Investigating the multifunctional nature of bimetallic FeMoP catalysts using dehydration and hydrogenolysis reactions

Abstract

Herein, we investigate the effects of altering the multifunctional nature of a series of FeMoP catalysts for biomass deoxygenation reactions. Unsupported FeMoP catalysts were synthesized at reduction temperatures between 650 degrees C and 850 degrees C. The reduction temperature used during the synthesis of FeMoP altered the surface properties of these materials (i.e., acidity and CO-titrated metal sites) while leaving the bulk crystal structure of FeMoP unaffected. This alteration in the surface properties significantly affected the catalytic performance of FeMoP materials in the deoxygenation reactions. The catalytic performance of the FeMoP catalysts was first investigated using the acid catalyzed, non-aqueous, dehydration of cyclohexanol. Aside from showing high selectivities to cyclohexene (>99%) for all catalysts, the experiments demonstrated that FeMoP-650 showed the highest initial rate due to the largest number of surface acid sites among these catalysts. In addition, these FeMoP catalysts were examined using the hydrodeoxygenation (HDO) of phenol. While all FeMoP catalysts were highly selective to benzene (similar to 90%) at conversions less than 15%, studies at higher conversions of phenol provided evidence that catalysts with a higher amount of acid sites maintained enhanced selectivity to benzene. Furthermore, the stability of FeMoP catalysts for phenol HDO was tested with a 48 h time-on-stream (TOS) study. FeMoP exhibited excellent stability, as evidenced by the retention of the initial reaction rate, selectivity to benzene, and oxidation state of surface species throughout the TOS run.