High-Density Renewable Fuels Based on the Selective Dimerization of Pinenes

High-density fuel candidates have been synthesized in up to 90% yield from β-pinene, a renewable strained bicyclic compound derived from wood and plant sources. The process is based on the heterogeneous acidic catalysts Montmorillonite-K10 and Nafion, which promote selective isomerization and dimerization of pinenes under moderate conditions (100 °C and atmospheric pressure). Montmorillonite-K10 was shown to be a highly active catalyst for dimerization but was also active in the ring opening of β-pinene followed by dehydrogenation to produce p-cymene, which limited the yield of the dimer to ca. 75%. Nafion was capable of producing dimers in up to 90% yield primarily through isomerization followed by dimerization. Amberlyst-15, a common industrial catalyst had very poor activity and conversion even at 150 °C. The dimer mixtures were upgraded through hydrogenation over PtO2 and fractional distillation. The synthesized fuels have a density of 0.94 g/cm3 and a net volumetric heating value of 39.5 MJ/L (141 745 BTU/gallon). These values are nearly identical to those for the widely used tactical fuel JP-10 (primarily composed of exotetrahydrodicyclopentadiene), suggesting that these renewable fuels may have applications for rocket propulsion.