One‐Step Room‐Temperature Synthesis of [Al]MCM‐41 Materials for the Catalytic Conversion of Phenylglyoxal to Ethylmandelate

Abstract Mesoporous [Al]MCM‐41 materials with n Si / n Al ratios of 15 to 50 suitable for the direct catalytic conversion of phenylglyoxal to ethylmandelate have been successfully synthesized at room temperature within 1 h. The surface areas and pore sizes of the obtained [Al]MCM‐41 materials are in the ranges of 1005–1246 m 2 g −1 and 3.44–3.99 nm, respectively, for the different n Si / n Al ratios. For all [Al]MCM‐41 catalysts, most of the Al species were tetrahedrally coordinated with Si in the next coordination sphere of atoms. 1 H and 13 C magic‐angle spinning NMR spectroscopic investigations indicated that the acid strength of the SiOH groups on these [Al]MCM‐41 catalysts and the density of these surface sites are enhanced with increasing Al content in the synthesis gels. These surface sites with enhanced acid strength were found to be catalytically active sites for phenylglyoxal conversion. The [Al]MCM‐41 material with n Si / n Al =15 showed the highest phenylglyoxal conversion (93.4 %) and selectivity to ethylmandelate (96.9 %), whereas the [Al]MCM‐41 material with n Si / n Al =50 reached the highest turnover frequency (TOF=99.3 h −1 ). This is a much better catalytic performance than that of a dealuminated zeolite Y (TOF=1.7 h −1 ) used as a reference catalyst, which is explained by lower reactant transport limitations in mesoporous materials than that in the microporous zeolite.