Hydrodeoxygenation of m-Cresol Over Pt-WOx/C Using H2 Generated In Situ by n-Hexane Dehydrogenation

Abstract

Hydrodeoxygenation (HDO) of m-cresol using H2 produced by dehydrogenation of n-hexane to hexenes is demonstrated at 673 K over a Pt-WOx/C catalyst at 36 bar. The reaction is possible because deactivation of Pt/C during n-hexane dehydrogenation is greatly suppressed at higher pressures. Flow-reactor measurements of pure n-hexane over Pt/C showed rapid deactivation at 1 bar and 773 K but the catalyst was stable for at least 5 h at 36 bar. While the Pt/C catalyst showed poor activity for HDO of m-cresol, the Pt-WOx/C catalyst was able to utilize the H2 to selectively catalyze m-cresol to toluene, simultaneously pushing the conversion of n-hexane above the equilibrium value that would be achieved in the absence of H2 consumption. To explain the increased stability for alkane dehydrogenation at higher pressures, a microkinetic model of propane dehydrogenation, a surrogate of hexane, was analyzed. The model demonstrates that the coverage of vacancies increases with increasing pressure at the expense of species believed to be coke precursors.