Carbonylation of Methanol: A Versatile Reaction

Abstract

Carbonylation reaction has aroused much interest in industry and academia because of the successful industrial applications of homogeneous catalysis in carbonylation of methanol to produce acetic acid. The first iodide-promoted cobalt catalyst, [HCo(CO) 4 ], of BASF was commercialized in 1960, but it required very high pressures (600 bar) as well as high temperature (250 °C), and the selectivity was 90% only. In 1970, Monsanto commercialized a rhodium-based homogeneous liquid-phase catalyst, [Rh(CO) 2 I 2 ] − , which involved a pressure of 30–60 bar and temperatures of 150–200 °C with a high selectivity over 99% based on methanol. Subsequently, in 1996, BP Chemicals developed and commercialized the most efficient Cativa process for the production of acetic acid involving active iridium catalyst [Ir(CO) 2 I 2 ] − along with Ru–complex activator, which could operate at reduced water content (less than 8 wt%), compared to that about 14–15 wt% required by Monsanto normal process, leading to less costly product purification. Iridium-based catalytic carbonylation of methanol is gaining much industrial importance compared to rhodium based one because of several advantages. To develop much improved catalysts and catalysis processes for carbonylation, much efforts are put forward in the laboratory scale process developments based on metal–complex catalysts of functionalized ligands. Development of heterogeneous catalytic process for carbonylation of methanol is also in progress. This chapter focuses on the importance and progress of carbonylation reaction of methanol to produce acetic acid starting from the initial processes to the state-of-the-art technology and also on the progress of laboratory scale processes based on metal-complexes and also rhodium complex-anchored heterogeneous catalysts.