Reforming Reaction Research Articles

An Energy Production System Powered by Solar Heat with Biogas Dry Reforming Reactor and Solid Oxide Fuel Cell

An Energy Production System Powered by Solar Heat with Biogas Dry Reforming Reactor and Solid Oxide Fuel Cell

CO2-negative fuel production using low-CO2 electricity: Syngas from a combination of methane pyrolysis and dry reforming with techno-economic analysis

This work investigates the use of CO2 as a feedstock through a thermochemical approach using low-carbon electricity, in which the CO2 reforming and methane pyrolysis reactions are combined in a single electrically heated reactor (PY/DMR). The process is enabled by a molten metal catalyst which was recently reported. Kinetic data are experimentally determined for a molten Ni-In alloy and are then used to generate a process model and a techno-economic analysis. The activation energy for methane pyrolysis and dry reforming over molten Ni-In are 187 and 99 kJ/mol respectively. This results in a 236 m3 rate-limited bubble-column reactor producing 500 kta syngas. PY/DMR is compared with a dry-reforming-based technology that is combined with steam reforming (SMR/DMR), state-of-art autothermal reforming (ATR), and CO2 co-electrolysis using solid oxide electrochemical cells from both an economic and environmental standpoint. In our present-day base case, SMR/DMR is the most affordable if no decoking is required ($179.2/t), while the commercialized ATR ($193.7/t) is similar to PY/DMR ($222/t). CO2 co-electrolysis is the least affordable case ($393.2/t). A sensitivity analysis indicates that the cost of PY/DMR is the most economically competitive case when clean (carbon intensity ≤ 160 g/kWh) and affordable (≤¢2.9/kwh) electricity is used, the solid carbon is sold at over $377/t, or when abatement cost reaches $104/t-CO2eq. Both PY/DMR and co-electrolysis result in net-negative CO2 emission, after heating and fugitive emissions are accounted for. The overall carbon footprints are −0.329 kg and −1.06 kg of CO2eq/kg-syngas respectively. PY/DMR has the lowest levelized CO2 mitigation cost ($60/t).

Sustainable cement and clay support in Ni–Cu/Al2O3 catalysts for enhancing hydrogen production from methanol steam reforming

Sustainable cement-clay composite is used as the support of bimetallic Ni–Cu/Al2O3 catalysts for hydrogen production from methanol steam reforming (MSR) reaction. The results indicate that higher methanol conversion and hydrogen yield can be obtained using composite supported catalysts. The cement-clay composite possesses CO2 absorption capability, which can enhance MSR performance. In the cases of a large proportion of cement, the CO2 concentration in the product is decreased by 1–2% where methanol conversion and hydrogen yield are not reduced. By varying the catalyst compositions such as Ni content, Ni–Cu/Al2O3 loading, and the weight ratio of cement and clay, 100% methanol conversion can be achieved as Ni content and Ni–Cu/Al2O3 loading increase. However, the CO concentration also increases due to the enhanced reverse water gas shift reaction. The results of the prepared 12 cement-clay-supported cases show the best performance with methanol conversion of 100%, hydrogen yield of 2.85 mol·(mol CH3OH)−1, and CO concentration of 5.90%. The scanning electron microscope images indicate no sintering of the spent catalyst, and the thermogravimetric analysis shows low coke formation on the catalyst surface. Overall, cement-clay replacing metal components in catalysts can efficiently reduce costs and intensify hydrogen production.

Customized Ni-MgO-ZrO2 catalysts for the dry reforming of methane using coke oven gas: Optimizing the MgO content

Ni-ZrO2 and Ni-MgO-ZrO2 catalysts were prepared by the stepwise control of the MgO content in the Ni-ZrO2 catalyst to develop a customized catalyst for the dry reforming (DRM) reaction utilizing coke oven gas (COG). The difference in MgO content affected the physicochemical properties of the catalysts. As MgO was added and the amount increased, formation of the NiO-MgO solid solution was promoted, so the Ni0 dispersion increased, but the reduction degree decreased due to strong metal-support interactions. On the other hand, basicity of the catalyst was not simply enhanced as the MgO content increased but was also affected by the degree of incorporation of Mg2+ ions into the tetragonal-ZrO2 lattice. We systematically changed the MgO content to select a catalyst that could show excellent performance in the actual process, while applying the catalyst to various reaction tests. Reaction conditions for screening of catalytic performances were derived by calculating thermodynamic equilibrium to minimize carbon deposition and maximize CO yield. As a result of catalytic evaluation, the Ni-30MgO-ZrO2 catalyst exhibited the highest catalytic activity and stability in the COG-DRM reaction. In addition, the Ni-30MgO-ZrO2 catalyst showed high stability through a long-term stability test and a temperature swing test (800–900 °C), indicating the possibility of commercialization for the target reaction.

Modeling of biomass-based hydrogen production via catalytic sorption-enhanced reformer integrated with a gasifier

The sorption enhanced reformer concept breaks the thermodynamic limits of steam methane reforming and water-gas shift reactions with selective CO2 removal to produce more H2. In this paper, we propose a dynamic kinetic model for sorption-enhanced steam reformers (SERs) integrated with biomass gasifiers. An analysis of operating conditions was conducted to examine high purity hydrogen production. The kinetic model was validated with published literature results at different reactor pressures (5-20 bar), steam/carbon ratios (2-5), and reactor temperatures (673K–1023K). This study shows that biomass gasifiers can be integrated with SER reactors to produce high purity H2.

Development and Testing of Ni-Cu Bimetallic Catalysts for Effective Syngas Production via Low-Temperature Methane Steam Reforming

In the present work, novel bi-metallic catalysts for syngas production at low temperature steam reforming are developed, characterised and tested. Steam methane reforming by using bi-metallic Ni-Cu catalysts found to balance the product of CO to CO2 ratios, while affected the water gas shift reaction by increasing the hydrogen selectivity up to 600°C. The addition of different amounts of Cu (3, 5, 7, 10 wt%) to the Ni catalyst for methane steam reforming showed different reactivity trends. One of the major outcomes of this work is the maximum load capacity of Cu (5wt.%Cu) to maintain the reactivity. For comparison purposes, mono-metallic catalysts of Cu and Ni were developed and tested along with the bi-metallic ones. The activity of the reaction decreased by doping more than 5wt.%Cu which affected the amount of hydrogen produced. This is related to the possible limited number of available sites required for hydrogen adsorption to maintain the reaction of methane steam reforming. Another important outcome of this work is the bi-metallic Ni-Cu catalysts did not decrease the amount of carbon formation.

Kinetics of Natural Kaolinite as a Catalyst for Toluene Dry Reforming

This study aims to develop a kinetic model for natural kaolinite as a potential tar removal catalyst in biomass gasification processes. The catalyst was crushed, sieved (0.2mm), and analyzed using TGA, BET, and XRF. The apparent first-order kinetic parameters of the dry reforming reaction at temperatures ranging from 750 to 900°C under 1atm were used to determine kaolinite's catalytic activity. It was found that both dry reforming and thermal cracking reactions occurred simultaneously. Furthermore, the raw kaolinite catalyst significantly removed toluene (80% at 900°C), at activation energy and frequency factor of 209 kJ/mol and 5.86×109s−1, respectively. Capitalizing on its catalytic activity in its natural form and its high efficacy as fluidized bed material, kaolinite can have great potential in primary and secondary tar reduction measures.

Methanol steam reforming reactor with fractal tree-shaped structures for photovoltaic–thermochemical hybrid power generation

The photovoltaic–thermochemical (PVTC) hybrid system converts thermal energy dissipated by concentrating photovoltaic cells to gain in power generation via the endothermic methanol steam reforming (MSR) reaction. Conventional MSR reactors are challenged by undesirable performances in heat transfer and methanol conversion, impacting the performances of power generation and energy storage of PVTC systems. In this work, an innovative fractal tree-shaped structure is introduced into the flow channels configuration of an MSR reactor to enhance heat transfer performance and methanol conversion. The methanol conversion of the novel reactor is experimentally assessed, which is 12.1 percentage points (relative improvement of 26.5%) higher than that of conventional reactors with serpentine flow channels design. A 3-D multiphysics model of the MSR reactors coupling heat transfer, gas flow, and chemical reaction is developed to reveal the mechanism of methanol conversion improvement. The fractal tree-shaped structure can improve the net solar-electric efficiency of the photovoltaic–thermochemical hybrid system by 5.6–7.5% (up to 36.6%). The efficient solar energy power generation of the PVTC system with energy storage ratio ensures considerable dispatchability for hybrid solar power generation.

The kinetic and experimental study of the phenol steam reforming towards hydrogen production over Ni-Rh/MgO catalyst

To study the kinetic implied on the Langmuir-Freundlich (LF) adsorption isotherm, the experimental tests of phenol steam reforming (PSR) reaction in the presence of Ni-Rh/MgO catalyst were performed in the temperature range of 500 °C-800 °C and flow rate of 10 mL/h to 30 mL/h in a fixed bed reactor. LF model accurately fitted the experimental responses with assuming CO and CO2 formation reactions as the kinetic limitations. By comparing two experimental and calculated values, the deviation of kinetic model in calculating experimental H2 yield was lower (2.58 %) compared to phenol conversion, CO and CO2 yields. The stability analysis revealed that conversion and yields were almost fixed without obvious deactivation up to 55 h initial time on stream, however, activity was declined over time on stream in the range of 55 h to 70 h because of coke deposition. The characterization results demonstrated that the deposited coke on the catalyst surface after the stability test was more aromatic and less aliphatic and included carboxylic group, methyl group and aromatic structure. The phenol conversion near to 90 % was attained at 800 °C and flow rate of 10 mL/h. The temperature had a positive effect on the catalytic activity regarding to phenol conversion, H2 and CO yields. However, temperature variable had a negative impact on CO2 yield. The changes of phenol conversion, H2 and CO2 yields showed descending trends with flow rate in the range of 10 mL/h to 30 mL/h. In the range of 500 °C-600 °C, CO yield was approximately constant by altering flow rate from 10 mL/h to 30 mL/h.

Numerical Investigation of Heat/Flow Transfer and Thermal Stress in an Anode-Supported Planar SOFC

To elucidate the thermofluid reacting environment and thermal stress inside a solid oxide fuel cell (SOFC), a three-dimensional SOFC model is implemented by using the finite element method in the commercial software COMSOL Multiphysics®, which contains both a geometric model of the full-cell structure and a mathematical model. The mathematical model describes heat and mass transfer, electrochemical reactions, internal reforming reactions, and mechanical behaviors that occur within the cell. A parameter study is performed focusing on the inlet fuel composition, where humidified hydrogen and methane syngas (the steam-to-carbon ratio is 3) as well as the local distribution of temperature, velocity, gas concentrations, and thermal stress are predicted and presented. The simulated results show that the fuel inlet composition has a significant effect on the temperature and gas concentration distributions. The high-temperature zone of the hydrogen-fueled SOFC is located at the central part of units 5, 6, and 7, and the maximum value is about 44 K higher than that of methane syngas-fueled SOFC. The methane-reforming and electrochemical reactions in the anode active layer result in a significant concentration gradient between the anode support layer and the active layer of the methane syngas-fueled SOFC. It is also found that the thermal stress distributions of different fuel inlet compositions are rather different. The maximum stress variation gradient between electrode layers of hydrogen SOFC is larger (44.2 MPa) than that of methanol syngas SOFC (14.1 MPa), but the remaining components have a more uniform stress distribution. In addition, the electrode layer of each fuel SOFC produces a significant stress gradient in the y-axis direction, and stress extremes appear in the corner regions where adjacent assembly components are in contact.

Thermodynamic analysis of a novel tri-generation system integrated with a solar energy storage and solid oxide fuel cell – Gas turbine

The conventional cooling, heating and power tri-generation system still has problems such as high greenhouse gas emissions and high fossil fuel consumption. A new integrated energy system is proposed which includes solar-methanol hydrogen production, energy storage device, solid oxide fuel cell and dual-effect absorption chiller/heat pump with less carbon dioxide emissions, higher energy conversion efficiency and less fossil fuel consumption. The solar energy storage device drives the methanol reformation reaction and the Li-Br chiller/heat pump in parallel, decoupling the power and cooling/heating of the system to simultaneously satisfy the user demands and increases system flexibility. The proposed system is modeled and simulated in Aspen Plus and Fortran. The system thermodynamic performance is analyzed at the design conditions and the results shows the new system obviously enhances the energy conversion efficiency compared with the reference system. The effects of the methanol flow rate on the system output parameters and the thermodynamic performances of the system in different seasons when meeting the cooling, heating and power needs of the district users are studied. The results shows that the maximum system energy efficiency is 92.98% when the system operates in summer, and the system power generation efficiency is 48.03%; in winter, the maximum total system energy efficiency reaches 146.30%, and the system power generation efficiency is 53.26%; in the transition season, the system only needs to provide users with power load and domestic hot water, and the exhaust gas provides the methanol reaction heat. The system power generation efficiency increases to 65.38% and the energy efficiency is 87%.

수소생산을 위한 수증기-메탄-개질 반응기의 성능 분석 및 설계

This study is to design a steam methane reforming (SMR) reactor that can produce hydrogen from methane, the main component of LNG, by extracting a portion of the gas (BOG) generated from the fuel tank to use a fuel cell as an auxiliary power source for an LNG propulsion ships. Prior to the design, performance was analyzed using several parameters. As the pressure in the reforming reactor increased, the methane conversion rate decreased. The yield to hydrogen is maximal at a temperature of 750 to 800℃, with almost 40% being reduced to hydrogen. At a low temperature, the methane conversion rate was low, and the concentrations of other compositions were also low. At a temperature above 700℃, the concentration of carbon monoxide continued to increase, while the concentration of carbon dioxide decreased. It can be seen that the water gas conversion reaction does not occur smoothly at high temperatures. The reactor design was carried out in the temperature range of 700 to 900℃, and it was found that for each 50℃ increase, the total heat transfer area required increased in the range of about 17~25%.

A comparative DFT study of ethanol steam reforming over Co(1 0 0) and CoO(1 0 0) surfaces: Molecular reaction mechanism

Unraveling the roles of cobalt sites with different oxidation states is crucial for understanding mechanism of cobalt-catalyzed ethanol steam reforming (ESR) reaction. In this work, the roles of Co(0) and Co(II) sites in ESR reaction are comparatively explored by DFT calculation studies about reaction pathways over Co(100) and CoO(100) surfaces, and a novel molecular reaction mechanism has been provided. The results demonstrate that the Co(II) site in Co-based catalyst exhibits distinct preference for dehydrogenation over dehydration of ethanol especially in the presence of H2O molecule. For the conversion of acetaldehyde, the Co(0) site exhibits significant preference for decomposition and water addition over aldol addition of acetaldehyde, thus facilitating the carbon chain shortening to improve ethanol steam reforming. Therefore, the Co(0) and Co(II) sites exhibit synergistic effects on ESR reaction, especially the role of Co(0) site in selective conversion of acetaldehyde is more crucial for high-efficiency reforming of ethanol.

Surface Acidity/Basicity and Oxygen Defects of Metal Oxide: Impacts on Catalytic Performances of CO2 Reforming and Hydrogenation Reactions

Surface Acidity/Basicity and Oxygen Defects of Metal Oxide: Impacts on Catalytic Performances of CO2 Reforming and Hydrogenation Reactions

Identification of Highly Selective Surface Pathways for Methane Dry Reforming Using Mechanochemical Synthesis of Pd-CeO2.

The methane dry reforming (DRM) reaction mechanism was explored via mechanochemically prepared Pd/CeO2 catalysts (PdAcCeO2M), which yield unique Pd–Ce interfaces, where PdAcCeO2M has a distinct reaction mechanism and higher reactivity for DRM relative to traditionally synthesized impregnated Pd/CeO2 (PdCeO2IW). In situ characterization and density functional theory calculations revealed that the enhanced chemistry of PdAcCeO2M can be attributed to the presence of a carbon-modified Pd0 and Ce4+/3+ surface arrangement, where distinct Pd–CO intermediate species and strong Pd–CeO2 interactions are activated and sustained exclusively under reaction conditions. This unique arrangement leads to highly selective and distinct surface reaction pathways that prefer the direct oxidation of CHx to CO, identified on PdAcCeO2M using isotope labeled diffuse reflectance infrared Fourier transform spectroscopy and highlighting linear Pd–CO species bound on metallic and C-modified Pd, leading to adsorbed HCOO [1595 cm–1] species as key DRM intermediates, stemming from associative CO2 reduction. The milled materials contrast strikingly with surface processes observed on IW samples (PdCeO2IW) where the competing reverse water gas shift reaction predominates.

A novel Ni–MoCxOy interfacial catalyst for syngas production via the chemical looping dry reforming of methane

<h2>Summary</h2> Modulating the oxygen-metal interface that enables efficient and selective C–H activation remains challenging. Herein, we present a novel MoC_xO_y oxygen carrier for syngas production via the chemical looping CH₄–CO₂ reforming (CL-DRM) reaction. Molybdenum carbide additive induces the re-dispersion of Ni particles from Al₂O₃ surface to α-MoC driven by the strong interaction between Ni and α-MoC. A dynamic structure transformation between MoC_x and MoC_xO_y occurs and new Ni–MoC_xO_y interfaces form during the redox cycling, which is discovered to be crucial for the low-temperature CH₄ activation using surface construction experiments and <i>in-situ</i> spectroscopic methods. As a result, Ni–(α-MoC)/Al₂O₃ exhibits near 100% selectivity to syngas with a H₂/CO ratio of 2:1 at 500°C, which is a significantly lower temperature than that of conventional systems. This study first employs molybdenum carbide as an oxygen storage material (OSM) in CL-DRM reaction, paving the way of utilizing transition metal carbides as OSMs in chemical looping processes.

The synergistic role of Ni-Co bimetallic catalyst for H2-rich syngas production via glycerol dry reforming

A by-product of biodiesel manufacturing, glycerol, is known for its potential to generate syngas via the glycerol dry reforming (GDR) reaction. This study evaluates monometallic and bimetallic Nickel–Cobalt (Ni–Co) (with 15%Co, 3%Ni–12%Co, 4.5%Ni-10.5%Co, 7.5%Ni-7.5%Co, 10.5%Ni-4.5%Co and 15%Ni loading) on Alumina (Al2O3) support extracted from aluminium dross. The catalysts were prepared using an ultrasonic-assisted impregnation process and used in GDR at temperatures ranging from 873 to 1173 K at stoichiometric feed ratio. Analyses result showed that the diluting impact of Ni–Co bimetallic precursors resulted in a reduction of metal crystallite size and improved H2 and CO2 uptake. The conversion of glycerol and product yield were in the order of 3%Ni–12%Co/Al2O3 > 4.5%Ni-10.5%Co/Al2O3 > 7.5%Ni-7.5%Co/Al2O3 > 10.5%Ni-4.5%Co/Al2O3 > 15%Co/Al2O3 > 15%Ni/Al2O3, with 3%Ni–12%Co/Al2O3 having values of 75.6%, 64.7% and 44.8%, for glycerol conversion, H2 and CO yield respectively. All catalysts achieved product ratios ranging from 1.20 to 1.44. The high oxygen vacancies in Ni–Co bimetallic catalysts aided the reduction of carbon formation. Enhanced Ni–Co particles dispersion on Al2O3 support reduced the agglomeration of metal particles, thus, creating smaller crystallite size. The changes in binding energy peaks of Ni and Co were indicative of strong electronic interaction which created Ni–Co bimetallic alloys. 3%Ni–12%Co was regarded as the best catalyst for this study since it was effective in enhancing the conversion of glycerol and product yield.

Electron density donation of concomitant peroxide anions in La0.25Ce0.75O1.88 boosting cobalt-catalyzed ethanol steam reforming for hydrogen production

Tuning the valence state and reducibility of Co active site in Co-based catalysts to improve catalytic performances is desirable for hydrogen production from ethanol steam reforming (ESR) reaction. In this work, we fabricate Co/LaxCe1−xO2−x/2 (x = 0.5, 0.25, 0.17) catalysts and investigate their catalytic performances for ESR reaction. Our studies manifest that the catalytic performances of Co-based catalysts have been effectively improved by La doping in CeO2. Among the investigated catalysts, Co/La0.25Ce0.75O1.88 exhibits the highest catalytic activity and durability, the hydrogen yield reaches as high as 80 % at ethanol conversion of 100 %, with an excellent durability during long-time (58 h) catalytic experiment. X-ray photoelectron spectroscopy (XPS) and hydrogen temperature programmed reduction (H2-TPR) studies demonstrate that the valence state and reducibility of the Co/La0.25Ce0.75O1.88 are effectively regulated via donation of electron density from the concomitant peroxide anions in La0.25Ce0.75O1.88 to the supported cobalt catalyst, the CC bond cleavage capability has been significantly enhanced to boost the hydrogen-production efficiency from ESR reaction. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies reveal that Co/La0.25Ce0.75O1.88 shows a remarkable preference for producing C1 products, the Co species in low valence state and with high reducibility result in highly efficient CC cleavage and excellent catalytic durability.

Effect of electrochemical reaction on steam adsorption during methane reforming on a Ni-GDC anode

The influence of steam on the internal reforming reaction in solid oxide fuel cells is under debate based on previously reported results. Therefore, appropriate kinetic models that accurately describe the methane reforming behaviour in solid oxide fuel cells under various operating conditions are required. The objective of this study is to find the appropriate kinetic model to describe the effect of current density on steam adsorption behaviour. The Langmuir-Hinshelwood model considers the associative methane adsorption and the dissociative steam adsorption. The formation of catalyst-hydroxide complexes is directly influenced by the steam concentration and current drawn via the non-faradaic electrochemical modification of the catalysis effect. The steam adsorption constant appeared to significantly drop when a current was produced. Of the current densities investigated, the models seemed to provide a more accurate description of reforming rates at a 600 A/m2 current density relative to open-circuit and 1000 A/m2 conditions. The models are used to predict the reaction rate in the fuel cell channel where the in-situ measurement is not practical.

PM2.5-mediated photochemical reaction of typical toluene in real air matrix with identification of products by isotopic tracing and FT-ICR MS

The sight into photoconversion of toluene, a ubiquitous typical pollutant, attentively by the involvement of PM2.5 in the real air environment is crucial for controlling haze pollution. Compared with the large-size PM2.5 on normal day (PM2.5-ND), the PM2.5 on haze day (PM2.5-HD) formed of small particle agglomerates featured greater oxidation capability, evidenced by the valence distribution of sulfur species. Notably, PM2.5-HD had abundant O2−• and •OH and participated in the photochemical reaction of toluene, giving it a greater toluene conversion with a first-order kinetic rate constant of 0.4 d−1 on haze day than on normal day (0.2 d−1). During the toluene photoconversion, isotopic labelling traced small molecules including benzene and newfound pentane, ethylbenzene, 1,3,8-p-menthatriene and 4-methyl-1-pentanone benzene that could be formed by methyl breakage, ring opening, fragmentation reforming and addition reaction of toluene. Given ADMET properties, 1,3,8-p-menthatriene was assigned high priority since it had poor metabolism, low excretion and severe toxicity, while benzene and 4-methyl-1-pentanone benzene should also be noticeable. FT-ICR MS results indicated that toluene could create multiple macromolecular products that are more sensitive to SOA generation in haze air matrix with broader carbon number and O/C, more oxygenated substitution with CHO/CHON occupying by 81.4%, lower DBEaverage at 4.66 and higher OSC‾ at −1.60 than normal air matrix. Accordingly, a photochemical reaction mechanism for toluene in real air atmosphere was proposed. The stronger oxidation property of PM2.5 not only facilitated toluene to generate small molecules but also boosted the conversion of intermediates to oxygenated macromolecular products, contributing to the formation of SOA.