阅读说明：本技术 一种丙烷脱氢催化剂及其制备方法 (Propane dehydrogenation catalyst and preparation method thereof ) 是由 石磊 文静 张昌武 于 2019-12-09 设计创作，主要内容包括：本发明公开一种丙烷脱氢制丙烯催化剂及其制备方法,丙烷脱氢制丙烯催化剂为负载型,活性相为磷和硅修饰的铂金属纳米簇,载体为纳米纤维状γ-Al<Sub>2</Sub>O<Sub>3</Sub>,磷与铂形成合金。本发明还公开了所述催化剂的制备方法,包括模板导向合成纳米纤维状γ-Al<Sub>2</Sub>O<Sub>3</Sub>,在其表面担载铂和磷前驱,经焙烧和还原后进一步包覆多孔硅。本发明获得的催化剂用于丙烷脱氢反应,同步提升了铂催化剂的反应活性、稳定性以及抗积碳性能。本发明使用了储量丰富的磷和硅元素,相比于金属助剂在成本和经济性上有优势。(The invention discloses a catalyst for preparing propylene by propane dehydrogenation and a preparation method thereof 2 O 3 Phosphorus is alloyed with platinum. The invention also discloses a preparation method of the catalyst, which comprises the step of synthesizing nano fibrous gamma-Al in a template-oriented way 2 O 3 Platinum and phosphorus precursors are loaded on the surface of the porous silicon, and the porous silicon is further coated after roasting and reduction. The catalyst obtained by the invention is used for propane dehydrogenation reaction, and the reaction activity, stability and anti-carbon deposition performance of the platinum catalyst are synchronously improved. The invention uses phosphorus and silicon elements with abundant reserves, and has advantages in cost and economy compared with metal additives.)

1. A catalyst for preparing propylene by propane dehydrogenation is characterized in that: comprises a carrier, an active component and an auxiliary agent, wherein the carrier is gamma-Al₂O₃The active component is a platinum metal nano cluster, the auxiliary agent comprises phosphorus, and the phosphorus and platinum form an alloy.

2. The catalyst for propane dehydrogenation to produce propylene according to claim 1, wherein: the mass percentage of platinum in the catalyst for preparing propylene by propane dehydrogenation is 0.1-0.8%, and the mass percentage of phosphorus is 0.01-0.4%.

3. The catalyst for propane dehydrogenation to produce propylene according to claim 1, wherein: the auxiliary agent also comprises silicon, the mass percentage of platinum in the catalyst for preparing propylene by propane dehydrogenation is 0.1-0.8%, the mass percentage of phosphorus is 0.01-0.4%, and the mass percentage of silicon is 0.1-0.8%.

4. A method for producing a catalyst for propane dehydrogenation to produce propylene according to claim 1, characterized in that: the method comprises the following steps:

s1 mixing inorganic aluminum salt, urea, structure directing agent and water, hydrothermal treating, drying and roasting to obtain gamma-Al₂O₃A nanofiber carrier;

s2 mixing Pt precursor, P precursor and solvent, and immersing in gamma-Al₂O₃Standing and drying the surface of the nanofiber carrier at room temperature to obtain powder; and roasting and reducing the powder to obtain the phosphorus modified platinum catalyst.

5. The method for producing a catalyst for producing propylene by dehydrogenation of propane according to claim 4, wherein: the structure directing agent in S1 is an amino-containing structure directing agent, the molar ratio of the structure directing agent to the inorganic aluminum salt is 0-2: 1, the molar ratio of urea to the inorganic aluminum salt is 1-10: 1, and the molar concentration of the inorganic aluminum salt is 0.01-1.0 mol/L.

6. The method for producing a catalyst for producing propylene by dehydrogenation of propane according to claim 4, wherein: s1, the hydrothermal temperature is 100-200 ℃, the hydrothermal time is 12-48 h, and the roasting temperature is 400-800 ℃.

7. The method for producing a catalyst for producing propylene by dehydrogenation of propane according to claim 4, wherein: in S2, the platinum precursor is chloroplatinic acid, the phosphorus precursor is phosphoric acid, the solvent is ethanol, the concentration of the chloroplatinic acid is 0.005 g/mL-0.04 g/mL, and the concentration of the phosphoric acid is 0.0005 g/mL-0.0024 g/mL.

8. The method for producing a catalyst for producing propylene by dehydrogenation of propane according to claim 4, wherein: and S3, dispersing the phosphorus-modified platinum catalyst into an aqueous solution containing a surfactant, dropwise adding an organic silicon source and coating porous silicon, aging, filtering and drying to obtain powder, and roasting and reducing the powder to obtain the phosphorus-and-silicon-modified platinum catalyst precursor powder.

9. The method for producing a catalyst for producing propylene by dehydrogenation of propane according to claim 8, wherein: in S3, the surfactant is cetyl ammonium bromide, the organic silicon source is ethyl orthosilicate, the molar ratio of the organic silicon source to the surfactant is 1: 0.1-1, the reaction temperature is 20-50 ℃, and the reaction time is 2-20 hours.

10. The catalyst according to any one of claims 1 to 3, applied to a reaction for producing propylene by propane dehydrogenation, is characterized in that: the reaction is carried out in a differential fixed bed reactor, the reaction temperature is 500-650 ℃, and the reaction pressure is 0-0.2 Mpa.

Technical Field

The invention relates to the technical field of chemical catalysis, in particular to a propane dehydrogenation catalyst and a preparation method thereof.

Background

Propylene is an important basic organic chemical raw material, and downstream products of the propylene comprise a series of chemicals such as polypropylene, propylene oxide, acrylic acid, acrylonitrile and the like which are closely related to human production and life. At present, the industrial production of propylene mainly comes from an oil-based steam cracking process, a catalytic cracking process or a coal-based methanol-to-olefin process. Compared with the traditional route, the propane catalytic dehydrogenation process has the advantages of special propylene production, simple flow and low investment cost, develops an important way for increasing the propylene production in industry, and can effectively relieve the excessive dependence of propylene raw materials in China on petroleum resources.

In the propane dehydrogenation process, the supported platinum catalyst is the system with the most excellent performance and the most extensive use, however, under the harsh working condition, the problem of platinum catalyst deactivation caused by carbon deposition and sintering is still the difficult problem to be solved in the field. Further doping with a metal promoter rich in lone pair electrons, such as tin, is an important means for improving the reactivity and stability of the platinum catalyst in industry. However, such metal promoters usually partially cover active sites, and lose reaction activity while improving selectivity and stability of the platinum catalyst, and more seriously, the metal promoters are easily segregated to the surface under working conditions, and are easily reduced and volatilized to cause permanent inactivation of the catalyst, so that the cost is high. Therefore, further development of novel inexpensive auxiliary agents, and simultaneous improvement of the reactivity and stability of platinum catalysts is still an urgent need in this field.

Disclosure of Invention

The invention aims to replace the metal auxiliary agent used in the existing propane dehydrogenation platinum catalyst, and provides a catalyst for preparing propylene by propane dehydrogenation and a preparation method thereof, which can synchronously improve the reactivity, stability, carbon deposit resistance and economic applicability of the platinum catalyst in the preparation of propylene by propane dehydrogenation.

The technical scheme of the invention is as follows:

the catalyst for preparing propylene by propane dehydrogenation comprises a carrier, an active component and an auxiliary agent, wherein the carrier is gamma-Al₂O₃The active component is a platinum metal nano cluster, the auxiliary agent comprises phosphorus, and the phosphorus and platinum form an alloy.

Preferably, the mass percent of platinum in the catalyst for preparing propylene by propane dehydrogenation is 0.1-0.8%, and the mass percent of phosphorus is 0.01-0.4%.

The preferable auxiliary agent also comprises silicon, the mass percentage of platinum in the catalyst for preparing propylene by propane dehydrogenation is 0.1-0.8%, the mass percentage of phosphorus is 0.01-0.4%, and the mass percentage of silicon is 0.1-0.8%.

The invention also provides a preparation method of the catalyst for preparing propylene by propane dehydrogenation, which comprises the following steps:

s1 mixing inorganic aluminum salt, urea, a structure directing agent and water, carrying out hydrothermal treatment for 12-48 hours, and roasting at 400-800 ℃ to obtain gamma-Al₂O₃A nanofiber carrier;

s2 mixing Pt precursor, P precursor and solvent, and immersing in gamma-Al₂O₃Standing and drying the surface of the nanofiber carrier at room temperature to obtain powder; and roasting and reducing the powder to obtain the phosphorus modified platinum catalyst (the propylene catalyst prepared by propane dehydrogenation).

Preferably, the structure directing agent in S1 is an amino-containing structure directing agent, such as triethylamine, and the molar ratio of the inorganic aluminum salt, urea and the structure directing agent is 1: 1-10: 0-2.

Preferably, the hydrothermal temperature of S1 is 100-200 ℃, the hydrothermal time is 12-48 h, and the roasting temperature is 400-800 ℃.

Preferably, the platinum precursor in S2 is chloroplatinic acid, the phosphorus precursor is phosphoric acid, the solvent is ethanol, the concentration of the chloroplatinic acid is 0.005 g/mL-0.04 g/mL, and the concentration of the phosphoric acid is 0.0005 g/mL-0.0024 g/mL.

Preferably, the preparation method of the catalyst for propylene preparation by propane dehydrogenation further comprises S3, dispersing the catalyst of phosphorus-modified platinum into an aqueous solution containing a surfactant, adding an organic silicon source dropwise and coating porous silicon, aging, filtering and drying to obtain powder, and roasting and reducing the powder to obtain the catalyst precursor powder of phosphorus-and silicon-modified platinum (the catalyst for propylene preparation by propane dehydrogenation).

Preferably, in the steps S2 and S3, the roasting temperature is 400-800 ℃, the roasting time is 1-6 hours, and the reduction conditions are as follows: introduction of H₂/N₂Mixed gas of H₂The volume fraction is 5-100%, the temperature is 400-800 ℃, and the reduction time is 0.5-3 h

Preferably, in S3, the surfactant is hexadecylammonium bromide, the organic silicon source is ethyl orthosilicate, the molar ratio of the organic silicon source to the surfactant is 1: 0.1-1, the reaction temperature is 20-50 ℃, and the reaction time is 2-20 hours.

The invention has the beneficial effect that the catalyst prepared by the method is applied toThe propane dehydrogenation improves the stability of the catalyst and reduces the generation of carbon deposition on the basis of improving the reaction activity and the propylene selectivity of the catalyst, and has good application prospect. The platinum catalyst co-modified by phosphorus and silicon is optimal in terms of activity, selectivity, stability and anti-carbon deposition performance. The invention adopts the gamma-Al prepared by the multi-amino template induction₂O₃The nanofiber effectively disperses platinum to exist in a form of low-dimensional nanocluster, phosphorus with directional covalent bonding characteristic and platinum form alloy on the secondary surface, the d-electron property of the platinum is modulated, and high activity and selectivity are shown in the propane dehydrogenation reaction; the affinity performance of phosphorus and platinum inhibits carbon deposition, the secondary surface bonding also effectively enhances the interaction between the platinum cluster and the surface of the carrier, and the reaction stability of the platinum catalyst is improved; meanwhile, the porous silicon coating layer not only effectively inhibits the growth of platinum clusters and the migration of a phosphorus additive to a carrier, but also occupies carbon deposition sites on the surface of the catalyst, and shows good carbon deposition resistance. In addition, the phosphorus and the silicon used in the invention are elements with relatively rich reserves in the earth crust, and have great advantages in cost and economy compared with metal additives such as tin, gallium, indium and the like.

Drawings

FIG. 1 shows Al prepared in example 1 of the present invention₂O₃Transmission electron microscope photograph of the nanofibers.

FIG. 2 shows PtPSi/Al of example 4 of the present invention₂O₃High resolution transmission electron micrographs of the catalyst.

FIG. 3 shows PtPSi/Al of example 4 of the present invention₂O₃And (4) correcting the spherical aberration of the catalyst by scanning a transmission electron microscope.

FIG. 4 shows PtPSi/Al of example 4 of the present invention₂O₃STEM-EDX elemental profile of the catalyst.

FIG. 5 shows PtPSi/Al of example 4 of the present invention₂O₃Catalyst and comparative example 1Pt/Al₂O₃Comparative results of propane conversion.

FIG. 6 shows PtPSi/Al of example 4 of the present invention₂O₃Catalyst and comparative example 1Pt/Al₂O₃Comparison of propylene SelectivityAnd (6) obtaining the result.

FIG. 7 shows PtPSi/Al of example 4 of the present invention₂O₃Catalyst and comparative example 1Pt/Al₂O₃And (5) carbon deposition analysis results.

Detailed Description

The present invention will be described in detail below with reference to specific examples, but the present invention is not limited to the following examples.