A Combined Photobiological-Photochemical Route to C10 Cycloalkane Jet Fuels from Carbon Dioxide via Isoprene

Abstract

The hemiterpene isoprene is a volatile C5 hydrocarbon with industrial applications. It is generated today from fossil resources, but can also be made in biological processes. We have utilized engineered photosynthetic cyanobacteria for direct, light-driven production of bio-isoprene from carbon dioxide, and show that isoprene in a subsequent photochemical step, using either near-UV or simulated or natural solar light, can be dimerized into limonene, paradiprene, and isomeric C10H16 hydrocarbons (monoterpenes) in high yields under photosensitized conditions (above 90% after 44 hours with near-UV and 61% with simulated solar light). The optimal sensitizer in our experiments is di(naphth-1-yl)methanone which we use with a loading of 0.1 mol%. It can also easily be recycled for subsequent photodimerization cycles. The isoprene dimers generated are a mixture of [2+2], [4+2] and [4+4] cycloadducts, and after hydrogenation this mixture is nearly ideal as a drop-in jet fuel. Importantly the photodimerization can be carried out at ambient conditions. However, the high content of hydrogenated [2+2] dimers in our isoprene dimer mix lowers the flash point below the threshold (38 °C), yet, these dimers can be converted thermally into [4+2] and [4+4] dimers. When hydrogenated these monoterpenoids fully satisfy the criteria for drop-in jet fuels with regard to energy density, flashpoint, kinematic viscosity, density, and freezing point. Life-cycle assessment results show a potential to produce the fuel in an environmentally sustainable way.

Light-driven (cross-)dimerization of terpenes as a route to renewable C15 – C30 crudes for fuel and lubricant oil applications

“…On the basis of our previous study, 35 1,1-dinapthylmethanone 8 was used as photosensitizer. Additionally screening with other aromatic ketone derivatives was also performed for dimerization of myrcene in search of a better photosensitizer, however 8 was proved to be the best choice (Table S1, ESI).…”

“…The photosensitizer 8 exhibits a broad absorption band within the range of 300 -400 nm, 35,41 which might enable the dimerization to be carried out under simulated and natural sunlight. Therefore, mixtures of myrcene and αphellandrene with 8 were irradiated under simulated sunlight with an intensity of 1 sun equivalent (AM 1.5 G) and using a flat coiled FEP tubing (CMS IV, Fig.…”

“…33 Since cycloalkanes are reported as high energy density combustion fuels, 34 our group has recently reported on a fruitful route to solar jet fuels, where the photobiologically produced isoprene is subject to photosensitized dimerization. 35 Herein, we apply the photochemical dimerization approach to mono-and sesquiterpenes bearing conjugated diene, e.g. α-phellandrene 1, myrcene 2 and ocimene 3.…”

A Simple Process for the Dimerization and Cross-Coupling of Isoprene and Myrcene to High-Performance Jet and Diesel Blendstocks

“…The mixture of cycloadducts was further hydrogenated and evaluated for use as a jet fuel surrogate. 25 Staples et al recently described the thermal cyclodimerization of myrcene. 24 Their process generated a blend of C20 cycloalkene and heavier oligomers, which were isolated and then hydrogenated with a heterogeneous nickel catalyst system.…”

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

“…35 More recently, Ottosson and co-workers reported a photochemical route to cyclic isoprene dimers. 36 Isoprene can also be effectively dimerized via a [4+4]-cycloaddition catalyzed by an iron pyridineimine (Fe-PDI) catalyst to generate 2,6-dimethyl-1,5-cyclooctadiene (DMCOD). 37,38 As an alternative to these approaches, isoprene can undergo a [4+2]-cycloaddition to generate substituted cyclohexenes.…”