High-purity hydrogen production by sorption-enhanced methanol steam reforming over a combination of Cu–Zn–CeO2–ZrO2/MCM-41 catalyst and (Li–Na–K) NO3·MgO adsorbent

In this study, sorption-enhanced methanol steam reforming (SEMSR) was applied to generate high-purity hydrogen. The mesoporous MCM-41 as support and CuO, ZnO, CeO₂, ZrO₂ as active agents and promoters were employed for the catalyst preparation. In addition, (Li–Na–K) NO₃·MgO as a CO₂ adsorbent was prepared by the wet mixing method. The fresh and used catalysts were characterized by XRD, BET, FTIR, FESEM, TEM, H₂-TPR and TGA analyses. Also, the CO₂ sorbent was studied by XRD, BET, FESEM, TEM and TGA analyses before and after the reaction. The SEMSR performances of the synthesized catalyst and adsorbent were evaluated experimentally in a fixed-bed reactor. The effect of various conditions such as temperature, WHSV, feed molar ratio and sorbent/catalyst ratio were investigated. The best results were obtained at 300 °C, a feed molar ratio (water/methanol) of 2:1, a WHSV of 1.62 h^?1, and the sorbent/catalyst ratio of 8:1, which produced 99.8% hydrogen, 25% more than the hydrogen production during conventional methanol steam reforming. Moreover, the cyclic stability of the catalyst and the sorbent was studied for 10 cycles.     

Synthetic CaO-based sorbent for high-temperature CO2 capture in sorption-enhanced hydrogen production

Calcium precursor and surfactant addition on properties of synthetic alumina-containing CaO-based for CO₂ capture and for sorption-enhanced steam methane reforming process (SE-SMR) were investigated. Results showed that the sorbent derived from calcium d-gluconic acid (CG-AN) offered CO₂ sorption capacity of 0.38 g CO₂/g sorbent, which is greater than 0.17 g CO₂/g sorbent of the sorbent derived from calcium nitrate (CN-AN). Addition of CTAB surfactant during synthesis was found to enhance CO₂ sorption capacity for CG-AN but not for CN-AN sorbents. Stability tests of the modified sorbents for 10 cycles showed that CG-AN-CTAB provided higher CO₂ sorption capacity than CN-AN-CTAB for each corresponding cycle. Incorporation of CG-AN with Ni catalyst (Ni-CG-AN) using wet-mixing technique offered the longest pre-breakthrough period of 60 min for average maximum H₂ purity of 88% at 600 °C and a steam/methane molar ratio of 3.     

Experimental investigation of improved calcium-based CO2 sorbent and Co3O4/SiO2 oxygen carrier for clean production of hydrogen in sorption-enhanced chemical looping reforming

In this study, highly pure hydrogen is produced in sorption enhanced chemical looping steam methane reforming (SE-CLSMR) using cobalt-based oxygen carrier (OC) and cerium promoted CaO-based sorbent. In addition, the CO₂ removal from a gas stream at high temperatures is investigated via calcium looping process prior to SE-CLSMR process. The prepared samples are characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and energy dispersive X-ray spectroscopy (EDX) techniques. The effect of Ca/Ce molar ratio (100/0.00–0.91/0.09), sorption temperature (550–650 °C) and sorbent lifetime are studied to find the optimal sorbent. The characterization results show the uniform and orderly CeO₂ dispersed sorbent nanoparticles that notably improved the sorbent morphology compared with blank CaO. The sorption results revealed the negative effect of temperature on CO₂ uptake of all the samples. In addition, the CO₂ sorption evaluations indicate that the molar ratio of cerium to calcium plays a significant role in the stability of sorbent and improved the CO₂ sorption capacity significantly. The high CO₂ removal efficiency in the cerium modified sorbents could be due to decrease in diffusion resistance of CO₂ through the sorbent structure during the carbonation reaction. Furthermore, results show that the addition of cerium to the sorbent structure, effectively improves the thermal resistance of synthesis sorbents. The SE-CLSMR results showed that the H₂ purity could be increased up to about 95% considering Co₃O₄/SiO₂ oxygen carrier and cerium promoted calcium-based sorbent at relatively low temperature of 550 °C, which is comparable with 84% in CLR process.     

High purity H2 production from sorption enhanced bio-ethanol reforming via sol-gel-derived Ni–CaO–Al2O3 bi-functional materials

Catalytic steam reforming of renewable bio-oxygenates coupled with in-situ CO₂ capture is a promising option for sustainable H₂ production. The current work focuses on high purity H₂ production over Ni–CaO–Al₂O₃ bi-functional materials via sorption enhanced steam reforming of ethanol (SEESR). To ensure the uniform distribution of catalytic sites (Ni), adsorptive sites (CaO) and stabilizer (Al₂O₃) in the bi-functional materials, a citrate sol-gel synthetic route was employed. These materials were characterized by XRD, N₂ physical adsorption, SEM, TG and TPR techniques. It was revealed that the existence of CaO in bi-functional materials could not only in-situ remove CO₂, but also play the role of inhibiting the formation of harmful spinel phase. The stabilizing role of Al component against capacity decay was confirmed, whereas the presence of Ni ions had a negative effect on the cycle CO₂ uptake. The sample of Ni/Al/Ca-85.5 possessed large specific surface area, abundant porosity with fluffy morphology, and thereby, exhibited the best CO₂ sorption capacity during 20 carbonation/calcination cycles. The highest H₂ concentration of 96% was obtained through the SEESR during the pre-breakthrough period when the Ni/Al/Ca-85.5 was employed. Over the optimized bi-functional material, the effect of operating conditions on the SEESR was investigated and the results indicated that temperature of 600 °C, reaction liquid space velocity of 0.05 ml/min and steam/ethanol ratio of 4 were the suitable conditions. After 10 cycles, the bi-functional material of Ni/Al/Ca-85.5 also showed the best performance, with a H₂ purity of about 90% and pre-breakthrough time of 18 min, conforming the high potential of this material for SEESR process.     

Sorption enhanced steam reforming of ethanol for hydrogen production,over Mg/Al hydrotalcites modified with K

Sorption-enhanced ethanol steam reforming is an interesting alternative, to produce high purity H₂. In this study, potassium promoted hydrotalcites are compared for sorption-enhanced ethanol steam reforming reaction under cyclic operation, performing sorbent regeneration at reaction temperature which is a great advantage to reduce process energy requirements. It is found that potassium promoted hydrotalcites have higher CO₂ sorption capacity compared to unpromoted ones, due to the higher concentration of intermediate and strong basic sites. The hydrotalcite modified with 15 wt% potassium shows the best performance on multicyclic CO₂ sorption-desorption (sorption capacity = 0.167 mol_CO2/kgsorbent). Therefore, there is an optimum loading of potassium, for which the opposite effects of reduction in surface area and enhanced basicity are balanced. Finally, potassium promoted hydrotalcites are tested under cyclical ethanol reforming process with simultaneous adsorption of CO₂ followed by regeneration in N₂ at reaction temperature (500 °C). At short reaction times (<5 min), H₂ purities higher than 95% are achieved, with CO₂ purities near 0%.     

Sorption enhanced steam methane reforming by Ni–CaO materials supported on mayenite

Sorption enhanced steam methane reforming (SESMR), i.e. SMR with in situ CO₂-sorption, can lead to a sustainable and economical exploiting of natural gas for hydrogen production, with high purity and simultaneous sequestration of greenhouse gases. CaO-mayenite CO₂-sorbents, Ni-mayenite SMR catalysts and Ni–CaO-mayenite combined sorbent catalyst materials (CSCM) for SESMR were synthesized by wet mixing and wet impregnation methods, and characterized by means of XRD, BET/BJH, SEM/EDS, and TPR. For CSCM, an influence of CaO load on textural and Ni reducibility properties was recorded. Materials sorption capacity was measured in multicycles sorption/regeneration TGA tests: it always underwent a stabilization with cycle number increase. Reforming tests in micro-reactor scale were performed on 3 wt% to 10 wt% Ni-mayenite and selected CSCM: all Ni-mayenite always shown good performances, while for CSCM a detrimental role of CaO load on Ni catalytic activity was evidenced.     

Effect of Ni precursor salts on Ni-mayenite catalysts for steam methane reforming and on Ni-CaO-mayenite materials for sorption enhanced steam methane reforming

In view of climate change containment, sorption enhanced steam methane reforming (SESMR) appears as an interesting production route for H₂ with the additional advantage of CO₂ capture application performed by high-temperature solid sorbents. CaO is largely employed as CO₂ sorbent because of its low-cost mineralized forms (limestone and dolomite), of its high sorption capacity in the high temperature range compatible with steam methane reforming (SMR). Many recent studies have proposed purposely synthesized Ni-based reforming catalysts, used with high-temperature CO₂ solid sorbents, or combined sorbent-catalyst materials (CSCM). For this last purpose, we studied the effect of Ni salt precursor (Ni nitrate hexahydrate or Ni acetate tetrahydrate) on properties and reactivity of Ni-mayenite catalysts or Ni-CaO-mayenite CSCM, synthesized by an already validated sequence of wet mixing (for sorbents synthesis) and wet impregnation (for catalysts and CSCM synthesis) methods. Although Ni acetate tetrahydrate was often reported as the best choice to improve textural properties, our study identified Ni nitrate hexahydrate as a definitely more suitable precursor than Ni acetate tetrahydrate in the purpose of developing efficient materials for SESMR. The dissimilar behaviors observed in reforming reactivity are related and explained by the differences in textural properties, Ni species dispersion, and reducibility.     

Catalytic and sorbent materials based on mayenite for sorption enhanced steam methane reforming with different packed-bed configurations

An experimental study was performed on sorption enhanced steam methane reforming (SESMR) by Ni-mayenite reforming catalyst and CaO-mayenite CO₂-sorbents with several CaO contents. Materials were synthesized, characterized (by XRD, BET and BJH methods, TPR) and tested in a micro-reactor, comparing two configurations: two separated, consequential packed-beds and the more usual raw mixing. Ni-mayenite always allowed a high, stable CH₄ conversion (>93%). A generalized direct effect from CO₂ capture emerged on water gas shift reaction extent, while enhancement of methane conversion took place only in raw mixing.In practical applications, investigated materials are bound to face alternatively reforming and sorbent regeneration conditions: an automated bench-scale system was used to perform 205 SESMR/regeneration cycles, with separate beds of Ni-mayenite and CaO-mayenite (30 wt% free-CaO), proving good activity and stability throughout cycles (stable CH₄ conversion > 95%, pre-breakthrough CO₂ concentration < 3 vol% dry, dilution-free).     

Sodium doping of Pt/m-ZrO2 promotes C–C scission and decarboxylation during ethanol steam reforming

The effect that sodium has on Pt/m-ZrO₂ catalyst was investigated during ethanol steam reforming (ESR). Sodium doping decreases the catalytic activity, but significantly increases CO₂ selectivity, providing a means of improving H₂ selectivity. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results suggest that acetate species are intermediates in the reaction and that their decomposition can follow different routes depending on the catalyst formulation. When Pt/m-ZrO₂ is promoted by sodium, decarboxylation is the favored route: forward decomposition of acetate at lower temperatures yields essentially methane and adsorbed carbonate, further decomposing to carbon dioxide. At higher temperature, the methane precursor can be intercepted by the metal for further steam reforming or a separate methane steam reforming catalyst can be used downstream. Decarbonylation is instead favored for the unpromoted catalyst; decarbonylation tends to lower the H₂ selectivity of the overall process. Finally, the addition of sodium promotes C–C scission as methane formation is detected at lower temperature by DRIFTS and TPD-MS of ethanol in steam. This is analogous to formate C–H bond breaking in methanol steam reforming, steam-assisted formic acid decomposition, and water-gas shift reactions. In catalytic testing of ESR utilizing a tubular reactor at low temperatures (where steam reforming of CH₄ is limited), methane and CO₂ selectivities are higher with the Na-promoted catalyst than with the unpromoted catalyst. Thus, promotion of the forward decomposition of acetate route by Na addition is confirmed.     

Continuous sorption-enhanced steam reforming of glycerol to high-purity hydrogen production

In this study, the continuous sorption-enhanced steam reforming of glycerol to high-purity hydrogen production by a simultaneous flow concept of catalyst and sorbent for reaction and regeneration using two moving-bed reactors has been evaluated experimentally. A Ni-based catalyst (NiO/NiAl₂O₄) and a lime sorbent (CaO) were used for glycerol steam reforming with and without in-situ CO₂ removal at 500 °C and 600 °C. The simultaneous regeneration of catalyst and sorbent was carried out with the mixture gas of N₂ and steam at 900 °C. The product gases were measured by a GC gas analyzer. It is obvious that the amounts of CO₂, CO and CH₄ were reduced in the sorption-enhanced steam reforming of glycerol, and the H₂ concentration is greatly increased in the pre-CO₂ breakthrough periods within 10 min both 500 °C and 600 °C. The extended time of operation for high-purity hydrogen production and CO₂ capture was obtained by the continuous sorption-enhanced steam reforming of glycerol. High-purity H₂ products of 93.9% and 96.1% were produced at 500 °C and 600 °C and very small amounts of CO₂, CH₄ and CO were formed. The decay in activity during the continuous reaction-regeneration of catalyst and sorbent was not observed.     

Bifunctional Ni–CaO catalysts modified with CeO2 and inert Ca12Al14O33 for sorption-enhanced steam reforming of ethanol

In this work, sorption-enhanced steam reforming of ethanol (SE-SRE) process was studied using Ni–CaO-based bifunctional catalysts modified with Ca₁₂Al₁₄O₃₃ (mayenite) and CeO₂. The CaO and CaO/Ca₁₂Al₁₄O₃₃ sorbents were synthesized by a sol-gel method and, subsequently, CeO₂ and Ni were added by the incipient wetness impregnation method. These materials were characterized by BET surface area, thermogravimetric analysis (TGA), in situ X-ray diffraction (XRD), and in situ X-ray absorption near edge structuare (XANES). In addition, the catalysts were tested on 10 cycles of SE-SRE reaction and regeneration. In general, the characterization results revealed an inverse relationship between average crystallite size of CaO and CO₂ sorption capacity. By the in situ XRD/XANES, the addition of the mayenite reduced by half the average crystallite size of CaO and increased the interaction between support and active phase. As a consequence, the catalyst containing mayenite (NiCaAl) showed the best CO₂ capture uptake and stability, which could be justified mitigation of the CaO sintering effect by the inert material presence. Great stability was also observed in the catalytic tests, since the duration of the pre-breakthrough stage for NiCaAl and for the catalyst containing maynite and ceria (NiCaAlCe) remained constant over the reaction cycles. In terms of hydrogen production, NiCaAl catalyst showed the highest H₂ molar fraction during the pre- (90%) and post-breakthrough. The CeO₂ addition slightly favored the methane formation, although did not bring significant benefits in the CO₂ capture and catalytic performance. Therefore, NiCaAl showed the best CO₂ capture capacity and stability, which led to the best SE-SRE performance.     

A novel catalyst–sorbent system for an efficient H2 production with in-situ CO2 capture

This paper presents an experimental investigation for an improved process of sorption-enhanced steam reforming of methane in an admixture fixed bed reactor. A highly active Rh/Ce_αZr_1−αO₂ catalyst and K₂CO₃-promoted hydrotalcite are utilized as novel catalyst/sorbent materials for an efficient H₂ production with in situ CO₂ capture at low temperature (450–500 °C). The process performance is demonstrated in response to temperature (400–500 °C), pressure (1.5–6.0 bar), and steam/carbon ratio (3–6). Thus, direct production of high H₂ purity and fuel conversion >99% is achieved with low level of carbon oxides impurities (<100 ppm). A maximum enhancement of 162% in CH₄ conversion is obtained at a temperature of 450 °C and a pressure of 6 bar using a steam/carbon molar ratio of 4. The high catalyst activity of Rh yields an enhanced CH₄ conversion using much lower catalyst/sorbent bed composition and much smaller reactor size than Ni-based sorption enhanced processes at low temperature. The cyclic stability of the process is demonstrated over a series of 30 sorption/desorption cycles. The sorbent exhibited a stable performance in terms of the CO₂ working sorption capacity and the corresponding CH₄ conversion obtained in the sorption enhanced process. The process showed a good thermal stability in the temperature range of 400–500 °C. The effects of the sorbent regeneration time and the purge stream humidity on the achieved CH₄ conversion are also studied. Using steam purge is beneficial for high degree of CO₂ recovery from the sorbent.     

H2S effect on dry reforming of biogas for syngas production

The effect of hydrogen sulfide (H₂S) on dry reforming of biogas for syngas production was studied both experimentally and theoretically. In the experimental work, the H₂S effect on Ni‐based catalyst activity was examined for reaction temperatures ranging from 600°C to 800°C. It was found that the presence of H₂S deactivated the Ni‐based catalysts significantly because of sulfur poisoning. Although bimetallic Pt‐Ni catalyst has better performance compared with monometallic Ni catalyst, deactivation was still found. The time‐on‐stream measured data also indicated that sulfur‐poisoned catalyst can be regenerated at high reaction temperatures. In the theoretical work, a thermodynamic equilibrium model was used to analyze the H₂S removal effect in dry reforming of H₂S‐contained biogas. Calcium oxide (CaO) and calcium carbonate (CaCO₃) were used as the H₂S sorbent. The results indicated that H₂S removal depends on the initial H₂S concentration and reaction temperature for both sorbents. Although CO₂ was also removed by CaO, the results from equilibrium analysis indicated that the dry reforming reaction in the presence of CaO was feasible similar to the sorption enhanced water‐gas shift and steam‐methane reforming reactions. The simulation results also indicated that CaO was a more preferable H₂S sorbent than CaCO₃ because syngas with an H₂/CO ratio closer to 2 can be produced and requires lower heat duty.     

Transient reaction phenomena of sorption-enhanced steam methane reforming in a fixed-bed reactor

The transient chemical reaction phenomena of the sorption-enhanced steam methane reforming (SE-SMR) by using Ni/Al₂O₃ catalyst and CaO sorbent in a tubular fixed-bed reactor were numerically investigated by an experimentally verified unsteady 2D model. Four chemical reactions are involved in SE-SMR including steam reforming (SR), water gas shift (WGS), global steam reforming (GSR), and CO₂ sorption. The reaction process in time is divided into period 1, transient period, and period 2. The high-purity H₂ is produced in period 1 which is defined as the outlet molar fractions of H₂ ≥ 90% and CO ≤ 1% (dry basis) in this work. In the first half of period 1, the endothermic reaction rates of SR and GSR are dominant in the entrance region of catalyst/sorbent bed. The WGS and CO₂ sorption reactions are triggered by SR and GSR reactions. The heat transfer from the wall plays an important role. Higher CaO conversion, temperature, and reaction rates appear first near the wall region, then they gradually expand to the central region.In the second half of period 1, a sharp wave-shaped curve of strong CO₂ sorption reaction occurred in downstream becomes dominant and it moves to downstream almost at a constant speed, as time progresses. The peak value of the CO₂ sorption reaction is more than twice larger than that of SR or WGS. The SR and WGS reaction rates are significantly enhanced by CO₂ sorption reaction. The great sorption, WGS, and SR reactions result in a high-purity H₂ production with the outlet molar fractions of 95.8% H₂, 0.998% CO, and 0.73% CO₂ at the end of period 1, based on the parameters used in this work such as reactor temperature of 600 °C. The maximum CaO conversion is about 76% in end of period 1 and the average CaO conversion in the reactor is 51%. The 2D distributions of CaO conversion, temperature, and reaction rates are also presented and discussed.     

Rh promoted and ZrO2/Al2O3 supported Ni/Co based catalysts: High activity for CO2 reforming,steam–CO2 reforming and oxy–CO2 reforming of CH4

Ni (2.5 wt%) and Co (2.5 wt%) supported over ZrO₂/Al₂O₃ were prepared by following a hydrolytic co-precipitation method. The synthesized catalysts were further promoted by Rh incorporation (0.01–1.00 wt%) and tested for their catalytic performance for dry CO₂ reforming, combined steam–CO₂ reforming and oxy–CO₂ reforming of methane for production of syngas. The catalysts were characterized by using N₂ physical adsorption, XRD, H₂–TPR, SEM, CO₂–TPD, NH₃–TPD, TEM and TGA. The results revealed that ZrO₂ phase was in crystalline form in the catalysts along with amorphous Al oxides. Ni and Co were confirmed to be in their respective spinel phases that were reducible to metallic form at 800 °C under H₂. Ni and Co were well dispersed with their nano-crystalline nature. The catalyst with 0.2% loading of Rh showed superior performance in the studied reactions for reforming of methane. This catalyst also showed good coke resistance ability for dry CO₂ reforming reaction with 3.8 wt% of carbon formation during the reaction as compared to 11.6 wt% carbon formation over the catalyst without Rh. The catalyst performance was stable throughout the reaction time for CH₄ conversions, irrespective of carbon formation with slight decline (～1%) in CO₂ conversion. For dry CO₂ reforming reaction, this catalyst showed good conversion for both CH₄ and CO₂ (67.6% and 71.8% respectively) with a H₂/CO ratio of 0.84, while for the Oxy-CO₂ reforming reaction, the activity was superior with CH₄ and CO₂ conversions (73.7% and 83.8% respectively) and H₂/CO ratio of 1.05.     

Numerical studies of sorption-enhanced glycerol steam reforming in a fluidized bed membrane reactor at low temperature

In order to improve the hydrogen production efficiency by glycerol steam reforming, a membrane-assisted fluidized bed reactor with carbon dioxide sorption is developed to enhance the reforming process. Low-temperature operation in a membrane reactor is necessary considering the thermal stability of membrane. In this work, the sorption-enhanced glycerol steam reforming process in a fluidized bed membrane reactor under the condition of low temperature is numerically investigated, where the hydrotalcite is employed as CO₂ sorbents. The impact of operating pressure on the reforming performance is further evaluated. The results demonstrate that the integration of membrane hydrogen separation and CO₂ sorption can effectively enhance the low-temperature glycerol reforming performance. The fuel conversion above 95% can be achieved under an elevated pressure.     

High hydrogen yield and purity from palm empty fruit bunch and pine pyrolysis oils

The benefits of CO₂ sorption enhanced steam reforming using calcined dolomite were demonstrated for the production of hydrogen from highly oxygenated pyrolysis oils of the agricultural waste palm empty fruit bunches (PEFB) and pine wood. At 1 atm in a down-flow packed bed reactor at 600 °C, the best molar steam to carbon ratios were between 2 and 3 using a Ni catalyst. After incorporating steam-activated calcined dolomite as the CO₂ sorbent in the reactor bed, the H₂ yield from the moisture free PEFB oil increased from 9.5 to 10.4 wt.% while that of the pine oil increased from 9.9 to 13.9 wt.%. The hydrogen purity also rose from 68 to 96% and from 54 to 87% for the PEFB and pine oils respectively, demonstrating very substantial sorption enhancement effects.     

Preparation and characterization of PEI-loaded MCM-41 for CO2 capture

MCM-41, a molecular sieve, was prepared using tetraethoxysilane and cetyltrimethylammonium bromide and used as an effective adsorbent for CO₂. By using the wet impregnation method, various weights of poly(ethyleneimine) (PEI) were modified on mesoporous silicate MCM-41 for increasing the CO₂-adsorption capacity. The samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption/desorption isotherms. Thermal gravimetric analysis (TGA) was conducted to investigate the CO₂ capture behaviors. PEI was successfully dispersed into the channels of MCM-41, shifting the (110) diffraction peaks in the XRD patterns. The specific surface area and total pore volume of the PEI-loaded MCM-41 adsorbent decreased when the weight of PEI loading increased. From the results, it was concluded that PEI loading influences the CO₂ capture performance, resulting from the enhancement of the basic functional groups on MCM-41.     

Performance comparison among different multifunctional reactors operated under energy self-sufficiency for sustainable hydrogen production from ethanol

Four ethanol-derived hydrogen production processes including conventional ethanol steam reforming (ESR), sorption enhanced steam reforming (SESR), chemical looping reforming (CLR) and sorption enhanced chemical looping reforming (SECLR) were simulated on the basis of energy self-sufficiency, i.e. process energy requirement supplied by burning some of the produced hydrogen. The process performances in terms of hydrogen productivity, hydrogen purity, ethanol conversion, CO₂ capture ability and thermal efficiency were compared at their maximized net hydrogen. The simulation results showed that the sorption enhanced processes yield better performances than the conventional ESR and CLR because their in situ CO₂ sorption increases hydrogen production and provides heat from the sorption reaction. SECLR is the most promising process as it offers the highest net hydrogen with high-purity hydrogen at low energy requirement. Only 12.5% of the produced hydrogen was diverted into combustion to fulfill the process's energy requirement. The thermal efficiency of SECLR was evaluated at 86% at its optimal condition.     

Chemical looping steam reforming of ethanol without and with in-situ CO2 capture

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/MgAl₂O₄ oxygen carriers (OCs) were employed for hydrogen production via CLSR with and without CaO sorbent for in-situ CO₂ 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/MgAl₂O₄ catalysts. The superior catalytic activity of 20NiO/MgAl₂O₄ 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 CO₂ 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.