Abstract
One alternative for the storage and transport of hydrogen is blending a low amount of hydrogen (up to 15 or 20%) into existing natural gas grids. When demanded, hydrogen can be then separated, close to the end users using membranes. In this work, composite alumina carbon molecular sieves membranes (Al-CMSM) supported on tubular porous alumina have been prepared and characterized. Single gas permeation studies showed that the H2/CH4 separation properties at 30 °C are well above the Robeson limit of polymeric membranes. H2 permeation studies of the H2–CH4 mixture gases, containing 5–20% of H2 show that the H2 purity depends on the H2 content in the feed and the operating temperature. In the best scenario investigated in this work, for samples containing 10% of H2 with an inlet pressure of 7.5 bar and permeated pressure of 0.01 bar at 30 °C, the H2 purity obtained was 99.4%.
Highlights
The so-called hydrogen economy is based on the clean conversion of hydrogen to electricity, releasing water as the only by-product
The pores of the Al-Carbon Molecular Sieves Membranes (CMSMs) were partially open by heating the membrane under He, at 4 bar pressure difference (He was used because it does not adsorb on the pores and the permeation is higher than N2); the He flow increases with the temperature from 98 mL minÀ1 at 32 C to 137 mL minÀ1 at 100 C (Figure S1) due to the removal of some water adsorbed in the pores
Al-CMSM membranes carbonized at 500 C were successfully prepared
Summary
The so-called hydrogen economy is based on the clean conversion of hydrogen to electricity, releasing water as the only by-product. The centralized production of H2 requires storage, distribution and transportation infrastructures to deliver it to the end users, which result in a significant cost increase as these infrastructures are not existing This cost can be greatly reduced by blending H2 into the existing natural gas storage and distribution infrastructures [11]. The safety risk increased by blending H2 into natural gas pipeline systems is related to the H2 content in the gas mixtures, and this risk increase is acceptable for H2 addition up to 15e20% In this way, pure H2 can be delivered to the multiple customers by using separation technologies close to the end users. H2 separation by selective membranes is a promising technology for the recovery of H2 present in low concentrations in the feed For this application, membranes with high permeation flux and high selectivity, above the upper bound Robeson’s limit for polymeric membranes are required. Among all membranes proposed for this separation, Pd based membranes and Carbon Molecular Sieves Membranes (CMSMs) are good alternatives
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