Concerted reactions are proposed to be keys to understanding thermal decomposition of glucose in the absence of ionic chemistry, including molecular catalysis by ROH molecules such as H(2)O, other glucose molecules, and most of the intermediates and products. Concerted transition states, elementary-reaction pathways, and rate coefficients are computed for pyrolysis of β-D-glucose (β-D-glucopyranose), the monomer of cellulose, and for related molecules, giving an improved and elementary-reaction interpretation of the reaction network proposed by Sanders et al. (J. Anal. Appl. Pyrolysis, 2003, 66, 29-50). Reactions for ring-opening and formation, ring contraction, retro-aldol condensation, keto-enol tautomerization, and dehydration are included. The dehydration reactions are focused on bicyclic ring formations that lead to levoglucosan and 1,6-β-D-anhydrousglucofuranose. The bimolecular ROH-assisted reactions are found to have lower activation energy compared to the unimolecular reactions. The same dehydration reaction to levoglucosan should occur for cellulose going to cellosan (e.g., cellotriosan) plus a shortened cellulose chain, a hypothesis supported by the very similar activation energies computed when alternate groups were substituted at the C1 glycosidic oxygen. The principles of Sanders et al. that distinguish D-glucose, D-fructose, sucrose, and cellulose pyrolysis prove useful in providing qualitative insights into cellulose pyrolysis.

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Ignition of methane-air and propane-air mixtures over platinum catalyst in a parallelplate microburner is studied numerically and a comparison of their ignition characteristics is presented. The ignition behaviour of the two fuels is compared for the case of heated feed and the strategy of using propane-methane mixed fuel is analysed. We show that adding small quantities of propane reduces the ignition temperature of lean methane-air mixture. Transient response of the mixed methane-propane fuel reveals sequential ignition of propane followed by methane. Sensitivity analysis on physical properties of methane and propane shows that the higher apparent activation energy of methane combustion accounts for most of the observed differences in their ignition behaviour. Ignition by resistive preheating, specifically the effect of locally preheating initial section of the burner is investigated. The amount of electric power required for ignition decreases with decrease in the electrical preheating length. This reduction in ignition power is especially significant for low conductivity walls, compared to highly conducting walls. Finally, the gap size of the channel has a relatively small effect on ignition in catalytic microburners.