Methane Steam Reforming Reaction Research Articles

Feedback control of an experimental electrically-heated steam methane reformer

Steam methane reforming (SMR) is the most common industrial process to produce hydrogen (H2) from methane and water vapor. The SMR reactions are overall highly endothermic and traditionally, fossil fuels are burned to provide the necessary heat of reaction. However, it was found that electrifying the tubular SMR reactors using renewable electrons instead of conventional heating gives the opportunity of producing H2 with lower carbon emissions, lower reactor volumes, and higher carbon conversion. While current studies in this new technology focus on improving the catalysts or heating sources, a more efficient process control scheme can also significantly contribute to the understanding of potential challenges and opportunities of combining renewables and natural gas in the production of H2 at industrial scales. In order to further develop the electrically-heated SMR process and the associated control strategies, we have constructed an experimental Joule-heated SMR system at UCLA. The system contains a tubular reactor with a washcoated Ni/ZrO2 catalyst, two thermocouples connected to the top and bottom of the reactor, a power supply for providing electrical heating, and an on-line gas chromatograph (GC) for measuring outlet gas concentrations. The synthesis procedure of the catalyst, SMR data collection, and thermal considerations for catalyst degradation are described in this paper and are all accounted for experimentally when using a proportional integral (PI) controller to gradually increase the reactor temperature without harming the catalyst. Advanced control strategies, such as model predictive control (MPC), require a process model that uses measurement feedback to make predictions of the process time-evolution in order to optimize the control actions in real-time. We have previously developed a lumped-parameter modeling strategy for the SMR process. The MPC objective is to control the H2 production rate by manipulating the current flowing through the outer reactor shell. However, to use this model in an MPC, feedback values for all state variables should be provided by the sensors. In our experimental system, the on-line GC only gives discrete measurements with a long sampling period. To this end, the process model is incorporated into an extended Luenberger observer (ELO) that uses the reactor temperature and GC measurements to provide estimates of all the variables needed by the MPC. The ELO-based MPC system is then experimentally implemented on the process and it is demonstrated to be more efficient in terms of speed of the closed-loop response than the PI controller using delayed, measurement feedback by the GC.

High-Throughput Screening of Sulfur-Resistant Catalysts for Steam Methane Reforming Using Machine Learning and Microkinetic Modeling.

The catalytic activity of bimetallic catalysts for the steam methane reforming (SMR) reaction was extensively studied previously. However, the performance of these materials in the presence of sulfur-containing species is yet to be investigated. In this study, we propose a novel process aided by machine learning (ML) and microkinetic modeling for the rapid screening of sulfur-resistant bimetallic catalysts. First, various ML models were developed to predict atomic adsorption energies (C, H, O, and S) on bimetallic surfaces. Easily accessible physical and chemical properties of the metals and adsorbates were used as input features. The Ensemble learning, artificial neural network, and support vector regression models achieved the best performance with R2 values of 0.74, 0.71, and 0.70, respectively. A microkinetic model was then built based on the elementary steps of the SMR reaction. Finally, the microkinetic model, together with the atomic adsorption energies predicted by the Ensemble model, were used to screen over 500 bimetallic materials. Four Ge-based alloys (Ge3Cu1, Ge3Ni1, Ge3Co1, and Ge3Fe1) and the Ni3Cu1 alloy were identified as promising and cost-effective sulfur-resistant catalysts.

Steam reforming of methane over nickel-aluminum spinel-derived catalyst

Despite steam reforming of methane (SRM) has been the dominant way to produce hydrogen in industrial owing to its large hydrogen production capacity, easy accessibility of feedstocks and relative low cost, the development of high-efficient catalysts is still of great significance. In this work, we report the synthesis, characterizations and evaluation of Nickel-aluminum spinel (NiAl2O4) catalyst in SRM reaction. Compared with Ni/γ-Al2O3 catalyst prepared by impregnation, NiAl2O4 presents higher methane conversion. Virous of characterizations exhibit NiAl2O4 possesses higher distribution of Ni and smaller Ni nanoparticle size, which is one of advantages for its high activity. Another vital reason is the generation of oxygen vacancies in spinel during the reduction, which is beneficial for the activation of water. Moreover, NiAl2O4 catalyst shows extremely stability without obvious deactivation in 160 h. This study illustrates that the construction of catalyst with high activity and stability via NiAl2O4 spinel and reals its high activity origination.

Direct steam reforming of the product gas from ethanol gasification with supercritical water

A continuous process for producing hydrogen from the gasification of ethanol with supercritical water (SCWG) is investigated, which involves a fixed bed steam methane reforming (SMR) reactor downstream of the SCWG reactor. Increasing temperature and decreasing space velocity in the SMR reactor resulted in increased hydrogen concentration and methane conversion. The catalyst activity was more affected at low than high pressures, presumably due to the kinetics of the SMR reaction. The significant increase in total hydrogen yield based on ethanol in the feed showed the importance of installing the reformer after gasification. The excessive steam from the SCWG reactor helped to prevent carbon formation, but it might have resulted in the sintering of the active metal. A long-time experiment proved the stability of the catalyst up to 49 h of time on stream (TOS) with a minor decrease in methane conversion from 84% to 78%.

Sensitivity analysis of hydrogen production by methane reforming using electrified wire reactors

Electrified modular reactors have been gaining attention due to their potential in reducing carbon emissions and meeting net-zero goals, where traditional reactors that burn fossil fuels to supply the endothermic heat of reaction can be replaced by electrified reactors integrated with renewable power. In this work, we demonstrate by modeling and calculations, the feasibility of hydrogen production by steam methane reforming (SMR) in electrically heated wire reactors, which can lead to a commercial pathway to produce hydrogen in bulk. We utilize a three-reaction network and an established kinetic model for SMR reactions to perform a detailed sensitivity analysis and evaluate the impact of process and other parameters such as power supply (electric heating), operating pressure, temperature, feed composition, catalyst loading and steam to carbon ratio, on methane conversion and hydrogen yield.

Response surface methodology for optimizing the activity of bimetallic Ni–Co–Ce/Al2O3 catalysts in the steam methane reforming

Hydrogen is being explored as a potential energy carrier for power and heat production, as well as energy storage, making it one of the most significant basic chemicals. In this work, steam methane reforming (SMR) over Ce-promoted Co–Ni/Al2O3 catalysts were employed to produce hydrogen, and the response surface method (RSM) based on an optimal custom method was used to examine the interplay between synthetic and operational factors affecting methane conversion, hydrogen yield and H2/CO molar ratio. Several independent factors were considered, including the catalyst Co/Ni mass ratio (0, 0.5, 1), Ce loading (0, 1.5, 3.0), operation temperature (600, 650, 700 °C), steam to methane (S/M) molar ratio (1.5, 2.5, 3.5), and support type (bulk and hollow Al2O3). Among the two determined optimized results in Design Expert, the hollow 0.17Co–Ni-1.26Ce@Al2O3 catalyst was the best choice, depicting 96.20% methane conversion, 96.89% hydrogen yield and 6.57H2/CO molar ratio. The stability test of both hollow and bulk optimized catalysts was compared in optimal conditions (S/M molar ratio and temperature) over a 12-h SMR reaction. The physical properties and morphology of the optimized catalysts were determined before and after the steam reforming reaction using FESEM, XRD, N2 physisorption, TPR, and TGA analyses.

Multi-objective optimization of hydrogen production process and steam reforming reactor design

This study proposes a multi-objective optimization approach to design a steam methane reforming (SMR) reactor and maximize the efficiency of the hydrogen production process. Out of 1782 possible variable combinations, only 50 iterations were performed, identifying three Pareto optimal that resulted in reactor size reductions of 50.53%, 35.56%, and 20.69%, respectively, compared to the reference reactor. The process efficiency for each optimal design varied slightly, with one achieving a 105.05% increase in efficiency, another remaining stable at 100.48%, and a third experiencing a slight decrease to 86.66% compared to the reference case. The results offer practical insights for planning an on-site distributed hydrogen production system, demonstrating that an increase in overall process efficiency can be achieved even with a reduced reactor size. This work is the first attempt to optimize a hydrogen production system by simultaneously considering overall process efficiency and SMR reactor design.

Steam methane reforming over a preheated packed bed: Heat and mass transfer in a transient process

The primary method of large scale hydrogen production is steam methane reforming (SMR) in the packed bed reactors filled with the catalysts. In these reactors, heat is mostly supplied through the reactor wall to compensate for the endothermic effect of SMR reactions. In this paper, an alternative route of steam methane reforming process over a preheated packed bed filled with Ni-based catalyst particles was studied. Consequent packed bed heating with hot flue gas and cooling with H2O - CH4 endothermically reacting mixture was investigated. Numerical model has been developed for the cooling and heating processes and realized via Ansys Fluent. The analyses were performed for various steam-to-methane ratios and different initial temperature distributions. Results are indicating that the packed bed volume averaged temperature increases by 98 °C after 15 s of heating with flue gas. Packed bed cools down by more than 125 °C after 15 s of the SMR process. Mixture species distribution was also analysed along the reformer length. Hydrogen outlet molar fraction constantly decreases from 0.38 to 0.25 at the process beginning and end, respectively. The highest hydrogen production was observed on the half of the packed bed closer to the reformer outlet.

Determination of the Optimum Operating Conditions for Integrated Methanol and Ethanol Plant from Natural Gas Reactors

Methanol and ethanol can be produced from many kinds of feedstock. One of the most preferred methods to synthesize methanol is from natural gas, which is reformed to form synthesis gas (syngas) and converted by a catalyst to form methanol. Conversely, ethanol production mostly comes from biomass, which competes with human food fulfilment. Several pieces of literature conduct syngas transformation to ethanol to solve this problem. However, the experiment is conducted on a lab scale or pilot scale. Before the technology can be mass-produced on a plant scale, we must determine the most suitable operating condition for the reactor to escalate the reactor's productivity. This study is aimed to determine the optimal operating condition for the integrated methanol and ethanol plant, which is the reactors. The software used for the study is Aspen Plus V12.1. The independent variables for all the reactors in this study are the pressure (P) and the temperature (T). We add the feed molar flow ratio as the independent variable for the Steam Methane Reforming (SMR) and the ethanol synthesis reactor. The dependent variable that will be used for the determination of the optimal operating condition of the reactors is the reactant conversion and the product yield. The data validation between the experimental data conducted by other authors and the process modeling result is in good agreement with less than 6% of error for all three reactors. After performing the process simulation and sensitivity analysis to determine the optimal operating condition for the reactors, it is found that the optimal operating condition for the reactors is as follows: (1) SMR reactor: 25 bar pressure, 1,223 K temperature, feed molar flow ratio (H2O/CH4 ratio) of 3, (2) methanol synthesis reactor: 100 bar pressure and 503 K temperature, and (3) ethanol synthesis reactor:110 bar pressure, 583 K temperature, and feed molar flow ratio (H2/CO ratio) of 0.75.

Synthesis, characterization, and application of bio-templated Ni–Ce/Al2O3 catalyst for clean H2 production in the steam reforming of methane process

A mesoporous γ-alumina was successfully synthesized through an environmentally-friendly method using Fig leaves as a bio-template for the first time in this research. After confirming the formation of porous Al2O3 structure with different characterization techniques, it was used as a supporting material of Ni–Ce particles to effectively enhance the conversion of steam reforming of methane (SRM) process. For this purpose, we optimized Ni content, Ce content, and SRM temperature using bulk and porous structure of Ni–Ce/Al2O3 catalysts. The results of field emission scanning electron microscopy (FESEM), temperature-programmed desorption (H2-TPD), and N2 adsorption/desorption showed the formation of more dispersed Ni particles with smaller sizes on the mesoporous alumina (MAl), especially when they were promoted with CeO2. Besides the efficient influence of CeO2 on Ni particle dispersion, it was enhanced the Ni–Al interaction, increased the activity of the catalysts, and decreased the coke deposition on the catalysts during the SRM process. As a result, 20Ni-3.0Ce/MAl catalyst depicted the highest H2 yield of 96.02% and CH4 conversion of 90.20%, and the lowest produced CO2 to consumed CH4 of 0.52% at 700 °C SRM reaction. This is while the bulky catalyst with equal Ni and Ce contents had 86.09, 92.30, and 0.56 CH4 conversion, H2 yield, and CO2/CH4 molar ratio, respectively at this temperature. Besides, 20Ni-3.0Ce/MAl depicted the highest stability during 12 h continuous SRM reaction at 700 °C with the lowest reduction amounts of 3.97% and 5.12% for CH4 conversion and H2 yield, respectively.

Effect of the Calcination Temperature of LaNiO3 on the Structural Properties and Reaction Performance of Catalysts in the Steam Reforming of Methane

The steam reforming of methane (SRM) reaction is a significant process for efficient syngas generation and for promising distributed hydrogen production. In this work, a series of LaNiO3 oxides were prepared using the Pechini method, calcined from 600 °C to 900 °C and tested for the SRM reaction. Fresh, reduced, and used samples were characterized using STA-MS-FTIR, in situ and ex situ XRD, N2 physical adsorption, H2-TPR, TEM, TPO, and Raman. The results show that LaNiO3 begins to crystallize at about 550 °C, and the increase in calcination temperature results in the following differences in the properties of the LaNiO3 samples: larger LaNiO3 grains, smaller specific surface area, higher reduction temperature, smaller Ni0 grains reduced from the bulk phase, and stronger metal–support interaction. The maximum CH4 conversion could be achieved over LaNiO3 calcinated at 800 °C. In addition, the effect of steam-to-carbon ratio (S/C) on the performance of the SRM reaction was studied, and a S/C of 1.5 was found to be optimal for CH4 conversion. Too strong a metal–support interaction and too much unreacted steam causes a loss of catalytic activity. Finally, it was also proved using TPO and Raman that an increase in calcination temperature improves the carbon deposition resistance of the catalyst.

Application of hollow promoted Ni-based catalysts in steam methane reforming

This work deals with the application of Y-promoted Ni-based catalysts supported on both bulk and hollow Al2O3 supports with spherical shape in the steam reforming of methane (SRM) process. For evaluating the influence of Ni and Y loadings, 15, 20, and 25 wt% Ni and 1.5, 3.0, and 4.5 wt% Y were loaded on both alumina supports. Furthermore, for enhancing the stability and activity of SRM Ni-based catalysts, reaction temperature (600, 650, and 700 °C) and steam to methane (S/M) molar ratio (1.5 to 3.0) are also adjusted in this research. Various characterizing techniques listed as X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), N2 adsorption/desorption, energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM), H2 temperature programmed reduction (H2-TPR), and temperature programmed oxidation (TPO) were employed on the fresh and used catalyst. Improvements in metal dispersion, catalytic performance, and long-time stability in SRM were achieved with the aim of a hollow Ni-Y-Al catalyst. As a result, 20Ni-3.0Y/HAl depicted the highest methane conversion of 95.77 %, hydrogen yield of 97.74 %, and H2/CO molar ratio of 6.61 at 700 °C, which is probably due to the higher surface area of hollow alumina support in comparison with bulk one.

Ultra-stable porous yolk-shell Ni catalysts for the steam reforming of methane with alkali poisoning

Hydrogen, a clean energy carrier, can be produced from renewable sources such as biomass and waste, but it is needed to develop new catalysts with high resistance against impurities. Ni/Al2O3 yolk-shell catalysts were prepared by different procedure for the steam reforming of methane reaction with alkali poisoning. Yolk-shell (ys) and porous yolk-shell (pys) materials were synthesized using a spray pyrolysis process. The physicochemical and structural properties of the prepared catalysts on the reaction performance and alkali resistance were investigated. All the yolk-shell catalysts exhibited high resistance to carbon deposition. The Ni/pys-Al2O3 catalyst showed the highest CH4 conversion and the best stability at a gas hourly space velocity of 932,492 mL·g−1·h−1 even upon exposure to alkali hydroxide vapor. It also showed strong resistance to sintering, whereas the structures of the ys-Ni-Al2O3 and Ni/ys-Al2O3 catalysts were relatively degraded under the same conditions.

Hollow sphere Ni-based catalysts promoted with cerium for steam reforming of methane

Investigation is made in this paper on the performance of hollow sphere Al2O3 supporting material in the steam reforming of methane (SRM). For this purpose, a series of Ni/hollowAl2O3 (Ni/HAl) catalysts promoted with CeO2 are synthesized and a detailed comparison is made between their structural properties, as well as catalytic activity and stability, with Ni/bulkAl2O3 (Ni/BAl). The influence of SRM temperature (600–700 °C), steam/methane (S/M) molar ratio (1.5–3.0), Ni loading (15-25 wt%), and Ce loading (1.5 and 3.0 wt%) are investigated for both Ni/Al2O3 structures. Different characterization techniques are performed on the synthesized supports, as well as catalysts, before and/or after SRM reaction. Better dispersed Ni active sites and thus higher catalytic activity and stability are achieved using 1.5Ce-promoted 20Ni/HAl catalyst which may be the result of higher surface area of HAl support compared with BAl. 20Ni-1.5Ce/HAl depicts the highest CH4 conversion of 92.06%, H2 yield of 97.03%, and H2/CO molar ratio of 6.40 at 700 °C with S/M molar ratio of 2.0. Besides, the less activity reduction of 6.07% and the less deposited coke of 4.01% is achieved during 12h reaction at 700 °C for 20Ni-1.5Ce/HAl. Therefore, this catalyst is not only a good choice for producing H2 energy carrier, but also is an appropriate catalyst for reducing the amount of CH4 greenhouse gas.

One-pot synthesis of NiCo/MgAl2O4 catalyst for high coke-resistance in steam methane reforming: Optimization of Ni/Co ratio

NiCo bimetallic catalysts based on the support of a MgAl2O4 defect spinel (Mg/Al < 1/2) were developed as catalysts for steam methane reforming (SMR) in the present study. Catalysts were synthesized by the one-pot evaporation-induced self-assembly (EISA) method followed by exsolving of active components under reduction conditions. The optimum Co contents were found to be 5 wt% in NiCo-MgAl2O4 for the SMR catalysts with high activity and coking resistance. To understand the key parameters, the physicochemical properties of the catalysts were investigated by multiple analyses. Ni and Co were simultaneously exsolved from the A-site in the MgAl2O4 support after reduction, which led to formation of Ni-Co alloy with strong metal-support interaction. Co highly influenced the oxidation state of Ni where the relative concentration of Ni0 was highest (37.6 %) for NiCo5 (5 wt% of Co). Through SMR reaction tests and Raman and thermogravimetric (TG) analyses, it was clearly confirmed that the addition of Co in NiCo-MgAl2O4 enhances for catalytic efficiency and coke resistance. Our findings are highly applicable to the development of more robust and optimized catalysts, particularly in light of the future hydrogen economy and the related and increasing demand for small-scale SMR for distributed hydrogen production.

Design of multistage fixed bed reactors for SMR hydrogen production based on the intrinsic kinetics of Ru-based catalysts

In recent years, interest in the development of a hydrogen economy has increased, and the steam methane reforming (SMR) reaction, which yields so-called “gray” hydrogen, is expected to play a key role in hydrogen refueling stations (HRSs) in the interim before “green” hydrogen process is developed. For this purpose, compact and economical designs for small- to medium-scale SMR processes for HRSs are required. Herein, we investigated the intrinsic kinetics of a Ru-based catalyst using catalyst experiments and parametric estimation. In addition, reactor modelling was performed using a kinetic model with a special focus on multistage reactor configurations. The proposed reactor design showed an increase in the reactor energy supplied rate from 6.98 to 7.55 kW compared to the base case (single-stage reactor), and the conversion increased from 86.2% to 91.2%. Further, the drastic temperature drop owing to the strongly endothermic nature of the SMR reaction was reduced, and, thus, reactor stability was improved. The proposed novel design of a multistage reactor using a Ru-based catalyst will advance the development of the hydrogen economy.

Numerical study on the effects of homogeneous reactions on the composition distributions of syngas in radiant syngas cooler

The radiant syngas cooler (RSC) is a crucial equipment for recovering the sensible heat of high-temperature syngas produced by coal gasification. Most of the previous studies on RSC focused on the flow field and heat transfer, ignoring the chemical reactions in RSC. In this work, a three-dimensional RSC model is established to investigate the effects of homogeneous reactions on the composition distributions of syngas in RSC. The simulation results show that the composition distributions of syngas are similar to the temperature distribution of RSC. From the inlet to the outlet of RSC, the mole fraction of CO decreases by 2.81%, and the mole fraction of H2, CO2 and CH4 increases by 3.44%, 8.08% and 182.09%, respectively. The relationship between temperature and the mole fraction of CH4 is concluded, which can be used as an indirect method to predict the temperature of RSC. The homogeneous reaction in RSC is dominated by water–gas shift reaction (WGSR). There are backward WGSR and forward methane-steam reforming reaction (MSR) in the inlet area, which is contrary to the situation in the outlet area. Moreover, the composition distributions of syngas present a polarized distribution under the influence of operating pressure or operating load, because the homogeneous reactions in the inlet and outlet area of RSC are affected by syngas velocity and temperature, respectively.

Synthesis, morphology control, and application of hollow Al2O3 spheres in the steam methane reforming process

This research focuses on controlling the morphology and crystalline phase of hollow Al2O3 spheres as a supporting material of Ni-based catalysts for the first time, which is then applied as a catalyst of high-temperature steam methane reforming (SMR) process. For this purpose, the effects of hydrothermal time, the concentration of alumina salt, and calcination temperature on the structure of support are investigated and adjusted and then loaded with 15–25 wt.% Ni contents. The morphology of synthesized hollow alumina samples and 20Ni/H-Al2O3 catalyst before and after reaction are characterized using XRD, FESEM, TEM, H2-TPR, CO2-TPD, EDX, FTIR, N2 adsorption/desorption, and mapping techniques. The hydrothermal time of 72 h, calcination temperature of 800 °C, and alumina salt concentration of 1.00 M resulted in the spherical morphology of hollow Al2O3 with 236.26 m2/gr surface area and high crystallinity. Among different Ni loadings, 20Ni/H-Al2O3 had the highest CH4 conversion of 87.75% and H2 yield of 92.09% at 700 °C. This catalyst also depicted stable performance during 12 h SMR reaction at 700 °C with low carbon deposited contents.

Steam reforming of methane in a gliding arc discharge reactor to produce hydrogen and its chemical kinetics study

A knife-type gliding arc discharge plasma reactor was developed for steam-methane reforming (SMR) H2 production. The kinetic model was established for industrial application. The effects of steam to carbon molar ratio, residence time and input power on SMR reactions were investigated. The experimental results indicated the S/C molar ratio of 2.01, the residence time of 13.8 s, and the input power of 36.0 W, the energy yield of hydrogen reached 173.6 L·(kW·h)−1, H2 and CO were also identified as the main gaseous products. Optical emission spectroscopy was used to diagnose chemically active species in plasma processes. The corresponding zero-dimensional chemical kinetic model was established, which includes 166 electron impact reactions and heavy particle reactions. The calculated results were in good agreement with the experimental results. The model results revealed the reaction CH4 + H → CH3 + H2 initiated by the H atom was the dominant reaction of CH4 conversion, and was also the main way of H2 generation.

A two step Microwave-assisted coke resistant mesoporous Ni-Co catalyst for methane steam reforming

Methane steam reforming (MSR) is an assuring reaction using steam to produce H2 as clean energy over a nicκel-based catalyst. We synthesized mesoporous monometallic NiMgAl2O4 and bimetallic NiCoMgAl2O4 catalysts in a two-step combustion method using a mix of fuels and powder metallurgy. BET-BJH, XRD, TGA, TPR, FESEM, and EDX-mapping characterized surface area, porosity, morphology, crystalline structure, and metal-support interaction behavior. The products exhibited strong interaction of well-structured MgAl2O4 spinel with NiO , in both specimens. The MSR evaluation tests at 750 °C under atmospheric pressure, CH4:H2O feed ratio of 1:1.2 showed the bimetallic catalyst has the highest conversion of 99.30% with low carbon deposition(0.09% weight loss), after 15 h. Both catalysts demonstrated a miniature nickel particle sintering. TG analysis revealed 0.0059 and 0.0035 mg lamentous carbon deposited on 3.4820 mg NiMgAl2O4 and 3.4820 mg NiCoMgAl2O4, respectively. Also, no XRD diffraction peaks related to the lamentous carbon were observed. Moreover the carbon balance showed the higher recovery of carbon (close to 1) for Co-promoted catalyst. Highly dispersed active Ni species might be responsible for high catalyst activity and resistant to coking in the MSR reaction.