Preparation method of chromium-based propane dehydrogenation catalyst and application thereof

Abstract

This invention relates to a method for preparing a chromium-based propane dehydrogenation catalyst and its application. The catalyst is prepared by modifying a composite support with multiple active components. The composite support consists of an X-Y-Al compound prepared by a precipitation-impregnation method, and γ-Al₂O₃, η-Al₂O₃, or δ-Al₂O₃, where X is derived from a transition metal and Y is derived from an alkaline earth metal. The multiple active components consist of Cr, Ga, alkali metals, and rare earth metals. Based on the mass of the catalyst itself, it comprises the following components in the following mass percentages: 10%–20% active component Cr₂O₃, 0.05%–5% Ga₂O₃, 0.1%–2.0% alkali metal, 0.1%–2.0% rare earth metal, and the composite support content is 60%–80%, with the remainder being a binder. The content of X and Y elements in the composite support is 0.01%–5.0%, and the sum of the mass percentages of the above components is 100%. This Cr-based dehydrogenation catalyst exhibits good high-temperature and hydrothermal stability, and demonstrates excellent dehydrogenation activity when used in propane dehydrogenation processes that require frequent regeneration under harsh conditions.

Description

Technical Field

[0001] This invention belongs to the field of propane dehydrogenation catalyst preparation and application, specifically the preparation of a chromium-based propane dehydrogenation catalyst and the method of applying the catalyst in the propane dehydrogenation reaction. Background Technology

[0002] As a basic chemical product, propylene production has been increasing year by year in recent years. Among the technologies for increasing propylene production, propane dehydrogenation, with its advantages of high propylene yield, friendly byproducts, and lower investment compared to refining for the same propylene scale, is gradually gaining favor among emerging propylene producers in China. Especially in China, a large number of propane dehydrogenation units have been built and put into operation, but the technology is still mainly based on UOP's Oleflex process and ABB Lummus's Catofin process.

[0003] γ-Al₂O₃ is often used as a support for propane dehydrogenation catalysts due to its good high-temperature stability (<800℃) and large specific surface area. A typical dehydrogenation catalyst is the Cr₂O₃ / Al₂O₃ system, which is used in the Catofin process. However, this system suffers from poor dehydrogenation activity stability, leading to frequent regeneration. Published literature reports that high-frequency, high-temperature regeneration causes Cr to integrate into the Al₂O₃ crystal structure, forming Cr-Al compounds, resulting in a gradual decline in catalyst activity and a continuous increase in reaction stability. Therefore, researchers both domestically and internationally have been conducting in-depth research on Cr-based dehydrogenation catalysts, hoping to develop novel Cr / Al₂O₃ dehydrogenation catalysts with high dehydrogenation activity and stable regeneration performance.

[0004] Chinese patent CN110114142A provides a method for preparing Cr2O3 / Al2O3 dehydrogenation catalysts without using high-valent chromium. This method involves partially doping Cr2O3 into a support, extruding it with an additive, and then impregnating it with low-valent chromium. This method achieves the same dehydrogenation performance as catalysts prepared with high-valent chromium without using it. Chinese patent CN113329814A provides a method for preparing a dehydrogenation catalyst supported on a Cr2O3 / Al2O3 support using ascorbic acid as a competing adsorbent for alkali metal loading. This method can improve propylene selectivity. Chinese patent CN110152650A provides a catalytic dehydrogenation material with a metal-doped alumina salt MaOb·xAl2O3 as the support material, and then loading Cr. This material retains good catalytic performance even after high-temperature carbonization above 1000℃. The researchers of the above-mentioned patents have provided a method for optimizing the performance of Cr2O3 / Al2O3 dehydrogenation catalysts and achieved certain results.

[0005] The aforementioned patents have all optimized and improved the preparation process of Cr2O3 / Al2O3 dehydrogenation catalysts, but there is still much room for improvement in dehydrogenation performance, and the high-temperature hydrothermal properties of the support are still relatively lacking. Summary of the Invention

[0006] The purpose of this invention is to address the problems of current catalysts by providing a method for preparing a chromium-based propane dehydrogenation catalyst and its application. This catalyst is a novel propane dehydrogenation catalyst based on XY dual-element modified Al₂O₃ as a support and Cr-M dual dehydrogenation active centers. This catalyst exhibits excellent high-temperature and hydrothermal stability and excellent dehydrogenation activity for propane dehydrogenation. This invention modulates the elements in the two components during the support preparation process, not only by altering the crystal structure through doping with transition metals or rare earth metals, but also by modifying the acidity and basicity through surface impregnation of microparticles. This not only further promotes the propane dehydrogenation reaction but also improves the high-temperature and hydrothermal performance of the support. During the support impregnation process, new active components are added within a certain content range to form a Cr-Ga dual dehydrogenation structure, optimizing the dehydrogenation performance. Finally, a novel multi-component modified Cr₂O₃-Al₂O₃ dehydrogenation catalyst with high activity and high stability is prepared.

[0007] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0008] A novel chromium-based propane dehydrogenation catalyst is prepared by modifying a composite support with multiple active components, resulting in a composite support exhibiting excellent electron transfer performance. The composite support is composed of an XY-Al compound prepared by impregnation precipitation and γ-Al₂O₃, η-Al₂O₃, or δ-Al₂O₃ (i.e., XY-Al compound and γ-Al₂O₃, XY-Al compound and η-Al₂O₃, or XY-Al compound and δ-Al₂O₃). The X element is derived from a transition metal, and the Y element is derived from an alkaline earth metal. The multiple active components are a composite modified formulation consisting of Cr, Ga, alkali metals, and rare earth metals. Based on the mass of the catalyst itself, it comprises the following components in the following mass percentages: 10%–20% active component Cr₂O₃, 0.05%–5% Ga₂O₃, 0.1%–2.0% alkali metal, 0.1%–2.0% rare earth metal, 60%–80% composite support, and the remainder is binder; the content of elements X and Y in the support is 0.01%–5.0%, and the sum of the mass percentages of the above components is 100%. This catalyst can be used for direct dehydrogenation of propane in fluidized beds or fixed beds through different molding methods.

[0009] Furthermore, in the composite support, the XY-Al compound prepared by the precipitation-impregnation method accounts for 20-70% of the total mass of the catalyst.

[0010] Furthermore, the element X is any one or two of Cu, Zr, Zn and In, respectively derived from copper nitrate, zirconium oxynitrate, zinc nitrate and indium nitrate; the element Y is any one or two of Mg, Ca and Ba, each derived from its respective nitrate.

[0011] Furthermore, alkali metals are derived from any one of Li, Na, and K, and all originate from nitrates; rare earth metals are derived from any one of Ce, La, and Pr, and all originate from nitrates; Ga originates from gallium nitrate, and Cr originates from one of chromium nitrate, chromium acetate, or chromium oxide.

[0012] As a preferred embodiment of this application, the preparation method of the chromium-based propane dehydrogenation catalyst described above includes the following steps:

[0013] (1) Weigh a certain amount of aluminum nitrate and element X raw material, mix them, add 5 to 10 times the mass of distilled water, and heat to 40 to 70°C to dissolve into a clear solution. Then, gradually add ammonia water or Na2CO3 aqueous solution to precipitate the mixture. The pH value of the precipitate is between 7.0 and 9.0. After the precipitation is complete, filter and wash (preferably 3 times) to obtain a filter cake of coprecipitated mixture of X-Al elements. After drying the filter cake in an oven, calcine it at 500 to 900°C for 2 to 4 hours. Then, ball mill it to 10 to 30 micrometers for later use to obtain X-Al compound, which is denoted as precursor I.

[0014] (2) Weigh a certain amount of Y element raw material and deionized water, mix them together and heat to 60-70℃ to dissolve; add the measured macroporous pseudoboehmite or trihydrate gibbsite and precursor I together to the above solution and stir continuously. After sealing the container, maintain the temperature of the mixed liquid at 40-60℃ and stir at this temperature for about 0.5-1.0h; then raise the temperature to 80-100℃ and stir open until the mixed liquid becomes viscous. Then put it into an oven and dry it rapidly at 120℃. After drying, calcine it at 500-900℃ for 3-6h. Then ball mill it to 10-30 micrometers for later use to obtain XY-Al compound, which is denoted as precursor II.

[0015] (3) First, weigh a certain amount of inorganic acid and organic acid, add deionized water to dilute them. The concentration of inorganic acid in the mixed acid solution is 0.5% to 3.0%, and the concentration of organic acid is 0.5% to 5.0%. Next, weigh the measured high-viscosity pseudo-boehmite, precursor II, pore expander and extrusion aid and mix them thoroughly. Then, mix the mixed acid solution with the above powder and knead it in a kneader. After kneading, extrude it in an extruder (the diameter can be 3 mm). After drying, calcine it in a muffle furnace at 500 to 900°C. This is called precursor III.

[0016] (4) Weigh a certain amount of deionized water, and then weigh a certain amount of Ga salt, alkali metal and rare earth metal nitrates and dissolve them in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add catalyst precursor III to the above solution for equal volume impregnation, then ultrasonically vibrate for 15 to 60 minutes and dry it. Finally, calcine it at 400 to 600℃ for 2 to 6 hours and pack it into bags for later use. It is called precursor IV.

[0017] (5) Weigh a certain amount of deionized water, and then weigh a certain amount of Cr salt or CrO3 and dissolve it in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add the catalyst precursor IV to the above solution for equal volume impregnation. After microwave treatment for 5 to 20 minutes, dry it. Finally, calcine it at 500 to 900°C with flowing humid air for 2 to 6 hours to obtain the desired catalyst, and pack it for later use.

[0018] Furthermore, in the above preparation steps, the extrusion aid used in step (3) is any one of guar gum powder, methylcellulose, cellulose, and graphite; the pore expander is any one of polyvinyl alcohol, polyethylene glycol, and CTAB.

[0019] Furthermore, in the above preparation steps, the macroporous boehmite used in step (2) has a pore volume of 0.7 to 1.2 ml / g; the high-viscosity boehmite used in step (3) has a pore volume of 0.4 to 0.6 ml / g and a gel solubility index greater than 90.

[0020] Furthermore, in the above preparation steps, the organic acid used in step (3) is any one of citric acid, oxalic acid, acetic acid, tartaric acid and ascorbic acid, and its amount is 0.5% to 5% of the mass of the XY-Al composite carrier; the inorganic acid used in step (3) is any one of nitric acid, sulfuric acid and hydrochloric acid, and its amount is 0.5% to 5% of the mass of the XY-Al composite carrier.

[0021] Furthermore, in the above preparation steps, the humid air used in step (5) is a mixture of water vapor and air, wherein the water vapor content accounts for 1% to 10% of the mass of the mixture.

[0022] Furthermore, when this catalyst is used for the direct dehydrogenation of propane, the suitable reaction temperature range is 550–650 °C, and the suitable mass hourly space velocity is 0.5–3 h⁻¹. -1 The regeneration cycle is 10–240 min. During regeneration, the mixture is first purged with nitrogen-steam (nitrogen accounts for about 30% of the mass of the mixture) for 10–30 min, and then air is introduced for regeneration at 620–650℃. The regeneration carbonization time is 10–240 min.

[0023] Compared with existing technologies, the positive effects of this invention are reflected in:

[0024] In the preparation of the support, the two-component modulating elements can not only change the crystal structure by doping with transition metals or rare earth metals, making the Al-XY structure in the support more stable and reducing the penetration of Cr into the support structure after long-term use; at the same time, the acidity and alkalinity can be modulated by impregnation modification on the surface of micro-particles, which is not only more conducive to the propane dehydrogenation reaction, but also makes the high-temperature hydrothermal performance of the support better; during the impregnation process, new active components can be added within a certain content range to form a Cr-Ga dual dehydrogenation structure, thereby optimizing the dehydrogenation performance. Detailed Implementation

[0025] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0026] Any feature disclosed in this specification (including the claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0027] Unless otherwise specified, the percentages below represent the mass percentage of the total catalyst mass. In the examples and comparative examples below, 100g of macroporous boehmite was calcined to yield 65g of anhydrous Al2O3, and 100g of high-viscosity boehmite was calcined to yield 67g of anhydrous Al2O3.

[0028] Example 1:

[0029] (1) Weigh a certain amount of aluminum nitrate and zinc nitrate, mix them, add 5 times the mass of distilled water, and heat to 70°C to dissolve them into a clear solution. Then, gradually add 0.1 mol / L Na2CO3 aqueous solution to precipitate. After precipitation, filter and wash 3 times to obtain a filter cake of X-Zn coprecipitate mixture. After drying the filter cake in an oven, calcine it at 550°C for 4 hours, and then ball mill it to 30 micrometers for later use to obtain Zn-Al compound, which is denoted as precursor I.

[0030] (2) Weigh a certain amount of magnesium nitrate and deionized water, mix them, and heat them to 60°C to dissolve them; add the measured macroporous pseudoboehmite (pore volume 0.90) and precursor I together to the above solution and stir continuously. After sealing the container, maintain the temperature of the mixed liquid at 50°C and stir at this temperature for about 1.0 h; then raise the temperature to 100°C and stir openly until the mixed liquid becomes viscous. Then put it into an oven and dry it rapidly at 120°C. After drying, calcine it at 750°C for 4 h, and then ball mill it to 30 micrometers for later use to obtain Zn-Mg-Al compound, which is denoted as precursor II.

[0031] (3) First, weigh a certain amount of concentrated nitric acid and citric acid, add deionized water to dilute them. The concentration of nitric acid in the mixed acid solution is 0.5% and the concentration of citric acid is 2.0%. Then weigh the measured high-viscosity pseudoboehmite (pore volume 0.45, gel solubility index 90), precursor II, 2% methylcellulose, and 2% CATB and mix them thoroughly. Then mix the mixed acid solution with the above powder and knead it in a kneader. After kneading, extrude it in an extruder (diameter 3mm). After drying, calcine it in a muffle furnace at 600℃. This is called precursor III.

[0032] (4) Weigh a certain amount of deionized water, and then weigh a certain amount of gallium nitrate, sodium nitrate and lanthanum nitrate and dissolve them in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add catalyst precursor III to the above solution for equal volume impregnation, then ultrasonically vibrate for 30 min and dry it. Finally, calcine it at 600℃ for 4 h and pack it into bags for later use. It is called precursor IV.

[0033] (5) Weigh a certain amount of deionized water, and then weigh a certain amount of chromium nitrate and dissolve it in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add the catalyst precursor IV to the above solution for equal volume impregnation. After microwave treatment for 10 minutes, dry it. Finally, calcine it at 700°C with flowing humid air for 4 hours to obtain the desired catalyst, and pack it in bags for later use.

[0034] Analysis showed that the catalyst contained 12% Cr2O3, 5% Ga2O3, 0.8% MgO, 1.0% ZnO, 0.7% Na2O, and 0.25% La2O3. The support contained 30% XY-Al2O3 compounds, with the remainder being Al2O3.

[0035] Example 2:

[0036] (1) Weigh a certain amount of aluminum nitrate and zirconium oxynitrate, mix them, add 10 times the mass of distilled water, and heat to 60°C to dissolve into a clear solution. Then slowly add 10% ammonia water solution to precipitate. After precipitation is complete, filter and wash three times to obtain a filter cake of X-Al coprecipitate mixture. After drying the filter cake in an oven, calcine it at 600°C for 4 hours, and then ball mill it to 25 micrometers for later use to obtain Zr-Al compound, which is denoted as precursor I.

[0037] (2) Weigh a certain amount of magnesium nitrate and deionized water, mix them together, and heat them to 70°C to dissolve them; add the measured macroporous boehmite (pore volume 1.10) and precursor I together to the above solution and stir continuously. After sealing the container, maintain the temperature of the mixed liquid at 50°C and stir at this temperature for about 0.5 hours; then raise the temperature to 80°C and stir with the container open until the mixed liquid becomes viscous. Then place it in an oven and dry it rapidly at 150°C. After drying, calcine it at 850°C for 6 hours, and then ball mill it to 10 micrometers for later use to obtain Zr-Mg-Al compound, which is denoted as precursor II.

[0038] (3) First, weigh a certain amount of concentrated nitric acid and oxalic acid, add deionized water to dilute them, and the concentration of nitric acid in the mixed acid solution is 1.0% and the concentration of oxalic acid is 1.0%. Then weigh the measured high viscosity pseudoboehmite (pore volume 0.55, gel solubility index 95), precursor II, 3% guar gum powder and 1% polyvinyl alcohol and mix them thoroughly. Then mix the mixed acid solution with the above powder and knead it in a kneader and then extrude it in an extruder (diameter 3mm). After drying, calcine it in a muffle furnace at 600℃ for 4h and record it as precursor III.

[0039] (4) Weigh a certain amount of deionized water, and then weigh a certain amount of gallium nitrate, sodium nitrate and cerium nitrate and dissolve them in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add catalyst precursor III to the above solution for equal volume impregnation, then sonicate for 15 min and dry it. Finally, calcine it at 500℃ for 6 h and pack it in a bag for later use. It is called precursor IV.

[0040] (5) Weigh a certain amount of deionized water, and then weigh a certain amount of CrO3 and dissolve it in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add the catalyst precursor IV to the above solution for equal volume impregnation. After microwave treatment for 20 minutes, dry it. Finally, calcine it at 600℃ with flowing humid air for 2 hours to obtain the desired catalyst, and pack it into bags for later use.

[0041] Analysis showed that the catalyst contained 17% Cr2O3, 2% Ga2O3, 0.4% MgO, 1.4% ZrO2, 0.9% Na2O, and 0.6% CeO2. The support contained 40% XY-Al2O3 compounds, with the remainder being Al2O3.

[0042] Example 3:

[0043] (1) Weigh a certain amount of aluminum nitrate and copper nitrate, mix them, add 6 times the mass of distilled water, and heat to 40°C to dissolve them into a clear solution. Then, gradually add 0.15 mol / L Na2CO3 aqueous solution to precipitate the mixture. After precipitation is complete, filter and wash three times to obtain a filter cake of Cu-Al coprecipitate mixture. After drying the filter cake in an oven, calcine it at 650°C for 3 hours, and then ball mill it to 20 micrometers for later use to obtain Cu-Al compound, which is denoted as precursor I.

[0044] (2) Weigh a certain amount of barium nitrate and deionized water, mix them together, and heat them to 70°C to dissolve them; add the measured macroporous boehmite (pore volume 1.2) and precursor I together to the above solution and stir continuously. After sealing the container, maintain the temperature of the mixed liquid at 50°C and stir at this temperature for about 1.0 h; then raise the temperature to 80°C and stir with an open mouth until the mixed liquid becomes viscous. Then put it into an oven and dry it rapidly at 120°C. After drying, calcine it at 650°C for 4 h, and then ball mill it to 20 micrometers for later use to obtain Cu-Ba-Al compound, which is denoted as precursor II.

[0045] (3) First, weigh a certain amount of nitric acid and tartaric acid, add deionized water to dilute them. The concentration of nitric acid in the mixed acid solution is 2.0%, and the concentration of organic acid is 0.5%. Then weigh the measured high-viscosity pseudoboehmite (pore volume 0.40, gel solubility index 92), precursor II, 1% methylcellulose, and 2% polyethylene glycol and mix them thoroughly. Then mix the mixed acid solution with the above powder and knead it in a kneader. After kneading, extrude it in an extruder (diameter 3mm). After drying, calcine it in a muffle furnace at 650℃ for 3h. This is called precursor III.

[0046] (4) Weigh a certain amount of deionized water, and then weigh a certain amount of gallium nitrate, potassium nitrate and praseodymium nitrate and dissolve them in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add catalyst precursor III to the above solution for equal volume impregnation, then ultrasonically vibrate for 45 min and dry it. Finally, calcine it at 650℃ for 4 h and pack it into bags for later use. It is called precursor IV.

[0047] (5) Weigh a certain amount of deionized water, and then weigh a certain amount of chromium nitrate and dissolve it in the deionized water. The water volume should meet the requirement of equal volume impregnation. Then, add catalyst precursor IV to the above solution for equal volume impregnation. After microwave treatment for 20 minutes, dry the solution and finally calcine it at 600°C with flowing humid air for 4 hours to obtain the desired catalyst. Pack it for later use. Since it is impossible to complete the impregnation of all Cr2O3 content in one step, repeat step (5) twice until the Cr2O3 content in the catalyst meets the requirements.

[0048] Analysis showed that the catalyst contained 18% Cr2O3, 1.0% Ga2O3, 0.15% BaO, 0.6% CuO, 1.5% K2O, and 1.0% Pr2O3. The support contained 60% XY-Al2O3 compounds, with the remainder being Al2O3.

[0049] Example 4:

[0050] (1) Weigh a certain amount of aluminum nitrate and zinc nitrate, mix them, add 7 times the mass of distilled water, and heat to 50°C to dissolve into a clear solution. Then, gradually add 8% ammonia water solution to precipitate. After precipitation is complete, filter and wash 3 times to obtain a filter cake of Zn-Al coprecipitate mixture. After drying the filter cake in an oven, calcine it at 550°C for 2 hours, and then ball mill it to 15 micrometers for later use to obtain Zn-Al compound, which is denoted as precursor I.

[0051] (2) Weigh a certain amount of calcium nitrate and deionized water, mix them together, and heat them to 60°C to dissolve them; add the measured amount of gibbsite and precursor I together to the above solution and stir continuously. After sealing the container, maintain the temperature of the mixed liquid at 60°C and stir at this temperature for about 1.0 h; then raise the temperature to 100°C and stir with an open mouth until the mixed liquid becomes viscous. Then put it into an oven and dry it rapidly at 120°C. After drying, calcine it at 550°C for 3 h, and then ball mill it to 15 micrometers (D50) for later use to obtain the Zn-Ca-Al compound, which is denoted as precursor II.

[0052] (3) First, weigh a certain amount of concentrated hydrochloric acid and acetic acid, add deionized water to dilute them. The concentration of nitric acid in the mixed acid solution is 1.0%, and the concentration of organic acid is 1.0%. Next, weigh the measured high-viscosity pseudoboehmite (pore volume 0.55, colloidal index 95), precursor II, 4% guar gum powder, and 0.5% CATB and mix them thoroughly. Then, mix the mixed acid solution with the above powder and knead it in a kneader. After kneading, extrude it in an extruder (diameter 3mm), dry it, and calcine it in a muffle furnace at 800℃. This is called precursor III.

[0053] (4) Weigh a certain amount of deionized water, and then weigh a certain amount of gallium nitrate, strontium nitrate and lanthanum nitrate and dissolve them in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add catalyst precursor III to the above solution for equal volume impregnation, then ultrasonically vibrate for 30 min and dry it. Finally, calcine it at 550℃ for 4 h and pack it into bags for later use. It is called precursor IV.

[0054] (5) Weigh a certain amount of deionized water, and then weigh a certain amount of CrO3 and dissolve it in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add the catalyst precursor IV to the above solution for equal volume impregnation. After microwave treatment for 20 minutes, dry it. Finally, calcine it at 600℃ with flowing humid air for 4 hours to obtain the desired catalyst, and pack it into bags for later use.

[0055] Analysis showed that the catalyst contained 20% Cr2O3, 0.5% Ga2O3, 1.2% CaO, 0.2% Zn, 0.5% Cs2O, and 0.1% La2O3. The support contained 50% XY-Al2O3 compounds, with the remainder being Al2O3.

[0056] Example 5:

[0057] The preparation steps (1) to (5) are the same as those in Example 1 except for the modified elements and their contents.

[0058] Analysis showed that the catalyst contained 19% Cr2O3, 3.0% Ga2O3, 0.3% CaO, 1.0% In2O3, 1.2% Li2O, and 1.1% La2O3. The support contained 35% XY-Al2O3 compounds, with the remainder being Al2O3.

[0059] Example 6:

[0060] The preparation steps (1) to (5) are the same as those in Example 2 except for the modified elements and their contents.

[0061] Analysis showed that the catalyst contained 25% Cr2O3, 1.5% Ga2O3, 1.2% MgO, 3.0% ZrO2, 1.4% K2O, and 0.7% Pr2O3. The support contained 45% XY-Al2O3 compounds, with the remainder being Al2O3.

[0062] Example 7:

[0063] The preparation steps (1) to (5) are the same as those in Example 3, except for the modified elements and their contents. The different modified elements and their contents are shown in Table 1.

[0064] Analysis showed that the catalyst contained 14% Cr2O3, 3.5% Ga2O3, 1.2% CaO, 0.8% ZnO, 0.4% Na2O, and 0.4% CeO2. The support contained 52% XY-Al2O3 compounds, with the remainder being Al2O3.

[0065] Example 8:

[0066] The preparation steps (1) to (5) are the same as those in Example 4 except for the modified elements and their contents.

[0067] Analysis showed that the catalyst contained 15% Cr2O3, 0.3% Ga2O3, 1.2% CsO, 1.0% CuO, 1.0% K2O, and 1.9% La2O3. The support contained 36% XY-Al2O3 compounds, with the remainder being Al2O3.

[0068] Comparative Example 1:

[0069] The preparation process is similar to that in Example 1.

[0070] (1) First, weigh a certain amount of concentrated nitric acid and citric acid, add deionized water to dilute them. The concentration of nitric acid in the mixed acid solution is 0.5% and the concentration of citric acid is 2.0%. Then weigh the measured amount of high-viscosity boehmite (pore volume 0.45, gel solubility index 90), methylcellulose and CATB and mix them thoroughly. Then mix the mixed acid solution with the above powder and knead it in a kneader. After kneading, extrude it in an extruder (diameter 3mm). After drying, calcine it in a muffle furnace at 600℃. This is called precursor III.

[0071] (2) Weigh a certain amount of deionized water, and then weigh a certain amount of gallium nitrate, sodium nitrate and lanthanum nitrate and dissolve them in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add catalyst precursor III to the above solution for equal volume impregnation, then ultrasonically vibrate for 30 min and dry it. Finally, calcine it at 600℃ for 4 h and pack it into bags for later use. It is called precursor IV.

[0072] (3) Weigh a certain amount of deionized water, and then weigh a certain amount of chromium nitrate and dissolve it in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add the catalyst precursor IV to the above solution for equal volume impregnation. After microwave treatment for 10 minutes, dry it. Finally, calcine it at 600°C with flowing humid air for 4 hours to obtain the desired catalyst, and pack it in bags for later use.

[0073] Analysis showed that the catalyst contained 12% Cr2O3, 5% Ga2O3, 0.7% Na2O, 0.25% La2O3, and the remainder was Al2O3.

[0074] Comparative Example 2:

[0075] Similar to the catalyst components prepared in Example 2, except that the XY-Al composite support structure is not used.

[0076] (1) First, weigh a certain amount of concentrated nitric acid and oxalic acid, add deionized water to dilute them. The concentration of nitric acid in the mixed acid solution is 1.0%, and the concentration of oxalic acid is 1.0%. Next, weigh a measured amount of high-viscosity pseudoboehmite (pore volume 0.55, gel solubility index 95) and polyvinyl alcohol and mix them thoroughly. Then, mix the mixed acid solution with the above powder and knead it in a kneader. After kneading, extrude it in an extruder (diameter 3mm). After drying, calcine it in a muffle furnace at 600℃ for 5h. This is recorded as precursor III.

[0077] (4) Weigh a certain amount of deionized water, and then weigh a certain amount of gallium nitrate, zirconium oxynitrate, magnesium nitrate, sodium nitrate and cerium nitrate and dissolve them in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Stir and heat to 50°C until all are dissolved into a transparent solution. Then add catalyst precursor III to the above solution for equal volume impregnation, followed by ultrasonic vibration for 15 min and drying. Finally, calcine at 600°C for 6 h and pack into bags for later use. This is called precursor IV.

[0078] (5) Weigh a certain amount of deionized water, and then weigh a certain amount of CrO3 and dissolve it in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add the catalyst precursor IV to the above solution for equal volume impregnation. After microwave treatment for 20 minutes, dry it. Finally, calcine it at 600℃ with flowing humid air for 2 hours to obtain the desired catalyst, and pack it into bags for later use.

[0079] Analysis showed that the catalyst contained 17% Cr2O3, 2% Ga2O3, 0.4% MgO, 1.4% ZrO2, 0.9% Na2O, 0.6% CeO2, and the remainder was Al2O3.

[0080] Comparative Example 3:

[0081] The preparation process is similar to that in Example 3, except that it does not contain element X Cu, and the calcination temperature of each step is 650℃.

[0082] Analysis showed that the catalyst contained 18% Cr2O3, 1.0% Ga2O3, 0.15% BaO, 1.5% K2O, 1.0% Pr2O3, and the remainder was Al2O3.

[0083] Comparative Example 4:

[0084] The preparation process is similar to that in Example 4, except that it does not contain the element Y (Ca), and the calcination temperature of each step is 700℃.

[0085] Analysis showed that the catalyst contained 20% Cr2O3, 0.5% Ga2O3, 0.2% Zn, 0.5% Cs2O, 0.1% La2O3, and the remainder was Al2O3.

[0086] Comparative Example 5:

[0087] The preparation process is similar to that in Example 5, except that it does not contain Ga and the calcination temperature of each step is 650°C.

[0088] The catalysts prepared in Examples 1-7 and Comparative Examples 1-5 were evaluated in a fixed-bed reactor. The reaction conditions were as follows: catalyst loading 8 ml, reaction pressure atmospheric pressure, reaction temperature 590 °C, and propane mass hourly space velocity 0.8 h⁻¹. -1 The N2:C3H8 volume ratio was 45:55; the gas was collected using a gas bag; the average propane carbon-based conversion rate and propylene carbon-based selectivity from 0 to 10 min of reaction are shown in Table 1.

[0089] The catalysts prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to continuous regeneration experiments under the following conditions: In a fixed-bed reactor, the catalyst loading was 20 ml, the reaction pressure was atmospheric pressure, the reaction temperature was 590 °C, the propane mass hourly space velocity was 0.8, and the N2:C3H8 ratio was 45:55. After 10 minutes of reaction, a N2-H2O (1.0%) mixed gas was first introduced at the reaction temperature for 10 minutes, and then air was introduced to raise the temperature to 620 °C to start carbonization for 20 minutes. After carbonization and nitrogen purging, the temperature was lowered to the reaction temperature, and the raw materials were introduced again for reaction. This process was repeated 100 times. The changes in activity are shown in Table 1.

[0090] Table 1. Propane dehydrogenation activity data for the catalysts in the examples and comparative examples.

[0091]

[0092] As shown in Table 1, the catalyst activity of this invention is significantly better than that of the comparative sample. Furthermore, it can be seen that after multiple continuous regenerations, the dehydrogenation catalyst using the technical specifications of this invention exhibits excellent propane dehydrogenation activity and stability. Overall, the catalyst of this invention has promising prospects for industrial application.

[0093] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

[0094] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A chromium-based propane dehydrogenation catalyst, characterized in that: This catalyst is prepared by modifying a composite support with multiple active components. The composite support is composed of XY-Al compounds prepared by precipitation-impregnation method and γ-Al2O3, η-Al2O3 or δ-Al2O3, where X comes from transition metals and Y comes from alkaline earth metals. The multiple active components are composed of Cr, Ga, alkali metals and rare earth metals. Based on the mass of the catalyst itself, it includes the following components in the following mass percentages: 10%~20% active component Cr2O3, 0.05%~5% Ga2O3, 0.1%~2.0% alkali metals, 0.1%~2.0% rare earth metals, composite support content 60%~80%, and the remainder is binder. The content of X and Y elements in the composite support is 0.01%~5.0%, and the sum of the mass percentages of the above components is 100%.

2. The chromium-based propane dehydrogenation catalyst according to claim 1, characterized in that: In composite supports, XY-Al compounds prepared by precipitation-impregnation method account for 20-70% of the total mass of the catalyst.

3. The chromium-based propane dehydrogenation catalyst according to claim 1, characterized in that: The element X is any one or any two of Cu, Zr, Zn and In, which are derived from copper nitrate, zirconium oxynitrate, zinc nitrate and indium nitrate, respectively; the element Y is any one or any two of Mg, Ca and Ba, which are derived from their nitrates.

4. The chromium-based propane dehydrogenation catalyst according to claim 1, characterized in that: Alkali metals are derived from any one of Li, Na, and K, and all originate from their nitrates; rare earth metals are derived from any one of Ce, La, and Pr, and all originate from their nitrates; Ga is derived from gallium nitrate, and Cr is derived from any one of chromium nitrate, chromium acetate, or chromium oxide.

5. The method for preparing the chromium-based propane dehydrogenation catalyst according to any one of claims 1-4, characterized in that... Includes the following steps: (1) Weigh a certain amount of aluminum nitrate and X element raw material and mix them. Then add 5 to 10 times the mass of distilled water and heat to 40 to 70°C to dissolve into a clear solution. Then gradually add ammonia water or Na2CO3 aqueous solution to precipitate. The pH value of the precipitate is between 7.0 and 9.

0. After the precipitation is complete, filter and wash to obtain a filter cake of X-Al coprecipitate mixture. Dry the filter cake in an oven and calcine it at 500 to 900°C for 2 to 4 hours. Then ball mill it to 10 to 30 micrometers for later use to obtain X-Al compound, which is called precursor I. (2) Weigh a certain amount of Y element raw material and deionized water, mix and heat to 60~70℃ to dissolve to obtain a Y-containing solution; add the measured macroporous pseudoboehmite or trihydrate gibbsite and the precursor I prepared in step (1) together to the Y-containing solution and stir continuously. After sealing the container, maintain the temperature of the mixed liquid at 40~60℃ and stir at this temperature for 0.5~1.0h; then raise the temperature to 80~100℃ and stir open until the mixed liquid becomes viscous. Then put it into an oven and dry it rapidly at 120℃. After drying, calcine it at 500~900℃ for 3~6h. Then ball mill it to 10~30 micrometers for later use to obtain XY-Al compound, which is recorded as precursor II; (3) First, weigh a certain amount of inorganic acid and organic acid, add deionized water to dilute them, and form a mixed acid solution. The concentration of inorganic acid in the mixed acid solution is 0.5%~3.0%, and the concentration of organic acid is 0.5%~5.0%. Next, weigh the measured high viscosity pseudoboehmite, the precursor II prepared in step (2), the pore expander and the extrusion aid and mix them thoroughly. Then, mix the mixed acid solution with the above powder and knead it in a kneader and then extrude it in an extruder. After drying, calcine it in a muffle furnace at 500~900℃ and record it as precursor III. (4) Weigh a certain amount of deionized water, and then weigh a certain amount of Ga salt, alkali metal and rare earth metal nitrates and dissolve them in deionized water. The amount of water meets the requirement of equal volume impregnation. Then add the catalyst precursor III prepared in step (3) to the above solution for equal volume impregnation, then ultrasonically vibrate for 15~60 min and dry it. Finally, calcine it at 400~600℃ for 2~6 h and pack it in a bag for later use. It is called precursor IV. (5) Weigh a certain amount of deionized water, and then weigh a certain amount of Cr salt or CrO3 and dissolve it in the deionized water. The amount of water should meet the requirement of equal volume impregnation. Then add the catalyst precursor IV prepared in step (3) to the above solution for equal volume impregnation. After microwave treatment for 5~20 min, dry it. Finally, calcine it at 500~900℃ with flowing humid air for 2~6 h to obtain the desired catalyst, and pack it in a bag for later use.

6. The method for preparing the chromium-based propane dehydrogenation catalyst according to claim 5, characterized in that: The macroporous pseudoboehmite used in step (2) has a pore volume of 0.7~1.2 ml / g.

7. The method for preparing the chromium-based propane dehydrogenation catalyst according to claim 5, characterized in that: The organic acid used in step (3) is any one of citric acid, oxalic acid, acetic acid, tartaric acid and ascorbic acid; the inorganic acid used is any one of nitric acid, sulfuric acid and hydrochloric acid; the high viscosity boehmite used has a pore volume of 0.4~0.6 ml / g and a colloidal index of 90 or above; the extrusion aid used in step (3) is any one of guar gum powder, methylcellulose, cellulose and graphite, and its amount is 1%~5% of the mass of the XY-Al composite carrier; the pore expander is any one of polyvinyl alcohol, polyethylene glycol and CTAB, and its amount is 1%~5% of the mass of the XY-Al composite carrier.

8. The method for preparing the chromium-based propane dehydrogenation catalyst according to claim 5, characterized in that: The humid air mentioned in step (5) is a mixture of water vapor and air, wherein the water vapor content accounts for 1% to 10% of the mass of the mixture.

9. The application of the chromium-based propane dehydrogenation catalyst prepared by any one of claims 6-8, characterized in that: This catalyst is used in the direct dehydrogenation of propane.

10. The application of the chromium-based propane dehydrogenation catalyst according to claim 9, characterized in that: When this catalyst is used for the direct dehydrogenation of propane, the reaction temperature range is 550~650℃, and the mass hourly space velocity is 0.5~3h⁻¹. -1 The regeneration cycle is 10~240 min. During regeneration, the nitrogen-steam mixture is first purged for 10~30 min, and then air is introduced to regenerate at 620~650℃. The regeneration carbonization time is 10~240 min.

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