CO2 sorption-enhanced steam reforming of phenol using Ni-M/CaO-Ca12Al14O33 (M = Cu, Co, and Ce) as catalytic sorbents

In this study, two kinds of Ni/CaO-Ca12Al14O33 catalytic sorbents were synthesized by wet impregnation using different CaO-Ca12Al14O33 as supports, which were prepared via calcination hydration (CH) and sol-gel/loading (SL) methods. Sorption-enhanced steam reforming (SESR) for hydrogen production was investigated using phenol as a tar model compound in a laboratory-scale fixed bed reactor. The Ni/CaO-Ca12Al14O33(CH) exhibited a higher hydrogen production activity compared to Ni/CaO-Ca12Al14O33(SL). The optimum operation condition for SESR process was obtained as temperature of 650 degrees C with S/C ratio of 3.0. Under this condition, the maximum H-2 concentrations of 69.75% and 67.68% were achieved for Ni/CaO-Ca12Al14O33(CH) and Ni/CaO-Ca12Al14O33(SL), respectively. The corresponding H-2 yields were 1.61 L/g and 1.45 L/g. However, a rapid deactivation of the Ni/CaO-Ca12Al14O33 catalytic sorbents occurred during the cyclic tests. Thus, bimetallic catalytic sorbents, Ni-M/CaO-Ca12Al14O33 (M = Cu, Co, and Ce), were developed by introducing the guest metal oxides. Among the three bimetallic catalytic sorbents, Ni-Co/CaO-Ca12Al14O33(CH) had the greatest potential for hydrogen production due to the synergistic catalytic effect of Co and Ni. The maximum H-2 concentration of 82.23% and the maximum H-2 yield of 2.31 L/g at 650 degrees C with S/C = 3.0 were observed for Ni-Co/CaO-Ca12Al14O33(CH). During the cyclic tests, the slight decrease in the H-2 yield of Ni-Co/CaO-Ca12Al14O33(CH) was attributed to the decrease in the CO2 sorption capacity. The Ni-Ce/CaO-Ca12Al14O33(CH) showed a stable CO2 sorption/desorption ability, but the H-2 yield decreased sharply due to the sintering of Ni particles and carbon deposition. Although the CO2 sorption capacity of Ni-Cu/CaO-Ca12Al14O33(CH) was well below the other two, it exhibited excellent stability. The results suggest that Ni-Co/CaO-Ca12Al14O33 and Ni-Cu/CaO-Ca12Al14O33 catalytic sorbents have great potential for the steam reforming of tar.