새로운 형상 선택적 촉매로서의 나노세공 니켈포스페이트

초록

Research involving open-framework transition metal phosphates has steadily increased following the discovery of AlPO’s, based primarily on the possibility of preparing porous materials with novel properties not seen in traditional aluminosilicate zeolites. Particularly promising are transition metal phosphates, where novel catalytic, spectroscopic, magnetic, and electronic properties are possible. While a host of such structures have been characterized, the nanoporous nickel phosphates VSB-1 and VSB-5 are rare in exhibiting genuine zeolitic properties such as high BET surface areas, ion exchange, and shape-selective catalysis. Both structures are based on 3D networks of octahedrally coordinated nickel atoms containing large, uni-dimensional channels. Sorption, neutron scattering, and temperature desorption experiments all point toward the existence of unsaturated Ni2+ sites in VSB-5 that strongly interact with H2. Such sites are unique in the field of porous materials and stem from the unusual surface chemistry of VSB-5’s pores, which possess coordinatively unsaturated Ni2+ sites accessible in the pores. Catalytic results on selective hydrogenation of olefin, as well as characterization of a modified form of VSB-5 produced by high-temperature H2 reduction, strongly suggest that the water molecule bound to a Ni2+ in the cavity is at least partially removed during calcination.