Evaluation of Different Process Concepts for the Indirect Hydration of Cyclohexene to Cyclohexanol

An indirect hydration process route for the production of cyclohexanol was proposed by Steyer et al., which uses formic acid as a reactive entrainer (Steyer, F.; Freund, H.; Sundmacher, K. Ind. Eng. Chem. Res. 2008, 47, 9581-9587; Steyer, F.; Sundmacher, K. Ind. Eng. Chem. Res. 2007, 46, 1099-1104). This route overcomes several limitations of the conventional Asahi process for cyclohexene hydration to cyclohexanol (Steyer, F.; Sundmacher, K. Ind. Eng.,Chem. Res. 2007, 46, 1099-1104; Mitsui, O.; Fukuoka, Y. Process for producing cyclic alcohol. U.S. Patent 4,588,846, 1986; Ishida, H. Catal. Sure. Jpn. 1997, 1, 241-246; Ishida, H.; Fukuoka, Y.; Mitsui, O.; Mono, M. Liquid-Phase Hydration of Cyclohexane with Highly Silicious Zeolities. In Zeolites and Microporous Crystals: Proceedings of the International Symposium on Zeolites and Microporous Crystals, Nagoya, August 22-25, 1993; Hattori, T., Yashima, T., Eds.; Studies in Surface Science and Catalysis, Vol. 83; Elsevier: Tokyo, NY, 1994; pp 473-480). A coupled-column reactive distillation process concept, developed earlier in our group (Kumar, R.; Katariya, A.; Freund, H.; Sundmacher, K. Org. Process Res. Dee. 2011, 15, 527-529; Katariya, A.; Freund, H.; Sundmacher, K. Ind. Eng. Chem. Res, 2009, 48, 9534-9545; Freund, H.; Katariya, A.; Kumar, R.; Steyer, F.; Sundmacher, K. DGMK Tagungsber. 2007, 2, 237-239), is feasible, but the energy consumption is very high, and the process concept is limited by multiple steady states with a narrow operating window. There is a need to develop other promising process options. In this direction the present work analyses different process concepts and discusses in detail the challenges involved. Various process options were developed and analyzed. Dedicated experiments were carried out in order to ensure the validity of the kinetic model at a wide range of process conditions. Long-time batch experiments provided an accurate estimation of the heat of formation of cyclohexylformate. The developed process concepts are compared and evaluated with respect to the benchmark Asahi process. As an important indicator of the economic viability, the energy consumption is analyzed.