Autothermal reforming of palm empty fruit bunch bio-oil: thermodynamic modelling

This work focuses on thermodynamic analysis of the autothermal reforming of palm empty fruit bunch (PEFB) bio-oil for the production of hydrogen and syngas. PEFB bio-oil composition was simulated using bio-oil surrogates generated from a mixture of acetic acid, phenol, levoglucosan, palmitic acid and furfural. A sensitivity analysis revealed that the hydrogen and syngas yields were not sensitive to actual bio-oil composition, but were determined by a good match of molar elemental composition between real bio-oil and surrogate mixture. The maximum hydrogen yield obtained under constant reaction enthalpy and pressure was about 12 wt% at S/C = 1 and increased to about 18 wt% at S/C = 4; both yields occurring at equivalence ratio Φ of 0.31. The possibility of generating syngas with varying H2 and CO content using autothermal reforming was analysed and application of this process to fuel cells and Fischer-Tropsch synthesis is discussed. Using a novel simple modelling methodology, reaction mechanisms were proposed which were able to account for equilibrium product distribution. It was evident that different combinations of reactions could be used to obtain the same equilibrium product concentrations. One proposed reaction mechanism, referred to as the ‘partial oxidation based mechanism’ involved the partial oxidation reaction of the bio-oil to produce hydrogen, with the extent of steam reforming and water gas shift reactions varying depending on the amount of oxygen used. Another proposed mechanism, referred to as the ‘complete oxidation based mechanism’ was represented by thermal decomposition of about 30% of bio-oil and hydrogen production obtained by decomposition, steam reforming, water gas shift and carbon gasification reactions. The importance of these mechanisms in assisting in the eventual choice of catalyst to be used in a real ATR of PEFB bio-oil process was discussed

Selective Hydrogenation of Carbon Dioxide into Methanol

International audienceThis chapter is dedicated to methanol synthesis from carbon dioxide and hydrogen. Methanol, chemical formula CH3OH, is an important platform molecule which can be transformed into a large number of other chemicals, i.e., formaldehyde, acetic acid, dimethyl ether, methyl tert-butyl ether, and methyl methacrylate, as well as complex hydrocarbon mixtures, e.g., gasoline and diesel. Up to date, methanol is produced at industrial scale by steam reforming of natural gas, leading to high environmental impacts. The selective hydrogenation of carbon dioxide into methanol can be a good alternative since it is possible to capture carbon dioxide from industrial processes and to produce hydrogen from renewable energies, e.g., solar energy and wind energy.From a thermodynamic point of view, carbon dioxide hydrogenation is strongly influenced by the total pressure, temperature, and feeding composition. The use of a catalyst is also mandatory to control the kinetic and the selectivity into methanol. Among solid catalysts studied, copper-based catalysts have been found to be the best catalytic systems. Promoters like zinc oxide were usually used. Nickel-, palladium-, and silver-based catalysts also showed good catalytic performance compared to copper-based catalysts. Soluble catalysts have been intensively studied for this hydrogenation. Ru complexes appeared as the best homogeneous catalyst. Other metal-free homogeneous catalysts, e.g., N-heterocyclic carbenes, have been found to be active and selective in this reaction. Efforts have been made on the mechanistic study of the reaction in both the gas and liquid phases. Large industrial production has started in several countries showing the interest and the feasibility of the process

In situ Characterisation of Practical Heterogeneous Catalysts

In situ methods are considered as a curiosity within the standard methodology of practical catalyst characterization. The methods are not commercially available and need to be adapted and validated for each specific problem. The great advantage of these methods is, however, that they deliver immediately relevant characteristics of the working state of a heterogeneous catalyst and allow justified structure-function relations to be deduced. To achieve this it is essential that the experiments are planned and conducted in such away that the proven to be active state of the catalyst is investigated. This can only be ascertained if simultaneous kinetic and spectroscopic data are acquired. The contribution lists a selection of methods with their main characteristics that allows to choose from the wide spectrum of information those that are most relevant for the given problem. A tabulated selection of case studies from the literature gives some insight in the current practice