Preparation of Mesoporous Ni–alumina Catalyst by One-step Sol–gel Method: Control of Textural Properties and Catalytic Application to the Hydrodechlorination of o-dichlorobenzene

Abstract

Mesoporous Ni–alumina catalysts (Ni–alumina-pre and Ni–alumina-post) were synthesized by one-step sol–gel method using micelle complex comprising lauric acid and nickel ion as a template with metal source and using aluminum sec-butoxide as an aluminum source. The Ni–alumina catalysts showed relatively high surface areas (303 m2/g for Ni–alumina-pre and 331 m2/g for Ni–alumina-post) and narrow pore size distributions centered at ca. 4 nm. Highly dispersed Ni particles were observed in the Ni–alumina catalysts (ca. 5.2 nm for Ni–alumina-pre and ca. 6.8 nm for Ni–alumina-post) after reduction at 550 °C, while a catalyst prepared without a template (NiAl-comp) exhibited inferior porosity with large metal particles (ca. 12.3 nm). Mesoporous Ni–alumina catalysts with different porosity were obtained by employing different hydrolysis step of aluminum source. When aluminum source was hydrolyzed under the presence of micelle complex, a supported Ni catalyst with highly developed framework mesoporosity was obtained (Ni–alumina-post). On the other hand, when aluminum source was pre-hydrolyzed followed by mixing with micelle solution, the resulting catalyst (Ni–alumina-pre) retained high portion of textural porosity. It was revealed that the hydrolysis method employed in this research affected not only textural properties but also metal-support interaction in the Ni–alumina catalysts. It was also found that the Ni–alumina-pre catalyst exhibited weaker interaction between nickel and alumina than the Ni–alumina-post, leading to higher degree of reduction in the Ni–alumina-pre catalyst. In the hydrodechlorination of o-dichlorobenzene, the Ni–alumina catalysts exhibited better catalytic performance than the NiAl-comp catalyst, which was attributed to higher metal dispersion in the Ni–alumina catalysts. In particular, the Ni–alumina-pre catalyst showing 1.5 times higher degree of reduction and larger amounts of o-dichlorobenzene adsorption exhibited better catalytic performance than the Ni–alumina-post catalyst.