Surface effects and CO/CO2 influence in the H2 permeation through a Pd–Ag membrane: A comprehensive model

Abstract

The permeability of a 0.175 mm thick Pd-Ag tubular membrane to pure H2 and binary mixtures of H2/CO or H2/CO2 was studied. The tests were performed in a wide range of temperature (523-723 K) and pressure (200-800 kPa).Pure H2-permeation through a dense metal membrane is described by the Sieverts' law. However, it was already found that the H2 permeation does not follow the Sieverts' law when other components are present in the feed and namely CO or CO2. In this work, it is proposed a new permeation model based on the Sieverts' law considering: i) the mass transfer resistance due to the surface effects and ii) the barrier effect due to the presence of either CO or CO2. The model was successfully validated against experimental data of hydrogen permeation for binary (H2/CO and H2/CO2) experiments for every working temperature and pressure.

A Comparison of the Inhibiting Effect of CO and CO2 to Hydrogen Permeation and n-Value in Pd and Pd/Ag Membranes Prepared on Alumina Support

“…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-dressed. These challenges are based on the need to address energy shortages, ensure environmental suatainability and make energy more affordable to the communities [1] [2]. The indefinite exploitation of fossil fuels for energy purposes is not sustainable as they cause environmental pollution through emission of greenhouse gases particularly CO 2 which necessitates global action to develop environmentally friendly and sustainable energy technologies [2].…”

“…These challenges are based on the need to address energy shortages, ensure environmental suatainability and make energy more affordable to the communities [1] [2]. The indefinite exploitation of fossil fuels for energy purposes is not sustainable as they cause environmental pollution through emission of greenhouse gases particularly CO 2 which necessitates global action to develop environmentally friendly and sustainable energy technologies [2]. Global efforts are ongoing on alternative and unconventional sources of energy to prepare the world towards the impending energy vacuum as oil and gas resources deplete and continue to cause environmental concerns.…”

“…The relevance of hydrogen as a reliable route for clean energy is increasing every day because it is renewable, environmentally friendly and affordable. The combustion of hydrogen produces only water vapour with a limited pollution to the environmental impact when produced thorugh renewable sources [2]. Hydrogen is currently widely used in several industries such as petroleum, steel, space, chemical and petrochemical industries but is expected to be increasingly more relevant in transportation and power generation sectors [2] [4] [5].…”

“…The combustion of hydrogen produces only water vapour with a limited pollution to the environmental impact when produced thorugh renewable sources [2]. Hydrogen is currently widely used in several industries such as petroleum, steel, space, chemical and petrochemical industries but is expected to be increasingly more relevant in transportation and power generation sectors [2] [4] [5]. Everyday, membrane reactors play an important role in shifting the quilibrium during water-gas shift reaction for conversion of CO to hydrogen through the steam methane reforming (SMR) process.…”

Changes in microstructures and hydrogen permeability of Nb30Hf35Co35 eutectic alloy membranes by annealing

“…Pd and its alloys are presently used as the hydrogen permeation membrane for purification of hydrogen gas [1,2]. However, since Pd is too expensive and a rare metal, much of the current research [3e7] on hydrogen permeable alloys is focused on Nb-based alloys containing less or no Pd, such as NbeTiNi [3,4], NbeTiCo [5] and NbeHfNi [6] etc.…”