Renewable high density fuels containing tricyclic sesquiterpanes and alkyl diamondoids
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.