Renewable high density fuels containing tricyclic sesquiterpanes and alkyl diamondoids

Abstract

Three new advanced biofuels have been produced from sesquiterpene feedstocks. Cedarwood oil, which is primarily composed of the sesquiterpenes thujopsene, α-cedrene, and β-cedrene, was hydrogenated to generate a fuel blend (HCWO) with a cetane number of 31 and a volumetric net heat of combustion (NHOC) more than 12% higher than conventional jet fuel. Hydrogenation under pressures ranging from 400 to 440 psi allowed for reduction of the double bond in thujopsene while keeping the cyclopropane ring intact. A single component high density fuel containing only hydrogenated α-cedrene (cedrane) was then prepared by dehydration and hydrogenation of α-cedrol, and found to have an even higher NHOC and lower viscosity than HCWO. Cedrane was then isomerized to 1-ethyl-3,5,7-trimethyladamantane (ETMA) and a mixture of other alkyl adamantanes. The adamantane mixture had a cetane number of 46 and a viscosity suitable for use in a conventional diesel engine. This work shows that sustainable multicyclic sesquiterpenes are versatile feedstocks to ultra-performance fuels that combine high densities with high cetane numbers.