Amination of 1-hexanol on bimetallic AuPd/TiO2 catalysts. Issue 20 (2nd October 2018)

• Record Type: Journal Article
• Authors: Ball, Madelyn R.; Wesley, Thejas S.; Rivera-Dones, Keishla R.; Huber, George W.; Dumesic, James A.
• Is Part Of: Green chemistry. Volume 20:Issue 20(2018)
• Page Start: 4695
• Page End: 4709
• Publication Date: 2018-10-02
• Subjects: Environmental chemistry -- Industrial applications -- Periodicals; Environmental management -- Periodicals; 660
• DOI: 10.1039/c8gc02321b
• Languages: English
• ISSNs: 1463-9262

Abstract

Abstract : AuPd/TiO2 bimetallic catalysts, synthesized using controlled surface reactions, exhibit enhanced rates for amination of hexanol using ammonia compared to monometallic Au and Pd catalysts. Abstract : AuPd/TiO2 catalysts, synthesized using controlled surface reactions, are active for the gas-phase amination of 1-hexanol using ammonia. The bimetallic active sites for these catalysts have been characterized using CO chemisorption and XAS techniques, and the absence of monometallic Pd species in the AuPd catalysts was confirmed using UV-vis and STEM-EDS analysis. The bimetallic catalysts exhibit synergy between Au and Pd, as the rate of hexanol conversion increases from 8.7 μmol ks −1 (μmol total Pd) −1 over Pd/TiO2 to up to 42 μmol ks −1 (μmol total Pd) −1 over AuPd/TiO2 with a Pd/Au atomic ratio of 0.06. The rate of hexanol conversion is also enhanced with respect to Au content, with a 5-fold increase in the total Au-normalized rate from Au/TiO2 to AuPd0.67 /TiO2 . As Pd is added to Au/TiO2 in increasing quantities, the production rate of primary species ( i.e., hexylamine and hexanenitrile) is preferentially increased. The rate of dihexylamine production increases to a lesser extent, while trihexylamine formation remains relatively constant across Pd loadings. Moreover, trihexylamine, which cannot be formed via the condensation of dihexylamine and hexanol, is shown to be produced via the secondary aldimine, N -hexylidene hexylamine. The AuPd bimetallic catalysts also exhibit reduced hydrogenolysis activity compared to monometallic Pd/TiO2 .