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Chemical looping steam reforming (CLSR) of ethanol using oxygen carriers (OCs) for hydrogen production has been considered a highly efficient technology. In this study, NiO/MgAl 2 O 4 oxygen carriers (OCs) were employed for hydrogen production via CLSR with and without CaO sorbent for in-situ CO 2 removal (sorption enhanced chemical looping steam reforming, SE-CLSR). To find optimal reaction conditions of the CLSR process, including reforming temperatures, the catalyst mass, and the NiO loadings on hydrogen production performances were studied. The results reveal that the optimal temperature of OCs for hydrogen production is 650 °C. In addition, 96% hydrogen selectivity and a 'dead time' (the reduced time of OCs) less than 1 minute is obtained with the 1 g 20NiO/MgAl 2 O 4 catalysts. The superior catalytic activity of 20NiO/MgAl 2 O 4 is due to the maximal quantity of NiO loadings providing the most Ni active surface centers. High purity hydrogen is successfully produced via CLSR coupling with CaO sorbent in-situ CO 2 removal (SE-CLSR), and the breakthrough time of CaO is about 20 minutes under the condition that space velocity was 1.908 h−1. Stability CLSR experiments found that the hydrogen production and hydrogen selectivity decreased obviously from 207 mmol to 174 mmol and 95%–85% due to the inevitable OCs sintering and carbon deposition. Finally, stable hydrogen production with the purity of 89%∼87% and selectivity of 96%∼93% was obtained in the modified stability SE-CLSR experiments. [Display omitted] • High catalytic OCs were developed via the modified Pechi method. • 20NiO/MgAl 2 O 4 attained 96% H 2 selectivity and 1 minute 'dead time' in CLSR. • The breakthrough time of CaO was 20 minutes in SE-CLSR. • Stable H 2 yield with high purity was obtained in the long-term modified SE–CLR. [ABSTRACT FROM AUTHOR]

[Display omitted] • SECLSR proposed realizes CO 2 in-situ capture & utilization to H 2 and syngas. • Conversion of CO 2 from in-situ extraction of dolomite using MDR at 850 °C is feasible. • NiO/NiAl 2 O 4 of 15% NiO presented good activity and stability in SECLSR and MDR. • The process is no need for separating catalyst and sorbent for SECLSR. Hydrogen production from chemical looping steam reforming using an oxygen transport catalyst is definitely enhanced by CO 2 in-situ capture, which shifts the chemical equilibrium and reduces the energy demands. The utilization of CO 2 from this process as a reactant for chemicals and fuels could help to improve economic reasons and mitigate its impact on climate. In this study, we proposed a sorption-enhanced chemical looping steam reforming of glycerol to realize the synergetic capture and conversion of CO 2 in one integrated chemical looping hydrogen production process. The process is characterized to use the oxidized NiO/NiAl 2 O 4 as a steam reforming catalyst, the reduced NiO/NiAl 2 O 4 as a CO 2 -CH 4 dry reforming catalyst, and the inexpensive dolomite as a CO 2 sorbent. The surface carbon that would deactivate the catalyst is combusted by air after CO 2 -CH 4 dry reforming and the Ni on the catalyst is re-oxidized. The coupling of these different processes of chemical looping steam reforming, CO 2 in-situ capture, dolomite decomposition and CO 2 in-situ utilization, results in simultaneous generation of high purity hydrogen and syngas. The results demonstrated that hydrogen of above 92.5% was one-step generated and CO 2 was decreased to zero in the pre-CO 2 breakthrough periods. The reduced NiO/NiAl 2 O 4 catalysts favored the CO 2 -CH 4 dry reforming at 850 °C. The syngas of H 2 -to-CO molar ratios of 0.8–1.1 through the conversion of CO 2 from in-situ extraction of the absorbed CO 2 dolomite, was produced. The NiO/Al 2 O 4 with 15 wt% NiO gave the highest hydrogen and syngas yields, and maintained high performance for the proposed system. The catalysts and dolomite exhibited good stability with no obvious loss of activity in 10 cycles. [ABSTRACT FROM AUTHOR]

For the fixed-bed reactor configuration in the sorption-enhanced steam reforming process (SERP), solid mixture of catalyst and sorbent is stationary and alternatively exposed to reaction and regeneration conditions for multi-cycles by periodically switching the feed gases for enhanced hydrogen production with in-situ CO 2 removal. A NiO/NiAl 2 O 4 catalyst was synthesized by the co-precipitation method with rising pH technique and the crystalline spinel phase of NiAl 2 O 4 was formed under the calcination temperature of 900 °C. The catalyst was characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), thermo-gravimetric analysis (TGA), and N 2 adsorption–desorption. The non-stoichiometric thermodynamic calculation was carried out to determine the effects of temperature and in-situ CO 2 removal on the enhancement of hydrogen production by SERP from glycerol at 425–700 °C. The multi-cycles on reaction and regeneration for hydrogen production by SERP from glycerol were performed by NiO/NiAl 2 O 4 catalyst and CaO based sorbent in a fixed-bed reactor. The results showed that hydrogen production by SERP can be clearly divided into three periods, and the experimental gaseous products were compared with non-stoichiometric thermodynamic calculations. It is obvious that H 2 purity was greatly increased, and CO 2 , CO and CH 4 concentrations were reduced by in-situ CO 2 removal during the pre-breakthrough period. It is found that enhanced hydrogen production was mainly depended on in-situ CO 2 removal. The operation durations for producing high-purity hydrogen of more than 90% were decreased with the increase of the cycles. It may due to the decrease in the reactivity of CaO based sorbent after multi-cycles reaction and regeneration. [ABSTRACT FROM AUTHOR]