Promotion of Activity and Selectivity by Alkanethiol Monolayers for Pd-Catalyzed Benzyl Alcohol Hydrodeoxygenation

作者：Lien Chih Heng; Medlin J Will^*

来源：Journal of Physical Chemistry C, 2014, 118(41): 23783-23789.

DOI：10.1021/jp507114g

In reactions of aromatic oxygenates, one promising strategy for improving selectivity toward desirable products is to control the ensembles of available surface sites and thus the adsorbed conformations of reactive intermediates. For this study, alkanethiolate self-assembled monolayers with variable surface densities were employed to restrict the conformation of adsorbed benzyl alcohol on Pd for enhancing hydrodeoxygenation selectivity to toluene and reducing decarbonylation selectivity to benzene. Toluene selectivity was dramatically improved on a 1-octadecanethiol-coated catalyst at the cost of a large decrease in reaction rate. On the other hand, deposition of a sparser 1-adamantanethiol (AT) coating improved selectivity to a smaller extent, but resulted in a higher reaction rate than that of the uncoated catalyst. Auger electron spectroscopy and temperature-programmed desorption (TPD) were used to further characterize this chemistry on a Pd(111) surface in ultrahigh vacuum. The TPD results match the selectivity results for the thiol-coated supported catalysts, revealing that increasing the surface density of thiols selectively shuts down decarbonylation while still allowing hydrodeoxygenation. The improved activity and selectivity for the AT-coated surface is attributed to weakened interactions of the phenyl ring with the surface.

• 出版日期2014-10-16