Supported metal catalyst with synergistic sites, a preparation method therefor and an application thereof
The present invention provides a preparation method of a supported metal catalyst with synergistic sites. The method is to utilize the unsaturated cubane-like structure, M cation with catalytic activity is introduced into the cluster core unit. By using the vertex vacancy as the capturing center, and adjusting the impregnation temperature to maximize the loading of the cluster precursor, Depending on the electrostatic adsorption of the support and the confinement of the cluster structural unit, the number of S vacancies and the distance between S vacancies and Miso sites are effectively controlled through liquid phase reduction and atmosphere treatment at room temperature to obtain supported X3MSx/Al2O3 catalyst with Miso-Vs synergistic sites. The method of the present invention achieves the joint enhancement of the activity, product selectivity, and stability of unsaturated carbon oxygen bond selective hydrogenation, carbon chlorine bond selective hydrogenation dechlorination, and carbon hydrogen bond dehydrogenation reactions.
1 . A preparation method of a supported metal catalyst with synergistic sites, characterized in that the preparation method comprises the following steps:
A. Mix a soluble metal M salt solution uniformly with a solution of [X3S4(H2O)y]Clz cluster compound to obtain a [X3MS4(H2O)y+1]z+ solution;
B. Disperse Al2O3 support uniformly into the solution obtained in step A, stir at the temperature of 25-60° C. and the rotation speed of 200~500 rpm for 2-6 h until it becomes sticky, and dry it in a constant temperature drying oven at 40~80° C. for 8-24 h to obtain [X3MS4(H2O)y+1]z+/Al2O3 solid powder;
C. Add 1.5 g solid powder obtained in step B into 5-30 mL of deionized water, add excessive soluble reducing agent to reduce M2+/M3+ to metal M, wherein the molar ratio of the reducing agent to the M salt is 3:1~7:1, stir for 18~60 min to obtain black suspension, centrifugally wash it to neutrality, and dry it in a constant temperature drying oven at 60° C. for 8-16 h to obtain X3MS4/Al2O3;
D. Place the X3MS4/Al2O3 obtained in step C into an atmosphere furnace, and heat it to 300~600° C. at a rate of 5-20° C./min for 0.25-6 h of treatment to obtain X3MSx/Al2O3 catalyst (0<x<4);
The corresponding treatment atmosphere is one of air, 10 vol. % O2/N2, 5-40 vol. % H2/N2 or 5-40 vol. % CO/N2; The corresponding X3MSx/Al2O3 catalyst possesses Miso-Vs synergistic sites;
Wherein,
the corresponding [X3S4(H2O)y]Clz in step A is a trinuclear transition metal-sulfur cluster compound with an unsaturated cubane structure, wherein X is one of Mo, W, Re and Ir; y=9; when X is Re (+3), z=1; when X is one of W, Mo and Ir(+4), z=4.
2 . A preparation method of a supported catalyst with synergistic sites according to claim 1 , characterized in that the corresponding soluble metal M salt in step A is one of Na2PdCl4, Pd(NO3)2, Pd(C5H7O2)2, H2PtCl6, Pt(NO3)2, CoCl2, Ni(NO3)2·6H2O, NiCl2, RuCl3, Ga(NO3)3, Fe(NO3)3·9H2O, CuCl2·2H2O, Cu(NO3)2 and AgNO3.
3 . A preparation method of a supported catalyst with synergistic sites according to claim 1 , characterized in that the molar ratio of M to X3 in step A is 4~25/l, and the concentration of the M salt is 0.0035~0.0171 mol/L.
4 . A preparation method of a supported catalyst with synergistic sites according to claim 1 , characterized in that the theoretical loading of the soluble metal M salt in step B is 0.03~5.00 wt. % of the catalyst; the corresponding Al2O3 support possesses rich pore structure while the crystalline phases is γ or δ, the specific surface area is 70~190 m2/g, the pore volume is 0.3~1.3 cm3/g, and the pore size is 15~30 nm; the soluble reducing agent in step C is one of NaBH4, LiBH4, ascorbic acid or oxalic acid.