The 231st national meeting of the American Chemical Society featured a one-day symposium on Biofuels for Transportation during which fuel chemists and other scientists from across the United States and Europe presented research toward developing viable, cost-effective and high-performing biofuels.
Much of the focus on the one-day event was on biodiesel, although several presentations touched on cellulosic ethanol and hydrogen.
The fourteen presentations of the symposium included:
Factors affecting the stability of biodiesel sold in the United States. Researchers from the National Renewable Energy Laboratory surveyed biodiesel quality and stability in the United States. They collected 27 B100 samples from blenders and distributors nationwide., including 4 produced from waste oils, 1 from tallow, and the balance from soy.
They then conducted a series of chemical analyses and oxidation stability tests to reveal the factors influencing B100 stability. A typical US biodiesel exhibits 5 mg/100 ml of deposits on the ASTM D2274 accelerated stability test and less than 1 hour induction time on the EN 14112 Rancimat stability test.
Oxidative stability of biodiesel and NMR. Researchers at the USDA Agricultural Research Service (ARS) used nuclear magnetic resonance (NMR) to study the composition of biodiesel oxidized in open vessels at elevated temperatures. The results show enrichment of monounsaturated fatty acid chains and a decrease of diunsaturated species. The results coincided with other methods such as kinematic viscosity and acid value.
A pipeline for evaluating novel soydiesel derived from biotechnology. Researchers at the University of Nebraska investigated the introduction of novel oil traits through genetic engineering as a way to produce industrial products in oil seeds, such as soybean.
A comparison of biodiesel combustion performance with that of three other diesel fuels in a homogeneous charge compression ignition engine. Researchers at the Oak Ridge National Laboratory assessed the performance of a 100% biodiesel fuel (methyl ester), derived from soy oil, compared to three other hydrocarbon diesel fuels in an HCCI engine. Findings indicate that biodiesel requires earlier combustion phasing for peak efficiency, a hotter charge for ignition, burns more rapidly, and exhibits higher combustion temperatures than the HC based fuels. Total HC, CO, and NOx are all higher for the biodiesel.
Low temperature ignition behavior of methyl decanoate. A team from Penn State investigated the low-temperature ignition behavior of methyl decanoate, a biodiesel-relevant compound.
A numerical investigation into the anomalous slight NOx increase when burning biodiesel; A new (old) theory. A team from UC Berkeley and Lawrence Livermore National Laboratory reviewed previously proposed theories for the slight NOx increase from burning biodiesel, including theories based on biodiesel’s cetane number, which leads to differing amounts of charge preheating, and theories based on the fuel’s bulk modulus, which affects injection timing. This paper proposes a new theory explaining this NOx increase; the increase in double bonds in biodiesel, compared to No. 2 diesel, increases its flame temperature, which in turn increases NOx.
Emissions characteristics of a light duty diesel engine fueled with a hydrogenated biodiesel fuel. Penn State researchers explored the approach of achieving a more saturated biodiesel fuel and observing its effects on NOx emissions blended as B50. They explored the effects of hydrogenation of soybean oil prior to transesterification. The resulting fuel has a higher percentage of oleic acid methyl ester, and a reduction in the linoleic and linolenic methyl esters. Emissions testing on a light duty diesel engine revealed a decrease in NOx levels for some engine modes and an increase for other modes.
Reformulating biodiesel to reduce NOx emissions. This paper from researchers at the US Department of Agriculture described two methods for reformulating of methyl soyate (commercial biodiesel in the U.S.) in an attempt to reduce NOx emissions by changing the properties that would change the bulk modulus.
Examination of the behavior of biodiesel soot. This work from Penn State shows that although soot derived from the combustion of soybean oil-derived biodiesel fuel (B100) possesses an initially ordered structure, it is 5 times more reactive than soot obtained from combustion of a Fischer-Tropsch (F-T) diesel fuel. The oxidation mechanism of the B100 soot is unique, leading to capsule type oxidation and eventual formation of graphene ribbon structures.
Reduction of oxygen on the cytochrome c oxidase modified electrode. In this paper, scientists at Virginia Commonwealth University investigated the mechanisms of a biofuel cell by immobilizing cytochrome c oxidase and cytochrome c/ cytochrome c oxidase complex into lipid bilayer membranes on the gold electrodes.
Bio-based oxygenate for biofuels and fossil fuels. A team from Lehigh University and Gibson Technologies explored the application of a new process for the manufacture of dimethoxymethane (DMM)—an oxygenate proven equivalent to ethanol (EtOH) and dimethyl ether (DME) in its ability to lower soot emissions from internal combustion engines operating on gasoline or diesel fuel—to the conversion of pulp and paper mill waste gases.
The pulp mill waste gas becomes a renewable bio-source for DMM. In addition, the CO2 generated by the present incineration of pulp mill waste gas is eliminated thus yielding an environmental advantage.
Conversion of cellulose to glucose via alkyl glucosides. Researchers at Iowa State University described their process for converting cellulose to glucose via an acid catalyst.
Production of large, water-soluble intermediates from carbohydrate-derived compounds by sequential condensation/hydrogenation. A group from the University of Wisconsin (also involved in Virent—earlier post) introduced a bi-functional metal-base catalyst that is highly active, selective, hydrothermally stable and recyclable. The bi-functional catalyst allows a single-pot synthesis to produce large water-soluble organic molecules by aldol-condensation of carbohydrate-derived compounds over a base catalyst and subsequent hydrogenation over a metal catalyst. These water-soluble intermediates can be processed further by aqueous phase dehydration/hydrogenation to form liquid alkane fuels.
The selectivity and overall yield of the process can be controlled by the choice of reaction temperature and appropriate molar ratio for co-reactants during the condensation reaction. Developing a stable/recyclable aldol-condensation catalyst with a bi-functional characteristic, which permits a single-reactor design, is a significant advance on the path to making this technology industrially feasible by reducing operating and capital costs.
Direct use of H2-poor bio-syngas model in Fischer-Tropsch synthesis over un-promoted and rhenium promoted alumina-supported cobalt catalysts. A Scandinavian team from Chalmers University of Technology, KTE-Royal Institute of Technology and NTNU-Norwegian University of Science and Technology put a syngas of H2 and CO of different molar H2/CO-ratios (2.1, 1.5 and 1.0) through a fixed bed Fischer-Tropsch (FT) reactor over Co/Al2O3 and Co-Re/Al2O3 catalysts.
The FT-reaction requires a H2/CO-molar-ratio of approximately 2.1 above the catalyst surface. For the ratios lower than 2.1, a water-gas-shift activity is desired in order to increase the H2/CO-ratio.
With lower H2/CO-ratios in the feed, the CO conversion and the CH4 selectivity decreased, while the C5+ selectivity and C3(olefin/paraffin) ratio were slightly increased. However, the catalysts studied had very low water-gas-shift activities.
The Re-promoted was considerably more active and selective to longer hydrocarbons. The characterization of catalysts showed the positive effect of the Re in dispersion and reducibility of the catalysts. It is possible to utilize the advantages of an inlet ratio of 1.0 (higher selectivity to C5+, lower selectivity to CH4) if a low CO conversion is accepted.