Carbon supported core-shell structure nano metal catalyst as well as preparation method and application thereof

Abstract

The invention provides a carbon supported core-shell structure nano metal catalyst as well as a preparation method and application thereof. The carbon supported metal catalyst with the core-shell structure is obtained by compounding layered double-metal hydroxides containing cobalt and nickel and beta-cyclodextrin and self-reducing the compound in situ at a high temperature by means of the reducibility of generating carbon at the high temperature of the beta-cyclodextrin; the carbon supported metal catalyst with the core-shell structure can be expressed as M / ZnO-Al2O3 / C; and the core of the carbon supported metal catalyst is formed by nano metal M (M is Co or Ni), and the shell of the catalyst is formed by ZnO and little amorphous Al2O3; amorphous carbon serves as the catalyst carrier; the grain sizes of the core-shell structure nanoparticles are distributed in the range of 15-40 nm; and the specific surface area of the catalyst is 150-350 m<2> / g. The carbon supported metal catalyst is applied to hydrogenation reaction of citronellal and shows excellent activity; and the carbon supported metal catalyst has high selectivity for the product citronellal.

Description

technical field [0001] The invention relates to the technical field of catalyst preparation, in particular to a preparation method of a carbon-loaded core-shell structure nano-metal catalyst. The catalyst is used for the selective catalytic hydrogenation of citronellal. technical background [0002] Layered double hydroxides (LDHs), whose molecular formula is [M 2+ (1-x) m 3+ x (OH) 2 ] x+ (A x / n ) n- .mH 2 O, is an anionic clay material with a typical layered structure. Due to its composition M 2+ ,M 3+ As well as the size controllability, it has important applications in the field of catalysis. Using LDHs as substrates to prepare highly dispersed catalysts combined with other materials has been widely used in various organic catalysis fields. With the development of science and technology, carbon materials have touched all walks of life. Since carbon materials have high specific surface area and good thermal and mechanical properties, loading catalysts on carb...

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Problems solved by technology

Nano-transition metal catalysts are easily oxidized in air and difficult to preserve in air. In Journal of Molecular Catalysis A:Chemical, 280 (2008) 52-60, Kamal Kouachi et al. prepared cobalt-based different carrier catalysts by impregnation method. It is clearly stated in the literature of hydrocitral that this type of catalyst is easily oxidized and deactivated, so hydrogen must be used for pre-reduction before the hydrogenation reaction starts, thus resulting in a complex operation process and increased requirements for equipment; in Applied Catalysis A: General, 232 (2002) 147-158, Evandro Luís Linhari Rodrigues et al. use impregnation method to SiO 2 Prepare Co / SiO as a carrier 2 Catalyst, due to the property that Co is easily oxidized in the air, can only be used for meteorological hydrogenation, and it needs to be reduced with a large amount of high-pressure hydrogen, which increases the cost of the catalyst

Co / Al was synthesized by Chie Ando et al. in Applied Catalysis A: General, 185 (1999) L181–L183 2 o 3 Catalyst, and hydrogenation reaction to a variety of unsaturated aldehydes with different structures. It can be seen from the results that the conversion rate and selectivity of the reaction fluctuate one after another, and the ideal effect cannot be achieved at the same time.

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