Bifunctional Solid Catalyst

A bifunctional nanoparticulate catalyst mediates direct conversion of ethanol to isobutene, researchers at Pacific Northwest National Laboratory and Washington State University report (J. Am. Chem. Soc., DOI: 10.1021/ja204235v). The study may lead to low-cost methods for converting biomass-derived ethanol in high yield to an intermediate used for synthesizing fuels, chemicals, and other industrial products. Today’s supplies of isobutene are generally made by catalytic or steam cracking of petroleum feedstocks. Bioethanol could serve as an alternative nonfossil feedstock by conversion to acetone via catalysts with base functionality and then using acidic zeolite catalysts to convert acetone to isobutene. PNNL’s Junming Sun, Yong Wang, and coworkers sought to mediate that transformation directly by using a single catalyst endowed with the right balance of acid and base character. They prepared a series of mixed zinc zirconium oxides and found that samples with a zinc/zirconium ratio of roughly 1:10 strike the balance needed to passivate ZrO₂’s strong Lewis acid sites and incorporate a suitable level of basicity. The 1:10 catalysts shut down most unwanted reaction pathways and produce isobutene from ethanol in 83% yield, they report.