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

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 331m ²/g for Ni-alumina-post) and narrow pore size distributions centered at ca.4nm. Highly dispersed Ni particles were observed in the Ni-alumina catalysts (ca. 5.2nm for Ni-alumina-pre and ca. 6.8nm 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.12.3nm). 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.