Sorption-enhanced reaction process for glycerol-to-hydrogen conversion over cobalt catalyst supported on promoted hydrotalcites

New bi-functional materials comprising the reforming catalyst, cobalt, and the CO2-sorbent, hydrotalcite were used to produce pure hydrogen (H-2) from sorption-enhanced steam glycerol reforming (SESGR). Three promoters, calcium, copper and zinc, were used for modifying the properties of hydrotalcites. All materials were characterized using X-ray diffraction, nitrogen physisorption and electron microscopy techniques. They were found to be very proficient for glycerol-to-H-2 conversion in a fixed-bed reactor, even at low temperature (623-823 K). Copper-promoted materials were especially promising, due to longest duration of the pre-breakthrough stage (40 min) and highest H-2 content of the reformed gas (93.1%) at T = 823 K. Besides, their sorption capacity was the highest (1.1 mol CO2/kg sorbent) at T = 823 K. The effects of temperature, steam-to-carbon ratio in feed (S/C ratio) and gas hourly space velocity (GHSV) on the SESGR process were investigated. Durability tests over 20 cycles of adsorption and regeneration showed that materials promoted with calcium, copper and zinc were stable up to 8 (at 773 K), 11 and 5 cycles (at 823 K) correspondingly. The role of cobalt metal and cationic hydrotalcite promoters in the reforming pathway was elucidated. This insightful study will assist in improved H-2 production from renewably producible glycerol. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.