Chromium dehydrogenation catalyst prepared from carrier with defect state and preparation method

Abstract

The invention discloses a chromium dehydrogenation catalyst prepared from a carrier with a defect state and a preparation method. The catalyst comprises the following components in percentage by mass based on the total mass of a dry basis: 3-30% of chromium oxide, 0.1-5% of a first auxiliary agent, 0.1-5% of a second auxiliary agent and the balance of the carrier, the first auxiliary agent is one or more of transition metals; and the second auxiliary agent is one or a mixture of more of rare earth metals. The dehydrogenation catalyst obtained by the method is doped with rare earth metal and transition metal, on one hand, the existence state of active components on the surface of the catalyst is adjusted to obtain higher selectivity, and on the other hand, the catalyst has higher activity by adjusting acidic sites on the surface of the carrier. And the phase change of gamma-Al2O3 is inhibited, the carrier structure is strengthened, a chromium-containing metallic bond is formed, and a chromium substance becomes more stable, so that the overall stability of the catalyst is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of petroleum chemical industry, in particular to a chromium-based dehydrogenation catalyst with a carrier with a defect state and a preparation method. BACKGROUND

[0002] Propylene, as the core raw material for chemical products such as plastics and epoxy propane, has a growing demand. The traditional process (such as refinery by-product, steam cracking) has insufficient capacity, and the cheap propane resources brought by the shale gas revolution provide economic feasibility for propane dehydrogenation (PDH). PDH uses propane as raw material, with a single-pass conversion rate of up to 40%-45% and a propylene selectivity of over 85%, becoming a key technology to fill the supply gap. As of 2023, China's PDH capacity has exceeded 10 million tons / year, but the risk of propylene overcapacity and the intensifying competition for propane resources require the development of more efficient and low-cost catalysts to enhance industrial competitiveness.

[0003] Current industrialized PDH catalysts are mainly of two types, Pt-based catalysts (such as UOP Oleflex process) and Cr-based catalysts (such as Lummus Catofin process). Pt-based catalysts have high activity (single-pass conversion rate of 35%-40%), continuous regeneration, environmental friendliness, and other advantages, but rely on precious metals, have high costs, require raw material pre-desulfurization, have weak resistance to sintering, and are prone to reactor blockage due to carbon deposition. Cr-based catalysts (such as Lummus Catofin process) have low prices, wide raw material adaptability, and high single-pass conversion rates (about 45%), but require frequent regeneration (every 15-30 minutes to switch reactors) due to severe carbon deposition, have poor stability, and chromium species are prone to sintering and deactivation at high temperatures. Developing a propane dehydrogenation catalyst with high activity, high selectivity, and high stability is key to the development of propane dehydrogenation.

[0004] The traditional carrier of Cr-based catalysts is mainly gamma-Al2O3, but its strong acidity easily causes cracking side reactions. Titanium dioxide (TiO2) as a new carrier has become a research hotspot due to its unique properties. The acid sites on the surface of TiO2 are weakly acidic, reducing the occurrence of side reactions such as skeletal isomerization, cracking, and olefin polymerization, and improving propylene selectivity. It has a high specific surface area (120-160 m² / g), which can enhance the dispersion of active components and reduce the chromium loading (which can be reduced to 10-15%), thereby reducing environmental risks. The high strength of the titanium-oxygen bond allows it to withstand high-temperature sintering (>600°C), extending the catalyst's lifespan. Its non-toxic properties meet the trend of green chemical industry, reducing pollution problems caused by Cr(VI). In their research, Sai Chen et al. (DOI: 10.1126 / science.adp7379) used nickel and titanium dioxide to prepare a Ni@TiO2 catalyst. These two metals are abundant in earth's resources, but their activity is usually low. However, Ni@TiO XThe catalysts passivate Ni NPs with TiO X The coating is completely wrapped together. Under conditions related to industry, a propylene selectivity of nearly 94% is achieved, with high propane conversion and low deactivation rate. Studies have shown that the defective TiOxcoating, which is composed of four-coordinated Ti4C sites with Ov, has catalytic activity. Chinese patent CN116272977B uses defective titanium dioxide as a carrier to prepare a PtZn catalyst. By metal / non-metal ion doping or co-doping, in-situ reaction, and other methods, unsaturated Ti 3+ ions are successfully introduced into the titanium dioxide, and active metals such as platinum and zinc are loaded on the carrier, which can effectively disperse and stabilize metal particles. However, the preparation method of the carrier is very complex and difficult to apply in industry.

[0005] PDH technology is crucial for alleviating the contradiction between propylene supply and demand, but the cost and environmental protection bottleneck of the catalyst need to be broken through. Titanium dioxide carrier, with high selectivity, stability, and adjustable electronic properties, has become an ideal choice to replace Al2O3, especially when combined with cheap metals such as nickel and vanadium, it has both economy and efficiency. Future research should focus on the deep optimization of the interaction mechanism between the carrier and the active component, and promote the upgrading of PDH to green and low-carbon. SUMMARY

[0006] The present application provides a chromium-based dehydrogenation catalyst with a defective carrier and a preparation method. The low-carbon alkane chromium-based dehydrogenation catalyst provided by the present application uses a mixture of defective titanium dioxide and aluminum oxide as a carrier. By in-situ reduction and reaction reduction, unsaturated Ti 3+ ions are successfully introduced into the titanium dioxide, and the synergistic effect of the carrier and the active component chromium can effectively improve the catalytic activity and increase the stability of the catalyst. Doping with rare earth metals and transition metals can adjust the state of the active component on the surface of the catalyst, increase the selectivity, and adjust the acid sites on the surface of the carrier to increase the activity of the catalyst. The phase change of γ-Al2O3 is inhibited, the structure of the carrier is strengthened, a chromium-containing metal bond is formed, and the chromium material becomes more stable, thus increasing the overall stability of the catalyst. In addition, the production of this catalyst is simple and easy to obtain, the preparation process is simple, and it can be produced efficiently, stably, and economically using existing production lines, which can effectively replace the existing traditional chromium-based dehydrogenation catalyst.

[0007] To achieve the above technical purposes, the technical scheme provided by the present application is as follows: A chromium-based dehydrogenation catalyst prepared by using a carrier with defect state, the catalyst contains the following components in the mass fraction based on the total mass of the dry base: 3-30% of chromium oxide, 0.1-5% of a first additive, 0.1-5% of a second additive, and the rest is the carrier.

[0008] Specifically, in the preparation method of the low-carbon alkane chromium-based dehydrogenation catalyst using the mixture of the titanium dioxide with defect state and the aluminum oxide as the carrier, the dehydrogenation active substance and the additive are introduced by the impregnation method, and the coordination unsaturated Ti 3+ ions are introduced by high-temperature hydrogen reduction. The dehydrogenation active component can be in the state of isolated chromium and oligomer, polymeric chromium, and the multiple states are distributed on the surface of the catalyst, preferably uniformly distributed, and controlled by the physical indexes of the additive and the carrier.

[0009] Further, the carrier is the mixture of the titanium dioxide and the aluminum oxide, the specific surface area of the carrier is 50-300 m 2 / g, and the bulk density is 0.5-2 g / ml.

[0010] Further, the chromium in the chromium oxide is derived from one or more of sodium chromate, sodium dichromate, potassium chromate, potassium dichromate, ammonium dichromate, chromic acid, chromium chloride, chromium acetylacetate, potassium chromosulfate, chromium trioxide, chromium peroxide, lead chromate, chromium nitride, chromium nitrate and chromium fluoride.

[0011] Further, the transition metal element is derived from one or more of transition metal powder, transition metal halide, transition metal oxide, transition metal sulfide, transition metal sulfate, transition metal nitrate, transition metal acetate and transition metal oxalate.

[0012] Further, the rare earth metal element is derived from one or more of rare earth metal powder, rare earth metal halide, rare earth metal oxide, rare earth metal sulfide, rare earth metal sulfate, rare earth metal nitrate, rare earth metal acetate and rare earth metal oxalate.

[0013] The application also provides a preparation method of the chromium-based dehydrogenation catalyst prepared by using the carrier with defect state, the mixture of the titanium dioxide with defect state and the aluminum oxide is used as the carrier, the chromium oxide is used as the dehydrogenation active substance, the mixture of one or more of transition metals is used as the first additive, and the mixture of one or more of rare earth metals is used as the second additive; after the carrier loaded with the chromium and the additive catalyst is calcined to form stable oxides, the coordination unsaturated Ti 3+ ions are introduced by the in-situ reduction or reaction reduction method.

[0014] Specifically, the strong acid sites on the surface of the alumina carrier doped with TiO2 are reduced, reducing the occurrence of side reactions such as skeletal isomerization, cracking and olefin polymerization, and improving the propylene selectivity. The successful introduction of the unsaturated Ti 3+ The synergistic effect of the ion, the carrier and the active component chromium effectively improves the catalytic activity and increases the stability of the catalyst. The first and second additives adjust the existing state of the active component on the surface of the catalyst and the acid sites on the surface of the carrier, so that the catalyst has higher activity. The phase transformation of gamma-Al2O3 is inhibited, the carrier structure is strengthened, the chromium-containing metal bond is formed, and the chromium material becomes more stable, thus increasing the overall stability of the catalyst.

[0015] Further, the method specifically comprises the following steps: Step 1: preparing soluble solutions containing chromium, transition metals and rare earth metals respectively, and mixing them into a mixed solution; Step 2: preparing a cylindrical carrier mixed with titanium dioxide and alumina; Step 3: impregnating, aging, drying and calcining the mixed solution of step 1 and the carrier of step 2 to obtain a catalyst precursor; Step 4: reducing the catalyst precursor to obtain a low-carbon alkane chromium dehydrogenation catalyst with a carrier of a mixture of titanium dioxide and alumina in a defect state.

[0016] Further, in step 2, the preparation method of the cylindrical carrier mixed with titanium dioxide and alumina comprises the following steps: The appropriate amount of anatase nano titanium powder and aluminum stone, 3wt%-15wt% of 65% nitric acid solvent and 3wt%-15wt% of sesbania powder of the powder mass, and appropriate amount of water are mixed into plastic mud; the mud is extruded into a cylindrical strip of φ2-5mm to obtain a carrier precursor; the carrier precursor is dried at 60-120℃ and calcined at 300-600℃ for 2-10 hours to obtain a cylindrical carrier mixed with titanium dioxide and alumina.

[0017] Further, in step 3, the aging time is 1-10h, the drying time is 1-10h, the calcination temperature is 650-950℃, and the calcination time is 2-10h.

[0018] Further, in step 4, the reduction treatment method is to reduce the catalyst precursor by using hydrogen at 400-600℃ for 2-4 hours, the reactor is thoroughly purged with nitrogen before hydrogen is introduced to prevent the presence of air, and the temperature is lowered under a nitrogen atmosphere.

[0019] The present application has the following beneficial effects: The low-carbon alkane chromium dehydrogenation catalyst with the mixture of titanium dioxide and aluminum oxide in defect state as the carrier can be applied to the fixed bed process, a) the composite carrier of titanium dioxide and aluminum oxide has good weak acidity, reduces the occurrence of side reactions such as skeletal isomerization, cracking and olefin polymerization, so that the catalyst has higher target product selectivity. b) the composite carrier of titanium dioxide and aluminum oxide has high specific surface area (80-120 m² / g), which can enhance the dispersion of active components, reduce the chromium load (which can be reduced to 10-15%), and reduce the environmental risk. c) the introduction of coordination unsaturated Ti 3+ ions, the synergistic effect of the carrier and the active component chromium effectively improves the catalytic activity and increases the stability of the catalyst. e) the first and second additives adjust the existing state of the active component on the surface of the catalyst and the acidic sites on the surface of the carrier, so that the catalyst has higher activity. f) the phase change of γ-Al2O3 is inhibited, the carrier structure is strengthened, the chromium-containing metal bond is formed, and the chromium material becomes more stable, thus increasing the overall stability of the catalyst. Due to its excellent selectivity and stability, the anti-coking ability in the low-carbon alkane reaction process is significantly enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a method flowchart; Figure 2 is the XPS characterization of the TiO2-Al2O3 carrier before and after reduction. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0023] As Figure 1 The method flowchart of the present application is shown.

[0024] Example 1 A preparation method of a chromium dehydrogenation catalyst with a carrier having a defect state, comprising the following steps: Step 1: prepare a mixed solution containing chromium anhydride, nickel nitrate and lanthanum nitrate.

[0025] Step 2: Preparation of a cylindrical carrier mixed with titanium dioxide and aluminum oxide: Take an appropriate amount of aluminum stone and anatase nano titanium powder with a dry basis mass ratio of 1:1, add 4wt% of 65% nitric acid solvent and 3wt% of sesbania powder based on the mass of the powder, and an appropriate amount of water, and mix into a plastic mud. The mud is extruded into a φ3mm cylindrical strip by a screw extruder, and the extrusion pressure and speed are controlled to avoid breakage, and a carrier precursor is obtained. Dry it at 60°C, calcine at 400°C for 4 hours, and obtain a cylindrical carrier mixed with titanium dioxide and aluminum oxide.

[0026] Step 3: The cylindrical carrier mixed with titanium dioxide and aluminum oxide is impregnated with an equal volume of the mixed solution for 6 hours, aged for 10 hours, dried at 80°C for 10 hours, and calcined at 700°C for 6 hours to obtain a catalyst precursor. The catalyst content is the following mass fraction of components based on the total mass of its dry basis: Cr2O3 18%, NiO 1%, La2O3 1%.

[0027] Step 4: Reduction treatment of the catalyst precursor, reduction treatment of the catalyst precursor with hydrogen at 500°C for 2 hours, the reactor is thoroughly purged with nitrogen before hydrogen is introduced to prevent the presence of air, and the temperature is lowered under a nitrogen atmosphere to avoid contact with air, to obtain catalyst 1.

[0028] Example 2 A method for preparing a chromium-based dehydrogenation catalyst with a carrier having a defect state, comprising the following steps: Step 1: Preparation of a mixed solution containing chromium anhydride, vanadium trichloride, and lanthanum nitrate.

[0029] Step 2: Preparation of a cylindrical carrier mixed with titanium dioxide and aluminum oxide: Take an appropriate amount of aluminum stone and anatase nano titanium powder with a dry basis mass ratio of 1:1, add 4wt% of 65% nitric acid solvent and 3wt% of sesbania powder based on the mass of the powder, and an appropriate amount of water, and mix into a plastic mud. The mud is extruded into a φ3mm cylindrical strip by a screw extruder, and the extrusion pressure and speed are controlled to avoid breakage, and a carrier precursor is obtained. Dry it at 60°C, calcine at 400°C for 4 hours, and obtain a cylindrical carrier mixed with titanium dioxide and aluminum oxide.

[0030] Step 3: The cylindrical carrier mixed with titanium dioxide and aluminum oxide is impregnated with an equal volume of the mixed solution for 6 hours, aged for 10 hours, dried at 80°C for 10 hours, and calcined at 700°C for 6 hours to obtain a catalyst precursor. The catalyst content is the following mass fraction of components based on the total mass of its dry basis: Cr2O3 18%, VO2 1%, La2O3 1%.

[0031] Step 4: Reduction treatment of the catalyst precursor, the catalyst precursor is reduced by hydrogen at 500 ℃ for 2 hours, the reactor is thoroughly purged by nitrogen before hydrogen is introduced to prevent the presence of air. And cool down under nitrogen atmosphere to avoid contact with air, catalyst 2 is obtained.

[0032] Example 3 A preparation method of a chromium-based dehydrogenation catalyst prepared by a carrier with a defect state, comprising the following steps: Step 1: Prepare a mixed solution containing chromium anhydride and nickel nitrate.

[0033] Step 2: Prepare a cylindrical carrier mixed with titanium dioxide and aluminum oxide, take an appropriate amount of aluminum stone and anatase nano titanium powder with a dry basis mass ratio of 1:1, add 4wt% of 65% nitric acid solvent and 3wt% of sesbania powder based on the mass of the powder, and an appropriate amount of water, and mix into a plastic mud. The mud is extruded into a φ3mm cylindrical strip by a screw extruder, the extrusion pressure and speed are controlled to avoid breakage, and a carrier precursor is obtained. Dry it at 60℃, calcine it at 400℃ for 4 hours, and obtain a cylindrical carrier mixed with titanium dioxide and aluminum oxide.

[0034] Step 3: The cylindrical carrier mixed with titanium dioxide and aluminum oxide is impregnated with an equal volume of the mixed solution for 6 hours, aged for 10 hours, dried at 80℃ for 10 hours, and calcined at 700℃ for 6 hours to obtain a catalyst precursor. The catalyst contains the following mass fractions based on the total mass of its dry basis: Cr2O318%, NiO 1%. Step 4: Reduction treatment of the catalyst precursor, the catalyst precursor is reduced by hydrogen at 500 ℃ for 2 hours, the reactor is thoroughly purged by nitrogen before hydrogen is introduced to prevent the presence of air. And cool down under nitrogen atmosphere to avoid contact with air, catalyst 3 is obtained.

[0035] Example 4 A preparation method of a chromium-based dehydrogenation catalyst prepared by a carrier with a defect state, comprising the following steps: Step 1: Prepare a mixed solution containing chromium anhydride and lanthanum nitrate.

[0036] Step 2: Prepare a cylindrical carrier mixed with titanium dioxide and aluminum oxide, take an appropriate amount of aluminum stone and anatase nano titanium powder with a dry basis mass ratio of 1:1, add 4wt% of 65% nitric acid solvent and 3wt% of sesbania powder based on the mass of the powder, and an appropriate amount of water, and mix into a plastic mud. The mud is extruded into a φ3mm cylindrical strip by a screw extruder, the extrusion pressure and speed are controlled to avoid breakage, and a carrier precursor is obtained. Dry it at 60℃, calcine it at 400℃ for 4 hours, and obtain a cylindrical carrier mixed with titanium dioxide and aluminum oxide.

[0037] Step 3: The cylindrical carrier mixed with titanium dioxide and aluminum oxide is impregnated with the mixed solution in equal volume for 6 hours, dried at 80°C for 10 hours after aging for 10 hours, calcined at 700°C for 6 hours to obtain the catalyst precursor. The catalyst contains the following components in mass fraction based on the total mass of its dry basis: Cr2O318%, La2O31%.

[0038] Step 4: The catalyst precursor is reduced, and the catalyst precursor is reduced by hydrogen at 500°C for 2 hours. The reactor is thoroughly purged with nitrogen before hydrogen is introduced to prevent the presence of air. The temperature is lowered under a nitrogen atmosphere to avoid contact with air to obtain catalyst 4.

[0039] Example 5 A method for preparing a chromium-based dehydrogenation catalyst prepared by a carrier with a defect state, comprising the following steps: Step 1: Prepare a mixed solution containing chromium anhydride, nickel nitrate, and lanthanum nitrate.

[0040] Step 2: Prepare a 30% TiO2-70% Al2O3 cylindrical carrier mixed with titanium dioxide and aluminum oxide. Weigh an appropriate amount of aluminum stone and anatase nano-titanium powder with a dry mass ratio of 7:3, add 4wt% of 65% nitric acid solvent and 3wt% of sesbania powder based on the mass of the powder, and add an appropriate amount of water to mix into a plastic mud. The mud is extruded into a φ3mm cylindrical strip by a screw extruder, and the extrusion pressure and speed are controlled to avoid breakage to obtain a carrier precursor. Dry it at 60°C and calcine it at 400°C for 4 hours to obtain a 30% TiO2-70% Al2O3 cylindrical carrier mixed with titanium dioxide and aluminum oxide.

[0041] Step 3: The 30% TiO2-70% Al2O3 cylindrical carrier is impregnated with the mixed solution in equal volume for 6 hours, dried at 80°C for 10 hours after aging for 10 hours, calcined at 700°C for 6 hours to obtain the catalyst precursor. The catalyst contains the following components in mass fraction based on the total mass of its dry basis: Cr2O3 18%, NiO 1%, La2O31%.

[0042] Step 4: The catalyst precursor is reduced, and the catalyst precursor is reduced by hydrogen at 500°C for 2 hours. The reactor is thoroughly purged with nitrogen before hydrogen is introduced to prevent the presence of air. The temperature is lowered under a nitrogen atmosphere to avoid contact with air to obtain catalyst 5.

[0043] Example 6 A method for preparing a chromium-based dehydrogenation catalyst prepared by a carrier with a defect state, comprising the following steps: Step 1: Prepare a mixed solution containing chromium anhydride, nickel nitrate, and lanthanum nitrate.

[0044] Step 2: Preparation of a 10% TiO2-90% Al2O3 cylindrical carrier mixed with titanium dioxide and aluminum oxide, take an appropriate amount of dry basis aluminum stone and anatase nano titanium powder with a mass ratio of 7:3, add 4wt% of 65% nitric acid solvent and 3wt% of sesbania powder of the powder mass, and an appropriate amount of water, and mix into a plastic mud. The mud is extruded into a φ3mm cylindrical strip by a screw extruder, and the extrusion pressure and speed are controlled to avoid breakage, and a carrier precursor is obtained. Dry it at 60°C, calcine at 400°C for 4 hours, and obtain a 10% TiO2-90% Al2O3 cylindrical carrier mixed with titanium dioxide and aluminum oxide.

[0045] Step 3: The obtained 10% TiO2-90% Al2O3 cylindrical carrier is impregnated with the mixed solution at the same volume for 6 hours, aged for 10 hours, dried at 80°C for 10 hours, and calcined at 700°C for 6 hours to obtain a catalyst precursor. The catalyst content is the following mass fraction of components based on the total mass of its dry basis: Cr2O3 18%, NiO 1%, La2O3 1%.

[0046] Step 4: The catalyst precursor is subjected to reduction treatment, and the catalyst precursor is reduced with hydrogen at 500°C for 2 hours. The reactor is thoroughly purged with nitrogen before hydrogen is introduced to prevent the presence of air, and the temperature is lowered under a nitrogen atmosphere to avoid contact with air, and catalyst 6 is obtained.

[0047] Comparative Example 1 A method for preparing a chromium-based dehydrogenation catalyst with a carrier having a defect state, comprising the following steps: Step 1: Preparation of a mixed solution containing chromium anhydride.

[0048] Step 2: Preparation of a cylindrical carrier mixed with titanium dioxide and aluminum oxide: take an appropriate amount of dry basis aluminum stone and anatase nano titanium powder with a mass ratio of 1:1, add 4wt% of 65% nitric acid solvent and 3wt% of sesbania powder of the powder mass, and an appropriate amount of water, and mix into a plastic mud. The mud is extruded into a φ3mm cylindrical strip by a screw extruder, and the extrusion pressure and speed are controlled to avoid breakage, and a carrier precursor is obtained. Dry it at 60°C, calcine at 400°C for 4 hours, and obtain a cylindrical carrier mixed with titanium dioxide and aluminum oxide.

[0049] Step 3: The cylindrical carrier mixed with titanium dioxide and aluminum oxide is impregnated with the mixed solution at the same volume for 6 hours, aged for 10 hours, dried at 80°C for 10 hours, and calcined at 700°C for 6 hours to obtain a catalyst precursor; the catalyst content is the following mass fraction of components based on the total mass of its dry basis: Cr2O318%, La2O3 1%.

[0050] Comparative Example 2 A method for preparing a chromium-based dehydrogenation catalyst with a carrier having a defect state, comprising the following steps: Step 1: preparing a mixed solution containing chromium anhydride, nickel nitrate and lanthanum nitrate.

[0051] Step 2: preparing a cylindrical carrier mixed with titanium dioxide and aluminum oxide: weighing a proper amount of aluminum stone and anatase nano-titanium powder with a dry basis mass ratio of 1:1, adding 4wt% of 65% nitric acid solvent and 3wt% of sesbania powder based on the mass of the powder, and a proper amount of water, and mixing them into a plastic mud. The mud is extruded into a cylindrical strip with a diameter of 3mm by a screw extruder, and the extrusion pressure and speed are controlled to avoid breakage, to obtain a carrier precursor. The carrier precursor is dried at 60°C and calcined at 400°C for 4 hours to obtain a cylindrical carrier mixed with titanium dioxide and aluminum oxide.

[0052] Step 3: immersing the cylindrical carrier mixed with titanium dioxide and aluminum oxide in the mixed solution with an equal volume for 6 hours, and after aging for 10 hours, drying at 80°C for 10 hours and calcining at 700°C for 6 hours to obtain a catalyst precursor; the catalyst contains the following components with the following mass fractions based on the total mass of the dry basis: Cr2O3 18%, NiO 1%, La2O3 1%.

[0053] Test Example I. Propane dehydrogenation test The catalysts 1-6 and the comparative example 1-2 were subjected to propane dehydrogenation tests, respectively; The process flow adopted was the existing process flow, which was not described in detail in the examples, and the control parameters in the process flow were as follows: the propane volume space velocity was 1000h-1, an appropriate amount of nitrogen was introduced, the propane partial pressure was maintained at 50kPa, and the total pressure of the reaction system was normal pressure; the bed temperature was 570°C; the results are shown in Table 1, Table 1 Propane dehydrogenation test of catalysts 1-6 and comparative example 1-2 As can be seen from Table 1, the introduction of coordination unsaturated Ti 3+ ions in the carrier can effectively improve the propane conversion rate of the catalyst. Titanium dioxide and cheap metals (such as nickel and vanadium) are coordinated at the same time, which is both economical and efficient. The rare earth metal lanthanum is beneficial to improve the propane conversion rate of the catalyst.

[0054] II. Propane dehydrogenation performance test of catalyst 1 at different temperatures The process flow adopted was the existing process flow, which was not described in detail in the examples, and the control parameters in the process flow were as follows: the propane volume space velocity was 1000h -1 , an appropriate amount of nitrogen was introduced, the propane partial pressure was maintained at 50kPa, and the total pressure of the reaction system was normal pressure; the bed temperature was 550-610°C; the results are shown in Table 2, Table 2 is the performance test of catalyst 1 in propane dehydrogenation at different temperatures As shown in Table 2, the low-carbon alkane chromium dehydrogenation catalyst with the mixture of defective titanium dioxide and aluminum oxide as the carrier has higher reaction activity and stability.

[0055] In addition, X-ray photoelectron spectroscopy analysis was performed on the TiO2-Al2O3 carrier before and after reduction, and was marked as TiO2-Al2O3 and TiO2-Al2O3-Ti, respectively. 3+ The Ti 2p spectrum and fitting results of the two carriers are shown in Figure 2 The Ti 2p peak in the fitting results of TiO2-Al2O3-Ti 3+ is divided into three peaks, which are Ti 3+ 2p 3 / 2 (458.0 eV), Ti 4+ 2p 3 / 2 (458.6 eV), and Ti 4+ 2p 1 / 2 (464.1 eV).

[0056] In summary, the low-carbon alkane chromium dehydrogenation catalyst with the mixture of defective titanium dioxide and aluminum oxide as the carrier has good dehydrogenation performance in the propane dehydrogenation reaction, and compared with the existing traditional chromium dehydrogenation catalyst, the mixture of defective titanium dioxide and aluminum oxide as the carrier reduces the occurrence of side reactions such as skeletal isomerization, cracking, and olefin polymerization, so that the catalyst has higher dehydrogenation target product selectivity and better stability. In addition, the production raw materials of the low-carbon alkane chromium dehydrogenation catalyst are simple and easy to obtain, the preparation process is simple, and the existing production line can be used efficiently, stably, and economically for production, which can effectively replace the existing traditional chromium dehydrogenation catalyst.

[0057] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements, and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

[0058] The above specific embodiments are detailed descriptions of the present application, and cannot be considered as limiting the specific embodiments of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, some simple deductions and replacements can be made without departing from the concept of the present application, and all of them should be considered as falling within the protection scope of the present application.

Claims

1. A chromium-based dehydrogenation catalyst prepared with a support having a defect state, characterized in that, The catalyst contains the following components in the following mass fractions based on the total mass of the dry base: 3-30% chromium oxide, 0.1-5% first additive, 0.1-5% second additive, and the rest is a carrier.

2. The chromium-based dehydrogenation catalyst prepared with the support having a defect state according to claim 1, wherein the chromium-based dehydrogenation catalyst is prepared by impregnating the support having a defect state with a chromium compound and then calcining the impregnated support. The carrier is a mixed carrier of titanium dioxide and aluminum oxide, the specific surface area of the carrier is 50-300 m 2 / g, and the bulk density is 0.5-2 g / ml.

3. The chromium-based dehydrogenation catalyst prepared on a support with defective states according to claim 1, characterized in that, The chromium in the chromium oxide is derived from one or more of sodium chromate, sodium dichromate, potassium chromate, potassium dichromate, ammonium dichromate, chromic acid, chromium chloride, chromium acetylacetonate, potassium chromic sulfate, chromium trioxide, chromium peroxide, lead chromate, chromium nitride, chromium nitrate, and chromium fluoride.

4. The chromium-based dehydrogenation catalyst prepared on a support with defective states according to claim 1, characterized in that, The transition metal element is derived from one or more of transition metal powder, transition metal halide, transition metal oxide, transition metal sulfide, transition metal sulfate, transition metal nitrate, transition metal acetate, and transition metal oxalate.

5. The chromium-based dehydrogenation catalyst prepared on a support with defective states according to claim 1, characterized in that, The rare earth metal element is derived from one or more of rare earth metal powder, rare earth metal halide, rare earth metal oxide, rare earth metal sulfide, rare earth metal sulfate, rare earth metal nitrate, rare earth metal acetate, and rare earth metal oxalate.

6. A preparation method of a chromium-based dehydrogenation catalyst with a defect state carrier prepared according to any one of claims 1-5, comprising the following steps: The catalyst comprises a mixture of titanium dioxide and aluminum oxide as a carrier, chromium oxide as a dehydrogenation active material, a mixture of one or more transition metals as a first assistant, and a mixture of one or more rare earth metals as a second assistant. After the carrier is loaded with chromium and the assistant catalyst is calcined to form stable oxides, unsaturated Ti 3+ ions are introduced by in-situ reduction or reaction reduction.

7. The method of claim 6, wherein the method is characterized by the steps of: (a) providing a carrier having a defect state; (b) depositing a chromium compound on the carrier; (c) heating the carrier to a temperature of 300°C to 600°C; (d) cooling the carrier to room temperature; and (e) exposing the carrier to a reducing atmosphere. Specifically comprising the following steps: Step 1: separately prepare soluble solutions containing chromium, transition metal, and rare earth metal, and mix them into a mixed solution; Step 2: prepare a cylindrical carrier mixed with titanium dioxide and aluminum oxide; Step 3: after impregnation, aging, drying, and calcination of the mixed solution of step 1 and the carrier of step 2, a catalyst precursor is obtained; Step 4: after reduction treatment of the catalyst precursor, a low-carbon alkane chromium-based dehydrogenation catalyst with a defect state carrier of a mixture of titanium dioxide and aluminum oxide is obtained.

8. The method of claim 7, wherein the chromium-based dehydrogenation catalyst is prepared by using a support having a defect state. In step 2, the preparation method of the cylindrical carrier mixed with titanium dioxide and aluminum oxide comprises the following steps: An appropriate amount of anatase nanometer titanium powder and aluminum stone, 3wt%-15wt% of 65% nitric acid solvent based on the mass of the powder, 3wt%-15wt% of sesbania powder based on the mass of the powder, and an appropriate amount of water are mixed into a plastic mud; the mud is extruded into a cylindrical strip with a diameter of φ2-5mm to obtain a carrier precursor; the carrier precursor is dried at 60-120℃ and calcined at 300-600℃ for 2-10 hours to obtain a cylindrical carrier mixed with titanium dioxide and aluminum oxide.

9. The method for preparing a chromium-based dehydrogenation catalyst based on a defective support according to claim 7, characterized in that, In step 3, the aging time is 1-10 h, the drying time is 1-10 h, the calcination temperature is 650-950℃, and the calcination time is 2-10 h.

10. The method of claim 7, wherein the chromium-based dehydrogenation catalyst is prepared by using a support having a defect state. In step 4, the reduction treatment method is to reduce the catalyst precursor with hydrogen at 400-600℃ for 2-4 hours, the reactor is thoroughly purged with nitrogen before hydrogen is introduced to prevent the presence of air, and the temperature is lowered under a nitrogen atmosphere.

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