Adsorption and thermal decomposition of H 2 S on Si(1 0 0)

Abstract Adsorption and thermal decomposition of H 2 S on Si(1 0 0)-2 Â 1 are studied by means of temperature-programmed desorption (TPD) and X-ray photoemission spectroscopy (XPS) with synchrotron radiation. The H 2 S molecule dissociates to form H and HS on the Si surface at adsorption temperature of 115 K. The Si(1 0 0)-2 Â 1 surface structure is conserved upon the adsorption of H 2 S due to bonding of dissociative H and HS on two Si atoms in a dimer without breaking the Si-Si dimer bond. H 2 and SiS are the only desorption products of thermal decomposition of H 2 S with peaks at 780 and 820 K, respectively. On the basis of TPD and XPS results, intermediates involved in decomposition of H 2 S and their adsorption configurations are proposed and discussed

Application of Flexible Micro Temperature Sensor in Oxidative Steam Reforming by a Methanol Micro Reformer

Advances in fuel cell applications reflect the ability of reformers to produce hydrogen. This work presents a flexible micro temperature sensor that is fabricated based on micro-electro-mechanical systems (MEMS) technology and integrated into a flat micro methanol reformer to observe the conditions inside that reformer. The micro temperature sensor has higher accuracy and sensitivity than a conventionally adopted thermocouple. Despite various micro temperature sensor applications, integrated micro reformers are still relatively new. This work proposes a novel method for integrating micro methanol reformers and micro temperature sensors, subsequently increasing the methanol conversion rate and the hydrogen production rate by varying the fuel supply rate and the water/methanol ratio. Importantly, the proposed micro temperature sensor adequately controls the interior temperature during oxidative steam reforming of methanol (OSRM), with the relevant parameters optimized as well

The Adsorption Isobar of Dioxygen on Rhodium Powders

Isobar oxidations of rhodium powders with dioxygen in the temperature range 77–473 K have been studied gravimetrically. The uptake of oxygen was found to increase with oxidation temperature. However, levelling off of the O/Rh s stoichiometry at a value of 1.0 was found between 232 K and 300 K, indicating monolayer chemisorption of oxygen on the rhodium surface. At higher temperatures, the stoichiometry increased above unity because of sublayer and bulk oxidations. Dioxygen chemisorption at 300 K was subsequently used to estimate the dispersion of rhodium catalysts assuming O/Rh s = 1.0, the value obtained agreeing well with that evaluated from measurements of the broadening of the X-ray diffraction line for a 10 wt.% Rh/Al 2 O 3 catalyst and for the modified deuterium uptake of a 1.5 wt.% Rh/Al 2 O 3 sample. Such agreements suggest that dioxygen chemisorption provides a direct and dependable method for estimating the particle size of supported rhodium catalysts over a wide dispersion range

Hydrogen Generation Using a CuO/ZnO-ZrO2 Nanocatalyst for Autothermal Reforming of Methanol in a Microchannel Reactor

In the present work, a microchannel reactor for autothermal reforming of methanol using a synthesized catalyst porous alumina support-CuO/ZnO mixed with ZrO2 sol washcoat has been developed and its fine structure and inner surface characterized. Experimentally, CuO/ZnO and alumina support with ZrO2 sol washcoat catalyst (catalyst slurries) nanoparticles is the catalytically active component of the microreactor. Catalyst slurries have been dried at 298 K for 5 h and then calcined at 623 K for 2 h to increase the surface area and specific pore structures of the washcoat catalyst. The surface area of BET N2 adsorption isotherms for the as-synthesized catalyst and catalyst/ZrO2 sol washcoat samples are 62 and 108 ± 2 m2g−1, respectively. The intensities of Cu content from XRD and XPS data indicate that Al2O3 with Cu species to form CuAl2O4. The EXAFS data reveals that the Cu species in washcoat samples have Cu-O bonding with a bond distance of 1.88 ± 0.02 Å and the coordination number is 3.46 ± 0.05, respectively. Moreover, a hydrogen production rate of 2.16 L h−1 is obtained and the corresponding methanol conversion is 98% at 543 K using the CuO/ZnO with ZrO2 sol washcoat catalyst