Highly efficient and clean synthesis of verbenone over well ordered two-dimensional mesoporous chromium silicate catalysts

Two-dimensional mesoporous SBA-15 catalysts synthesized by different hydrothermal methods have been used, for the first time, in the liquid-phase oxidation of α-pinene with t-butyl hydrogen peroxide (TBHP) for the synthesis of verbenone (VO). The recyclable CrSBA-15 catalysts have also been reused in this reaction to find their catalytic activities. To investigate the leaching of chromium species on the silica surface, CrSBA-15(8) has been treated with ammonium acetate solution, and it has been also treated with boiling water for the investigation of hydrothermal stability. The treated CrSBA-15(8) catalyst has been used in the catalytic reaction for finding the effects of catalytic stability. The influences of various reaction parameters such as temperature, time, ratios of reactant (α-pinene-to-TBHP) have been extensively investigated for the synthesis of VO. In addition, the liquid-phase oxidation of α-pinene has been conducted with different solvents to find the best solvent with a good catalytic activity. On the basis of all investigations with a hypothetical reaction pathway of α-pinene oxidation, the CrSBA-15(8) catalyst is found to be a highly active, recyclable and promising heterogeneous catalyst in the liquid-phase oxidation of α-pinene for highly selective synthesis of VO. Furthermore, CrSBA-15(8) catalyst has higher selectivity of VO (88.2%) than other CrSBA-15 and CrMCM-41.