Fluorinated hydrotreatment catalysts: Hydrodeoxygenation and hydrocracking on fluorine-nickel-molybdenum/γ-alumina catalysts

Abstract

The degree of conversion of the hydrodeoxygenation (HDO) of tetrahydrofuran and the hydrocracking of 2,4,4-trimethyl-1-pentene (HCG), used as probe reactions, was determined over the surface of the Ni-Mo/γ-Al 2O 3 catalysts modified with various amounts of fluoride ions. Concerning HDO it was found that doping with small amount of fluoride ions (0.3-0.8% fluoride) increases the degree of conversion whereas further increase in the dopant concentration causes a drop in the conversion. Comparison of the graphs of degree of conversion vs. fluoride content with the graph of nitric oxide uptake vs. fluoride content resulted in the conclusion that fluorination changes the HDO activity mainly by altering the number of active sites. The dependence of the apparent rate constant determined in the present work on the dopant concentration showed that fluorination also changes the activity of each active site. Concerning HCG no change in the catalytic activity was observed upon fluorination. Finally, based on results reported previously for the hydrodesulfurization (HDS) of thiophene it was concluded that, as in the case of HDO, fluorination modifies the HDS activity by altering both the number of active sites and the activity of each site.