RU53184U1 - CATALYTIC SYSTEM FOR HETEROGENEOUS REACTIONS - Google Patents

Abstract

The invention relates to the field of chemical industry, to new catalysts that can be used, in particular, for the selective hydrogenation of polyunsaturated hydrocarbons, the deep oxidation of CO, organic and halogen-organic compounds, the oxidation of sulfur dioxide, the selective chlorination and oxychlorination of hydrocarbons, the reduction of nitrogen oxides and many others catalytic reactions. The invention can find application in the processes of obtaining and purifying valuable chemical products and intermediates, as well as in the processing and disposal of a variety of gaseous and liquid wastes.

The catalytic system for heterogeneous reactions is a geometrically structured system comprising microfibers of a high siliceous fibrous carrier with a diameter of 5-20 μm, which is characterized by the presence 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} has a specific surface area measured by the BET method for thermal desorption of argon, S _Ar = 0.5-30 m ² / g, and at least one active element. In this case, the carrier has a surface value measured by the alkaline titration method, S _Na = 5-150 m ² / g at a ratio of S _Na / S _Ar = 5-50, and the active element is configured to form charged metal or bimetal clusters characterized by UV-Vis spectrum of diffuse reflectance in specific bands 34000-42000 cm ^-1 and the ratio of the integrated intensity of the band attributable to the charged or metallic or bimetallic clusters to the integrated intensity of the band attributable respectively Or a metal or a bimetallic particles of at least 1.0. The claims contain 1 independent and 3 dependent clauses.

Description

The invention relates to the field of chemical industry, to new catalysts that can be used, in particular, for the selective hydrogenation of polyunsaturated hydrocarbons, the deep oxidation of CO, organic and halogen-organic compounds, the oxidation of sulfur dioxide, the selective chlorination and oxychlorination of hydrocarbons, the reduction of nitrogen oxides and many others catalytic reactions. The invention can find application in the processes of obtaining and purifying valuable chemical products and intermediates, as well as in the processing and disposal of a variety of gaseous and liquid wastes.

A known catalytic system for heterogeneous reactions, which is a geometrically structured system comprising microfibers of a high siliceous fibrous carrier with a diameter of 5-20 μm, which is characterized by the presence 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, has a specific surface area measured by the BET method of thermal desorption of argon, S _Ar = 0,5-30 m ² / g, BET surface area, as measured by alkali titration, S _Na = 10-250 m ² / g soot Ocean S _Na / S _Ar = 5-30, and at least one active element selected from the group consisting of platinum, palladium, rhodium, iridium, silver, zirconium, chromium, cobalt, nickel, manganese, copper, tin, gold (No. No. 2257952, 01 OJ 1/08, priority dated 12/26/03, published on 08/10/05, BI No. 22).

The disadvantages of the known catalytic system are relatively low activity, deactivation in aggressive reaction media, as well as low selectivity of transformations in a number of reactions, for example, in the processes of selective hydrogenation of polyunsaturated hydrocarbons, reduction of nitrogen oxides, chlorination and oxychlorination of hydrocarbons.

The authors were tasked with developing a catalytic system for heterogeneous reactions with higher activity, resistance to deactivation and increased selectivity in the oxidation of hydrocarbons, organochlorine compounds, sulfur dioxide,

oxidative dehydrogenation of light paraffins, selective chlorination of hydrocarbons, reduction of nitrogen oxides, selective hydrogenation of polyunsaturated hydrocarbons.

The problem is solved in that in a catalytic system for heterogeneous reactions, which is a geometrically structured system that includes microfibers of a highly siliceous fibrous carrier with a diameter of 5-20 μm, which is characterized by the presence in the infrared spectrum of the absorption band of hydroxyl groups with a wave number ν = 3620-3650 cm ^{- 1} and half-width 65-75 cm ^-1, having a specific surface area measured by the BET method of thermal desorption of argon, S _Ar = 0,5-30 m ² / g, BET surface area, as measured by alkali t trirovaniya, S _Na = 5-150 m ² / g at a ratio S _Na / S _Ar = 5-50, and at least one active element, the latter is configured to generate a charged metallic or bimetallic clusters, characterized in the UV-Vis specific diffuse reflection spectrum bands in region 34000-42000 cm ^-1 and the ratio of the integrated intensity of the band attributable to the charged or metallic or bimetallic clusters to the integrated intensity of the band attributable respectively to either metal or to the bimetallic m particles of at least 1.0. In this case, metal clusters are formed from atoms of either platinum or palladium, or rhodium, or iridium, or silver, or nickel, or copper, or tin, or gold, and bimetallic clusters are formed from a combination of atoms or palladium or platinum with atoms or silver, either cobalt, or nickel, or copper, or tin, or gold.

The technical effect of the claimed invention consists in a higher activity of the catalytic system and increased resistance to deactivation in aggressive environments in the oxidation, chlorination and oxychlorination reactions, as well as increased selectivity in the processes of selective hydrogenation of polyunsaturated hydrocarbons, reduction of nitrogen oxides, chlorination and oxychlorination of hydrocarbons.

This is due to the use of a catalytic system comprising either Pd, or Pt, or Rh, or Ir, or Ag, or Ni, or Cu, or Sn, or Au, supported on a highly siliceous fibrous carrier with the claimed set of physicochemical and geometric properties, which leads to the formation of the active element in the form of charged metal clusters Me ^{δ +} . In addition, the introduction of additional elements, such as Co, Ag, Ni, Cu, Sn, Au, etc., forms bimetallic clusters that differ from the monometallic clusters in the charge state.

The high-silica carrier proposed in the invention, comprising 50.0-98.8 wt.% Silicon dioxide, is characterized by a set of the following physicochemical properties:

- in the infrared spectrum there is an absorption band of hydroxyl groups with a wave number of 3620-3650 cm ^-1 and a half-width of 65-75 cm ^-1

- the carrier has a specific surface area measured by the BET method for thermal desorption of argon, S _Ar = 0.5-30 m ² / g and a surface value measured by the alkaline titration method, S _Na = 5.0-150 m ² / g, and the ratio S _Na / S _Ar = 5-50.

The combination of the claimed features indicates the specific structure of the fibrous carrier and the possibility of forming active states of the applied component on it. For example, the presence in the infrared spectrum of the absorption band of OH groups in the region of wave numbers 3620-3650 cm ^-1 and the small half-width of this band indicates the presence in the carrier of a significant amount of OH groups located not on the external surface, as for traditional silica gels, but in small and cavities quite homogeneous in geometry. Similar bands are described in the literature for silicate materials containing OH groups in the volume of globules or in very small pores (Euler R. Chemistry of silica. M: Mir, 1982. V.2. P.870. Chukin G.D., Apretova A. I., Silverstova I.V. // Kinetics and Catalysis 1994. T.35. S.426.) In addition, in this invention there are large differences in the specific surface area measured by the BET method for the physical adsorption of argon S _Ar = 0 , 5-30 m ² / g and Sears method for the chemisorption of charged particles - sodium cations S _Na = 5.0-150 m ² / g (GWSears // Anal. Chem. - 1956. - V.28. - p. 1981 .. R. Euler. Silica Chemistry. - M .:

Mir, 1982.- T.2. - S.480.), A significant excess of the surface area measured by sodium chemisorption S _Na , the specific surface area determined by the BET method for physical adsorption of argon, S _Na / S _Ar = 5-50, indicates the presence of active centers in the fibrous carrier for chemisorption of charged particles - Na ⁺ cations (diameter ~ 1.4A) and limited Ar molecules for physical adsorption.

The presence of these signs can lead to the formation of highly active states of the deposited metal, in the form of charged metal clusters Me ^{δ +} , characterized in the UV-type diffuse reflection spectrum by a specific band of 34000-42000 cm ^-1 Moreover, the fraction of charged clusters should be quite large: the ratio of the integrated intensity of the band is 34000 -42000 cm ^-1 related to charged metal clusters, to the integrated intensity of the band with a maximum at 48000 cm ^-1 related to metal particles, must be at least 1, I _clt / I _met ≥1.0. The formation of bimetallic clusters slightly affects the I _cl / I _met ratio, but leads to a change in the charge state of the clusters, which manifests itself in a shift of the band maximum 34000-42000 cm ^-1 to the low frequency region with increasing charge due to the interaction of platinum or palladium atoms with ions of the second metal .

Highly siliceous fibrous carrier contains 50-98.8 wt.% SiO ₂ and at least one element selected from the group including alkaline, alkaline earth, rare earth elements, aluminum, iron, molybdenum, titanium, zirconium, chromium, manganese.

The presence of the claimed promoters in the carrier changes the composition and structure of the immediate environment of the applied active elements of palladium and platinum and, accordingly, can additionally affect their properties: the size and electronic state (charge value) of the clusters. For example, the interaction of Pd and Ce reduces the absorption maximum observed for palladium in the UV spectra from 41,000 cm ^-1 to 38,000 cm ^-1 This leads to an increase in the specific catalytic activity of Pd in various reactions by several times (for example, in the acetylene hydrogenation reaction - by 2, 5 times).

Microfibres of high siliceous carrier with a diameter of 5-20 microns should be structured in the form of non-woven or pressed

material such as cotton wool and felt, or in the form of threads with a diameter of 0.5-5.0 mm, or in the form of fabrics from these threads with weaving such as satin, linen, mesh with a mesh size of 0.5-5.0 mm. Such a geometric structure ensures the absence of diffusion difficulties for heat and mass transfer and can make an additional contribution to an increase in activity and selectivity. In addition, geometric structuring improves the technological parameters of the reaction: it increases the permeability of the catalyst layer, reduces its hydraulic resistance, which is important to achieve a high volumetric flow rate, and, consequently, high productivity of the industrial process.

In combination with the above active states of the introduced active element, this can lead to a higher activity of the catalytic system and its increased resistance to deactivation in aggressive environments in the oxidation, chlorination and oxychlorination reactions, as well as increased selectivity in the processes of selective hydrogenation of polyunsaturated hydrocarbons, reduction of nitrogen oxides, chlorination and oxychlorination of hydrocarbons.

The catalytic system used in the claimed invention can be prepared, for example, by impregnation of a high-silica fibrous carrier with the claimed properties by aqueous solutions of salts of active elements, followed by removal of the impregnation solution and heat treatment of the catalytic system in air or in hydrogen, or in an inert atmosphere.

The modifier elements included in the carrier are selected from the group consisting of alkaline, alkaline earth, rare earth elements, aluminum, iron, molybdenum, titanium, zirconium, chromium, manganese are introduced into the fibrous carrier either at the carrier preparation stage or immediately before the introduction of the active elements.

Examples of the use of the inventive catalytic system:

Example 1

Selective hydrogenation of the ethylene-acetylene mixture is carried out, for which a gas mixture containing 1% acetylene, 1.6% hydrogen, 97.4%

ethylene (ethylene / acetylene ratio = 97.4), passed through a catalytic system at 100 ° C and a space velocity of 5000 h ^-1 .

The support of the catalytic system is characterized by the presence in the infrared spectrum of the absorption band of hydroxyl groups with a wave number of ν = 3630 cm ^-1 and a half-width of 70 cm ^-1 . The carrier has a specific surface area measured by the BET method for thermal desorption of argon, S _Ar = 1-2 m ² / g, surface area measured by the alkaline titration method, S _Na = 26 m ² / g and the ratio S _Na / S _Ar = 21.7. The catalytic system contains 0.02 wt% Pc), with the bulk of palladium present in the form of charged clusters Pd ^{δ +} 0 <δ <2, which are characterized by a band with a maximum of 38,000 cm ^-1 in the UV-type diffuse reflection spectrum. The ratio of the integrated intensity of the band with a maximum at 38000 cm ^-1 related to charged palladium clusters to the integrated intensity of the band with a maximum at 48000 cm ^-1 related to metallic palladium particles is 1 (I _cl / I _met = 1.0).

The catalyst system carrier is a microfibre of a high siliceous carrier comprising 95.8 wt% SiO ₂ , as well as 1.55 wt% Al, 0.04 Mac% Fe, 0.08 Mac% Na, 0.5 wt% Ca, 0.3 wt% Mg. The support has a net weave fabric structure in which fibers with a diameter of 10 μm are spun into strands with a diameter of 1.5 mm, of which a mesh with a square mesh of 3.0 × 3.0 mm and aperture size of 1.5 × 1.5 mm is woven.

The sample according to example 1 showed a high conversion of acetylene of 88.2% and an increase in the concentration of ethylene in the reaction products by 0.72%. The absence of ethylene losses indicates a high selectivity for the hydrogenation of acetylene to ethylene, without subsequent hydrogenation of ethylene to ethane.

Example 2

Dichloroethane is recycled, for which vapors of dichloroethane are mixed with air (the volume concentration of dichloroethane is 0.1-3.5%) and passed through a catalyst bed. A catalytic system structured in the form of a woven material contains about 0.05% platinum, with most of the platinum present in the form of charged clusters Pt ^{δ +} 0 <δ <2, which are characterized in the UV-type diffuse reflection spectrum

strip with a maximum of 38,000 cm ^-1 . The ratio of the integrated intensity of the band with a maximum at 38000 cm ^-1 related to charged platinum clusters to the integrated intensity of the band with a maximum at 48000 cm ^-1 related to metal particles of platinum is 1.5 (I _cl / I _met = 1.5).

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 when the analysis sensitivity threshold is at least 1 ppm, which indicates the high activity and selectivity of the proposed catalyst system. The experiment under these conditions for 60 hours shows the absence of a decrease in the activity and selectivity of the catalytic system, which indicates the high stability of the proposed catalyst.

The use of a known catalyst containing platinum mainly in a metallic form (the ratio of the integrated intensity of the band with a maximum at 38000 cm ^-1 related to charged platinum clusters to the integrated intensity of the band with a maximum at 48000 cm ^-1 related to metal particles of platinum is 0.6), leads to the formation of significant quantities of undesirable by-products (chlorovinyl, CO), as well as to a noticeable deactivation of the catalyst. 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. A catalytic system structured in the form of a woven material contains 0.1% platinum, with most of the platinum present in the form of charged clusters Pt ^{δ +} 0 <δ <2, which are characterized by a band with

a maximum of 38,000 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 70% 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 traditional vanadium catalyst less than 1-2%.

Example 4

Natural gas containing 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 200-400 ° C and atmospheric pressure is passed through a catalytic system containing the active component - platinum in an amount of 0.05 wt%, and the main part of platinum is present in the form charged clusters Pt ^{δ +} 0 <δ <2, which are characterized in the UV-type spectrum of diffuse reflection by a band with a maximum of 38000 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 of the formation of undesired methylene chloride does not exceed 4%, polychlorinated hydrocarbons - not more than 1%, while undesirable chloroform, carbon tetrachloride, phosgene, carbon monoxide and dioxins are completely absent in the reaction products.

Example 5

Purify the exhaust gases of diesel engines by passing exhaust through the catalytic system. The catalytic system contains a fibrous carrier (structured in the form of a plain weave fabric with a thread diameter of 0.5 mm) and an active component of platinum in an amount of 0.03 wt.%, With most of the platinum present in the form of charged clusters Pt ^{δ +} 0 <δ < 2, which are characterized in the UV-type diffuse reflection spectrum by a band with a maximum of 38,000 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%. In similar conditions, the method using the known

a platinum catalyst provides a conversion of nitrogen oxides of not more than 30-40%.

Example 6

Purify ventilation emissions of paint plants from toxic fumes of organic solvents by passing emissions through a catalyst bed. The catalytic system contains a fibrous support (structured in the form of a grid with a square cell of 1.5 × 1.5 mm) and an active component of platinum in an amount of 0.02 wt.%, With most of the platinum present in the form of charged clusters Pt ^{δ +} 0 < δ <2, which are characterized in the UV-type diffuse reflection spectrum by a band with a maximum of 38000 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 (4)

1. The catalytic system for heterogeneous reactions, which is a geometrically structured system comprising microfibers of a high siliceous fibrous carrier with a diameter of 5-20 μm, which is characterized by the presence 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 , has a specific surface area measured by the BET method for thermal desorption of argon, S _Ar = 0.5-30 m ² / g, and at least one active element, characterized in that the carrier has a surface ty measured by the alkaline titration method, S _Na = 5-150 m ² / g with the ratio S _Na / S _Ar = 5-50, and the active element is configured to form charged either metal or bimetallic clusters characterized in the UV-type spectrum diffuse reflection bands in specific 34000-42000 cm ^-1 and the ratio of the integrated intensity of the band attributable to the charged or metallic or bimetallic clusters to the integrated intensity of the band corresponding respectively to either a metal or a bimetallic m particles is not less than 1.0. 2. The catalytic system for heterogeneous reactions according to claim 1, characterized in that the metal clusters are formed from atoms of either platinum, or palladium, or rhodium, or iridium, or silver, or nickel, or copper, or tin, or gold. 3. The catalytic system for heterogeneous reactions according to claim 1, characterized in that the bimetallic clusters are formed from a combination of atoms of either palladium or platinum with atoms, or silver, or cobalt, or nickel, or copper, or tin, or gold. 4. The catalytic system for heterogeneous reactions according to claim 1, characterized in that the high-siliceous fibrous carrier contains 50-98.8% SiO ₂ , and at least one element selected from the group comprising metals aluminum, iron, molybdenum, titanium, zirconium , chromium, manganese, alkaline, alkaline earth and rare earth elements.