Development of a Bimetallic Pd-Ni/HZSM-5 Catalyst for the Tandem Limonene Dehydrogenation and Fatty Acid Deoxygenation to Alkanes and Arenes for Use as Biojet Fuel

Abstract

A tandem process involving the dehydroaromatization of the terpene limonene and the hydrodeoxygenation of stearic acid has been found to be efficiently catalyzed by Pd-Ni/HZSM-5. The process involves the generation of p-cymene from terpene with concomitant formation of H2, which leads to the one-pot hydrodeoxygenation of stearic acid to C17 and C18 alkanes; these products can be used as kerosene additives for aviation fuel. Screening a wide range of catalysts, the bimetallic Pd-Ni/HZSM-5 catalyst is the most efficient, leading to quantitative conversion of stearic acid to alkanes in limonene at 280 °C at a H2 pressure of 2 bar after 120 min. It has been found that single Ni or Pd catalysts lead to a poor conversion of stearic acid in limonene at a H2 pressure of 2 bar. The combination of physically mixed Pd- and Ni-sites onto different supports (Pd/HZSM-5 or Pd/C, and Ni/HZSM-5, Ni/HY, or Ni/HBEA) leads to catalysts which show satisfactory conversion to p-cymene but generally have very low stearic acid co...