CH4 Partial Pressure Research Articles

Tree stem-atmosphere greenhouse gas fluxes in a boreal riparian forest

Tree stems exchange greenhouse gases with the atmosphere but the magnitude, variability and drivers of these fluxes remain poorly understood. Here, we report stem fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in a boreal riparian forest, and investigate their spatiotemporal variability and ecosystem level importance. For two years, we measured CO2 and CH4 fluxes on a monthly basis in 14 spruces (Picea abies) and 14 birches (Betula pendula) growing near a headwater stream affected by historic ditching. We also measured N2O fluxes on three occasions. All tree stems were net emitters of CO2 and CH4, while N2O fluxes were around zero. CO2 fluxes correlated strongly with air temperature and peaked in summer. CH4 fluxes correlated modestly with air temperature and solar radiation and peaked in late winter and summer. Trees with larger stem diameter emitted more CO2 and less CH4 and trees closer to the stream emitted more CO2 and CH4. The CO2 and CH4 fluxes did not differ between spruce and birch, but correlations of CO2 fluxes with stem diameter and distance to stream differed between the tree species. The absence of vertical trends in CO2 and CH4 fluxes along the stems and their low correlation with groundwater levels and soil CO2 and CH4 partial pressures suggest tree internal production as the primary source of stem emissions. At the ecosystem level, the stem CO2, CH4 and N2O emissions represented 52 ± 16 % of the forest floor CO2 emissions and 3 ± 1 % and 11 ± 40 % of the forest floor CH4 and N2O uptake, respectively, during the snow-free period (median ± SE). The six month snow-cover period contributed 11 ± 45 % and 40 ± 29 % to annual stem CO2 and CH4 emissions, respectively. Overall, the stem gas fluxes were more typical for upland rather than wetland ecosystems likely due to historic ditching and subsequent groundwater level decrease.

Controls of Atmospheric Methane on Early Earth and Inhabited Earth-like Terrestrial Exoplanets

Methane (CH4) is a primarily biogenic greenhouse gas. As such, it represents an essential biosignature to search for life on exoplanets. Atmospheric CH4 abundance on Earth-like inhabited exoplanets is likely controlled by marine biogenic production and atmospheric photochemical consumption. Such interactions have been previously examined for the case of the early Earth where primitive marine ecosystems supplied CH4 to the atmosphere, showing that the atmospheric CH4 response to biogenic CH4 flux variations is nonlinear, a critical property when assessing CH4 reliability as a biosignature. However, the contributions of atmospheric photochemistry, metabolic reactions, or solar irradiance to this nonlinear response are not well understood. Using an atmospheric photochemical model and a marine microbial ecosystem model, we show that the production of hydroxyl radicals from water vapor photodissociation is a critical factor controlling the atmospheric CH4 abundance. Consequently, atmospheric CH4 partial pressure (pCH4) on inhabited Earth-like exoplanets orbiting Sun-like stars (F-, G-, and K-type stars) would be controlled primarily by stellar irradiance. Specifically, irradiance at wavelengths of approximately 200–210 nm is a major controlling factor for atmospheric pCH4 when the carbon dioxide partial pressure is sufficiently high to absorb most stellar irradiance at 170–200 nm. Finally, we also demonstrated that inhabited exoplanets orbiting near the outer edge of K-type stars’ habitable zones are better suited for atmospheric pCH4 buildup. Such properties will provide valuable support for future detection of life signatures.

Preparation of ultrafine WC-Co powder via fluidized bed

In this paper, the effects of reaction parameters on the deep-reduction and carbonization process of WO2-Co to WC-Co were studied. The results indicate that oxygen loss rate of WO2 is positively correlated with temperature and methane partial pressure. The partial pressure of methane has no significant effect on the formation rate of WC. The carbon content and particle size of the product increase with the increase of CH4 partial pressure. By synergistically regulating the reaction temperature to 950 °C, methane partial pressure to 1.25%, and reaction time to 60 min, ultrafine WC-Co powder without η phase can be obtained. The particle size of the composite powder is 128 nm, with total carbon content of 6.16%, free carbon content of 0.4%, and residual oxygen content of 0.05%, respectively. The growth rate relationship of tungsten carbide is as follows:

Large greenhouse gases emissions from lakes in Inner Mongolia, China

Lakes are important component of the regional carbon cycle and a significant sources of greenhouse gases (GHGs) to the atmosphere. However, the regional variations in carbon dioxide (CO2) and methane (CH4) emissions, as well as the factors regulating these emissions are poorly constrained. To investigate the regional GHG emission from lakes and their potential influencing factors, we conducted field measurements in 13 lakes in Inner Mongolia from July to August 2020. We found that the studied lakes were predominantly sources of atmosphere CO2 and CH4. The CO2 partial pressure (pCO2) exhibited supersaturation in 80 % of samplings, but all samplings of CH4 partial pressure (pCH4) showed supersaturation. Moreover, the average pCH4 is 40 times greater than that in the atmosphere. The lakes emitted substantial amounts CO2 and CH4 with average values of 25.8 ± 4.9 mmol m−2 d−1 and 2.1 ± 0.3 mmol m−2 d−1, respectively. At the regional scale, the dynamics of pCO2 and pCH4 are regulated by combination of various environmental factors. CO2 emissions from studied lakes decreased with the catchment net primary productivity (NPP), normalized difference vegetation index (NDVI), and nighttime lights which is indicative of urbanization. Conversely, CH4 fluxes increased with NPP, NDVI, and nighttime lights. We conclude that terrestrial carbon-cycling related variables and human activities significantly affect CO2 and CH4 emissions from lakes by transporting different nutrients, but they show opposite trends. Our results also exhibited that the freshwater lakes are the main contributors of CH4, while saline lakes are the main contributors of CO2. We suggest that increased human activity leads to changes in terrestrial carbon-cycle related processes which affects lake carbon emissions by altering the amount of nutrients input to the lakes.

H2 promotes the premature replacement of CH4–CO2 hydrate even when the CH4 gas-phase pressure exceeds the phase equilibrium pressure of CH4 hydrate

Submarine CO2 sequestration via solid hydrate has been considered a promising strategy for controlling greenhouse gas emissions. The simultaneous replacement of CH4 from subsea natural gas hydrates through buried CO2 offers a win-win approach. Utilizing H2 as an enhancer to promote CH4–CO2 hydrate replacement, coupled with integrating the replacement products into CH4 steam reforming for cyclic H2 production, presents a potential pathway for CO2 geological storage and eventual H2 recovery. However, the enhancement mechanism of H2 in the hydrate replacement process remains unclear. Focusing on the critical replacement condition, this study investigates the effects of gas-phase partial pressures on hydrate replacement in CH4-rich systems to elucidate the H2 influence mechanism. Remarkably, the results indicate, for the first time, that H2 induces premature CH4 hydrate dissociation under conditions exceeding the corresponding CH4 gas equilibrium pressure in CO2/CH4/H2 ternary gas systems. The critical condition for hydrate replacement depends on the total system pressure, rather than CO2 gas partial pressure. Additionally, in the CH4-rich systems, the driving force for CH4 hydrate decomposition takes precedence over that for hydrate reformation in controlling replacement. The replacement ratio increases from 16.7 % to 24.5 % as the CH4 partial pressure decreases from 2.01 MPa to 1.11 MPa at 274.15 K, despite simultaneous declines in both CO2 partial pressure and total system pressure from 1.70 MPa to 0.97 MPa and from 6.10 MPa to 3.39 MPa, respectively. These findings can provide insights into the improvement of CH4–CO2/H2 hydrate replacement efficiency and the development of oceanic CO2 sequestration.

Experimental investigation of integrated CO2 capture and conversion to syngas via calcium looping coupled with dry reforming of CH4

Calcium looping integrated with dry reforming of CH4 is a promising strategy for CO2 capture and in situ conversion to syngas. This intensified process is usually conducted with bifunctional materials that combine CO2 capture (CaO) and catalytic (Ni) active sites. Herein, the integrated calcium looping/dry reforming process was examined by investigating various bifunctional materials and operating conditions. The Ni loading of materials affected the interaction between active and inert phases, while adding a CaZrO3 promoter enhanced the CO2 capture and catalytic activities and the resistance toward sintering. Conducting experiments with a fluidized bed reactor (700 °C, 3% CH4 in feed) led to nearly complete CH4 conversion and ∼52% utilization of captured CO2 toward syngas production with steady H2/CO ratio close to unity. Temperature comprised a decisive parameter, with low values enabling high degrees of CO2 conversion up to ∼80%. The increase of CH4 concentration in the gas feedstock enhanced the rate of calcination and the conversion of CO2 over its desorption in the gas phase. Co-feeding O2 with CH4 was proposed to mitigate the energy demand, which reduced the reforming selectivity for the partial oxidation reaction and increased the H2/CO ratio of syngas.

Novel Energetic Co-Reactant for Thermal Oxide Atomic Layer Deposition: The Impact of Plasma-Activated Water on Al2O3 Film Growth.

In the presented study, a novel approach for thermal atomic layer deposition (ALD) of Al2O3 thin films using plasma-activated water (PAW) as a co-reactant, replacing traditionally employed deionized (DI) water, is introduced. Utilizing ex situ PAW achieves up to a 16.4% increase in the growth per cycle (GPC) of Al2O3 films, consistent with results from plasma-enhanced atomic layer deposition (PEALD). Time-resolved mass spectrometry (TRMS) revealed disparities in CH4 partial pressures between TMA reactions with DI water and PAW, with PAW demonstrating enhanced reactivity. Reactive oxygen species (ROS), namely H2O2 and O3, are posited to activate Si(100) substrate sites, thereby improving GPC and film quality. Specifically, Al2O3 films grown with PAW pH = 3.1 displayed optimal stoichiometry, reduced carbon content, and an expanded bandgap. This study thus establishes "PAW-ALD" as a descriptor for this ALD variation and highlights the significance of comprehensive assessments of PAW in ALD processes.

Class-III Hydrate Reservoir Depressurization Production Enhancement by Volume Fracturing and Cyclic N2 Stimulation Combination.

The depressurization effect is limited to class III hydrate reservoir recovery. To improve the depressurization effect, a new method of volume-fracturing and cyclic N2 stimulation combination (VFCS) was proposed. The production performance of this method was investigated by using numerical models based on reservoir parameters of the SH7 hydrate site in the South China Sea. The results show that (1) VFCS can greatly enhance the production performance with the average CH4 production rate being approximately 2.85 times higher than that of pure depressurization. This method combines the effects of volume fracturing and cyclic N2 stimulation by improving the seepage environment and further reducing the CH4 partial pressure in the gas phase. (2) High reservoir permeability, medium hydrate saturation, large volume-fracturing scale, low bottom-hole pressure, and high N2 injection amount can increase CH4 production by VFCS. (3) Although VFCS has the largest CH4 production volume and the highest hydrate dissociation degree among the studied production strategies, the reservoir temperature drop is significant by VFCS and future studies can be focused on the external heat supply to the reservoir to further improve the production.

Micro-mechanism of the effect of multi-component gas injection on methane recovery

To investigate how the micro-mechanism of multi-component gas injection affects the process of retrieving methane, a combination of density functional theory and molecular dynamics simulation method has been conducted under different gas injection ratios of CO2 and N2. The results of DFT demonstrate that the adsorption energy of the gas molecules over bituminous coal fragment are in order of CO2 > CH4 > N2. Independent gradient model analyses show that the Van der Waals interactions are the dominant force contributing to these three adsorption behaviors. To gain further insight into the influence of functional groups on CH4 adsorption, the radial distribution function analyses have been performed. It was found that oxygen-containing functional groups have a substantial impact on the adsorption of CH4 on coal molecules. Among these, CH4 preferentially adsorb around the hydroxyl group of coal molecule. Moreover, density profiles of the three gas molecules within nanopores demonstrate that CO2 molecules cause CH4 molecules to desorb by molecular swapping. In contrast, N2 slows down CH4 adsorption spontaneity by lowering CH4 partial pressure. Furthermore, it should be noted that increasing the proportion of CO2 in the gas mixture system can significantly improve the displacement efficiency of CH4. Conversely, the diffusion coefficient becomes small. The microscopic mechanism revealed in the present work helps us gain a better understanding of gas displacement processes, which provides new insights for optimizing gas injection compositions for field applications.

Effect of Co3O4 powder on the explosion characteristics and CO products of methane-air mixture

Rapid removing toxic CO for methane-air mixture explosions is essential in reducing casualties, but relevant research is rare. This paper proposed a novel approach for efficient CO removal and explosion suppression for methane-air mixture explosions using Co3O4 powder. The effect of Co3O4 powder on the explosion characteristics and basic parameters to quantify the CO removal performance have been studied, mainly including maximum explosion pressure (Pm), combustion time (tc), flame propagation velocity, and average CO removal rate (Rave.). Results indicated that explosion intensity and CO concentration decreased significantly with Co3O4 powder, due to increased heat absorption capacity and the active site of CO catalytic oxidation. However, the average CO removal rate decreased as the Co3O4 powder usage and CH4 partial pressure increased, which could reduce the dispersion degree of the Co3O4 dust cloud. The CO removal was achieved through the CH4 catalytic combustion and CO catalytic oxidation, which could reduce the CO generation and oxidize the generated CO to harmless CO2, respectively. This work provides a novel routine to lessen the explosion hazards and has promising applications in emergency rescue.

Thermal defect healing of single-walled carbon nanotubes assisted by supplying carbon-containing reactants

We experimentally investigated the effect of carbon-containing reactants (C2H2) on healing the defects in single-walled carbon nanotubes (SWCNTs) by thermal processes at high temperatures (∼1100 °C). Introducing C2H2 notably improved the crystallinity of healed SWCNTs compared with the thermal process in Ar ambient without C2H2. The defect healing rate increased with increasing C2H2 partial pressure, and the healing effect of C2H2 was more remarkable for relatively thinner SWCNTs (<1.1 nm). Combined with the relevant theoretical work reported previously, we propose a healing model in which C2H2 helps to heal the vacancy defects and increases the healing rate at high temperatures.

Greenhouse gas emissions from Daihai Lake, China: Should eutrophication and salinity promote carbon emission dynamics?

Greenhouse gases (GHGs) emitted or absorbed by lakes are an important component of the global carbon cycle. However, few studies have focused on the GHG dynamics of eutrophic saline lakes, thus preventing a comprehensive understanding of the carbon cycle. Here, we conducted four sampling analyses using a floating chamber in Daihai Lake, a eutrophication saline lake in Inner Mongolia Autonomous Region, China, to explore its carbon dioxide (CO2) and methane (CH4) emissions. The mean CO2 emission flux (FCO2) and CH4 emission flux (FCH4) were 17.54 ± 14.54 mmol/m2/day and 0.50 ± 0.50 mmol/m2/day, respectively. The results indicated that Daihai Lake was a source of CO2 and CH4, and GHG emissions exhibited temporal variability. The mean CO2 partial pressure (pCO2) and CH4 partial pressure (pCH4) were 561.35 ± 109.59 µatm and 17.02 ± 13.45 µatm, which were supersaturated relative to the atmosphere. The regression and correlation analysis showed that the main influencing factors of pCO2 were wind speed, dissolved oxygen (DO), total nitrogen (TN) and Chlorophyll a (Chl.a), whereas the main influencing factors of pCH4 were water temperature (WT), Chl.a, nitrate nitrogen (NO3−-N), TN, dissolved organic carbon (DOC) and water depth. Salinity regulated carbon mineralization and organic matter decomposition, and it was an important influencing factor of pCO2 and pCH4. Additionally, the trophic level index (TLI) significantly increased pCH4. Our study elucidated that salinity and eutrophication play an important role in the dynamic changes of GHG emissions. However, research on eutrophic saline lakes needs to be strengthened.

Computational simulation study on adsorption and separation of CH4/H2 in five higher-valency covalent organic frameworks

The density functional theory (DFT) calculation and molecular simulation were implemented to investigate the structural characteristics and the adsorption/separation properties of CH4/H2 on five borophosphonate based higher-valency covalent organic frameworks (BP-COFs). The computed results reveal that five BP-COFs possess the low density, high void fraction, suitable pore size and accessible surface area for CH4 and H2. The grand canonical Monte Carlo (GCMC) simulations indicate that the CH4 uptake capacity is higher than H2 in all five BP-COFs at 298 K and BP-COF-1 and BP-COF-4 possess the better capacity for separating CH4 form CH4/H2 mixture with low CH4 partial pressure. The centroid density distribution profiles display that the preferable sites for CH4 and H2 are both located at the corners formed by the linear ligands and the hexahedron B4P4O12 clusters. This work may provide some inspiration for further exploring higher-valency COFs as gas adsorption/separation media.

Dissociative adsorption of hydrogen and methane molecules at high-angle grain boundaries of pipeline steel studied by density functional theory modeling

Pipelines provide an economic and efficient means for hydrogen transport, contributing to accelerated realization of a full-scale hydrogen economy. Dissociative adsorption of hydrogen molecules (H2) occurring on pipe steels generates hydrogen atoms (H), potentially resulting in hydrogen embrittlement of the pipelines. This is particularly important for existing pipelines transporting hydrogen in blended form with methane (CH4). In this work, a density functional theory model was developed to investigate the dissociative adsorption of H2 and CH4 at high-angle grain boundaries (HAGB), a typical type of hydrogen traps contained in steels, and the stable adsorption configurations. Results demonstrate that the dissociative adsorption of both H2 and CH4 at the HAGB is thermodynamically feasible under pipeline operating conditions. Compared with crystalline lattice sites, the HAGB possesses the most negative free energy change, a lower energy barrier and the lowest H-adsorption energy, making the HAGB, especially the quasi three-fold site, become the most stable site for hydrogen adsorption. The saturation coverage of hydrogen at HAGB is calculated to be 1.33. The iron-H bonds are formed at the HAGB by charge consumption at Fe atoms and electron accumulation at H atoms, following a so-called electron hybridization mechanism. The CH4 adsorption at HAGB affects the H2 adsorption. Without pre-adsorption of CH4, the hydrogen adsorption at the HAGB is more stable. Although an elevated CH4 partial pressure decreases the thermodynamic tendency for H2 adsorption, it cannot hinder occurrence of the H2 dissociative adsorption.

Influences of diffusion-limited transport in the crystals and initial water on the gaseous CO2 dynamic replacement in CH4 hydrate

CO2–CH4 dynamic replacement is a process of the CO2–CH4 replacement method. In this process, CO2 is injected into CH4 hydrate-bearing sediment continuously to recover CH4. The dynamic replacement process can be divided into the CO2 displacement stage and the subsequent dynamic replacement stage and is affected by the existence of initial water and diffusion-limited transport caused by the mixed hydrate layer. Effective fugacity is utilized to combine the thermodynamic model and kinetic model to investigate the effects of the above two factors on the CH4–CO2 dynamic replacement process. Initial water is assumed to distribute in the pore space. The CH4 hydrate decomposition due to the decrease of CH4 partial pressure in the gas phase during the CO2 displacement stage is considered. Our investigation results show that diffusion-limited transport is the main factor that restricts the replacement percent in the displacement stage, the effect of the existence of initial water on the replacement percent is more obvious than that of the diffusion-limited transport. CO2 storage efficiency is less than 10% during the entire dynamic replacement and is mainly affected by the existence of initial water rather than the diffusion-limited transport. The temperature increase is mainly due to newly formed hydrate. Finally, more CH4 hydrate is exploited near the outlet than that near the inlet. Therefore, the CH4–CO2 replacement method needs to be enhanced near the inlet. CO2 is mainly sequestrated in the CO2 hydrate formed through free water. CO2 sequestrated in the mixed hydrate is mainly distributed near the inlet, while the CO2 sequestrated in the CO2 hydrate is mainly distributed near the outlet.

Physical Factors and Microbubble Formation Explain Differences in CH4 Dynamics Between Shallow Lakes Under Alternative States

Submerged macrophytes play a key role in maintaining clear vegetated states in shallow lakes, but their role on methane (CH4) dynamics is less explored. They might enhance methanogenesis by providing organic matter but they can also supply oxygen to the sediments increasing methanotrophy. They may also affect gas exchange by diminishing wind turbulence in the water column. We previously measured seasonal CO2 and CH4 partial pressure (pCO2 and pCH4) and diffusive fluxes from two clear vegetated and two turbid algal shallow lakes of the Pampean Plain, Argentina, and we reported that clear lakes had higher mean annual pCH4 despite states having similar mean annual CH4 diffusive flux. In this study we explore the contribution of physical and biological factors regulating surface pCH4. Mean annual CH4 diffusive fluxes and CH4 fraction of oxidation (Fox) were similar between states, implying a comparable mean annual CH4 input. kCH4 was significantly higher than kCO2, suggesting occurrence of CH4 microbubbles, yet kCH4 was higher in turbid lakes than in clear lakes, implying a higher microbubble formation in turbid lakes. Furthermore, in turbid lakes there were positive relationships between k and wind speed, and between k and pCH4, yet in clear lakes these relations were absent. Results suggest that submerged vegetation suppresses wind induced turbulence in clear vegetated lakes, decoupling kCH4 from wind and reducing microbubble formation, therefore augmenting pCH4 in their surface waters. Overall, physical rather than biological factors appear to control the observed differences in pCH4 between states.

Competitive adsorption in CO2 enhancing shale gas: Low-field NMR measurement combined with molecular simulation for selectivity and displacement efficiency model

CO2 enhanced shale gas recovery is considered to be a potential method of shale gas development and CO2 reduction. However, core experiments cannot independently analysis competitive adsorption when the partial pressure of CH4 in the core sample keeps changing during displacement. In this study, an experimental method based on low-field nuclear magnetic resonance (NMR) and in situ gas chromatography is developed to quantitatively analyze the competitive adsorption of shale particles. As was demonstrated in our previous study, the adsorption capacity of the nanopores at various pressures can be obtained from the transverse relaxation spectrum of NMR and the change in pressure in a reference cavity. By NMR experiment combined with gas chromatography, the competitive adsorption selectivity of CH4 and CO2 in nanopores is investigated. In addition, molecular simulations are used to simulate the competitive adsorption and selectivity of CO2 and CH4 in shale nanopores with different pore structures, sizes, and shapes. The results reveal that as the pressure, carbon dioxide mole fraction, temperature, and pore size increases, the competitive adsorption selectivity S decreases. However, it remains greater than one, which demonstrates that CO2 has a stronger adsorption ability than CH4. For shale gas development, as the total pressure decreases, the contribution of the competitive adsorption effect becomes significant. A competitive adsorption model for CO2 and CH4 is established, and it is shown to fit the experimental data and simulation data well at different pressures. Finally, based on single-component adsorption results, we can separate the different effects and predict the displacement efficiency, which may provide a criterion in field scale simulations.

Characteristics of carbon source greenhouse gas flux in the water–air formation in the middle and upper reaches of the Three Gorges Reservoir

Abstract This study selected five points in the middle and upper mainstream of the Three Gorges Reservoir area. Starting from May 2016, the greenhouse gases CO2 and CH4 from the water–air formation at the sampling points have been monitored month by month for 10 months. Using the headspace balance method and the thin boundary layer model estimation method, we obtained the CO2 and CH4 partial pressure ranges and the water–air formation diffusion flux at the mainstream point. It is found that the CH4 partial pressure of water body is significantly positively correlated with water temperature, and significantly negatively correlated with DO; the CH2 partial pressure of water body is positively correlated with water temperature, but negatively correlated with conductivity, DO, pH and wind speed. The diffusion fluxes of CH4 and CO2 at the water–air formation are positively correlated with CH4 partial pressure and water temperature, and negatively correlated with ph, DO and conductivity. It is also found that the reservoir has a certain mitigation effect on the release of CO2 from the river water body, and the CH4 diffusion flux at the water–air formation is roughly equivalent.

SYNGAS PRODUCTION FROM GREENHOUSE GASES VIA DRM OVER Ni/Al2O3 CATALYST: EFFECT OF Ca ADDITION

In view of the escalating global warming phenomenon, utilization of CO2 has become an important event in recent decades. Syngas production via Dry Reforming of Methane (DRM) is one of the promising methods to produce COX-free hydrogen as a renewable and sustainable energy source. DRM requires an active functioning catalyst since it is a highly endothermic process. The catalytic behaviour of 10 wt.% Ni supported on Al2O3 and doped with CaO is investigated for DRM. In the present study, the effect of alkaline earth metal oxide (CaO) loading (varying from 0.5-2.0 wt.%) on the structure, properties, stability, and performances of the Ni-CaO/Al2O3 catalyst for the DRM process is studied. The catalysts were prepared by wet impregnation method and characterized by Scanning Electron Microscopy (SEM) to study the morphology of the fresh and spent catalyst and Thermogravimetric Analyzer (TGA), which changes in physical and chemical properties of the catalysts are measured as a function of increasing temperature and time. DRM is carried out in a fixed-bed reactor at a temperature range from 600°C to 800°C. Further, the effect of CH4 partial pressure on the conversion of CH4, CO2 and syngas ratio were also investigated. The thermal stability of the catalyst increased on loading with CaO, and CAT-4 (1.5 wt.% CaO, 8.5 wt.% Ni on Al2O3) displayed the optimum activity, stability, and least coke formation.Keywords: Global warming, syngas, catalyst, wet impregnation

Kinetic studies for DRM over high-performance Ni–W/Al2O3–MgO catalyst

The reaction kinetics of DRM over high-performance Ni–W/Al2O3–MgO bimetallic catalyst is investigated in a fixed bed reactor. The variation of reaction rate is examined within the CH4 and CO2 partial pressure from 0.2 to 0.6 atm and the temperature range of 600oC–800 °C. It is found that the rate of reaction for DRM is more sensitive to CH4 partial pressure compared to CO2 partial pressures. At a constant partial pressure of CO2 and increasing the CH4 partial pressure, the increase in the reaction rate is more than reverse conditions. The activation energies of consumption of CH4 and CO2 were found to be 45.9 and 31.9 kJ/mol, respectively, showing a higher energy barrier for CH4 activation than CO2. Four typical kinetic models then fitted the experimental results obtained, i.e., Power Law, Langmuir- Hinshelwood and Eley-Rideal model I and II. The Langmuir-Hinshelwood model showed the best fitting between experimental and estimated reaction rates.