RU2299190C1 - Light paraffin oxidative dehydrogenation process - Google Patents

Abstract

FIELD: petrochemical processes.

SUBSTANCE: feed stream is passed with admixed oxygen and diluent through catalyst bed at 400-500°C and constant flow rate 50 mL/min, said catalyst being catalytic system for heterogeneous reactions and representing geometrically structured system including microfibers of high-silica fibrous carrier, which is characterized by presence in IR absorption band of hydroxyl groups with wave number ν=3620-3650 cm^-1 and half-width 65-75 cm^-1. The carrier has specific surface as measured according to BET method from heat desorption of argon S_Ar=0.5-30 m²/g, surface area as measured by alkali titration method S_Na=5-150 m²/g at ratio S_Na/S_Ar=5-50, and at least one active element, whose principal portion is composed in the form of charged either metallic, or bimetallic clusters characterized in UV-vis diffuse reflection spectrum by specific bands in the region 34000-42000 cm^-1 and ratio of integral intensity of band attributed to charged either metallic, or bimetallic clusters to integral intensity of band belonging to, respectively, either metallic, or bimetallic particles is not less than 1.0.

EFFECT: increased choice of oxidative dehydrogenation catalysts.

4 cl, 5 ex

Description

The invention relates to the field of chemistry, and in particular to methods of oxidative dehydrogenation of light paraffins.

The research area developing the processes of oxidative dehydrogenation of light paraffins is based on the fact that the chemical industry is heavily dependent on the availability of feedstock containing propylene and other olefins. For example, according to official estimates, the demand for propylene increased by 4.5% annually between 1991 and 2000.

Olefins are obtained by thermal cracking of hydrocarbons and by dehydrogenation and oxidative dehydrogenation of paraffins. Catalytic oxidative dehydrogenation (OD) is the most attractive way to produce olefins for several reasons. Unlike thermal cracking, catalytic OD is a thermodynamically resolved process at low temperatures. In addition, unlike catalytic dehydrogenation, oxidative dehydrogenation minimizes catalyst deactivation due to coking due to the presence of oxygen in the initial reaction mixture.

There is a method of oxidative dehydrogenation of light paraffins, namely ethane, using catalysts consisting of a mixture of molybdenum, vanadium and transition metal oxides (E.M. Thorsteinson et al., "The Oxidative Dehydrogenation of Ethane over Catalyst Containing Mixed oxide of Molybdenum and Vanadium , "J. Catalysis, 1978, v. 52, p. 116).

There is also known a method of oxidative dehydrogenation of light paraffins, which use vanadium-containing oxide catalysts supported on alumina, the composition of which is determined by the formulas MV and MVSb, where M is Ni, Co, Bi and Sn (R. Juarez Lopez et al., "Oxidative Dehydrogenation of Ethane on Supported Vanadium-Containing Oxides, "Applied Catalysis A: General, 1995, v. 124, p. 281).

There is also a known method for oxidative dehydrogenation of light paraffins, which uses a catalyst containing unsupported oxides of iron, cobalt and nickel, which are active in the oxidative dehydrogenation of ethane (Y.Schuurman et al., "Low Temperature Oxidative Dehydrogenation of Ethane over Catalysts Based on Group VIII Metals, "1997, Applied Catalysis A: General, v. 163, p. 227).

A disadvantage of the known methods is the insufficiently high activity of the catalysts and the associated need for the process at a high temperature, which requires high energy consumption and leads to low selectivity for the conversion of the starting paraffin. These disadvantages hinder the industrial use of processes based on these catalysts.

The activity of oxide catalysts increases as a result of the introduction of platinum metals into their composition.

A known method of oxidative dehydrogenation of light paraffins, mainly isobutane, n-butane, propane, comprising converting paraffin to olefin in the presence of oxygen using a catalyst consisting of a platinum group metal, mounted on a carrier, selected as a prototype (US Patent RE37663, "Catalysis ", B01J 023/00, publ. 16.04.2002). The dehydrogenation process is carried out at a temperature of about 450-550 ° C. The catalyst is Pt supported on a carrier consisting of a mixture of tin oxide and zirconium oxide. The content of Pt varies from 0.1 wt.%. up to 3 wt.%. This method of dehydrogenation of paraffins differs in one or several indicators, such as a high yield of olefins, high selectivity for the formation of olefins, low reaction temperature, simplicity of the system, and poor catalyst deactivation.

The disadvantage of this method is the high cost of the catalyst due to the high content of platinum metal, namely platinum.

The authors were tasked with developing a method for the oxidative dehydrogenation of light paraffins, the cost of which would be lower due to the use of a catalyst with a lower weight content of platinum, providing a high yield and selectivity in the reactions of oxidative dehydrogenation of light paraffins.

The problem is solved in that in a method of oxidative dehydrogenation of light paraffins, including passing a stream of a mixture with oxygen and a diluent through a catalyst bed at a temperature of 400-500 ° C, at a constant speed of 50 ml / min, a catalyst system for heterogeneous reactions is used as a catalyst, which is a geometrically structured system including microfibres of a high siliceous fibrous carrier, which is characterized by the presence in the infrared spectrum of the absorption band of hydroxyl groups Nos with the wave number ν = 3620-3650 cm ^-1 and half-width 65-85 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 = 5-150 m ² / g with the ratio S _Na / S _Ar = 5-50, and at least one active element, the main part of which is formed in the form of charged either metal or bimetallic clusters, characterized in UV View of the diffuse reflectance spectrum with specific bands in the region 34000-42000 cm ^-1 and the ratio of the integrated intensity the bandwidth corresponding to charged either metal or bimetallic clusters, to the integrated intensity of the band, corresponding, respectively, to metal or bimetallic particles, not less than 1.0. In this case, metal clusters are formed from atoms of either platinum or palladium, or rhodium, or iridium, or silver, or zirconium, or chromium, or cobalt, or nickel, or manganese, or copper, or tin, or gold, and bimetallic clusters are formed from a combination of atoms of either palladium or platinum with atoms of either silver or zirconium or chromium or cobalt or nickel or manganese or copper or tin or gold. In addition, microfibers of a high-siliceous fibrous carrier are made with a diameter of 5-20 μm, contain 50-98.8% SiO ₂ , and at least one element selected from the group comprising metals titanium, aluminum, iron, molybdenum, alkaline, alkaline earth and rare earth elements.

The technical effect of the proposed method lies in the fact that the oxidative dehydrogenation reactions of light paraffins take place at relatively low temperatures using a cheap catalyst, the low cost of which is due to the low metal content, which allows it to be used in industry.

The inventive method is as follows.

To implement the method, the initial reaction mixture containing one or more light paraffins, oxygen and a diluent, is passed through a catalyst bed, which is a geometrically structured system comprising microfibers of a high silica fibrous carrier and an active element. A high-siliceous fibrous carrier 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 , which has a specific surface area measured by the BET method for thermal desorption of argon, S _Ar = 0.5-30 m ² / g, the surface value measured by the method of alkaline titration, S _NA = 5-150 m ² / g at a ratio of S _Na / S _Ar = 5-50 , contains 50-98.8% SiO ₂ and at least one element selected from the group consisting of titanium, aluminum, iron, molybdenum, alkaline, alkaline earth and rare earth Wowed items. The main part of the active component is formed in the form of charged either metal or bimetallic clusters, characterized in the UV-type diffuse reflection spectrum by specific bands in the region of 34000-42000 cm ^-1 and the ratio of the integrated intensity of the band related to charged either metal or bimetallic clusters to the integral intensity of the band, corresponding, respectively, to either metallic or bimetallic particles, is not less than 1.0. Metal clusters are formed from atoms of either platinum or palladium or rhodium or iridium or silver or zirconium or chromium or cobalt or nickel or manganese or copper or tin or gold. And bimetallic clusters are formed from a combination of atoms of either palladium or platinum with atoms of either silver or zirconium or chromium or cobalt or nickel or manganese or copper or tin or gold.

The catalytic system is prepared by treating the surface of a silicate material with complex metal compounds or inorganic or organic metal salts. For example, in the case of palladium, it can be palladium (II) chloride, nitrate or sulfate, palladium (II) tetrammine chloride. In the case of platinum, platinum chloride, potassium tetrachloroplatoate, tetramine platochloride can be used.

Conventional application methods are used, in particular, impregnation, adsorption, and precipitation procedures can be used. The application procedure can be carried out once or several times. After drying, the carrier with the active component is subjected to heat treatment at a temperature of 100-600 ° C either in air or in a stream of nitrogen, and then kept in a stream of hydrogen or a gas containing hydrogen at a temperature of 100-300 ° C.

Finished catalytic systems contain 0.001-0.01 wt.% Platinum metal, which is significantly lower than the platinum content in the catalyst of the prototype.

Platinum metals are found in large part in the form of clusters, giving a band in the UV spectrum in the region of 34000-42000 cm ^-1 . The presence of such clusters ensures a high activity of the catalytic system in the oxidative dehydrogenation of paraffins.

The proposed method allows for the oxidative dehydrogenation of paraffins with the formation of alkenes. Oxidative dehydrogenation is carried out in a flow reactor with a catalytic system disposed therein. The microfiber structure of the high-siliceous carrier simplifies the placement and fixing of the catalytic system in the reactor, provides effective contact of the catalytically active surface with the flow of reagents, and prevents the entrainment of particles with the flow of reagents.

The reagent stream in contact with the catalyst system contains gaseous paraffin or paraffin vapor, oxygen in an amount of 1-10 vol.% And a diluent in an amount of 0-10%. The diluent may be nitrogen, hydrogen, or water vapor.

The method can be carried out at a temperature of 400-500 ° C. Both high and too low temperatures adversely affect system performance.

At low temperatures, the catalyst system may exhibit low activity. High temperature is unfavorable for the reaction, since it causes deep oxidation of paraffins with the formation of carbon oxides and, thus, leads to unproductive consumption of paraffins.

Oxidative dehydrogenation usually occurs at atmospheric pressure, but can be carried out at elevated pressure.

The volumetric velocity of the gas mixture is 50 ml / min.

The advantage of the proposed method is the high activity of the catalytic system with a reduced platinum content compared to the prototype. The essential features of the proposed method provide its cost reduction in comparison with the prototype, which allows its use in industry.

Example 1

The method of oxidative dehydrogenation of propane is carried out by passing a stream of a mixture of 95% propane with 5% oxygen through a catalyst (1 g) at a temperature of 400-500 ° C, at a constant speed of 50 ml / min. As a catalyst, a catalytic system for heterogeneous reactions is used, which is a geometrically structured system including microfibers of a high siliceous fibrous carrier with a diameter of 20 μm, consisting of 97.2 wt% SiO ₂ , 0.12 wt% Na, 1.4 wt% Al, which are characterized by the presence in the infrared spectrum of the band absorption of hydroxyl groups with a wave number ν = 3620 cm ^-1 and a half-width of 75 cm ^-1 has a specific surface area measured by the BET method for thermal desorption of argon, S _Ar = 1.2 m ² / g, the surface alkaline titration method, S _Na = 5.5 m ² / g at a ratio of S _Na / S _Ar = 5. The catalytic system contains 0.005 wt.% Pt, the main part of which is formed in the form of a cluster having a specific band with a maximum at 36,000 cm ^-1 in the UV-type diffuse reflection spectrum. The ratio of the integrated intensity of the band related to charged clusters (I _clt ) to the intensity of the band due to metal particles (I _met ) is 2 (I _met = 0.95). According to the result of chromatographic analysis of the gas at the outlet of the reactor, the propylene yield is 7 mol%.

The prototype catalyst containing 1 wt.% Pt, under the same conditions in the oxidative dehydrogenation of propane gives a propylene yield of from 12 to 19%.

Example 2

The method of oxidative dehydrogenation of propane is carried out by passing a stream of a mixture of 95% isobutane with 5% oxygen through a catalyst (1 g) at a temperature of 400-500 ° C, at a constant speed of 50 ml / min. As a catalyst, a catalytic system is used, for which the carrier parameters are described in Example 1, containing 0.005 wt.% Pd and having a specific band with a maximum at 35,000 cm ^-1 in the UV-Diffuse reflectance spectrum. The ratio of I _clast / I _met = 1.2. The yield of isobutylene is 4 mol.%.

Example 3

The method of oxidative dehydrogenation of propane is carried out by passing a mixture of 85% propane, 5% oxygen and 10% water through a catalyst (1 g) at a temperature of 400-500 ° C, at a constant speed of 50 ml / min. As a catalyst, a catalytic system is used, for which the parameters of the support are described in Example 1, containing 0.005 wt.% Pt and 0.002 wt.% Au and having a specific band in the UV diffuse reflectance spectrum with a maximum at 38000 cm ^-1 . The ratio of I _clast / I _met = 1.2. The propylene yield is 12 mol%.

Example 4

The method of oxidative dehydrogenation of propane is carried out as described in Example 1. As a catalyst, a catalytic system is used, for which the carrier parameters are described in Example 1, containing 0.005 wt.% Pt and 0.05 wt.% Cu and having a specific diffuse reflection spectrum in the UV-type a strip with a maximum at 40500 cm ^-1 . The ratio of I _clast / I _met = 1.2. According to the result of chromatographic analysis of the gas at the outlet of the reactor, the propylene yield is 13 mol%.

Example 5

The method of oxidative dehydrogenation of propane is carried out as described in Example 1. As a catalyst, a catalytic system for heterogeneous reactions is used, which is a geometrically structured system comprising microfibers of a high siliceous fibrous carrier with a diameter of 5 μm, consisting of 96.2 wt.% SiO ₂ , 0.008 wt.% Na, 0.09 wt.% Al and rare earth elements: 0.31 wt.% La, 0.26 wt.% Y, 0.91 wt.% Ce, 0.39 wt.% Pr, 0.17 wt.% Nd, 0.17 wt.% Sm, 0.69 wt.% Er, which is characterized by the presence in the infrared spectrum of the absorption band g droksilnyh groups with the wave number ν = 3650 cm ^-1 and half-width of 70 cm ^-1, has a specific surface area measured by the BET method of thermal desorption of argon, S _Ar = 0.5 m ² / g, BET surface area, as measured by alkali titration, S _Na = 5 m ² / g with a ratio of S _Na / S _Ar = 10, and 0.005 wt.% Pd, the main part of which is formed as a cluster having a specific band with a maximum at 36,000 cm ^-1 in the UV diffuse reflectance spectrum. The ratio of the integrated intensity of the band related to charged clusters (I _clt ) to the intensity of the band due to metal particles (I _met ) is 1.4.

The propylene yield is 3 mol%.

Claims (4)

1. The method of oxidative dehydrogenation of light paraffins, comprising passing a stream of a mixture with oxygen and a diluent through a catalyst bed at a temperature of 400-500 ° C, at a constant speed of 50 ml / min, characterized in that the catalyst system is used for heterogeneous reactions, representing a geometrically structured system comprising microfibers of a high siliceous fibrous carrier, which is characterized by the presence in the infrared spectrum of the absorption band of hydroxyl groups with a wave number v = 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, the surface value measured by the method alkaline titration, S _Na = 5-150 m ² / g with a ratio of S _Na / S _Ar = 5-50, and at least one active element, the main part of which is formed in the form of charged either metal or bimetallic clusters characterized in UV -type spectrum in 34000-42000 specific diffuse reflection bands cm ^-1 and the integrated intensity ratio five bands relating to charged either metallic or bimetallic clusters to the integrated intensity of the band attributable respectively to either the metal or bimetallic particles to not less than 1.0. 2. The method of oxidative dehydrogenation of light paraffins 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 zirconium, or chromium, or cobalt, or nickel, or manganese , or copper, or tin, or gold. 3. The method of oxidative dehydrogenation of light paraffins according to claim 1, characterized in that the bimetallic clusters are formed from a combination of atoms of either palladium or platinum with atoms of either silver or zirconium or chromium or cobalt or nickel or manganese or copper, either tin or gold. 4. The method of oxidative dehydrogenation of light paraffins according to claim 1, characterized in that the microfibers of a high siliceous fibrous carrier are made with a diameter of 5-20 μm, contain 50-98.8% SiO ₂ , and at least one element selected from the group including metals titanium, aluminum, iron, molybdenum, alkaline, alkaline earth and rare earth elements.