Enzymatic Oxidation of Butane to 2-Butanol in a Bubble Column

Abstract

Unspecific peroxygenases have recently gained significant interest due to their ability to catalyse the hydroxylation of non-activated C−H bonds using only hydrogen peroxide as a co-substrate. However, the development of preparative processes has so far mostly concentrated on benzylic hydroxylations using liquid substrates. Herein, we demonstrate the application of a peroxygenase for the hydroxylation of the inert, gaseous substrate butane to 2-butanol in a bubble column reactor. The influence of hydrogen peroxide feed rate and enzyme loading on product formation, overoxidation to butanone and catalytic efficiency is investigated at 200 mL scale. The process is scaled up to 2 L and coupled with continuous extraction. This setup allowed the production of 115 mmol 2-butanol and 70 mmol butanone with an overall total turnover number (TTN) of over 15.000, thereby demonstrating the applicability of peroxygenases for preparative hydroxylation of such inert, gaseous substrates at mild reaction conditions.