Well ordered two-dimensional mesoporous CeSBA-15 synthesized with improved hydrothermal stability and catalytic activity

Abstract

Mesoporous CeSBA-15 catalysts with a variety of n Si/ n Ce ratios have been synthesized under pH-adjusting direct hydrothermal (pH-aDH) method using cerium (IV) sulphate tetrahydrate and Pluronic P123 as the sources of cerium and template, respectively. For comparison studies, Ce/SBA-15(10) catalyst has been synthesized by an incipient wetness impregnation (IWI) method. The hydrothermal stabilities of CeSBA-15 catalysts have been investigated in boiling water (373 K) at autogenous pressure for 168 h. The mesoporous CeSBA-15 catalysts synthesized by different methods have been characterized using the relevant techniques viz. ICP-AES, XRD, N 2 adsorption, UV–vis DRS, EPR, 29Si MAS NMR, TEM and FE-SEM, and their characteristic results show that the CeSBA-15 catalysts synthesized by pH-aDH method have higher tetrahedral cerium-ions with two-dimensional mesostructures than the Ce/SBA-15(10) synthesized by IWI method. In addition, CeSBA-15(10) has higher hydrothermal stability than CeSBA-15(50). The CeSBA-15 catalysts have been tested in the liquid phase oxidation of cyclohexane with hydrogen peroxide (H 2O 2). Based on the catalytic activities of all catalysts, CeSBA-15(10) is found to be a highly active, recycle and promising heterogeneous catalyst for the oxidation of cyclohexane.