Mixed phase catalyst for one-step ammoxidation of propane to prepare acrylonitrile acid
阅读说明：本技术 一种用于丙烷一步氨氧化制丙烯腈酸反应的混合相催化剂 (Mixed phase catalyst for one-step ammoxidation of propane to prepare acrylonitrile acid ) 是由 杨维慎 楚文玲 王红心 刘延纯 王宏奎 于 2018-08-16 设计创作，主要内容包括：一种用于丙烷一步氨氧化制丙烯腈反应的混合相复合金属氧化物催化剂及其制备,通过原位一步制备出同时含有主相和辅相的混合相复合金属氧化物催化剂或以固相球磨法将分别制备的主相和辅相混合均匀得到混合相催化剂：催化剂主相为Mo、V、Sb、Te、Nb、Bi、As、Pd中4种或4种以上元素组成的复合金属氧化物；辅助相为Mo、V、Bi、K、Fe、Ba、Cs中3种或3种以上元素组成的复合金属氧化物。合成出的混合相复合金属氧化物催化剂在丙烷一步氨氧化制丙烯腈反应中表现出由于纯相的催化活性,也由于专利报导的最好结果。具有工业应用的前景。(A mixed phase composite metal oxide catalyst for the reaction of preparing acrylonitrile by propane one-step ammoxidation and a preparation method thereof are disclosed, wherein the mixed phase composite metal oxide catalyst simultaneously containing a main phase and an auxiliary phase is prepared in situ one step, or the main phase and the auxiliary phase which are respectively prepared are uniformly mixed by a solid phase ball milling method to obtain the mixed phase catalyst: the main phase of the catalyst is a composite metal oxide consisting of 4 or more than 4 elements of Mo, V, Sb, Te, Nb, Bi, As and Pd; the auxiliary phase is a composite metal oxide consisting of 3 or more than 3 elements of Mo, V, Bi, K, Fe, Ba and Cs. The synthesized mixed phase composite metal oxide catalyst shows pure phase catalytic activity in the reaction of preparing acrylonitrile by propane one-step ammoxidation, and also shows the best result reported by the patent. Has the prospect of industrial application.)
1. A mixed phase catalyst characterized by: the main phase of the catalyst is a composite metal oxide consisting of 4 or more than 4 elements of Mo, V, Sb, Te, Nb, Bi, As and Pd, and the auxiliary phase is a composite metal oxide consisting of 3 or more than 3 elements of Mo, V, Bi, K, Fe, Ba and Cs.
2. The mixed-phase catalyst according to claim 1, wherein the structure of the catalyst is preferably MoVTeNb or MoVSbNb composite metal oxide having a main phase structure and MoVM having a secondary phase structure1A composite metal oxide composition of M1Te, Sb or Bi.
3. A process for the preparation of a mixed phase catalyst according to any one of claims 1-2, characterized in that it is prepared by process one or process two:
the first method comprises the following steps:
(1) dissolving metal precursor salt of elements required by the mixed structure catalyst in distilled water according to a proportion, and stirring and dissolving at 60-80 ℃ to obtain a mixed solution;
(2) reacting the mixed solution by a hydrothermal synthesis method, a rotary evaporation method or a precipitation method, filtering, and drying at 80-120 ℃ to obtain a powder material;
(3) the powder material is put in a static state N2Atmosphere, N2/H2Or roasting the mixture for 2 to 10 hours at 500 to 800 ℃ in air atmosphere to obtain the mixed phase catalyst;
the hydrothermal method comprises the following steps: transferring the mixed solution obtained in the step (1) into a high-pressure synthesis kettle, and carrying out hydrothermal synthesis at the temperature of 150-200 ℃ for 10-48 hours;
the rotary evaporation method comprises the following steps: transferring the mixed solution obtained in the step (1) into a rotary evaporator, and carrying out rotary evaporation on the solution for 2-10 hours at the temperature of 60-80 ℃ under the condition of vacuum pumping;
the precipitation method comprises the following steps: dropwise adding an ammonia carbonate solution with a certain concentration into the mixed solution obtained in the step (1) under the condition of vigorous stirring at the temperature of 60-80 ℃, and gradually generating precipitates; after the dropwise addition, stirring for 3-10 hours at the temperature of 60-80 ℃,
the second method comprises the following steps:
(1) preparation of composite oxide with main phase structure: selecting a main phase metal precursor, and preparing a main phase structure composite oxide by changing the type and corresponding proportion of the metal precursor according to the first method;
(2) preparing an auxiliary phase structure composite oxide: selecting an auxiliary phase metal precursor, and preparing the auxiliary phase structure composite oxide by changing the type and corresponding proportion of the metal precursor according to the first method;
(3) and (3) mixing and ball-milling the main-phase structure composite oxide and the auxiliary-phase structure composite oxide by adopting a solid-phase ball milling method to obtain the mixed-phase catalyst, wherein the ball-milling time is 10-30 hours, and the ball-milling speed is 600-1000 r/h.
4. Method for the preparation in a mixed phase catalyst according to claim 3, characterized in that Mo and V and Nb and Bi and Te orThe precursor of Sb is mixed to prepare a mixed oxide precursor, and the MoVTeNb or MoVSbNb composition with a main phase structure and the MoVM with an auxiliary phase structure can be obtained in situ after high-temperature roasting1Composition of mixed-phase catalyst, M1Te or Sb or Bi.
5. The method of claim 3, wherein the MoVM having a main phase structure is prepared by the second method2And MoVM of auxiliary phase structure3Mixing two crystal phases by a solid phase ball milling method to obtain a mixed phase catalyst, wherein M is2Is 2 or more than 2 of Te, Nb, Sb, Bi and Pd, and M is3Is one of Te, Sb or Bi.
6. The use of a mixed phase catalyst according to any one of claims 1-2 in the one-step ammoxidation of propane to acrylonitrile, wherein: the reaction temperature is 400-700 ℃, the reaction pressure is normal pressure, and the volume ratio of reaction gas is V (C)3H8)/V(air)/V(NH3) The reaction space velocity is between 500 and 1500mL/g-cat/h, wherein the reaction space velocity is between 1/10 and 20/0.5 and 3.
Technical Field
The invention belongs to the field of chemical industry, and particularly relates to a mixed phase catalyst for a reaction of preparing acrylonitrile by propane ammoxidation and a preparation method thereof.
Background
Acrylonitrile is an important organic chemical raw material, and is prepared from three synthetic materials: the polymer material such as synthetic fiber, synthetic resin, synthetic rubber and the like can be widely applied. Acrylonitrile polymers and acrylonitrile derivatives also have important uses. With the continuous development and application of acrylonitrile downstream fine chemical products, the demand of the acrylonitrile downstream fine chemical products is continuously increased.
Currently, 95% of acrylonitrile worldwide is produced by the propylene ammoxidation process developed by Mobil oil Co., U.S.A. With the increasing shortage of propylene resources and the serious shortage of propane resource utilization rate with rich reserves in the world, the process for producing acrylonitrile by direct ammoxidation by taking propane as a raw material becomes a research hotspot of alkane utilization and catalytic conversion technology with the outstanding advantage of price existing between propane and propylene, and has extremely high economic value. Meanwhile, the propane is rich in source and is a main component in oil field gas, natural gas and refinery gas. The oil field gas in Daqing, Tarim and the like in China contains about 6% of propane, the condensate oil contains 3-6% of propane, the liquefied petroleum gas contains about 60% of propane, and the natural gas moisture contains about 15% of propane. In the past, propane has generally been used as a fuel, in small quantities as a solvent, or as a feedstock for steam cracking to produce ethylene and propylene. In recent years, people increasingly pay more attention to the catalytic processing of propane into intermediate chemical products or chemical raw materials with high added values, and in the process of producing the chemical products with high added values by replacing low-carbon olefins with low-carbon alkanes, the direct ammoxidation production of acrylonitrile by replacing propylene with propane as a raw material is considered to be one of the technologies most likely to realize industrialization.
In conclusion, the propane has low price and abundant sources, so that the direct synthesis of acrylonitrile by one-step ammoxidation of propane has obvious economic benefit and practical significance. The development of a catalyst for preparing acrylonitrile by propane ammoxidation with high activity, high selectivity and high stability is imperative.
The catalysts for the reaction of preparing acrylonitrile by one-step oxidation of propane reported in the literature and patents at present are all multi-component and multi-functional catalysts generally. Wherein the mixed metal oxide Mo-V-Te-Nb-O catalyst has good catalytic performance for the reaction. In patents on MoVTeNb catalyst reported by Mitsubishi and Asahi of Japan (European Patent No.529853(1992) and European Patent No.895809(1998)), the mixed metal oxides are all of pure phase structure, and the yields of acrylonitrile are as high as about 60%, respectively.
Disclosure of Invention
The invention aims to improve the catalytic performance of a composite metal oxide catalyst in the reaction of preparing acrylonitrile by one-step ammoxidation of propane by controlling the composition and structure of two phases of the composite metal oxide and modulating the synergistic effect between the two phases.
In order to achieve the above object, the present invention provides a mixed phase catalyst for the reaction of producing acrylonitrile by one-step ammoxidation of propane, wherein the mixed phase comprises a mixture of different kinds of composite oxides and a mixture of different crystal phases, and the main phase of the mixed phase catalyst is a composite metal oxide composed of 4 or more than 4 elements of Mo, V, Sb, Te, Nb, Bi, As and Pd; the auxiliary phase is a composite metal oxide composed of 3 or more than 3 elements of Mo, V, Bi, K, Fe, Ba and Cs, and is preferably MoVTeNbO or MoVSbNbO composite metal oxide with a main phase structure and MoVM with an auxiliary phase structure1A composite metal oxide composition of M1Te, Sb or Bi.
In another aspect, the invention provides a method for preparing the mixed phase catalyst, the method comprising two steps:
the first method comprises the following steps:
(1) dissolving metal precursor salt of elements required by the mixed structure catalyst in distilled water according to a proportion, and stirring and dissolving at 60-80 ℃ to obtain a mixed solution;
(2) reacting the mixed solution by a hydrothermal synthesis method, a rotary evaporation method or a precipitation method, filtering, and drying at 80-120 ℃ to obtain a powder material;
(3) will be at the topThe powder material is in a static state N2Atmosphere, N2/H2Or roasting the mixed phase catalyst for 2 to 10 hours at 500 to 800 ℃ in an air atmosphere to obtain the mixed phase catalyst.
The hydrothermal method comprises the following steps: and (2) transferring the mixed solution obtained in the step (1) into a high-pressure synthesis kettle, and carrying out hydrothermal synthesis at the temperature of 150-200 ℃ for 10-48 hours.
The rotary evaporation method comprises the following steps: and (2) transferring the mixed solution obtained in the step (1) to a rotary evaporator, and carrying out rotary evaporation on the solution for 2-10 hours at the temperature of 60-80 ℃ under the vacuum-pumping condition.
The precipitation method comprises the following steps: and (2) dropwise adding an ammonia carbonate solution with a certain concentration into the mixed solution obtained in the step (1) under the condition of vigorous stirring at the temperature of 60-80 ℃, and gradually generating precipitates. And after the dropwise addition is finished, stirring for 3-10 hours at the temperature of 60-80 ℃.
The second method comprises the following steps:
(1) preparation of composite oxide with main phase structure: selecting a main phase metal precursor, and preparing a main phase structure composite oxide by changing the type and corresponding proportion of the metal precursor according to the first method;
(2) preparing an auxiliary phase structure composite oxide: selecting an auxiliary item metal precursor, and preparing the auxiliary phase structure composite oxide by changing the type and corresponding proportion of the metal precursor according to the first method;
(3) and (3) mixing and ball-milling the main-phase structure composite oxide and the auxiliary-phase structure composite oxide by adopting a solid-phase ball milling method to obtain the mixed-phase catalyst, wherein the ball-milling time is 10-30 hours, and the ball-milling speed is 600-1000 r/h.
The catalyst of the invention can obtain the mixed phase in situ by one step of the method, and can also obtain different single phases by two steps of the method and then mix the different single phases to obtain the mixed phase.
Mixing precursors of Mo, V, Te (Sb), Nb and Bi according to the first method to prepare a mixed oxide precursor, and roasting at high temperature to obtain MoVTeNb or MoVSbNb composition with a main phase structure and MoVM with an auxiliary phase structure in situ1Composition of mixed-phase catalyst, M1Te, Sb or Bi.
Preparation of MoVM with Main phase Structure according to the second Process2(
When at least four metal precursor elements are selected to be in accordance with the composition of the main phase structure and the composition of the auxiliary phase structure, the synthesized catalyst can be effectively controlled to be in a mixed phase structure or a single main phase structure by changing the metal precursor proportion, when the proportion is Mo: a mixed phase structure catalyst is prepared when Nb is 1: 0.1-0.3: 0.3-0.6, a single main phase catalyst is obtained when the ratio of Mo, V, Te and Nb is 1: 0.1-0.3: 0.05-0.2,
the invention also provides an application of the mixed phase catalyst in the reaction of preparing acrylonitrile by propane one-step ammoxidation, which is characterized in that: the reaction temperature is 400-700 ℃, the reaction pressure is normal pressure, and the volume ratio of reaction gas is V (C)3H8)/V(air)/V(NH3) The reaction space velocity is between 500 and 1500mL/g-cat/h, wherein the reaction space velocity is between 1/10 and 20/0.5 and 3.
The mixed phase composite metal oxide catalyst for the reaction of preparing acrylonitrile by one-step oxidation of propane provided by the invention modulates the synergistic effect of two phases by controlling the composition and the structure of the two phases, thereby improving the activity and the selectivity of the catalyst for preparing acrylonitrile by one-step ammoxidation of propane.
Compared with a pure phase catalyst reported in the literature, the method can further improve the propane conversion rate and the acrylonitrile selectivity, and shows very high industrial application prospect.
Drawings
FIG. 1 is an XRD spectrum of a mixed phase Mo-V-Te-Nb-Bi-O catalyst prepared in example 1.
FIG. 2 is an XRD spectrum (a) of M1 phase Mo-V-Te-Nb-O catalyst and an XRD spectrum (b) of M2 phase Mo-V-Bi-O catalyst prepared in example 3.
FIG. 3 is an XRD spectrum of the mixed phase Mo-V-Te-Nb-O catalyst prepared in example 5.
FIG. 4 shows the stability results of ammoxidation of propane in one step to acrylonitrile in the mixed phase Mo-V-Te-Nb-Bi-O catalyst prepared in example 1.
Detailed Description
In the reaction of preparing acrylonitrile by propane one-step ammoxidation, the reaction product is divided into gas phase and liquid phase. The gas phase product comprises CO and CO2And C3H6. The liquid phase product comprises the target product acrylonitrile, a small amount of by-product acetonitrile and HCN.
The conversion and selectivity as well as the yield were calculated as follows:
yield (%). conversion. times. selectivity. times.100
(Mi: the number of moles of a product; ni: the number of carbon atoms contained in a molecule of a product)