Highly selective synthesis of vitamin K3 over mesostructured titanium catalysts

Abstract

Mesoporous TiSBA-15 catalysts have been synthesized using Pluronic P123 as a structuring agent under pH-adjusting direct hydrothermal (pH-aDH) method. The mesoporous TiSBA-15 catalysts characterized by sophisticated instrumental techniques via. ICP-AES, XRD, N2 adsorption, FE-SEM, TEM, UV-vis DRS and 29Si MAS NMR show their two-dimensional mesostructures with tetrahedral titanium on the silica surface. The highly ordered TiSBA-15 catalysts have been used in the liquid-phase oxidation of 2-methyl-1-naphthol (2M1N-OH) with hydrogen peroxide (H2O2, 30%), for the synthesis of vitamin K3 (2-methyl-1,4-naphthoquinone). The recyclable TiSBA-15 catalysts have also been reused to find their catalytic activities. The influences of various reaction parameters such as temperature, time, ratios of reactant (2M1N-OH: H2O2) have been then investigated in this catalytic reaction for the highly selective synthesis of vitamin K 3. In addition, the liquid-phase oxidation of 2M1N-OH has been carried out with different solvents to find the best solvent with a good catalytic activity. Based on the all catalytic studies, TiSBA-15(6) catalyst is found to be a highly active and eco-friendly heterogeneous catalyst for the selective synthesis of vitamin K3. Furthermore, TiSBA-15(6) catalyst has higher 2M1N-OH conversion (100%) and vitamin K3 selectivity (93.2%) than other TiSBA-15 and TiMCM-41(40). © 2010 Elsevier B.V.