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Hydrogen production from rice husk was carried out via a two-stage system combining CLG (calcium looping gasification) using Ca(OH) 2 adsorbent in a bubbling fluidized bed and catalytic reforming with Ce–Ni/γAl 2 O 3 catalyst in a connected fixed bed. The results show that the maximum H 2 concentration (69.16 vol%) and H 2 yield (11.86 mmol g−1 rice husk) are achieved at Ca/C (Ca(OH) 2 to carbon molar ratio) = 1.5, H 2 O/C (H 2 O to carbon molar ratio) = 1.5, T g (gasification temperature) = 500 °C, T c (catalytic temperature) = 800 °C. The supplementation of fresh Ca(OH) 2 at Ca/C of 0.5 during calcination helps to activate the regenerated CaO by hydration, maintaining its carbonation activity and CO 2 adsorption. Ce–Ni/γAl 2 O 3 catalyst promotes water gas shift (WGS), steam methane reforming (SMR), and C 2 –C 3 hydrocarbons reforming, also exhibits excellent activity stability to maintain H 2 concentration and H 2 yield above 67.21 vol% and 11.67 mmol g−1 rice husk , respectively, during 5 lifetime tests. • Staged catalytic gasification of rice husk in a fluidized bed for H 2 -rich gas. • Ca(OH) 2 adsorbent promotes WGS and hydrocarbons reforming at a moderate temperature. • Fresh Ca(OH) 2 supplement during calcination activates regenerated CaO by hydration. • Ce–Ni/γAl 2 O 3 catalyst promotes WGS, SMR, and C 2 –C 3 hydrocarbons reforming reactions. • Ce–Ni/γAl 2 O 3 catalyst shows excellent activity stability with low carbon deposition. [Display omitted] [ABSTRACT FROM AUTHOR]

A two-stage system involving alkaline thermal gasification of cellulose with Ca(OH) 2 sorbent and catalytic reforming with Ni/Fe dual-functional CaO based catalysts is proposed and applied to enhance H 2 production and in-situ CO 2 capture. The results show that the H 2 concentration is maximized at a considerably lower temperature (500 °C) than commercialized biomass gasification processes, reducing energy consumption. Sol-gel method is deemed better than impregnation method for its lower cost and higher-concentration H 2 production. Among the prepared catalysts, sol-NiCa catalyst exhibits the best performance in CO 2 absorption, resistance to carbon deposition, and cyclic stability, creating maximum H 2 concentration (79.22 vol%), H 2 yield (27.36 mmol g−1 cellulose), and H 2 conversion (57.61%). Introduction of Ni rather than Fe on the CaO based catalyst promotes steam methane reforming at moderate temperature range of 400–600 °C, generating low contents of CH 4 (5.38 vol%), CO 2 (4.82 vol%), and CO (10.58 vol%). [Display omitted] • A two-stage system involving alkaline thermal gasification and catalytic reforming. • Sol-gel shows higher-concentration H 2 production and lower cost than impregnation. • Introduction of Ni rather than Fe on CaO catalysts promotes SMR at 400–600 °C. • Sol-NiCa catalyst exhibits good carbon deposition resistance and cyclic stability. • Maximum H 2 concentration (79.22 vol%) is achieved at moderate temperature of 500 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-stage steam gasification and catalytic reforming of rice husk for H 2 -rich gas. • Ce 0.7 Ni 1 Ca 5 catalyst achieves 85.81 vol% H 2 with H 2 yield of 35.82 mmol g-1 biomass. • Ce 0.7 Ni 1 Ca 5 exhibits excellent cyclic stability and inhibition of carbon deposition. • High oxygen transport capacity of CeO 2 helps to promote WGS and SMR reactions. • CeO 2 prevents the sintering of NiO and CaO particles, stabilizing CO 2 sorption. Hydrogen-rich gas production from rice husk via steam gasification and catalytic reforming using CeO 2 -modified Ni-CaO sorption bifunctional catalysts synthesized by sol–gel method in a two-stage system was investigated. The results show that the Ce 0.7 Ni 1 Ca 5 catalyst achieves maximum H 2 concentration (85.81(±0.39) vol.%) and H 2 yield (35.82(±0.28) mmol g-1 biomass) under a condition of 500 °C, S/C (steam/carbon in biomass) molar ratio of 5, catalyst/biomass mass ratio of 2.5, producing the lowest content of CO 2 (3.62(±0.16) vol.%), CO (4.27(±0.11) vol.%), CH 4 (4.49(±0.18) vol.%), and C 2 -C 3 (1.81(±0.09) vol.%), correspondingly. Ce 0.7 Ni 1 Ca 5 also exhibits excellent cyclic stability in H 2 production, CO 2 sorption, and inhibition of carbon deposition. The H 2 concentration and H 2 yield remain above 81.88 vol% and 32.11 mmol g-1 biomass , respectively, and CO 2 emission keeps below 4.85 vol% during 10 cyclic tests. The carbon deposition of Ce 0.7 Ni 1 Ca 5 is only about 30% of that of Ni 1 Ca 5 after 10 cycles and hardly increased after 5 cycles. It is found that well-dispersed CeO 2 can effectively prevent the sintering of NiO and delay agglomeration of CaO species, stabilizing CaO carbonation and CO 2 sorption, and the strong Ni-O-Ce interaction induces the creation of oxygen vacancies that facilitate the fracture of O–H bonds of water for the formation of H 2. Furthermore, the high oxygen transport capacity of CeO 2 not only forms abundant mesopores structure to promote WGS and SMR reactions for enhancing H 2 production, but also contributes to reforming the carbon deposited on the catalyst surface by lowering the oxidation temperature of amorphous carbon containing low-molecular aromatic or aliphatic compounds with lower degree of graphitization. [ABSTRACT FROM AUTHOR]