Natural marble powder-modified SBA-15 as an efficient catalyst for the selective production of 2-methyl-2-pentenal from n-propanal self-aldol condensation.

In this study, conversion of n-propanal to produce 2-methyl-2-pentenal (C6 compound, a fuel range precursor) was carried out using AMW-SBA-15 catalyst synthesized from activated marble waste (AMW) consisting mainly of Ca²⁺ and Mg²⁺ ions. AMW-SBA-15 catalysts with different weight ratios of AMW/Si (6, 12, and 18 wt. %) were prepared using single step sol-gel method. The catalytic activities were examined using a fixed bed continuous reactor over temperature ranging from 350−425 °C under atmospheric pressure. The 12AMW-SBA-15 catalysts showed superior catalytic performance with n-propanal conversion of 75 % and C-6 compound selectivity of 81 % at 375 °C without the need of deactivation for 12 h. To elucidate the structure-activity relationship, all catalysts were characterized using a variety of techniques. The superior performance of 12AMW-SBA-15 was ascribed to the high surface area and smaller particle size as well as the high hydrophobicity, which controlled the hydration of Ca²⁺/Mg²⁺ ions during the reaction. [ABSTRACT FROM AUTHOR]