title: Key Roles of Lewis Acid-Base Pairs on ZnxZryOz in Direct Ethanol/Acetone to Isobutene Conversion.
abstract: The effects of surface acidity on the cascade ethanol-to-isobutene conversion were studied using ZnxZryOz catalysts. The ethanol-to-isobutene reaction was found to be limited by the secondary reaction of the key intermediate, acetone, namely the acetone-to-isobutene reaction. Although the catalysts with coexisting Brønsted acidity could catalyze the rate-limiting acetone-to-isobutene reaction, the presence of Brønsted acidity is also detrimental. First, secondary isobutene isomerization is favored, producing a mixture of butene isomers. Second, undesired polymerization and coke formation prevail, leading to rapid catalyst deactivation. Most importantly, both steady-state and kinetic reaction studies as well as FTIR analysis of adsorbed acetone-d6 and D2O unambiguously showed that a highly active and selective nature of balanced Lewis acid-base pairs was masked by the coexisting Brønsted acidity in the aldolization and self-deoxygenation of acetone to isobutene. As a result, ZnxZryOz catalysts with only Lewis acid-base pairs were discovered, on which nearly a theoretical selectivity to isobutene (∼ 88.9%) was successfully achieved, which has never been reported before. Moreover, the absence of Brønsted acidity in such ZnxZryOz catalysts also eliminates the side isobutene isomerization and undesired polymerization/coke reactions, resulting in the production of high purity isobutene with significantly improved catalyst stability (<2% activity loss after 200 h time-on-stream). This work not only demonstrates a balanced Lewis acid-base pair for the highly active and selective cascade ethanol-to-isobutene reaction but also sheds light on the rational design of selective and robust acid-base catalyst for C-C coupling via aldolization reaction.
authors.affiliation: The Gene & Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University , Pullman, Washington 99164, United States.
authors.forename: Junming
authors.initials: J
authors.lastname: Sun
authors.affiliation: The Gene & Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University , Pullman, Washington 99164, United States.
authors.forename: Rebecca A L
authors.initials: RA
authors.lastname: Baylon
authors.affiliation: The Gene & Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University , Pullman, Washington 99164, United States.
authors.forename: Changjun
authors.initials: C
authors.lastname: Liu
authors.affiliation: Institute for Integrated Catalysis, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Donghai
authors.initials: D
authors.lastname: Mei
authors.affiliation: Archer Daniels Midland Company, 1001 N Brush College Road, Decatur, Illinois 62521, United States.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Martin
authors.affiliation: Archer Daniels Midland Company, 1001 N Brush College Road, Decatur, Illinois 62521, United States.
authors.forename: Padmesh
authors.initials: P
authors.lastname: Venkitasubramanian
authors.affiliation: The Gene & Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University , Pullman, Washington 99164, United States.|Institute for Integrated Catalysis, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang