Abstract
The mitigation of the CO inhibition effect in palladium membranes is necessary due to its significance in the efficiency of membrane reactors and hydrogen production systems. In this work, the hydrogen separation performance of a Pd and Pd/Ag membrane both of thickness 2 μm is investigated using a mixed gas with composition (H2 = 50%, CO = 28%, CO2 = 10%, CH4 = 8%, N2 = 4%) at temperature 623 - 873 K and pressure (0.05 - 0.4 bar) was investigated. The component gases CO and CO2 were observed to inhibit hydrogen permeation through the membrane and lead to deviations from Sievert’s law for n values 0.55 and 0.62 for the Pd membrane and unity for the Pd/Ag membrane. For the Pd/Ag membrane, the concentration of CO in the permeate stream was reduced as a result of the addition of Ag. The effect of the component gases to hydrogen permeation was observed to be lower for the Pd/Ag membrane. Annealing the membrane in hydrogen at high temperature decreased the inhibition effect and enhanced hydrogen permeation through the membrane.
Highlights
IntroductionThe future of the global energy system is hugely dependent on how the challenges posed by fossil fuels (energy security and environmental security) are ad-
Several studies were carried out on the inhibition effect of CO to hydrogen permeation in palladium membranes. Most of these studies were at temperatures below 400 ̊C, this work investigates this effect 450 ̊C which falls within the relevant temperature range for steam methane reforming (SMR) membrane reactors
The inhibition effect of CO on hydrogen permeation and separation through 2 μm Pd and Pd/Ag membranes has been investigated at temperatures between 523 K and 723 K
Summary
The future of the global energy system is hugely dependent on how the challenges posed by fossil fuels (energy security and environmental security) are ad-. The application of palladium membranes in membrane reactors is significant as high purity hydrogen (>99.99 vol%) is required for maximum efficiency of fuel cells and nuclear purposes. Hydrogen permeation through palladium membranes can be decribed through the process below [5] [6] [7]: 1) External mass transfer where the hydrogen molecules undergo internal diffusion from the bulk of the gas phase onto the membrane surface on the high pressure side. 5) The hydrogen atoms undergo reversible movement from the bulk metallic layer to the membrane surface. A challenge in hydrogen separation and purification from syngas stream using Pd-based membranes is the inhibition effect caused by some co-existing gases such as CO and CO2. CO is known to be a major inhibitor to hydrogen permeation in Pd-based membranes
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