Removal of Siloxane from Biogas By Adsorption on Mesoporous Aluminosilicate (UCT-15)

Biogas, which comes from anaerobic decomposition of organic waste, has a significant potential as a renewable energy source. However, the siloxanes in biogas will cause severe problems to gas engine during the combustion process by generating abrasive microcrystalline silica. Removal of siloxane from biogas by commonly-used microporous active carbon is difficult because of the relatively large size of siloxane molecule (~ 1 nm).  In this study, mesoporous aluminosilicates are investigated as adsorbents to remove octamethylcyclotetrasilxoane (D4). The mesoporous aluminosilicates are synthesized by sol-gel based inversed micelle method. Current work focuses on tuning the structural properties of the mesoporous aluminosilicates, such as surface area and total pore volume, by changing the amount of aluminum dopant and calcination heating rate, and the exploration of the effect of these two synthesis conditions on the adsorption capacity. The best adsorption capacities of D4 is on mesoporous aluminosilicate with Si:Al=5 and synthesized under 10 °C/min heating rate. The D4 adsorption capacity of the best mesoporous aluminosilicate is more than twice higher than that of commercial ZSM-5. The adsorption capacities of mesoporous aluminosilicates are linearly related to BET specific surface area and total pore volume. The adsorption mechanism of D4 on mesoporous aluminosilicates is very likely related to the surface hydroxyl group on the adsorbents, since polymerization of D4 on the adsorbent surface is observed.