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a Lignin solvolysis in supercritical alcohols provides a method for producing a deoxygenated liquid bio-oil. Solvent consumption is however inevitable and due to the high cost of alcohols, relative to a bio-oil product, it can hinder commercial viability. In order to investigate the reactions of solvent consumption we studied solvolysis of biorefinery lignin in several primary alcohols. Lignin solvolysis in methanol, ethanol, 1-propanol and 1-butanol performed similarly with respect to bio-oil composition; however, methanol gave much lower bio-oil yield. Solvent consumption increases with reaction temperature for all alcohols and from 10 wt% at 300°C to 35 wt% at 400°C when using ethanol. The mechanism for solvent consumption was found mainly to take place through three different reactions: Direct decomposition to gas through decarbonylation, formation of light condensation products and incorporation of the alcohol into the bio-oil through covalent bonding. Incorporation of the alchohol into the depolymerised oil product by covalent bonding may be a desirable effect which contributes to increased oil yield, inhibition of repolymerisation, reduced oxygen content and elimination of acidity. IntroductionSolvolysis of lignin rich biomass is of growing interest as a process for producing liquid fuels and chemicals. 1, 2 An important issue in such a process is consumption of the solvent, since the cost of solvent may exceed the value of the depolymerised lignin product. Undesired solvent consumption can therefore hinder commercial viability.The mechanisms of solvent consumption in biomass solvolysis reactions are not understood in detail. Alcohols thermally decompose to gasses at elevated temperatures starting already at the supercritical temperature. 3 Even in reactions where the solvent is recognised as being a reactant, and acting as a hydrogen donor, solvent consumption is often an overlooked parameter. 1,2 Reactions in which alcohol solvent is consumed due to reaction with lignin is seen in some studies where the yield of solids and liquid depolymerised lignin species exceed the amount of initially added lignin 4, 5 hence transformation of solvent to biooil must occur. Direct alkylation of depolymerised lignin by ethanol can be described by a mechanism by Zhao et al. 6 , where alcohol radicals facilitate cleavage and resulting in its incorporation in the depolymerised lignin molecule. The alcohol most likely both facilitates lignin polymer cleavage and inhibition of repolymerisation by reaction with reactive radical species formed at elevated temperatures. Barnard investigated the thermal decomposition of ethanol at 576 °C -624 °C and observed significant gas yields and in particular also a brown polymer. 7 Higher alcohol synthesis as described by Guerbet 8, 9 may be responsible for formation of heavier alcohol polymerisation products that will be found in the bio-oil fraction after lignin solvolysis.We previously conducted a parametric study of bio-refinery lignin solvolysis by ethanol assessing the effect of re...

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A nonlinear wear model for a cylinder rolling over a periodically varying surface is derived from the theory of half spaces. The model describes how some irregularities on the surface are amplified whereas others are levelled out as the number of cylinder passages increases. This is a pure nonlinear contact mechanical effect independent of the dynamic response of the cylinder and the support. The aim of the present work is to demonstrate, that these nonlinearities, which often are neglected in models for wheel/rail interaction, play an important role in the evolution of corrugation of rails.