Modeling of Packed Bed Methanol Steam Reformer Integrated with Tubular High Temperature Proton Exchange Membrane Fuel Cell

This work proposes a novel tubular structure of high-temperature proton exchange membrane fuel cell(PEMFC)integrated with a built-in packed-bed methanol steam reformer to provide hydrogen for power output.A two-dimensional axisymmetric non-isothermal model was developed in COMSOL Multiphysics 5.4 to simulate the performance of a tubular high temperature proton membrane fuel cell and a packed bed methanol reformer.The model considers the coupling multi-physical processes,including methanol reforming reaction,water gas shift reaction,methanol cracking reaction as well as the heat,mass and momentum transport processes.The sub-model of the tubular packed-bed methanol reformer is validated between 433 K and 493 K with the experimental data reported in the literature.The sub-model of the high temperature proton exchange fuel cell is validated between 393 K and 433 K with the published literature.Our results show that power output and temperature distribution of the integrated unit depend on methanol flow rates and working voltages.It was suggested that stable power generation performance of 0.14 W/cm_(2)and temperature drop in methanol steam reformer of≤10 K could be achieved by controlling the methanol space-time ratio of≥250 kg·s/mol with working voltage at 0.6 V,even in the absence of an external heat source.

Ethanol steam reforming over Ni/ZSM-5 nanosheet for hydrogen production

Compared to reforming reactions using hydrocarbons,ethanol steam reforming(ESR)is a sustainable alternative for hydrogen(H_(2))production since ethanol can be produced sustainably using biomass.This work explores the catalyst design strategies for preparing the Ni supported on ZSM-5 zeolite catalysts to promote ESR.Specifically,two-dimensional ZSM-5 nanosheet and conventional ZSM-5 crystal were used as the catalyst carriers and two synthesis strategies,i.e.,in situ encapsulation and wet impregnation method,were employed to prepare the catalysts.Based on the comparative characterization of the catalysts and comparative catalytic assessments,it was found that the combination of the in situ encapsulation synthesis and the ZSM-5 nanosheet carrier was the effective strategy to develop catalysts for promoting H_(2) production via ESR due to the improved mass transfer(through the 2-D structure of ZSM-5 nanosheet)and formation of confined small Ni nanoparticles(resulted via the in situ encapsulation synthesis).In addition,the resulting ZSM-5 nanosheet supported Ni catalyst also showed high Ni dispersion and high accessibility to Ni sites by the reactants,being able to improve the activity and stability of catalysts and suppress metal sintering and coking during ESR at high reaction temperatures.Thus,the Ni supported on ZSM-5 nanosheet catalyst prepared by encapsulation showed the stable performance with~88% ethanol conversion and~65% H_(2) yield achieved during a 48-h longevity test at 550-C.

High H_(2) selective performance of Ni-Fe-Ca/H-Al catalysts for steam reforming of biomass and plastic

The development of a selective catalyst for the conversion of biomass and plastics into H2by steam reforming can combat the energy crisis and global warming.In this work,support Ni-Fe-Ca/H-Al bifunctional catalysts were prepared by loading Ni and Fe into pretreatment CaO/Al_(2)O_(3)(Ca/H-Al)carriers and showed high catalytic activity for the steam reforming of biomass and plastic.Moreover,the idea of bidirectional degradation was exploited to strengthen the pyrolysis of plastic with a high H/C and biomass with a high O/C.Interestingly,the products presented high H2selective(1302.10 m L/g)and low CO_(2)yield(120.23 m L/g)in 7Ni-5Fe-Ca/H-Al(2:4)catalyst compared with current reports.Here,the abundant oxygen vacancies(Ov)in the H-Al carrier exhibited an electron-deficient nature,providing active sites for anchoring Ni O.Meanwhile,Ni O interacted with Ca_(2)Fe_(2)O_(5)to produce more defective Ovsites,which stabilized the NiO particles in the 7Ni-5Fe-Ca/H-Al(2:4)catalyst,and the interaction between the catalyst and the carrier was enhanced,leading to the reduction of weakly basic sites,this property promoted the strong adsorption of CO_(2)and H2O by the catalyst,contributing to the enhancement of efficient steam conversion and the promotion of conversion of by-products to H2.Notably,7Ni-5Fe-Ca/H-Al(2:4)catalysts maintained structural integrity after regeneration and exhibited excellent regenerability in H2selection and CO_(2)adsorption.The work provides a new idea for the study of efficient H2production from steam reforming of biomass and plastics.

Simultaneous syngas production with different H_2/CO ratio in a multi-tubular methane steam and dry reformer by utilizing of CLC

For syngas production, the combustion of fossil fuels produces large amounts of CO2 as a greenhouse gas annually which intensifies global warming. In this study, chemical looping combustion （CLC） has been utilized for the elimination of CO2 emission to atmosphere during simultaneous syngas production with different H2/CO ratio in steam reforming of methane （SR） and dry reforming of methane （DR） in a CLC-SR-DR configuration. In CLC-SR-DR with 184 reformer tubes （similar to an industrial scale steam reformer in Zagros Petrochemical Company, Assaluyeh, Iran）, DR reaction occurs over Rh-based catalysts in 31 tubes. Also, SR reaction is happened over Ni-based catalysts in 153 tubes. CLC via employment of Mn-based oxygen carriers supplies heat for DR and SR reactions and produces CO2 and H2O as raw materials simultaneously. A steady state heterogeneous catalytic reaction model is applied to analyze the performance and applicability of the proposed CLC-SR-DR configuration. Simulation results show that combustion efficiency reached 1 at the outlet of fuel reactor （FR）. Therefore, pure CO2 and H2O can be recycled to DR and SR sides, respectively. Also, CH4 conversion reached 0.2803 and 0.7275 at the outlet of SR and DR sides, respectively. Simulation results indicate that, 3223 kmol.h-l syngas with a H2/CO ratio equal to 9.826 was produced in SR side of CLC-SR-DR. After that, 1844 kmol.h-1 syngas with a H2/CO ratio equal to 0.986 was achieved in DR side of CLC-SR-DR. Results illustrate that by increasing the number of DR tubes to 50 tubes and considering 184 fixed total tubes in CLC-SR-DR, CH4 conversions in SR and DR sides decreased 2.69% and 3.31%, respectively. However, this subject caused total syngas production in SR and DR sides （in all of 184 tubes） enhance to 5427 kmol-h-1. Finally, thermal and molar behaviors of the proposed configuration demonstrate that CLC-SR-DR is applicable for simultaneous syngas production with high and low Hx/CO ratios in an environmental friendly process.

Improvement strategies for Ni-based alcohol steam reforming catalysts

Steam reforming(SR)of fossil methane is already a well-known,documented and established expertise in the industrial sector as it accounts for the vast majority of global hydrogen production.From a sustainable development perspective,hydrogen production by SR of biomass-derived feedstock represents a promising alternative that could help to lower the carbon footprint of the traditional process.In this regard,bio-alcohols such as methanol,ethanol or glycerol are among the attractive candidates that could serve as green hydrogen carriers as they decompose at relatively low temperatures in the presence of water compared to methane,allowing for improved H_(2)yields.However,significant challenges remain regarding the activity and stability of nickel-based catalysts,which are most widely used in alcohol SR processes due to their affordability and ability to break C–C,O–H and C–H bonds,yet are prone to rapid deactivation primarily caused by coke deposition and metal particle sintering.In this state-of-the-art review,a portfolio of strategies to improve the performance of Ni-based catalysts used in alcohol SR processes is unfolded with the intent of pinpointing the critical issues in catalyst development.Close examination of the literature reveals that the efforts tackling these recurring issues can be directed at the active metal,either by tuning Ni dispersion and Ni-support interactions or by targeting synergistic effects in bimetallic systems,while others focus on the support,either by modifying acid-base character,oxygen mobility,or by embedding Ni in specific crystallographic structures.This review provides a very useful tool to orient future work in catalyst development.

Hydrogen production from steam reforming of methanol over CuO/ZnO/Al_2O_3 catalysts: Catalytic performance and kinetic modeling

A series of CuO/ZnO/Al_2O_3, CuO/ZnO/ZrO_2/Al_2O_3 and CuO/ZnO/CeO_2/Al_2O_3 catalysts were prepared by coprecipitation and characterized by N_2 adsorption, XRD, TPR, N_2O titration and HRTEM. The catalytic performances of these catalysts for the steam reforming of methanol were evaluated in a laboratory-scale fixed-bed reactor at 0.1 MPa and temperatures between 473 and 543 K. The results showed that the catalytic activity depended greatly on the catalyst reducibility and the specific surface area of Cu. An approximate linear correlation between the catalytic activity and the Cu surface area was found for all catalysts investigated in this study.Compared to CuO/ZnO/Al_2O_3, the ZrO_2-doped CuO/ZnO/Al_2O_3 exhibited higher activity and selectivity to CO,while the CeO_2-doped catalyst displayed lower activity and selectivity. Finally, an intrinsic kinetic study was carried out over a screened CuO/ZnO/CeO_2/Al_2O_3 catalyst in the absence of internal and external mass transfer effects. A good agreement was observed between the model-derived effluent concentrations of CO(CO_2) and the experimental data. The activation energies for the reactions of methanol-steam reforming, water-gas shift and methanol decomposition over CuO/ZnO/CeO_2/Al_2O_3 were 93.1, 85.1 and 116.5 k J·mol^(-1), respectively.

Effect of Ni Loading and Ce_(x)Zr_(1-x)O_(2) Promoter on Ni-Based SBA-15 Catalysts for Steam Reforming of Methane

A series of Ni/SBA-15 catalysts with Ni contents ranging from 5wt% to 20wt% as well as 10wt%Ni/10wt%CexZr1-xO2/SBA-15 （x=0, 0.5, 1） were prepared. The structures of the catalysts were characterized using XRD, TPR, TEM and BET techniques. The catalytic activities of the catalysts for steam reforming of methane were evaluated in a continuous flow microreactor. The results indicated that both the Ni/SBA-15 and the Ni/CexZr1-xO2/SBA-15 catalysts had good catalytic activities at at- mospheric pressure. The 10wt%Ni/SBA-15 catalyst exhibited excellent stability at 800 ℃ for time on stream of 740 h. After the reaction, carbon deposits were not formed on the surface of the catalyst. There existed a regular hexagonal mesoporous structure in the Ni/SBA-15 and the Ni/CexZr1-xO2/SBA-15 catalysts. The nickel species and the CexZr1-xO2 component were all confined in the SBA-15 mesopores. The CexZr1-xO2 could promote dispersion of the nickel species in the Ni/CexZr1-xO2/SBA-15 catalysts.

High-efficient solar-driven hydrogen production by full-spectrum synergistic photo-thermo-catalytic methanol steam reforming with in-situ photoreduced Pt-CuO_(x) catalyst

Synergy between the intrinsic photon and thermal effects from full-spectrum sunlight for H_(2) production is considered to be central to further improve solar-driven H_(2) production.To that end,the photo-thermocatalyst that demonstrates both photoelectronic and photothermal conversion capabilities have drawn much attention recently.Here,we propose a novel synergistic full-spectrum photo-thermo-catalysis technique for high-efficient H_(2) production by solar-driven methanol steam reforming(MSR),along with the Pt-Cu Oxphoto-thermo-catalyst featuring Pt-Cu/Cu_(2)O/CuO heterojunctions by Pt-mediated in-situ photoreduction of Cu O.The results show that the H_(2) production performance rises superlinearly with increasing light intensity.The optimal H_(2) production rate of 1.6 mol g^(-1) h^(-1) with the corresponding solar-to-hydrogen conversion efficiency of 7%and the CO selectivity of 5%is achieved under 15×sun full-spectrum irradiance(1×sun=1 k W m^(-2))at 180°C,which is much more efficient than the previously-reported Cu-based thermo-catalysts for MSR normally operating at 250~350°C.These attractive performances result from the optimized reaction kinetics in terms of intensified intermediate adsorption and accelerated carrier transfer by long-wave photothermal effect,and reduced activation barrier by short-wave photoelectronic effect,due to the broadened full-spectrum absorbability of catalyst.This work has brought us into the innovative technology of full-spectrum synergistic photothermo-catalysis,which is envisioned to expand the application fields of high-efficient solar fuel production.

Improved catalytic performance of Ni catalysts for steam methane reforming in a micro-channel reactor

Milliseconds process to produce hydrogen by steam methane reforming （SMR） reaction, based on Ni catalyst rather than noble catalyst such as Pd, Rh or Ru, in micro-channel reactors has been paid more and more attentions in recent years. This work aimed to further improve the catalytic performance of nickel-based catalyst by the introduction of additives, i.e., MgO and FeO, prepared by impregnation method on the micro-channels made of metal-ceramic complex substrate. The prepared catalysts were tested in the same micro-channel reactor by switching the catalyst plates. The results showed that among the tested catalysts Ni-Mg catalyst had the highest activity, especially under harsh conditions, i.e., at high space velocity and/or low reaction temperature. Moreover, the catalyst activity and selectivity were stable during the 12 h on stream test even when the ratio of steam to carbon （SIC） was as low as 1.0. The addition of MgO promoted the active Ni species to have a good dispersion on the substrate, leading to a better catalytic performance for SMR reaction.

Hydrogen and syngas production from two-step steam reforming of methane using CeO_2 as oxygen carrier

CeO2 oxygen carrier was prepared by precipitation method and tested by two-step steam reforming of methane （SRM）. Two-step SRM for hydrogen and syngas generation is investigated in a fixed-bed reactor. Methane is directly converted to syngas at a H2/CO ratio close to 2 ： 1 at a high temperature （above 750 °C） by the lattice oxygen of CeO2; methane cracking is found when the reduction degree of CeO2 was above 5.0% at 850 °C in methane isothermal reaction. CeO2？δ obtained from methane isothermal reaction can split water to generate CO-free hydrogen and renew its lattice oxygen at 700 °C; simultaneously, deposited carbon is selectively oxidized to CO2 by steam following the reaction （C＋2H2O→CO2＋2H2）. Slight deactivation in terms of amounts of desired products （syngas and hydrogen） is observed in ten repetitive two-step SRM process due to the carbon deposition on CeO2 surface as well as sintering of CeO2.

Hydrogen production through diesel steam reforming over rare-earth promoted Ni/γ-Al_2O_3 catalysts

Rare-earth （La, Ce, Yb） promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catalyst characterizations with TG, TPR and H2 chemisorption were carried out to investigate the promoting mechanism. Experimental results show that rare-earth promoters, especially Yb promoter, obviously improve the activity and carbon formation resistance of Ni/γ-Al2O3 catalyst, and Yb-Ni catalyst shows even higher performance than several commercial catalysts. According to the characterization results, Yb promoter enhances the interaction between the active metal and support, thus increasing the active metal＇s dispersion and improving its performance. Furthermore, the obvious difference in diesel conversion between Yb-Ni catalyst and others was shown in the temperature range of 450-550 °C, which would be the reason for its excellent carbon resistance.

Glycerol steam reforming over calcium hydroxyapatite supported cobalt and cobalt-cerium catalysts

Calcium hydroxyapatite（HAp） supported cobalt and cobalt-cerium catalysts were examined for hydrogen production in glycerol steam reforming. The catalysts were synthesized by incipient wetness impregnation method and characterized through X-ray diffraction, adsorption-desorption isotherms of N2 and temperature-programmed reduction of H2. Catalytic properties were examined in terms of glycerol conversion, selectivity toward hydrogen and C-containing products in temperature range of 650-800 ℃.The effect of active metal reduction and residence time（thereby flow feed rate） was analysed. It was found that the growth of residence time increased the hydrogen selectivity in the whole temperatures range whereas the catalyst reduction, before the catalytic process, decreased the hydrogen selectivity at temperatures lower than 750 ℃. The cerium addition improved the catalytic behaviour for hydrogen production via glycerol steam reforming. Cerium oxide suppressed the sintering of cobalt particles and as a result Co-Ce/HAp ensured higher stability and H2 selectivity than Co/HAp. Under reaction conditions investigated in this study, the highest selectivity toward hydrogen at 650 ℃ was obtained for 7.5 Co-Ce/HAp catalyst.

Effects of inherent potassium on the catalytic performance of Ni/biochar for steam reforming of toluene as a tar model compound

Biochar supported nickel(Ni/BC)has been widely studied as a cheap and easy-to-prepare catalyst with potential applications in tar reforming during the gasification of low-rank fuels,such as brown coal and biomass.However,the role and behaviors of inherent K species,especially their interactions with Ni particles and the biochar support,are not well understood yet.In this work,three Ni/BC catalysts with varying K amount were prepared from raw,water-washed,and acid-washed biomass.They were used in steam reforming of toluene as a tar model compound to elucidate the effects of inherent K on the catalytic activity and stability.Detailed characterization indicated that K enhanced water adsorption due to its hydroscopicity and lowered the condensation and graphitization degrees of biochar,but the alteration to the electronic state of Ni was not observed.These effects together led to a temperature-dependent role of K.That is,at relatively low temperatures of 450 and 500℃,toluene conversion was increased in the presence of K,due to the increased concentration of adsorbed water around Ni particles.By contrast,at relatively higher temperatures of 550 and 600℃,although initial high activity was achieved,Ni/BC with K deactivated rapidly because of the accelerated consumption of the biochar support.

Ethanol steam reforming over Ni-Cu/Al_2O_3-M_yO_z (M = Si, La, Mg,and Zn) catalysts

Ni-based catalysts doped with copper additives were studied on their role in ethanol steam reforming reaction. The effects of Cu content, support species involving Al2O3-SIO2, Al2O3-MgO, Al2O3-ZnO, and Al2O3-La2O3, on the catalytic performance were studied. Characterizations by TPR, XRD, NH3-TPD, XPS, and TGA indicated that catalysts 30Ni5Cu/Al2O3-MgO and 30Ni5Cu/Al2O3-ZnO have much higher H2 selectivity than 30Ni5Cu/Al2O3-SiO2, as well as good coke resistance. H2 selectivity for 30Ni5Cu/Al2O3-MgO catalyst was 73.3% at 450 ℃ and increased to 94.0% at 600℃, whereas for 30Ni5Cu/Al2O3-ZnO catalyst, the H2 selectivity was 63.6% at 450 ℃ and 95.2% at 600℃. TheseAl2O3-MgO and Al2O3-ZnO supported Ni-Cu bimetallic catalysts may have important applications in the production of hydrogen by ethanol steam reforming reactions.

Renewable hydrogen production from steam reforming of glycerol(SRG)over ceria-modified Y-alumina supported Ni catalyst

Excess crude glycerol derived as a by-product from biodiesel industry prompts the need to valorise glycerol to value-added chemicals.In this context,catalytic steam reforming of glycerol(SRG) was proposed as a promising and sustainable alternative for producing renewable hydrogen(H2).Herein,the development of nickel(Ni) supported on ceria-modified mesoporous γ-alumina(γ-Al2 O3) catalysts and their applications in catalytic SRG(at550-750℃ atmospheric pressure and weight hourly space velocity,WHSV,of 44,122 ml·g^-1·h^-1(STP)) is presented.Properties of the developed catalysts were characterised using many technique s.The findings show that ceria modification improved Ni dispersion on γ-Al2 O3 catalyst support with highly active small Ni particles,which led to a remarkable catalytic performance with the total glycerol conversion(ca.99%),glycerol conversion into gaseous products(ca.77%) and H2 yield(ca.62%).The formation rate for H2 production(14.4 ×10^(-5)mol·s^-1·g^-1, TOF(H2)=3412 s^-1) was significantly improved with the Ni@12 Ce-Al2 O3 catalyst,representing nearly a 2-fold increase compared with that of the conventional Ni@AI2 O3 catalyst.In addition,the developed catalyst also exhibited comparatively high stability(for 12 h) and coke resistance ability.

Hydrogen production from steam reforming of ethanol over Ni/MgO-CeO_2 catalyst at low temperature

MgO,CeO2 and MgO-CeO2 with different mole ratio of Mg:Ce were prepared by solid-phase burning method.Catalysts Ni/MgO,Ni/CeO2 and Ni/MgO-CeO2 were prepared by impregnation method.The catalytic properties were evaluated in ethanol steam reforming(ESR) reaction.Specific surface areas of the supports were measured by nitrogen adsorption-desorption at 77 K,and the catalysts were characterized with X-ray diffraction(XRD),temperature programmed reduction(TPR) and thermogravimetric(TG).The results showed that well...

Hydrogen production through glycerol steam reforming using Co catalysts supported on SBA-15 doped with Zr,Ce and La

The steam reforming of glycerol has been studied at 500 and 600 oC using Co/SBA-15 and Co/M/SBA-15（M: Zr, Ce, or La） promoted catalysts. The prepared materials were characterized by inductively coupled plasma atomic emission spectroscopy（ICP-AES）, X-ray powder diffraction（XRD）, hydrogen temperatureprogramed reduction（H;-TPR）, ammonia temperature-programed desorption（NH;-TPD）, nitrogen physisorption analysis（N;-BET）, transmission electron microscopy（TEM） and thermogravimetric analysis（TGA）. The incorporation of promoters like Zr, Ce and La on SBA-15 support and successive Co impregnation leaded to smaller cobalt crystallites improving metaldispersion. Besides, stronger metal-support interactions between Co species and M/SBA-15 supports were observed. Thanks to the incorporation of Zr, La and mainly Ce, promoted catalysts present higher glycerol conversion than Co/SBA-15 along 5 h of time on stream. Besides, at 600 oC, Co/M/SBA-15（M: Zr, Ce, or La） catalysts produce higher hydrogen amounts than Co/SBA-15.

Catalytic steam reforming of biomass over Ni-based catalysts: Conversion from poplar leaves to hydrogen-rich syngas

A series of Ni/SBA-15 catalysts with Ni contents from 5 wt%–20 wt%and CaO-12.5%Ni/SBA-15 catalysts with CaO contents from 1.4 wt%– 9.8 wt%have been prepared.The structure of the catalysts was characterized using X-ray diffraction（XRD）,N2 adsorption-desorption,transmission electron microscopy（TEM）and X-ray photoelectron spectroscopy（XPS）.The performance of catalytic steam reforming of the poplar leaves to the hydrogen-rich syngas was tested in a fixed-bed reactor.The results indicate that the 7.0wt%CaO-12.5wt%Ni/SBA-15 catalyst exhibits the best performance for the catalytic steam reforming of poplar leaves to hydrogen-rich syngas.The ratio of H2：CO can reach ca 5：1 in the hydrogen-rich syngas.The yield of H2 can reach 273.30 mL/g（poplar leaves）.In the CaO-Ni/SBA-15 catalyst,Ni active component mainly fills the role of catalytic steam reforming of the poplar leaves,and CaO active component mainly plays the role as water-gas shift and CO2 sorbent.

Highly dispersible cerium-oxide modified Ni/SBA-15 for steam reforming of bio-mass based JP10

Ni/SBA-15 modified by highly dispersed cerium-oxide was prepared with the aid of sucrose for steam reforming of JP10(C_(10)H(16)).Their characterization showed that addition of appropriate amount ceria led to the formation of highly dispersed CeO_(2)and Ni,and the CeO_(2)covered smaller nickel particles like strawberry seeds to form much more interface between them.Their catalytic activity exhibited higher stability over time on stream of 6.5 h with conversion higher than 95%and higher carbon resistance(mass loss less than 4.5%by TG),which may derive from good properties below:(1)much more interface enhanced cooperation effect and increased turnover frequency at the interface;(2)the stronger interaction between Ni and ceria to suppress sintering by formation of Ni-O-Ce solid solution;(3)the large amount of oxygen vacancies from the formation of Ni-O-Ce solid solution and highly dispersed CeO_(2)to facilitate the water-gas-shift reaction and carbon removal.

Low CO content hydrogen production from oxidative steam reforming of ethanol over CuO-CeO_2 catalysts at low-temperature

CuO-CeO2 catalysts were prepared by a urea precipitation method for the oxidative steam reforming of ethanol at low-temperature.The catalytic performance was evaluated and the catalysts were characterized by inductively coupled plasma atomic emission spectroscopy,X-ray diffraction,temperature-programmed reduction,field emission scanning electron microscopy and thermo-gravimetric analysis.Over CuOCeO2 catalysts,H2 with low CO content was produced in the whole tested temperature range of 250–450 C.The non-noble metal catalyst 20CuCe showed higher H2production rate than 1%Rh/CeO2 catalyst at 300–400 C and the advantage was more obvious after 20 h testing at400 C.These results further confirmed that CuO-CeO2 catalysts may be suitable candidates for low temperature hydrogen production from ethanol.