https://cmapspublic3.ihmc.us/rid=1N3976C22-12M3P49-9V/Holladay%20et%20al.%20-%202009%20-%20An%20overview%20of%20hydrogen%20production%20technologies.pdf

An overview of hydrogen production technologies

Periodic, self-consistent density functional theory (DFT-GGA) calculations are used to investigate the water gas shift reaction (WGSR) mechanism on Cu(111). The thermochemistry and activation energy barriers for all the elementary steps of the commonly accepted redox mechanism, involving complete water activation to atomic oxygen, are presented. Through our calculations, we identify carboxyl, a new reactive intermediate, which plays a central role in WGSR on Cu(111). The thermochemistry and activation energy barriers of the elementary steps of a new reaction path, involving carboxyl, are studied. A detailed DFT-based microkinetic model of experimental reaction rates, accounting for both the previous and the new WGSR mechanism show that, under relevant experimental conditions, (1) the carboxyl-mediated route is the dominant path, and (2) the initial hydrogen abstraction from water is the rate-limiting step. Formate is a stable “spectator” species, formed predominantly through CO2 hydrogenation. In addition...

On the mechanism of low-temperature water gas shift reaction on copper.

Catalytic partial oxidation of methane has been reviewed with an emphasis on the reaction mechanisms over transition metal catalysts. The thermodynamics and aspects related to heat and mass transport is also evaluated, and an extensive table on research contributions to methane partial oxidation over transition metal catalysts in the literature is provided. Presented are both theoretical and experimental evidence pointing to inherent differences in the reaction mechanism over transition metals. These differences are related to methane dissociation, binding site preferences, the stability of OH surface species, surface residence times of active species and contributions from lattice oxygen atoms and support species. Methane dissociation requires a reduced metal surface, but at elevated temperatures oxides of active species may be reduced by direct interaction with methane or from the reaction with H, H2, C or CO. The comparison of elementary reaction steps on Pt and Rh illustrates that a key factor to produce hydrogen as a primary product is a high activation energy barrier to the formation of OH. Another essential property for the formation of H2 and CO as primary products is a low surface coverage of intermediates, such that the probability of O–H, OH–H and CO–O interactions are reduced. The local concentrations of reactants and products change rapidly through the catalyst bed. This influences the reaction mechanisms, but the product composition is typically close to equilibrated at the bed exit temperature.

A review of catalytic partial oxidation of methane to synthesis gas with emphasis on reaction mechanisms over transition metal catalysts

The rapid development in recent years of the proton-exchange membrane (PEM) fuel cell technology has stimulated research in all areas of fuel processor catalysts for hydrogen generation. The principal aim is to develop more active catalytic systems that allow for the reduction in size and increase the efficiency of fuel processors. The overall selectivity in generating a low CO content hydrogen stream as needed by the PEM fuel cell catalyst is dependent on the efficiency of the catalysts in each segment of the fuel processor. This article reviews the advances achieved during the past few years in the development of catalytic materials for hydrogen generation through fuel reforming, 1 water-gas shift and carbon monoxide preferential oxidation, as used or aimed to be of use in fuel processing for PEM fuel cell systems.

Review of fuel processing catalysts for hydrogen production in PEM fuel cell systems

Review of hydrogen storage techniques for on board vehicle applications

Fuel cell powered electric cars using on-board methanol reforming to produce a hydrogen-rich gas represent a low-emissions
 alternative to gasoline internal combustion engines (ICE). In order to exceed the well-to-wheel efficiencies
 of 17% for the gasoline ICE, high-efficiency fuel cells and methanol reformers must be developed.
 Catalytic autothermal reforming of methanol offers advantages over endothermic steam-reforming
 and exothermic partial oxidation. Microreactor testing of copper-containing catalysts was carried out
 in the temperature range between 250 and 330°C showing nearly complete methanol conversion at 85% hydrogen yield.
 For the overall process a simplified model of the reaction network, consisting of the total oxidation of
 methanol, the reverse water-gas shift reaction, and the steam-reforming of methanol, is proposed. Individual kinetic measurements
 for the latter two reactions
 on a commercial Cu/ZnO/Al2O3 catalyst are presented.

Autothermal methanol reforming for hydrogen production in fuel cell applications

The catalytic partial oxidation (CPO) of methane in the presence of steam (low temperature catalytic partial oxidation, LTCPO) over noble metal catalysts was investigated The ‘‘dry’’ CPO over ruthenium and rhodium catalysts was studied by thermogravimetric analyses coupled with IR spectroscopy For CPO conditions, high CO selectivities at comparably low temperatures were observed for a rhodium/g-alumina catalyst (5% rhodium) and a 1% ruthenium/TiO2 catalyst giving evidence that a direct reaction mechanism is involved at low temperatures It was found that under CPO conditions at low temperatures (<450 8C) the catalysts are in an oxidised state, which is probably responsible for the formation of carbon dioxide At higher temperatures, the catalysts are in a reduced state The CO selectivity increases with the reduction of the catalyst Our results indicate that a direct CO formation mechanism is also possible for ruthenium/alumina catalysts The platinum catalysts studied in the LTCPO of methane were less active than rhodium and ruthenium catalysts and revealed a lower hydrogen yield It was found that the steam reforming activity of the ruthenium/alumina catalyst was reduced inhibited by ceria The long term stability (80 h) of a ruthenium catalyst for LTCPO of methane was demonstrated # 2005 Elsevier BV All rights reserved

Low temperature catalytic partial oxidation of methane for gas-to-liquids applications

Low-temperature catalytic partial oxidation of hydrocarbons (C1-C10) for hydrogen production

A process for generating methane from biomass has the following steps: (a) a biomass pulp is produced from the biomass by setting an optimum dry matter content, (b) the biomass pulp is put under pressure, (c) in order to liquefy the solid organic components of the biomass pulp, the biomass pulp is heated under pressure, (d) the thus pressurised and heated biomass pulp is further heated up to at least the critical temperature of the mixture, (e) solids deposited under pressure and increased temperature are separated from the remaining fluid phase, and (f) at least part of the remaining fluid phase is gasified in a reactor under pressure and increased temperature to form a methane-rich gas. This provides a highly efficient process because a large part of the substances which hinder catalytic gasification, in particular salts, can be separated from the mixture by precipitation in supercritical conditions. A high methane yield and a high reaction speed can thus be achieved for catalytic gasification, at the same time as a long service life of the catalyst.

Thanh-Binh Truong

Papers

Autothermal methanol reforming for hydrogen production in fuel cell applications

Low temperature catalytic partial oxidation of methane for gas-to-liquids applications

Low-temperature catalytic partial oxidation of hydrocarbons (C1-C10) for hydrogen production

Process for generating methane and/or methane hydrate from biomass

Catalytic reforming of gasoline to hydrogen: Kinetic investigation of deactivation processes