Key engineering innovations in industrial-scale cyclohexanone production via cyclohexene esterification–reduction

Abstract

Conventional industrial technologies for cyclohexanone production, a key precursor to ε-caprolactam, primarily cyclohexane oxidation (CHA-Ox) and cyclohexene hydration (CHE-Hydr), are constrained by an inherent trade-off between conversion and selectivity. This leads to low carbon atom utilization or high energy intensity, together with substantial environmental burdens. The cyclohexene esterification–reduction (CHE-ER) route, first proposed by the Research Institute of Petroleum Processing (RIPP), delivers exceptional conversion and selectivity and therefore offers a promising platform for next-generation cyclohexanone production. However, the central challenge has been to translate the intrinsic advantages of this chemistry into a process that is simultaneously economically competitive and environmentally sustainable. Here we report a set of critical chemical engineering innovations that streamline process design and substantially reduce energy consumption. By leveraging the inertness of cyclohexane during cyclohexene esterification, we designed a new extraction system that selectively separates benzene from its partial hydrogenation products. We further implemented a hybrid reactor configuration integrating a fixed-bed reactor with a catalytic reactive distillation reactor for cyclohexene esterification with acetic acid. In addition, we identified and strategically harnessed the beneficial roles of cyclohexane in facilitating reaction heat dissipation and excess acetic acid separation. These innovations have been successfully deployed in a 400 kt yr–1-capacity industrial plant for cyclohexanone production via the CHE-ER route, affording nearly complete cyclohexene conversion and cyclohexyl acetate selectivity above 99.0%. This work establishes a new-generation of industrial technology for cyclohexanone production that maximizes economic benefit, while minimizes energy demand and environmental impacts associated with conventional processes.