Steam Reforming Research Articles

Variation of the shapes of catalytic blocks in the autothermal reforming of hexadecane, propane and methane using mathematical modeling

In this work, mathematical modeling of the autothermal reforming of hexadecane, propane and methane on catalytic blocks of different geometric shapes was carried out. It was shown that the convex shape of the block towards the oncoming reaction flow can increase the maximum temperature in the frontal zone, while the concave shape contributes to a more uniform temperature distribution along the entire length of the catalytic layer. The work also investigated the effect of the reaction flow rate on the change in the temperature gradient, which can subsequently be used to prevent the formation of hot spots and catalyst deactivation. The results obtained can serve as the basis for future research in the field of autothermal reforming and optimization of the geometric parameters of catalysts for the conversion of hydrocarbon fuels into synthesis gas.

Highly Efficient and Selective Light-Driven Dry Reforming of Methane by a Carbon Exchange Mechanism.

Dry reforming of methane (DRM) is a promising technique for converting greenhouse gases (namely, CH4 and CO2) into syngas. However, traditional thermocatalytic processes require high temperatures and suffer from low selectivity and coke-induced instability. Here, we report high-entropy alloys loaded on SrTiO3 as highly efficient and coke-resistant catalysts for light-driven DRM without a secondary source of heating. This process involves carbon exchange between reactants (i.e., CO2 and CH4) and oxygen exchange between CO2 and the lattice oxygen of supports, during which CO and H2 are gradually produced and released. Such a mechanism deeply suppresses the undesired side reactions such as reverse water-gas shift reaction and methane deep dissociation. Impressively, the optimized CoNiRuRhPd/SrTiO3 catalyst achieves ultrahigh activity (15.6/16.0 mol gmetal-1 h-1 for H2/CO production), long-term stability (∼150 h), and remarkable selectivity (∼0.96). This work opens a new avenue for future energy-efficient industrial applications.

An Economic Analysis of In-Situ Hydrogen Production from Natural Gas Wells with Subsurface Carbon Retention

Summary An economic analysis for a wellbore methodology that promotes sustainable natural gas conversion to hydrogen is presented. The methodology uses at-source, wellbore gasification of methane for hydrogen production, incorporating the simultaneous in-situ sequestration of carbon for both climate and economic benefit. The proposal is for a wellbore completion tool, to take natural gas (methane) production from the reservoir and perform gasification within the wellbore tool (not within the reservoir). This would not interfere with reservoir management, allowing standard reservoir management practices to be used. The proposed process is for natural gas fields and not for use in the gasification of heavy oils (which is covered by other “combustion type” reservoir management processes performed deep within the reservoir geology). The proposed methane gasification tool, when located deep within the wellbore, takes maximum advantage of the “free” energy provided by the elevated temperatures and pressures of the surrounding fluid-connected geology. The combination of surface-injected fluids and geofluids, mixed inside the wellbore gasification tool at depth, significantly reduces the excess process energy input from the surface and lessens feedstock consumption for power. The proposed system is neither electricity cost dependent nor fuel cost dependent, as both are provided in situ and through heat recovery and reserves. There are therefore several process steps and significant energy and cost savings to be gained by this method when compared with surface-based methane reformation facilities, as well as infrastructure longevity benefits. In addition, CO2 life cycle climate savings are made, as zero carbon is produced to the surface, eliminating the harm greenhouse gases (GHGs: CH4 and CO2) do while transitioning through the environment. The proposed methodology therefore avoids the expense and energy consumption of the subsequent, only partial, downstream recapture of the CO2 released from the combustion of this same methane. To help maintain consistency and ensure comparability for hydrogen production types, the standardized H2A template of the National Renewable Energy Laboratory (NREL) of the U.S. Department of Energy was used in our analysis. This economic template contains several cost model scenarios used to illustrate the possible magnitudes of economic advantages using this wellbore methodology. Based on the model’s comparative cost analyses, such a proposed system could produce hydrogen from natural gas wells consistently below 1 USD/kg H2, leading to cost-competitive wellbore hydrogen production when compared with surface-based steam methane reformation facilities. Using several scenarios for cost analysis, we found that the cost cannot be higher than 2 USD/kg H2. In our uncertainty quantification, we included the effects of the number of wells that can be used as well as mixing H2 with CH4 (v/v%).

Comparative analysis of methane conversion: pyrolysis, dry and steam thermal plasma reforming

Methane reforming is gaining attention because of its potential to be converted into energy-dense fuels or high-value chemicals. In addition to the production of syngas (H2+CO), the utilization of CO2 can help reduce greenhouse gases. Water steam is typically used to increase the output of H2. This study evaluated the potential of thermal plasma technology to produce clean hydrogen, carbon monoxide, and carbon black from methane by applying a thermodynamic equilibrium model. A comparative analysis of three cases of methane processing (pyrolysis, dry reforming, and steam reforming) is presented to provide a comprehensive understanding of the potential of thermal plasma technology for methane conversion.

Anti-coking Ni-La2O3/SiO2 catalyst prepared by using a glycine-assisted impregnation method for low-temperature dry reforming of methane

Abstract The development of efficient Ni-based catalysts for low-temperature (≤600 °C) dry reforming of methane remains a challenge because of their susceptibility to carbon deposition. Herein, we report a Ni-La2O3/SiO2 catalyst prepared by using the glycine-assisted impregnation method. Small Ni nanoparticles were confined by La2O3 on the SiO2 support in the catalyst, which exhibited remarkable resistance to carbon deposition for the dry reforming of methane at 600 °C.

Performance evaluation of carbon-negative syngas production via chemical looping reforming of methane from biomass pyrolysis volatiles

To realize the clean and efficient directional conversion of biomass, chemical looping reforming of biomass volatile CH4 based on a decoupling strategy is expected to carry out carbon-negative production of hydrogen-rich syngas. In this paper, a multi-functional oxygen carrier (NiFe2O4@SBA-16) for encapsulating the active metal oxide component NiFe2O4 with a three-dimensional interconnecting pore molecular sieve SBA-16 was designed. The experimental results showed that the modification strategy of composite metal oxide encapsulation improved syngas selectivity and CH4 conversion based on the fixed-bed reactor. 20 %NiFe2O4@SBA-16 showed 22.1 % CH4 conversion and 92.6 % CO selectivity under 750 °C, and it maintained good cycle stability after 15 cycles. The H2/CO ratio was effectively improved by adding part of CO2 into the feed gas, and the CH4 conversion reached over 35 %. This study provides essential data for the clean preparation of hydrogen-rich syngas from biomass and the development and design of multifunctional oxygen carriers.

Methane-H2S Reforming Catalyzed by Carbon and Metal Sulfide Stabilized Sulfur Dimers.

H2S reforming of methane (HRM) provides a potential strategy to directly utilize sour natural gas for the production of COx-free H2 and sulfur chemicals. Several carbon allotropes were found to be active and selective for HRM, while the additional presence of transition metals led to further rate enhancements and outstanding stability (e.g., Ru supported on carbon black). Most metals are transformed to sulfides, but the carbon supports prevent sintering under the harsh reaction conditions. Supported by theoretical calculations, kinetic and isotopic investigations with representative catalysts showed that H2S decomposition and the recombination of surface H atoms are quasi-equilibrated, while the first C-H bond scission is the kinetically relevant step. Theory and experiments jointly establish that dynamically formed surface sulfur dimers are responsible for methane activation and catalytic turnovers on sulfide and carbon surfaces that are otherwise inert without reaction-derived active sites.

Structured nanoporous Cu/ZnO catalysts for on-board methanol steam reforming prepared by laser powder bed fusion and dealloying

The development of efficient structural catalysts and reactors (SCRs) for on-board methanol steam reforming (MSR) has long been a focal point. Traditional MSR SCRs exhibit problems such as poor heat transfer, low catalyst loading, and coating delamination. In this study, novel three-dimensional graded nanoporous Cu/ZnO (3DNP-Cu/ZnO) SCRs were prepared via metal 3D printing technology and dealloying. For 3DNP-Cu/ZnO SCRs activated with MeOH/H2O steam, both the interfacial area of Cu-ZnO and the Cu+/(Cu0 + Cu+) molar ratio were greater than those of catalysts activated with H2/N2 mixtures. The experimental results showed that a 3DNP-Cu/ZnO SCR activated with MeOH/H2O for 20 min exhibited a high methanol conversion rate of 98.3 % with a CO selectivity of 0.86 % (with a reaction temperature of 280 °C, a water-to-alcohol molar ratio of 1.3 and a weight hourly space velocity of 30 h−1). The superior catalytic activity was attributed to the high Cu+/(Cu++Cu0) ratio, which enabled the generation of *CHOO during the MSR reaction. Additionally, the 3DNP-Cu/ZnO SCRs demonstrated low pressure drops and high mechanical strengths. Computational fluid dynamics simulations showed that the gyroid lattice-structured catalyst achieved a high H2 concentration due to its high mass and heat transfer. 3DNP-Cu/ZnO SCRs provide a new strategy for the preparation of MSR SCRs with broad application prospects.

Study on tritium permeation behavior in primary and second circuits of the hydrogen production system by methane steam reforming using HTGR

Hydrogen production by methane steam reforming (MSR) using the process heat from High-temperature gas-cooled reactor (HTGR) is one of the most promising technology for hydrogen production using nuclear energy in the near future. The permeation behavior of tritium produced by the reactor is extremely important when analyzing the safety of this hydrogen production system. There are two methods of connection between a nuclear reactor and a hydrogen production system. One is direct coupling that the steam reformer of the hydrogen production system is directly connected to the first circuit of the nuclear reactor. The other is indirect coupling via an intermediate heat exchanger (IHX) to connect nuclear reactor and hydrogen production system. Hence, this work proposed a model to analyze the difference in tritium permeation between these two coupling ways and to compare the tritium permeation behavior for different IHX alloys at various operating conditions. This model includes tritium's production rate, release fraction, and decay reduction in the system. The results show that the pre-exponential factor of the IHX alloy mainly limits the tritium permeation rate. In addition, the tritium permeation rate increases about two times when the temperature rises from 750 °C to 950 °C at a steady state. Further, the decrease of tritium permeation rate is seen from the calculation results for the system with IHX, e.g., for T = 750 °C, the mean permeation rate of tritium into the product gas is 9.31 × 10−12 mol/s at the whole year for indirect coupling with an IHX, compared to 3.86 × 10−12 mol/s for direct coupling, which reduced 58.54 % (This means that with IHX the permeation rate is lower than the system without IHX). These results will contribute to designing an effective and safe hydrogen production system by MSR using HTGR process heat.

Kinetic Analysis of Catalytic Dry Reforming of Methane Using Ni-ZrO2/MCM-41 Catalyst

This work investigates the kinetics of catalytic dry reforming of methane (CDRM) to produce hydrogen gas using nickel-based catalysts. A new catalyst was prepared, Ni-ZrO2@MCM-41 (MCMZ) and used in the CDRM reaction. The textural, physical, and morphological scans are used to characterize the prepared catalyst. The performance of the newly prepared catalyst in terms of temperature effects and long-term stability is assessed. The reaction activation energy is studied as well. The outcomes of this study revealed that the MCMZ provided the highest conversion values for CH4 and CO2, with 89 and 91%, respectively. The optimum reaction temperature to achieve the highest syngas conversion was 800 °C. In addition, two new models that present CH4 and CO2 conversions for MCMZ as a function of reaction time to predict the rate of catalyst activity were built with very high accuracy. It was found that the activation energy was within the expected limits. Finally, the constants and reaction rate were determined. To conclude, this research creates a new catalyst with high performance to enhance hydrogen gas production from methane with carbon dioxide that contributes significantly to the field of yielding alternative energy sources.

MOFs-derived Ni@ZrO2 catalyst for dry reforming of methane: Tunable metal-support interaction

Metal-support interaction (MSI) plays an important role in heterogeneous catalysis, that could be well regulated by many strategies. Here, Ni@ZrO2 catalysts were controllably synthesized by sacrificial Zr-MOFs template strategy, and were applied to the dry reforming of methane (DRM). Amongst, the Ni/ZrO2-B catalyst shows the best performance toward CH4 and CO2 conversion, H2/CO ratio, and stability, following by Ni/ZrO2-A and Ni/ZrO2C catalysts. The difference in catalytic performance should be ascribed to different synthetic strategy, resulting in different properties of Ni species and ZrO2 matrix, and interface interaction. It revealed that small Ni particles were benefit for CH4 activation, and strong MSI boosted CO2 activation, that could remain the Ni dispersion and thermal stability. This study is beneficial to the catalyst design in DRM reaction.

Hydrolysis Precipitation Method for the Preparation of Cu‐ZnO@Al2O3 Catalyst in Methanol Steam Reforming

AbstractA hydrolysis precipitation method was developed to prepare Cu based catalyst for methanol steam reforming. A comparison of the hydrolysis precipitation and the conventional coprecipitation method was conducted. The test results present that Cu‐ZnO@Al2O3 prepared by hydrolysis precipitation exhibits better catalytic activity and stability in MSR reaction. XRD, XRF, EDS, SEM, TPR, XPS and N2 adsorption/desorption reveal that the high catalytic performance of Cu based catalyst from hydrolysis precipitation could be attributed to developed pore organization, surface enrichment of active components and higher reducibility.

Multi-objective optimization of steam methane reformer in micro chemically recuperated gas turbine

A kinetic theory, known as the Langmuir–Hinshelwood–Hougen–Watson adsorption model, is applied to describe the steam methane reforming (SMR) in a 500 kW scale micro chemically recuperated gas turbine (CRGT) cycle. The response surface models of important performance parameters, including the methane conversion, carbon monoxide selectivity, and chemically recuperated heat as a function of the temperature, pressure, steam-to-carbon ratio, and contact time are numerically obtained based on the cases selected by the central composite design. The factors affecting the SMR performance are analyzed, and the reformer performance is optimized using both the desirability function combined with the response surface methodology and the second generation non-dominated sorting genetic algorithm. Finally, performance of the optimized reformer and electrical efficiency of the micro CRGT cycle with the reformer are evaluated. Results reveal that the efficiency of the micro CRGT is 40.70%, which is much higher than the typical high-efficiency micro gas trubine without reformer.

CO2-to-methanol: Economic and environmental comparison of emerging and established technologies with dry reforming and methane pyrolysis

This work compares 9 process routes that produce methanol from carbon dioxide using new and established thermochemical and electrochemical technologies. Net CO2 conversion is compared, and process efficiencies are benchmarked using side-by-side process models. New process routes using recently reported catalysts that enable methane pyrolysis (PY), and the dry reforming of methane (DMR) are modeled. Comparison is made with direct CO2 hydrogenation to methanol, the co-electrolysis of water and CO2 using solid oxide electrochemistry, and combinations of process technologies. Both electric heating and fuel switching to hydrogen are considered. Autothermal reforming of methane (ATR) is modeled as the conventional technology for reference. A new thermochemical approach in which CO2 reforming and methane pyrolysis reactions occur in separate reactors, with excess hydrogen produced and combusted for heat, (PY/DMR) was found to have the lowest levelized costs of CO2 mitigation varying from $50.4–53.9/t-CO2 using different electricity carbon intensities and levelized cost of methanol of $295.6/t. Methane pyrolysis offers the most flexible process solutions: it is nearly cost-competitive with reforming today ($295.6/t vs $277.3/t) using fuel switching and would emerge as the most economically viable process ($99.5/t) in future scenarios with very low electricity and natural gas costs and very high emissions penalties starting from 2030. Based on the emission factors from both electricity and natural gas across 195 countries around the world, 53 countries would result in net conversion of CO2 via pyrolysis today after heating, fugitive emissions, and energy use are taken into account.

NiGa nano-alloy for the dry reforming of methane: Influences of Ga alloying with Ni on the catalytic activity and stability

The massive emission of CO2 and CH4 has caused serious environmental and ecological problems, and dry reforming of methane reaction has received widespread attentions due to the fact that it can eliminate the two gas simultaneously. Herein, Ni60Ga40/Al2O3 (molar ratio of Ni:Ga was 60:40) catalyst was synthesized by mechanochemical synthesis method, offering 75 % CH4 conversion, 85 % CO2 conversion, and H2/CO ratio of 0.93 at 750 °C during 120 h test. Ni in Ni60Ga40/Al2O3 combines with Ga to form Ni3Ga intermetallic compound, which inhibits the sintering of Ni and rapid cracking of CH4. Moreover, the extra Ga species, existing in the form of Ga2O3-Al2O3 with abundant oxygen vacancy, boosts CO2 activation and prevents carbon development on catalyst surface. In contrast, for the pure Ni/Al2O3 and Ga/Al2O3 catalysts, the stability and catalytic activity couldn’t be obtained synchronously. This work particularly investigated the CH4 dissociation and CO2 activation for the NiGa/Al2O3 catalysts, establishing the foundation for rational design of low-cost performance catalysts for the dry reforming of methane reactions.

Quench-induced Cu-ZnO catalyst for hydrogen production from methanol steam reforming

Methanol steam reforming (MSR) is considered as a promising approach to provide hydrogen for proton-exchange membrane fuel cells. However, it is challenging to develop effective and durable Cu-based catalysts. Herein, Cu-ZnO catalysts are prepared by facile quenching of ZnO in copper nitrate solution followed by reduction to obtain the desired metal loading and induce the doping of surface metal heteroatoms for producing more vacancies. Catalysts enriched with oxygen vacancies can efficiently activate H2O and rapidly transform C-containing intermediates, resulting in higher methanol conversion and lower CO selectivity. As a result, the quenched optimal catalyst achieves 100 % methanol conversion and 0.05 % CO selectivity at 280 ℃, exhibiting the excellent catalytic performance in MSR reaction. In practical applications, structured catalysts are more attractive for large-scale catalytic reactions owing to the low pressure drop and high utilization efficiency. Therefore, ZnO-Cu3 catalyst is coated on cordierite honeycomb ceramics with 100 % methanol conversion and 0.04 % CO selectivity at 280 ℃. After 100 h of the reaction, the structured catalyst remains ∼ 92.3 % with CO selectivity varying from 0.02 to 0.06 %, demonstrating the good catalytic stability in the long-term experiment. In addition, the evolution of reactants and intermediates on the catalyst surface are briefly described by FTIR spectra. This study offers a novel and efficient approach to obtain highly active and durable catalysts with great potential for industrial-scale preparation and application.

Highly stable CuFe1.2Al.8O4 catalyst with low CO selectivity for hydrogen production in HT‐PEMFCs application

AbstractMethanol steam reforming (MSR) is considered as an effective way to provide on‐board hydrogen production technology for fuel cell applications. CuFe1.2Al.8O4 spinel catalyst was synthesized by sol–gel method and the chemical and physical properties were studied in‐depth. X‐ray diffraction, hydrogen‐temperature programmed reduction (H2‐TPR), BET, and scanning electron microscopy were used to characterize the catalysts with reaction times of 20, 50, and 100 h. The results of H2‐TPR showed that 90% of spinel Cu2+ was released after 100 h reaction. BET results show that the specific surface area and pore characteristics of the catalyst have not changed greatly after reaction for 20, 50, and 100 h. Furthermore, in the unsteady‐state test, CuFe1.2Al.8O4 exhibited excellent catalytic activity and thermal stability under long‐term repeated start‐up and stop cycles. At 275°C, the methanol conversion rate remained around 94% and the CO selectivity remained below 1%. Therefore, the catalyst synthesized in this study has excellent stability and low CO selectivity, making it a highly promising on‐board hydrogen production catalyst in the field of HT‐proton exchange membrane fuel cells (PEMFCs).

Design of a novel tubular membrane reactor with a middle annular injector for enhancement of dry reforming towards high hydrogen purity: CFD analysis

This study introduces a novel design of a tubular porous membrane catalytic reactor (TPMCR) with a middle annular injector, which aims to improve the performance of a dry reforming of methane (DRM) process. A computational fluid dynamics (CFD) model is developed for a fundamental configuration and subsequently verified using experimental data. The validated CFD model is utilized to examine the influence of different parameters, such as feed composition, inlet gas temperature and pressure, and injection rate, on the reactor performance. The study findings reveal that the introduction of a secondary gas during the injection process has the potential to regulate the process and positively affect the production rates of hydrogen and carbon monoxide. The optimal inlet temperature to attain the highest rate of hydrogen production is determined to be 900 K. The hydrogen selectivity is found to increase from 0.96 to 1.60 with the injection of pure steam when the injection rate is increased from 50 to 500 kg/(m2.s). In addition, the carbon monoxide selectivity is decreased from 6.30 to 2.67. The implementation of a middle annular injector within the proposed TPMCR design offers the potential for enhancing the efficiency and sustainability of chemical reactors. Consequently, the introduced modification leads to more efficient and environmentally friendly chemical processes, specifically in the realms of syngas and hydrogen production through the DRM process, resulting in improved purity levels.

Perovskite-Derivative Ni-Based Catalysts for Hydrogen Production via Steam Reforming of Long-Chain Hydrocarbon Fuel

Large-scale hydrogen production by the steam reforming of long-chain hydrocarbon fuel is highly desirable for fuel-cell application. In this work, LaNiO3 perovskite materials doped with different rare earth elements (Ce, Pr, Tb and Sm) were prepared by a sol-gel method, and the derivatives supported Ni-based catalysts which were successfully synthesized by hydrogen reduction. The physicochemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, N2 adsorption–desorption isotherms, H2 temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic performance of the as-prepared catalysts for hydrogen production was investigated via the steam reforming of n-dodecane. The results showed that the catalyst forms perovskite oxides after calcination with abundant mesopores and macropores. After reduction, Ni particles were uniformly distributed on perovskite derivatives, and can effectively reduce the particles’ sizes by doping with rare earth elements (Ce, Pr, Tb and Sm). Compared with the un-doped catalyst, the activity and hydrogen-production rate of the catalysts are greatly improved with rare earth element (Ce, Pr, Tb and Sm)-doped catalysts, as well as the anti-carbon deposition performance. This is due to the strong interaction between the uniformly distributed Ni particles and the support, as well as the abundant oxygen defects on the catalyst surface.

Unlocking exceptional diffusion of porous Ni@SiO2 nanocapsule catalysts for enhanced dry reforming of methane

This paper introduces innovative porous Ni@SiO2 nanocapsule catalysts for high-temperature dry reforming of methane, synthesized through a selective etching method in a mild alkaline solution with varying CTAB concentrations. While core-shell catalysts have been proven effective in addressing issues like active metal sintering and coking, their dense inert oxide shells can impede intrinsic kinetics and hinder gas diffusion. The optimized catalyst, M-NSNC-2, showcases exceptional performance, featuring small Ni nanoparticles (5.3 nm) within a porous SiO2 nanocapsule (>900 m2g−1). M-NSNC-2 demonstrates outstanding methane conversion (>82%), stability (50 hours), and resistance to sintering, agglomeration, and higher-ordered carbon deposition. In comparison to dense Ni@SiO2 nanocapsules (NSNC), M-NSNC-2 exhibits superior performance with nearly 13-fold enhanced mass transfer diffusivity. Additionally, the porous Ni@SiO2 nanocapsule catalyst exhibits an apparent CH4 activation energy of 67.9 kJ/mol at a kinetic regime of 1800,000 mL gcat−1h−1, emphasizing its efficacy in catalyzing dry reforming of methane.