Molecular Design and Characterization of High-Cetane Alkyl Diamondoid Fuels

Abstract

Four alkyl diamondoids, 1-pentyladamantane (PA), 2-butyladamantane (BA), 2-propyladamantane (2-PrA), and 2-ethyladamantane (EA), were synthesized on a preparative scale, and key fuel properties, including density, net heat of combustion, low-temperature viscosity, and derived cetane number (DCN), were measured. The fuel molecules had densities up to 17% higher than conventional jet fuel and volumetric net heats of combustion comparable to or exceeding that of the synthetic missile fuel JP-10. Remarkably, the alkyl diamondoid fuels had DCNs in the range of 42–49, which should allow for their efficient combustion in diesel engines. PA, BA, and 2-PrA all had essentially the same DCN (∼49), while the short alkyl chain in EA lowered the value to 42.7. Bond dissociation energies for the formation of diradicals from 2-PrA and PA were calculated with density functional theory methods to gain a qualitative understanding of potential combustion mechanisms. Ring opening of the adamantane core during combustion is proposed to explain the high cetane number of these fuels. The alkyl diamondoids described in this report are the first examples of multicyclic hydrocarbons that combine extraordinary densities (>0.9 g/mL) with DCNs comparable to or exceeding that of conventional diesel fuel.

Hydroconversion of Perhydrophenanthrene over Bifunctional Pt/H‐USY Zeolite Catalyst

“…These compounds have high cetane index and superior diesel quality. [13] We could also analyse the ring opening selectivity, i. e. the tendency to open the central vs. a terminal ring of PHP isomers. The detailed knowledge of the structure of ring opening products allowed us in turn to rationalise the distribution of cracked products.…”

Synthesis of Bio‐Based Methylcyclopentadiene from 2,5‐Hexanedione: A Sustainable Route to High Energy Density Jet Fuels

“…Due to its high density, pure RJ‐4 has applications as a high NHOC fuel for cruise missile propulsion, [38–40] while its low volatility and high flashpoint are well suited for ramjet engines [41] . More recently, researchers have shown that RJ‐4 can be efficiently converted to 1,3‐dimethyladamantane, a thermally stable jet fuel of interest for high speed applications [42] …”

“…[41] More recently, researchers have shown that RJ-4 can be efficiently converted to 1,3dimethyladamantane, a thermally stable jet fuel of interest for high speed applications. [42] To develop a route to RJ-4 from lignocellulosic feedstocks, it was of interest to explore 2,5-hexanedione [HD (1)] as a platform chemical for the synthesis of methylcyclopentadiene [MCPD (4), Scheme 1]. Fructose can be readily converted to 5hydroxymethylfurfural (HMF) through isomerization and acid-catalyzed dehydration, followed by selective hydrogenolysis, to generate 2,5-dimethylfuran (DMF).…”

Density, Viscosity, and Refractive Index for Binary Mixtures of Three Adamantane Derivatives with n-Nonane or n-Undecane at T = 293.15–343.15 K and Atmospheric Pressure

“…It has been reported that adamantane fuels derived from some reservoirs exhibit a high density and volumetric heating value, and they are regarded as one new kind of high-energy-density hydrocarbon fuel. Alkyl-substituted adamantanes are specifically attractive, as they possess good low-temperature properties …”

“…Alkyl-substituted adamantanes are specifically attractive, as they possess good lowtemperature properties. 5 1,3-Dimethyladamantane (1,3-DMA), which is an alkyl derivative of adamantanes, has satisfying density and good thermal stability. 6,7 1,3-DMA even shows higher thermal stability than JP-10 (used by U.S. Navy and Air Force), which has been considered as a new candidate of high-energy-density fuels or energetic additives for conventional fuels.…”