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CN-121990595-A - Modified alumina carrier, metal catalyst, preparation method and application

CN121990595ACN 121990595 ACN121990595 ACN 121990595ACN-121990595-A

Abstract

The invention provides a modified alumina carrier, a metal catalyst, a preparation method and application. The modified alumina carrier is prepared by taking industrial molded alumina in a gamma-Al 2 O 3 crystal form as a base material and carrying out in-situ modification treatment on carbon-containing gaseous micromolecules, wherein the surface of the modified alumina carrier is provided with a reconstructed active site and an electron-rich micro-area environment, the reconstructed active site is formed by breaking Al-O-Al bridging bonds on the surface of the base material, and the Al 2p binding energy in the X-ray photoelectron spectrum of the electron-rich micro-area environment is reduced by 0.2-0.35eV compared with that of unmodified gamma-Al 2 O 3 . The preparation method provided by the invention can be operated simply and conveniently under mild conditions, has low cost and is suitable for industrial mass production requirements.

Inventors

  • FENG JUNTING
  • PAN DENGKE
  • WU XINJUN
  • WANG QIAN
  • LI LING
  • LIU JINQING

Assignees

  • 中国化学工程第七建设有限公司
  • 衢州资源化工创新研究院

Dates

Publication Date
20260508
Application Date
20251230

Claims (10)

  1. 1. The modified alumina carrier is characterized in that gamma-Al 2 O 3 crystal form industrial grade formed alumina is used as a base material, and is prepared through carbon-containing gaseous micromolecule in-situ modification treatment, wherein the surface of the modified alumina carrier is provided with a reconstructed active site and an electron-rich micro-area environment, the reconstructed active site is formed by breaking Al-O-Al bridging bonds on the surface of the base material, and the Al 2p binding energy in the electron-rich micro-area environment is reduced by 0.2-0.35eV compared with unmodified gamma-Al 2 O 3 in X-ray photoelectron spectrum.
  2. 2. The modified-alumina carrier according to claim 1, wherein the modified-alumina carrier has a specific surface area of 200 to 303m 2 /g, a pore volume of 0.3 to 0.8cm 3 /g, and an average pore diameter of 5 to 13nm.
  3. 3. The modified-alumina support of claim 1 or 2, wherein the carbonaceous gaseous small molecules are one or more of CH 4 、C 2 H 2 、C 2 H 4 、CO、CO 2 、C 2 H 6 .
  4. 4. A process for the preparation of the modified-alumina support of any one of claims 1 to 3, comprising the steps of: s1, pretreatment of a carrier: Roasting the gamma-Al 2 O 3 crystal form industrial-grade formed alumina carrier to remove surface organic adhesive and adsorption impurities, thereby obtaining a degummed formed alumina carrier; s2, inert atmosphere replacement: introducing deoxidized protective gas into the reactor to reduce the oxygen content in the reactor to below 50 ppm; s3, in-situ modification reaction: the reaction gas is switched into a mixed gas after deoxidization, the mixed gas consists of carbon-containing gaseous micromolecules X and protective gas, wherein the volume content of X is 10% -80%, and the balance is the protective gas; s4, post-treatment: after the reaction is finished, cooling to room temperature, taking out the sample rapidly and sealing to obtain the molded alumina carrier with reducing capability.
  5. 5. The preparation method of claim 4, wherein in step S1, the gamma-Al 2 O 3 crystal form of the industrial-grade molded alumina carrier is placed in a muffle furnace, heated to 400-600 ℃ at a heating rate of 2-10 ℃ per min in an air atmosphere, and baked for 2-6 hours under heat preservation to remove surface organic adhesives and adsorbed impurities, and naturally cooled to room temperature, so as to obtain the degummed molded alumina carrier.
  6. 6. The method according to claim 5, wherein in step S3, the volume content of X in the mixed gas is 30% -75%.
  7. 7. An apparatus for use in the process of any one of claims 4-6, wherein the apparatus comprises at least one X-gas storage tank, at least one shielding gas storage tank, a mass flow meter set, an oxygen removal device, a reactor, and a tail gas collection vessel; the outlet of the X gas storage tank and the outlet of the protecting gas storage tank are respectively and correspondingly connected to the inlet of the mass flowmeter group, the outlet of the mass flowmeter group is connected with the inlet of the deaerating device, and the outlet of the deaerating device is connected with the air inlet of the reactor; a first pressure gauge is arranged at the air inlet of the reactor, a second pressure gauge is arranged at the air outlet of the reactor, and the bottom of the reactor is connected with a tail gas collecting container; the number of the X gas storage tanks is matched with the number of the carbon-containing gaseous micromolecules used in the preparation process of the modified alumina carrier.
  8. 8. A metal catalyst comprising the modified alumina support of any one of claims 1-3 and an active metal comprising at least one of platinum, gold, silver, ruthenium or palladium, wherein the active metal is present at a loading of 0.1% to 3%.
  9. 9. A method of preparing the metal catalyst of claim 8, wherein the method comprises: Adding the modified alumina carrier according to any one of claims 1-3 into a noble metal precursor solution, carrying out isovolumetric impregnation at room temperature to 85 ℃ for 3-24 hours, wherein the concentration of the noble metal solution is determined according to the content of noble metal required by a final product, and drying the impregnated carrier at 40-90 ℃ for 6-24 hours to obtain the metal catalyst loaded with the highly dispersed noble metal element.
  10. 10. A method for using the metal catalyst for carbon dioxide hydrogenation reaction according to any one of claims 1-3, which is characterized in that the metal catalyst and quartz sand are mixed and filled into a reaction tube, the test temperature is controlled to be 250-550 ℃, the reaction raw material gas consists of CO 2 、H 2 and shielding gas, the volume ratio of H 2 、CO 2 is (3:1) - (4:1), and the reaction is completed after 4-16 time to obtain CO and CH 4 .

Description

Modified alumina carrier, metal catalyst, preparation method and application Technical Field The invention relates to the technical field of catalyst preparation, in particular to a modified alumina carrier, a metal catalyst, a preparation method and application. Background The formed alumina carrier has excellent mechanical strength, excellent thermal stability, flexible and controllable pore canal structure and rich and adjustable surface chemical properties, so that the formed alumina carrier becomes one of the most widely applied catalyst framework materials in the industrial catalysis field, has the market ratio of more than 60% in the core fields of petrochemical hydrofining, fine chemical catalytic synthesis, environmental catalytic pollutant degradation and the like, and plays a vital role in promoting the development of industrial catalytic technology. In industrial catalytic reactions, highly dispersed metal catalysts (including monoatomic catalysts, diatomic catalysts and nanoparticle catalysts) exhibit irreplaceable catalytic performances in many core industrial reactions such as hydrogenation, ammonia synthesis, fischer-tropsch synthesis and the like by virtue of nearly 100% of atomic utilization, unique electronic structures and excellent catalytic selectivity, and are key technical directions for improving catalytic reaction efficiency and reducing industrial production cost. However, the surface chemistry of shaped alumina supports is inert, the number of surface active sites is small and the distribution is not uniform, resulting in the loading and stabilization of active metal species on the support surface facing a great challenge. Currently, the mainstream mode of preparing a high-dispersion metal catalyst by molding an alumina carrier in industry and laboratory generally needs to be performed under severe conditions such as high-temperature roasting, high-temperature reduction and the like, so as to activate inert sites on the surface of the carrier and realize decomposition and loading of a metal precursor. However, the high temperature condition is very easy to cause migration and agglomeration of active metal atoms or nano particles, so that the metal dispersity is greatly reduced, the catalytic activity and stability of the catalyst are seriously weakened, and the application requirement of industrial catalysis on the high-dispersion metal catalyst is difficult to meet. To solve the above problems, a great deal of research has been conducted by researchers and industry. For example, patent CN 105772008B discloses a heavy oil hydroprocessing catalyst comprising a titanium-containing shaped alumina carrier, a metal component molybdenum and a metal component cobalt or nickel, wherein the titanium content of the titanium-containing shaped alumina carrier is 0.5-8 wt% based on the oxide and based on the total weight of the titanium-containing shaped alumina carrier, the metal component molybdenum content of the catalyst is 4.8 μmol/m 2-9.0μmol/m2 and the metal component cobalt or nickel content is 1.5 μmol/m 2-4.0μmol/m2 based on the oxide and based on the unit carrier surface loading, and no MoO 3 characteristic peak occurs at diffraction angle 2θ=26++2 ° when the catalyst is characterized by XRD. According to the scheme, titanium element with the mass fraction of 0.5-8% is introduced into an alumina precursor, and after the processes of molding, high-temperature roasting and the like, the number and the distribution of active sites on the surface of the carrier are optimized, so that the dispersed load of active metals such as molybdenum, cobalt, nickel and the like on the surface of the carrier is realized. The patent CN 114249300A discloses a method for improving the reaction performance and energy efficiency of preparing synthesis gas by using plasma and a catalyst with a specific microstructure through coupling, wherein methane and carbon dioxide are used as raw materials, ni/Al 2O3 is used as a catalyst, the reaction is carried out in a plasma reactor, the synthesis gas is prepared under a mild condition, and Al 2O3 is the mixture of one or more of nano-sheet Al 2O3, feather-shaped Al 2O3, spherical Al 2O3 and rod-shaped Al 2O3 with different microstructures. The carriers with different structures directly influence the dispersion, stability and discharge capacitance of Ni particles, thereby influencing the Ni/Al 2O3 catalytic performance under mild conditions. According to the scheme, a hydrothermal synthesis combined forming treatment process is adopted to prepare an alumina carrier with special morphology such as nano-sheet, feather, spherical flower or rod, and the like, five-coordination Al 3+ rich on the surface of the carrier is used as an active metal anchoring site, and a subsequent reduction process is combined to realize high dispersion of Ni particles. Although the technology has a breakthrough in improving the metal dispersibility, the technology has the obvious defec