Highly selective synthesis of 2-cyclopentylidenecyclopentanone via cyclopentanone self-condensation over MgAl-LDO(NO3−)

Abstract

Cyclopentanone self-condensation to 2-cyclopentylidenecyclopentanone is one of the key steps in synthesizing high-density fuels. In this study, MgAl-LDO(NO₃⁻) catalysts, prepared via coprecipitation, demonstrated good catalytic performance. Meanwhile, Mg₂Al-LDO(NO₃⁻) catalysts with different Mg/Al ratios were explored. Characterization by XRD, NH₃-TPD and CO₂-TPD revealed that Mg₂Al-LDO(NO₃⁻) possessed appropriate acid–base active sites, correlating with its enhanced catalytic performance. Under optimized reaction conditions, cyclopentanone conversion reached 85.9% with 98.8% selectivity toward 2-cyclopentylidenecyclopentanone. Furthermore, the reusability of the catalyst was investigated. XRD, SEM, and N₂ adsorption–desorption analyses indicated that structural changes in the Mg₂Al-LDO(NO₃⁻) catalyst led to its deactivation. GC-MS analysis of the reaction system identified the primary by-product as 2,5-dicyclopentylidenecyclopentanone. Based on these findings, a plausible reaction network is proposed.