Valorization of Coal Fly Ash as a Stabilizer for the Development of Ni/CaO-Based Bifunctional Material

Sorption-enhanced glycerol steam reforming (SEGSR) is considered as one of the promising processes for H-2 production by combining glycerol steam reforming with simultaneous CO2 capture in a single-unit operation. The key challenge for a successful SEGSR process is the selection of suitable high-temperature CO2 sorbents with high resistance to sintering. In the present work, an attempt was made to modify a CaO-based sorbent by adding different types of coal fly ash (FA1-FA12) to develop highly effective and economical CaO-based sorbents suitable for CO2 removal at high temperatures. Among the synthesized sorbents, the 90%CaO FA5 sorbent offered the most stable CO2 capture activity over 20 cycles, with a CO2 capture capacity of 0.58 g(cO2)/g(sorbent) at the 1st cycle and 0.45 g(co2)/g(sorbent) at the 20th cycle. This can be attributed to the relatively high amounts of SiO2 and mullite (inert materials) in FAS compared with those of the other FA-containing samples. The presence of these inert materials helps enhancing the sorbent stability by hindering their aggregation and sintering. This sorbent was then selected to synthesize a bifunctional catalyst sorbent material for H-2 production via SEGSR The 15%Ni-CaO-FA5 bifunctional material exhibited a stable H-2 purity of similar to 97% and a H-2 yield of 90% for 30 min (prebreakthrough) of the SEGSR reaction. These results highlight the high potential of FAS as a low-cost stabilizer for improving the stability of CaO-based sorbents.