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Pyrolysis of lignocellulosic biomass and reforming of the pyroligneous oils are being studied as a strategy for producing hydrogen. A process of this nature has the potential to be cost competitive with conventional means of producing hydrogen. We propose a regionalized system of hydrogen production, where small- and medium-sized pyrolysis units (<500 Mg/day) provide bio-oil to a central reforming unit to be catalytically converted to H2 and CO2. Thermodynamic modeling of the major constituents of the bio-oil has shown that reforming is possible within a wide range of temperatures and steam-to-carbon ratios. In addition, screening tests aimed at catalytic reforming of model compounds to hydrogen using Ni-based catalysts have achieved essentially complete conversion to H2. Existing data on the catalytic reforming of oxygenates have been studied to guide catalyst selection. A process diagram for the pyrolysis and reforming operations is discussed, as are initial production cost estimates. A window of opportunity clearly exists if the bio-oil is first refined to yield valuable oxygenates so that only a residual fraction is used for hydrogen production.

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We investigated the production of hydrogen by the catalytic steam reforming of model compounds of biomass fast-pyrolysis oil (bio-oil). Acetic acid, m-cresol, dibenzyl ether, glucose, xylose, and sucrose were reformed using two commercial nickel-based catalysts for steam reforming naphtha. The experiments were conducted at a methane-equivalent gas hourly space velocity (G C1 HSV) from 500 to 11790 h -1 . Steam-to-carbon ratios (S/C) of 3 and 6 and catalyst temperatures from 550 to 810 °C were selected. Rapid coking of the catalyst was observed during acetic acid reforming at temperatures lower than 650 °C. Acetic acid, m-cresol, and dibenzyl ether were completely converted to hydrogen and carbon oxides above this temperature, and hydrogen yields ranged from 70 to 90% of the stoichiometric potential, depending on the feedstock and reforming conditions. Sugars were difficult to reform because they readily decomposed through pyrolysis in the freeboard of the reactor. This led to the formation of char and gases before contacting the catalyst particles.

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The continuous increase in oil prices together with an increase in carbon dioxide concentration in the atmosphere has prompted an increased interest in the production of liquid fuels from non-petroleum sources to ensure the continuation of our worldwide demands while maximizing CO(2) utilization. In this sense, the Fischer-Tropsch (FT) technology provides a feasible option to render high value-added hydrocarbons. Alternative sources, such as biomass or coal, offer a real possibility to realize these purposes by making use of H(2)-deficient or CO(2)-rich syngas feeds. The management of such feeds ideally relies on the use of iron catalysts, which exhibit the unique ability to adjust the H(2)/CO molar ratio to an optimum value for hydrocarbon synthesis through the water-gas-shift reaction. Taking advantage of the emerging attention to hybrid FT-synthesis catalysts based on cobalt and their associated benefits, an overview of the current state of literature in the field of iron-based multifunctional catalysts is presented. Of particular interest is the use of zeolites in combination with a FT catalyst in a one-stage operation, herein named multifunctional, which offer key opportunities in the modification of desired product distributions and selectivity, to eventually overcome the quality limitations of the fuels prepared under intrinsic FT conditions. This review focuses on promising research activities addressing the conversion of syngas to liquid fuels mediated by iron-based multifunctional materials, highlights their preparation and properties, and discusses their implication and challenges in the area of carbon utilization through H(2)/CO(+CO(2)) mixtures.

Xylose-based oligosaccharides produced from xylan-rich hemicelluloses (xylo-oligomers) are carbohydrates with potential food and pharmaceutical uses. Autohydrolysis of lignocellulosic biomass is an efficient way to produce xylo-oligomers in a reasonable yield and a wide variety of compositions (anhydroarabinose/anhydroxylose and acetyl/anhydroxylose mass ratios). In this work, we develop a kinetic model for the autohydrolysis of xylan in lignocellulosic biomass that describes the yields of the different reaction products and explains the changes in the chemical composition of the xylo-oligomers due to reaction temperature and time. This model assumes that xylan is made up of three monomers (xylose, arabinose, and acetic acid) and that there are two xylan fractions with different compositions and reactivities toward hydrolysis. Both fractions are hydrolyzed to xylo-oligomers, which are hydrolyzed to xylose, arabinose, and acetic acid. Finally, monosaccharides dehydrate to furfural and degradation products. The model is validated with experimental data obtained for the autohydrolysis of corncobs in a batch reactor system at temperatures from 150 to 190 °C. The amount and composition of each xylan fraction, as well as the activation energies and frequency factors for all the reactions, are calculated from the experimental data. This model provides a satisfactory interpretation of the experimental data.