A method for preparing propylene by oxidative dehydrogenation of propane and catalyst used therein

Abstract

The present invention relates to a method for preparing propylene by oxidative dehydrogenation of propane. The method uses propane as a reactant, CO2 as an oxidant, and propylene is prepared by oxidative dehydrogenation reaction under the catalytic action of a supported silicon oxide-cerium oxide composite catalyst. Its reaction conditions are as follows: the reaction is carried out in a fixed bed reactor, the reaction is carried out at normal pressure, the reaction temperature is 450-650°C, the feed space velocity of propane is 500-2000mL / (g·h), and C3H8:CO2=1:1-1:4. The method catalyst is simple to prepare and efficiently catalyzes the reaction, CO2 replaces oxygen in the prior art as an oxygen source, avoids excessive oxidation, improves product selectivity, and the propane conversion rate reaches 55%, and the propylene selectivity reaches 65%.

Description

Technical Field

[0001] The present invention relates to a method for preparing propylene by oxidative dehydrogenation of propane, and in particular to a technology for preparing propylene by oxidative dehydrogenation using propane and CO2 as reactants. Background Art

[0002] Propylene is a very important chemical raw material that can be used to produce high value-added products such as polypropylene, acrylonitrile, and resin. With the rapid growth of the global economy, the supply of secondary commodities produced from propylene is far from enough, which has led to an urgent demand for propylene worldwide. Propylene mainly comes from four processes: 1) catalytic cracking; 2) the co-production process of ethylene from naphtha cracking; 3) catalytic propane dehydrogenation; 4) methanol to olefins. Among them, the catalytic propane dehydrogenation route needs to be further studied and developed. Propane comes from natural gas and petroleum refining by-products, but most of it will be used as fuel and emptied, which is a serious waste of resources. Therefore, reacting propane to produce propylene is an effective way to utilize resources.

[0003] The catalytic dehydrogenation of propane to propylene can be mainly divided into two processes: direct dehydrogenation of propane and oxidative dehydrogenation of propane. Although the direct dehydrogenation of propane has been industrialized, it is a highly endothermic reaction, so propane must react under high temperature conditions (>700°C), and it is easy to over-dehydrogenate and form carbon deposits. In comparison, the oxidative dehydrogenation of propane is an exothermic reaction. Oxygen and hydrogen on the CH bond in propane react to form water, which overcomes the problem of strong endothermicity and can inhibit catalyst carbon deposition and deactivation. However, the presence of oxygen will cause catalytic combustion of alkanes and olefins, resulting in a low propylene yield. Therefore, controlling the oxidative dehydrogenation process of propane, realizing selective oxidative dehydrogenation of propane, inhibiting deep oxidation and improving olefin selectivity are the key issues of oxidative dehydrogenation of propane to propylene. Carbon dioxide, as a mild oxidant, oxidizes propane to dehydrogenate propylene, and inhibits deep oxidation of propane, which can achieve the selective production of propylene. The development of this project is expected to provide a theoretical basis for improving the current situation of propylene shortage.

[0004] At present, the catalytic systems used for the dehydrogenation of propane by CO2 to produce propylene mainly include: indium oxide or gallium-based systems (In or Ga), chromium-based systems (Cr), vanadium-based systems (V) and supported metal catalytic systems (Fe / CeO2, FeNi / CeO2), etc. The research on the catalytic system for the dehydrogenation of propane by CO2 to produce propylene has made great progress, but there are still some problems: for example, the Ga and In systems follow a two-step cascade mechanism and still cannot avoid the problem of carbon deposition; the Cr system has high catalytic activity, but the catalytically active Cr6+ species are highly toxic and environmentally unfriendly; the single active component has insufficient adjustable space; in contrast, by regulating multiple factors such as the composition and chemical state of the supported metal and the properties of the carrier, the catalytic interface properties can be regulated within a certain range, and it is expected to achieve the co-activation of CO2 and propane and obtain a highly active catalyst. Therefore, it is of great significance to design and prepare an efficient catalytic system to achieve an efficient catalytic dehydrogenation of propane to produce propylene. Summary of the invention

[0005] The significance of the present invention is that it overcomes the shortcomings existing in the current propane oxidative dehydrogenation process. The catalyst in the process has high catalytic activity, high stability, simple reaction process and high yield of product propylene.

[0006] The propane oxidative dehydrogenation to propylene disclosed by the present invention is prepared by the following scheme: the process of the propane oxidative dehydrogenation to propylene is as follows: propane and CO2 are used as raw materials, reacted in a fixed bed reactor, and the reaction tube is filled with a supported silica-cerium oxide composite catalyst and then placed in a fixed bed reactor, and the reaction temperature is 450-650°C. The supported silica-cerium oxide composite catalyst comprises an active metal, a silica matrix, cerium oxide and an auxiliary agent; the supported silica-cerium oxide composite catalyst, wherein the active metal is one, two or more of Fe, Co, Ni, Cu, Pd, Zn and Mn; the preferred active metal is one or more of Fe, Ni, Zn and Mn; the content of cerium oxide in the supported silica-cerium oxide composite catalyst is 5.0%-50%; the auxiliary agent is one or more of alkali metals and alkaline earth metals;

[0007] The supported silicon oxide-cerium oxide composite catalyst has an active metal content of 0.05wt% to 5.0wt% and an auxiliary agent content of 0.05wt% to 1.0wt%. The supported silicon oxide-cerium oxide composite catalyst and the silicon oxide-cerium oxide carrier are prepared by co-hydrolysis of organic silane or tetraethyl orthosilicate and a cerium precursor salt, the hydrolysis is carried out at room temperature, and the concentration of the cerium salt is 0.1 to 1.1 mol / L; the concentration of the organic silane or tetraethyl orthosilicate is 1 to 10 mol / L; the pH is 8 to 11; the active metal is introduced by an impregnation method; In the supported silicon oxide-cerium oxide composite catalyst, the preferred content of active metal is 1.0wt% to 2.0wt%; the preferred content of cerium oxide is 20% to 30%; the content of auxiliary agent is 0.05wt% to 1.0wt%; the preferred reaction temperature is 450 to 550°C, the feed space velocity of propane is 500 to 2000mL / (g·h), and propane:CO2 is 1:1 to 1:4; the optimal reaction temperature is 500 to 550°C, the feed space velocity of propane is 600 to 1000mL / (g·h), and propane:CO2 is 1:2 to 1:4.

[0008] The method for preparing propylene by oxidative dehydrogenation of propane disclosed in the present invention has the following characteristics: (1) CO2 is used as an oxidant to replace oxygen as an oxidant in the traditional process, thereby avoiding excessive oxidation of oxygen and improving the selectivity of propylene; (2) a composite catalyst is used as a catalyst, with silicon oxide-cerium oxide as a matrix, and the particle size of cerium oxide particles at high temperature is effectively controlled through the physical isolation effect of silicon oxide to form unsaturated cerium oxide nano-islands, promote the formation of oxygen vacancies in the cerium oxide catalyst, adsorb and dissociate CO2, and at the same time introduce active metals as dehydrogenation sites, and utilize the synergistic effect of the synergistic double sites to obtain a high-activity and high-stability catalytic system.

[0009] The present invention has the following advantages: (1) the reaction process is simple, and the catalyst activity and stability are both high; (2) the reaction conditions are relatively mild, and the energy consumption is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a transmission electron microscope photograph of the 30wt% CeO2-SiO2 matrix in Example 1. DETAILED DESCRIPTION

[0011] Example 1

[0012] Preparation of 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / 30wt%CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 70wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C, and obtain 30wt%CeO2-SiO2, wherein cerium oxide is nanoparticles with an average size of 5nm (attached Figure 1 ); Fe, Ni, and Cs were introduced by impregnation method: 54 mL of 10 mmol / L ferric nitrate aqueous solution, 17 mL of 10 mmol / L nickel nitrate aqueous solution, and 7.6 mL of 1.0 mmol / L cesium nitrate aqueous solution were co-impregnated, stirred at room temperature, 2 g of the above 30 wt% CeO2-SiO2 matrix was added, stirring was continued for 4 hours, evaporated at 100°C, and calcined at 400°C for 4 hours to obtain 1.5 wt% Fe-0.5 wt% Ni-0.05 wt% Cs / 30 wt% CeO2-SiO2 catalyst.

[0013] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 800 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 55%, and the selectivity of propylene is 65%.

[0014] Example 2

[0015] Preparation of 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / 30wt%CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 70wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C, and obtain 30wt% CeO2-SiO2, in which cerium oxide is nanoparticles with an average size of 5nm; introduce Fe, Ni, and Cs by impregnation method: take 54mL 10mmol / L ferric nitrate aqueous solution, 17mL of 10mmol / L nickel nitrate aqueous solution and 7.6mL of 1.0mmol / L cesium nitrate aqueous solution were co-impregnated and stirred at room temperature. 2g of the above-mentioned 30wt% CeO2-SiO2 matrix was added and stirring was continued for 4 hours. The mixture was evaporated at 100°C and calcined at 400°C for 4 hours to obtain 1.5wt% Fe-0.5wt% Ni-0.05wt% Cs / 30wt% CeO2-SiO2 catalyst.

[0016] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 800 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 650°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 60%, and the selectivity of propylene is 58%.

[0017] Example 3

[0018] Preparation of 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / 30wt%CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 70wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C, and obtain 30wt%CeO2-SiO2, in which cerium oxide is nanoparticles with an average size of 5nm; introduce Fe, Ni, and Cs by impregnation method: take 54mL 10mmol / L ferric nitrate aqueous solution, 17mL of 10mmol / L nickel nitrate aqueous solution and 7.6mL of 1.0mmol / L cesium nitrate aqueous solution were co-impregnated and stirred at room temperature. 2g of the above-mentioned 30wt% CeO2-SiO2 matrix was added and stirring was continued for 4 hours. The mixture was evaporated at 100°C and calcined at 400°C for 4 hours to obtain 1.5wt% Fe-0.5wt% Ni-0.05wt% Cs / 30wt% CeO2-SiO2 catalyst.

[0019] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 800 mL / (g·h), and C3H8:CO2=1:1 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 46%, and the selectivity of propylene is 60%.

[0020] Example 4

[0021] Preparation of 1.5wt% Fe-0.5wt% Ni-0.08wt% Mg / 30wt% CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 70wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C, and obtain 30wt% CeO2-SiO2, in which cerium oxide is nanoparticles with an average size of 5nm; introduce Fe, Ni, and Mg by impregnation method: take 54mL 10mmol / L ferric nitrate aqueous solution, 17mL of 10mmol / L nickel nitrate aqueous solution and 4.7mL of 10mmol / L magnesium nitrate aqueous solution are co-impregnated, stirred at room temperature, 2g of the above-mentioned 30wt% CeO2-SiO2 matrix is ​​added, stirring is continued for 4 hours, evaporated at 100°C, and calcined at 400°C for 4 hours to obtain 1.5wt% Fe-0.5wt% Ni-0.08wt% Mg / 30wt% CeO2-SiO2 catalyst.

[0022] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 800 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 51%, and the selectivity of propylene is 62%.

[0023] Example 5

[0024] Preparation of 0.5wt% Zn-0.5wt% Mn-0.08wt% Mg / 20wt% CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of triphenylmethylsilane (silicon dioxide equivalent is 80wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.55mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=11, continue stirring for 4 hours, filter, wash with water three times, and evaporate to dryness at 100°C to obtain 20wt% CeO2-SiO2 catalyst. O2, wherein cerium oxide is nanoparticles with an average size of 9nm; Zn, Mn, and Mg are introduced by impregnation method: 15.4mL of 10mmol / L zinc nitrate, 18.2mL of 10mmol / L manganese nitrate aqueous solution and 4.7mL of 10mmol / L magnesium nitrate aqueous solution are taken, stirred at room temperature, 2g of the above-mentioned 20wt% CeO2-SiO2 matrix is ​​added, stirring is continued for 4 hours, evaporated at 100°C, and calcined at 550°C for 4 hours to obtain 0.5wt% Zn-0.5wt% Mn-0.08wt% Mg / 20wt% CeO2-SiO2 catalyst.

[0025] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 800 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 54%, and the selectivity of propylene is 65%.

[0026] Example 6

[0027] Preparation of 0.5wt%Fe-0.5wt%Zn-0.08wt%Mg / 30wt%CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 70wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=10, continue stirring for 4 hours, filter, wash with water three times, and evaporate to dryness at 100°C to obtain 30wt%CeO2- SiO2 in which cerium oxide is nanoparticles with an average size of 5nm; Fe, Zn, and Mg are introduced by impregnation method: a certain amount of 10mmol / L ferric nitrate, 15.4mL of 10mmol / L zinc nitrate aqueous solution and 4.7mL of 10mmol / L magnesium nitrate aqueous solution are taken, stirred at room temperature, 2g of the above-mentioned 30wt% CeO2-SiO2 matrix is ​​added, stirring is continued for 4 hours, evaporated at 100°C, and calcined at 400°C for 4 hours to obtain 0.5wt% Fe-0.5wt% Zn-0.08wt% Mg / 30wt% CeO2-SiO2 catalyst.

[0028] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 800 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 53%, and the selectivity of propylene is 64%.

[0029] Example 7

[0030] Preparation of 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / 30wt%CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 70wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C, and obtain 30wt%CeO2-SiO2, in which cerium oxide is nanoparticles with an average size of 5nm; introduce Fe, Ni, and Cs by impregnation method: take a certain amount of 54mL 10mmol / L ferric nitrate aqueous solution, 17mL of 10mmol / L nickel nitrate aqueous solution and 7.6mL of 1.0mmol / L cesium nitrate aqueous solution were co-impregnated and stirred at room temperature. 2g of the above-mentioned 30wt% CeO2-SiO2 matrix was added and stirring was continued for 4 hours. The mixture was evaporated at 100°C and calcined at 400°C for 4 hours to obtain 1.5wt% Fe-0.5wt% Ni-0.05wt% Cs / 30wt% CeO2-SiO2 catalyst.

[0031] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 500 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 63%, and the selectivity of propylene is 60%.

[0032] Example 8

[0033] Preparation of 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / 30wt%CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 70wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C, and obtain 30wt%CeO2-SiO2, in which cerium oxide is nanoparticles with an average size of 5nm; introduce Fe, Ni, and Cs by impregnation method: 54mL 10mmol / L ferric nitrate aqueous solution, 17mL of 10mmol / L nickel nitrate aqueous solution and 7.6mL of 1.0mmol / L cesium nitrate aqueous solution were co-impregnated and stirred at room temperature. 2g of the above-mentioned 30wt% CeO2-SiO2 matrix was added and stirring was continued for 4 hours. The mixture was evaporated at 100°C and calcined at 400°C for 4 hours to obtain 1.5wt% Fe-0.5wt% Ni-0.05wt% Cs / 30wt% CeO2-SiO2 catalyst.

[0034] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 1000 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 52%, and the selectivity of propylene is 64%.

[0035] Example 9

[0036] Preparation of 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / 30wt%CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 70wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C, and obtain 30wt%CeO2-SiO2, in which cerium oxide is nanoparticles with an average size of 5nm; introduce Fe, Ni, and Cs by impregnation method: 54mL 10mmol / L ferric nitrate aqueous solution, 17mL of 10mmol / L nickel nitrate aqueous solution and 7.6mL of 1.0mmol / L cesium nitrate aqueous solution were co-impregnated and stirred at room temperature. 2g of the above-mentioned 30wt% CeO2-SiO2 matrix was added and stirring was continued for 4 hours. The mixture was evaporated at 100°C and calcined at 400°C for 4 hours to obtain 1.5wt% Fe-0.5wt% Ni-0.05wt% Cs / 30wt% CeO2-SiO2 catalyst.

[0037] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 2000 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 51%, and the selectivity of propylene is 64%.

[0038] Example 10

[0039] Preparation of 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / 30wt%CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 70wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C, and obtain 30wt%CeO2-SiO2, in which cerium oxide is nanoparticles with an average size of 5nm; introduce Fe, Ni, and Cs by impregnation method: 54mL 10mmol / L ferric nitrate aqueous solution, 17mL of 10mmol / L nickel nitrate aqueous solution and 7.6mL of 1.0mmol / L cesium nitrate aqueous solution were co-impregnated and stirred at room temperature. 2g of the above-mentioned 30wt% CeO2-SiO2 matrix was added and stirring was continued for 4 hours. The mixture was evaporated at 100°C and calcined at 400°C for 4 hours to obtain 1.5wt% Fe-0.5wt% Ni-0.05wt% Cs / 30wt% CeO2-SiO2 catalyst.

[0040] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 800 mL / (g·h), and C3H8:CO2=1:4 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 59%, and the selectivity of propylene is 61%.

[0041] Comparative Example 1

[0042] Preparation of 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / CeO2 catalyst: weigh 5g of cerium nitrate hexahydrate and dissolve it in 500mL of water; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust the pH to 8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C to obtain CeO2, the cerium oxide is nanoparticles with an average size of 25nm; introduce Fe, Ni, and Cs by impregnation method: take 54mL of 10mmol / L iron nitrate aqueous solution, 17mL of 10mmol / L nickel nitrate aqueous solution and 7.6mL of 1.0mmol / L cesium nitrate aqueous solution for co-impregnation, stir at room temperature, add 2g of the above CeO2 matrix, continue stirring for 4 hours, evaporate to dryness at 100°C, and calcine at 400°C for 4 hours to obtain 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / CeO2 catalyst.

[0043] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 800 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 23%, and the selectivity of propylene is 45%.

[0044] Comparative Example 2

[0045] Preparation of 1.5wt%Fe-0.5wt%Ni-0.05wt%Cs / 5wt%CeO2-SiO2 catalyst: Weigh 5g of cerium nitrate hexahydrate and a certain amount of tetraethyl orthosilicate (silicon dioxide equivalent is 95wt% of the total matrix content), dissolve in 500mL of ethanol aqueous solution, the volume ratio of ethanol to water is 1:1, and the concentration of cerium nitrate is 0.11mol / L; add ammonia water (25%) dropwise to the above solution under stirring conditions, adjust pH=8, continue stirring for 4 hours, filter, wash three times with water, evaporate to dryness at 100°C, and obtain 5wt%CeO2-SiO2, in which cerium oxide is nanoparticles with an average size of 20nm; introduce Fe, Ni, and Cs by impregnation method: take 54mL 10mmol / L ferric nitrate aqueous solution, 17mL of 10mmol / L nickel nitrate aqueous solution and 7.6mL of 1.0mmol / L cesium nitrate aqueous solution were co-impregnated and stirred at room temperature. 2g of the above-mentioned 5wt% CeO2-SiO2 matrix was added and stirring was continued for 4 hours. The mixture was evaporated at 100°C and calcined at 400°C for 4 hours to obtain 1.5wt% Fe-0.5wt% Ni-0.05wt% Cs / 5wt% CeO2-SiO2 catalyst.

[0046] Weigh 200 mg of the above catalyst, sieve out 14-25 mesh catalyst and fill it into the reaction tube, pre-treat with hydrogen reduction before the reaction, with a hydrogen flow rate of 30 ml / min, and treat with hydrogen at 450°C for 1 hour; react at normal pressure, with a propane space velocity of 800 mL / (g·h), and C3H8:CO2=1:2 (molar ratio). React at 550°C, after 400 minutes of reaction, online gas chromatography analysis shows that the conversion rate of propane is 25%, and the selectivity of propylene is 48%.

Claims

1. A method for preparing propylene by oxidative dehydrogenation of propane, characterized in that: The process of oxidative dehydrogenation of propane to produce propylene is as follows: propane and CO2 are used as raw materials to react in a fixed bed reactor, a supported silica-cerium oxide composite catalyst is filled in a reaction tube of the fixed bed reactor and the reaction tube is placed in the fixed bed reactor, the reaction temperature is 450° C. to 650° C., the feed space velocity of propane is 500 to 2000 mL / (g·h), and the molar ratio of propane:CO2 is 1:1 to 1:4; The supported silicon oxide-cerium oxide composite catalyst comprises active metal, silicon oxide matrix, cerium oxide and auxiliary agent; The supported silicon oxide-cerium oxide composite catalyst, wherein the active metal is one or more of Fe, Ni, Zn, and Mn; the content of the active metal in the composite catalyst is 0.05 wt% to 5.0 wt%; Cerium oxide accounts for 5.0 wt% to 50 wt% of the total mass of silicon oxide and cerium oxide; The auxiliary agent is one or two of Cs and Mg; the content of the auxiliary agent in the composite catalyst is 0.05 wt% ~1.0 wt%.

2. The method according to claim 1, characterized in that: In the supported silicon oxide-cerium oxide composite catalyst, the content of active metal is 0.1 wt% to 4.0 wt%; the content of cerium oxide accounts for 10 wt% to 40 wt% of the total mass of silicon oxide and cerium oxide; and the content of auxiliary agent is 0.05 wt% to 1.0 wt%.

3. The method according to claim 1 or 2, characterized in that: The content of active metal is 0.5 wt%~2.0 wt%; cerium oxide accounts for 20 wt%~30 wt% of the total mass of silicon oxide and cerium oxide; and the content of auxiliary agent is 0.1 wt%~0.5 wt%.

4. The method according to claim 1 or 2, characterized in that: The supported silicon oxide-cerium oxide composite catalyst uses silicon oxide-cerium oxide as a carrier. The silicon oxide-cerium oxide carrier is prepared by co-hydrolysis of one or two of organic silane or ethyl orthosilicate with a precursor salt of cerium. The hydrolysis is carried out at room temperature, and the concentration of the cerium salt is 0.1-1.1 mol / L. The system pH is adjusted to 8-11 for hydrolysis.

5. The method according to claim 1, characterized in that: The active metal and the auxiliary agent are introduced by impregnation method to load them on the silicon oxide-cerium oxide carrier, and calcined at 300 ℃ ~ 600 ℃ for 2-6 hours to obtain a composite catalyst.

6. The method according to claim 1, characterized in that: Before the reaction, the composite catalyst needs to be pre-treated by hydrogen reduction at 300°C~550°C for 1-6 hours.

7. The method according to claim 1, characterized in that: The reaction temperature is 450-550°C.

8. The method according to claim 1, characterized in that: The reaction temperature is 500-550°C, the feed space velocity of propane is 600-1000 mL / (g·h), and the molar ratio of propane:CO2 is 1:2-1:

4.

9. A catalyst, characterized in that: It is a supported silicon oxide-cerium oxide composite catalyst, comprising active metal, silicon oxide matrix, cerium oxide and auxiliary agent; The supported silicon oxide-cerium oxide composite catalyst, wherein the active metal is one or more of Fe, Ni, Zn, and Mn; the content of the active metal in the composite catalyst is 0.05 wt% to 5.0 wt%; Cerium oxide accounts for 5.0 wt% to 50 wt% of the total mass of silicon oxide and cerium oxide; The auxiliary agent is one or two of Cs and Mg; the content of the auxiliary agent in the composite catalyst is 0.05 wt% ~1.0 wt%.

10. The catalyst according to claim 9, characterized in that: In the supported silicon oxide-cerium oxide composite catalyst, the content of active metal is 0.1 wt% to 4.0 wt%, cerium oxide accounts for 10 wt% to 40 wt% of the total mass of silicon oxide and cerium oxide, and the content of auxiliary agent is 0.05 wt% to 1.0 wt%.

11. The catalyst according to claim 10, characterized in that: In the supported silicon oxide-cerium oxide composite catalyst, the content of active metal is 0.5 wt% to 2.0 wt%; the content of cerium oxide accounts for 20 wt% to 30 wt% of the total mass of silicon oxide and cerium oxide; and the content of auxiliary agent is 0.1 wt% to 0.5 wt%.

12. The catalyst according to claim 9 or 10, characterized in that: The supported silicon oxide-cerium oxide composite catalyst uses silicon oxide-cerium oxide as a carrier. The silicon oxide-cerium oxide carrier is prepared by co-hydrolysis of one or two of organic silane or ethyl orthosilicate with a cerium precursor salt. The hydrolysis is carried out at room temperature, and the concentration of the cerium salt is 0.1-1.1 mol / L. The system pH is adjusted to 8-11 for hydrolysis. The active metal and the auxiliary agent are introduced by impregnation method to load them on the silicon oxide-cerium oxide carrier, and calcined at 300 ℃ ~ 600 ℃ for 2-6 hours to obtain a composite catalyst.

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