嵌于纳米ZSM-5沸石表面孔口的金属磷化物簇（NixPy/MoxPy)的结构及其加氢性能研究

Transition metal phosphides have been widely used in the fundamental research in the field of the hydrofining due to their high intrinsic hydrotreating activity. However, the lower dispersion of the phosphide phases on SiO2 support reduced their total activity. Especially, the phosphide active phases are easily aggregated, and phosphorus loss occurs during the reaction process, which greatly hinders their application in industry. In this study, we combine the confinement effect of the micropore mouth on metal clusters and the unique surface properties of the zeolite to embed the metal phosphide clusters (MxPy, M=Ni or Mo) at the surface openings of the nanosized ZSM-5 zeolite crystals for preparation of highly dispersed, highly stable metal phosphides catalysts. The structure of the MxPy clusters is deeply studied. The interaction between the MxPy clusters and zeolite framework is clarified. The relationship of the catalytic activity and stability with the structure of the MxPy active phase is investigated through combining the catalytic activity in the hydrogenation of dibenzothiophene and methylbenzene and the characterization results of the catalysts. It is expected that these studies would provide a new knowledge for understanding the correlation between the structure of the active phase and stabilities for metal phosphides catalyst, which provide a new strategy for preparation of highly active and highly stable metal phosphides catalysts.

过渡金属磷化物催化剂具有非常高的本征加氢活性，人们在加氢精制领域对其性能进行了广泛的研究。但是，磷化物活性相在SiO2载体上的分散性较差导致其表观活性不高，特别是反应过程中发生积聚以及磷物种流失问题，导致其仍然没有走向商业化。本项目利用沸石的微孔孔口对组装的金属簇具有空间限制作用以及沸石独特的表面化学性质可以加强金属与沸石表面相互作用的特点，将极小的金属磷化物簇（MxPy，M=Ni or Mo）嵌于纳米ZSM-5晶粒表面开放的孔口，实现高分散、高稳定的金属磷化物簇催化剂的制备。深入研究这种极小的磷化物簇的组成结构，以及它们与沸石骨架的相互作用本质；以二苯并噻吩和甲苯的加氢为模型反应，研究其活性、稳定性与活性相结构的关系。期望这些研究能够为理解金属磷化物催化剂的活性相结构及其稳定性提供新的认识，为制备高活性、高稳定性金属磷化物催化剂提供一个新的策略。

过渡金属磷化物催化剂，特别是 Ni2P 和 MoP，具有非常高的本征加氢活性，人们对其在加氢精制反应中的性能进行了广泛的研究，希望其能成为第二代加氢精制催化剂。但是，由于磷化物活性相在SiO2载体上的分散性较差导致其表观活性不高，特别是反应过程中发生积聚以及磷物种流失的问题，限制其在工业中的实际应用。为此，本项目利用纳米ZSM-5沸石独特的表面性质、微-介孔结构及阴离子骨架特性，制备了高分散、高稳定的金属磷化镍（钼）簇催化剂。研究发现所制备的金属磷化镍和磷化钼簇是Ni2P和MoP相。纳米沸石独特的表面酸性羟基可以加强金属镍（钼）物种与沸石相互作用，沸石微孔孔口对组装的金属磷化物簇具有空间限制作用及沸石骨架与嵌在微孔孔口的Ni2P和MoP簇发生强相互作用并发生电子相互转移，沸石的高外表面积及开放的微-介孔孔道进一步有利于活性相的分散。活性结果显示所制备Ni2P簇催化剂在小分子苯乙炔加氢反应中的本征加氢性能（反应速率robs=1.5 mol∙kg-1∙s-1）远高于SiO2担载的Ni2P催化剂（robs=0.4 mol∙kg-1∙s-1）；而且得到的MoP催化剂在多环芳烃菲的加氢反应中具有良好的反应稳定性，而且本征加氢活性（robs=3.4 mol∙kg-1∙s-1）也高于SiO2担载的Ni2P催化剂（robs=2.3 mol∙kg-1∙s-1）。期望这些研究能够为制备高活性、高稳定性金属磷化物催化剂提供一个新的策略。