Thermal cyclodimerization of isoprene for the production of high-performance sustainable aviation fuel

Abstract

Isoprene was converted to a jet fuel blendstock through thermal cyclodimerization followed by hydrogenation. The dimerization was performed at moderate temperature (200 °C) and completed in 90 min. The product distribution consisted of six isomers produced via Diels-Alder [4+2]-cycloadditions as well as [4+4]-cycloadditions. The hydrogenation reactions were conducted with Pt, Pd, and Ni-based catalysts. The Pt and Ni catalysts yielded 499% saturated C10H20 products, while significant quantities of p- and m-cymene were generated with the Pd-catalyst. The hydrogenated isoprene dimers (HID) exhibited outstanding fuel properties including a gravimetric net heat of combustion (NHOC) of 43.34 MJ kg-1, a density of 0.806 g mL-1, and a -20 °C kinematic viscosity of 3.10 mm2 s-1. These values are 1.3% higher, 4% higher, and 61% lower, respectively, compared to the Jet-A specifications. These properties suggest that HID can be used as a blendstock with either conventional jet fuel or biobased synthetic paraffinic kerosenes (SPKs) to enhance the operability and performance of the final fuel blend. The catalyst- and solvent-free dimerization method is amenable to a high-throughput process for fuel production. In combination with biosynthetic generation of isoprene or isoprene precursors, the approach described herein holds great promise for the formulation of drop-in sustainable aviation fuels.