Hydrotalcite-loaded nanometer platinum catalyst as well as preparation method and application thereof

Abstract

The invention provides hydrotalcite-loaded nanometer platinum catalyst as well as a preparation method and application thereof. The preparation method of the hydrotalcite-loaded nanometer platinum catalyst comprises the following steps of: preparing magnesium-aluminum hydrotalcite crystal nucleus by utilizing an all-return liquid mixing membrane reactor, dispersing the crystal nucleus in an aqueous solution; adding an chloroplatinic acid aqueous solution and tetradecyl trimethyl ammonium bromide (TTAB) as well as a proper proportion reducing agent of NaBH4; controlling the reducing velocity and the growth of Pt nanometer particles by utilizing the protecting and stabilizing effect of the TTAB to the Pt<4+> ion; and gradually crystallizing the hydrotalcite while reducing the Pt<4+> ion to obtain the hydrotalcite-loaded nanometer platinum catalyst. The catalyst is obtained by loading nanometer particles on a hydrotalcite carrier, wherein the chemical formula of the hydrotalcite is as follows: MgxAly(OH)16CO3 nH2O; the platinum nanometer particle dimension is 2 nm-8nm; the nanometer particles are polyhedral or ellipsoidal in appearance; the loading capacity of the platinum is 0.5%-3%; and the dispersion degree on the carrier is 20%-50%. The hydrotalcite-loaded nanometer platinum catalyst can be used for catalytic hydrogenation reaction of unsaturated aldehyde (cinnamyl aldehyde), wherein water is used as solvent, the conversation rate of the reactant cinnamyl aldehyde is 75%-95% and the selectivity of the product cinnamyl alcohol is 75%-95%.

Description

technical field [0001] The invention belongs to the field of metal nano-catalyst preparation, and in particular relates to a supported platinum catalyst and a preparation method thereof, as well as using it as an unsaturated aldehyde hydrogenation catalyst. Background technique [0002] Platinum metal catalysts have been found to be better hydrogenation reaction catalysts, showing high activity in various organic molecule hydrogenation reactions, such as: hydrogenation of unsaturated aldehyde / ketone molecules, ester hydrogenation, nitro reduction, etc. . The main factors affecting the catalytic performance of platinum metal catalysts are: metal particle size, support type and metal-support interaction [Urbano, F.J.; Hidalgo-Carrillo, J.; Aramendia, M.A.; Marinas, A.; Marinas, J.M., Appl . Catal. A-Gen 2010, 385, 190-200.]. The methods for preparing supported platinum catalysts currently reported in the literature mainly include: impregnation method and reduction method. T...

AI Technical Summary

Problems solved by technology

Reducing agents with strong reducing ability, such as sodium borohydride, hydrazine, etc., can reduce metal ions from their solutions in a very short time, but because the reduction speed is too fast, the obtained metal particle size distribution is wide; while mild Reducing agents, such as reducing sugars, polyols, ascorbic acid, etc., can slow down the reduction rate and control the growth of metal particles, but they often require higher temperatures, take longer, and consume more energy [Z.Guo, Y .Chen,L.Li,X.Wang,G.L.Haller,Y.Yang.J.Catal.2010,276,314-326.]

In addition, for supported metal catalysts, the current method usually separates the support preparation from the metal loading process [Bhogeswararao, S.; Srinivas, D. Intramolecular J. Catal. 2012, 285, 31-40; J.Zhu, Y. Jia, M.Li, M.Lu, J.Zhu.Ind.Eng.Chem.Res.2013,52,1224-1233.], that is, the carrier is prepared first and then the metal particles are loaded, or the carrier and the Metal nanoparticles, and then mixed in the solution for metal loading, this preparation process makes the binding force between the metal particles and the carrier poor, easy to migrate and aggregate, thus affecting the catalytic reactivity and stability

Images