Load type metal mesoporous molecular sieve noble metal catalyst and preparation method thereof

Abstract

The invention relates to a load type metal mesoporous molecular sieve noble metal catalyst and a preparation method thereof. The preparation method comprises serving a complex which is formed by long-chain surfactant molecules and a metal complex as a template agent, producing a metal platinum doped molecular sieve Pt-MCM-41 by a hydrothermal crystallization method after a silicon source is added and uniformly fixing metal platinum in molecular sieve frame lattices in the process; washing and drying a sample after crystallization and directly reducing the sample in the hydrogen; removing the residual surfactant through low temperature after-treatment to obtain a required sample. According to the load type metal mesoporous molecular sieve noble metal catalyst and the preparation method thereof, the prepared catalyst comprises a regular mesoporous structure, active site centers are distributed in a highly ordered mode, the specific surface area and the pore volume are large, the thermal and hydrothermal stability is good, and the catalyst can serve as a catalytic oxidation, catalytic cracking and catalytic isomerization catalyst.

Description

technical field [0001] The invention relates to a supported mesoporous molecular sieve noble metal catalyst and a preparation method thereof, in particular to a catalyst in which metallic platinum is highly ordered and dispersed in a mesoporous molecular sieve MCM-41 matrix and a preparation method thereof. Background technique [0002] In 1992, Mobil scientists invented the M41S series of mesoporous molecular sieves, which expanded the application range of molecular sieve materials in the field of macromolecular catalysis. MCM-41 mesoporous molecular sieve has the characteristics of regular channels arranged in hexagonal arrangement, large specific surface area, large pore volume, uniformly distributed pore size, and adjustable components, but its skeleton has fewer defects and weak catalytic active centers, which greatly limits a major obstacle to its catalytic applications. With the further maturity of the synthesis method of mesoporous molecular sieves, increasing the a...

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Problems solved by technology

The impregnation method is simple and easy to operate, but there are also some disadvantages: during the drying stage of the impregnation solution, with the evaporation of water, due to the solvation effect and the influence of the surface tension of the impregnation solution, the metal active components tend to aggregate and deposit on the carrier. surface, the subsequent calcination, activation and other processes are also difficult to destroy this highly aggregated form; the impregnated active metal species are only supported on the surface of the carrier and cannot form a strong interaction with the carrier. High temperature calcination is likely to cause the migration of metal particles, Aggregation to form large metal grains directly affects the dispersion of catalyst active components, as well as catalytic performance and repeatability of use

The results show that the metal Ni particles of the catalyst prepared by the chemical grafting method are highly dispersed on the surface of the support, and its size is significantly smaller than that obtained by the traditional impregnation method, and it shows good catalytic activity for carbon dioxide methanation, but the HRTEM It shows that the size of the metal particles is not uniform and the method is limited to the limited number of hydroxyl groups on the surface of the carrier, which is more suitable for the preparation of low-concentration active component catalysts

[0005] With the development of molecular sieves and the improvement of the performance requirements of catalytic materials in the field of catalysis, if the metal particles can be highly dispersed inside the carrier and tend to be ordered or regularly distributed, the catalyst will exert greater catalytic activity. This topic Group (Microporous and Mesoporous Materials, 2014, 185, 130-136) prepared a highly ordered dispersed catalyst Ni / MCM-41 loaded with transition metal nickel by lattice positioning method, using CTAB as template agent, divalent nickel ions Incorporated into the MCM-41 skeleton during the synthesis process with ammonia, the sample after hydrothermal crystallization was calcined to remove the template agent, and this was used as the precursor to obtain the product through hydrogen reduction, in which the metal nickel particles were less than 20nm, and the distribution showed a certain law Compared with the traditional impregnation method, it has higher catalytic activity, but for the introduction of noble metals, due to the different properties of metal salts or acids, this synthesis process has certain limitations

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