Oxidative dehydrogenation of ethylbenzene over CMK-1 and CMK-3 carbon replicas with various mesopore architectures

Abstract

Nanoreplication strategy was used for the synthesis of mesoporous ordered carbon materials with various pore architectures and surface compositions. Two different silica templates (regular MCM-48 and hexagonal SBA-15) were filled with a carbon precursor – poly(furfuryl alcohol) or sucrose – by the precipitation polycondensation or incipient wetness impregnation, respectively. Furthermore, the resulting carbon precursor/silica composites were carbonized at various temperatures from the range of 650–1050 °C. It was shown that the carbon precursor and method of its deposition strongly influenced structural and textural parameters of the final carbon material determined by XRD, low-temperature N2 adsorption and TEM. The specific surface area of the sucrose-based CMK-3 was ca. 45% higher than the poly(furfuryl alcohol)-derived replicas. On the other hand, this effect was not observed for CMK-1 replicas. The carbonization temperatures tuned up the content of C=O moieties on the surface of carbon replica calculated based on temperature-programmed desorption (TPD) profiles. Obviously, the concentration of C=O functionalities was correlated to the catalytic activity in the oxidative dehydrogenation of ethylbenzene (EB) to styrene. Nevertheless, the CMK-1 replicas were more sensitive to the C=O concentration in terms of EB conversion. Hence, we discussed carefully the role of the pore geometry in the catalytic performance of the studied carbon materials. For the CMK-1 and CMK-3 carbon replicas with comparable chemical and textural properties, but different pore structure, the initial EB conversion varied considerably, reaching 34.2% and 21.6%, respectively, at 350 °C and EB/O2 ratio = 1.0.