RU2257952C1 - Catalytic system for heterogeneous reactions - Google Patents

Abstract

FIELD: heterogeneous catalysts.

SUBSTANCE: catalytic system comprises (i) high-silica fibrous carrier characterized by ²⁹Si MNR spectrum, in which lines with chemical shifts -100±3 ppm (line Q³) and -110±3 ppm (line Q⁴) are present at ratio of integral intensities Q³/Q⁴ from 0.7 to 1.2; IR spectrum, in which absorption bands of hydroxyl groups with wave number ν=3620-3650 cm^-1 and half-width 65-75 cm^-1 are present; which carrier has specific surface S_Ar=0.5-30 m²/g as measured by BET method from thermal desorption of argon, surface area S_Na=10-250 m²/g as measured by alkali titration method, at S_Na/S_Ar ratio 5 to 30; and (ii) at least one active element. The system represents geometrically structured one constituted by microfibers with diameter 5-20 μm and additionally has active centers characterized in IR spectra of adsorbed ammonia by presence of an absorption band with wave numbers ν=1410-1440 cm^-1.

EFFECT: increased catalytic activity, resistance to deactivation, and selectivity.

3 cl, 7 ex

Description

The invention relates to the field of chemical industry, to new catalysts that can be used, in particular, in processes for the disposal of organochlorine wastes, purification of gaseous and liquid emissions from toxic organochlorine impurities, in the processes of oxidation of sulfur dioxide to trioxide, in the production of sulfuric acid or in the purification of sulfur-containing industrial gas emissions, in the processes of obtaining a valuable monomer - vinyl chloride from dichloroethane, in the processes of production of such valuable products from methane and natural gas s as methyl chloride, vinilhlodid light olefins, in processes of purification of diesel engine exhaust gases, in the processes of deep oxidation of toxic organic impurities in other processes.

A known catalyst for heterogeneous reactions containing at least one catalytically active element and a high siliceous carrier, characterized by the presence in the NMR spectrum of ²⁹ Si lines with a chemical shift of -100 ± 3 ppm (line Q ³ ) and -110 ± 3 ppm. (line Q ⁴ ) with a ratio of the integrated intensities of the lines Q ³ / Q ⁴ from 0.7 to 1.2, in the infrared spectrum of the absorption band of hydroxyl groups with a wave number of 3620-3650 cm ^-1 and a half-width of 65-75 cm ^-1 , having a specific surface area measured BET method for thermal desorption of argon S _Ar = 0.5-30 m ² / g, the surface value measured by alkaline titration method S _Na = 10-250 m ² / g at a ratio of S _Na / S _Ar = 5-30 (RF Patent No. 2160156, IPC 6 B 01 J 21/08, priority dated 28.12.1999, published on 10.12.2000).

The disadvantages of the known catalyst are relatively low activity, deactivation in aggressive reaction media, as well as low selectivity of transformations in a number of reactions.

The authors were tasked with developing a catalytic system for heterogeneous reactions with higher activity, resistance to deactivation, and increased selectivity.

The problem is solved in that the catalytic system for heterogeneous reactions, including a high siliceous fibrous carrier, characterized by the presence in the NMR spectrum of ²⁹ Si lines with a chemical shift of -100 ± 3 ppm (line Q ³ ) and -110 ± 3 ppm. (line Q ⁴ ) when the ratio of the integrated intensities of the lines Q ³ / Q ⁴ 0.7-1.2, in the infrared spectrum of the absorption band of hydroxyl groups with a wave number of ν = 3620-3650 cm ^-1 and a half-width of 65-75 cm ^-1 having a specific surface, measured by the BET method for thermal desorption of argon, S _Ar = 0.5-30 m ² / g and the surface value measured by the method of alkaline titration, S _Na = 10-250 m ² / g at a ratio of S _Na / S _Ar = 5-30 , and at least one active element, is a geometrically structured system of microfibers with a diameter of 5-20 microns, additionally having there are active centers, which are characterized in the IR spectra of adsorbed ammonia by the presence of an absorption band with wave numbers in the range ν = 1410–1440 cm ^–1 . In addition, the active component of the catalytic system is selected from the group comprising platinum, palladium, rhodium, iridium, silver, zirconium, chromium, cobalt, nickel, manganese, copper, tin, gold, titanium, aluminum, iron, molybdenum, and / or their oxides , and / or their salts, and microfibers are structured in the form of either non-woven or pressed material such as cotton wool or felt, or filaments with a diameter of 0.5-5 mm, or woven from filaments with weaving such as satin, linen, openwork with a mesh diameter of 0, 5-5 mm.

The technical effect of the claimed invention consists in greater selectivity, in providing a higher yield of target products of heterogeneous reactions, for example, in processes for the disposal of organochlorine wastes, purification of gaseous and liquid emissions from toxic organochlorine impurities, in the processes of oxidation of sulfur dioxide to trioxide, in the production of sulfuric acid and in the purification of sulfur-containing industrial gas emissions, in the processes of obtaining a valuable monomer - vinyl chloride from dichloroethane, in the processes of production from meta on and natural gas products such as methyl chloride, vinyl chloride, light olefins, and others.

The catalytic system for heterogeneous reactions contains a carrier and an active element and is a geometrically structured system of microfibers. Microfibers of the catalytic system can be structured in the form of a woven, non-woven or extruded material. The active component of the catalytic system is at least one of the elements selected from the group comprising platinum, palladium, rhodium, iridium, silver, zirconium, chromium, cobalt, nickel, manganese, copper, tin, gold, titanium, aluminum, iron , molybdenum, and / or their oxides, and / or their salts, the IR spectrum of ammonia adsorbed on the catalyst is characterized by the presence of characteristic absorption bands with wave numbers in the range ν = 1410-1440 cm ^-1 .

The presence of characteristic bands in the range ν = 1410-1440 cm ^-1 indicates the specific acidic properties of the proposed catalyst for heterogeneous reactions. The indicated properties of the catalyst can be formed during the preparation of the catalyst in various ways, for example, by introducing aluminum atoms into its composition as described in the well-known scientific and technical literature (RGRouxhet, RESempels // J.Chem.Soc.Farad.Trans.l. - v.70, 1974, pp.2021-2032).

Example 1

Vinyl chloride is produced from dichloroethane, for which vapors of dichloroethane are passed through a catalyst system. The catalytic system, structured in the form of a woven material, contains a high-siliceous fibrous carrier with a microfiber diameter of about 5-10 μm and an active component (platinum), and during preparation the system is modified by introducing aluminum atoms so that the IR spectra of adsorbed ammonia have characteristic bands in range ν = 1410-1440 cm ^-1 . In the temperature range of 400-550 ° C and a volumetric feed rate of the reaction mixture of 10-20 thousand hour ^{-1 the} selectivity of dichloroethane to vinyl chloride is achieved at a level of 94-98% at a dichloroethane conversion of about 80%. The only by-product in this case is acetylene, other substances are not detected at all when the sensitivity threshold of the analysis is not higher than 1 ppm. No coking and gumming of the catalytic system is observed. The experiment under these conditions for 60 hours shows the absence of a decrease in the activity and selectivity of the catalyst. The results indicate a high activity, selectivity and resistance to deactivation of the claimed invention.

Example 2

Dichloroethane is disposed of, for which dichloroethane vapors are mixed with air (the volume concentration of dichloroethane is 0.1-3.5%) and passed through a catalytic system. The catalytic system, structured in the form of a woven material, contains a high siliceous glass fiber carrier with a microfiber diameter of about 10 μm and an active component (platinum), and the system is modified in such a way that the IR spectra of adsorbed ammonia have characteristic bands in the range ν = 1410-1440 cm ^-1 . In the temperature range of 400-500 ° C and the volumetric feed rate of the reaction mixture of 16-18 thousand hours ^-1 , a complete conversion of dichloroethane to hydrogen chloride, water vapor and carbon dioxide is achieved. Other oxidation products (products of incomplete oxidation, elemental chlorine, CO, phosgene, dioxins) are not detected at all when the analysis sensitivity threshold is not higher than 1 ppm. This indicates a high activity and selectivity of the proposed catalytic system. The experiment under these conditions for 6 hours shows the absence of a decrease in the activity and selectivity of the catalytic system, which indicates its high stability. The use of a similar unmodified catalyst (which does not have these bands in the IR spectra of adsorbed ammonia) leads to the formation of significant amounts of undesirable by-products (chlorovinyl, CO). The use of other known catalysts also leads to the formation of undesirable by-products, in addition, they undergo a strong deactivation in these conditions.

Example 3

The oxidation of sulfur dioxide is carried out in a laboratory isothermal reactor, passing a mixture containing 10% (vol.) SO ₂ and 10% O ₂ (the rest is nitrogen) through a catalytic system. The catalyst system contains a glass fiber carrier with a microfiber diameter of about 10 μm (structured as a woven material) and an active component (platinum) and is modified so that the IR spectra of adsorbed ammonia have characteristic bands in the range ν = 1410-1440 cm ^-1 . At 300 ° C and a space velocity of the initial gas mixture of 4000 h ^-1 , a sulfur dioxide conversion of up to 61-71% is achieved. Under similar conditions, the method using the known platinum catalyst provides a conversion of not higher than 10-15%, the method using the vanadium catalyst is less than 1-2%.

Example 4

Natural gas containing at least 96% methane is chlorinated. For this, natural gas is mixed with elemental chlorine in a volume ratio of 2: 1 and at a temperature of 400 ° C and atmospheric pressure is passed through a catalytic system containing an active component (platinum) and a glass fiber woven carrier with a microfiber diameter of about 10 μm, the IR spectra of adsorbed ammonia have characteristic bands in the range ν = 1410-1440 cm ^-1 . A complete conversion of chlorine is observed, while the methane conversion is ~ 38%. The main product of chlorination is methyl chloride, and the selectivity of the conversion of methane to methyl chloride is 96%. The selectivity for the formation of undesired methylene chloride does not exceed 1%, polychlorinated hydrocarbons - not more than 4%, while undesirable chloroform, carbon tetrachloride, phosgene, carbon monoxide and dioxins are completely absent in the reaction products.

Example 5

The same as in example 4, but the process is carried out at a temperature of 450-500 ° C and a natural gas / chlorine ratio of 1: 1. Chlorine conversion - 100%, methane - about 80%. The formation of light olefins (ethylene, propylene) with a selectivity of up to 70%, as well as vinyl chloride with a selectivity of up to 15%, is observed. With an increase in the natural gas / chlorine ratio to a value of 4: 1, methane conversion decreases to ~ 25%, while the selectivity of olefin formation reaches almost 100%. The use of other known catalysts does not provide the indicated valuable products (olefins, vinyl chloride).

Example 6

Propane is subjected to chlorination on the indicated catalytic system, while the process is carried out at 160 ° C, atmospheric pressure and with an initial ratio of propane / chlorine / inert gas of 1: 1: 1. A conversion of propane of 55% is achieved, while the selectivity for the formation of monochloropropanes reaches 80%. When the reaction temperature rises above 350 ° С, monochloropropanes are converted to propylene with a selectivity close to 100%. The use of other known catalysts does not provide the indicated valuable products (monochloropropanes, propylene).

Example 7

Purify the exhaust gases of diesel engines by passing exhaust through the catalytic system. The catalytic system contains a glass fiber carrier (structured as a woven material) and an active component (platinum) and is modified so that the IR spectra of adsorbed ammonia have characteristic bands in the range of ν = 1410-1440 cm ^-1 . In the temperature range of 300-600 ° C and space velocities of 20,000-200,000 h ^{-1 the} conversion of hydrocarbons and CO is higher than 90%, the degree of reduction of nitrogen oxides is up to 70%. Under similar conditions, the method using the known platinum catalyst provides a conversion of nitrogen oxides of not more than 30-40%.

Example 8

Purify ventilation emissions of paint plants from toxic fumes of organic solvents by passing emissions through a catalyst bed. The catalyst system contains a glass fiber carrier with a microfiber diameter of 15 μm (structured as a pressed material) and an active component (platinum) and is modified so that the IR spectra of adsorbed ammonia have characteristic bands in the range ν = 1410-1440 cm ^-1 . In the temperature range of 250-600 ° C, a complete conversion of toxic organic impurities to harmless substances (water vapor, carbon dioxide) is achieved. Under similar conditions, the method using the known platinum catalyst ensures the conversion of impurities not higher than 95-97%.

Claims (3)

1. A catalytic system for heterogeneous reactions, including a highly siliceous fibrous carrier, characterized by the presence in the NMR spectrum of ²⁹ Si lines with chemical shifts of -100 ± 3 ppm (line Q ³ ) and -110 ± 3 ppm. (line Q ⁴ ) with a ratio of the integrated intensities of the lines Q ³ / Q ⁴ 0.7-1.2, in the infrared spectrum of the absorption band of hydroxyl groups with a wave number of ν = 3620-3650 cm ^-1 and a half-width of 65-75 cm ^-1 , having a specific surface area measured by the BET method for thermal desorption of argon, S _Ar = 0.5-30 m ² / g, surface area measured by the method of alkaline titration, S _Na = 10-250 m ² / g with the ratio S _Na / S _Ar = 5-30, and at least one active element, characterized in that it is a geometrically structured system of microfibers with a diameter of 5-20 microns and additionally has active centers, which are characterized in the IR spectra of adsorbed ammonia by the presence of an absorption band with wave numbers in the range ν = 1410-1440 cm ^-1 . 2. The catalytic system according to claim 1, characterized in that the active element is selected from the group comprising platinum, palladium, rhodium, iridium, silver, zirconium, chromium, cobalt, nickel, manganese, copper, tin, gold, titanium, aluminum, iron, molybdenum and / or their oxides, and / or their salts. 3. The catalytic system according to claim 1, characterized in that the microfibers are structured in the form of either non-woven or extruded material such as cotton wool or felt or threads with a diameter of 0.5-5 mm, or woven from threads with a material of weaving type satin, canvas, openwork with cell diameter 0.5-5 mm.