WO2019029358A1 - 钼钒双金属氧化物催化剂及其在低碳烷烃化学链脱氢中的应用 - Google Patents

钼钒双金属氧化物催化剂及其在低碳烷烃化学链脱氢中的应用 Download PDF

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WO2019029358A1
WO2019029358A1 PCT/CN2018/096942 CN2018096942W WO2019029358A1 WO 2019029358 A1 WO2019029358 A1 WO 2019029358A1 CN 2018096942 W CN2018096942 W CN 2018096942W WO 2019029358 A1 WO2019029358 A1 WO 2019029358A1
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molybdenum
vanadium
oxygen
metal oxide
oxide catalyst
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French (fr)
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巩金龙
陈赛
曾亮
慕仁涛
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Tianjin University
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/28—Molybdenum
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    • B01J23/90—Regeneration or reactivation
    • B01J23/92—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J38/00—Regeneration or reactivation of catalysts, in general
    • B01J38/04—Gas or vapour treating; Treating by using liquids vaporisable upon contacting spent catalyst
    • B01J38/12—Treating with free oxygen-containing gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
    • C07C5/32—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with formation of free hydrogen
    • C07C5/321—Catalytic processes
    • C07C5/322—Catalytic processes with metal oxides or metal sulfides
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
    • C07C5/42—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with a hydrogen acceptor
    • C07C5/48—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with a hydrogen acceptor with oxygen as an acceptor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04—Alumina
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/063—Titanium; Oxides or hydroxides thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/08—Silica
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/02—Processes carried out in the presence of solid particles; Reactors therefor with stationary particles
    • B01J2208/023—Details
    • B01J2208/027—Beds
    • B01J2208/028—Beds rotating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2235/00—Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties
    • B01J2235/15—X-ray diffraction
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • C07C2523/24—Chromium, molybdenum or tungsten
    • C07C2523/28—Molybdenum
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the iron group metals or copper
    • C07C2523/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the iron group metals or copper combined with noble metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/584—Recycling of catalysts

Definitions

  • the present invention relates to a technique for dehydrogenating a lower alkane using a metal oxide, and more particularly to a method and application of a supported molybdenum vanadium double metal oxide for the oxidative dehydrogenation of a lower alkane to an olefin.
  • shale gas is rich in low-carbon alkanes. It is of great energy and environmental significance to convert low-carbon alkanes in shale gas into higher-value chemical products. In recent years, the use of alkane dehydrogenation to produce corresponding olefins has been fully developed.
  • the conventional oxygen-free dehydrogenation (PDH) technology uses Pt-based or Cr-based catalysts.
  • the PDH reaction has high selectivity for propylene under the catalytic conditions of Pt-based catalysts, but due to thermodynamic limitations.
  • the single pass conversion rate can not be effectively improved, and the oxygen-free dehydrogenation as the endothermic reaction consumes a lot of energy in the reaction stage; although the Cr-based catalyst solves the problem of high cost of the Pt-based catalyst, Cr is highly toxic to the environment and the human body, and thermodynamics The restrictions have not been resolved, prompting people to find a more economical and efficient way to produce propylene from propane.
  • aerobic dehydrogenation introduces molecular oxygen into the reaction system, breaking through thermodynamic constraints.
  • propane and propylene are prone to complete oxidation reaction to form CO 2 . It affects the selectivity and economy of the reaction, and there is a safety hazard in the mixing of reducing gas and oxygen.
  • the control of the reaction conditions is demanding, so industrial promotion is difficult.
  • C-ODH chemical chain oxidative dehydrogenation
  • the apparatus and process for propane chemical chain oxidative dehydrogenation are as shown in Fig. 1.
  • a metal oxide catalyst is disposed in a fixed bed reactor, and a gas switching device is disposed on the intake line, and the gas switching device is respectively used for the raw material gas.
  • the road, the inert gas path and the oxidizing gas path are connected and can be switched so that the intake line can be respectively connected to the raw material gas path, the inert gas gas path and the oxidizing gas path.
  • a raw material gas path for introducing a raw material low-carbon alkane into the fixed bed reactor, and an inert gas gas path for purging an inert atmosphere into the intake pipe and the fixed bed reactor to carry out the reaction under anaerobic conditions .
  • An oxidizing gas path for introducing oxygen or air into the fixed bed reactor to oxidatively regenerate the metal oxide catalyst.
  • the lower alkanes are reacted, and the activity of the metal oxide catalyst is monitored during the reaction, such as product composition, reaction time, metal oxide valence state, etc., when the metal oxide catalyst activity is near the limit, the oxygen gas path is replaced by oxygen or Air, in order to oxidize and regenerate the metal oxide catalyst, from a low-cost state to a high-valence state; after regeneration, the inert gas path is replaced to remove oxygen, the raw material gas path is replaced for reaction, and the oxidizing gas path is replaced for regeneration.
  • a reaction system using a combination of two or more fixed bed reactors ensures that at least one fixed bed reactor is in the reaction stage at any time, and the remaining fixed bed reactors are in a regeneration stage or a deoxygenation stage to achieve continuous production of the entire reaction process.
  • oxygen carriers for CL-ODH are mainly one-component metal oxides, including vanadium oxide, chromium oxide, tungsten oxide, and the like.
  • their lattice oxygen activity is affected by various factors, and it is not possible to activate propane carbon-hydrogen bonds to form propylene with high activity and high selectivity. Therefore, how to adjust the lattice oxygen activity reasonably and controllable by constructing composite metal oxides has important scientific and economic benefits.
  • a catalyst for the dehydrogenation of alkanes and used in fixed bed, moving bed and circulating fluidized bed reactors.
  • the catalyst of the invention is non-noble metal, non-toxic and harmless, and can be continuously reacted and regenerated in a reactor compatible with the catalyst. While maintaining high catalytic activity, the selectivity of the catalyst needs to be further improved.
  • the invention aims to overcome the defects of the prior art, such as thermodynamic limitation, low propylene selectivity and low reaction economy, and provides a molybdenum-vanadium double metal oxide catalyst and its chemical chain dehydrogenation in lower alkanes.
  • the application of the molybdenum-vanadium double metal oxide catalyst as an oxygen carrier the lattice oxygen in the oxygen carrier reacts with the hydrogen atom in the activated propane to form water, which effectively pushes the reaction to move in the direction of generating propylene.
  • the surface oxygen activity of the addition of Mo is significantly inhibited, and the conversion of propane reaction and the selectivity of propylene are significantly improved, which effectively improves the yield and reaction economy of propylene.
  • the molybdenum-vanadium double metal oxide catalyst is a solid solution composed of an oxide of a metal molybdenum and an oxide of a metal vanadium, and the molar ratio of the metal Mo to the metal V is 1: (4 to 30), preferably 1: (6 to 18).
  • Mo metal into the bulk lattice V 2 O 5 and V 2 O 5 causes the lattice distortion, molybdenum, vanadium, solid solution is formed.
  • the catalyst is a supported catalyst
  • the carrier is Al 2 O 3 , TiO 2 , SiO 2 or a molecular sieve
  • the mass percentage of the oxide of molybdenum ie, the mass of the oxide of molybdenum / the mass of the carrier
  • the mass percentage of vanadium oxide is 4 to 60%, preferably 40 to 60%.
  • Step 1 the ammonium metavanadate and oxalic acid are uniformly dispersed in deionized water, and then mixed with ammonium molybdate according to the atomic ratio of molybdenum to vanadium to form an immersion liquid;
  • Step 2 immersing the carrier in the impregnation liquid prepared in the step 1 for equal volume impregnation
  • Step 3 the carrier impregnated in step 2 is dried at room temperature of 20 to 25 degrees Celsius for 8 to 12 hours, then dried at 70 to 90 ° C for 8 to 12 hours, and finally calcined at 500 to 600 ° C for 2 to 4 hours in an air atmosphere.
  • a molybdenum-vanadium double metal oxide catalyst having a molecular formula of Mo 1 V y is obtained , wherein y represents the amount of V relative to 1 mol of Mo, that is, the molar ratio of metal V to metal Mo.
  • the mass ratio of oxalic acid to ammonium metavanadate is (2.8 to 3): (1.5 to 2).
  • the support is Al 2 O 3 , TiO 2 , SiO 2 or molecular sieves.
  • step 3 it is dried at room temperature of 20 to 25 degrees Celsius for 10 to 12 hours, then dried at 80 to 90 ° C for 10 to 12 hours, and finally calcined at 550 to 600 ° C for 2 to 4 hours in an air atmosphere.
  • step 3 the molybdenum-vanadium double metal oxide catalyst powder is tableted to form a particulate catalyst having a size of 20 to 40 mesh.
  • the use of the catalyst of the invention in the dehydrogenation of a lower alkane chemical chain the reaction is carried out under an anaerobic condition, the catalyst is used as an oxygen carrier, and the oxidative dehydrogenation reaction with the lower alkane is carried out, and the lattice oxygen in the oxygen carrier is low. Hydrogen atoms in the carbon alkane combine to form water, the oxygen carrier is reduced to a lower state, and the lower alkane is oxidized to the corresponding olefin.
  • the lower alkane is an alkane of at least one carbon atom, more preferably a linear alkane comprising one carbon atom, and most preferably, the alkane comprises preferably ethane, propane, n-butane or isobutane.
  • the lattice oxygen in the catalyst participates in the reaction, so as the reaction proceeds, the lattice oxygen is gradually consumed, resulting in a decrease in catalyst activity, and therefore, it is necessary to carry out cyclic regeneration of the catalyst.
  • the low-cost oxygen carrier is oxidized to a high valence state by reaction with air or oxygen, and the lattice oxygen is regained and recycled back to the reactor for reaction.
  • the gas-solid two-phase (the gas phase is mainly the raw material low-carbon alkane and the product low-carbon olefin, and the solid phase is mainly the metal oxide oxygen carrier).
  • the contact modes mainly include gas-solid countercurrent contact and gas-solid cocurrent contact.
  • kind of operation Specifically selected fixed bed reactors, moving bed reactors or circulating fluidized beds.
  • the catalyst and quartz sand are mixed and used uniformly, and the reaction is carried out under normal pressure at a reaction temperature of 450 to 500 ° C, nitrogen gas is introduced to remove oxygen and air, and then propane is introduced, and the total flow rate of propane and nitrogen is 20-50 ml/min, the propane volume percentage is 10 to 30%.
  • the mass ratio of the catalyst to the quartz sand is (0.2 to 1):1, preferably (0.5 to 0.8):1.
  • the present invention has benefits such as:
  • the present invention is a supported double metal oxide, and vanadium oxide and molybdenum oxide form a bimetallic composite oxide.
  • the selectivity of lower olefins is significantly improved compared to a single vanadium oxide; the conversion of lower alkanes is improved compared to a single molybdenum oxide.
  • By adjusting the ratio of molybdenum to vanadium the optimum values of conversion and selectivity can be obtained.
  • the oxygen carrier of the present invention is prepared by the impregnation method, has simple operation and low cost.
  • the oxygen carrier can maintain a higher conversion and selectivity after lattice oxygen consumption.
  • the oxygen carrier basically maintains the stability of structure and performance after undergoing several redox regeneration cycles, and the conversion rate and selectivity are basically unchanged.
  • the catalyst needs to be supplied with oxygen or air during the regeneration stage. On the one hand, it can oxidize the low-value oxygen carrier to supplement the lattice oxygen, and on the other hand, the oxygen carrier is oxidized to an exothermic reaction, and is accompanied by the burning of carbon deposits.
  • the heat can enter the reactor through the thermal conduction of the oxygen carrier to provide heat for the dehydrogenation reaction, and the heat can be completely matched by adjusting the mass of the oxygen carrier.
  • the alkane dehydrogenation catalyst of the present invention is used in a chemical chain dehydrogenation reactor, and the outstanding advantage of the present invention is that the single-pass conversion of the alkane is high, the selectivity of the desired product olefin is high, and the catalyst is compared with the prior art.
  • the active component is a non-noble metal and has no adverse effect on the environment and is free of the introduction of a vulcanization medium.
  • Figure 1 is a schematic illustration of the apparatus and process for the dehydrogenation of propane chemical chain used in the present invention.
  • Figure 2 is a graph showing the results of activity tests using different amounts of Mo added catalyst in the chemical chain dehydrogenation of propane.
  • Figure 3 is a graph showing the results of activity tests at different temperatures during the dehydrogenation of propane chemical chain.
  • Figure 4 is a graph showing the results of activity tests at different space velocities during propane chemical chain dehydrogenation.
  • Figure 5 is a graph showing the results of activity tests at different reaction times when VO x and Mo1V6 catalysts were used in the chemical chain dehydrogenation of propane, respectively.
  • Figure 6 is a graph showing the results of H 2 -TPR test of fresh oxygen carriers (catalysts) prepared by the present invention.
  • Figure 7 is a graph showing the results of XRD test of a fresh oxygen carrier (catalyst) prepared by the present invention.
  • Figure 8 is a graph showing the results of a cycle stability test using a catalyst Mo1V6 for a reaction regeneration cycle in a chemical chain dehydrogenation process of propane.
  • Fig. 9 is a graph showing the results of oxygen carrier test before and after the reaction regeneration cycle using the catalyst Mo1V6 in the chemical chain dehydrogenation of propane.
  • Figure 10 is a graph showing the results of lattice oxygen consumption of the catalysts VO x and Mo1V6 at different reaction times in the chemical chain dehydrogenation of propane.
  • Figure 11 is a schematic diagram showing the phase changes of the catalysts VO x and Mo1V6 at different reaction times in the chemical chain dehydrogenation of propane.
  • step 1 1.8 parts by mass of ammonium metavanadate (NH 4 VO 3 ) and 2.9 parts by mass of oxalic acid (C 2 H 2 O 4 ) are dissolved in 3 mL of deionized water. After the reaction is completed, the atomic ratio of molybdenum to vanadium is added. A certain mass of ammonium molybdate ((MH 4 ) 6 Mo 7 O 24 .4H 2 O), 2.0 parts by mass of Al 2 O 3 was immersed in the above solution.
  • ammonium molybdate (MH 4 ) 6 Mo 7 O 24 .4H 2 O)
  • Step 2 the material obtained in the step 1 is dried at room temperature 25 ° C for 12 h, then dried at 70 ° C for 12 h, and finally calcined at 600 ° C for 4 h in an air atmosphere to obtain a molybdenum-vanadium bimetallic composite oxide supported on alumina.
  • Its molecular formula is Mo 1 V y .
  • step 3 a solid powder of Mo 1 V y is tableted into a pelletized catalyst having a size of 20 to 40 mesh.
  • the reaction was carried out by the method of Example 1, except that the mass of the ammonium molybdate of the step (1) was 0, and a VO x catalyst was obtained.
  • Step 1 Take 1.472 parts by mass of ammonium molybdate ((MH 4 ) 6 Mo 7 O 24 .4H 2 O), dissolve in 3 mL of deionized water, and immerse 2.0 parts by mass of Al 2 O 3 in the above solution, and dry at room temperature. 12h, dried at 80 ° C for 2h;
  • Step 2 the material obtained in the step 1 is dried at room temperature 25 ° C for 12 h, then dried at 70 ° C for 12 h, and finally calcined at 600 ° C for 4 h in an air atmosphere to obtain molybdenum oxide supported on alumina, the molecular formula of which is MoO x .
  • step 3 the MoO x solid powder is tableted into a pelletized catalyst having a size of 20 to 40 mesh.
  • the VO x , Mo 1 V y , and MoO x oxygen carriers (ie, three kinds of oxide catalysts) obtained in Examples 1 to 3 were respectively weighed and mixed with 0.25-0.8 g and 2 mL of quartz sand (SiC), and added to a fixed bed tube.
  • the reactor was tested at 450 to 500 ° C under normal pressure.
  • N 2 was introduced to exclude oxygen and air, followed by propane, wherein the total flow of propane and nitrogen was 21 ml/min and the volume fraction of propane was 20%.
  • the product composition is detected by gas chromatography.
  • the propane conversion rate is calculated by the following formula:
  • the gas phase selectivity of the product is calculated by the following formula:
  • the gas phase product A includes: C 3 H 6 , CO x (carbon oxides, ie, carbon monoxide, carbon dioxide), CH 4 , C 2 H 6 , C 2 H 4 .
  • the catalyst reactivity of the above examples was the activity at a reaction time of 5 min.
  • the histogram is the product conversion rate or selectivity, and the star corresponds to the propylene yield.
  • the highest selectivity of propylene under Mo1V6 was 89%; pure vanadium oxide VO x , surface oxygen activity is higher, resulting in complete oxidation of propane or propylene to CO x ; pure molybdenum oxide MoO x , low surface oxidation, resulting in lower propane conversion, complete oxidation of propane or propylene to lower CO x ( VO x , Mo 1 V y , MoO x , using both VO x and MoO x ).
  • the molybdenum-vanadium double metal oxide can effectively increase the selectivity of propylene while suppressing the surface oxygen activity. Excessive addition of molybdenum results in a decrease in the conversion of propane and the selectivity of propylene. Therefore, the optimum Mo addition amount of molybdenum vanadium double metal oxide is Mo1V6. (The product represented by the histogram in each figure is identical to Figure 2).
  • the airspeed adjustment is achieved by changing the mass of the catalyst while the gas flow rate remains unchanged. As the reaction space velocity decreases, the conversion of propane increases, but the selectivity of propylene decreases, mainly because of the retention. The reduction in time causes the propane or propylene to be completely oxidized by the more active oxide on the surface to form CO x .
  • Figure 5 is a graph showing the activity test results at different reaction times when using VO x and Mo1V6 catalysts in the chemical chain dehydrogenation process of propane.
  • the histogram corresponds to the propylene yield
  • the curve 1-4 corresponds to the curve of the metal V oxide catalyst.
  • Curve 1 is propylene selectivity
  • curve 2 is propane conversion
  • curve 3 is carbon oxide selectivity
  • curve 4 is selectivity for methane, ethane and ethylene
  • curve 5-8 corresponds to metal molybdenum vanadium bimetallic catalyst.
  • the curve, curve 5 is propylene selectivity
  • curve 6 is propane conversion
  • curve 7 is carbon oxide selectivity
  • curve 8 is selectivity for methane, ethane and ethylene.
  • the fresh oxygen carrier (catalyst) prepared in the present invention was subjected to H 2 -TPR test, and as shown in Fig. 6, there were mainly two types of oxygen species, OI and OII, in the oxygen carrier, and at a lower temperature.
  • the oxygen OI activity of the lower oxygen release is higher, and it is the main oxygen species that completely oxidizes propane or propylene.
  • the lattice oxygen OII released at a higher temperature has moderate activity and can selectively dehydrogenate propane to Propylene.
  • the increase of Mo content the reduction peak of OI species is gradually weakened, and the reduction peak of OII species gradually increases, which also indicates that the addition of Mo does effectively regulate the activity of lattice oxygen species in the oxygen carrier, and the inhibitory activity. Strong OI species.
  • the XRD experiment was carried out on an X-ray diffractometer of model Rigaku C/mx-2500. As shown in Fig. 7, the fresh catalyst just prepared mainly contains V 2 O 5 , and the characteristics of V 2 O 5 with the addition of Mo content. peak offset angularly, illustrating Mo V 2 O 5 into the lattice phase, V 2 O 5 causes the lattice distortion, the lattice constant changes, providing evidence for the formation of molybdenum-vanadium solid solution.
  • the left side is the catalyst VO x and the right side is the catalyst Mo1V6.
  • the lattice oxygen consumption results and phase changes of the catalysts VO x and Mo1V6 at different reaction times in the chemical chain dehydrogenation process of propane schematic diagram. As the reaction time increases, the lattice oxygen in the oxygen carrier is gradually consumed, and the consumption in the early stage is obvious. The main reason is that the propane and propylene are completely oxidized to CO x , and the lattice oxygen is consumed in a large amount, which urges the lattice oxygen continuously.
  • the preparation of the catalyst of the present invention can be achieved by adjusting the preparation parameters according to the present invention to achieve efficient catalysis against propane.
  • the present invention has been described in detail above, and it should be understood that any simple modifications, alterations, or other equivalents of those skilled in the art without Scope of protection of the invention

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Abstract

一种钼钒双金属氧化物催化剂及其在低碳烷烃化学链脱氢中的应用，钼钒双金属氧化物催化剂分子式为Mo 1V y，y表示钒钼原子摩尔比，采用浸渍法制备，通过浸渍、干燥、焙烧和压片得到Mo 1V y载氧体。利用负载型钼钒双金属氧化物进行低碳烷烃脱氢制烯烃反应，反应温度在450-550℃，可以实现高活性、高选择性的将丙烷氧化脱氢为丙烯，丙烷转化率保持在30-40％，丙烯选择性在80-90％。新鲜的载氧体与丙烷反应后从高价态变为低价态，而低价态载氧体与空气或者氧气反应被氧化为高价态，重新获得晶格氧并再次循环，而且在反复多次再生后反应性能非常稳定，可用于固定床反应器、移动床反应器或者循环流化床等反应装置。

Description

钼钒双金属氧化物催化剂及其在低碳烷烃化学链脱氢中的应用 技术领域
本发明涉及一种利用金属氧化物进行低碳烷烃脱氢的技术，更加具体的说，涉及负载型钼钒双金属氧化物用于低碳烷烃氧化脱氢制烯烃的方法和应用。
背景技术
页岩气作为一种重要的非常规天然气资源，富含低碳烷烃，将页岩气中的低碳烷烃转化成更高价值的化工产品具有重要的能源与环境意义。近年来，利用烷烃脱氢制备相对应的烯烃得到了充分的发展。
以丙烷脱氢制取丙烯为例，传统的无氧脱氢(PDH)技术使用Pt系或者Cr系催化剂，PDH反应在Pt系催化剂催化条件下丙烯选择性很高，但是由于受到的热力学限制导致单程转化率不能有效提高，而且无氧脱氢作为吸热反应在反应阶段能耗很大；Cr系催化剂虽然解决了Pt系催化剂成本较高的问题，但是Cr对环境以及人体毒性较大，热力学限制也没有得到解决，促使人们寻找更经济更高效的丙烷生产丙烯的方式。有氧脱氢(ODH)作为一种潜在的脱氢方式，在反应体系中引入分子氧，突破了热力学限制，在分子氧存在的条件下，丙烷和丙烯容易发生完全氧化反应，生成CO 2，影响反应选择性与经济性，并且，还原性气体与氧气混合存在安全隐患，对反应条件控制要求严苛，因此工业推广难度较大。
化学链技术作为一种先进高效的热化学技术，在燃料转化的同时可以实现产物的近零能耗原位分离，已经得到广泛的关注[Fan L-S，Zeng L，Wang W，Luo S.Chemical looping processes for CO 2 capture and carbonaceous fuel conversion-prospect and opportunity[J].Energy & Environmental Science，2012，5(6)，7254-7280.]。而化学链式氧化脱氢(CL-ODH)是指利用金属氧化物(载氧体)中的晶格氧，高选择性的活化丙烷生成丙烯。既解决了无氧脱氢中热力学限制的影响，又避免了分子氧存在条件下丙烷与丙烯发生深度氧化的倾向。丙烷化学链氧化脱氢(CL-ODH)的装置和过程如附图1所示，在固定床反应器中设置金属氧化物催化剂，在进气管路上设置气体切换装置，气体切换装置分别于原料气路、惰性气体气路和氧化气路相连，并能够进行切换，以使进气管路能够分别与原料气路、惰性气体气路和氧化气路相连。原料气路，用于向固定床反应器 中通入原料低碳烷烃，惰性气体气路，用于向进气管路和固定床反应器中吹扫惰性气氛，以使反应在绝氧条件下进行。氧化气路，用于向固定床反应器中通入氧气或者空气，以使金属氧化物催化剂氧化再生。在进行使用时，首先以惰性气体气路、进气管路、固定床反应器和出气管联通，以排除整个反应系统中的氧，再更换原料气路，以向固定床反应器中通入原料低碳烷烃进行反应，在反应过程中监测金属氧化物催化剂的活性，如产物组成、反应时间、金属氧化物价态等参数，待金属氧化物催化剂活性临近极限时，更换氧化气路通入氧气或者空气，以使金属氧化物催化剂氧化再生，由低价态转变为高价态；再生后，更换惰性气体气路进行除氧，更换原料气路进行反应，更换氧化气路进行再生。采用两台以上固定床反应器组合的反应系统，在任意时刻确保有至少一个固定床反应器处于反应阶段，其余固定床反应器处于再生阶段或者除氧阶段，实现整个反应过程的连续生产。
目前，用于CL-ODH的载氧体主要是单组份金属氧化物，包括氧化钒、氧化铬、氧化钨等。但是这些单一的金属氧化物由于自身晶体结构的影响，使其晶格氧活性收到多种因素的影响，不能高活性、高选择性的活化丙烷碳氢键生成丙烯。所以，如何通过构筑复合金属氧化物，合理可控的调节晶格氧活性，具有重要的科学和经济效益。在前期的研究中，我们申请了一种用于烷烃脱氢的催化剂及用于固定床、移动床和循环流化床反应装置。该发明中的催化剂为非贵金属、无毒无害的，并且可在与该催化剂相配套的反应器中进行连续反应再生。而在维持高催化活性的同时，催化剂的选择性有待进一步的提高。
发明内容
本发明目的在于克服现有技术的不足，热力学限制、丙烯选择性较低、反应经济性较低等缺陷，提供了一种钼钒双金属氧化物催化剂及其在低碳烷烃化学链脱氢中的应用，将钼钒双金属氧化物催化剂作为载氧体，载氧体中的晶格氧与活化的丙烷中氢原子反应生成水，有效推动反应向生成丙烯的方向移动。Mo的添加相对于单一的氧化钒基氧化物，其表面氧活性得到明显抑制，丙烷反应转化率与丙烯选择性都得到了显著的提升，这使丙烯收率和反应经济性得到有效提高。
本发明的技术目的通过下述技术方案予以实现：
钼钒双金属氧化物催化剂为由金属钼的氧化物和金属钒的氧化物组成的固溶体，金 属Mo和金属V的摩尔比为1∶(4～30)，优选1∶(6～18)。
金属Mo进入了V 2O 5的体相晶格，造成了V 2O 5晶格畸变，形成钼钒固溶体。
催化剂为负载型催化剂，载体为Al 2O 3、TiO 2、SiO 2或者分子筛，钼的氧化物质量百分比(即钼的氧化物质量/载体质量)为1～30％，优选10～20％，钒的氧化物质量百分比(即钼的氧化物质量/载体质量)为4～60％，优选40～60％。
在进行制备时，按照下述步骤进行：
步骤1，将偏钒酸铵和草酸均匀分散在去离子水中，按照钼钒原子比再加入钼酸铵混合均匀，形成浸渍液；
步骤2，将载体浸渍于步骤1制备的浸渍液中进行等体积浸渍；
步骤3，经过步骤2浸渍的载体在室温20～25摄氏度下干燥8～12h，再在70～90℃下干燥8～12h，最后在500～600℃下空气气氛下焙烧2～4h，即可得到钼钒双金属氧化物催化剂，其分子式为Mo 1V y，其中，y表示V相对于1molMo的物质的量，即金属V和金属Mo的摩尔比。
在步骤1中，草酸和偏钒酸铵的质量比为(2.8～3)∶(1.5～2)。
在步骤2中，载体为Al 2O 3、TiO 2、SiO 2或者分子筛。
在步骤3中，在室温20～25摄氏度下干燥10～12h，再在80～90℃下干燥10～12h，最后在550～600℃下空气气氛下焙烧2～4h。
在步骤3中，将钼钒双金属氧化物催化剂粉末压片成型制成大小20～40目的颗粒状催化剂。
本发明的催化剂在低碳烷烃化学链脱氢中的应用，反应在无氧条件下进行以催化剂为载氧体，与低碳烷烃发生氧化脱氢反应，载氧体中的晶格氧与低碳烷烃中的氢原子结合生成水，载氧体被还原为低价态，低碳烷烃被氧化为对应的烯烃。
低碳烷烃为至少一个碳原子的烷烃，更优选的包括一个碳原子的直链烷烃，最优选的，所述的烷烃包括优选乙烷、丙烷、正丁烷或异丁烷。
催化剂中的晶格氧参与反应，因此随着反应的进行，晶格氧会逐渐消耗，造成催化剂活性降低，因此，需要进行催化剂的循环再生。低价态载氧体与空气或者氧气反应被氧化为高价态，重新获得晶格氧并再次循环返回反应器进行反应。
在氧化脱氢反应中，气固两相(气相主要为原料低碳烷烃和产物低碳烯烃，固相主要为金属氧化物载氧体)接触方式主要有气固逆流接触和气固并流接触两种操作方式。 具体选择固定床反应器、移动床反应器或者循环流化床。
在进行使用时，将催化剂和石英砂混合均匀进行使用，在常压下进行反应，反应温度为450～500℃，通入氮气以排除氧气和空气，之后通入丙烷，丙烷和氮气总流量为20-50ml/min，丙烷体积百分数为10～30％。催化剂和石英砂的质量比为(0.2～1)∶1，优选(0.5～0.8)∶1。
与现有技术相比，本发明具有如效益：
(1)本发明为负载型双金属氧化物，氧化钒与氧化钼形成双金属复合氧化物。与单一的氧化钒相比，低碳烯烃的选择性出现了明显的提高；与单一氧化钼相比，低碳烷烃的转化率得到了提高。通过调节钼与钒的比例，可以得到转化率与选择性的最优值。
(2)本发明载氧体采用浸渍法制备，操作简单，造价低廉。
(3)载氧体在晶格氧消耗之后还可以保持一个较高的转化率与选择性。
(4)载氧体在经历若干个氧化还原再生循环后基本保持结构和性能的稳定性，转化率和选择性基本不变
(5)催化剂在再生阶段需要通入氧气或空气，一方面可以氧化低价态载氧体补充晶格氧，另一方面载氧体氧化为放热反应，并且伴随着积碳的燃烧，放出的热量可以通过载氧体的导热作用进入反应器为脱氢反应提供热量，通过调节载氧体的质量可以实现热量的完全匹配。
(6)本发明的烷烃脱氢催化剂用于化学链脱氢反应装置中，与现有技术相比，本发明的突出的优势在于烷烃单程转化率高，目的产物烯烃的选择性高，催化剂的活性组分为非贵金属，且对环境无不利影响，且无硫化介质的引入。
附图说明
图1是本发明中使用的丙烷化学链脱氢的装置和过程示意图。
图2是在丙烷化学链脱氢过程中使用不同Mo添加量的催化剂的活性测试结果图。
图3是在丙烷化学链脱氢过程中不同温度下活性测试结果图。
图4是在丙烷化学链脱氢过程中不同空速下活性测试结果图。
图5是在丙烷化学链脱氢过程中分别使用VO x和Mo1V6催化剂时，不同反应时间下活性测试结果图。
图6是本发明制备的新鲜载氧体(催化剂)的H 2-TPR测试结果谱图。
图7是本发明制备的新鲜载氧体(催化剂)的XRD测试结果谱图。
图8是在丙烷化学链脱氢过程中使用催化剂Mo1V6进行反应再生循环的循环稳定性测试结果图。
图9是在丙烷化学链脱氢过程中使用催化剂Mo1V6进行反应再生循环前后的载氧体测试结果图。
图10是在丙烷化学链脱氢过程中不同反应时间下催化剂VO x和Mo1V6的晶格氧消耗结果图。
图11是在丙烷化学链脱氢过程中不同反应时间下催化剂VO x和Mo1V6的物相变化示意图。
具体实施方式
下面结合具体实施例进一步说明本发明的技术方案。
首先进行钼钒双金属氧化物催化剂的制备，每一质量份为1g，同时制备金属V和金属Mo的单金属氧化物催化剂，作为对比验证使用，在进行制备时选择相同的制备工艺参数进行三种金属氧化物催化剂的制备。
实施例1
步骤1，取1.8质量份的偏钒酸铵(NH 4VO 3)与2.9质量份的草酸(C 2H 2O 4)溶于3mL去离子水中，待反应完全之后，按照钼钒原子比加入一定质量的钼酸铵((MH 4) 6Mo 7O 24.4H 2O)，将2.0质量份的Al 2O 3浸渍于上述溶液中。
步骤2，将步骤1所得物质在室温25摄氏度下干燥12h，再在70℃下干燥12h，最后在600℃下空气气氛下焙烧4h，得到负载于氧化铝上的钼钒双金属复合氧化物，其分子式为Mo 1V y。其中，y表示V相对于1molMo的物质的量，y＝4，6，9，12，18，30，即金属V和金属Mo的摩尔比。
步骤3，将Mo 1V y固体粉末压片成型制成大小20～40目的颗粒状催化剂。
实施例2
采用实施例1方法进行反应，其区别仅在于步骤(1)的钼酸铵的质量为0，得到VO x催化剂。
实施例3
步骤1，取1.472质量份的钼酸铵((MH 4) 6Mo 7O 24.4H 2O)，溶于3mL去离子水 中，将2.0质量份Al 2O 3浸渍于上述溶液中，室温干燥12h，80℃干燥2h；
步骤2，将步骤1所得物质在室温25摄氏度下干燥12h，再在70℃下干燥12h，最后在600℃下空气气氛下焙烧4h，得到负载于氧化铝上的氧化钼，其分子式为MoO x。
步骤3，将MoO x固体粉末压片成型制成大小20～40目的颗粒状催化剂。
实施例4
实施例1～3中所得的VO x、Mo 1V y、MoO x载氧体(即三种氧化物催化剂)，分别称取0.25～0.8g与石英砂(SiC)2mL混合，加入固定床管式反应器，实验在450～500℃常压条件下进行。通入N 2，以排除氧气和空气，之后通入丙烷，其中丙烷和氮气总流量为21ml/min，丙烷体积分数为20％。产品组成由气相色谱检测。
丙烷转化率由如下公式计算：
Figure PCTCN2018096942-appb-000001
其中：
Figure PCTCN2018096942-appb-000002
——丙烷转化率，％
Figure PCTCN2018096942-appb-000003
——反应器进口丙烷摩尔流量，mol/min
Figure PCTCN2018096942-appb-000004
——反应器出口丙烷摩尔流量，mol/min
产品气相选择性由如下公式计算：
Figure PCTCN2018096942-appb-000005
其中：S 产物A——气相产物A的选择性，％
n 产物A——气相产物A的产量，mol
∑n 产物——气相所有产物物质的量之和，mol
x 产物A——气相产物A在所有气相产物中的含量
气相产物A包括：C 3H 6，CO x(碳氧化物，即一氧化碳，二氧化碳)，CH 4，C 2H 6，C 2H 4。
以上实施例的催化剂反应活性均为反应时间为5min时的活性，如图2所示，柱状图为产物转化率或者选择性，星形对应丙烯产率。随着钼含量的增加，丙烷的转化率随之升高，丙烯的选择性有所上升，均保持在80％以上，最高的为Mo1V6下的丙烯选择 性为89％；纯的氧化钒VO x，表面氧活性较高，导致丙烷或丙烯被完全氧化为CO x；纯的氧化钼MoO x，表面氧化性较低，使得丙烷转化率较低，丙烷或丙烯被完全氧化为CO x较低(VO x、Mo 1V y、MoO x、同时使用VO x和MoO x)。而钼钒双金属氧化物可以在抑制表面氧活性的同时，有效提高丙烯的选择性。而过多的钼的添加，会导致丙烷的转化率和丙烯的选择性有所降低。所以最佳Mo添加量的钼钒双金属氧化物为Mo1V6。(各个图中柱状图代表的产物，与附图2一致)。
以最佳Mo添加量的钼钒双金属氧化物为Mo1V6为参考，图3中Mo1V6随反应温度性能测试结果可以看出，随着反应温度的提高，丙烷的转化率有所提高，CO x的选择性逐渐减低，但随着反应温度的进一步升高，丙烷C-C断裂生成甲烷的倾向增大，导致丙烯的选择性有所降低。图4中VO x和Mo1V6丙烷化学链脱氢过程不同空速下活性测试结果图表明，I、II和III分别对应载氧体0.25g、0.5g和0.8g(空速为气体流量/催化剂质量，在气体流量保持不变的情况下通过改变催化剂质量来实现空速调整)，随着反应空速的降低，丙烷的转化率有所增加，但是丙烯的选择性有所降低，主要是因为停留时间的减少会造成丙烷或丙烯被表面较强活性的氧化物完全氧化生成CO x。
图5是在丙烷化学链脱氢过程中分别使用VO x和Mo1V6催化剂时，不同反应时间下活性测试结果图，柱状图对应为丙烯收率，曲线1-4对应使用金属V氧化物催化剂的曲线，曲线1为丙烯选择性，曲线2为丙烷转化率，曲线3为碳氧化物选择性，曲线4为甲烷、乙烷和乙烯等的选择性，曲线5-8对应使用金属钼钒双金属催化剂的曲线，曲线5为丙烯选择性，曲线6为丙烷转化率，曲线7为碳氧化物选择性，曲线8为甲烷、乙烷和乙烯等的选择性。随着反应时间的增加，载氧体中的晶格氧逐渐被消耗，从图5中VO x和Mo1V6丙烷化学链脱氢过程不同反应时间下活性测试结果图中可以看出，反应初始阶段0～3min晶格氧活性最高，丙烷转化率最高，但是较高的氧活性造成了完全氧化生成CO x。随着表面晶格氧的逐渐消耗殆尽，在3～5min时，此时有着最高的C 3H 6产率，说明了此时体相晶格氧是活化丙烷生成丙烯的主要活性氧物种。在反应的末期10～15min，晶格氧消耗殆尽，此时发生的主要是丙烷在V 2O 3上的无氧脱氢反应。
将本发明中制备的新鲜载氧体(催化剂)进行H 2-TPR测试，结果如附图6所示，氧载体中主要存在着两种类型的氧物种，OI和OII，而在较低温度下释氧放的晶格氧OI活性较高，是完全氧化丙烷或丙烯的主要氧物种，而在较高温度下释放的晶格氧OII，活性适中，可以选择性的将丙烷养活脱氢为丙烯。并且，醉着Mo含量的增加，OI物种 的还原峰逐渐被削弱，而OII物种的还原峰逐渐增加，也说明了Mo的添加的确有效调控了载氧体中晶格氧物种的活性，抑制活性较强的OI物种。XRD实验在型号Rigaku C/mx-2500的X射线衍射仪上进行，如附图7所示，刚刚制备的新鲜催化剂主要含V 2O 5，随着Mo含量的添加，V 2O 5的特征峰出现了一定角度的偏移，说明了Mo进入了V 2O 5的体相晶格，造成了V 2O 5晶格畸变，晶格常数发生了变化，为钼钒固溶体的形成提供证据。
在完成反应后，晶格氧逐渐消耗，造成催化剂活性降低，使用氧气或者空气对催化剂进行再生(即被氧化为高价态)，重新获得晶格氧并循环返回反应器中进行反应，丙烷化学链脱氢过程循环稳定性测试附图8(每个产物对应附图中标记)结果表明，氧化还原循环过程中性能基本保持不变，说明钼钒双金属氧化物具有很好的氧化再生性能。50个循环之后(“反应-再生-反应-再生”的循环)氧载体和新鲜氧载体的XRD和H 2-TPR，如附图9所示，左侧为XRD，曲线1和2分别为新鲜载体和循环后氧载体的XRD谱线谱图，曲线右侧为H 2-TPR，曲线3和4分别为新鲜载体和循环后氧载体的H 2-TPR谱线谱图，对比可以看出，载氧体的物相结构基本没有发生变化，也很好的解释了钼钒固溶体优异的稳定性能。
如附图10和11所示，左侧为催化剂VO x，右侧为催化剂Mo1V6，在丙烷化学链脱氢过程中不同反应时间下催化剂VO x和Mo1V6的晶格氧消耗结果图和物相变化示意图。随着反应时间的增加，载氧体中的晶格氧逐渐被消耗，前期阶段消耗明显，主要是由于丙烷和丙烯完全氧化为CO x，晶格氧被大量消耗，而催着晶格氧不断消耗，氧活性不断减弱，晶格氧选择性的将丙烷氧化脱氢为丙烯，晶格氧消耗缓慢，后期晶格氧消耗殆尽，反应进入无氧脱氢阶段。从左图VO x和Mo1V6晶格氧消耗对比可以看出，Mo的添加有效减少了副反应CO x生成所消耗的大量的晶格氧，而增加了选择性转化为丙烯消耗的晶格氧。随着反应时间的进行，VO X和Mo1V6经历着物相结构的变化，从V 2O 5-V 2O 4-V 2O 3，从反应时间看主要对应着完全氧化阶段，选择性氧化脱氢阶段和无氧脱氢阶段。
根据本发明内容进行制备参数的调整，均可实现本发明催化剂的制备，实现针对丙烷的有效催化。以上对本发明做了示例性的描述，应该说明的是，在不脱离本发明的核心的情况下，任何简单的变形、修改或者其他本领域技术人员能够不花费创造性劳动的等同替换均落入本发明的保护范围

Claims (15)

  1. 钼钒双金属氧化物催化剂，其特征在于，由金属钼的氧化物和金属钒的氧化物组成的固溶体，金属Mo和金属V的摩尔比为1∶(4～30)，金属Mo进入了V 2O 5的体相晶格，造成了V 2O 5晶格畸变，形成钼钒固溶体。
  2. 根据权利要求1所述的钼钒双金属氧化物催化剂，其特征在于，金属Mo和金属V的摩尔比为1∶(6～18)。
  3. 根据权利要求1或者2所述的钼钒双金属氧化物催化剂，其特征在于，催化剂为负载型催化剂，载体为Al 2O 3、TiO 2、SiO 2或者分子筛，钼的氧化物质量百分比为1～30％，钒的氧化物质量百分比为4～60％。
  4. 根据权利要求3所述的钼钒双金属氧化物催化剂，其特征在于，钼的氧化物质量百分比为10～20％，钒的氧化物质量百分比为40～60％。
  5. 钼钒双金属氧化物催化剂的制备方法，其特征在于，按照下述步骤进行：
    步骤1，将偏钒酸铵和草酸均匀分散在去离子水中，按照钼钒原子比再加入钼酸铵混合均匀，形成浸渍液；
    步骤2，将载体浸渍于步骤1制备的浸渍液中进行等体积浸渍；
    步骤3，经过步骤2浸渍的载体在室温20～25摄氏度下干燥8～12h，再在70～90℃下干燥8～12h，最后在500～600℃下空气气氛下焙烧2～4h，即可得到钼钒双金属氧化物催化剂，其分子式为Mo 1V y，其中，y表示V相对于1molMo的物质的量，即金属V和金属Mo的摩尔比。
  6. 根据权利要求5所述的钼钒双金属氧化物催化剂的制备方法，其特征在于，在步骤1中，草酸和偏钒酸铵的质量比为(2.8～3)∶(1.5～2)。
  7. 根据权利要求5所述的钼钒双金属氧化物催化剂的制备方法，其特征在于，在步骤2中，载体为Al 2O 3、TiO 2、SiO 2或者分子筛。
  8. 根据权利要求5所述的钼钒双金属氧化物催化剂的制备方法，其特征在于，在步骤3中，在室温20～25摄氏度下干燥10～12h，再在80～90℃下干燥10～12h，最后在550～600℃下空气气氛下焙烧2～4h。
  9. 如权利要求1～4之一所述的钼钒双金属氧化物催化剂在低碳烷烃化学链脱氢中的应用。
  10. 根据权利要求9所述的钼钒双金属氧化物催化剂在低碳烷烃化学链脱氢中的应用，其特征在于，反应在无氧条件下进行以催化剂为载氧体，与低碳烷烃发生氧化脱氢反应，载氧体中的晶格氧与低碳烷烃中的氢原子结合生成水，载氧体被还原为低价态，低碳烷烃被氧化为对应的烯烃。
  11. 根据权利要求9或者10所述的钼钒双金属氧化物催化剂在低碳烷烃化学链脱氢中的应用，其特征在于，低碳烷烃为乙烷、丙烷、正丁烷或异丁烷
  12. 根据权利要求9或者10所述的钼钒双金属氧化物催化剂在低碳烷烃化学链脱氢中的应用，其特征在于，在氧化脱氢反应中，气固两相接触方式有气固逆流接触和气固并流接触两种操作方式，具体选择固定床反应器、移动床反应器或者循环流化床。
  13. 根据权利要求10所述的钼钒双金属氧化物催化剂在低碳烷烃化学链脱氢中的应用，其特征在于，催化剂的晶格氧参与反应，随着反应的进行，晶格氧会逐渐消耗，造成催化剂活性降低，进行催化剂的循环再生，低价态载氧体与空气或者氧气反应被氧化为高价态，重新获得晶格氧并再次循环返回反应器进行反应。
  14. 根据权利要求9或者10所述的钼钒双金属氧化物催化剂在低碳烷烃化学链脱氢中的应用，其特征在于，在进行使用时，将催化剂和石英砂混合均匀进行使用，在常压下进行反应，反应温度为450～500℃，通入氮气以排除氧气和空气，之后通入丙烷，丙烷和氮气总流量为20～50ml/min，丙烷体积百分数为10～30％，催化剂和石英砂的质量比为(0.2～1)∶1。
  15. 根据权利要求14所述的钼钒双金属氧化物催化剂在低碳烷烃化学链脱氢中的应用，其特征在于，在进行使用时，催化剂和石英砂的质量比为(0.5～0.8)∶1。
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