Increase In Methane Conversion Research Articles

Conversion of dry biogas in a chemical looping reforming unit: Performance of Fe and FeMn-based oxygen carriers

Biogas conversion is a renewable alternative for producing hydrogen. In this work, dry reforming of simulated biogas was performed in a 1 kWth continuous chemical looping reforming (CLR) unit in which the oxygen required for the partial oxidation of biogas to CO and H2 is supplied by an oxygen carrier. The performance of two different oxygen carriers (an iron oxide-based residue and a synthetic material based on an iron-manganese mixed oxide) was evaluated. The residue was capable of performing the dry reforming of biogas to a larger extent than the synthetic oxygen carrier. To enhance hydrogen yield, NiO addition was also considered with both materials. The presence of NiO increased methane conversion and H2 selectivity for both oxygen carriers. A value of approximately 2.6 mol H2/mol CH4 was achieved with both materials with the presence of only 2.7 wt% NiO in the bed.

Ni-based bimetallic catalysts for hydrogen production via (sorption-enhanced) steam methane reforming

The catalytic performance of a monometallic Ni/Al2O3 and three bimetallic catalysts (Ni3M1/Al2O3, with M = Cu, Fe, and Ge) for the (sorption-enhanced) steam methane reforming reaction was evaluated. Ni3Cu1/Al2O3 was found to be the optimal catalyst in terms of methane conversion, hydrogen yield, and purity. Ge also has a promoting effect on the monometallic Ni catalyst, whereas the addition of Fe negatively influenced its performance. Physico-chemical characterization of the materials indicated the formation of alloys upon activation of the materials with hydrogen. The addition of Cu increased the surface area and metal dispersion, and improved the overall morphology of the catalyst. The experimental observations were also supported by a numerical study combining Density Functional Theory-based calculations and Microkinetic modelling of the SMR process. Ni3Cu1 and Ni3Ge1 were calculated to have a similar level of catalytic activity as Ni, whereas Ni3Fe1 was unsuitable for the reaction. The SMR reaction was further improved by adding calcium oxide as the CO2 sorbent, which increased methane conversion, CO selectivity, hydrogen yield, and hydrogen purity. The highest methane conversion of 97 % was achieved by Ni/Al2O3 and Ni3Cu1/Al2O3 at 700 °C.

Numerical Evaluation of Heat Transfer and Conversion Efficiency by Tube Design and Flow Configuration for a Compact Steam-Methane Reformer

In the chemical industry, hydrogen (H2) production through steam-methane reforming is a well-established process. With the growing demand for H-fueled vehicles and charging stations, there is a need for compact reformers with efficient heat transfer capabilities. In this study, computational fluid dynamics simulations were performed to evaluate the methane (CH4) conversion and heat transfer efficiency of various reformer designs. These designs include single, double, and triple tubes, each with parallel- and counter-flow configurations between the reformate feed and heat source. The findings revealed substantial disparities in methane conversion between the tube designs and flow configurations. Notably, the triple-tube design outperforms single and double tubes, exhibiting higher methane conversion and improved heat transfer efficiency. This superior performance is attributed to the larger wall area facing the heat source and additional heat recovery from the reformate flowing in the inner annulus. This led to the highest temperature at the catalyst exit among the cases, increasing methane conversion, and the lowest reformate temperature at the reformer tube exit, which is also beneficial for the subsequent water–gas shift reaction process. Installing external fins on the reformer tube provided a more effective enhancement of heat transfer than using internal fins in the catalyst section. Regardless of the tube design employed, the counter-flow configuration consistently enhanced the heat transfer efficiency, resulting in 4.6–11.9% higher methane conversion than the parallel-flow configuration. Consequently, the triple-tube design with the counter-flow configuration achieved the highest methane conversion, offering flexibility in the reformer design, including the potential for lower heat input and a reduced catalyst volume.

Numerical study on the interaction between rotating detonation wave and turbine stator blades with multicomponent mixtures

Aiming at the coupling problem between rotating detonation combustor and turbine components, this paper uses methane recuperation gas as fuel and adopts two-dimensional numerical simulation to study the working process after coupling between rotating detonation combustor and turbine stator blades. The results show that with the increase of methane conversion, the propagation mode changes from single wave mode to unstable single wave mode. Under the two modes, after the oblique shock wave sweep, the turbine stator blade outlet Mach number suddenly rises to 2.5. In addition, the flow field structure of a single turbine blade is also analyzed, and it is found that after oblique shock wave sweep, the flow field structure changes, and boundary layer separation occurs at the trailing edge of turbine stator blades. Turbine stator blades have a certain inhibition effect on the pressure oscillation at the combustion chamber outlet, and the disturbance generated by detonation wave extinguishing in unstable single-wave mode will be transmitted through turbine stator blades to the outlet. With the increase of fuel activity, turbine stator blade pressure loss gradually increases. The total pressure loss coefficient of single-wave mode is 9%, and the total pressure loss coefficient of unstable single-wave mode is 4%–6% higher than that of single-wave mode.

Methane Pyrolysis in a Liquid Metal Bubble Column Reactor for CO2-Free Production of Hydrogen

In light of the growing interest in hydrogen as an energy carrier and reducing agent, various industries, including the iron and steel sector, are considering the increased adoption of hydrogen. To meet the rising demand in energy-intensive industries, the production of hydrogen must be significantly expanded and further developed. However, current hydrogen production heavily relies on fossil-fuel-based methods, resulting in a considerable environmental burden, with approximately 10 tons of CO2 emissions per ton of hydrogen. To address this challenge, methane pyrolysis offers a promising approach for producing clean hydrogen with reduced CO2 emissions. This process involves converting methane (CH4) into hydrogen and solid carbon, significantly lowering the carbon footprint. This work aims to enhance and broaden the understanding of methane pyrolysis in a liquid metal bubble column reactor (LMBCR) by utilizing an expanded and improved experimental setup based on the reactor concept previously proposed by authors from Montanuniversitaet in 2022 and 2023. The focus is on investigating the process parameters’ temperature and methane input rate with regard to their impact on methane conversion. The liquid metal temperature exhibits a strong influence, increasing methane conversion from 35% at 1150 °C to 74% at 1250 °C. In contrast, the effect of the methane flow rate remains relatively small in the investigated range. Moreover, an investigation is conducted to assess the impact of carbon layers covering the surface of the liquid metal column. Additionally, a comparative analysis between the LMBCR and a blank tube reactor (BTR) is presented.

Process configurations to lower the temperature of methane pyrolysis in a molten metal bath for hydrogen production

Novel configurations of a process for methane pyrolysis using a molten catalyst bubble column reactor are proposed in this study. These configurations aim to achieve reasonable conversion at temperatures below 1000 °C by recycling a fraction of the hot reactor product gas. Three recycling configurations are assessed: the first utilizes an ejector, the second employs a compressor, and the third combines a compressor with a turbo-expander. The performance of these configurations was evaluated using ASPEN HYSYS to compare them against a reference cycle without recycling. The evaluation criteria included methane conversion and the thermal heat requirement of the reactor. The results indicate that recycling can significantly increase methane conversion, with a maximum improvement of 165%. Specifically, when recycling 80% of the hot products in the first pass conversion using the third configuration, methane conversion increased from 17.8% to 47.2%. The other two configurations achieved conversions of 28%, representing a 57% increase from the baseline of 17.8% under the same conditions. Furthermore, it is possible to achieve a configuration with zero net CO2 emissions by employing renewable power and utilising some of the hydrogen product for combustion to meet the process heat demand.

Effect of temperature and heat flux boundary conditions on hydrogen production in membrane-integrated steam-methane reformer

In order to operate reforming plants at maximum efficiency it is important to investigate their operation under various conditions. This study aims to perform a comprehensive computational analysis to examine the effect of thermal boundary conditions on SMR and hydrogen recovery and, consequently, enriching the literature on hydrogen generation through steam-methane reforming. The studied thermal boundary conditions include constant and variable inlet temperature, outer wall temperature, and heat flux on outer wall of the reactor. A constant inlet flow rate of 0.001 kg/s (methane mass flow rate = 0.00018 kg/s), steam-to-methane ratio (or steam-to-carbon ratio, i.e., S/C) of 4 is considered in the reformer side for all the cases. Furthermore, the difference of pressure between both faces of the membrane is kept constant. Sweeping flow is incorporated to further raise the hydrogen partial pressure difference. Steam with flow rate of 0.001 kg/s is used to induce the sweeping effect throughout the study. Constant and variable temperatures/heat fluxes along with the effect of radiation in the reformer and transient inlet temperatures are examined in this study in terms of CH4 conversion ( %), H2 recovery ( %), H2 mass flow rates (kg/s), hydrogen mass flux through the membrane (kg.m−2. s−1), and other important parameters. About 1.7 times increase in methane conversion is noted as the reformer temperature is increased from 500 to 700 °C. The hydrogen recovery is found to decrease with the increase in temperature. Around 57 % and 56 % decrease in methane conversion and 42 % and 11.5 % rise in hydrogen recovery is observed with segmented case as compared to the constant heat flux and constant temperature cases, respectively. As compared to the reference 600 °C constant wall temperature, the increasing temperature profile results in 10.6 % rise in methane reforming and 11.2 % drop in the recovery of hydrogen. On the other hand, the decreasing temperature profile demonstrates 9.4 % decrease in conversion and 10.2 % elevation in recovery rate in contrast with the constant temperature case.

Natural Gas Pyrolysis in a Liquid Metal Bubble Column Reaction System—Part II: Pyrolysis Experiments and Discussion

This contribution presents the results of continued investigations on the production of hydrogen by means of pyrolysis in a liquid metal bubble column reactor, as developed at the Karlsruhe Institute of Technology in recent years. Part I of this contribution described the motivation and the methodology of this study, as well as a significant scale-up, and discussed its results for pure methane pyrolysis. Here in part II, two additional experimental campaigns with methane–ethane mixtures (MEMs) and high-calorific natural gas (nGH) will be presented and discussed for the first time, using the up-scaled liquid metal bubble column reactor. It could be proven that an MEM as the feed gas led to an increase in methane conversion at low temperatures, which is consistent with the literature data. The nGH pyrolysis confirms this trend and also results in a significant rise in methane conversion compared to pure methane pyrolysis. Furthermore, the nGH pyrolysis leads to an increased methane conversion even at higher temperatures compared to MEM pyrolysis. Additionally, both MEM and nGH pyrolysis also showed a shift in the formation of by-products toward lower temperatures.

Effect of the Catalyst Shapes and the Packed Bed Structure on the Efficiency of Steam Methane Reforming

One of the promising technologies for on-board hydrogen production is methane steam reforming in reactor with packed bed. The study of the effect of various catalytic packing arrangements on the steam methane reforming process is of considerable interest. The present article analyses the influence of catalyst shapes and packing arrangement on steam methane reforming reactions efficiency. The reformer tube contains several packings with a changing relative position; additionally, two forms of catalysts, a ball and a cylinder, are also used. The pressure drop depending on the packing location, methane conversion and hydrogen yield were analysed. It was found that the packing arrangement with spacing allows better distribution of the supplied heat. Due to the distance between the packing sections flow becomes more turbulent after each section, which intensifies the heat transfer and mixing of the mixture. The highest hydrogen yield is observed on catalytic packings located at a distance of 40 mm from each other and consisting of cylindrical catalysts. The most uniform pressure drop occurs at a packing arrangement without spacing. The increase in methane conversion observed with the increment in spacing distance, but the difference is insignificant. Therefore, the arrangement of catalysts with spacing can be used for the improvement of steam methane reforming process.

An iron ore-based catalyst for producing hydrogen and metallurgical carbon via catalytic methane pyrolysis for decarbonisation of the steel industry

Experiments to investigate the catalytic pyrolysis of methane using an iron ore-based catalyst were carried out to optimize catalytic activity and examine the purity of the carbon produced from the process for the first time. Ball milling of the iron ore at 300 rpm for varying times – from 30 to 330 min – was studied to determine the effect of milling time on methane conversion. Optimal milling for 270 min led to a five-fold increase in methane conversion from ca. 1%–5%. Further grinding resulted in a decline of methane conversion to 4% shown by SEM to correspond to an increase in particle size caused by agglomeration. Data from Raman and Mössbauer spectroscopy and H2 temperature programmed reduction indicated a change in phase from magnetite to maghemite and hematite (at the particle surface) as the grinding time increased. Analysis of the carbon produced as a byproduct of the reaction indicated a highly pure material with the potential to be used as an additive for steel production.

Theoretical analysis of a solar membrane reactor with enhanced mass transfer by using helical inserts

Product separation Pd-based membrane can boost performance of conventional solar-driven thermochemical reactors by accelerating reaction processes. However, concentration polarization due to mass transfer resistance limits the conversion and efficiency of solar membrane reactor. In this work, the helical insert-enhanced solar membrane reactor is proposed to eliminate adverse impact of concentration polarization. The influence mechanism of radial mass transfer enhancement on reactor performance is analyzed. The number of helical inserts is optimized and the performance enhancement of proposed reactor under different operating conditions is explored. It is shown that enhancing radial mass transfer effectively alleviates concentration polarization and overall methane conversion can be maximally improved by about 29 %. By applying multi-helical inserts, the radial mass transfer in reaction bed is greatly enhanced, which achieves homogenous radial component distribution, improves the hydrogen separation performance and expands high-quality reaction zone. In comparison to the original membrane reactor, the optimized reactor with 5-helical inserts can increase methane conversion, fuel efficiency, and hydrogen recovery by 16.4 %, 18.7 %, and 21.4 %, respectively, in the operating temperature range of 673–823 K. Also, it is presented that the proposed helical insert-enhanced solar membrane reactor can deliver significant performance improvement under different operating conditions.

Metal impregnation on steel converter slag as an oxygen carrier

AbstractOxygen carriers used in chemical looping processes operated with biofuel are affected by the inorganic matter of the fuel. It is therefore expected that the lifetime of the oxygen carrier is limited, and preferably low‐cost oxygen carriers should be used. Oxygen carriers based on iron ore or steel manufacturing waste products are available in significant quantities at low cost. However, it is common for these types of materials that their reactivity is low. This study investigates the effect of adding small amounts of more reactive elements into steel converter slag, also called LD slag.Slag particles were wet impregnated with 2 or 5 wt.% of Ni, Cu, Mn, or Ce. The new material's morphology was evaluated using X‐Ray Diffraction and SEM‐EDS. Changes in reactivity towards CO, CH4 and the model tar molecule benzene were evaluated using a bench‐scale laboratory fluidized bed reactor.It was observed that even small amounts of either Ni, Cu, or Mn could increase reactivity toward CO. Both Cu and Mn formed phases with LD slag that released oxygen via CLOU (chemical looping with oxygen uncoupling) and increased the conversion of methane and benzene. Ni and Ce doping also increased methane conversion but had only a minor effect on the benzene conversion. © 2023 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

H2 Production by Methane Oxy-Reforming: Effect of Catalyst Pretreatment on the Properties and Activity of Rh-Ce0.5Zr0.5O2 Synthetized by Microemulsion

Green hydrogen introduction in hard-to-abate processes is held back by the cost of substituting steam reforming plants with electrolyzers. However, green hydrogen can be integrated in properly modified reforming processes. The process proposed here involves the substitution of steam reforming with oxy-reforming, which is the coupling of the former with catalytic partial oxidation (CPO), exploiting the pure oxygen coproduced during electrolysis to feed CPO, which allows for better heat exchange thanks to its exothermic nature. With the aim of developing tailored catalysts for the oxy-reforming process, Ce0.5Zr0.5O2 was synthetized by microemulsion and impregnated with Rh. The Ce-based supports were calcined at different temperatures (750 and 900 °C) and the catalysts were reduced at 750 °C or 500 °C. Tuning the calcination temperature allowed for an increase in the support surface area, resulting in well-dispersed Rh species that provided a high reducibility for both the metal active phase and the Ce-based support. This allowed for an increase in methane conversion under different conditions of contact time and pressure and the outperformance of the other catalysts. The higher activity was related to well-dispersed Rh species interacting with the support that provided a high concentration of surface OH* on the Ce-based support and increased methane dissociation. This anticipated the occurrence and the extent of steam reforming over the catalytic bed, producing a smoother thermal profile.

Effect of the interaction of components in a nickel-molybdenum catalyst on its activity in decomposition of methane to hydrogen

This work is devoted to the study of the activity of monometallic (Fe/Al2O3) and bimetallic (Fe-Mo/Al2O3) catalysts supported to carrier γ- Al2O3. It has been discovered that the bimetallic catalyst is more active than the monometallic catalyst in the methane decomposition reaction. The results of the influence of molybdenum oxide on the activity of Fe/Al2O3 catalyst in the methane decomposition reaction in the temperature range 500-850°C have been obtained. It has been determined that the addition of molybdenum oxide in the amount of 5 wt. % of the iron catalyst composition leads to an increase in the catalytic activity of the sample in the reaction of methanedecomposition to hydrogen at relatively low temperatures. Compared to Fe/Al2O3 on the FeMo/Al2O3 catalyst at a reaction temperature of 750°C, methane conversionincreases from 8% to 98%, hydrogen yield from 5% to 57%. The increased field of activity Fe-Mo/Al2O3catalyst in the decomposition of methane to hydrogen compared to Fe/Al2O3 catalysts is due to an increase in the dispersity of the active phases of the catalyst, as well as the formation of an easily reduced Fe2(MоО4)3 phase, according to XRD, TPR-H2, and BET methods.

Photocatalytic Methane Conversion: Insight into the Mechanism of C(sp 3 )–H Bond Activation

Photocatalytic Methane Conversion: Insight into the Mechanism of C(sp ³ )–H Bond Activation

The Efficiency of Pd Addition and Sr Substitution on La1−xSrxMnO3 to Remove Ventilation Air Methane in a Catalytic Flow Reversal Reactor

Ventilation air methane (VAM) is the main cause of greenhouse gas emissions in coal mining. Catalytic flow reverse reactor (CFRR) is widely used in VAM to mitigate methane emissions. In this study, palladium (Pd) and La1−xSrxMnO3 were used as catalysts in a CFRR. Different types of catalysts were prepared by loading La0.8Sr0.2MnO3, La0.9Sr0.1MnO3, and 0.1%Pd-La0.9Sr0.1MnO3 on a cordierite honeycomb reactor coated with γ-Al2O3 to compare their performances. In addition, this study compared the performance of the three catalysts in an 800 °C reactor based on different methane inlet concentrations, inlet speeds, and conversion times. The results showed: (1) 0.1% addition of Pd increased methane conversion. (2) La0.8Sr0.2MnO3 had higher efficiency at lower methane inlet concentrations, whereas La0.9Sr0.1MnO3 was more efficient at higher methane concentrations. This study demonstrates that a higher Sr loading is worth implementing only when the methane concentration of VAM is lower than 0.6%. (3) To achieve a higher methane conversion efficiency, the inlet velocity of methane should also be considered.

Autothermal reforming of methane over an integrated solid oxide fuel cell reactor for power and syngas co-generation

Autothermal reforming of methane couples exothermal partial oxidation of methane and endothermal steam or dry reforming of methane to achieve high energy efficiency, which can be operated through solid oxide fuel cells (SOFCs) so that expensive oxygen is not required and safety issue caused by CH4/O2 mixture is avoided. In addition, electric power is simultaneously generated. This study has demonstrated the efficient electrochemical autothermal reforming of methane over a SOFC reactor integrated with catalyst beds within anode channel structure. The catalyst bed reformer increases syngas yield by a factor of about 6 owing to the increased methane conversion and syngas selectivity. By numerical assessment, enhanced mass transportation is well validated by high fuel accessibility at the electrode-electrolyte interface benefiting from the integrated catalyst beds. Compared with conventional catalyst layer on anode surface, the catalyst beds are more efficient for conducting methane reforming. After the initial stabilization of cell microstructure, the SOFC reactor has demonstrated stable cell performance and syngas yield during the test for 120 h. The integrated SOFC reactor has demonstrated a promising application in performing catalytic reforming reactions.

Comprehensive parametric investigation of methane reforming and hydrogen separation using a CFD model

Steam-methane reforming is the primary method for industrial hydrogen production. High energy consumption and elevated greenhouse gas (GHG) emissions call for a significant improvement in the reforming process for optimum methane conversion and hydrogen production. Enhanced fuel conversion also produces more CO2 than CO, making the carbon capture process easier, consequently reducing harmful emissions. In this work, a membrane-integrated reformer reactor (MRR) has been investigated through an experimentally validated computational fluid dynamics (CFD) model using ANSYS-Fluent. The MRR model constitutes of Ni-based catalyst filled reforming zone, Pd-based hydrogen-selective membrane, and permeate zone for hydrogen recovery. The developed model has been examined for several parameters including steam-to-methane ratio, flow rate, sweeping conditions, flow direction, reformer pressure and membrane length. The results indicated a substantial increase in methane conversion with a higher steam-to-carbon (S/C) ratio for a given feed flow rate. The methane conversion increased from 34% to 63% when the S/C ratio is increased from 2 to 6 at a methane mass flow rate of 0.0018 kg/s. The results also indicate an increase in hydrogen recovery with the decrease in feed flow rate for a fixed steam-to-methane ratio. Hydrogen recovery decreased from 28% to 2% when the mass flow rate of methane is increased from 5 × 10-5 kg/s to 1.8 × 10-3 kg/s, at a fixed S/C of 4. The incorporation of sweeping steam demonstrated a significant improvement in hydrogen recovery increasing from 15% to 33% with a sweep flow rate equal to the feed flow rate and methane mass flow rate of 1.8 × 10-4 kg/s. Further increase in sweep flow rate showed very small increase in hydrogen recovery, therefore in order to minimize the use of sweeping steam, a sweeping steam flow rate equal to the feed flow rate is suggested. Furthermore, flow direction, reformer pressure and membrane length were also found to play vital role in MRR performance.

Methane dehydroaromatization over Mo and W catalysts supported on ZSM-5

Methane aromatization reaction to produce benzene using tungsten and molybdenum catalysts supported on ZSM-5 was investigated at 800 oC. Catalysts were prepared by impregnation of tungsten and molybdenum salts on ZSM-5 zeolite with various metal loadings in the range of 2-10 wt. %. In order to obtain the catalytic structures before and after the reaction, catalysts were characterized by XRD and FTIR analysis. It was indicated from reactor tests that increase of metal loading on the catalyst surface leads to increase methane conversion (1.1% and 3.2% for 2W/ZSM-5 and 6 W/ZSM-5, and 2.4% and 4.8% for 2W/ZSM-5 and 6 W/ZSM-5, respectively, at time of stream equals 120 min). It was also concluded that Mo catalysts show higher activity and stability than W (methane conversion of 3.2 and 9 % using 10Mo/ ZSM-5 and 10 W/ZSM-5 catalysts respectively, at time of stream equals 100 min), and increase of Mo loading leads to enhancement of catalytic activity and methane conversion, which indicate initial activation of methane is occurred on metal sites of catalysts. This activation leads to occur the later reactions and production of final benzene. These conditions confirm the two-factor mechanism which include two stages: i) hemolysis break of C-H bond and CH3 radical formation and then ethylene formation, and ii) cyclization of ethylene species in the presence of acidic sites within the zeolite channels. Investigations on mesoporous HMS support showed no aromatic production, which show increase of support channel diameter leads to reduce the possibility of ring formation.

Numerical simulation of heat‐pipe and folded reformers for efficient hydrogen production through methane autothermal reforming

In order to intensify the methane autothermal reforming (ATR) process for efficient hydrogen production, novel heat-pipe and the folded reactors were designed and studied by numerical simulations. The reactor performance, such as methane conversion rate, hydrogen yield, and temperature difference between the reactor inlet and outlet, was computed and compared for both traditional tubular reactors and the novel reactors. Under the optimum operating parameters, compared with the tubular reactor, the heat pipe reactor and the folded reactor can help to increase methane conversion rate from 34% to 45% and 50%, while hydrogen productivity from 22.2% to 28.6% and 31.4%, respectively. The performance of the heat pipe reactor depends on the length and position of the heat pipe, while for the folded reactor, thicker intermediate plate with higher thermal conductivity material is more beneficial. Results were compared with previous experiments and could be used as a reference to guide new experimental and theoretical works toward the ultimate goal of designing and optimizing the ATR reactors for hydrogen production in the future.