			Home About us Contact

Hydrogen Permeation (hydrogen + permeation)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Co-current and Countercurrent Configurations for a Membrane Dual Type Methanol Reactor

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2008
R. Rahimpour
Abstract A dynamic model for a membrane dual-type methanol reactor was developed in the presence of catalyst deactivation. This reactor is a shell and tube type where the first reactor is cooled with cooling water and the second one with feed synthesis gas. In this reactor system, the wall of the tubes in the gas-cooled reactor is covered with a palladium-silver membrane which is only permeable to hydrogen. Hydrogen can penetrate from the feed synthesis gas side into the reaction side due to the hydrogen partial pressure driving force. Hydrogen permeation through the membrane shifts the reaction towards the product side according to the thermodynamic equilibrium. Moreover, the performance of the reactor was investigated when the reaction gas side and feed gas side streams are continuously either co-current or countercurrent. Comparison between co-current and countercurrent mode in terms of temperature, activity, methanol production rate as well as permeation rate of hydrogen through the membrane shows that the reactor in co-current configuration operates with lower conversion and also lower permeation rate of hydrogen but with longer catalyst life than does the reactor in countercurrent configuration. [source]

Effect of metal-support interface on hydrogen permeation through palladium membranes

AICHE JOURNAL, Issue 3 2009
Ke Zhang
Abstract Thin palladium membranes of different thicknesses were prepared on sol-gel derived mesoporous ,-alumina/,-alumina and yttria-stabilized zirconia/,-alumina supports by a method combining sputter deposition and electroless plating. The effect of metal-support interface on hydrogen transport permeation properties was investigated by comparing hydrogen permeation data for these membranes measured under different conditions. Hydrogen permeation fluxes for the Pd/,-Al2O3/,-Al2O3 membranes are significantly smaller than those for the Pd/YSZ/,-Al2O3 membranes under similar conditions. As the palladium membrane thickness increases, the difference in permeation fluxes between these two groups of membranes decreases and the pressure exponent for permeation flux approaches 0.5 from 1. Analysis of the permeation data with a permeation model shows that both groups of membranes have similar hydrogen permeability for bulk diffusion, but the Pd/,-Al2O3/,-Al2O3 membranes exhibit a much lower surface reaction rate constant with higher activation energy, due possibly to the formation of Pd-Al alloy, than the Pd/YSZ/,-Al2O3 membranes. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Steam reforming of propane in a zirconia membrane reactor with a Rh-supported Ce0.15Zr0.85O2 catalyst

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009
K. Kusakabe
Abstract The steam reforming (SR) of propane for hydrogen production at 400,600 °C in a porous yttria-stabilized zirconia (YSZ) membrane reactor was investigated. The YSZ membrane was used as a hydrogen selective membrane. A Rh-supported Ce0.15Zr0.85O2 catalyst was packed in the membrane reactor because the catalyst was found to be the most suitable catalyst for the low-temperature SR of propane on the basis of the results obtained using a packed bed reactor. The conversion of propane in the membrane reactor was higher than that in a packed bed reactor due to the shift of equilibrium toward the hydrogen-producing side. In spite of relatively low permeation selectivity (ideal H2/CO selectivity = 9 at 100 °C), hydrogen permeation through the membrane caused an increase in the CO2 fraction and a decrease in the CO fraction in reformed gas. This indicates that the water-gas shift reaction was an important contributor in the product distribution in the membrane reactor. Meanwhile, the methane fraction remained largely unchanged, regardless of selective hydrogen permeation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]