Immobilization of small metal oxide particles on a solid support by impregnation with solutions of metal salts is a common route of catalyst preparation. Here we explore a modification of this route, based on eutectic freezing of the aqueous precursor salts in the pores of SBA-15, and removal of water/ice by freeze-drying. The two-solvents method was used to selectively fill the pore space of SBA-15 with precursor salts (nickel acetate or nitrate). A morphological and structural analysis of the nickel oxide formed in the pores after thermal decomposition of the salts was performed and compared to samples obtained via conventional solvent evaporation. Immobilized NiO nanocrystallites prepared via eutectic freezing appeared in two morphologies: (a) rodlike particles of ca 5 nm diameter, i.e., somewhat smaller than the pore diameter of SBA-15 (7 nm); (b) species detectable by powder XRD and energy-dispersive X-ray spectroscopy (EDXS), but not by TEM. Nitrogen adsorption isotherms are sensitive to the distribution of NiO in the pores: Pore blocking effects appear in the desorption branch for samples containing rodlike NiO particles, but not in samples in which no particles are detectable by TEM.

通过用金属盐溶液浸渍将小的金属氧化物颗粒固定在固体载体上是催化剂制备的常见途径。在这里，我们基于SBA-15孔中的水性前体盐的共晶冷冻，以及通过冷冻干燥除去水/冰，探索了该途径的改进方法。两种溶剂法用于用前体盐（乙酸镍或硝酸镍）选择性填充SBA-15的孔空间。对盐热分解后在孔中形成的氧化镍进行了形态和结构分析，并将其与通过常规溶剂蒸发获得的样品进行了比较。通过共晶冷冻制备的固定化NiO纳米微晶以两种形态出现：（a）直径约5 nm，即略小于SBA-15（7 nm）孔径的棒状颗粒；（b）可通过粉末XRD和能量色散X射线光谱法（EDXS）检测到的物种，但不能通过TEM检测。氮吸附等温线对孔中NiO的分布很敏感：对于包含棒状NiO颗粒的样品，解吸分支中会出现毛孔阻塞效应，而在TEM中无法检测到颗粒的样品中则不会出现。