Published March 2003
This review examines the technology represented by recent patents in gas phase Beckmann rearrangement of cyclohexanone oxime to caprolactam. The contribution aims to solve the longstanding issue in caprolactam processes of eliminating byproduct salts. The issue is relevant because of a recent process development joint venture between Sumitomo (for the oxime rearrangement step) and Enichem (for oxime production). The conclusion of this review finds that both steps, as illustrated by the corresponding patents, do not appear to be competitive with current best practices. However, both processes were evaluated directly along the lines of the patents, with limited information on process optimization. As a result, the potential for process improvements appears to be significant. Thus, optimization of process parameters and improvements in process technology may eventually lead to cost competitive technology. The discussion illustrates several factors that represent significant potential contributions to the economic feasibility of the technology.
Of the issues discussed, the use of hydrogen peroxide in the oxime production appears to be the main factor affecting the oxime cost. As a result, the Enichem contribution to the joint venture would appear to require modifications to the chemistry, if the design in PEP Report 7C is valid. The design in this review indicates that even with the most economical oxime source, the process in this review is not viable without modification. Fortunately, a number of potential factors are available for process improvement and optimization, to reduce both capital and operating costs. Hence the conclusion that there are significant potential opportunities for improvement that may result in a cost competitive process. However, successful implementations of such improvements are unknown, at least publicly.