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CN-121972207-A - Platinum-based catalyst for cyclohexane dehydrogenation and preparation process thereof

CN121972207ACN 121972207 ACN121972207 ACN 121972207ACN-121972207-A

Abstract

The invention relates to the technical field of catalysts, and discloses a platinum-based catalyst for cyclohexane dehydrogenation and a preparation process thereof, wherein the invention firstly prepares a titanium dioxide-nitrogen doped graphene composite carrier by a microwave hydrothermal method, and then loading platinum and rhenium metal precursors on a carrier, finally forming platinum-rhenium alloy nano particles under mild conditions by adopting an ultraviolet light assisted chemical reduction method, and then carrying out aftertreatment to obtain the platinum-based catalyst for cyclohexane dehydrogenation. The invention creatively constructs a composite structure with titanium dioxide nano particles as cores, nitrogen doped graphene as shells and platinum-rhenium alloy nano particles positioned at interfaces, and realizes remarkable improvement of catalyst activity, selectivity and stability in cyclohexane dehydrogenation reaction by utilizing the stabilizing effect of the titanium dioxide inner cores, the conduction and anchoring functions of the nitrogen doped graphene shells and the synergistic catalysis effect of the platinum-rhenium alloy. The method is green and safe in process and simple and convenient to operate, and the prepared catalyst has excellent catalytic performance.

Inventors

  • YU JIANQIANG
  • SHI XUEFANG
  • LI LE
  • ZHANG RUI

Assignees

  • 陕西开达化工有限责任公司

Dates

Publication Date
20260505
Application Date
20260409

Claims (9)

  1. 1. The platinum-based catalyst for cyclohexane dehydrogenation is characterized by comprising a titanium dioxide-nitrogen doped graphene composite carrier and a platinum-based active component loaded on the titanium dioxide-nitrogen doped graphene composite carrier; The titanium dioxide-nitrogen doped graphene composite carrier consists of an inner core and an outer shell, wherein the inner core is titanium dioxide nano particles, and the outer shell is a nitrogen doped graphene layer; the platinum-based active component is platinum-rhenium alloy nano particles, and the average particle size is 1-3nm; the platinum-based active component is positioned between the nitrogen-doped graphene outer shell layer and the titanium dioxide inner core.
  2. 2. The platinum-based catalyst for cyclohexane dehydrogenation according to claim 1, wherein the molar ratio of rhenium to platinum in said platinum-rhenium alloy nano-particles is (0.1-0.5): 1.
  3. 3. A process for preparing the platinum-based catalyst for cyclohexane dehydrogenation according to any one of claims 1 to 2, characterized in that the process for preparing the platinum-based catalyst for cyclohexane dehydrogenation comprises the steps of: s1, preparing a composite carrier: dispersing titanium dioxide nano particles in water, adding graphene oxide and a nitrogen source, ultrasonically stirring for 1-2 hours to obtain a mixed solution, adding the mixed solution into a microwave hydrothermal reaction kettle, performing microwave reaction for 2-4 hours at 150-200 ℃, cooling, centrifuging to remove supernatant, and alternately washing and centrifuging with deionized water and absolute ethyl alcohol for 3 times to obtain a titanium dioxide-nitrogen doped graphene composite carrier; s2, loading a metal precursor: adding the titanium dioxide-nitrogen doped graphene composite carrier into ethanol, performing ultrasonic dispersion for 30-60min, adding ammonium perrhenate and chloroplatinic acid, continuing ultrasonic treatment for 30-60min, and then placing the mixture in a dark place at room temperature and stirring for 1-2h to obtain slurry carrying a metal precursor; S3, ultraviolet light assisted chemical reduction: Adding sodium borohydride into the slurry loaded with the metal precursor under the protection of nitrogen atmosphere, heating to 25-60 ℃ in a water bath, and reducing for 2-3 hours under the irradiation of ultraviolet light, so that the platinum precursor chloroplatinic acid and the rhenium precursor ammonium perrhenate are reduced together, and platinum-rhenium alloy nano particles are formed at the interface of the composite carrier, thus obtaining a platinum-based active component; S4, post-processing: and (3) alternately washing the platinum-rhenium alloy nanoparticle platinum-based active component loaded on the titanium dioxide-nitrogen doped graphene composite carrier with deionized water and absolute ethyl alcohol for 3 times, drying, and activating by heat treatment to obtain the platinum-based catalyst for cyclohexane dehydrogenation.
  4. 4. The process for preparing a platinum-based catalyst for cyclohexane dehydrogenation according to claim 3, wherein the nitrogen source in S1 is one of urea, melamine, ammonia, polyaniline and ethylenediamine.
  5. 5. The preparation process of the platinum-based catalyst for cyclohexane dehydrogenation, according to claim 3, wherein the mass ratio of the titanium dioxide nano particles to the water to the graphene oxide to the nitrogen source in the S1 is 10 (800-1200): 15-25): 40-80.
  6. 6. The preparation process of the platinum-based catalyst for cyclohexane dehydrogenation according to claim 3, wherein the mass volume ratio of the titanium dioxide-nitrogen doped graphene composite carrier and ethanol in the S2 is 10 (100-200), the molar ratio of ammonium perrhenate to chloroplatinic acid in the S2 is (0.1-0.5): 1, and the addition amount of the chloroplatinic acid is 0.5-3% of the total mass of the catalyst.
  7. 7. The process for preparing a platinum-based catalyst for cyclohexane dehydrogenation according to claim 3, wherein the addition amount of sodium borohydride in S3 is 2 to 5 times the total molar amount of ammonium perrhenate and chloroplatinic acid.
  8. 8. The process for preparing a platinum-based catalyst for cyclohexane dehydrogenation according to claim 3, wherein the main wavelength of ultraviolet light in S3 is 254nm and the power is 100 to 160W.
  9. 9. The process for preparing a platinum-based catalyst for cyclohexane dehydrogenation according to claim 3, wherein in S4, the heat treatment activation method is to reduce the dried product at 130 ℃ for 2 hours and 300-400 ℃ for 2-5 hours under a hydrogen atmosphere.

Description

Platinum-based catalyst for cyclohexane dehydrogenation and preparation process thereof Technical Field The invention relates to the technical field of catalysts, in particular to a platinum-based catalyst for cyclohexane dehydrogenation and a preparation process thereof. Background Cyclohexane dehydrogenation is an important reaction process for industrially preparing benzene and hydrogen, and is widely applied to the fields of petrochemical industry and fine chemical industry. Benzene is used as a basic chemical raw material and has an irreplaceable position in the industries of synthetic fibers, plastics, rubber, medicines, pesticides and the like. Cyclohexane dehydrogenation is a strong endothermic reaction, and is usually carried out under high temperature conditions, and high requirements are imposed on the activity, selectivity and stability of the catalyst. Currently, cyclohexane dehydrogenation catalysts commonly used in industry are mainly noble metal catalysts, and among them, platinum (Pt) -based catalysts are attracting attention due to their excellent dehydrogenation activity and benzene selectivity. Conventional platinum-based catalysts generally use alumina, silica or activated carbon as a carrier, and carry platinum nanoparticles by an impregnation method. However, the catalyst still has a plurality of problems in practical application, namely, the platinum metal is easy to sinter and migrate at high temperature, so that active sites are reduced, the catalyst is deactivated, the selectivity of the catalyst to benzene still has room for improvement, byproducts such as pyrolysis gas and carbon deposition can influence the purity of a product and the service life of the catalyst, and the dispersity of the platinum in the traditional preparation process is low, the utilization rate is low, and the waste of noble metal resources is caused. There are a number of improvements in the art. Publication number CN111686718B discloses a cyclohexane dehydrogenation catalyst and a preparation method thereof, wherein the catalyst is a metal supported catalyst, and comprises a metal active component and a carrier, the metal active component is Pt, and the carrier is gamma-Al 2O3. The invention increases the steric hindrance of the metal load compound in the impregnating solution by an ammonia complexation mode, and the alkaline condition can further reduce the active metal load rate, prevent the agglomeration of metal particles and improve the dispersibility and uniformity of the active components of the catalyst. However, the traditional alumina (Al 2O3) carrier has higher specific surface area, but the acidic sites on the surface of the carrier are easy to cause side reactions such as cracking, isomerization and the like, so that the selectivity of benzene is affected. Therefore, a platinum-based cyclohexane dehydrogenation catalyst with high activity, high selectivity, good platinum-based active material dispersibility, simple preparation process and reasonable cost is developed, and the catalyst has important industrial significance and application prospect. Disclosure of Invention The technical problems to be solved are as follows: aiming at the defects of the prior art, the invention provides a platinum-based catalyst for cyclohexane dehydrogenation and a preparation process thereof, and solves the problems of low activity, insufficient selectivity, insufficient stability and the like of the traditional catalyst. (II) technical scheme: a platinum-based catalyst for cyclohexane dehydrogenation comprises a titanium dioxide-nitrogen doped graphene composite carrier and a platinum-based active component loaded on the titanium dioxide-nitrogen doped graphene composite carrier. The titanium dioxide-nitrogen doped graphene composite carrier consists of an inner core and an outer shell, wherein the inner core is titanium dioxide nano particles, and the outer shell is a nitrogen doped graphene layer. The platinum-based active component is platinum-rhenium alloy nano particles, and the average particle size is 1-3nm. The platinum-based active component is positioned between the nitrogen-doped graphene outer shell layer and the titanium dioxide inner core. Further, in the platinum-rhenium alloy nanoparticles, the molar ratio of rhenium to platinum is (0.1-0.5): 1. Further, the preparation process of the platinum-based catalyst for cyclohexane dehydrogenation comprises the following steps: s1, preparing a composite carrier: Dispersing titanium dioxide nano particles in water, adding graphene oxide and a nitrogen source, ultrasonically stirring for 1-2 hours to obtain a mixed solution, adding the mixed solution into a microwave hydrothermal reaction kettle, performing microwave reaction for 2-4 hours at 150-200 ℃, cooling, centrifuging to remove supernatant, and alternately washing and centrifuging with deionized water and absolute ethyl alcohol for 3 times to obtain the titanium dioxide-nitrogen doped graphene co