Single-step preparation of Ni catalysts supported on mesoporous silicas (SBA-15 and SBA-16) and the effect of pore structure on the selective hydrodechlorination of 1,1,2-trichloroethane to VCM

A nickel catalyst supported on mesoporous silica was synthesized using a single-step sol-gel scheme with a triblock copolymer as the structure-directing agent. The role of the surfactant is to organize the silica into the highly ordered 2D hexagonal and 3D cubic structure, via an ionic assembly pathway. The addition of Ni²⁺ ions to the solution results in a strong interaction between the head group (polyethylene oxide, PEO), Ni²⁺ ions, and the silica precursors (tetraethoxysilane, TEOS). PEO is exposed to hydrophilic conditions in acidic media, and consequently combines with nickel ions by electrostatic force. Thus, the nickel particles are located on the surface of the mesostrucutre, within the mesoporous and outer surface. After calcination, the catalysts had a small and regular size metal dispersion with a well-defined cylindrical pore structure and a narrow pore size distribution, as evidenced by XRD, TEM, N₂ adsorption, ICP-AES, and EXAFS. Using the SBA-16 type support with 3D cage like, mesopore structure and a high micropore ratio, the hydrodechlorination of 1,1,2-trichloroethane was found to be relatively efficient. Moreover, high VCM selectivity could be obtained on nickel catalysts prepared via the single-step method.