Profitability Analysis of Selected Steam Methane Reforming Methods for Hydrogen Production

One of the matured methods for producing hydrogen in bulk is steam methane reforming (SMR). The two commercial aspects of producing hydrogen from SMR are SMR with shift reactor (SR) and SMR with dry methane reforming (DRM). Although SMR with SR produces high hydrogen yield, it emits a large quantity of carbon dioxide (CO2). On the contrary, SMR and DRM produce low hydrogen yield but favorably emit a low quantity of CO2. However, it is not obvious which of these methods is more favourable economically. Consequently, using UNISIM Software Package, this study investigates three SMR methods namely SMR with SR, SMR with DRM and SMR with the combination of DRM and SR for the purpose of determining the most favourable route for producing hydrogen. This was done on the basis of feedstock rate of 100 kmol/hr of methane which reacted with 250 kmol/hr of steam for 8000 hrs annually using the rate of CO2 and CO emissions (COx) and the plant net profit percentage as performance indices. The profitability analysis shows that SMR/SR process is the most profitable process with a net profit percentage of 41.3%. Moreover, SMR/SR process has the highest yield and interestingly lowest COx emission rate. It is therefore concluded that the most favourable process route, technically and economically, is SMR/SR for the production of hydrogen using methane as feedstock.

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.

NiO-CaO materials as promising catalysts for hydrogen production through carbon dioxide capture and subsequent dry methane reforming

In this work, CaO-NiO mixed oxide powders were evaluated as consecutive CO;chemisorbents and catalytic materials for hydrogen production thought the CH;reforming process. Between the NiO impregnated CaO and CaO-NiO mechanical composite, the first one presented better chemical behaviors during the CO;capture and CH;reforming processes, obtaining syngas（H;+ CO） as final product. Results showed that syngas was produced at two different temperature ranges, between 400 and 600 °C and at T > 800 °C, where the first temperature range corresponds to the CH;reforming process but the second temperature range was attributed to a different catalytic reaction process: CH;partial oxidation. These results were confirmed through different isothermal and cyclic experiments as well as by XRD analysis of the final catalytic products, where the nickel reduction was evidenced. Moreover, when a CO-O;flow was used during the carbonation process a triple process was achieved:（i） CO oxidation,（ii） CO;chemisorption and（iii） CH;reforming. Using this gas flow the hydrogen production was always higher than that obtained with CO;.

Methane reforming with CO_2 to syngas over CeO_2-promoted Ni/Al_2O_3-ZrO_2 catalysts prepared via a direct sol-gel process

CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy （IR）, thermal gravimetric analysis （TGA）, microscopic analysis, X-ray diffraction （XRD） and temperature-programmed reduction （TPR）. The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.

Preparation and catalytic properties of ZrO_2-Al_2O_3 composite oxide supported nickel catalysts for methane reforming with carbon dioxide

ZrO 2-Al 2O 3 composite oxides and supported Ni catalysts were prepared, and characterized by N 2 adsorption /desorption, X-ray diffraction(XRD) an d X-ray photoelectron spectroscopy(XPS) techniques. The catalytic performance and carbon deposition was also investigated. This mesoporous composite oxide is shown to be a promising catalyst support. An increase in the catalytic activity and stability of methane and carbon dioxide reforming reaction was resulted from the zirconia addition, especially at 5wt% ZrO 2 content. The Ni catalyst supported ZrO 2-Al 2O 3 has a strong resistance to sintering and the carbon deposition in a relatively long-term reaction.

Effect of Partial Substitution of Ni by Cu in LaNiO_3 Perovskite Catalyst for Dry Methane Reforming

A series of ternary perovskite type oxides LaNi1-xCuxO3(x = 0.2,0.4,0.6,0.8,and 1.0) were synthesized via the sol-gel method in propionic acid.Partial substitution of Ni by Cu showed higher activities and selectivities towards syngas products.LaNi0.8Cu0.2O3 was the most active toward the CH4 and CO2 conversions,and was selective for syngas products.Temperature-programmed reduction results showed that the addition of Cu facilitates the reduction of Ni3+ to Ni0,which is the main reason for the higher performance of this catalyst.

Machine learning-driven optimization of plasma-catalytic dry reforming of methane

This study investigates the dry reformation of methane(DRM)over Ni/Al_(2)O_(3)catalysts in a dielectric barrier discharge(DBD)non-thermal plasma reactor.A novel hybrid machine learning(ML)model is developed to optimize the plasma-catalytic DRM reaction with limited experimental data.To address the non-linear and complex nature of the plasma-catalytic DRM process,the hybrid ML model integrates three well-established algorithms:regression trees,support vector regression,and artificial neural networks.A genetic algorithm(GA)is then used to optimize the hyperparameters of each algorithm within the hybrid ML model.The ML model achieved excellent agreement with the experimental data,demonstrating its efficacy in accurately predicting and optimizing the DRM process.The model was subsequently used to investigate the impact of various operating parameters on the plasma-catalytic DRM performance.We found that the optimal discharge power(20 W),CO_(2)/CH_(4)molar ratio(1.5),and Ni loading(7.8 wt%)resulted in the maximum energy yield at a total flow rate of∼51 mL/min.Furthermore,we investigated the relative significance of each operating parameter on the performance of the plasma-catalytic DRM process.The results show that the total flow rate had the greatest influence on the conversion,with a significance exceeding 35%for each output,while the Ni loading had the least impact on the overall reaction performance.This hybrid model demonstrates a remarkable ability to extract valuable insights from limited datasets,enabling the development and optimization of more efficient and selective plasma-catalytic chemical processes.

Dry-gel synthesis of hierarchical Ni-La@S-1 catalysts with stabilized Ni-La bimetals nanoparticles for dry reforming of methane

Dry reforming of methane (DRM) can simultaneously convert two critical greenhouse gases CH4 and CO_(2) into high-value syngas. However, the catalyst deactivation caused by sintering and carbon deposition of Ni-based catalysts at high temperature is a significant problem to be solved for DRM industrialization. Herein, we represent a hierarchical Ni-La@S-1 catalyst for DRM reaction, showing high anti-sintering/coke capacity to improve DRM stability. The La and Ni nitrates were first grinded into the pores of SBA-15 followed by N2-treatment;the sample was then recrystallized by a unique template assisted-uniformly dispersed strategy to obtain the hierarchical Ni-La@S-1 catalyst. This strategy achieves uniform encapsulation of stabilized Ni-La bimetallic nanoparticles in S-1 with high loading, exhibiting high DRM activity and stability at 700 °C and 36,000 mL·g^(−1)·h^(−1). Moreover, La addition promoted CO_(2) to form bidentate carbonate, a critical intermediate in DRM, which greatly ameliorated carbon deposition in Ni catalysts. This work offers promising clue for tailoring the industrial DRM catalysts.

Regulating crystal phase of TiO_(2) to enhance catalytic activity of Ni/TiO_(2) for solar-driven dry reforming of methane

Ni/TiO_(2) catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO_(2) remains unclear.In this work,the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO_(2).Structural characterizations revealed that a distinct TiO_(x) coating on the Ni nanoparticles(NPs)was evident for Ni/TiO_(2)-700 catalyst due to strong metal-support interaction.It is observed that the TiOx overlayer gradually disappeared as the ratio of rutile/anatase increased,thereby enhancing the exposure of Ni active sites.The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH4,which led to the much elevated catalytic activity for Ni/TiO_(2)-950 in which rutile dominated.Therefore,the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio.Ni/TiO_(2)-950,characterized by a predominant rutile phase,exhibited the highest DRM reactivity,with remarkable H_(2) and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h),respectively.These rates were approximately 257 and 130 times higher,respectively,compared to those obtained on Ni/TiO_(2)-700 with anatase.This study suggests that the optimization of crystal structure of TiO_(2) support can effectively enhance the performance of photothermal DRM reaction.

BaCe_(0.8)Fe_(0.1)Ni_(0.1)O_(3−δ)-impregnated Ni-GDC by phase-inversion as an anode of solid oxide fuel cells with on-cell dry methane reforming

BaCe_(0.8)Fe_(0.1)Ni_(0.1)O_(3−δ)(BCFN)in a perovskite structure is impregnated consecutively by BCFN solution and BCFN suspension into a phase-inversion prepared NiO–Gd_(0.1)Ce_(0.9)O_(2−δ)(GDC)scaffold as an anode for solid oxide fuel cells(SOFCs)with on-cell dry reforming of methane(DRM).The whole pore surface of the scaffold is covered by small BCFN particles formed by BCFN solution impregnation;the large pores near the scaffold surface are filled by BCFN aerogels with a high specific surface area produced by BCFN suspension impregnation,which act as a catalytic layer for on-cell DRM.After reduction,the anode consists of a Ni–GDC scaffold and BCFN particles with exsolved FeNi3 nanoparticles.This BCFN-impregnated Ni–GDC anode has higher electrical conductivity,electrochemical activity,and resistance to carbon deposition,with which the cell shows maximum power densities between 1.44 and 0.92 W·cm^(−2) when using H_(2) and between 1.09 and 0.50 W·cm^(−2) when using CO_(2)–CH_(4) at temperatures ranging from 750 to 600℃.A stable performance at 400 mA·cm^(−2) and 700℃is achieved using 45%CO_(2)–45%CH_(4)–10%N_(2) for more than 400 h without carbon deposition,benefiting from the impregnated BCFN aerogel with a high specific surface area and water adsorbability.

Efficiency analysis of sorption-enhanced method in steam methane reforming process

The sorption-enhanced method can change the thermodynamic equilibrium by absorbing CO_(2).However,it also brings about the problems of high regeneration temperature of adsorbent and large regeneration energy consumption.In order to study the impact of enhanced adsorption methods on the overall energy cost of the system in the hydrogen production process,this paper analyzes and compares steam methane reforming and reactive adsorption-enhanced steam methane reforming with the energy consumption of hydrogen production products as the evaluation index.The results showed that the energy consumption per unit hydrogen production decreased from 276.21 MJ/kmol to 131.51 MJ/kmol,and the decomposition rate of H2O increased by more than 20%after the addition of adsorption enhancement method.It is proved that the advantage of sorption enhanced method on pre-separation of CO_(2)in the product makes up for the disadvantage of energy consumption of adsorbent regeneration.In addition,the ability of the process to obtain H element is improved by the high decomposition rate of H2O,which realizes a more rational distribution of the element.

Design of a multi-inlet solar thermochemical reactor for steam methane reforming with improved performance

Reactor structure design plays an important role in the performance of solar-thermal methane reforming reactors.Based on a conventional preheating reactor,this study proposed a cylindrical solar methane reforming reactor with multiple inlets to vary the temperature field distribution,which improved the temperature of the reaction region in the reactor,thereby improving the reactor performance.A multi-physical model that considers mass,momentum,species,energy conservation,as well as thermochemical reaction kinetics of methane reforming,was applied to numerically investigate the reactor performance and analyze the factors that affect performance improvement.It was found that compared with a conventional preheating reactor,the proposed cylindrical reac-tor with inner and external inlets for gas feeding enhanced heat recovery from the exhausted gas and provided a more suitable temperature field for the reaction in the reactor.Under different operating conditions,the methane conversion in the cylindrical reactor with multi-inlet increased by 9.5%to 19.1%,and the hydrogen production was enhanced by 12.1%to 40.3%in comparison with the conventional design,even though the total reaction catalyst volume was reduced.

Probing deactivation by coking in catalyst pellets for dry reforming of methane using a pore network model

Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, which prevents this technology from commercialization. In this work, a pore network model is developed to probe the catalyst deactivation by coking in a Ni/Al_(2)O_(3) catalyst pellet for DRM. The reaction conditions can significantly change the coking rate and then affect the catalyst deactivation. The catalyst lifetime is higher under lower temperature, pressure, and CH_(4)/CO_(2) molar ratio, but the maximum coke content in a catalyst pellet is independent of these reaction conditions. The catalyst pellet with larger pore diameter, narrower pore size distribution and higher pore connectivity is more robust against catalyst deactivation by coking, as the pores in this pellet are more difficult to be plugged or inaccessible.The maximum coke content is also higher for narrower pore size distribution and higher pore connectivity, as the number of inaccessible pores is lower. Besides, the catalyst pellet radius only slightly affects the coke content, although the diffusion limitation increases with the pellet radius. These results should serve to guide the rational design of robust DRM catalyst pellets against deactivation by coking.

The Nature of Active Sites for Plasmon-Mediated Photothermal Catalysis and Heat-Coupled Photocatalysis in Dry Reforming of Methane

Solar energy-induced catalysis has been attracting intensive interests and its quantum efficiencies in plasmon-mediated photothermal catalysis(P-photothermal catalysis)and external heat-coupled photocatalysis(E-photothermal catalysis)are ultimately determined by the catalyst structure for photo-induced energetic hot carriers.Herein,different catalysts of supported(TiO_(2)-P25 and Al_(2)O_(3))platinum quantum dots are employed in photo,thermal,and photothermal catalytic dry reforming of methane.Integrated experimental and computational results unveil different active sites(hot zones)on the two catalysts for photo,thermal,and photothermal catalysis.The hot zones of P-photothermal catalysis are identified to be the metal-support interface on Pt/P25 and the Pt surface on Pt/Al_(2)O_(3),respectively.However,a change of the active site to the Pt surface on Pt/P25 is for the first time observed in E-photothermal catalysis(external heating temperature of 700℃).The hot zones contribute to the significant enhancements in photothermal catalytic reactivity against thermocatalysis.This study helps to understand the reaction mechanism of photothermal catalysis to exploit efficient catalysts for solar energy utilization and fossil fuels upgrading.

An efficient technique for improving methanol yield using dual C02 feeds and dry methane reforming

Steam methane reforming(SMR)-based methanol synthesis plants utilizing a single CO2 feed represent one of the predominant technologies for improving methanol yield and CO2 utilization.However,SMR alone cannot achieve full CO2 utilization,and a high water content accumulates if CO2 is only fed into the methanol reactor.In this study,a process integrating SMR with dry methane reforming to improve the conversion of both methane and CO2 is proposed.We also propose an innovative methanol production approach in which captured CO2 is introduced into both the SMR process and the recycle gas of the methanol synthesis loop.This dual CO2 feed approach aims to optimize the stoichio-metric ratio of the reactants.Comparative evaluations are carried out from a techno-economic point of view,and the proposed process is demonstrated to be more efficient in terms of both methanol productivity and CO2 utilization than the existing stand-alone natural gas-based methanol process.

Multi-objective optimization for membrane reactor for steam methane reforming heated by molten salt

A membrane reactor for steam methane reforming heated by molten salt(MS-SMRMR)is studied based on finite time thermodynamics for decreasing carbon emissions and improving hydrogen production rate(HPR).Effects of flow directions of sweep gas and molten salt on MS-SMRMR are researched.Profiles of temperatures,HPR,and local entropy generation rates(EGRs)of MS-SMRMR are analyzed.Hybrid particle swarm optimization algorithm is utilized to obtain the minimum of specific EGR(SEGR),ratio of EGR to HPR.Multi-objective optimization about HPR maximization and EGR minimization is performed by utilizing NSGA-II.The EGR caused by the mass transfer process is the largest among all irreversible processes in the MS-SMRMR.The membrane length should be slightly shorter than the reactor length when the flow direction of sweep gas is different from that of reaction mixture.When flow directions of molten salt and sweep gas are opposite to that of reaction mixture,SEGR is the smallest.Compared with SEGR calculated by utilizing initial parameters,SEGRs after primary,twice and triple optimizations reduce by 1.2%,5.5%and 5.7%,respectively.SEGR can be further decreased by adjusting other operating parameters.Pareto front provides many optimization results,and it contains SEGR minimization.In Pareto front,an optimum decision point is obtained based on decision-making of TOPSIS,and its EGR and HPR,respectively,increase by 7.12%and13.24%,compared with those obtained by using initial parameters.The results have certain theoretical guiding significance for optimization designs of MS-SMRMR.

A PVTC system integrating photon-enhanced thermionic emission and methane reforming for efficient solar power generation

A new photovoltaic-thermochemical(PVTC) conceptual system integrating photon-enhanced thermionic emission(PETE) and methane steam reforming is proposed. Major novelty of the system lies in its potential adaptivity to primary fuels(e.g. methane) and high efficiencies of photovoltaic and thermochemical power generation, both of which result from its operation at much elevated temperatures(700–1000 °C)compared with conventional photovoltaic-thermal(PVT) systems. Analysis shows that an overall power generation efficiency of 45.3% and a net solar-to-electric efficiency of 39.1% could be reached at an operating temperature of 750 °C, after considering major losses during solar energy capture and conversion processes. The system is also featured by high solar share(37%) in the total power output, as well as high energy storage capability and very low CO_2 emissions, both enabled by the integration of methane reforming with photovoltaic generation at high temperatures.

Characteristic of macroporous CeO_2-ZrO_2 oxygen carrier for chemical-looping steam methane reforming

Chemical-looping steam methane reforming （CL-SMR） is a novel process towards the production of pure hydrogen and syngas, consisting ofa syngas production reaction and a hydrogen production reaction. Macroporous CeQ-ZrO2 oxygen carders with different pore sizes prepared by colloidal crystal templating method and characterized by techniques of scalming electron microscopy （SEM）, transmission electron microscopy （TEM）, Brunauer-Emmett-Teller （BET）, X-ray diffraction （XRD） and temperature pro- grammed reduction （H2-TPR） were tested in CL-SMR process. For comparison, nonporous CeO2-ZrO2 oxygen carrier prepared by precipitation method was also investigated. It was found that macroporous CeO2-ZrO2 oxygen carriers owned higher reducibility and reactivity in CL-SMR process than nonporous samples. For the macroporous CeO2-ZrO2 sample, the decline of pore size could im- prove the reducibility and reactivity. The macroporous sample with a pore size of 100 nm （labeled as Ce-Zr-100） showed the highest performance for the co-production of syngas and hydrogen during the successive CL-SMR redox cycles. After 10 redox cycles, it still retained good porous structure and reducibility. It was found that the porous structure could accelerate the oxygen release from bulk to surface, leading to a good mobility of oxygen and higher reducibility. In addition, it was also favorable for diffusion and penetration of methane and water steam into the sample particles to accelerate the reaction rate.

Role of La_2_O3 as Promoter and Support in Ni/γ-Al_2O_3 Catalysts for Dry Reforming of Methane

The nature of support and type of active metal affect catalytic performance. In this work, the effect of using La203 as promoter and support for Ni/γ-A1203 catalysts in dry reforming of methane was investigated. The reforming reactions were carried out at atmosphenc pressure in the temperature range of 500-2700℃. The activity and stability of the catalyst, carbon formation, and syngas （H2/CO） ratio were determined. Various techniques were applied for characterization of both fresh and used catalysts. Addition of La2O3 to the catalyst matrix improved the dispersion of Ni and adsorption of CO2, thus its activity and stability enhanced.

First principles study on methane reforming over Ni/TiO2（110） surface in solid oxide fuel cells under dry and wet atmospheres

Understanding the carbon-tolerant mechanisms from a microscopic view is of special importance to develop proper anodes for solid oxide fuel cells.In this work,we employed density-functional theory calculations to study the CH4 reaction mechanism over a Ni/TiO2 nanostructure,which experimentally demonstrated good carbon tolerance.Six potential pathways for methane reforming reactions were studied over the Ni/TiO2(110)surface under both dry and wet atmospheres,and the main concerns were focused on the impact of TiO2 and Ni/TiO2 interface on CO/H2 formation.Our calculations suggest that the reaction between carbon and the interfacial lattice oxygen to form CO*is the dominant pathway for CH4 reforming under both dry and wet atmospheres,and intervention of steam directly to oxidize C*with its dissociated OH*group is less favorable in energy than that to wipe off oxygen vacancy to get ready for next C*oxidation.In all investigated paths,desorption of CO*is one of the most difficult steps.Fortunately,CO*desorption can be greatly promoted by the large heat released from the previous CO*formation process under wet atmosphere.H2O adsorption and dissociation over the TiO2 surface are found to be much easier than those over Ni,yttria stabilized zirconia(YSZ)and CeO2,which should be the key reason for the greatly depressed carbon deposition over Ni-TiO2 particles than traditional YSZ-Ni and CeO2-Ni anode.Our study presents the detailed CO*formation mechanism in CH4 reforming process over the Ni/TiO2 surface,which will benefit future research for exploring new carbon-tolerant solid oxide fuel cell anodes.