Alpha-hydroxy methylisobutyrate (a-MOB) and beta-methoxy methylisobutyrate (b-MEMOB) can account for up to 50% of distillation bottoms in a conventional ACH-route to methyl methacrylate (MMA). While a-MOB and b-MEMOB can be isolated with high yield via fractional distillation, there is no commercial process available for converting such stream into high value products such as MMA or methacrylic acid (MAA). In this work, we successfully demonstrate that the majority of the distillation bottoms, including a-MOB and b-MEMOB, can be recovered as higher value chemicals such as MMA/MAA via additional separation combined with catalytic process. The motivation of this study is to identify a catalyst system that can convert both a-MOB and b-MEMOB in the distillate to MMA/MAA effectively. In this report, we review and evaluate different promising approaches based on prior art, and identify the most appropriate catalytic system among a series of acid and base catalysts, in terms of the nature of catalyst active sites. Both acid and base sites can dehydrate a-MOB and demethanolate b-MEMOB. However, catalysts with strong or medium-strong acid sites should be avoided due to serious side reactions such as a-MOB decomposition and methanol etherification over the acid sites. NaX zeolite catalyst with acid-base pairs works well for a-MOB dehydration, but has low selectivity for b-MEMOB demethanolation. Catalysts with strong base sites such as Cs2O/SiO2 give the most leveraged conversion of a-MOB and b-MEMOB with high selectivity to MMA/MAA. Overall, strong base catalyst has shown the greatest promise to convert both a-MOB and b-MEMOB effectively to MMA/MAA while avoiding unwanted side reactions.

Identification of suitable active sites for simultaneous conversion of alpha-MOB and beta-MEMOB into MMA and MAA

254th National Meeting (2017)

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