D) cooling the product stream of the oxidation coming from the stage catalytic oxidation, by simultaneous transmission of the stream of the oxidation product and the flow of raw exhaust gas through gas-to-gas heat exchanger for heat transfer; and

(E) contacting of the flow of the cooled oxidation product with an aqueous medium comprising at least one member of the group consisting of lime, ammonia, sodium formiate, sodium sulfide, urea and formaldehyde in the gas scrubber to form a liquid solution of soluble compounds and treated off-gas.

The choice of the combustible techcareers to regulate working conditions over the oxidation catalyst without adversely affecting the catalyst activity. Connections to flammable fluid should be predominantly in the gaseous state at operating conditions of the process. Suitable combustible fluids contain carbon monoxide, hydrogen, hydrocarbons, and organic compounds containing at least one oxygen atom in the molecule. Usually organic compounds that are suitable as a combustible fluid, are compounds such as alkanes, alkenes, alcohols, ethers, aldehydes (alkanal), ketones (Alcanena), organic acids and mixtures thereof which have a boiling point under normal conditions ranging from approximately 200oC to about -165oC, preferably in the range from about 160oC to about -50oC and most preferably in the range from about 130oC to about 30oC. Selected flammable fluids represent a compound selected from the group consisting of carbon monoxide, hydrogen, C1-C5hydrocarbon, C1-C5organic compounds containing at least one oxygen atom in the molecule, and mixtures thereof, preferably at least one compound from the group consisting of carbon monoxide, hydrogen, methanol, ethanol, 1-propanol, 2-propanol, 2 is tan, Aten (ethylene), propene (propylene), 1-butene (-butylene), 2-butene (-butylene), methylpropene (isobutylene), 1-penten (-Amylin), 2-penten, 2-methyl-1-butene, 2-methyl-2-butene, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol (isobutyl alcohol), 2-methyl-2-propanol (tert-butyl alcohol), methoxymethane (dimethyl ether, methoxyethane (metaliteracy ether), ethoxyethane (diethyl ether), 1-methoxypropan (methyl-n-propyl ether), 2-methoxypropan (metrizability ether), 1-methoxybutan (methyl-n-butyl ether), methanol (formaldehyde), ethanal (acetaldehyde), propanal (propionic aldehyde), butanol (n-Butyraldehyde), methylpropanal (Isobutyraldehyde), pentanal (n Valerian aldehyde), dimethylpropyl (trimethyloxonium aldehyde), propanone (acetone), butanone (methyl ethyl ketone), 3-pentanon (diethylketone), 2-pentanone (methyl-n-propylketone), methane, ethane and mixtures thereof.

In a broad sense the invention is a system for processing exhaust gas to reduce emissions of carbon monoxide, volatile hydrocarbons and other volatile compounds from chemical installations where the exhaust gas contains potential pollutants and excess oxygen. More specifically, the system includes a vessel for oxidized the Oia flow temperature of the exhaust gas over the oxidation catalyst; means for feeding hot fluid medium in the flow of exhaust gas in the upper part of the autoclave oxidation to facilitate catalytic oxidation of organic pollutants; means for determining the temperature of exhaust gas under the layer of oxidation catalyst; and means for controlling the amount of combustible fluid supplied by the means for supplying and regulating means is constructed so as to provide sufficient reagents for catalytic oxidation to maintain suitable reaction temperatures.

Treatment system exhaust gas according to this invention mainly include gas heat exchanger located in the flow of the oxidation product leaving the vessel to oxidation, and in the flow of raw exhaust gas for the implementation of heat transfer between them. The gas scrubber may be located along the flow of the oxidation product gas below the heat exchanger.

According to another aspect of the invention relates to a method for processing exhaust gas to reduce emissions of carbon monoxide, volatile hydrocarbons and alkylhalogenide of chemical installations where the flow of the exhaust gas contains the Oka exhaust gas of the regulated quantity of the combustible fluid, moreover, the temperature of the flue gas is in the range of temperatures in excess of approximately 25oC, usually in the range of from about 30oC to about 600oC;

(C) oxidation of the combustible fluid and the destruction of a significant part of organic pollutants by oxidation over a selected solid oxidation catalyst at temperatures in the range of from about 150oC, usually in the range of from about 200oC to about 600oC; and

(C) regulation of the quantity of the combustible fluid introduced into the flow of exhaust gas in such a way as to provide sufficient reagents for catalytic oxidation, in order to maintain a suitable reaction temperature. One class of suitable combustible fluid preferably is selected from the group consisting of hydrogen and organic compounds containing at least one oxygen atom in the molecule, and organic compounds have a boiling point under normal conditions in the range of from about 200oC to about -165oC, preferably in the range of from about 160oC to about -50oC and more preferably in the range of from about 130oC to about 30oC.

production of organic acids and/or their anhydrides, in particular dibasic aromatic acids such as isophthalic acid, terephthalic acid, 2,6-natalijagolosova acid, or anhydrides, such as timetravel anhydride, etc., One or more compounds containing halogen is usually a critical component of the catalytic oxidation system used for the industrial production of dibasic aromatic acids. This is, for example, processes in which the flow of exhaust gas is a product containing nitrogen, excess oxygen, volatile hydrocarbons and other organic compounds such as volatile alkylhalogenide facing in the liquid-phase oxidation in obtaining aromatic acid from the corresponding methylsiloxanes aromatic compounds in contact with oxygen source, such as compressed air, in the presence of a catalytic oxidation system at elevated pressures and temperatures. Integrated processing system according to this invention are preferably used to reduce emissions of carbon monoxide and volatile organic compounds from a process of liquid-phase oxidation for the extraction of aromatic acids such as isophthalic acid, tower description and the claims, as well as the drawing shows a more detailed explanation of the invention.

The drawing shows a simplified schematic diagram of the integrated method of processing exhaust gas to reduce emissions of carbon monoxide and volatile organic compounds from chemical installations using the device for catalytic oxidation of organic pollutants with oxygen in the flow of exhaust gas over a solid oxidation catalyst, means for supplying combustible fluid into the flow of exhaust gas during its course above the autoclave for oxidation to facilitate catalytic oxidation of organic pollutants and means for controlling the amount of combustible fluid introduced through the means for feeding and the means for regulating is designed to provide sufficient reagents for catalytic oxidation, in order to provide a suitable reaction temperature in accordance with this invention.

System for catalytic treatment of exhaust gas to reduce emissions of volatile chemical substances according to the invention are used for the destruction of volatile organic compounds, CodeGate streams are formed, for example, when implementation of the processes of production of organic chemicals and polymers, impregnation of textiles, food processing, manufacture of rubber and during operations, when for coating, cleaning and/or degreasing in the processing and finishing of metals used volatile organic solvents.

Exhaust gases, which can be treated according catalytic method according to this invention may contain the majority of substances that are flammable in the presence of oxygen at temperatures in the operating temperature range installation. These substances are usually (without limitation of the scope of the invention) carbon monoxide, hydrogen, hydrocarbons, and organic compounds that contain other atoms such as oxygen, nitrogen, Halogens and the like. Usually, the potential contaminants include volatile compounds such as alkanes, alkenes, alcohols, ethers, aldehydes (alkanal), ketones (Alcanena), organic acids and mixtures thereof, which form a pair, located in the exhaust gas.

For security purposes, the amount of organic compounds in the discharged air or the exhaust gas should normally beat less than about 50% of the LEL, and more preferably less than about 25% of the LFL. The composition of gas streams for security purposes, usually controlled on-line, and the quantity of the combustible fluid supplied into the flow of exhaust gas is controlled so as to provide sufficient reagents for catalytic oxidation, in order to maintain a suitable reaction temperature.

The total pressure in the reactor according to this invention is in the range between 1 and 20 atmospheres and preferably from 2/3 to 14 ATM.

Treatment of exhaust gas in accordance with this invention includes contacting wybranego gas with a catalyst in the presence of excess oxygen under suitable temperatures, which are typically less than approximately 600oC. All stages according to this invention mainly carried out at temperatures of entrance flow in a layer of oxidation catalyst being in the range from about 550oC to about 50oC depending on the composition wybranego gas and the specific nature of the catalytic system. Catalysts do not change the composition of the reaction product to an equilibrium, but can accelerate the achievement of an equilibrium state at lower energy levels (lower temperatures). While canimi compounds in the exhaust gas or under severe conditions.

Flow rate are in the range between about 100 h-1and about 200,000 h-1preferably, between approximately 1000-1h 50,000 h-1per volume of catalyst.

In accordance with this invention, the oxidation catalyst contains accelerating the combustion of the metal deposited on the carrier. Ordinary metals can be used for processing vibronic streams containing CO and/or organic compounds that have a relatively high capacity for destruction, such as alcohols, cellosolve, aldehydes and the like. In General, the higher molecular weight specific organic compounds, the higher its propensity for destruction. Noble metals are primarily used for processing vibronic streams containing organic compounds with a relatively low propensity for destruction, such as aromatic compounds, ketones, acetates, alkanes, halogenated hydrocarbons and the like.

According to this invention, the catalyst can be used in any suitable configuration, shape and of any suitable dimensions that enable the exposure of accelerating the oxidation catalyst components dcov, rings, spheres, etc. If you need large amounts of catalysts, as in the case where it is desired periodic replacement of the catalyst, it is desirable to use a catalyst in the form of microparticles. In cases where it is desired to have a smaller mass or when moving or mixing of the catalyst particles can lead to abrasion, dust and as a consequence the loss of the dispersed metal or unnecessary increasing the pressure drop in the layer of particles, the preferred monolithic form. According to this invention, the catalysts are usually used in the form of granules or solid particles.

Media for the oxidation catalyst may be less catalytically active or even inert to oxidation reactions. For best results it is desirable that the carrier was porous and had a surface area, including the area of the pores on the surface equal to at least about 25 m2/g to about 250 m2/g, preferably from about 50 m2/g to about 200 m2/g and more preferably from about 80 m2/g to about 150 m2/, Suitable carrier materials according to this invention include mullite, spinel, sand, silica, alumina, silica-alumina, titanium dioxide Titus Preferred media containing alpha-alumina, gamma-alumina, silica or silica-alumina. More preferred are media containing alpha-alumina or gamma-alumina.

The carrier of the oxidation catalyst can be a homogeneous or composite material. Composite carriers of pre-emption where it is desirable that the catalyst has acquired additional chemical or physical properties. For example, the oxidation catalyst may contain a carrier and a coating on the media, to use the specific advantages of both, while the substrate materials have high resistance to wear, and coating materials have a large surface area. The substrate and its coating can be joined using conventional methods of impregnation. For use as a composite substrate for oxidation catalyst suitable alumina, silica, titanium dioxide, alumina-silica, zirconium dioxide, alpha-alumina, gamma-alumina, Delta-alumina and ETA-alumina. Coating of the substrate is made of silicon dioxide, titanium dioxide, silica-alumina, the preferred material is gamma-oxide and the x2">

One of the preferred options is one in which a solid oxidation catalyst contains titanium dioxide and optionally at least one representative of the group consisting of tungsten oxide, vanadium oxide, tin oxide, and metals - platinum, palladium and rhodium; titanium dioxide deposited on a ceramic or metal carrier.

The method of processing exhaust gas to reduce emissions of volatile substances from industrial installations according to the invention can be carried out using solid oxidation catalysts comprising silica, alumina, titanium dioxide, silicon dioxide-aluminum oxide, zirconium dioxide and/or aluminum oxide deposited on a ceramic or metallic porous media.

Promoting the combustion of the metal according to this invention may refer to metals used or known in this area to accelerate the oxidation of carbon monoxide to carbon dioxide in the presence of molecular oxygen. The metal may be in the form of compounds, such as oxide, preferably than its application in the form element. Promoting the oxidation of the metal may contain two or more catalytically what tall according to this invention are transition metals, preferably group VIII of the Periodic table (IUPAC), more preferably precious metals and even more preferably platinum and palladium. Platinum is preferred because of its ability to retain high activity in the oxidation of carbon monoxide.

The amount of promoting the oxidation of the metal that is added to the oxidation catalyst used according to this invention depends on the cost of the catalyst and the performance of the method. In General promoting the oxidation of the metal is an expensive component of the oxidation catalyst. Higher concentrations of the metal and the use of smaller volumes reduce the cost of media and oxidation catalyst. For best results, the concentration of metals in the catalyst, promoting combustion, according to this invention can vary in weight from about 0.1 ppm to about 15000 ppm, preferably from about 0.5 ppm to about 10,000 ppm, and more preferably from about 1 ppm to about 8000 ppm.

Component of the group of platinum can be introduced into the carrier in any suitable manner such as coprecipitation, joint gelation media, ion exchange or impregnation. Preferably the platinum group component was evenly distributed is of a water-soluble compounds of platinum group element for impregnation of the carrier prior to calcination. For example, platinum can be added to the carrier by mixing 'green' carrier with an aqueous solution chloroplatinic acid. Other water-soluble compounds of platinum may be used for impregnating solutions, including, for example, ammonium salt chloroplatinic acid and chloride of platinum.

The oxidation catalyst used according to this invention, must have suitable physical properties for use in stationary oxidation layer. The most important physical characteristics in the implementation of the present invention is a pressure drop in the catalyst bed, and resistance to wear.

Some particularly suitable oxidation catalysts vibronic gases is described. For example, in U.S. patent N 3378334 described fixed bed of spherical particles of a catalyst containing up to about 5% of the catalytically active metal, such as platinum, palladium, iridium, ruthenium, rhodium, various mixtures, including platinum-iron, platinum-cobalt, platinum-Nickel, palladium-iron, palladium-cobalt, palladium-Nickel, platinum-palladium, palladium-copper-cobalt, platinum-copper-lithium-cobalt, platinum-cobalt-copper, copper-cobalt-Nickel-platinum, platinum-palladium-cavalry oxidation usually composed as well as other catalysts for conversion of hydrocarbons they contain refractory inorganic oxide as the base or carrier, such as alumina, alumina-silica, alumina-Zirconia, and so on, which is applied by deposition or impregnation of one or more triggering components, namely the catalytically active metals or oxides of metals. Especially desirable activating component for burning combustible gases are the platinum group metal, particularly platinum and palladium; they are characterized by excellent activity in the conversion of carbon monoxide, hydrocarbons and oxygen-containing hydrocarbons in a long time.

Suitable catalysts containing ruthenium, ruthenium and platinum, and platinum dispersed on a non-oxidizing medium is described in U.S. patent N 4059675, 4059676 and 4059683 respectively. In the first patent disclosed the use of 0.01-1.0 wt.% ruthenium on a non-oxidizing carrier for the decomposition of chlorinated hydrocarbons containing up to 4 carbon atoms and containing at least as many hydrogen atoms as chlorine atoms, at temperatures of at least about 350oC. In the second proposed patent application bikerneu platinum 1 hour ruthenium deposited on a non-oxidizing carrier for the decomposition of chlorinated hydrocarbons containing up to 4 carbon atoms and having at least as many hydrogen atoms as chlorine atoms, at temperatures of at least about 350oC. Chlorinated compounds that undergo degradation include vinyl chloride and a mixture of C1-chlorinated and C2-chlorinated compounds containing vinyl chloride, with the total number of hydrogen atoms in the mixture to at least the number of chlorine atoms. Using these catalysts receive the products of oxidation, representing the CO2H2O, HCl and Cl2.

Catalysts containing (a) iron, dispersed on alumina, which is a carrier, and a rare-earth metal, especially iron oxides and praseolite, and (b) an intermediate oxide of tungsten, in which the average valence of the radical tungsten is greater than 4 and less than 6, are described in U.S. patent N 4610975.

Catalysts containing palladium and/or platinum and at least three component promoter deposited on a porous carrier, is disclosed in U.S. patent N 4857499. The first component of the promoter includes one of rare earth elements such as lanthanum, cerium, parsetime is omotola includes magnesium, silicon and its oxides, and the third component of the promoter includes one of the heavy metals, such as Nickel, zirconium, cobalt, iron and manganese, and their oxides.

In U.S. patent N 5176897 described is particularly suitable catalysts containing titanium dioxide and optionally tungsten oxide, vanadium oxide, tin oxide and noble metals platinum, palladium and rhodium, for use with an effective amount of water to turn haloesters organic compounds to carbon dioxide and the corresponding galoidvodorodnykh acid.

The following examples serve to illustrate certain specific forms of embodiment of the disclosed invention. These examples, however, should not be construed as limiting the scope of invention, as the person skilled in the art it is obvious that, without departing from the scope of the invention, it is possible to make various changes on the basis of this description.

Examples of carrying out the invention

In the following examples, the simultaneous oxidation of the combustible fluid and the destruction of a significant part of potentially harmful volatile organic compounds oxidation over an oxidation catalyst at elevated temperatures is carried out with the use of may of the catalyst on the carrier. External heating is carried out by means of electric heaters. The inner surface of the reactor made from materials that do not show catalytic activity in various operating conditions described in the examples. Thermocouples placed in the apparatus, especially in the reactor immediately above and below the catalyst bed. Combustible fluid and the exhaust gas is continuously measured and is fed through a static mixer upward flow in the reactor. The temperature of the gas mixture entering the reactor, usually equal to approximately 200oC. the Concentration of organic compounds in the incoming gas into the reactor and the exhaust gas is determined by gas chromatography using flame ionization.

The concentration of oxide and carbon dioxide is measured using infrared analyzers. Oxygen concentration is measured using an electrochemical analyzer. Unless otherwise indicated, the compositions are given in volume percent and parts per million by volume (ppmv).

Example 1

In this example, carried out a series of treatments of exhaust gas according to this invention, using as the combustible fluid methanol in combination with a catalyst for decomposition of organic coedie, arriving in the reactor contain from about 2% to about 6% oxygen, from about 0.1% to about 0.5% carbon monoxide, from about 0.5% to about 3.0 percent carbon dioxide, from about 0.2% to about 2% water, from about 1 ppm to about 1000 ppm of each of the acetate, bromide, methylformate, benzene, toluene, p-xylene and acetic acid, from about 3000 ppm to about 14000 ppm of methanol, and the rest is nitrogen.

When the temperature in the reactor in the range of from about 415oC to about 510oC, the pressure in the reactor from about 11 atmospheres to approximately 11.7 MPa and a speed of about 10000 h-1(the velocity of the gas stream at standard conditions/volume of catalyst) the conversion of carbon monoxide, methyl acetate, bromide, methylformate, benzene, toluene, p-xylene and acetic acid is approximately 97% and above. When the temperature in the reactor in the range of from about 310oC to about 510oC and velocity of the gas stream to about 10000 h-1(the velocity of the gas stream at standard conditions/volume of catalyst) degree of conversion of methanol equal to about 99% and above. Analysis of the stream exiting the reactor, for burning shows the presence of carbon dioxide, water, bromine (Br2) and hydrogen bromide (Found. In these experiments, there was no reduction in catalyst activity.

Comparative example AND

In this comparative example is carried out a series of experiments as in example 1, but without a catalyst and at very low concentrations of methanol in the range from about 30 ppm to about 60 ppm calculated on the whole the feed gas. Under the conditions of example 1, there is no significant oxidation of any organic compounds or carbon monoxide in the feed gas into the reactor, even when the temperature in the reactor to about 550oC, a pressure of about 950-1100 kPa.

Comparative example

In this comparative example is carried out a series of experiments as in example 1, but without adding any of the combustible fluid in the feed to the reactor gas and at very low concentrations of methanol in the range of from about 30 ppm to about 35 ppm calculated for the whole of the supplied gas. The temperature of the catalyst layer regulate when an external electric heaters.

The gaseous mixture entering the reactor, have a composition that includes from about 2% to about 6% oxygen, from about 0.1% to about 0.5% carbon monoxide, from about 0.5% to about 3% carbon dioxide, from about 0.2% to about 2.0% of water, from about 1 ppmv to the slots, the rest is nitrogen.

When the pressure in the reactor in the range from about 9.5 to 1.03 ATM ATM, the temperature in the reactor from about 438oC and above, and the gas flow velocity of about 10600 h-1the degree of conversion of carbon monoxide, methyl acetate, bromide, methylformate, benzene, toluene, p-xylene and acetic acid is about 95% and above. When the temperature in the reactor from about 494oC and higher conversion rate of approximately 98% and above.

Comparative example

In this comparative example is carried out a series of treatments of the exhaust gas, as in example 1, but using hexane as the combustible fluid in combination with a catalyst for the destruction of volatile organic compounds composed of base metal, in the form of granules.

The gaseous mixture entering the reactor, have a composition that includes approximately 5.8% oxygen, and 2.0% water, from about 1 ppm to about 1000 ppm of each of the bromide and methanol, from about 4000 ppm to about 5000 ppm of hexane, and the rest nitrogen.

When the temperature in the reactor in the range of from about 415oC to about 510oC, the reactor pressure from about 760 kPa to about 900 kPa and flow rate of gas, equal to about 10 is romida, methanol and hexane was about 91, 92, and 99.8%, respectively, as determined by the decrease of their concentration along the reactor. Analysis of the gas emerging from the reactor for combustion shows the presence of carbon dioxide, water, bromine (Br2) and hydrogen bromide (HBr). However, in the gas leaving the reactor, was found about 10 ppmv benzene. I think that, probably, this benzene is formed from hexane. Brombenzene were also detected in the exhaust gas, which can be obtained by the reaction between benzene and bromine (Br2). If hexane is contained in the gas supplied to the reactor in amounts required for combustible fluid, the formation of benzene and brombenzene makes hexane unacceptable as the combustible fluid.

As can be seen from example 1 and comparative examples described above, a method of reducing emissions of volatile chemicals from industrial plants according to the invention can be effective in obtaining aromatic acid from the corresponding methylsiloxanes aromatic compounds by catalytic liquid-phase oxidation of methyl groups by excess oxygen in the presence of a source of bromine, while the exhaust gas contains bromide.

Cu is in various forms, this description and the corresponding drawings disclose only some specific forms as examples of the use of the invention. Specific preferred cases when processing the exhaust gas from the catalytic liquid-phase oxidation is described the use of compressed air. The invention is not limited to the described examples, and the scope of the invention defined by the following claims.

The device according to this invention is used with some common elements, the details of which, although not fully illustrated or described, will be obvious to experts in the field who are familiar with the functions of these elements.

As can be seen from the drawing, integrated treatment system exhaust gas includes one or more vessels for oxidation; shows the vessel 44 containing a suitable solid oxidation catalyst; the heater exhaust gas is shown as a heat exchanger 22; and cooling means and/or scrubbers, shown in the form of a tower 66.

During operation of the system the flow of exhaust gas containing volatile compounds and an excess of oxygen, for example, coming from the installation of liquid-phase catalytic oxidation with the use of the re to the minimum temperature catalytic conversion. The nitrogen content in the flow of such exhaust gas is generally greater than about 90% by volume; a content of oxygen is less than 10%, usually less than about 7.5%; carbon monoxide and water vapor together comprise less than about 7.5%, usually less than about 5%. The level of organic pollutants in the stream of exhaust gas mainly considerably below the lower explosive limit at the operating conditions, preferably this level is less than about 50% of the LEL.

The temperature of the heated gas of approximately 150oC and above, usually equal to from about 200oC to about 600oC. the Flow of heated gas is passed from heat exchanger 22 through lines 25 and 33 in the vessel to oxidize 44.

To facilitate catalytic oxidation of volatile compounds combustible fluid in a certain amount is mixed with a stream of heated exhaust gas entering through line 31 or elsewhere in the vessel for oxidation upstream of the gas flow. The quantity of the combustible fluid is normally regulated dosing pump or control flow (not shown). Provides a means for regulating the amount of combustible fluid to provide sufficient SS="ptx2">

The quantity of the combustible fluid can be adjusted manually using conventional devices, such as thermocouples for measuring at least the temperature of exhaust gas upstream of the flow over the oxidation catalyst and the temperature of exhaust gas downstream of the flow under the oxidation catalyst, and can be adjusted flow rate and gas composition. However, the automatic control and measuring equipment, primarily adapted for regulating the amount of combustible fluid, and is constructed so as to provide sufficient reagents for catalytic oxidation to maintain the desired reaction temperature in the vessel to oxidize 44 and limit the total number of organic compounds in the gas to levels significantly below the LEL at operating temperatures, mostly equal to from about 50% of the LEL and below and more preferably below about 25% LFL.

Using the selected oxidation catalysts under suitable operating conditions destruction occurs even kaleidoscopically compounds. In particular, the bromide decomposes to form hydrogen bromide and/or bromine.

The temperature of the hot gas leaving the P>C to about 600oC. the Hot gas from the heat exchanger 22 is passed through line 23 into the lower part of the column 66, where the gas is cooled and washed. In the column on line 66 for supply 51 is supplied suitable aqueous solvent.

Typically, the aqueous solvent is a dilute solution chemical bases, namely, substances which in aqueous solution increases the concentration of hydroxyl ions. the pH of these aqueous-alkaline solutions is between about 7 and above, preferably the pH is in the range from about 7 to about 9. If the gas stream contains haloesters connection, the solvent may contain an additive compounds, which react with halogen, contributing to leaching. Usually suitable compounds are appreciably soluble oxides, hydroxides, carbonates, sulfides, etc. of alkali metals and calcium, strontium, barium and ammonium. Sources of suitable compounds include industrial chemicals such as lime (CaO), ammonia (NH3), ammonium hydroxide (NH4OH), sodium hydroxide (NaOH), sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3), sodium formate (NaCO2H), sodium sulfide (NaS), urea (NH2)CONH2, formaldehyde bromine, aqueous solvent mainly contains dilute caustic.

The solution of soluble compounds is removed from the system by line for liquid 53 in any suitable processing waste liquid/solid. The processed gas is delivered from the tower 66 through line 63 to the release of energy and/or processing for industrial purposes, e.g. for use as an inert carrier gas or gas outlet.

The method in accordance with this invention typically can achieve degrees of decomposition: carbon monoxide approximately 90% or more, preferably about 95% and above for the hydrocarbon - about 80% or more, preferably about 90% and above for methyl bromide is about 50% or higher, preferably about 85% and above.

The system usually begins with the filing of the air (the tool to supply not shown) and any ordinary fuel line 71 into the combustion chamber 72 for receiving hot air from the combustion chamber 72 through lines 73 and 45 flows into the heat exchanger 22, where the oxygen-containing gas, triggering the installation, such as a compressed air supply not shown), is heated at least to the minimum temperature catalytic conversion, usually about 150o

1. The way to reduce emissions of volatile chemicals from industrial plants, flue gas which contains oxygen, carbon monoxide, hydrocarbons and other organic compounds, including one or more alkylhalogenide with 1 to 5 carbon atoms, comprising (A) dispersing flammable fluid selected from the group consisting of carbon monoxide, hydrogen, C1-C5hydrocarbon, C1-C5organic compounds containing at least one oxygen atom in the molecule, and mixtures thereof in the stream of exhaust gas at pressures in the range of from atmospheric to 20 atmospheres; (C) oxidation of the combustible gas and the destruction of at least 90% of carbon monoxide, at least 80% of the hydrocarbons, and at least 50% of alkylhalogenide in the exhaust gatewaypundit from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, silicon dioxide-aluminum oxide, zirconium dioxide and aluminum oxide; (C) regulation of the quantity of the combustible fluid supplied to the exhaust gas, thereby to provide sufficient reagents for catalytic oxidation to maintain the desired reaction temperatures in the range 200 - 600oC for the oxidation of obtaining oxidation product containing unreacted oxygen, carbon dioxide and water; (D) cooling the product stream of co oxidation stage catalytic oxidation by simultaneous transmission of the stream of the oxidation product and the flow of raw exhaust gas through a gas heat exchanger for heat transfer; (E) contacting the cooled oxidation product with an aqueous medium containing at least one representative from a group consisting of lime, ammonia, sodium formiate, sodium sulfide, urea and formaldehyde, a tower scrubber with formation of a solution of soluble compounds and flow of the treated flue gas.

2. The method according to p. 1, in which the solid catalyst additionally contains at least one representative selected from the group sotoyama the m flue gas is gas, coming upon receipt of aromatic acids from the corresponding methylsiloxanes aromatic compounds by catalytic liquid-phase oxidation of methyl groups by excess oxygen in the presence of a source of bromine, while the exhaust gas contains bromide.

4. The method according to any of the preceding paragraphs, in which the aqueous medium contains at least one representative of the group consisting of sodium formate, sodium sulfide, urea and formaldehyde.

5. The method according to any of the preceding paragraphs, in which the combustible fluid is at least one representative of the group consisting of carbon monoxide, hydrogen, methanol, ethanol, 1-propanol, 2-propanol, 2-butanol and 2-methyl-2-propanol.

6. The method according to any of the preceding paragraphs, in which the oxidation is carried out at pressures in the range of 2/3 - 14 ATM and the flow velocities in the range of 1000 to 50000 h-1calculated as the rate of flow of gas at standard conditions per volume of catalyst.

7. The method according to any of the preceding paragraphs, in which the solid oxidation catalyst contains titanium dioxide and, optionally, at least one representative of the group consisting of oxide wolframites or metal carrier.

8. The method according to p. 7, in which 95% or more of carbon monoxide in the exhaust gas will destroy in the process of oxidation on solid oxidation catalyst, 90% or more of the hydrocarbons in the exhaust gas will destroy in the process of oxidation on solid oxidation catalyst and 85% or more of methyl bromide in the exhaust gas is converted into hydrogen bromide (HBr) and/or bromine (Br2) the above solid catalyst oxidation.

9. The method according to p. 7 or 8, in which the combustible fluid is at least one representative of the group consisting of hydrogen, methanol and butane.

10. The method according to any of the preceding paragraphs, in which the aqueous medium has a pH in the range 7 to 9.

11. The method according to any of the preceding paragraphs, in which silica, alumina, titanium dioxide, silicon dioxide - aluminum oxide, zirconium dioxide and/or aluminum oxide deposited on a ceramic or metallic porous media.

 

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