Effect of water and methanol in the production of methyl methacrylate over iron phosphate catalysts

Abstract

This work discusses two production routes to methyl methacrylate (MMA) over an iron phosphate catalyst, namely oxidative dehydrogenation of methyl isobutyrate (MIB) and isobutyric acid (IBA) with methanol as co-feed. In situ studies show that at 400 °C, a mixture of the iron tridymite and quartz like phases are present under air, H2 and N2. The catalyst was tested in a fixed bed stainless steel reactor. The feed was passed over the catalyst with air and methanol; and air, water and methanol. The effects of the water to feed ratio and methanol to feed ratio were studied in terms of maximum conversion, yield and selectivity to MMA. Using methyl isobutyrate as a feed and methanol as a co-feed, the best yield of methylmethacrylate obtained was 40%. This corresponds to a selectivity of 73%, at a conversion of 55%. Feeding isobutyric acid and methanol over the iron phosphate catalyst gave an optimum yield of 15% methyl methacrylate at 400 °C. The yield of the products increased with increasing methanol/IBA ratio due to methanol limiting the hydrolysis reactions. The results obtained in this study show that MMA can be formed by the oxidative dehydrogenation–esterification of IBA and methanol over the iron phosphate catalyst.