Methane Conversion Rate Research Articles

A novel biogas-driven CCHP system based on chemical reinjection

In the process of vaporizing water within the biogas-driven CCHP system based on chemical recuperation, a significant temperature disparity in heat transfer exists, leading to increased irreversible loss, and the methane conversion rate is low because the gas turbine exhaust gas is difficult to drive efficient methane conversion. This paper proposed a novel biogas-driven CCHP system based on chemical reinjection. Through the reinjection of a portion of the exhaust gas into the reactor, a self-thermal reforming reaction process is engineered, leading to a substantial enhancement in methane conversion rate. The heat matching of the heat exchange unit is optimized by the reheat air, and the power generation and cooling capacity of the system are improved. Notably, the electricity and cooling generation of the new system increased by 55.52 kW (6.20 %) and 542.49 kW (101.49 %), respectively, while the exergy efficiency increased by 8.31 %. The study delves into the influence of key parameters on the system thermal performance. During the reforming process, the exhaust gas split ratio has a significant impact on carbon deposition and methane conversion. When the methane is nearly completely converted, there is no significant change in electricity generation of the system. Excessive turbine inlet temperature is found to be unfavorable for improving the exergy efficiency of the new system from a holistic system perspective. Finally, a comprehensive comparison of the thermal performance between the new system and the reference system is conducted under various ambient temperatures. This study offer a new design scheme for the efficient utilization of biogas.

Mechanism on CMD reaction regulated by supports and promoters of Fe-based catalysts

Methane cracking technology for low-carbon energy conversion to produce hydrogen is a key technical approach in the pursuit of fossil energy decarbonization. Catalytic methane decomposition (CMD) is a process that accomplishes the fundamental removal of carbon from fossil energy without oxygen, producing high-quality carbon-based materials and H2. The functionality of supports and promoters was investigated using inorganic metal oxide support Al2O3, supported active metal Fe, and cocatalyst K. The results show that the Al2O3–Fe catalyst achieves the highest CH4 conversion of 65% at 850 °C, with a gas-phase H2 yield of 1189.72 mmol/gFe within 3 h, and a solid-phase carbon yield of 6.32 g/gFe, significantly higher than at 750 °C. The Al2O3–Fe–K catalyst achieves a methane conversion rate of 66.28% at 850 °C for 1.5 h, exhibiting relatively fast deactivation. The Al2O3–Fe catalyst catalyzes the formation of carbon nanotubes (CNTs) through methane cracking, resulting in mainly 'chain-locked' morphology. The promoter K acts on the surrounding metal clusters to influence the dispersion of active metal. The Al2O3–Fe–K catalyst is more favorable for the production of 'bamboo-shaped' carbon nanotubes, suggesting that K has a more significant impact on shaping the CNTs' products.

Thermochemical energy storage analysis of solar driven carbon dioxide reforming of methane in SiC-foam cavity reactor

Solar energy is an abundant renewable energy source, and the use of solar energy for carbon dioxide reforming of methane (CRM) is a promising thermochemical energy storage scheme, but the reactor using the traditional powder catalyst has the disadvantages of complex encapsulation and low energy storage efficiency. In this paper, porous SiC-foam with high thermal conductivity is used to prepare Ni/CeO2–Al2O3/SiC catalyst, and then is loaded into a cavity reactor to achieve highly efficient and stable CRM under solar simulator. After a period of reaction, methane conversion rate remains high. As inlet flow rate decreases and incident energy flux rises, methane conversion rate is improved, and thermochemical energy storage efficiency first rises and then drops with maximum 31.4%. The numerical model of the cavity reactor under concentrated heat flux is established, and the simulation results are in good agreement with the experimental data. The structure of catalyst bed directly influences the heat storage performance, and the optimal bed thickness, radius and porosity are obtained. For thick bed, the reverse reaction appears in the end region of the bed, and then this region expands with bed thickness rising, so the reaction rate first increases and then decreases.

Analysis of heat transfer performance and system energy efficiency of catalytic combustion heaters for low calorific value waste gas application to oil shale in-situ conversion

In this study, we explore the utilization of low calorific value waste gas for in-situ conversion mining of oil shale. Through simulation, we analyze the effects of variations in the parameters of the catalytic combustion heater's independent variables on the exhaust gas temperature, methane conversion rate, and system energy efficiency (dependent variables). The results demonstrate that larger values of the pore radius, gas injection flow rate, and pulsation flow rate parameters lead to reductions in the corresponding dependent variables. The system's energy efficiency remains stable between 21.94% and 22.46% with increasing gas injection temperature. Furthermore, an increase in the oxygen molar fraction results in elevated methane conversion rates from 0.64% to 58.2% and system energy efficiency from 0.4% to 21.51%. Conversely, an increase in the methane molar fraction causes a decrease in methane conversion from 76.17% to 7.18% and a decline in system energy efficiency from 32.83% to 7.18%. Notably, gas flowback occurs at downhole pressure conditions of 2 MPa. The variation in pressure stabilizes the system's energy efficiency between 21% and 22.10%. The simulation and analysis findings of this study provide significant reference value for subsequent practical testing efforts.

Catalytic Partial Oxidation of Methane to Methanol over Fe2O3/MWCNTs

The catalytic partial oxidation of methane (CPOM) to methanol has been regarded as a promising approach for methane utilization, despite that the conversion remains a formidable challenge in the perspective of catalysts. A novel catalyst system of multi-wall carbon nanotubes (MWCNTs) that supported Fe2O3 with existing I2, consisting of non-noble metal and working in weak acid at an ambient temperature, was investigated for CPOM. MWCNTs supported the Fe2O3 catalyst, which was prepared by the impregnation method and characterized via HRTEM, XRD, XPS, FT-IR, and BET techniques. The characterization results reveal that, as a non-noble metal catalyst, the Fe2O3/MWCNTs catalyst had a good catalytic performance and stability in the CPOM. With the variation of reaction pressure and the dosage of Fe2O3/MWCNTs, the catalyst system obtained the highest methane conversion rate of 7.41% and methanol selectivity of 86.3%, which is analogous to that of the equivalently strong acid catalyst system. The I2-Fe2O3/MWCNTs catalyst system has great potential in the application of CPOM under mild, environmentally benign conditions, such as non-noble metal requirement, ambient temperature, and weak acid. The reaction mechanism was discussed.

Thermally enhanced solid-liquid separation process in food waste biorefinery: modelling the anaerobic digestion of solid residues.

The biochemical valorization potential of food waste (FW) could be exploited by extracting decreasing added-value bio-based products and converting the final residues into energy. In this context, multi-purpose and versatile schemes integrating thermal and biochemical conversion processes will play a key role. An upstream thermal pretreatment + solid-liquid separation unit was here proposed to optimize the conversion of the liquid fraction of FW into valuable chemicals through semi-continuous fermentation process, and the conversion of the residual solid fraction into biomethane through anaerobic digestion. The solid residues obtained after thermal pretreatment presented a higher soluble COD fraction, which resulted in higher methane production with respect to the raw residues (0.33 vs. 0.29 Nm3CH4 kg-1VSfed) and higher risk of acidification and failure of methanogenesis when operating at lower HRT (20d). On the contrary, at HRT = 40 d, the pretreatment did not affect the methane conversion rates and both tests evidenced similar methane productions of 0.33 Nm3CH4 kg-1VSfed. In the reactor fed with pretreated residue, the association of hydrogenotrophic methanogens with syntrophic bacteria prevented the acidification of the system. Modelling proved the eligibility of the FW solid residues as substrates for anaerobic digestion, given their small inert fractions that ranged between 0% and 30% of the total COD content.

Synergistic promotions between high purity H2 production and CO2 capture via sorption enhanced chemical looping reforming

Hydrogen energy, a promising clean source, holds potential to combat global warming. To achieve efficient and low-carbon H2 production, we proposed an isothermal sorption-enhanced chemical looping reforming (SE-CLR) process to realize the high-purity hydrogen production and in-situ CO2 capture at mild temperatures (550–650 °C). For practical application, the process is characterized to use Fe-Ni double metal oxide particles as steam methane reforming oxygen carriers, and K2CO3-promoted Li4SiO4 particles as CO2 sorbent. The oxygen transfer capacity of metal oxide matintained high at 57.4%, and the K-Li4SiO4 absorbents remained at 22.5% CO2 absorption capacity over 200 isothermal absorption-regeneration cycles. Conducting a synergistic conversion mechanism within double metal oxides and absorbents, and adjusting the absorbent-to-metal oxide mass ratio to 7:4, enhanced hydrogen purity to 92% and CO2 uptake to 95%. Furthermore, in-situ CO2 removal in CLR processes achieved methane conversion and H2 production rates equivalent to conventional CLR processes under the same reaction conditions, but at temperatures ∼60 °C lower. The effects of the reaction temperature, pressure, steam-to-methane and methane-to-solid ratios on SE-CLR performance were studied systematically. Finally, stable hydrogen production with a purity of 91%–89% and CO2 uptake of 94%–91% were obtained over 25 CLR cycles, with minimal changes in mechanical strength of particles.

Continuous Flow System for Highly Efficient and Durable Photocatalytic Oxidative Coupling of Methane.

Photocatalytic oxidative coupling of methane (OCM) into value-added industrial chemicals offers an appealing green technique for achieving sustainable development, whereas it encounters double bottlenecks in relatively low methane conversion rate and severe overoxidation. Herein, we engineer a continuous gas flow system to achieve efficient photocatalytic OCM while suppressing overoxidation by synergizing the moderate active oxygen species, surface plasmon-mediated polarization, and multipoint gas intake flow reactor. Particularly, a remarkable CH4 conversion rate of 218.2 μmol h-1 with an excellent selectivity of ∼90% toward C2+ hydrocarbons and a remarkable stability over 240 h is achieved over a designed Au/TiO2 photocatalyst in our continuous gas flow system with a homemade three-dimensional (3D) printed flow reactor. This work provides an informative concept to engineer a high-performance flow system for photocatalytic OCM by synergizing the design of the reactor and photocatalyst to synchronously regulate the mass transfer, activation of reactants, and inhibition of overoxidation.

CO2-Free Hydrogen Production by Methane Pyrolysis Utilizing a Portion of the Produced Hydrogen for Combustion

Air pollutants such as carbon dioxide and nitrogen oxides emitted by the combustion of fossil fuels have become the subject of increasing concern. Hydrogen has accordingly emerged as a promising low-emission alternative energy source. Among the various methods for hydrogen production, methane pyrolysis, which produces hydrogen without emitting carbon dioxide, has gained substantial attention. This study evaluated the self-sustainability of a new hydrogen production system based on methane pyrolysis, in which a portion of the hydrogen produced is used as combustion fuel rather than relying on catalysts and electrical heating. Coupled heat transfer and one-dimensional reaction simulations employing two plug-flow reactors of a counterflow double-pipe heat exchanger were conducted to investigate the feasibility and efficiency of the proposed system, as well as the influence of flow conditions on hydrogen production. The results confirmed system viability, informed the estimation of hydrogen production rates, and provided methane conversion rate data emphasizing the critical role of low-flow conditions and residence time in system efficiency. Additionally, the production of carbon constituted a significant aspect of system efficiency. These findings indicate that the proposed system can produce environmentally friendly hydrogen, contributing to its potential utilization as a sustainable energy source.

Improving the performance of porous volumetric solar reactor with biomimetic leaf vein structures and spectrally selective gradual porous parameters

The steam reforming of methane to hydrogen production in porous volumetric solar reactor is a promising way for solar energy utilization, which realize the conversion of solar energy to chemical energy. Due to the strong non-uniform volumetric inner heat source distribution in the porous catalyst and the varying concentration of methane, the porosity and pore diameter distribution of the porous catalyst should be carefully designed to improve the thermochemical performance. We firstly design a solar porous media volumetric reactor with a leaf vein bionic structure. Then, we numerically analyze the impact of leaf vein structure and pore size on the thermochemical performance of the reactor. The results show that the bionic leaf vein structure can regulate the distribution of methane and improve the chemical reaction rate. Compared with the traditional reactor, the reactor with non-parallel biomimetic leaf vein structure II can increase the methane conversion rate by 8.11 %. The pore size difference between the two regions is 0.5 mm that is limited within a small range, and the reactor has good performance. This paper can provide a guidance for porous volumetric solar reactor design to improve the thermochemical reactions performance.

Influence of Mn, Mg, Ce and P promoters on Ni-X/Al2O3 catalysts for dry reforming of methane

In this work, the performance of a series of nickel catalysts supported on alumina containing the promoters Mg, Mn, Ce and P was evaluated against the dry reforming of methane (DRM). Alumina support was obtained quickly and simply through the microwave-assisted combustion method using low levels of urea. The catalysts were characterized by XRD, TPR, FTIR and XRD in situ, proving that successive hydration and heat treatment steps during synthesis can generate modifications in the alumina phases, in addition to the formation of aluminate species that are reduced during the catalytic activation step and modify the level of interaction between active and support phases. The catalytic activity test was performed with GHSV = 100 L g−1 h−1 and the formed carbon was quantified by thermogravimetric analysis. The Mn promoter exhibited the highest methane conversion rate during the initial stages of the reaction, in which the presence of MnO2 favored parallel reactions of methane decomposition. The phosphorus and cerium produced smaller amounts of coke, reducing the carbon generated due to the interaction of promoters with carbon on the surface of the catalytic sites. The Mg increases the interaction of the active phase with the support.

A CFD model of natural gas steam reforming in a catalytic membrane reactor: Effect of various operating parameters on the performance of CMR

The use of hydrogen as an energy carrier has increased for reasons related to its environmentally friendly characteristics. The most common and low-cost method of producing hydrogen from natural gas (or CH4) is the steam reforming process. The 2-D axisymmetric catalytic membrane reactor (CMR) model is developed for pure hydrogen production from real natural gas (NG) using a Pd–Ru membrane with a Ni/Al2O3 catalyst. In this paper, a CFD model is prepared to investigate the performance of a catalytic membrane reactor through natural gas conversion and hydrogen production under various operation parameters, i.e., temperature of reaction in the range of 600, 700, 800, 900, and 1000 K, gas hourly space velocity GHSV with a range of 500, 700, 1000, 2000, and 3000 h−1, and sweep gas flow rate (Re No.) 1, 50, 100, 150, and 250. The results of the simulation show that the CMR exhibits a high permeation rate of hydrogen on the permeate side (tube side) and achieves a high methane conversion rate of approximately 99.9 % at 1000 K on the retentate side. The hydrogen flux exhibits a decline as the temperature increases from 900 to 1000 K, despite the achievement of complete (NG) conversion. Hence, it can be concluded that the performance of the catalytic membrane reactor (CMR) process exhibits a pattern of increase when the other parameters, such as (GHSV) and (Re.No.), are increased.

Methane C(sp3)-H bond activation by water microbubbles.

Microbubble-induced oxidation offers an effective approach for activating the C(sp3)-H bond of methane under mild conditions, achieving a methane activation rate of up to 6.7% per hour under optimized parameters. In this study, microbubbles provided an extensive gas-liquid interface that promoted the formation of hydroxyl (OH˙) and hydrogen radicals (H˙), which facilitated the activation of methane, leading to the generation of methyl radicals (CH3˙). These species further participated in free-radical reactions at the interface, resulting in the production of ethane and formic acid. The microbubble system was optimized by adjusting gas-liquid interaction time, water temperature, and bubble size, with the optimal conditions (150 s of water-gas interaction, 15 °C, 50 μm bubble size) yielding a methane conversion rate of 171.5 ppm h-1, an ethane production rate of 23.5 ppm h-1, and a formic acid production rate of 2.3 nM h-1 during 8 h of continuous operation. The stability and efficiency of this process, confirmed through electron spin resonance, high-resolution mass spectrometry, and gas chromatography, suggest that microbubble-based methane activation offers a scalable and energy-efficient pathway for methane utilization.

Biogas Reforming Combined with Co-Electrolysis inside AC:DC Operated Solid Oxide Electrolyser Cells

Upgrading biogas into added-value fuels and chemicals is seen as one of the main pathways to reduce carbon dioxide emissions from the energy sector. In particular, green methanol represents a strategical product due to its high versatility in the transportation and chemical industry. Biogas reforming is a key step in the upgrading process and it can be integrated with Power-to-X technology. The reforming can be conducted using Solid Oxide Electrolysers (SOEs). Furthermore, the outlet syngas composition can be adjusted and optimized for methanol production, via the additional production of hydrogen provided by the simultaneous steam electrolysis.This research focuses on analysing the effects of Dynelectro’s patented AC:DC operation [EP3719171A1, WO2020/201485A1, EP3947779A1] applied to biogas-fed SOE cells. The principle of this novel operating condition is to impose an alternating current over a direct current, which for SOE translates into reversing the polarization of the cell and having a regular switch between fuel cell mode and electrolysis mode. When performing steam electrolysis, the benefits of AC:DC operation are already proven to consist in reduced degradation, due to impurities removal, and enhanced temperature control during dynamic operations [Skafte, 2022]. When the SOE cell is fed with a composition of methane, carbon dioxide and steam, the main issue to solve is the high energy requirement from the steam reforming process and the steam electrolysis performed simultaneously. In fact, both reactions are endothermic at SOE operating conditions (750°C and ambient pressure), with an enthalpy difference of respectively 225 kJ/mol and 248 kJ/mol. In this regard, the AC:DC operation can provide additional heat, because of the polarization switch to fuel cell mode, and avoid the temperature drop within the SOE. Moreover, it is possible to tune the rate of co-electrolysis and biogas reforming.A mathematical model is developed to simulate biogas reforming in an AC:DC operated SOE cell. The model includes mass transport, electrochemistry, catalytic reactions and energy balance. The composition of biogas is assumed to be mainly methane and carbon dioxide. By operating both in DC and AC:DC, this gives a first indication of the extent of the expected benefits. To validate the model, laboratory experiments are performed, where single SOE cells are operated in an imitated biogas compositions and the outlet gas is analysed using gas chromatography. These experiments include current-voltage (i-V) curves and electronic impedance spectroscopy (EIS) analysis, which can be used to measure the performances of such operations by observing the cell voltage and the degradation rate.The results from ordinary direct current operation and Dynelectro’s AC:DC operation are compared in terms of syngas composition and operating voltage. The optimal composition of syngas for methanol synthesis, consisting of a ratio of hydrogen to carbon monoxide of approximately 2 and low traces of methane, is achieved. Reduced methane content in the outlet gas is shown when operating the SOE cells with AC:DC current, compared to DC operations. The latter shows a CH4 molar fraction of approximately 1%, while the former allows the CH4 concentration to go below this level, depending on the AC:DC parameters. It is found that the rate of methane and carbon dioxide conversion is dependent on the frequency and duty cycle of the AC:DC operation. The achievement of stable conditions during these operations leads to an optimized biogas to syngas conversion, and a simplified overall biogas to methanol process.

Inlet baffle structural optimization and reforming performance of exhaust gas-fuel reformer for marine LNG engine

The structural and boundary conditions are pivotal factors influencing the performance of the reformer. However, previous research primarily relied on tailored theoretical boundary conditions specific to the research requirements, often conducted in low airspeed conditions ranging from 700 ℃ to 1000 ℃. There is a lack of research focused on the complex and dynamic process of reforming hydrogen production process in reformers that handle exhaust gas components with high flow rates, high dilution, complex compositions, and low to medium temperatures (300 °C–600 °C) as boundary conditions. The objective of this study is to optimize the structure of the reformation reactor while exploring its hydrogen reforming characteristics. Therefore, this study focused on the simulation-based optimization design of an EGR reformer for marine natural gas engines. A comprehensive model was developed by coupling fluid flow, heat transfer, and surface reactions on a nickel-based catalyst. The accuracy of the model was validated through experimental data from a single-tube fixed-bed catalytic reforming experiment. The results highlighted the importance of the reformer design, with the optimal configuration incorporating two baffle plates positioned at angles of 15° and 35°. This design achieved the most uniform flow field and minimal pressure drop among the six investigated configurations. Furthermore, the study emphasized the significance of reforming gas composition in achieving high performance. The optimal reforming gas composition was found to have an M/O value of approximately 2 and an S/M value of approximately 1. This resulted in an outlet hydrogen concentration of approximately 18.8%, hydrogen yield of approximately 46.1%, methane conversion rate of approximately 66.2%, and an energy efficiency of 71%. It was observed that increasing the EGR rate led to a decrease in performance indicators, with a more pronounced effect observed at an M/O value of 1. This study provides valuable insights into the performance optimization of EGR reformers for marine natural gas engines. The findings offer guidance on selecting operational parameters to enhance efficiency and hydrogen production.

Numerical study of exhaust chemical composition in a methane DBD plasma actuator under different operating conditions

In this paper, numerical simulations of a Dielectric-Barrier Discharge (DBD) plasma actuator are performed to predict its output chemical composition. The plasma actuator is cylindrical, with two coaxial electrodes and a quartz dielectric. The electrical discharge occurs in a pulsed manner around the quartz wall. This device is utilized for methane conversion in plasma-assisted combustion applications. The effects of voltage, frequency, temperature, and relative permeability parameters on methane conversion and some selected species concentrations were investigated. The results show that plasma discharging converts methane to hydrogen and heavier hydrocarbons such as C2H3, C2H4,C2H5, C2H6, and C3H8. Moreover, increasing the relative permeability coefficient and voltage had the greatest effect on methane conversion. Increasing the relative permeability from 2 to 6 increases the methane conversion by 43 % and also increases the H2 density by 57 %. The conversion rate of methane and the H2 density increase by 18 % with increasing the voltage from 6 to 8 kV. The partial conversion of methane to hydrogen and radical species benefits combustion applications in terms of flame stability and emissions reduction.

Engineering defective Co3O4 containing both metal doping and vacancy in octahedral cobalt site as high performance catalyst for methane oxidation

Advanced defective structure in Co3O4 catalyst plays a vital role in the boost of catalytic oxidation activity. In this study, a rational defects engineering strategy was developed by precise implanting Ce and Al in the octahedral site of Co3O4, followed by the partial de-doping of the Al atoms. Distorted crystal, abundant oxygen vacancies, higher specific surface area are synergistically incubated by the dual dopants combined with the metal vacancies. The Co3+O bond could be significantly stimulated to guarantee an excellent methane oxidation activity, with methane conversion rate more than 1.5 times compared with the original Co3O4 catalyst at 300 °C. This work exemplifies the importance of accurate multi-defects manipulation in Co3O4 for intrinsic oxidizability improvement.

Fundamental characteristics of an integrated reactor with catalytic combustor and air pre-heater for compact solid oxide fuel cell systems

Bulky volume limits the application of solid oxide fuel cell (SOFC) systems in some scenarios. In this paper, a compact integrated reactor with combustor and air pre-heater is proposed. It is adapted by coating combustion catalyst to the hot-side of a plate-fin heat exchanger. The fundamental steady/transient characteristics of the reactor are investigated at different inlet settings in the warmup condition of a metal-supported SOFC.Results show that the reactor has a balanced combustion performance with a minimum methane conversion rate of 85.1%, while it can be effectively improved by reducing the excess air ratio. The reactor has better heat exchange capability than the traditional series arrangement of independent combustor and air pre-heater. There is about 68.7% of the reaction heat extracted by direct metal-substrate conduction and this dominates the heat exchange process. The reactor also has a good transient response. Methane conversion can be stable within 12.5 min; meanwhile, the output air temperature shows a good capability to track the development of stack temperature. Both the air temperature rise rate around 35 ˚C min−1 and the rise trend of first fast and then slow can meet the requirements of stack quick warmup. Overall, the methane conversion development within the reactor and the temperature rise of the stack reinforce mutually, and both can stabilize more quickly in this case.

1D modeling of methanation reactor with circulation (MeRCi) for assessment of reaction characteristics

For a power-to-gas (PtG) system, methanation has attracted attention to synthesize methane from carbon dioxide and hydrogen. There is a problem that heat generated by the reaction causes thermal degradation of the catalyst. Then, we have proposed a methanation reactor with circulation (MeRCi), where the temperature of the catalyst bed is controlled by recycling a part of the product gas. In this study, a one-dimensional model of the MeRCi was developed, and the methanation process was numerically simulated for assessment of reaction characteristics. The catalyst amount, the recycle ratio, and the catalyst bed length were changed. For comparison, the simulation of a straight-tube fixed-bed reactor was also simulated. Based on the gas temperature distribution of the straight-tube reactor, the simulation results show a good agreement with the experimental data, and the validity of our numerical model was confirmed. Even for the higher recycle ratio, the methane conversion rate at the reactor outlet does not change much, showing the high conversion rate within the simulation conditions. The increase of the catalyst packing density as well as the catalyst bed length enlarges the methane conversion rate. By considering the fact that the methane conversion rate is sufficiently high when the catalyst packing density is over 500 kg/m3, the reaction rate must be kept at certain level to keep the high methane conversion rate. As for the catalyst bed length, there is a minimum value at which the methane conversion rate is unexpectedly dropped where unreacted hydrogen and carbon dioxide are retained in the products.

Methane transformation into light olefins using methanol as co-reactant over Mo/HZSM-5

Direct conversion of methane into other value-added chemicals remains as a grand challenge due to its stable non-polar tetrahedral structure. Coupling methane with methanol over Mo-modified HZSM-5 is promising to activate methane at lower temperatures than for pure methane. This work investigates the effect of Si/Al ratio (25–250) and reaction conditions (reaction temperatures from 500 to 650 °C and methane-to-methanol molar ratios of 10 to 1 on methane conversion into light olefins (ethene, propene, butene)) using methanol as a co-reactant over 3Mo/HZSM-5. It was found that at 600 °C and CH4/CH3OH = 5 the 3Mo/HZSM-5 (Si/Al = 160) catalyst delivers the best performance of 0.72 mmol g−1 h−1 methane conversion rate and 50 % light olefins selectivity. Through 13C-labeled methane, this study also provided the direct evidence on the involvement of methane carbon in the reaction products. The results of this study enabled us to propose a possible reaction pathway for the methane-methanol coupling reaction.