Direct oxidation of ethane to acetic acid

The homogeneous carbonylation of methanol to acetic acid uses CH3I/HI as a co-catalyst, which requires significant environmental treatment and separation stages. In contrast, direct oxidation of ethane to acetic acid over a heterogeneous catalyst, first established in a SABIC pilot plant in Saudi Arabia in 2003, is a viable alternative to the traditional route without the environmental impact or the need for separations; however, significant levels of by-products have limited its commercialisation. The SABIC catalyst is a complex Mo-V-Ln-Nb-Pd system and determining the function of each component is a significant challenge. Surprisingly, few in situ investigations on this system have been performed; however, the application of both Raman spectroscopy and X-ray absorption fine structure (XAFS) could result in a clearer understanding of the role of each component. In turn, this understanding should lead to advances in catalyst design, improving selectivity to acetic acid. In addition, differences in reactor design will be assessed by applying these in situ techniques to investigate changes in the catalyst with time on stream when using fixed and fluidised-bed reactors, the latter having been shown to be advantageous for the direct oxidation of ethane.