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CN-121988375-A - Metal modified molecular sieve @ SiO2Catalyst, preparation method and application thereof

CN121988375ACN 121988375 ACN121988375 ACN 121988375ACN-121988375-A

Abstract

The invention provides a metal modified molecular sieve@SiO 2 catalyst and a preparation method and application thereof, belonging to the technical field of catalytic conversion of CO 2 and light alkane. According to the invention, the metal modified molecular sieve is subjected to H 2 reduction-oxidation pretreatment and silanization treatment in sequence, the fine regulation and control of the chemical state of a metal active center are realized through H 2 reduction-oxidation pretreatment, and then the SiO 2 coating layer is utilized to physically fix the active center and regulate the acidity of the outer surface, so that the cracking side reaction is effectively inhibited, the aromatization selectivity is improved, and the metal active center can be obviously stabilized under the synergistic effect of the two, so that the catalyst has excellent carbon deposition resistance and long-acting stability when applied to CO 2 and low-carbon alkane aromatization.

Inventors

  • BAI BING
  • GUO YUYU
  • BAI HUI
  • HUANG WEI

Assignees

  • 太原理工大学

Dates

Publication Date
20260508
Application Date
20260327

Claims (10)

  1. 1. The preparation method of the metal modified molecular sieve@SiO 2 catalyst is characterized by comprising the following steps of: loading a metal source on a molecular sieve by adopting an ion exchange method or an impregnation method, and then roasting to obtain a metal modified molecular sieve; Carrying out reduction treatment on the metal modified molecular sieve in a hydrogen-containing atmosphere, and then carrying out oxidation treatment in an oxygen-containing atmosphere to obtain a pretreated metal modified molecular sieve; And mixing the pretreated metal modified molecular sieve with a silanization reagent and an organic solvent, performing silanization treatment by adopting a chemical liquid phase deposition method, and sequentially drying and roasting the obtained product to obtain the metal modified molecular sieve@SiO 2 catalyst.
  2. 2. The preparation method of claim 1, wherein the metal source comprises one or more of Zn, ga, cu, fe, cr, mo, sn, pt and Pd, the molecular sieve comprises one or more of HZSM-5, HZSM-11, HZSM-12, HZSM-35 and HZSM-48, the loading amount of the metal element on the metal modified molecular sieve is 0.1-10wt%, and the roasting treatment temperature is 500-600 ℃ for 3-6 h.
  3. 3. The preparation method according to claim 1, wherein the hydrogen-containing atmosphere has a volume fraction of H 2 -20% and the balance N 2 or Ar, and the reduction treatment is performed at a temperature of 500-650 ℃ for a time of 0.5-3H.
  4. 4. The preparation method of the oxygen-containing gas, according to claim 1, wherein the volume fraction of O 2 -30% in the oxygen-containing atmosphere is N 2 or Ar, the temperature of the oxidation treatment is 500-650 ℃ and the time is 0.5-3 h.
  5. 5. The preparation method according to claim 1, wherein the silylating agent comprises one or more of ethyl orthosilicate, isopropyl silicate, hexadecyltrimethoxysilane and methyltrimethoxysilane, and the organic solvent comprises at least one of n-hexane, cyclohexane and ethanol.
  6. 6. The preparation method according to claim 1 or 5, wherein the mass ratio of the silylating agent to the pretreated metal-modified molecular sieve is 1:3 to 3:1.
  7. 7. The preparation method of the metal modified molecular sieve catalyst according to claim 1, wherein the temperature of the silanization treatment is 60-80 ℃ and the time is 2-8 hours, and the mass of the SiO 2 coated after the silanization treatment is 0.01-20% of that of the metal modified molecular sieve catalyst @ SiO 2 .
  8. 8. The method according to claim 1, wherein the drying temperature is 100-120 ℃, the baking temperature is 500-600 ℃ and the time is 4-6 hours, and the atmosphere comprises air, nitrogen or inert atmosphere.
  9. 9. The metal modified molecular sieve@SiO 2 catalyst prepared by the preparation method of any one of claims 1-8.
  10. 10. The use of the metal modified molecular sieve @ SiO 2 catalyst of claim 9 in the CO-conversion of light alkanes with CO 2 to produce aromatics.

Description

Metal modified molecular sieve@SiO 2 catalyst and preparation method and application thereof Technical Field The invention relates to the technical field of catalytic conversion of CO 2 and light alkane, in particular to a metal modified molecular sieve@SiO 2 catalyst and a preparation method and application thereof. Background With the large-scale development of shale gas, the yield of light alkane (C 2~C5) represented by ethane is greatly increased, and a rich raw material basis is provided for the high-valued conversion and utilization of the shale gas. Meanwhile, carbon dioxide (CO 2) is a major greenhouse gas, and its recycling is receiving attention. The CO-conversion of light alkane and CO 2 can not only utilize CO 2 as a weak oxidant or CO-reactant to promote the activation and dehydrogenation of alkane, but also directly convert CO 2 into valuable chemicals, thus being a potential green process route. The aromatization reaction is an important process route for converting light alkane into aromatic hydrocarbon with high added value (such as benzene, toluene and xylene), and has wide application in the fields of petrochemical industry and coal chemical industry. Molecular sieve catalysts, particularly metal modified ZSM-5 molecular sieves, are widely used in research and industrial practice for aromatization reactions due to their suitable acidity and pore structure. The dehydrogenation activity and the aromatic hydrocarbon selectivity of the catalyst can be obviously improved by introducing metal components (such as Ga, zn, pt and the like), and the catalytic performance is directly influenced by the existence state of metal species and the synergistic effect of the metal species and the acidic sites of the molecular sieve. However, the existing metal modified molecular sieve catalyst still has the following technical problems in practical application that firstly, the chemical state of a metal active center is difficult to accurately regulate and control. In the catalyst prepared by the conventional impregnation or ion exchange method, metal species exist in the form of agglomerated oxides, and part of the metal species are positioned on the outer surface of the molecular sieve, so that migration, agglomeration or loss easily occurs in the reaction process, the stability of an active center is poor, and the catalytic efficiency is reduced. Secondly, strong acid sites existing on the outer surface of the molecular sieve are easy to cause side reactions such as nonselective cracking, excessive hydrogen transfer and the like, so that the aromatization selectivity is reduced, the carbon deposition generation is accelerated, and the catalyst is deactivated rapidly. In addition, deposition and attack of carbon deposition precursors on the catalyst surface further exacerbate stability problems, limiting the industrial application life of the catalyst. In order to solve the above problems, researchers try to regulate the dispersion state of metal species and the surface properties of catalysts by pretreatment or surface modification, but the existing methods often have difficulty in combining stabilization of active centers and precise modulation of acidity of external surfaces, and have complex process and poor universality. Therefore, the development of the preparation method of the catalyst, which can simultaneously realize the fine regulation and control of the chemical state of the metal active center, the stable immobilization of the active center and the effective modification of the acidity of the outer surface, has important significance for improving the comprehensive performance of the aromatization catalyst. Disclosure of Invention The invention aims to provide a metal modified molecular sieve@SiO 2 catalyst, a preparation method and application thereof, which can obtain an aromatization catalyst with high activity, high selectivity and long-acting stability and solve the problems of low selectivity of light alkane and CO 2 CO-conversion into aromatic hydrocarbon and reduced catalyst stability caused by deposition of carbon deposition precursors. In order to achieve the above object, the present invention provides the following technical solutions: The invention provides a preparation method of a metal modified molecular sieve@SiO 2 catalyst, which comprises the following steps: loading a metal source on a molecular sieve by adopting an ion exchange method or an impregnation method, and then roasting to obtain a metal modified molecular sieve; Carrying out reduction treatment on the metal modified molecular sieve in a hydrogen-containing atmosphere, and then carrying out oxidation treatment in an oxygen-containing atmosphere to obtain a pretreated metal modified molecular sieve; And mixing the pretreated metal modified molecular sieve with a silanization reagent and an organic solvent, performing silanization treatment by adopting a chemical liquid phase deposition method, and sequentially dry