Zeolite Catalysts for Green Production of Caprolactam

Abstract

Caprolactam is an important petrochemical platform molecule that has been widely used to prepare nylon-6 and other polyamide engineering plastics. Compared with traditional routes in caprolactam synthesis with environmentally unfriendly wastes, a recent green route involves benzene semihydrogenation, cyclohexene hydration, cyclohexanol dehydrogenation, cyclohexanone ammoximation, and Beckmann rearrangement. In most of these reactions, zeolite catalysts have displayed crucial roles, for example, ZSM-5 zeolite for hydration, TS-1 zeolite for ammoximation, and S-1 zeolite for Beckmann rearrangement. In this Review, these processes and the catalytic performances of different zeolite catalysts are summarized, and the significant advantages of zeolites compared with the previous homogeneous catalysts and general supported catalysts are mentioned. In addition, the structure–performance interplay of these zeolites was particularly discussed, which is expected to guide the development of more efficient zeolite catalysts with optimized structures in the future.

Electrocatalytic Synthesis of Nylon‐6 Precursor at Almost 100 % Yield

“…Multiple serious explosion incidents in the industrial CPL production are mainly due to the explosive decomposition of NH 2 OH [8] . Meanwhile, the growing demand for CPL promotes the expansion of CPL production capacity (by 8.9 million tons per year) [1b, 9] . Therefore, it is imperative to develop a new direct CPL synthesis from NO x and CYC, to improve the safety of the CPL synthesis by avoiding the direct use of NH 2 OH.…”

Modulating the Microenvironment of Silanols in Pure-Silicon Zeolites for Boosting Vapor-phase Beckmann Rearrangement of Cyclohexanone Oxime

“…ε-Caprolactam (CPL) is an important organic chemical intermediate to produce Nylon-6 fiber and corresponding polyamide engineering plastics, which are widely applied in textile, automobile, and electronic industries. − The world CPL capacity mounted to 9 million tons in 2022, over 95% of which were produced via a liquid-phase Beckmann rearrangement (BR) process promoted by oleum catalysts. , Drawbacks of such a liquid-phase process, including large amounts of low-value ammonium sulfate byproducts as well as ecological and safety problems, severely violate the criteria of green chemistry. , To overcome these problems, vapor-phase BR based on solid acid catalysts had been developed, which ensure complete green CPL production owing to its theoretically 100% atom utilization efficiency and no ammonium sulfate generation. − …”

Editorial for the Festschrift Honoring the Legacy of Babatunde A. Ogunnaike (1956–2022)

“…The reaction engineering area is well represented by the contributions of Cohen et al, who present an analysis of catalytic parallel pathways and selectivity using a modified energy span, 13 Conrad et al, who provide insights into the homogeneous thermal oligomerization of ethylene to fuels, 14 and Wang et al, who discuss zeolite catalysts for green production of caprolactam. 15 The work of Fromer et al lies at the intersection of process and reaction engineering, reporting on methods for identifying stoichiometric models for complex reaction mixtures. 16 Likewise, the contribution of Ekici et al covers optimization modeling of advanced reactors for syngas to olefin conversion.…”

“…The reaction engineering area is well represented by the contributions of Cohen et al, who present an analysis of catalytic parallel pathways and selectivity using a modified energy span, Conrad et al, who provide insights into the homogeneous thermal oligomerization of ethylene to fuels, and Wang et al, who discuss zeolite catalysts for green production of caprolactam …”