preparation method of catalyst for preparing methanol hollow sphere by carrier-free carbon dioxide hydrogenation
阅读说明：本技术 一种无载体二氧化碳加氢制甲醇空心球催化剂的制备方法 (preparation method of catalyst for preparing methanol hollow sphere by carrier-free carbon dioxide hydrogenation ) 是由 亓士超 朱蓉蓉 喻国兴 周睿 孙林兵 刘晓勤 于 2019-08-27 设计创作，主要内容包括：本发明公开了一种无载体二氧化碳加氢制甲醇空心球催化剂的制备方法,其制备的催化剂可应用到二氧化碳加氢制甲醇上。该方法包括以下步聚：(1)蔗糖中加入去离子水,室温下搅拌至其完全溶解,于160-220℃反应8-24h；(2)将所得悬浊液进行离心分离,置于80-120℃烘箱干燥24h或以上时间；(3)取上述步骤(2)中干燥所得不溶物加入乙二醇溶液进行溶解,向溶液中加入前驱体,得到前驱体悬浊液；(4)将前驱体悬浊液进行离心分离并干燥；(5)将干燥后的产品在空气中进行焙烧3-5小时；(6)将焙烧所得产品在200-400℃下于氢气流中还原1-3h,得到无载体二氧化碳加氢制甲醇空心球催化剂。(the invention discloses a preparation method of a hollow sphere catalyst for preparing methanol by carbon dioxide hydrogenation without a carrier, and the prepared catalyst can be applied to preparing methanol by carbon dioxide hydrogenation. The method comprises the following steps: (1) adding deionized water into sucrose, stirring at room temperature until the sucrose is completely dissolved, and reacting at 160-220 deg.C for 8-24 h; (2) centrifugally separating the obtained suspension, and drying in an oven at 80-120 deg.C for 24 hr or more; (3) adding an insoluble substance obtained by drying in the step (2) into an ethylene glycol solution for dissolving, and adding a precursor into the solution to obtain a precursor suspension; (4) carrying out centrifugal separation on the precursor suspension and drying; (5) roasting the dried product in air for 3-5 hours; (6) reducing the roasted product in hydrogen flow at 200-400 ℃ for 1-3h to obtain the catalyst for preparing the hollow methanol sphere by the carrier-free carbon dioxide hydrogenation.)
1. A preparation method of a catalyst for preparing a methanol hollow sphere by carrier-free carbon dioxide hydrogenation is characterized by comprising the following steps:
(1) weighing sucrose in a beaker, adding deionized water, stirring at room temperature until the sucrose is completely dissolved, transferring the obtained transparent solution to a hydrothermal kettle with a polytetrafluoroethylene lining, sealing, putting the hydrothermal kettle into an oven, and reacting at 160-220 ℃ for 8-24 hours;
(2) centrifuging the suspension obtained by the hydrothermal reaction, washing the obtained insoluble substances with water and ethanol for 3-5 times, and drying in an oven at 80-120 deg.C for 24 hr or more;
(3) putting the insoluble substances obtained in the step (2) into a three-neck flask, adding an ethylene glycol solution for dissolving, adding a precursor into the solution after ultrasonic dispersion is uniform, heating the solution to 100-140 ℃ under reflux, and stirring the solution at a high speed for 8-14h to obtain a precursor suspension of the mixed component catalyst;
(4) centrifugally separating the stirred precursor suspension, washing the obtained product with water and ethanol twice respectively, and drying in an oven at 80-120 ℃ for 24 hours or more;
(5) roasting the product dried in the step (4) in air at 450-600 ℃ for 3-5 hours;
(6) And (3) placing the product obtained by roasting into a tubular furnace, and reducing for 1-3h in hydrogen flow at the temperature of 200-400 ℃ to obtain the carrier-free carbon dioxide hydrogenation methanol hollow sphere catalyst.
2. The method according to claim 1, wherein the precursor is a mixture of copper nitrate and zinc nitrate, and the molar ratio of copper nitrate to zinc nitrate is 7: 3-3: 7.
Technical Field
the invention relates to a preparation method of a catalyst, in particular to a preparation method of a catalyst for preparing a hollow methanol sphere by carrier-free carbon dioxide hydrogenation.
Background
Methanol is an important chemical intermediate, is an ideal liquid fuel additive, has great industrial demand, is one of important sources of industrial methanol in the process of preparing methanol by carbon dioxide hydrogenation, and can greatly improve the utilization rate of carbon atoms. The rapid development of the modern industry and the great changes in human lifestyle have intensified the combustion of chemical fuels and the accumulation of carbon dioxide in the atmosphere, with the impact of the greenhouse effect becoming increasingly significant. How to effectively utilize carbon dioxide, reduce the emission of the carbon dioxide and realize green economy and sustainable development is an important problem to be solved urgently. Carbon dioxide is often used as a raw material in industry, and is converted into important organic chemical raw materials such as methanol, formic acid and the like by utilizing the reaction of the carbon dioxide and hydrogen, so that the emission reduction of the carbon dioxide is realized, wherein the methanol can be used as a raw material for producing formaldehyde, acetic acid and biodiesel and is an important material for organic chemical industry.
the reaction activity of the carbon dioxide is very low, and the hydrogenation of the carbon dioxide is catalyzed by a load type copper-based catalyst commonly used in industry, and Al is commonly used2O3、ZrO2、SiO2、TiO2and the porous material is used as a carrier for loading active components of copper and zinc oxide. The common preparation methods include an impregnation method, a deposition precipitation method, a chemical vapor deposition method, an ion exchange method and the like. (1) The impregnation method comprises the steps of immersing a proper amount of carrier in a solution containing active components, removing residual liquid after the immersion is balanced, and drying, roasting, activating and the like to obtain the catalyst. (2) The deposition precipitation method introduces a precipitating agent for precipitation on the premise that the active metal component is fully contacted with the carrier of the active metal component, so that the metal active component is precipitated in inner holes or surfaces of the carrier. (3) Chemical vapor deposition processes utilize a vapor phase reaction to introduce the reactive component in gaseous form into a solid support to be deposited at a specified deposition temperature and at a sufficiently high vapor pressureAnd on the body film, the loading and dispersion of the active component are realized. (4) The ion exchange method utilizes exchangeable ions existing on the surface of a carrier to load active components on the carrier through ion exchange to realize the controllable introduction of the active components, and then the catalyst is prepared through washing, drying, roasting and other treatments.
in the preparation process of the supported catalyst, the content of active components by an impregnation method is difficult to control, and when the concentration of an impregnation solution is too low, the supported active components are not uniformly dispersed in pores, the structural stability is poor, and the catalytic performance is unstable; when the concentration of the impregnation solution is too high, ions are easy to agglomerate, the catalytic activity is limited, repeated experiments are needed for searching the optimal appropriate conditions, and time and labor are wasted; and the active components are easy to sinter and lose catalytic activity in the calcining process. In the deposition precipitation method, the loading condition of the active component is difficult to modulate and control, the repeatability is poor, the nucleation process is easier to occur in the solution, and the generated metal particles are larger and have small specific surface area. The chemical vapor deposition method has high requirements on instruments and operation conditions, and the operation process is complicated and difficult to popularize. In the ion exchange method, the interaction between the metal and the carrier is weak, the content of the generated active component is limited, and the application range is small. In conclusion, the traditional method is difficult to realize high dispersion of the active components on the carrier, and the active sites are difficult to regulate. Therefore, it is necessary to develop a preparation method of the catalyst for preparing methanol by carbon dioxide hydrogenation, so as to improve the conversion rate and selectivity of preparing methanol by carbon dioxide.
disclosure of Invention
the invention aims to solve the problems and the defects in the prior art and provides a preparation method of a hollow sphere catalyst for preparing methanol by carbon dioxide hydrogenation without a carrier. The method can utilize the carbon sphere template to form the copper-zinc oxide mixture hollow sphere with uniform shape and size and adjustable particle size, realizes good dispersion of active components by constructing higher internal specific surface area of the active components, enables the catalyst to get rid of the limitation of the existence of a carrier, prevents the active components from agglomeration and inactivation due to a catalytic process, improves the catalytic efficiency and the service life of the catalyst, and remarkably improves the conversion rate and the selectivity of preparing methanol from carbon dioxide.
The invention is realized by the following technical scheme:
The preparation method of the catalyst for preparing the hollow methanol sphere by the carrier-free carbon dioxide hydrogenation comprises the following steps:
(1) weighing sucrose in a beaker, adding deionized water, stirring at room temperature until the sucrose is completely dissolved, transferring the obtained transparent solution to a hydrothermal kettle with a polytetrafluoroethylene lining, sealing, putting the hydrothermal kettle into an oven, and reacting at 160-220 ℃ for 8-24 hours;
(2) centrifuging the suspension obtained by the hydrothermal reaction, washing the obtained insoluble substances with water and ethanol for 3-5 times, and drying in an oven at 80-120 deg.C for 24 hr or more;
(3) putting the insoluble substances obtained in the step (2) into a three-neck flask, adding an ethylene glycol solution for dissolving, adding a precursor into the solution after ultrasonic dispersion is uniform, heating the solution to 100-140 ℃ under reflux, and stirring the solution at a high speed for 8-14h to obtain a precursor suspension of the mixed component catalyst;
(4) centrifugally separating the stirred precursor suspension, washing the obtained product with water and ethanol twice respectively, and drying in an oven at 80-120 ℃ for 24 hours or more;
(5) Roasting the product dried in the step (4) in air at 450-600 ℃ for 3-5 hours;
(6) And (3) placing the product obtained by roasting into a tubular furnace, and reducing for 1-3h in hydrogen flow at the temperature of 200-400 ℃ to obtain the carrier-free carbon dioxide hydrogenation methanol hollow sphere catalyst.
the preparation method further adopts the technical scheme that the precursor is a mixture of copper nitrate and zinc nitrate, and the molar ratio of the copper nitrate to the zinc nitrate is 7: 3-3: 7.
compared with the prior art, the invention has the following beneficial effects:
the catalyst prepared by the method is shot by a scanning electron microscope, has uniform shape and size, and is in a hollow sphere shape with the particle size of about 200-300nmthe obtained high-power transmission electron microscope pictures are further illustrated as hollow spheres, and the BET test method shows that the specific surface area of the hollow spheres is as high as 250m2The result of X-ray diffraction detection shows that the copper and zinc components are uniformly mixed, the obtained catalyst has a good crystal form, and the successful preparation is proved. The activity of the catalyst is tested by using a carbon dioxide hydrogenation reaction, and the result shows that the product selectivity is up to 90 percent, and the methanol yield is 87 percent. The catalyst prepared by the method has the advantages of high recovery rate, high repeatability, simple operation and mass production. The obtained product has high dispersity, the active components are uniformly mixed, the catalytic efficiency of carbon dioxide hydrogenation and the product selectivity are improved, and the purpose of the invention is achieved.
the catalyst prepared by the invention does not need to be supported by a carrier, and has an active component with ultrahigh specific surface area, and the catalyst has larger specific surface area due to the unique hollow sphere structure, so that the active component is not easy to sinter in the calcining process, the catalytic efficiency is obviously improved, and the preparation process is nontoxic and harmless and is simple and convenient to operate.
Detailed Description
The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the above-described subject matter of the present invention to the examples below.