Issue 20, 2018

Amination of 1-hexanol on bimetallic AuPd/TiO2 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.

Graphical abstract: Amination of 1-hexanol on bimetallic AuPd/TiO2 catalysts

Supplementary files

Article information

Article type
Paper
Submitted
25 Jul 2018
Accepted
24 Sep 2018
First published
25 Sep 2018

Green Chem., 2018,20, 4695-4709

Author version available

Amination of 1-hexanol on bimetallic AuPd/TiO2 catalysts

M. R. Ball, T. S. Wesley, K. R. Rivera-Dones, G. W. Huber and J. A. Dumesic, Green Chem., 2018, 20, 4695 DOI: 10.1039/C8GC02321B

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