Hydrogen production reactions from carbon feedstocks: fossil fuels and biomass.

A large number of studies can be found in the literature regarding the production of new catalysts for methanol steam reforming. This work summarizes the latest developments on catalysts for this application and is divided in two main groups: copper-based and group 8–10 metal-based catalysts. In each section, the strategies proposed by several authors to enhance the performance of the catalysts are described. An overall comparison between the two groups shows that copper-based catalysts are the most active ones, while the 8–10 group catalysts present better results in terms of thermal stability and long-term stability. Very promising results were reported for both groups, enhancing the value of methanol as a hydrogen carrier for fuel cell applications.

Catalysts for methanol steam reforming—A review

This review highlights various aspects of current palladium membrane research and serves as a comprehensive bibliography covering palladium membrane preparation methods and applications. There are many promising uses for palladium membranes, although widespread use of the available technologies is constrained primarily by the high cost of palladium, lack of durability due to hydrogen embrittlement, and susceptibility to fouling. Various researchers in the field are tackling these problems and fabricating thinner palladium alloy composite membranes that better withstand contaminantion and thermal cycling. What has been accomplished to address these issues and the directions presently being explored are discussed.

Innovations in palladium membrane research

A comparative study of fuels for on-board hydrogen production for fuel-cell-powered automobiles

Increasingly stringent legislation controls emissions from internal combustion engines to the point where alternative power sources for vehicles are necessary. The hydrogen fuel cell is one promising option, but the nature of the gas is such that the conversion of other fuels to hydrogen on board the vehicle is necessary. The conversion of methanol, methane, propane, and octane to hydrogen is reviewed. A combination of oxidation and steam reforming (indirect partial oxidation) or direct partial oxidation are the most promising processes. Indirect partial oxidation involves combustion of part of the fuel to produce sufficient heat to drive the endothermic steam reforming reaction. Direct partial oxidation is favored only at high temperatures and short residence times but is highly selective. However, indirect partial oxidation is shown to be the preferred process for all fuels. The product gases can be taken through a water–gas shift reactor, but still retain ∼2% carbon monoxide, which poisons fuel-cell ca...

Onboard fuel conversion for hydrogen-fuel-cell-driven vehicles

The rate of catalytic decomposition of methanol in the presence of steam has been studied using a commercial Girdler G66B CuO-ZnO low temperature shift catalyst from 150 to 250°C at atmospheric pressure. The mole ratio of steam to methanol was varied from 0 to 1.5, and the feed rates covered the range from 300 to 1400 kg s/mol. The data were successfully correlated using a simple reaction network involving CH3OH, H2O, CO and H2. A conventional reversible reaction rate equation was used which included a resistance term for site blockage by a CO surface complex. The methanol decomposition rate constants showed satisfactory Arrhenius behaviour with an activation energy of about 96 kJ/mole.



On a etudie la vitesse de decomposition catalytique du methanol en presence de vapeur d'eau, en employant un catalyseur commercial de la reaction du gaz a l'eau a basse temperature (150 a 250°C a la pression atmospherique) Girdler G66B CuO-ZnO. On a fait varier le rapport molaire vapeur d'eau/methanol de 0 a 1,5 et les vitesses d'alimentation ont varie de 300 a 1400 kg s/mol. On a obtenu une bonne correlation des resultats obtenus, en employant une serie simple d'etapes reactionnelles impliquant CH3OH, H2O, CO et H2. On a employe une equation classique pour la vitesse des reactions reversibles qui inclut un terme de resistance pour le blocage des sites par un complexe de surface du CO. Les constantes de vitesse de decomposition du methanol suivent bien la loi d'Arrhenius avec une energie d'activation d'environ 96 kJ/mole

Hydrogen production by the catalytic steam reforming of methanol: Part 2: Kinetics of methanol decomposition using girdler G66B catalyst

The thermodynamic equilibria involved in the catalytic steam reformation of methanol to produce hydrogen have been examined over the ranges of pressure 101–3040 kPa, temperature 400–700K and water to methanol feed ratio 1.5–0.67. Four models have been considered based upon possible reaction products and the equilibrium composition of each model calculated.

The presence of methane and carbon reduce the quantity and quality of hydrogen produced. The best condition for hydrogen production occurs at 500K in the model in which carbon (soot) and methane gas are excluded and where pressures are low, and water is in excess in the feed. To achieve these conditions in practice the reactions for methane formation, which is thermodynamically favoured, and the appearance of carbon (soot) must be inhibited.

Hydrogen production by the catalytic steam reforming of methanol part 1: The thermodynamics

The vaporization times of small (12 mg.) drops of a binary liquid on a flat plate were measured in the maximum (critical) heat flux region of boiling heat transfer. The binary system studied was water-1-pentanol, the mixture previously shown by other workers to exhibit the most pronounced concentration effect on critical heat flux. Evaporation curves are reported in the critical region for pure water, pure pentanol and a number of mixtures in the concentration range 1.0 to 2.5 weight % pentanol in water.



It was confirmed that drop lifetimes can be obtained in the critical heat flux region by comparatively simple techniques and that there is a concentration effect on drop lifetime that is very similar to that observed during critical heat flux boiling studies. A minimum drop lifetime is observed at 1.8 weight % pentanol in water, the same concentration at which maximum critical heat fluxes were obtained in pool boiling studies at one atmosphere by S. J. D. Van Stralen and co-workers.



On a mesure, dans la region du flux maximal (critique) de chaleur du transfert de chaleur a l'ebullition, les temps de vaporisation de petites gouttes (12 mg.) d'un liquide binaire sur une plaque plane. Le systeme binaire etudie a ete celui forme d'eau et du l-pentanol qui, comme l'ont indique d'autres chercheurs, presente l'effet de concentration le plus eleve sur le flux de chaleur critique. On rapporte des courbes d'evaporation dans la region critique dans le cas de l'eau pure, du pentanol pur et d'un certain nombre de melanges pour des concentrations (% en poids) de pentanol dans l'eau de 1.0 a 2.5%.



On a confirme qu'on pent obtenir les valeurs de la duree des gouttes, dans la region du flux critique de la chaleur, au moyen de methodes comparativement simples et qu'un effet de concentration s'exerce sur la duree des gouttes, lequel ressemble beaucoup a celui qu'on a observe durant les etudes du flux critique de la chaleur a l'ebullition. On a observe une duree minimale des gouttes lorsque le pourcentage en poids du pentanol dans l'eau etait 1.8; c'est la meme concentration que celle a laquelle S. J. D. Van Stralen et al. ont obtenu des flux maximaux et critiques de chaleur dans des etudes d'ebullition dans un bassin sous une pression d'une atmosphere.

The vaporization of small binary drops on a flat plate at maximum heat flux

The Kinetics and Mechanism of the Oxidation of Carbon Monoxide Over an Industrial Vanadium Oxide Catalyst

The chemisorption of oxygen on an industrial vanadium pentoxide/potassium sulphate catalyst has been studied in the temperature range 300-353°C by a gravimetric technique. Agreement of equilibrium data with the Langmuir and Freudlich equations is not entirely satisfactory. The kinetic measurements suggest that at least two mechanisms are involved in oxygen chemisorption under certain conditions. At low coverage Langmuir or Elovich kinetics are followed reasonably closely although a pressure dependence is apparent suggesting dissociation into oxygen atoms before a final chemisorbed state is reached. Diffusion is suggested as the possible ratedetermining process at higher coverage. Langmuir analysis of the kinetics as equilibrium is approached shows that an unexpected pressure dependence also exists in this region.



On a etudie par voie gravimetrique, a une echelle de temperatures comprises entre 300 et 353°C, la chemisorption de l'oxygene sur un catalyseur industriel forme de pentoxyde de vanadium et de sulfate de potassium. La concordance entre les resultats d'equilibre et les equations de Langmuir et de Freundlich n'est pas completement satisfaisante. Les mesures cinetiques semblent indiquer qu'au moins deux mecanismes entrent en jeu dans la chemisorption de l'oxygene dans certaines conditions. Pour un champ d'application faible, la chemisoroption se fait d'une maniere assez rapprochee de la cinetique de Langmuir ou d'Elovich, quoiqu'elle indique une dependance de la pression qui laisse croire qu'il se produit une dissociation en atonies d'oxygene avant que l'etat final de la chemisorption ne soit atteint. Il y a lieu de croire que la diffusion determine la vitesse de la chemisorption dans le cas d'un champ d'application plus considerable. L'analyse de la cinetique indique qu'il existe aussi dans ce secteur une dependance imprevue de la pression.

R. F. Mann

Papers

Hydrogen production by the catalytic steam reforming of methanol: Part 2: Kinetics of methanol decomposition using girdler G66B catalyst

Hydrogen production by the catalytic steam reforming of methanol part 1: The thermodynamics

The vaporization of small binary drops on a flat plate at maximum heat flux

The Kinetics and Mechanism of the Oxidation of Carbon Monoxide Over an Industrial Vanadium Oxide Catalyst

Kinetics and thermodynamics of oxygen chemisorption on an industrial vanadium oxide catalyst