WO2020014850A1 - 一种高比表面积纯M1相MoVTeNbOx催化剂的制备方法 - Google Patents

一种高比表面积纯M1相MoVTeNbOx催化剂的制备方法 Download PDF

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WO2020014850A1
WO2020014850A1 PCT/CN2018/095872 CN2018095872W WO2020014850A1 WO 2020014850 A1 WO2020014850 A1 WO 2020014850A1 CN 2018095872 W CN2018095872 W CN 2018095872W WO 2020014850 A1 WO2020014850 A1 WO 2020014850A1
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containing compound
catalyst
solution
precursor
protective agent
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French (fr)
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黄伟新
章轩语
卫泽跃
尤瑞
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中国科学技术大学
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    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/10—Heat treatment in the presence of water, e.g. steam
    • 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
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
    • B01J27/057—Selenium or tellurium; Compounds thereof
    • B01J27/0576—Tellurium; Compounds 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
    • 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
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/04—Mixing
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C11/00—Aliphatic unsaturated hydrocarbons
    • C07C11/02—Alkenes
    • C07C11/04—Ethylene
    • 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
    • B01J2523/00—Constitutive chemical elements of heterogeneous 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
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Definitions

  • the invention relates to the field of catalysis, in particular to a method for preparing a pure M1-phase MoVTeNbOx catalyst with high specific surface area.
  • Ethylene (C 2 H 4 ) is one of the world's largest output chemical products. It is an important chemical raw material. It is mainly used for synthetic fibers, rubber, plastics, acrylic, adhesives and other chemicals. At present, ethylene products account for more than 40% of organic chemicals, and about 75% of petrochemical products are produced by ethylene, which plays an important role in the national economy. The world has taken ethylene production scale, technology and output as one of the important indicators to measure a country's petrochemical development level.
  • ethylene production is mainly achieved by steam cracking and catalytic cracking of naphtha and ethane.
  • This type of cracking process is a strongly endothermic reaction.
  • the reaction temperature is generally greater than 900 ° C.
  • the energy consumption is high and it is limited by thermodynamic equilibrium, and the combustion of by-products is accompanied by a large amount of CO 2 and other greenhouse gas emissions.
  • ODHE ethane oxidative dehydrogenation
  • ethylene production technology using ethane (C 2 H 6 ) and oxygen (O 2 ) as raw materials has many advantages and is a low energy consumption method for ethylene production. Great application prospects.
  • pure M1 phase catalyst is currently a catalyst system with great application prospects, which can achieve higher ethane conversion and ethylene selectivity at lower temperatures, but the current patent Compared with MoVTeNbOx pure M1 phase catalysts reported in the literature, the space-time yield and catalyst production capacity are still far from the requirements of industrialization.
  • pure M1 phase catalysts are generally prepared by a hydrothermal method or a precipitation method with a suitable purification process. The specific surface area of the prepared catalysts is generally small, which limits its catalytic activity.
  • the technical problem to be solved by the present invention is to provide a method for preparing a pure M1-phase MoVTeNbOx catalyst with a high specific surface area, and the prepared catalyst has a higher specific surface area.
  • the invention provides a method for preparing a pure M1-phase MoVTeNbOx catalyst with a high specific surface area, including the following steps:
  • the protective agent is a surfactant or a small molecule organic acid and a salt thereof;
  • the protective agent is a non-ionic polymer surfactant, a cationic surfactant, or an organic acid of C1 to C20 and a salt thereof.
  • the protective agent is a quaternary ammonium salt surfactant, a polyether surfactant, a polyamide surfactant, a C1-C20 reducing organic acid and a salt thereof, or a C1-C20 non-reducing organic acid. Acids and their salts.
  • the protective agent is citric acid, sodium citrate, ammonium citrate, oleic acid, ascorbic acid, oxalic acid, sodium malonate, sodium oxalate, polyvinylpyrrolidone, cetyltrimethylammonium bromide, poly Vinyl alcohol or polyethylene glycol.
  • the step S1) is specifically:
  • the precursor solution and the protecting agent solution are mixed to obtain a precursor-protecting agent mixed solution.
  • the molar ratio of Mo, V, Te, Nb and the protective agent is 1: (0.15 to 0.35): (0.15 to 0.35): (0.10 to 0.15): (0.069 ⁇ 1.38).
  • the temperature of the hydrothermal reaction is 150-200 ° C, and the time of the hydrothermal reaction is 24-48 hours.
  • the baking temperature in the air atmosphere is 200 to 300 ° C and the time is 1 to 4 hours; the baking temperature in the inert gas is 500 to 600 ° C and the time is 1 to 4 hours; the hydrogen peroxide The concentration is 5% to 20%; the temperature of the purification treatment is 20 to 80 ° C, and the time is 1 to 3h.
  • the invention provides a new method for preparing a pure M1 phase MoVTeNbOx catalyst.
  • the size of the phase in the catalyst is regulated by a hydrothermal synthesis method using a protective agent, and then purified by hydrogen peroxide to remove the M2 phase.
  • the pure M1-phase MoVTeNbOx catalyst with high specific surface area and pore volume has excellent catalytic activity, has obtained a high space-time yield (STY), is greater than 1 kg C2H4 / kg cat / h, and has good stability.
  • STY space-time yield
  • the preparation process is simple, the operation is simple, the repeatability is good, the protective agent used in the synthesis is inexpensive, and has a good application prospect.
  • FIG. 1 is an X-ray diffraction pattern of the catalyst in Example 1 after calcination and purification
  • Example 2 is a comparison diagram of the catalytic effect of the catalyst synthesized by adding a sodium citrate protective agent in Example 1 and the catalyst synthesized without adding a protective agent in Comparative Example 1;
  • Example 4 is an oxidative dehydrogenation activity diagram of a catalyst synthesized by adding a sodium citrate protective agent in Example 1 at a reaction flow rate of 50 ml / min;
  • Example 5 is an X-ray diffraction pattern of the catalyst after purification and calcination in Example 2;
  • FIG. 6 is a comparison diagram of the catalytic effects of the catalyst synthesized by adding the ammonium citrate protective agent in Example 2 and the catalyst synthesized without the protective agent in Comparative Example 1;
  • FIG. 6 is a comparison diagram of the catalytic effects of the catalyst synthesized by adding the ammonium citrate protective agent in Example 2 and the catalyst synthesized without the protective agent in Comparative Example 1;
  • FIG. 7 is an ethane oxidative dehydrogenation activity life curve of a catalyst synthesized by adding an ammonium citrate protective agent in Example 2;
  • Example 8 is an X-ray diffraction pattern of the catalyst after calcination and purification in Example 3;
  • FIG. 9 is a comparison diagram of the catalytic effects of the catalyst synthesized by adding a citric acid protective agent in Example 3 and the catalyst synthesized without adding a protective agent in Comparative Example 1;
  • FIG. 9 is a comparison diagram of the catalytic effects of the catalyst synthesized by adding a citric acid protective agent in Example 3 and the catalyst synthesized without adding a protective agent in Comparative Example 1;
  • the invention provides a method for preparing a pure M1-phase MoVTeNbOx catalyst with a high specific surface area, including the following steps:
  • the protective agent is a surfactant or a small molecule organic acid and a salt thereof;
  • the invention uses a molybdenum-containing compound, a vanadium-containing compound, a tellurium-containing compound, and a niobium-containing compound as raw materials to prepare a pure M1 phase MoVTeNbOx catalyst.
  • the vanadium-containing compound is a vanadium metal salt, such as one or more of vanadium sulfate and ammonium metavanadate.
  • the tellurium-containing compound is telluric acid.
  • the niobium-containing compound is a niobium metal salt, such as one or more of ammonium niobium oxalate and niobium oxalate.
  • the protective agent is a surfactant or a small molecule organic acid and a salt thereof.
  • the small-molecule organic acid and its salt are preferably C1-C20 organic acid and its salt; more preferably, C1-C20 reducing organic acid and its salt; still more preferably lemon Acid, sodium citrate, ammonium citrate, oleic acid, ascorbic acid or oxalic acid.
  • the C1-C20 organic acid and its salt are preferably C1-C20 non-reducing organic acid and its salt, and more preferably sodium malonate or sodium oxalate.
  • the dissolving condition is heating.
  • the heating temperature is preferably 40 to 80 ° C, and more preferably 80 ° C.
  • the heating rate is preferably 1 to 5 ° C / min, and more preferably 5 ° C / min.
  • the invention does not specifically limit the mixing order of the molybdenum-containing compound, vanadium-containing compound, tellurium-containing compound, niobium-containing compound, and protective agent, and they can be added simultaneously and mixed or added in batches.
  • a molybdenum-containing compound, a vanadium-containing compound, a tellurium-containing compound, and a niobium-containing compound are first mixed and dissolved under heating conditions, and then mixed with the protecting agent solution to obtain a precursor-protecting agent mixed solution.
  • the precursor solution and the protecting agent solution are mixed to obtain a precursor-protecting agent mixed solution.
  • the concentration of the protecting agent solution is 0.025 to 0.5 mol / L; the volume ratio of the protecting agent solution to the precursor solution is 1: (2 to 10).
  • the molar ratio of Mo, V, Te, Nb and the protective agent is preferably 1: (0.15 to 0.35): (0.15 to 0.35 ): (0.10 to 0.15): (0.069 to 1.38).
  • the method for separating and obtaining the solid is not particularly limited in the present invention, and can be a separation method well known to those skilled in the art, such as centrifugation or filtration.
  • the present invention does not specifically limit the hydrothermal reaction.
  • the hydrothermal reaction is performed in a hydrothermal kettle.
  • the temperature of the hydrothermal reaction is 150-200 ° C; and the time of the hydrothermal reaction is 24-48h.
  • the solid was then fired in an air atmosphere.
  • the roasting is performed in a muffle furnace.
  • the baking temperature is 200 to 300 ° C.
  • the time is 1 to 4 hours.
  • the method before firing in an air atmosphere, the method further includes:
  • the obtained solid was washed, dried, and ground to obtain a solid powder precursor.
  • the drying temperature is preferably 60 to 100 ° C, and the drying time is preferably 8 to 20 hours.
  • the solid is then calcined in an inert gas.
  • the inert gas is one or more of argon, helium, and nitrogen.
  • the temperature for firing in an inert gas is 500 to 600 ° C, and the time is 1 to 4 hours.
  • the baking in an inert gas is performed in a tube furnace.
  • the obtained solid was further purified by hydrogen oxide to obtain a pure M1 phase MoVTeNbOx catalyst.
  • the hydrogen peroxide concentration is preferably 5% to 20%; the temperature of the purification treatment is 20 to 80 ° C, and the time is 1 to 3 hours.
  • the obtained solid is stirred and treated in a hydrogen peroxide solution at 20 to 80 ° C for 1 to 3 hours, the M2 phase is removed, and the solid is dried after being washed with deionized water.
  • the pure M1 phase MoVTeNbOx catalyst prepared by the above method can be applied to the oxidative dehydrogenation of ethane to ethylene, or other suitable reactions known to those skilled in the art.
  • the present invention adds a protective agent to reduce the size of the M2 phase.
  • the MoVTeNbOx composite oxide catalyst synthesized by this method can effectively control the size of different phases, and removes M2 by hydrogen oxide purification treatment.
  • a pure M1 phase MoVTeNbOx catalyst was obtained, which has rich pore volume and high specific surface area, and showed excellent conversion, selectivity, space-time yield, and stability in the oxidative dehydrogenation of ethane to ethylene.
  • the method provided by the present invention is simple and convenient, and the cost of the protective agent used is low, which is suitable for commercial application.
  • reagents used in the following examples of the present invention such as gas (ethane, oxygen, nitrogen, argon, etc.) and reagents such as ammonium molybdate, vanadium sulfate, ammonium niobium oxalate, telluric acid, citric acid, sodium citrate, etc. are available from the market Purchased.
  • Solution 1 After cooling with solution 2, mix and stir well to obtain a precursor solution, then add 0.05mol / L sodium citrate solution, the volume ratio of the protective agent solution to the precursor solution is 1: 6.5, continue to mix and stir well; mix well
  • the solution was transferred to a hydrothermal kettle and hydrothermally heated at 175 ° C for 48 hours to obtain a purple suspension; the suspension obtained by hydrothermal synthesis was washed by centrifugation, dried at 80 ° C in a blast drying oven overnight, and ground.
  • a solid powder precursor was obtained later; the precursor solid powder was placed in a muffle furnace and baked at 250 ° C in an air atmosphere for 2 hours, and then the powder was placed in a tube furnace and fired at 600 ° C for 2 hours in an argon atmosphere, and then obtained MoVTeNbOx catalyst with mixed phase of M1 and M2
  • the surface area (BET) was 0.8 m 2 / g, and the pore volume (Pore Volume) was 0.0013 cm 3 / g.
  • the mixed-phase catalyst was placed in a 7.5% hydrogen peroxide solution by volume fraction, heated to 60 ° C., and stirred for 3 h. After centrifugal washing with deionized water, it was dried overnight in a blast drying oven at 110 ° C. to obtain a pure M1 phase MoVTeNbOx catalyst.
  • the specific surface area (BET) was 48.9 m 2 / g, and the pore volume was 0.10 cm. 3 / g.
  • reaction atmosphere is a mixture of ethane, oxygen, and argon (gas ratio of 3: 2: 5), and the total gas flow rate is 30ml.
  • reaction atmosphere was a mixture of ethane, oxygen, and argon (gas ratio of 3: 2: 5).
  • the total gas flow rate is 50ml / min, and the gas composition after the reaction is detected by online gas chromatography (Shimadzu GC-2014 gas chromatograph, SH-Rt-Alumina BOND / KCl column connected to FID detector, Porapak Q column connected to TCD detector , High-purity argon as a carrier gas), its specific catalytic activity is shown in Figure 4, when the reaction temperature is 425 ° C, the ethane conversion is 71.4%, the ethylene selectivity is 83.4%, and its ethylene space-time yield (STY) performance It reaches 3.05kg C 2 H 4 / kgcat / h.
  • STY ethylene space-time yield
  • the volume ratio of the protective agent solution to the precursor solution is 1: 8.5. After mixing and stirring, transfer to a hydrothermal kettle, and heat at 175 ° C for 48h. After that, a lavender suspension was obtained; after centrifuging the suspension, it was dried overnight in a blast drying box at 80 ° C, and then calcined at 300 ° C in an air atmosphere for 2h, and then at 600 ° C in an argon atmosphere for 2h. Then, a MoVTeNbOx catalyst with a mixed phase of M1 and M2 is obtained. At this time, the specific surface area (BET) of the catalyst is 1.2m 2 / g and the pore volume is 0.0078cm 3 / g.
  • BET specific surface area
  • the mixed phase catalyst is then placed in a volume.
  • a 7.5% hydrogen peroxide solution heat to 60 ° C, stir for 3 hours, centrifuge and wash with deionized water, and dry in a blast drying oven at 110 ° C overnight to obtain a pure M1 phase MoVTeNbOx catalyst.
  • Its specific surface area (BET ) Is 43.0 m 2 / g, and the pore volume (Pore Volume) is 0.12 cm 3 / g.
  • the XRD test was performed on the prepared catalyst. The results are shown in FIG. 5. It can be seen from FIG. 5 that the results are similar to those in Example 1. It shows that the catalyst synthesized by the ammonium citrate protective agent has reduced the size of the M2 phase and treated with hydrogen peroxide. After dissolving the small-sized M2 phase, the pore volume of the M2 phase is significantly increased, thereby increasing the specific surface area of the catalyst.
  • molar ratio of Mo, V, Te, Nb and the protective agent (citric acid) is 1: 0.25: 0.23: 0.12: 0.28, under a heating condition of 80 ° C, a certain amount of ammonium niobium oxalate is weighed and dissolved in deionization.
  • Solution 1 was obtained in water, and a certain mass of ammonium molybdate, vanadium sulfate, and telluric acid was also weighed and dissolved in deionized water to obtain solution 2.
  • the volume ratio of solution 1 to solution 2 was 1: 2.5. After the solution 2 was cooled, mixed and stirred to obtain a precursor solution. Add 0.1mol / L citric acid protection agent solution to the precursor solution.
  • the volume ratio of the protection agent solution to the precursor solution is 1: 7.5.
  • To obtain a lavender suspension after centrifuging the suspension, drying it at 80 ° C. in a blast drying oven overnight, followed by calcination at 250 ° C. for 2 h in an air atmosphere, and then calcination at 600 ° C. for 2 h under an argon atmosphere, Then a MoVTeNbOx catalyst with a mixed phase of M1 and M2 was obtained.
  • the specific surface area (BET) of the catalyst was 1.7 m 2 / g and the pore volume was 0.0047 cm 3 / g.
  • the mixed phase catalyst was then placed in a volume fraction. It is a 15% hydrogen peroxide solution, heated to 60 ° C, stirred for 3 hours, centrifuged and washed with deionized water, and dried in a blast drying oven at 110 ° C overnight to obtain a pure M1 phase MoVTeNbOx catalyst. Its specific surface area (BET) It was 37.8 m 2 / g, and the pore volume was 0.069 cm 3 / g.
  • the XRD test was performed on the prepared catalyst. The results are shown in Fig. 8. It can be seen from Fig. 8 that the catalysts calcined in argon at 600 ° C have diffraction peaks of M1 and M2 phases at the same time. Pure M1 phase is obtained after hydrogen peroxide treatment. MoVTeNbOx catalyst.
  • the specific surface area (BET) of the catalyst was 1.7 m 2 / g and the pore volume was 0.0048 cm 3 / g.
  • the mixed phase catalyst was then placed in a volume fraction of In a 7.5% hydrogen peroxide solution, heated to 60 ° C, stirred for 3 hours, centrifuged and washed with deionized water, and dried in a blast drying oven at 110 ° C overnight to obtain a pure M1 phase MoVTeNbOx catalyst.
  • Its specific surface area (BET) is 45.2 m 2 / g, and the pore volume (Pore Volume) was 0.14 cm 3 / g.
  • PVP polyvinylpyrrolidone
  • the specific surface area (BET) of the catalyst was 5.3 m 2 / g, and the pore volume (Pore Volume) was 0.011 cm 3 / g.
  • the mixed-phase catalyst was then placed in a 7.5% hydrogen peroxide solution. Medium, heated to 60 ° C, stirred for 3 hours, washed with deionized water, centrifuged, and dried in a blast drying oven at 110 ° C overnight to obtain a pure M1-phase MoVTeNbOx catalyst, whose specific surface area (BET) is 72.1m 2 / g, The pore volume was 0.25 cm 3 / g.
  • the molar ratio of Mo, V, Te, Nb and the protective agent is 1: 0.25: 0.23: 0.12: 0.069, under a heating condition at 80 ° C, a certain amount is weighed in proportion.
  • the ammonium niobium oxalate was dissolved in deionized water to obtain solution 1.
  • a certain mass of ammonium molybdate, vanadium sulfate, and telluric acid was weighed and dissolved in deionized water to obtain solution 2.
  • the volume ratio of solution 1 to solution 2 was 1: 2.5. After cooling solution 1 and solution 2, mix and stir to obtain a precursor solution.
  • CTAB cetyltrimethylammonium bromide
  • the specific surface area (BET) of the catalyst was 2.9 m 2 / g, and the pore volume was 0.0083 cm 3 / g.
  • the mixed-phase catalyst was then placed in a volume fraction. In a 7.5% hydrogen peroxide solution, heated to 60 ° C, stirred for 3 hours, centrifuged and washed with deionized water, and dried in a blast drying oven at 110 ° C overnight to obtain a pure M1 phase MoVTeNbOx catalyst, its specific surface area (BET) It was 34.8 m 2 / g, and the pore volume (Pore Volume) was 0.05 cm 3 / g.
  • the reaction atmosphere is a mixture of ethane, oxygen, and argon (gas ratio is 3: 2: 5), and the total gas flow rate is 30ml / min; the ethane conversion was 16.4% at a reaction temperature of 375 ° C, the ethylene selectivity was 93.1%, and the space-time yield (STY) of ethylene was 0.48kg C2H4 / kg cat / h; at a reaction temperature of 425 ° C, the ethane conversion The rate was 41.1%, the ethylene selectivity was 84.8%, and the space-time yield (STY) of ethylene was 1.09 kg C2H4 / kg cat / h.
  • the pure M1 phase MoVTeNbOx catalyst prepared by the present invention has higher specific surface area, catalytic activity and stability.

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Abstract

本发明提供了一种高比表面积纯M1相MoVTeNbOx催化剂的制备方法，包括以下步骤：S1)将含钼化合物、含钒化合物、含碲化合物、含铌化合物和保护剂混合溶解，得到前驱体-保护剂混合溶液；所述保护剂为表面活性剂或小分子有机酸及其盐；S2)将所述前驱体-保护剂混合溶液进行水热反应，分离得到固体；S3)将所述固体在空气氛围中焙烧，然后在惰性气体中焙烧，再经过氧化氢纯化处理，得到纯M1相MoVTeNbOx催化剂。通过该方法合成的MoVTeNbOx复合氧化物催化剂具有丰富孔体积和高比表面积，在乙烷氧化脱氢制乙烯反应中表现出优异的转化率、选择性、时空产率以及稳定性。

Description

一种高比表面积纯M1相MoVTeNbOx催化剂的制备方法 技术领域
本发明涉及催化领域，尤其涉及一种高比表面积纯M1相MoVTeNbOx催化剂的制备方法。
背景技术
乙烯(C 2H 4)是世界上产量最大的化学产品之一，是一种重要的化工基础原料，主要用于合成纤维、橡胶、塑料、腈纶、粘合剂等化学品。目前乙烯产品占有机化学品的40％以上，而石油化工产品中约有75％都是乙烯生产的，其在国民经济中占有重要的地位。世界上已将乙烯生产规模、技术与产量作为衡量一个国家石油化工发展水平的重要标志之一。
目前，乙烯的生产主要通过石脑油和乙烷的蒸汽裂解和催化裂解实现。这类裂解过程是一个强吸热反应，反应温度一般大于900℃，能耗高且受热力学平衡的限制，并且副产物的燃烧也伴随着大量CO 2等温室气体的排放。相比较而言，以乙烷(C 2H 6)和氧气(O 2)为原料的乙烷氧化脱氢(ODHE)制乙烯技术具有较多的优势，是一条低能耗制乙烯的途径，具有巨大的应用前景。但是由于催化剂性能及制备工艺的限制，乙烷氧化脱氢(ODHE)制乙烯方法目前还没有工业化。F.Cavani,等人在文献(Oxidative Dehydrogenation of Ethane and Propane:How Far from Commercial Implementation？Catal.Today 127(2007)113-131.)中提出，实现乙烷氧化脱氢商业化，对于催化剂必须同时满足几个关键要求：具有高的乙烯选择性，高的稳定性以及高的乙烯时空产率(>1.0kgC 2H 4/kgcat/h)。特别是高标准的乙烯时空产率被认为是ODHE工艺商业化的主要障碍。
钼钒碲铌多元复合金属氧化物中，纯M1相催化剂是目前具有较大应用前景的催化剂体系，其在较低温度下就能取得较高的乙烷转化率以及乙烯选择性，但是目前专利与文献中报道的MoVTeNbOx纯M1相催化剂，时空产率以及催化剂的生产能力与工业化要求还有一定距离。除此以外，目前纯M1相催化剂一般通过水热法或者沉淀法配以合适的纯化过程来制备，制得的催化剂比表面积通常偏小，制约了其催化活性。
发明内容
有鉴于此，本发明要解决的技术问题在于提供一种高比表面积纯M1相MoVTeNbOx催化剂的制备方法，制备的催化剂具有较高的比表面积。
本发明提供了一种高比表面积纯M1相MoVTeNbOx催化剂的制备方法，包括以下步骤：
S1)将含钼化合物、含钒化合物、含碲化合物、含铌化合物和保护剂混合溶解，得到前驱体-保护剂混合溶液；
所述保护剂为表面活性剂或小分子有机酸及其盐；
S2)将所述前驱体-保护剂混合溶液进行水热反应，分离得到固体；
S3)将所述固体在空气氛围中焙烧，然后在惰性气体中焙烧，再经过氧化氢纯化处理，得到纯M1相MoVTeNbOx催化剂。
优选的，所述保护剂为非离子型高分子表面活性剂、阳离子型表面活性剂或C1～C20的有机酸及其盐。
优选的，所述保护剂为季铵盐表面活性剂，聚醚类表面活性剂，聚酰胺类表面活性剂，C1～C20的还原性有机酸及其盐，或C1～C20的非还原性有机酸及其盐。
优选的，所述保护剂为柠檬酸、柠檬酸钠、柠檬酸铵、油酸、抗坏血酸、草酸、丙二酸钠、草酸钠、聚乙烯吡咯烷酮、十六烷基三甲基溴化铵、聚乙烯醇或聚乙二醇。
优选的，所述步骤S1)具体为：
将含铌化合物在加热条件下溶解，得到第一前驱体溶液；
将含钼化合物、含钒化合物和含碲化合物在加热条件下混合溶解，得到第二前驱体溶液；
将第一前驱体溶液和第二前驱体溶液混合，得到前驱体溶液；
将前驱体溶液与保护剂溶液混合，得到前驱体-保护剂混合溶液。
优选的，所述加热的温度为40～80℃，加热的速率为1～5℃/min。
优选的，所述含钼化合物为钼酸铵；所述含钒化合物为硫酸氧钒和偏钒酸铵中的一种或多种；所述含碲化合物为碲酸；所述含铌化合物为草酸铌铵和草酸铌中的一种或多种。
优选的，所述前驱体-保护剂混合溶液中，Mo、V、Te、Nb和保护剂的摩 尔比为1：(0.15～0.35)：(0.15～0.35)：(0.10～0.15)：(0.069～1.38)。
优选的，所述水热反应的温度为150～200℃，水热反应的时间为24～48h。
优选的，所述在空气氛围中焙烧的温度为200～300℃，时间为1～4h；所述在惰性气体中焙烧的温度为500～600℃，时间为1～4h；所述过氧化氢浓度为5％～20％；所述纯化处理的温度为20～80℃，时间为1～3h。
本发明提供了一种新的制备纯M1相MoVTeNbOx催化剂的方法，利用保护剂，通过水热合成方法，调控了催化剂中物相的尺寸，再用过氧化氢纯化处理，去除M2相后，得到高比表面积以及孔体积的纯M1相MoVTeNbOx催化剂，其具有优异的催化活性，获得了较高的时空产率(STY)，大于1kg C2H4/kg cat/h，且具有较好的稳定性。制备工艺简单，操作简便，重复性好，合成中所使用的保护剂价格低廉，有很好的应用前景。
附图说明
图1为实施例1中催化剂焙烧纯化后的X射线衍射图；
图2为实施例1添加柠檬酸钠保护剂合成的催化剂与比较例1中未添加保护剂合成的催化剂的催化效果对比图；
图3为实施例1添加柠檬酸钠保护剂合成的催化剂的乙烷氧化脱氢活性寿命曲线图；
图4为实施例1添加柠檬酸钠保护剂合成的催化剂在反应流速为50ml/min的乙烷氧化脱氢活性图；
图5为实施例2中催化剂焙烧纯化后的X射线衍射图；
图6为实施例2添加柠檬酸铵保护剂合成的催化剂与比较例1中未添加保护剂合成的催化剂的催化效果对比图；
图7为实施例2添加柠檬酸铵保护剂合成的催化剂的乙烷氧化脱氢活性寿命曲线图；
图8为实施例3中催化剂焙烧纯化后的X射线衍射图；
图9为实施例3添加柠檬酸保护剂合成的催化剂与比较例1中未添加保护剂合成的催化剂的催化效果对比图；
图10为比较例1中催化剂焙烧纯化后的X射线衍射图。
具体实施方式
为了进一步说明本发明，下面结合实施例对本发明提供的高比表面积纯M1相MoVTeNbOx催化剂的制备方法进行详细描述。
本发明提供了一种高比表面积纯M1相MoVTeNbOx催化剂的制备方法，包括以下步骤：
S1)将含钼化合物、含钒化合物、含碲化合物、含铌化合物和保护剂混合溶解，得到前驱体-保护剂混合溶液；
所述保护剂为表面活性剂或小分子有机酸及其盐；
S2)将所述前驱体-保护剂混合溶液进行水热反应，分离得到固体；
S3)将所述固体在空气氛围中焙烧，然后在惰性气体中焙烧，再经过氧化氢纯化处理，得到纯M1相MoVTeNbOx催化剂。
本发明以含钼化合物、含钒化合物、含碲化合物和含铌化合物为原料，制备纯M1相MoVTeNbOx催化剂。
在本发明的一些具体实施例中，所述含钼化合物为钼金属盐，如钼酸铵。
在本发明的一些具体实施例中，所述含钒化合物为钒金属盐，如硫酸氧钒和偏钒酸铵中的一种或多种。
在本发明的一些具体实施例中，所述含碲化合物为碲酸。
在本发明的一些具体实施例中，所述含铌化合物为铌金属盐，如草酸铌铵和草酸铌中的一种或多种。
本发明在制备纯M1相MoVTeNbOx催化剂的过程中，添加了保护剂，提高催化剂的比表面积。
所述保护剂为表面活性剂或小分子有机酸及其盐。
在本发明的一些具体实施例中，所述表面活性剂为非离子型高分子表面活性剂或阳离子型表面活性剂；更优选为季铵盐表面活性剂，聚醚类表面活性剂，聚酰胺类表面活性剂；进一步优选为聚乙烯吡咯烷酮(PVP)、十六烷基三甲基溴化铵(CTAB)、聚乙烯醇(PVA)或聚乙二醇(PEG)。
在本发明的一些具体实施例中，所述小分子有机酸及其盐优选为C1～C20的有机酸及其盐；更优选为C1～C20的还原性有机酸及其盐；进一步优选为柠檬酸、柠檬酸钠、柠檬酸铵、油酸、抗坏血酸或草酸。
在本发明的一些具体实施例中，所述C1～C20的有机酸及其盐优选为C1～C20的非还原性有机酸及其盐，进一步优选为丙二酸钠或草酸钠。
在本发明的一些具体实施例中，所述步骤S1)中，含钼化合物、含钒化合物、含碲化合物、含铌化合物和保护剂混合溶解的溶剂为水。
所述溶解的条件为加热，所述加热的温度优选为40～80℃，进一步优选为80℃；所述加热的速率优选为1～5℃/min，进一步优选为5℃/min。
本发明对所述含钼化合物、含钒化合物、含碲化合物、含铌化合物和保护剂的混合顺序并无特殊限定，可以同时加入混合，或分批加入。
在本发明的一些具体实施例中，首先将含钼化合物、含钒化合物、含碲化合物、含铌化合物在加热条件下混合溶解，然后再与保护剂溶液混合，得到前驱体-保护剂混合溶液。
在本发明的一些具体实施例中，所述步骤S1)具体为：
将含铌化合物在加热条件下溶解，得到第一前驱体溶液；
将含钼化合物、含钒化合物和含碲化合物在加热条件下混合溶解，得到第二前驱体溶液；
将第一前驱体溶液和第二前驱体溶液混合，得到前驱体溶液；
将前驱体溶液与保护剂溶液混合，得到前驱体-保护剂混合溶液。
所述加热的温度和加热的速率同上，在此不再赘述。
在本发明的一些具体实施例中，所述保护剂溶液浓度为0.025～0.5mol/L；所述保护剂溶液与前驱体溶液的体积比为1：(2～10)。
在本发明的一些具体实施例中，所述前驱体-保护剂混合溶液中，所述Mo、V、Te、Nb和保护剂的摩尔比优选为1：(0.15～0.35)：(0.15～0.35)：(0.10～0.15)：(0.069～1.38)。
得到前驱体-保护剂混合溶液后，将其进行水热反应，得到悬浮液，分离得到固体。
本发明对所述分离得到固体的方式并无特殊限定，可以为本领域技术人员熟知的分离方式，如离心或过滤。
本发明对所述水热反应并无特殊限定，在本发明的一些具体实施例中，所述水热反应在水热釜中进行。
在本发明的一些具体实施例中，所述水热反应的温度为150～200℃；所述水热反应的时间为24～48h。
然后将所述固体在空气氛围中焙烧。
在本发明的一些具体实施例中，所述焙烧在马弗炉中进行。
在本发明的一些具体实施例中，所述焙烧的温度为200～300℃，时间为1～4h。
本发明优选的，在空气氛围中进行焙烧之前，还包括：
将得到的固体洗涤，干燥，研磨，得到固体粉末前驱体。
所述干燥的温度优选为60～100℃，干燥的时间优选为8～20h。
然后将所述固体在惰性气体中焙烧。
在本发明的一些具体实施例中，所述惰性气体为氩气、氦气和氮气中的一种或多种。
在本发明的一些具体实施例中，所述在惰性气体中焙烧的温度为500～600℃，时间为1～4h。
在本发明的一些具体实施例中，所述在惰性气体中焙烧在管式炉中进行。
惰性气氛焙烧后，得到M1和M2混合相的MoVTeNbOx催化剂。
再将得到的固体经过氧化氢纯化处理，得到纯M1相MoVTeNbOx催化剂。
所述过氧化氢浓度优选为5％～20％；所述纯化处理的温度为20～80℃，时间为1～3h。
具体的，将得到的固体于20～80℃在过氧化氢溶液中搅拌处理1～3h，去除M2相，用去离子水洗涤后，80～150℃干燥即可。
实验结果表明，本发明制备的纯M1相MoVTeNbOx催化剂具有较高的比表面积和孔体积。实验结果表明，其比表面积大于30m 2/g，孔体积大于0.05cm 3/g，当催化乙烷氧化脱氢制乙烯反应时，具有较高的催化活性、乙烯选择性和乙烯时空产率。
通过上述方法制备的纯M1相MoVTeNbOx催化剂可应用于乙烷氧化脱氢制乙烯反应，或其他本领域技术人员公知的适宜反应中。
本发明在制备纯M1相MoVTeNbOx催化剂的过程中，添加了保护剂，可以缩小M2相尺寸，通过该方法合成的MoVTeNbOx复合氧化物催化剂能有效 控制不同物相的尺寸，经过氧化氢纯化处理除去M2相后，得到纯M1相MoVTeNbOx催化剂，具有丰富孔体积和高比表面积，在乙烷氧化脱氢制乙烯反应中表现出优异的转化率、选择性、时空产率以及稳定性。
并且，本发明提供的方法简单方便，所使用的保护剂成本较低，适合商业化应用。
本发明以下实施例采用的试剂，如气体(乙烷、氧气、氮气和氩气等)及钼酸铵、硫酸氧钒、草酸铌铵、碲酸、柠檬酸、柠檬酸钠等试剂均从市场购得。
实施例1
按Mo、V、Te、Nb和保护剂(柠檬酸钠)的摩尔比为1:0.25:0.23:0.12:0.14，在80℃加热条件下，按比例称取一定量的草酸铌铵溶解于去离子水中，得到溶液1，同样称取一定质量的钼酸铵，硫酸氧钒，碲酸，溶解于去离子水中，得到溶液2，溶液1与溶液2的体积比为1:2.5，将溶液1与溶液2冷却后，混合并搅拌均匀后得到前驱体溶液，再加入0.05mol/L柠檬酸钠溶液，保护剂溶液与前驱体溶液的体积比为1:6.5，继续混合搅拌均匀；将混合均匀的溶液转移到水热釜中，在175℃下水热48h，得到紫色的悬浊液；将水热合成得到的悬浊液经过离心洗涤后，在鼓风干燥箱中80℃烘干过夜，研磨后得到固体粉末前驱体；将前驱体固体粉末置于马弗炉中，在空气氛围下250℃焙烧2h，随后将粉末置于管式炉中，在氩气氛围下600℃焙烧2h，随后得到M1和M2混合相的MoVTeNbOx催化剂，此时催化剂的比表面积(BET)为0.8m 2/g，孔体积(Pore Volume)为0.0013cm 3/g；再将该混合相催化剂置于体积分数为7.5％过氧化氢溶液中，加热至60℃，搅拌3h后，用去离子水离心洗涤后，在鼓风干燥箱中110℃烘干过夜得到纯M1相MoVTeNbOx催化剂，其比表面积(BET)为48.9m 2/g，孔体积(Pore Volume)为0.10cm 3/g。
对制备的催化剂进行XRD检测，结果见图1，可以看出，经过600℃氩气中焙烧后的催化剂的XRD谱图中仅含有M1相的衍射峰，说明通过柠檬酸钠保护剂合成的催化剂，能将M2相尺寸变小，从XRD上观察不到其衍射峰，经过过氧化氢处理后，将小尺寸的M2相溶解后，其孔体积明显增大，从而增大了催化剂的比表面积。
对制备的催化剂进行催化性能测试：
取上述催化剂200mg与400mg碳化硅稀释混合后，置于微型固定床反应器上，反应气氛为乙烷、氧气、氩气的混合气(气体比例为3:2:5)，气体总流速为30ml/min，反应后气体组成通过在线气相色谱检测(岛津GC-2014气相色谱仪，SH-Rt-Alumina BOND/KCl色谱柱接FID检测器，Porapak Q色谱柱接TCD检测器，高纯氩作为载气)，其具体催化活性如图2所示，其中反应温度为375℃时，乙烷转化率为37.4％，乙烯选择性为92.1％，乙烯时空产率(STY)为1.08kgC 2H 4/kgcat/h；反应温度在425℃时，乙烷转化率为71.0％，乙烯选择性为84.2％，乙烯时空产率(STY)为1.88kg C 2H 4/kgcat/h。
同时催化剂在425℃时的寿命测试如图3所示，乙烷的转化率稳定在66.9％～72.1％左右，乙烯选择性稳定在80.5％～84.6％左右，能保持200小时没有明显失活现象发生。
进一步增大空速，取上述催化剂200mg与400mg碳化硅稀释混合后，置于微型固定床反应器上，反应气氛为乙烷、氧气、氩气的混合气(气体比例为3:2:5)，气体总流速为50ml/min，反应后气体组成通过在线气相色谱检测(岛津GC-2014气相色谱仪，SH-Rt-Alumina BOND/KCl色谱柱接FID检测器，Porapak Q色谱柱接TCD检测器，高纯氩作为载气)，其具体催化活性如图4所示，反应温度为425℃时，乙烷转化率为71.4％，乙烯选择性为83.4％，其乙烯时空产率(STY)能达到3.05kg C 2H 4/kgcat/h。
实施例2
按Mo、V、Te、Nb和保护剂(柠檬酸铵)的摩尔比为1:0.25:0.23:0.12:0.14，在80℃加热条件下，按比例称取一定量的草酸铌铵溶解于去离子水中，得到溶液1，同样称取一定质量的钼酸铵，硫酸氧钒，碲酸，溶解于去离子水中，得到溶液2，溶液1与溶液2的体积比为1:2.5，将溶液1与溶液2冷却后，混合并搅拌均匀后得到前驱体溶液。在前驱体溶液中加入0.05mol/L的柠檬酸铵保护剂溶液，保护剂溶液与前驱体溶液的体积比为1:8.5，混合搅拌均匀后，转移至水热釜中，175℃水热48h后，得到淡紫色悬浊液；将此悬浊液离心洗涤后，在鼓风干燥箱中80℃烘干过夜，随后在空气氛围下300℃焙烧2h，接着在氩气氛围下600℃焙烧2h，随后得到M1和M2混合相的MoVTeNbOx催化剂，此时催化剂的比表面积(BET)为1.2m 2/g，孔体积(Pore Volume)为 0.0078cm 3/g；再将该混合相催化剂置于体积分数为7.5％过氧化氢溶液中，加热至60℃，搅拌3h后，用去离子水离心洗涤后，在鼓风干燥箱中110℃烘干过夜得到纯M1相MoVTeNbOx催化剂，其比表面积(BET)为43.0m 2/g，孔体积(Pore Volume)为0.12cm 3/g。
对制备的催化剂进行XRD检测，结果见图5，由图5可以看出结果与实施例1相似，说明通过柠檬酸铵保护剂合成的催化剂，将M2相尺寸变小，经过过氧化氢处理后，将小尺寸的M2相溶解后，其孔体积明显增大，从而增大了催化剂的比表面积。
对制备的催化剂进行催化性能测试：
取上述催化剂200mg与400mg碳化硅稀释混合后置于微型固定床反应器上，反应气氛为乙烷、氧气、氩气的混合气(气体比例为3:2:5)，气体总流速为30ml/min；其具体催化活性如图6所示，由图6可以看出，反应温度为375℃时乙烷转化率为39.6％，乙烯选择性为92.1％，乙烯时空产率(STY)为1.15kgC 2H 4/kgcat/h；反应温度在425℃时，乙烷转化率为72.4％，乙烯选择性为85.4％，乙烯时空产率(STY)为1.94kgC 2H 4/kgcat/h。其反应活性也明显高于不添加保护剂合成的比较例1的催化剂。
同时催化剂在375℃时的寿命测试如图7所示，由图7可以看出，乙烷的转化率稳定在39.6％左右，乙烯选择性稳定在87％～92％左右，能保持144小时没有明显失活现象发生。
实施例3
按Mo、V、Te、Nb和保护剂(柠檬酸)的摩尔比为1:0.25:0.23:0.12:0.28，在80℃加热条件下，按比例称取一定量的草酸铌铵溶解于去离子水中，得到溶液1，同样称取一定质量的钼酸铵，硫酸氧钒，碲酸，溶解于去离子水中，得到溶液2，溶液1与溶液2的体积比为1:2.5，将溶液1与溶液2冷却后，混合并搅拌均匀后得到前驱体溶液。在前驱体溶液中加入0.1mol/L的柠檬酸保护剂溶液，保护剂溶液与前驱体溶液的体积比为1:7.5，混合搅拌均匀后，转移至水热釜中，180℃水热48h后，得到淡紫色悬浊液；将此悬浊液离心洗涤后，在鼓风干燥箱中80℃烘干过夜，随后在空气氛围下250℃焙烧2h，接着在氩气氛围下600℃焙烧2h，随后得到M1和M2混合相的MoVTeNbOx催化 剂，此时催化剂的比表面积(BET)为1.7m 2/g，孔体积(Pore Volume)为0.0047cm 3/g；再将该混合相催化剂置于体积分数为15％过氧化氢溶液中，加热至60℃，搅拌3h后，用去离子水离心洗涤后，在鼓风干燥箱中110℃烘干过夜得到纯M1相MoVTeNbOx催化剂，其比表面积(BET)为37.8m 2/g，孔体积(Pore Volume)为0.069cm 3/g。
对制备的催化剂进行XRD检测，结果见图8，由图8可以看出，经过600℃氩气中焙烧后的催化剂同时存在M1，M2相的衍射峰，通过过氧化氢处理后得到纯M1相MoVTeNbOx催化剂。
对制备的催化剂进行催化性能测试：
取上述催化剂200mg与400mg碳化硅稀释混合后置于微型固定床反应器上，反应气氛为乙烷、氧气、氩气的混合气(气体比例为3:2:5)，气体总流速为30ml/min；其具体催化活性如图9所示，由图9可以看出，反应温度为375℃时乙烷转化率为25.2％，乙烯选择性为91.9％，乙烯时空产率(STY)为0.73kg C2H4/kg cat/h；反应温度在425℃时，乙烷转化率为60.9％，乙烯选择性为80.1％，乙烯时空产率(STY)为1.53kg C2H4/kg cat/h。其反应活性也高于不添加保护剂合成的比较例1的催化剂。
实施例4
按Mo、V、Te、Nb和保护剂(丙二酸钠)的摩尔比为1:0.25:0.23:0.12:0.14在80℃加热条件下，按比例称取一定量的草酸铌铵溶解于去离子水中，得到溶液1，同样称取一定质量的钼酸铵，硫酸氧钒，碲酸，溶解于去离子水中，得到溶液2，溶液1与溶液2的体积比为1:2.5，将溶液1与溶液2冷却后，混合并搅拌均匀后得到前驱体溶液。在前驱体溶液中加入0.05mol/L的丙二酸钠溶液，保护剂溶液与前驱体溶液的体积比为1:5.5，混合搅拌均匀后，转移至水热釜中，175℃水热48h后，得到紫色悬浊液；将此悬浊液离心洗涤后，在鼓风干燥箱中80℃烘干过夜，随后在空气氛围下250℃焙烧2h，接着在氩气氛围下600℃焙烧2h，随后得到M1和M2混合相的MoVTeNbOx催化剂，此时催化剂的比表面积(BET)为1.7m 2/g，孔体积(Pore Volume)为0.0048cm 3/g；再将该混合相催化剂置于体积分数为7.5％过氧化氢溶液中，加热至60℃，搅拌3h后，用去离子水离心洗涤后，在鼓风干燥箱中110℃烘干过夜得到纯M1 相MoVTeNbOx催化剂，其比表面积(BET)为45.2m 2/g，孔体积(Pore Volume)为0.14cm 3/g。
实施例5
按Mo、V、Te、Nb和保护剂(聚乙烯吡咯烷酮)的摩尔比为1:0.25:0.23:0.12:1.25，在80℃加热条件下，按比例称取一定量的草酸铌铵溶解于去离子水中，得到溶液1，同样称取一定质量的钼酸铵，硫酸氧钒，碲酸，溶解于去离子水中，得到溶液2，溶液1与溶液2的体积比为1:2.5，将溶液1与溶液2冷却后，混合并搅拌均匀后得到前驱体溶液。在前驱体溶液中加入0.45mol/L的聚乙烯吡咯烷酮(PVP)作为保护剂，保护剂溶液与前驱体溶液的体积比为1:7.5，充分混合搅拌均匀后，转移至水热釜中180℃水热48h后，得到深绿色悬浊液；将此悬浊液离心洗涤后，在鼓风干燥箱中80℃烘干过夜，随后在空气氛围下300℃焙烧2h，接着在氩气氛围下600℃焙烧2h，此时催化剂的比表面积(BET)为5.3m 2/g，孔体积(Pore Volume)为0.011cm 3/g；再将该混合相催化剂置于体积分数为7.5％过氧化氢溶液中，加热至60℃，搅拌3h后，用去离子水离心洗涤后，在鼓风干燥箱中110℃烘干过夜得到纯M1相MoVTeNbOx催化剂，其比表面积(BET)为72.1m 2/g，孔体积(Pore Volume)为0.25cm 3/g。
实施例6
按Mo、V、Te、Nb和保护剂(十六烷基三甲基溴化铵)的摩尔比为1:0.25:0.23:0.12:0.069，在80℃加热条件下，按比例称取一定量的草酸铌铵溶解于去离子水中，得到溶液1，同样称取一定质量的钼酸铵，硫酸氧钒，碲酸，溶解于去离子水中，得到溶液2，溶液1与溶液2的体积比为1:2.5，将溶液1与溶液2冷却后，混合并搅拌均匀后得到前驱体溶液。在前驱体溶液中加入0.05mol/L的十六烷基三甲基溴化铵(CTAB)作为保护剂，保护剂溶液与前驱体溶液的体积比为1:6.5，充分混合搅拌均匀后，转移至水热釜中180℃水热48h后，得到深绿色悬浊液；将此悬浊液离心洗涤后，在鼓风干燥箱中80℃烘干过夜，随后在空气氛围下300℃焙烧2h，接着在氩气氛围下600℃焙烧2h，此时催化剂的比表面积(BET)为2.9m 2/g，孔体积(Pore Volume)为0.0083cm 3/g；再将该混合相催化剂置于体积分数为7.5％过氧化氢溶液中，加热至 60℃，搅拌3h后，用去离子水离心洗涤后，在鼓风干燥箱中110℃烘干过夜得到纯M1相MoVTeNbOx催化剂，其比表面积(BET)为34.8m 2/g，孔体积(Pore Volume)为0.05cm 3/g。
比较例1
按Mo:V:Te:Nb的摩尔比为1:0.25:0.23:0.12，在80℃加热条件下，按比例称取一定量的草酸铌铵溶解于去离子水中，得到溶液1，同样称取一定质量的钼酸铵，硫酸氧钒，碲酸，溶解于去离子水中，得到溶液2，溶液1与溶液2的体积比为1:2.5，将溶液1与溶液2冷却后，混合并搅拌均匀后得到前驱体溶液。将所述前驱体溶液经过175℃水热48h，得到紫色悬浊液，经离心洗涤后，80℃烘干过夜；先在250℃空气中焙烧2h，然后再氩气中600℃焙烧2h后，将得到的粉末催化剂于7.5％过氧化氢溶液中，加热至60℃处理3h；用去离子水离心洗涤后，110℃烘干过夜得到纯M1相MoVTeNbOx催化剂，其比表面积(BET)为20.0m 2/g，孔体积(Pore Volume)为0.033cm 3/g。
对制备的催化剂进行XRD检测，结果见图10，由图10可以看出，经过600℃氩气中焙烧后的催化剂同时存在M1，M2相的衍射峰，通过过氧化氢处理后得到纯M1相MoVTeNbOx催化剂。
对制备的催化剂进行催化性能测试：
取上述催化剂200mg与400mg碳化硅稀释混合后置于微型固定床反应器上，反应气氛为乙烷、氧气、氩气的混合气(气体比例为3:2:5)，气体总流速为30ml/min；反应温度为375℃时乙烷转化率为16.4％，乙烯选择性为93.1％，乙烯时空产率(STY)为0.48kg C2H4/kg cat/h；反应温度在425℃时，乙烷转化率为41.1％，乙烯选择性为84.8％，乙烯时空产率(STY)为1.09kg C2H4/kg cat/h。
由上述实施例及比较例可知，本发明制备的纯M1相MoVTeNbOx催化剂，具有更高的比表面积以及催化活性和稳定性。
以上实施例的说明只是用于帮助理解本发明的方法及其核心思想。应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以对本发明进行若干改进和修饰，这些改进和修饰也落入本发明权利要求的保护范围内。

Claims (10)

  1. 一种高比表面积纯M1相MoVTeNbOx催化剂的制备方法，包括以下步骤：
    S1)将含钼化合物、含钒化合物、含碲化合物、含铌化合物和保护剂混合溶解，得到前驱体-保护剂混合溶液；
    所述保护剂为表面活性剂或小分子有机酸及其盐；
    S2)将所述前驱体-保护剂混合溶液进行水热反应，分离得到固体；
    S3)将所述固体在空气氛围中焙烧，然后在惰性气体中焙烧，再经过氧化氢纯化处理，得到纯M1相MoVTeNbOx催化剂。
  2. 根据权利要求1所述的制备方法，其特征在于，所述保护剂为非离子型高分子表面活性剂、阳离子型表面活性剂或C1～C20的有机酸及其盐。
  3. 根据权利要求2所述的制备方法，其特征在于，所述保护剂为季铵盐表面活性剂，聚醚类表面活性剂，聚酰胺类表面活性剂，C1～C20的还原性有机酸及其盐，或C1～C20的非还原性有机酸及其盐。
  4. 根据权利要求3所述的制备方法，其特征在于，所述保护剂为柠檬酸、柠檬酸钠、柠檬酸铵、油酸、抗坏血酸、草酸、丙二酸钠、草酸钠、聚乙烯吡咯烷酮、十六烷基三甲基溴化铵、聚乙烯醇或聚乙二醇。
  5. 根据权利要求1所述的制备方法，其特征在于，所述步骤S1)具体为：
    将含铌化合物在加热条件下溶解，得到第一前驱体溶液；
    将含钼化合物、含钒化合物和含碲化合物在加热条件下混合溶解，得到第二前驱体溶液；
    将第一前驱体溶液和第二前驱体溶液混合，得到前驱体溶液；
    将前驱体溶液与保护剂溶液混合，得到前驱体-保护剂混合溶液。
  6. 根据权利要求5所述的制备方法，其特征在于，所述加热的温度为40～80℃，加热的速率为1～5℃/min。
  7. 根据权利要求1所述的制备方法，其特征在于，所述含钼化合物为钼酸铵；所述含钒化合物为硫酸氧钒和偏钒酸铵中的一种或多种；所述含碲化合物为碲酸；所述含铌化合物为草酸铌铵和草酸铌中的一种或多种。
  8. 根据权利要求1所述的制备方法，其特征在于，所述前驱体-保护剂混合溶液中，Mo、V、Te、Nb和保护剂的摩尔比为1：(0.15～0.35)：(0.15～0.35)：(0.10～0.15)：(0.069～1.38)。
  9. 根据权利要求1所述的制备方法，其特征在于，所述水热反应的温度为150～200℃，水热反应的时间为24～48h。
  10. 根据权利要求1所述的制备方法，其特征在于，所述在空气氛围中焙烧的温度为200～300℃，时间为1～4h；所述在惰性气体中焙烧的温度为500～600℃，时间为1～4h；所述过氧化氢浓度为5％～20％；所述纯化处理的温度为20～80℃，时间为1～3h。
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