Influence of Dioxygen on the Promotional Effect of Bi during Pt-Catalyzed Oxidation of 1,6-Hexanediol

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• 作者：Jiahan Xie ; Benjamin Huang ; Kehua Yin ; Hien N. Pham ; Raymond R. Unocic ; Abhaya K. Datye ; Robert J. Davis
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：July 1, 2016
• 年：2016
• 卷：6
• 期：7
• 页码：4206-4217
• 全文大小：625K
• 年卷期：0
• ISSN：2155-5435

文摘

A series of carbon-supported, Bi-promoted Pt catalysts with various Bi/Pt atomic ratios was prepared by selectively depositing Bi on Pt nanoparticles. The catalysts were evaluated for 1,6-hexanediol oxidation activity in aqueous solvent under different dioxygen pressures. The rate of diol oxidation on the basis of Pt loading over a Bi-promoted catalyst was 3 times faster than that of an unpromoted Pt catalyst under 0.02 MPa of O₂, whereas the unpromoted catalyst was more active than the promoted catalyst under 1 MPa of O₂. After liquid-phase catalyst pretreatment and 1,6-hexanediol oxidation, migration of Bi on the carbon support was observed. The reaction order in O₂ was 0 over Bi-promoted Pt/C in comparison to 0.75 over unpromoted Pt/C in the range of 0.02–0.2 MPa of O₂. Under low O₂ pressure, rate measurements in D₂O instead of H₂O solvent revealed a moderate kinetic isotope effect (rate_H2O/rate_D2O) on 1,6-hexanediol oxidation over Pt/C (KIE = 1.4), whereas a negligible effect was observed on Bi-Pt/C (KIE = 0.9), indicating that the promotional effect of Bi could be related to the formation of surface hydroxyl groups from the reaction of dioxygen and water. No significant change in product distribution or catalyst stability was observed with Bi promotion, regardless of the dioxygen pressure.