Rhodri W. Jenkins

Renewable biofuel additives from the ozonolysis of lignin

In this investigation ozonolysis in the presence of ethanol was used to depolymerise lignin, resulting in a low conversion of oxygenated aromatics over short reaction times, or a range of saturated esters over 24 h. Short chain oxygenates can be used as fuel additives, displacing a percentage of a hydrocarbon fuel while leading to improvement in some of the fuel properties. The utility of the resulting bio-oils was therefore assessed by blending with a range of fuels. Guaiacol, a potential antioxidant, was formed over short reaction times and was found to be completely miscible with low-sulphur petrol (ULSP), diesel, aviation kerosene and rapeseed methyl ester. The mainly aliphatic proportion of the bio-oil produced over 24 h could be blended with the fuels replacing a maximum of 12-17 wt.% of the hydrocarbon fuel.

The effect of functional groups in bio-derived fuel candidates

Interest in developing renewable fuels is continuing to grow and biomass represents a viable source of renewable carbon with which to replace fossil-based components in transportation fuels. During our own work, we noticed that chemists think in terms of functional groups whereas fuel engineers think in terms of physical fuel properties. In this Concept article, we discuss the effect of carbon and oxygen functional groups on potential fuel properties. This serves as a way of informing our own thinking and provides us with a basis with which to design and synthesize molecules from biomass that could provide useful transportation fuels.

Acetaldehyde as an ethanol derived bio-building block: an alternative to Guerbet chemistry

In this work, we describe a highly selective poly-aldol condensation of acetaldehyde, which can readily be obtained via dehydrogenation of ethanol. The process operates under mild temperatures (100 °C or less) using commercially available catalysts and exhibits excellent total carbon yield of C4+ products with good selectivity for C6 products. The products derived from the reactions described herein are shown to be candidate drop-in fuel replacements for compression ignition engines and precursors to valuable chemicals.

Heterogeneous Ketone Hydrodeoxygenation for the Production of Fuels and Feedstocks from Biomass

In this work, we describe a simple, heterogeneous catalytic system for the hydrodeoxygenation (HDO) of 5‐nonanone and 2,5‐hexanedione, which we use as model compounds for more complex biomass‐derived molecules. We present the stepwise reduction of ketones by using supported metal and solid acid catalysts to identify the intermediates en route to hydrocarbons. Although monoketone HDO can be achieved rapidly using moderate conditions (Ni/SiO2.Al2O3, HZSM‐5, 200 °C, 1.38 MPa H2, 1 h), quantitative γ‐polyketone HDO requires higher pressures and longer reaction times (Pd/Al2O3, HZSM‐5, 2.76 MPa H2, 5 h), although these are more facile conditions than have been reported previously for γ‐polyketone HDO. Stepwise HDO of the γ‐polyketone shows the reaction pathway occurs through ring‐closure to a saturated tetrahydrofuran species intermediate, which requires increased H2 pressure to ring‐open and subsequently to fully HDO. This work allows for further understanding of bio‐derived molecule defunctionalization mechanisms, and ultimately aids in the promotion of biomass as a feedstock for fuels and chemicals.

Synthesis of Acetone‐Derived C6, C9, and C12 Carbon Scaffolds for Chemical and Fuel Applications

A simple, inexpensive catalyst system (Amberlyst 15 and Ni/SiO2 -Al2 O3 ) is described for the upgrading of acetone to a range of chemicals and potential fuels. Stepwise hydrodeoxygenation of the produced ketones can yield branched alcohols, alkenes, and alkanes. An analysis of these products is provided, which demonstrates that this approach can provide a product profile of valuable bioproducts and potential biofuels.

The emissions and the performance of diethyl succinate in a diesel fuel blend

The finite natures of fossil fuels and their contributions to anthropogenic climate change are driving the development of biofuels. However, because of the inherent issues with current biofuels, such as ethanol and biodiesel, innovative replacements are being increasingly sought. Recently, four esters produced from fermentation, namley diethyl succinate, dibutyl succinate, dibutyl fumarate and dibutyl malonate, were reported to have suitable physical properties as a substitute for conventional diesel fuel. Although the physical properties are indicative of the fuel behaviour, the determination of the combustion emissions and the performance of a fuel using controlled engine testing is vital. In this investigation, the engine performance and emissions produced from the most viable fuel, namely diethyl succinate, were examined. Diethyl succinate was blended with diesel in a 20 vol % blend, owing to the low cetane number of diethyl succinate, and the emissions established in pseudo-steady-state conditions using a 2.0 L turbocharged direct-injection EURO 3-compliant light commercial vehicle equipped with a direct-injection common-rail diesel engine. When using the diesel–20 vol % diethyl succinate blend, the fuel demand and the wheel force were higher for the majority of engine speeds than those of diesel, whereas the exhaust gas temperatures were lower. The difference between the exhaust gas temperature for the diesel–20 vol % diethyl succinate blend and that for diesel increased with increasing pedal demand. In comparison with the carbon monoxide emissions from petroleum-derived diesel, the carbon monoxide emissions obtained when using the diesel–20 vol % diethyl succinate blend were reduced, most probably because of more complete combustion due to the increased oxygen content. However, the total hydrocarbon emissions and the mono-nitrogen oxide emissions were shown to increase on using the diethyl succinate blend. Both of these factors were presumably due to the lower cetane number of the fuel, although the increase in the total hydrocarbon emissions was deemed negligible because of the low amount produced by both fuels.