Abstract
Water gas shift reaction of carbon monoxide (CO) with membrane reactors should be a promising method for hydrogen mass-production because of its high CO conversion, high hydrogen purity and low carbon dioxide emission. For developing such membrane reactors, we need hydrogen permselective membranes with high hydrogen permeance with order of 10−6 mol m−2 s−1 Pa−1 at 573 K and high steam durability. In this study, we have optimized the kind of substrates, precursors, vapor concentration, and chemical vapor deposition (CVD) time using the counter-diffusion CVD method for developing such membranes. The developed membrane prepared from hexamethyldisiloxane has a hydrogen permeance of 1.29 × 10−6 mol m−2 s−1 Pa−1 at 573 K and high steam durability. We also conducted water gas shift reactions with membrane reactors installed the developed silica membranes. The results indicated that reactions proceed efficiently with the conversion around 95–97%, hydrogen purity around 94%, and hydrogen recovery around 60% at space velocity (SV) 7000.
Highlights
Hydrogen energy is very attractive from the viewpoint of global warming prevention.Since hydrogen is a secondary energy, its production method is important
In many cases, the location of hydrogen production by renewable energy does not coincide with the location of hydrogen energy utilization
At present, the most common hydrogen production method is steam reforming of methane followed by water gas shift reaction of carbon monoxide
Summary
Hydrogen energy is very attractive from the viewpoint of global warming prevention. Since hydrogen is a secondary energy, its production method is important. An asymmetric substrate coated with γ-alumina was deposited with 0.885 mol m−3 HMDSO or a syringe pump (KDS-410, KD Scientific, Tokyo, Japan) in a nitrogen (200 mL min−1 ) carrier gas, to examine the effect of substrate. The influence of silica precursors, silica membranes were deposited to γ-alumina coated symmetric substrates with the precursor concentration around 0.85 mol m−3 (0.886 mol m−3 for HMDSO and 0.804 mol m−3 for TMOS) for 5 min as CVD time. Membrane gas permeation performance was evaluated at 773, 673, and 573 K using single-component gases of hydrogen, nitrogen by a bubble flow meter (SF 1U, Horiba Co., Kyoto, Japan).
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