Sorption Enhanced Steam Reforming Research Articles

Embedding Ni in Ni–Al Mixed-Metal Alkoxide for the Synthesis of Efficient Coking Resistant Ni–CaO-Based Catalyst-Sorbent Bifunctional Materials for Sorption-Enhanced Steam Reforming of Glycerol

The sorption-enhanced steam reforming of glycerol (SESRG) is a sustainable approach to produce high-purity hydrogen in a single step by valorizing waste raw material. Fabricating Ni–CaO-based catal...

Pd-promoted Ni-Ca-Al bi-functional catalyst for integrated sorption-enhanced steam reforming of glycerol and methane reforming of carbonate

The integration process of sorption-enhanced steam reforming (SESR) reaction and methane reforming (MR) of carbonates provides a promising way to produce high-purity H2 without CO2 emission. However, the huge different reaction temperature of SESR (~550 °C) and MR (>750 °C) hinders this coupling process. Herein, we report that the Pd-promoted Ni-Ca-Al bi-functional catalyst can lower the MR reaction temperature to 650 °C by enhancing CH4 decomposition activity to provide H2 molecules or atoms. The low regeneration temperature significantly improves the stability of SESR of glycerol (SESRG) reaction with only 8% increase in Ni particle size and 25% decrease of sorption-enhanced effect after 10 SESRG-MR cycles. Thanks to the high stability of the catalyst, 98.3% hydrogen-enriched stream and syngas with RH2/CO < 3 are co-produced in ten cyclic tests. Therefore, lowering the regeneration temperature can simultaneously weaken the thermal-swing operation and improve the stability of the catalyst during the SESR-MR reaction.

Sorption enhanced steam reforming of ethanol over Ni-based catalyst coupling with high-performance CaO pellets

Coupling with the conventional Ni/Al2O3 catalyst, novel CaO-based porous spherical sorbents (made by a new molding technique) were examined in the sorption enhanced steam reforming of ethanol process (SESRE) to improve the H2 quality. The cyclic H2 quality was monitored, and the catalytic properties of the catalyst for steam reforming of ethanol as well as the CO2 capture capacity of the modeled sorbents were studied in details. Besides, thermodynamic modelling has been done by Gibbs free energy minimization method to simulate the sorption enhancing effect and screen the optimized reaction conditions to yield high-quality H2; furthermore, the relative H2O consumption versus ethanol during the reforming process was further discussed. The results showed that the sorption enhanced steam reforming process was an effective and flexible way to produce high-quality H2 around 600 °C, and subsequently the simulated sorption enhanced process was validated experimentally. In addition, the properties of the catalyst and modeled sorbents were analyzed by N2 physisorption, SEM, EDS-Mapping, H2-TPR, XRD, Raman, In-situ DRIFTS and so on. A high purity H2 was yielded during the pre-breakthrough stages, in especial that process enhanced by the modeled sorbents templated by cellules (CaOS-C5 pellets), which illustrated a good prospect of SESRE process. With the CaOS-C5 pellets, during the 10th SESRE process, H2 could be constantly produced with purity above 90% within at least 15 min of SESRE process. The modeled CaO spheres greatly boosted the concentration and output of H2. Over the repeated cycles, the Ni/Al2O3 catalyst and the modeled sorbents displayed well stability over the long-term reactions, which illustrated a good prospect of SESRE process enhanced by these new spherical sorbents.

Production of high-purity hydrogen from paper recycling black liquor via sorption enhanced steam reforming

Environmentally friendly and energy saving treatment of black liquor (BL), a massively produced waste in Kraft papermaking process, still remains a big challenge. Here, by adopting a NiCaOCa12Al14O33 bifunctional catalyst derived from hydrotalcite-like materials, we demonstrate the feasibility of producing high-purity H2 (∼96%) with 0.9 mol H2 mol−1 C yield via the sorption enhanced steam reforming (SESR) of BL. The SESRBL performance in terms of H2 production maintained stable for 5 cycles, but declined from the 6th cycle. XRD, Raman spectroscopy, elemental analysis and energy dispersive techniques were employed to rationalize the deactivation of the catalyst. It was revealed that gradual sintering and agglomeration of Ni and CaO and associated coking played important roles in catalyst deactivation and performance degradation of SESRBL, while deposition of Na and K from the BL might also be responsible for the declined performance. On the other hand, it was demonstrated that the SESRBL process could effectively reduce the emission of sulfur species by storing it as CaSO3. Our results highlight a promising alternative for BL treatment and H2 production, thereby being beneficial for pollution control and environment governance in the context of mitigation of climate change.

On the effect of biogas composition on the H2 production by sorption enhanced steam reforming (SESR)

Abstract Biogas is a valuable source of renewable energy produced from biodegradable organic materials via anaerobic digestion. The production of H2 by sorption enhanced steam reforming (SESR) of biogas has been studied thermodynamic and experimentally. A Pd/Ni–Co catalyst and dolomite as CO2 sorbent were used. The effect of biogas composition (CH4/CO2 vol%) on the process was evaluated at 600 and 650 °C in a fluidized bed reactor using biogas CO2 concentrations of 5–50 vol%. During conventional biogas steam reforming (SR), high CH4 partial pressures in the feed favor the process, producing high H2 concentrations. During biogas SESR, CO2 was effectively removed from the gas phase by the sorbent for all the biogas compositions, and it did not alter the process compared to pure methane. Steam methane reforming (SMR) and water-gas shift (WGS), together with carbonation, were the main reactions occurring during biogas SESR. Dry (or CO2) methane reforming did not occur under the conditions studied due to the relatively low temperature and the presence of steam. High H2 purity (98.4 vol%) and H2 yield (91%) were experimentally obtained, pointing out the biogas SESR as a promising technology for the efficient production of high-purity high-yield hydrogen from a renewable source.

Hydrogen and power generation via integrated bio-oil sorption-enhanced steam reforming and solid oxide fuel cell systems: Economic feasibility analysis

A solid oxide fuel cell (SOFC) is a promising technology for generating electricity and heat with high efficiency and environmental friendliness. The use of a bio-oil as a renewable and low-cost feedstock for an external reforming SOFC system can reduce fossil fuel consumption and greenhouse gas emissions. From a technical perspective, high-purity hydrogen (H2) for SOFCs can be produced from the sorption-enhanced steam reforming (SESR). In this study, an economic analysis of a bio-oil SESR and SOFC integrated system (160 kW alternating current electricity production) is performed to evaluate the feasibility of the designed process. An economic comparison of the systems with different configurations, i.e., SESR-SOFC integrated systems with and without anode gas recirculation and a conventional reforming-based SOFC system (CON-SOFC), is presented in terms of their net present cost (NPC) and levelized cost of energy (LCOE). According to the results, the SESR-SOFC system with anode gas recirculation is more favorable than the CON-SOFC system and SESR-SOFC system without recirculation. Nevertheless, it remains economically infeasible because its NPC in the 20th year is approximately 6.13% higher than that of the combined heat and power (CHP) system (a base case). However, it can attain economic equivalence with the CHP system when a carbon tax of at least $15 tCO2−1 is considered or when the SOFC capital cost, interest rate, and bio-oil cost are separately reduced by 14%, 21%, and 37%, respectively. In addition, an increase in feed-in tariff has the highest impact on the NPC reduction of the renewable bio-oil SESR-SOFC integrated system with recirculation.

Feasibility analysis of Ca-looping sorption enhanced steam reforming of bio-butanol for SOFC application: comparative study with steam and auto-thermal reforming

ABSTRACT The thermodynamic analysis of Ca-looping sorption enhanced steam reforming of renewable energy source bio-butanol was carried out. The effect of reformer temperature, steam to carbon molar ratio and CaO to carbon molar ratio were investigated on the production rate of H2, CO, CO2 and CH4. The favorable reformer conditions were proposed as 600°C reformer temperature, steam to carbon molar ratio = 4 and CaO to carbon molar ratio = 1 with respect to hydrogen production rate and utility requirement of Ca-looping process. A process was developed for the application of reformer exhaust gases for solid oxide fuel cell. Performance of different reforming processes (sorption enhanced steam reforming, steam reforming and auto-thermal reforming) was evaluated in terms of overall energy efficiency. Among all these processes the auto-thermal reforming exhibited the highest overall energy efficiency of 77.30% followed by steam reforming (66.57%) and sorption enhanced steam reforming (66.04%).

Continuous high-purity hydrogen production by sorption enhanced steam reforming of ethanol over modified lithium silicate

Sorption-enhanced steam reforming of ethanol (SE-SRE) with in-situ CO2 removal is an environmentally friendly and sustainable approach for hydrogen production. Researches on continuous production of high-purity H2 by SE-SRE over the modified Li4SiO4 sorbent were conducted using two parallel reactor in this work. The low cost Li4SiO4 derived from rice husk ash (RHA) is a promising high-temperature CO2 sorbent. However, the poor adsorption kinetics of RHA-Li4SiO4 sorbent at low CO2 concentration is the major challenge. The metallic elements (K, Ca, Al, Mg) were employed to modify the RHA-Li4SiO4 for efficient CO2 capture. The developed sorbents were characterized and tested to study the role of dopants on the crystal, textural, microstructure and CO2 adsorption kinetics and cyclic stability. Results indicated that K doping effectively inhibited the growth of crystal aggregation and resulted in a fluffy morphology with abundant pores and higher specific surface area, while the addition of Ca, Al and Mg formed a nubby structure with larger particle size. K-doped RHA-Li4SiO4 exhibited the best CO2 uptake properties and the optimal K doping molar content was 0.02 with the maximum capture capacity of 34.16 wt%, which is higher than 27.1 wt% of pure RHA-Li4SiO4. Then, the effect of operating conditions on the enhancement behaviors was considered in the SE-SRE system. High-purity H2 (above 96%) was achieved by coupling K(0.02)/RHA-Li4SiO4 sorbent with Ni-based catalyst under the optimum condition (T: 525 °C, liquid hourly space velocity: 0.9 mL/(g·h), sorbent/catalyst: 4 and steam/carbon: 8.0). The adsorption activity of K(0.02)/RHA-Li4SiO4 maintained at a high level in ten SE-SRE/regeneration cycles. Finally, a scheme including two parallel fixed-bed reactors was designed and operated periodically for continuous production of high-purity H2. The reaction switching time was shown to depend strongly on the pre-breakthrough time and operating conditions. As the reaction switching time was 40 min, the products were always only H2 and CH4 (no CO and CO2 appear) and the H2 purity remained above 90% during 400 min, confirming high purity hydrogen stream can be obtained continuously.

Sorption enhanced steam reforming of methanol for high-purity hydrogen production over Cu-MgO/Al2O3 bifunctional catalysts

Sorption enhanced steam reforming of methanol (SESRM) can significantly promote the hydrogen production process with simultaneous CO2 sorption. The mechanical mixture of catalysts and sorbents as a conventional approach is complex and requires high temperatures for regeneration, which results in serious sintering of Cu-based catalysts. This paper describes a novel Cu-MgO/Al2O3 bifunctional catalysts (xCMA, x is denoted as the mass fraction of Cu, 0%–10%) via a sol–gel method for the SESRM process. We find that Cu species, including metallic Cu and Cu ions, co-exist on the catalyst. The metallic Cu on the catalyst surface is an active site for methanol steam reforming while the Cu ion in MgO lattice promotes the CO2 sorption capacity. Moreover, the incorporation of Cu ion into MgO also facilitates CO2 desorption by forming more bidentate carbonates. Due to the strong interaction between Cu and MgO, the Cu sintering is inhabited in comparison with the mechanical mixture of catalysts and sorbents. Meanwhile, MgO is found to induce more formate species to inhibit the generation of carbon monoxide. As a result, the optimal bifunctional catalyst, 8 wt% Cu-MgO/Al2O3 (8CMA) shows a superior performance in both catalytic reforming and CO2 sorption with a highest H2 selectivity of 99.3% and lowest CO selectivity (<0.15%) over 10 repeated cycles. This study suggests that the appropriate control of bifunctional catalysts can lead to powerful potential for high H2 production performance in SESRM.

Hydrogen Production from Sorption-Enhanced Steam Reforming of Phenol over a Ni–Ca–Al–O Bifunctional Catalyst

Phenol is one of the major products of bio-oil derived from biomass pyrolysis. Sorption-enhanced steam reforming of phenol (SESRP) aiming to produce high-purity H2 has been carried out over Ni–Ca–A...

Performance analysis and temperature gradient of solid oxide fuel cell stacks operated with bio-oil sorption-enhanced steam reforming

A high temperature gradient within a solid oxide fuel cell (SOFC) stack is considered a major challenge in SOFC operations. This study investigates the effects of the key parameters on SOFC system efficiency and temperature gradient within a SOFC stack. A 40-cell SOFC stack integrated with a bio-oil sorption-enhanced steam reformer is simulated using MATLAB and DETCHEM. When the air-to-fuel ratio and steam-to-fuel ratio increase, the stack average temperature and temperature gradient decrease. However, a decrease in the stack temperature steadily reduces the system efficiency owing to the tradeoff between the stack performance and thermal balance between heat recovered and consumed by the system. With an increase in the bio-oil flow rate, the system efficiency decreases because of the lower resident time for the electrochemical reaction. This is not, however, beneficial to the maximum temperature gradient. To minimize the temperature gradient of the SOFC stack, a decrease in the bio-oil flow rate is the most effective way. The maximum temperature gradient can be reduced to 14.6 K cm−1 with the stack and system efficiency of 76.58 and 65.18%, respectively, when the SOFC system is operated at an air-to-fuel ratio of 8, steam-to-fuel ratio of 6, and bio-oil flow rate of 0.0041 mol s−1.

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.

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

Abstract 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 °C with S/C ratio of 3.0. Under this condition, the maximum H2 concentrations of 69.75% and 67.68% were achieved for Ni/CaO–Ca12Al14O33(CH) and Ni/CaO–Ca12Al14O33(SL), respectively. The corresponding H2 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 H2 concentration of 82.23% and the maximum H2 yield of 2.31 L/g at 650 °C with S/C = 3.0 were observed for Ni–Co/CaO–Ca12Al14O33(CH). During the cyclic tests, the slight decrease in the H2 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 H2 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.

SORPTION-ENHANCED STEAM REFORMING OF ETHANOL FOR HYDROGEN PRODUCTION

In last years, sorption-enhanced steam reforming of ethanol (SESRE) has become an interesting alternative for the industry, since it offers high H2 purity with a simpler and smaller system. In this study CaO derived materials were synthesized to improve multicyclic CO2 sorption-desorption stability. A dispersant and inert phase (Ca12All4O33) was incorporated into CaO structure. The effects of CaO:Ca12Al14O33 ratio on the characteristics of the new absorbents and on their performance in sorption-enhanced steam reforming of ethanol were analyzed. The results obtained indicate that the absorbent 85% CaO – 15% Ca12Al14O33 had significantly improved cyclic reaction stability. Additionally, it was proved that with this adsorbent CO purity on wet basis was lower than 2 %, making it possible to attain in only one reaction stage the CO purity obtained after de WGS reactor.

Comprehensive Modeling of Sorption-Enhanced Steam Reforming of Coke Oven Gas in a Fluidized Bed Membrane Reactor

Integration of membrane hydrogen separation and carbon dioxide capture with fuel steam reforming efficiently promote hydrogen production and feedstock conversion. In this study, catalytic steam reforming of coven oven gas in a sorption-enhanced fluidized bed membrane reactor (MA-SE-SRCOG) was simulated using a reactive three-fluid model under Euler framework. The numerical studies provided insights into details about interactions of multi-scale sub-processes, including hydrogen permeation, carbon dioxide adsorption, catalytic reforming and multiphase flow dynamics, during MA-SE-SRCOG. Concentration polarization caused by hydrogen separation was also examined. Meanwhile, impacts of several operating parameters, such as reaction pressure, steam concentration, membrane position and reactor scale, on the performances of MA-SE-SRCOG were evaluated in terms of CH4 conversion, CO selectivity, hydrogen recovery factor and CO2 fix factor. The simulation results demonstrated that membrane hydr...

Effect of Ce/Ca Ratio in Ni/CeO2-ZrO2-CaO Catalysts on High-Purity Hydrogen Production by Sorption-Enhanced Steam Reforming of Acetic Acid and Bio-Oil

The sorption-enhanced steam reforming (SESR) of poplar sawdust pyrolysis oil and acetic acid for high-purity hydrogen production was investigated in this present work. The Ni/CeO2-ZrO2-CaO bifuncti...

Improved Hydrogen Production from Sorption-Enhanced Steam Reforming of Ethanol (SESRE) Using Multifunctional Materials of Cobalt Catalyst and Mg-, Ce-, and Zr-Modified CaO Sorbents

Hydrogen (H2) was produced via sorption-enhanced steam reforming of ethanol (SESRE) over multifunctional hybrid materials made of cobalt (10 wt %) and a Ca-based sorbent modified by CeO2, ZrO2, and...

Simulations of sorbent regeneration in a circulating fluidized bed system for sorption enhanced steam reforming with dolomite

In this work, the sorption enhanced steam reforming (SESR) method was developed for improved hydrogen (H2) production, and the drawbacks of conventional steam reforming processes on H2 yield and purity were overcome. However, the SESR process is discontinuous and requires regeneration after sorbent saturation with CO2. The circulating fluidized bed reactor (CFBR) system has previously been proposed for continuous H2 production, with both reforming and sorbent regeneration occurring simultaneously. The main aim of this work was to determine the feasibility and performance of SESR with a proper design and conditions in conjunction with the CFBR system. The reforming riser and bubbling bed regenerator are studied separately but related to each other. Two-dimensional transient models using the Euler‒Euler approach and kinetic theory of granular flow were used for fluid dynamic simulations combined with the decarbonation kinetics of dolomite, to investigate a conceptual regenerator system and determine its key conditions. A mixture of the Ni-based catalyst and dolomite from the risers was injected with a flux of 200kg/(m2s) and a catalyst to sorbent ratio of 2.54kg/kg. A double-stage bubbling bed regenerator system was designed with 1.2m width, 0.8m bed height, a gas inlet velocity of 0.2m/s and solid preheating at 950°C. The used dolomite was regenerated with an assumed CaO conversion of 3%; the almost fresh dolomite was then released with good mixing of the catalyst and sorbent.

Hydrochar-Supported Bimetallic Ni–Cu Nanocatalysts for Sustainable H2 Production

Noble-metal-free heterometallic Ni–Cu nanoparticles (NPs) supported on hydrochar have been developed for CO2 sorption-enhanced steam reforming of acetic acid (AC) to enhance H2 production. Among al...

Mg-promoted Ni-CaO microsphere as bi-functional catalyst for hydrogen production from sorption-enhanced steam reforming of glycerol

The sorption-enhanced steam reforming (SESR) process provides a simple way to produce high-purity hydrogen. And a key requirement for SESR is the availability of high cyclic stability of sorbent due to the rapid decline of sorption capacity caused by the sorbent sintering. Herein, we report a facile one-pot hydrothermal synthesis method by using in situ generated carbon microspheres as templates to prepare porous Ni-CaO-MgO bi-functional catalyst. The catalyst possessed MgO-stabilized, Ni and CaO microspheres featuring highly porous structure, which provided sufficient void space for volume variations and reduced the contact between CaO particles which was beneficial to improving the stability. Meanwhile, the uniformly distributed MgO had been found to reduce the particle size of CaO and stabilize the structure of bi-functional catalyst to ensure a stable CO2 uptake. 10Ni-CM7 as the best performing material only required 8.1 wt% MgO, showing 40% loss in sorption-enhanced effect after 10 cycles of repeated SESRG-desorption, where CaO utilization kept 59.1% exceeding the commercial CaO by ~109%.