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With the growing importance of climate change, soot emissions from engines have been receiving increasing attention since black carbon is the second largest source of global warming. A sooting tendency can be used to quantify the extent of soot formation in a combustion device for a given fuel molecule, and therefore to quantify the soot reduction benefits of alternative fuels. However real fuels are complex mixtures of multiple components. In this work, we have used experimental methods to investigate how the sooting tendency of a blended fuel mixture is related to the sooting tendencies of the individual components. A test matrix was formulated that includes sixteen mixtures of six components that are representative of the main categories of hydrocarbons in diesel (eicosane (ECO) for alkanes, isocetane (ICE) for isoalkanes, butylcyclohexane (BCH) for cycloalkanes, 1-methylnaphthalene (1MN) for aromatics, tetralin for naphthoaromatics, and methyl-decanoate (MDC) for oxygenates). Most of the mixtures contain three to five components. The sooting tendency of each mixture was characterized by yield sooting index (YSI), which is based on the soot yield when a methane/air nonpremixed flame is doped with 1000 ppm of the test fuel. The YSIs were measured experimentally. The results show that the blending behavior is linear, i.e., the YSI of the mixtures is the mole-fraction-weighted average of the component YSIs. Experimental results have shown that the sooting tendency of a fuel mixture can be accurately estimated as the linear combination of the individual components. In addition, mass density of the mixtures is also measured, and a linear blending rule is applied to test whether mixing rules exist for mass density of diesel mixtures in this study. Results also have shown that the mixing rule tested in this study is valid and mass density of a mixture can be accurately estimated from the linear combination of the individual components.

Bioderived ethers have recently drawn attention as a response to increasing demands on clean alternative fuels. A theory-experiment combined approach was introduced for the five ether molecules representing linear, branched, and cyclic ethers to derive rational design principles for low-emission and high-reactivity ethers. Flow reactor experiments and quantum-mechanical calculations were performed at high (750–1100K) and low temperature (400–700K) regimes to investigate the structural effects on their sooting tendency and reactivity, respectively. At a high-temperature regime, ethers’ high sooting tendency is related to increased C3 and C4 hydrocarbon formation compared to C1 and C2 products from oxidation reactions. On the other hand, the reactivity at the low-temperature regime is determined by the activation energies of reaction steps until ketohydroperoxide formation. These studies found that ethers’ sooting tendency and reactivity are relevant to two structural factors: the carbon type (primary to quaternary) and the relative position of ether oxygen atoms to carbon atoms. These factors were utilized to build a multivariate model to predict the cetane number (CN) and yield sooting index (YSI) of 50 different ethers. The model suggests building blocks with specific carbon types that maximize CN and minimize YSI, leading to the design principles of ethers toward low emissions and high reactivity fuels for transport applications. Ethers with a high CN and low YSI were then proposed using the developed model, and through experimental measurements, it was proved that they are promising biodiesel candidates.

Cobalt silicate was studied as a model catalyst to seek an understanding of why Co-MCM-41 catalyst is not active for single wall carbon nanotubes (SWNT) upon treatment at high temperature. Cobalt orthosilicate was formed during high-temperature pretreatment of Co-MCM-41 (at 900 °C) in an oxidizing environment. Cobalt silicate did not produce any carbon species during the first reaction cycle because the high thermal stability of cobalt silicate did not result in sufficient metallic Co clusters responsible for carbon dissociation in CO disproportionation. With repeated reaction cycles, however, undesirable carbon species, i.e., amorphous carbon and graphite, were produced resulting from larger metallic cobalt clusters formed at the high reduction temperature and without the confinement and/or anchoring of the MCM-41 matrix. These relatively large clusters do not catalyze the growth of SWNT.

A serious limitation for direct, routine mass spectrometric analysis of complex mixtures arises from the destructive nature of electron ionization methods employed in commercial instrumentation.

Highly ordered cobalt substituted MCM-41 samples were synthesized and characterized for application as catalytic templates for producing aligned single walled carbon nanotubes (SWNT). Highly reproducible Co−MCM-41 samples were successfully synthesized using alkyl templates with 10, 12, 14, 16, and 18 carbon chain lengths by direct incorporation of cobalt into the siliceous MCM-41 framework using a hydrothermal method; the pore size and the pore volume can be controlled precisely. The local environment of cobalt as determined by UV−vis spectroscopy is a mixture of tetrahedral and distorted tetrahedral structures similar to those observed in Co3O4. Cobalt atoms are uniformly distributed in the pores (about 30−40/pore) at nearly atomic dispersion probed by XAFS. Incorporation of cobalt into siliceous MCM-41 improves the structure, most likely by dehydroxylation and/or knitting the defective structure of the amorphous silica polymer. The optimum crystallization temperature and time were 100 °C and 4 days for ...