Mixture Of CH4 Research Articles

Investigating adsorption properties of CO2 and CH4 in subbituminous coals from Mamu and Nsukka formations: a molecular simulation approach

The study aimed to investigate the adsorption properties of methane (CH4) and carbon dioxide (CO2) in subbituminous coals from the Mamu and Nsukka formations, focusing on the CO2-Enhanced Coalbed Methane (ECBM) method. Proximate, ultimate, and FT-IR analyses determined the quality, age, and functional categories of these coals, confirming their subbituminous nature. Using molecular dynamics (MD) simulations, a unique amorphous subbituminous coal model was developed to study adsorption phenomena. Isosteric heat and adsorption isotherms for pure CO2 and CH4 were analyzed, alongside Grand Canonical Monte Carlo (GCMC) simulations to assess CO2 adsorption selectivity in a binary CO2 and CH4 mixture. Results showed that CO2 required more isosteric heat than CH4 in single-component scenarios and demonstrated stronger electrostatic interactions with heteroatom groups in the coal model, explaining its higher adsorption preference. In binary adsorption experiments, CO2 exhibited a higher affinity under specific conditions, particularly influenced by pressure variations. At lower pressures, CO2 selectivity decreased rapidly with increasing temperature, while at higher pressures, the influence of temperature diminished. These findings have established a theoretical and practical basis for optimizing CO2-ECBM extraction in Nigeria, highlighting the preferential adsorption of CO2 over CH4 in subbituminous coals from the Mamu and Nsukka formations under varying pressure and temperature conditions. Implementing CO2-ECBM extraction and storage in Nigeria could boost economic viability and help achieve net-zero goals, using insights from this study to guide policy development.Graphical

Simulation Study on Diffusion and Local Structure of CH4, CO2, SO2, and H2O Mixtures into Double-Layers Graphene.

Graphene has been widely studied as an ideal material for the adsorption and separation. In this work, we used molecular dynamics simulations to investigate the evolution of diffusion and local structure of CH4, CO2, SO2, and H2O mixtures into double-layers graphene under seven different interlayer spacings and four different CO2 concentrations. The results showed that the adsorption of CH4 and CO2 molecules on the graphene surface weakened with increased interlayer spacing. The diffusion capacities of CH4 and CO2 in the mixed system were significantly improved by increasing the interlayer spacing. In interlayer spacings ranging from 5 to 10 nm, the diffusion capacities of each component varied significantly in the order CH4 > CO2 ≫ H2O > SO2. Compared with CH4 and CO2, the local structures of SO2 and H2O were more affected by the interlayer spacing. Larger interlayer spacings or higher CO2 concentrations were advantageous for the formation of stronger hydrogen bond structures between H2O molecules. When the CO2 concentrations were between 10% and 20% and the interlayer spacing of graphene was 8 nm, the graphene structure exhibited the best adsorption and separation effects on CH4 and other components.

Amino-Functionalized Metal-Organic Frameworks Featuring Ultra-Strong Ethane Nano-Traps for Efficient C2H6/C2H4 Separation.

Developing high-performance porous materials to separate ethane from ethylene is an important but challenging task in the chemical industry, given their similar sizes and physicochemical properties. Herein, a new type of ultra-strong C2H6 nano-trap, CuIn(3-ain)4 is presented, which utilizes multiple guest-host interactions to efficiently capture C2H6 molecules and separate mixtures of C2H6 and C2H4. The ultra-strong C2H6 nano-trap exhibits the high C2H6 (2.38mmolg-1) uptake at 6.25kPa and 298K and demonstrates a remarkable selectivity of 3.42 for C2H6/C2H4 (10:90). Additionally, equimolar C2H6/C2H4 exhibited a superior high separation potential ∆Q (2286mmolL-1) at 298K. Kinetic adsorption tests demonstrated that CuIn(3-ain)4 has a high adsorption rate for C2H6, establishing it as a new benchmark material for the capture of C2H6 and the separation of C2H6/C2H4. Notably, this exceptional performance is maintained even at a higher temperature of 333K, a phenomenon not observed before. Theoretical simulations and single-crystal X-ray diffraction provide critical insights into how selective adsorption properties can be tuned by manipulating pore dimensions and geometry. The excellent separation performance of CuIn(3-ain)4 has been confirmed through breakthrough experiments for C2H6/C2H4 gas mixtures.

Durable electrocatalysts based on barium niobates doped with Ca, Fe, and Y: Enhancing catalytic activity and selectivity for oxidative coupling of methane

Effective conversion of methane into value added products such as olefins, is a major research area for the past 40 years. Electrochemical oxidative coupling of methane (E-OCM) is recently gaining attention due to its ability to control the product selectivity by oxide ion flux and applied potential. We report a new series of catalysts, Ca, Fe, and Y co-doped barium niobate perovskites (BCNFY) for E-OCM application. BCNFY perovskites show chemical stability under 4 % H2, CH4, and high CH4-O2 mixtures at high temperatures up to 900 °C. Under reducing conditions, BCNFY perovskites form excess oxygen vacancies that is supported by Nb4+/5+ oxidation state changes that help retain the crystal structure. Temperature programmed reaction (TPR) measurements under 95 % CH4:5% O2 reveal methane activation properties from 600 °C with a high C2+ selectivity of 82 % at 850 °C. TPR measurements further reveal the nature of active sites for methane activation. Cyclic voltammetry measurements show a unique relationship between product selectivity and applied potential as at applied biases close to open circuit potential, CO and H2 are the major products while at high applied biases ethylene and CO2 are the major products. Our results show the advantages of E-OCM over conventional OCM although improvements in terms of electronic conductivity of the electrode and overall current densities are required for commercial viability for these perovskite electrodes.

Fluid inclusion and pyrite geochemistry of the Jiapigou gold deposit, North China Craton: Implication for origin of orogenic gold deposit?

The Jiapigou auriferous belt in Jilin province has been recognized as substantial gold-producers in the North China Craton (NCC). Gold mineralization in this district mainly occurs in mineralized quartz veins and alteration zones, characterized by silicification, pyritization, and argillitization. The quartz veins contain three generations of mineralized quartz, namely, qtz1 (probably oldest), qtz2 (slightly younger), and qtz3 (probably youngest) were identified using SEM-CL. The fluid inclusions in all three generations of quartz are broadly of three types, viz., bi-phase Ia (H2O-CO2), tri-phase Ib (H2O-CO2-NaCl ± CH4), and II (H2O-NaCl).The micro-thermometric analysis of the type Ia and Ib fluid inclusion in qtz1 & qtz2 have aqueous-carbonic composition and exhibit a similar salinity of 1.1 to 7.8 wt% NaCl equivalent, whereas the homogenization temperature (Th) range varies from ∼237 to ∼350 °C. These ore-related fluid inclusions are of low to moderate salinity, and show mixture of CO2 and CH4. On the other hand, Type II fluid inclusions are dominant in qtz3. They have salinity of 3.2 to 12.7 wt% NaCl equivalent and homogenization temperature varying between 180 °C and 210 °C. These data indicate that the ore-forming fluid evolved from a CO2–H2O–NaCl ± CH4 system during the mineralization period.The X-ray elemental maps of pyrite acquired using electron microprobe analysis (EPMA) show irregular zones of Co and Ni indicating two generations of pyrite. The early-stage pyrite which occupies core portion shows high Co and Ni, whereas the later-stage pyrite occupying rim has lower Co and Ni. The laser ablation-inductively coupled plasma-mass spectrometer (LA-ICPMS) analyses of pyrite has indicated that pyrite-1 is rich in Au + Ag + Se + Cu + Co + Ni, whereas, pyrite-2 has lower concentration of these elements. A positive correlation between Fe and other chalcophile elements reported here (i.e. Au + Ag + Se + Cu + Co + Ni), might be due to fluid-rock interaction resulting into a saturated fluid that subsequently precipitated along the microfractures within earlier-formed pyrite and quartz. The in-situ δ34S values in pyrite from Jiapigou deposits overlap in the range of +4.5 to +9.6 ‰, which is consistent with the ore-forming fluids of the crustal origin input during fluid-rock interaction. The systematic pyrite compositional observations and fluid inclusions study documented here to provide new insight into the process of ore formation for the Au enrichment in the Jiapigou deposit.

Nitrogen‐Induced Microcrystalline‐to‐Nanocrystalline Structure Transition in Diamond Films Grown by Microwave Plasma Chemical Vapor Deposition: Comparison of N2 and NH3 Precursors

The structure and properties of polycrystalline chemical vapor deposition (CVD) diamond coatings grown by microwave plasma CVD in H2–CH4 mixtures can be effectively controlled by nitrogen admixture in the process gas. Here, a comparative study of adding nitrogen from different precursors, N2 and ammonia NH3, in concentrations up to 0.4%vol on grain size, texture, surface roughness, and sp2/sp3 ratio of the produced films on Si substrates is performed. A transition from microcrystalline to smooth nanocrystalline diamond structure is found to occur at a certain concentration of the precursor, for NH3 this threshold concentration being much lower, 0.02–0.1%, than for N2. The higher activity of ammonia is associated with easier formation of cyano radicals in the plasma as detected with optical emission spectroscopy, in accord with the lower bond‐dissociation energy for NH3 compared to N2. On the contrary, a smaller addition (0.004%) of either N2 or NH3 promotes almost doubling of the growth rate, while preserving the microcrystalline structure of the film. The results establish ammonia as a convenient alternative precursor to commonly used N2 added in the plasma for the diamond film structure modifications.

Binary Adsorption Equilibria of Three CO2+CH4 Mixtures on NIST Reference Zeolite Y (RM 8850) at Temperatures from 298 to 353 K and Pressures up to 3 MPa.

Adsorption equilibria of CO2, CH4, and their mixtures were measured on binderless pellets of NIST reference zeolite NaY (RM 8850) using a static gravimetric setup. The unary adsorption isotherms are reported at temperatures from 298 to 393 K up to a pressure of 3 MPa and compare favorably with independent results on RM 8850 powder. The competitive adsorption measurements were performed at temperatures from 298 to 353 K and up to 3 MPa for three premixed gas mixtures with CO2 molar feed compositions of 0.25, 0.50, and 0.75. The results constitute the first competitive adsorption dataset reported for any of the NIST reference materials. RM 8850 shows a strong selectivity for CO2 adsorption toward CH4. The experimental unary and binary adsorption isotherms are accurately modeled using the simplified statistical isotherm model (SSI). Notably, the agreement with the model improves only slightly (and within experimental uncertainties) when the whole dataset is used for parameter fitting as opposed to only using the unary data.

Preparation of highly graphitized porous carbon and its ethane/ethylene separation performance

The efficient separation of ethane (C2H6) and ethylene (C2H4) is crucial for the preparation of polymer-grade C2H4, necessitating the development of highly selective and stable C2H6/C2H4 adsorbents. Highly graphitized porous carbon, denoted GC-800, was synthesized by polymerization at room temperature followed by carbonization at 800 °C using phenolic resin as the precursor and FeCl3 as the iron source. Vienna Ab-initio Simulation Package (VASP) calculations confirmed a higher binding energy between C2H6 molecules and graphitized porous carbon surfaces, so that a high degree of graphitization increased the adsorption capacity of porous carbon for C2H6. However, catalytic graphitization using Fe at high temperatures disrupted the microporous structure of the carbon, thereby reducing its ability to separate C2H6/C2H4. By controlling the carbonization temperature, the degree of graphitization and pore structure of the porous carbon could be changed. Raman spectra and XPS spectra showed that the GC-800 had a high degree of graphitization, with a sp2 C content as high as 73%. Low-temperature N2 physical adsorption measurements estimated the specific surface area of GC-800 to be as high as 574 m2·g−1. At 298 K and 1 bar, it had an equilibrium adsorption capacity of 2.16 mmol·g−1 for C2H6, with the C2H6/C2H4 (1:1 and 1:9, v/v) ideal adsorbed solution theory selectivity respectively reaching 2.4 and 3.8, significantly higher than the values of most reported high-performance C2H6 selective adsorbents. Dynamic breakthrough experiments showed that GC-800 could produce high-purity C2H4 in a single step from a mixture of C2H6 and C2H4. Dynamic cycling tests confirmed its good cyclic stability, and that it could efficiently separate C2H6/C2H4 even under humid conditions.

Environmentally friendly production of petroleum systems with high CO2 content

Natural gas hydrates represents a huge source of energy. At the same time substantial leakages of natural gas from hydrates contributes significantly to climate changes. One of the most important reasons for these natural gas fluxes is leakage of seawater in to the hydrates from seafloor, through fracture systems. Hydrate dissociates if surrounding seawater is less than hydrate stability limit. Another interesting aspect of natural gas hydrates is the potential for safe CO2 storage. These different aspects of hydrates in natural sediments put demands on thermodynamic models. In addition to accurate description of pressure temperature hydrate stability there also a need to describe hydrate dissociation in concentration gradients towards surrounding water or surrounding gas as two examples. In this work we present new experimental data and an extensive thermodynamic model for hydrate. In contrast to conventional thermodynamic models for hydrate the model is consistent since all thermodynamic properties are derived from the Gibbs free energy. In this work we examine mixtures of CH4, C2H6, N2, CO2 from the China Sea and some synthetic mixtures, using this model. Maximum CO2 content in these mixtures are 60 mol% and the rest is dominated by CH4. Agreement between experimental data and model calculations are generally good and average deviations are below 5.5% for all the systems and conditions examined. Another aspect of the model is the ability for incorporation of effects of mineral surfaces. Specifically it is illustrated that adsorption of water on rust dominates liquid water drop out from gas as compared to water dew-point. Production of natural gas with such high CO2 content requires a strategy for CO2 separation and storage. It is proposed that the CH4 is separated from the C2H6, CO2 and N2 and cracked to H2 and CO2 using steam. Thermodynamic analysis indicates a significant potential for safe CO2 storage in natural gas hydrate and H2 as the only export product.

Enhanced Solubility and Miscibility of CO2-Oil Mixture in the Presence of Propane under Reservoir Conditions to Improve Recovery Efficiency

The existence of propane (C3H8) in a CO2-oil mixture has great potential for increasing CO2 solubility and decreasing minimum miscibility pressure (MMP). In this study, the enhanced solubility, reduced viscosity, and lowered MMP of CO2-saturated crude oil in the presence of various amounts of C3H8 have been systematically examined at the reservoir conditions. Experimentally, a piston-equipped pressure/volume/temperature (PVT) cell is first validated by accurately reproducing the bubble-point pressures of the pure component of C3H8 at temperatures of 30, 40, and 50 °C with both continuous and stepwise depressurization methods. The validated cell is well utilized to measure the saturation pressures of the CO2-C3H8-oil systems by identifying the turning point on a P-V diagram at a given temperature. Accordingly, the gas solubilities of a CO2, C3H8, and CO2-C3H8 mixture in crude oil at pressures up to 1600 psi and a temperature range of 25–50 °C are measured. In addition, the viscosity of gas-saturated crude oil in a single liquid phase is measured using an in-line viscometer, where the pressure is maintained to be higher than its saturation pressure. Theoretically, a modified Peng–Robinson equation of state (PR EOS) is utilized as the primary thermodynamic model in this work. The crude oil is characterized as both a single and multiple pseudo-component(s). An exponential distribution function, together with a logarithm-type lumping method, is applied to characterize the crude oil. Two linear binary interaction parameters (BIP) correlations have been developed for CO2-oil binaries and C3H8-oil binaries to accurately reproduce the measured saturation pressures. Moreover, the MMPs of the CO2-oil mixture in the presence and absence of C3H8 have been determined with the assistance of the tie-line method. It has been found that the developed mathematical model can accurately calculate the saturation pressures of C3H8 and/or CO2-oil systems with an absolute average relative deviation (AARD) of 2.39% for 12 feed experiments. Compared to CO2, it is demonstrated that C3H8 is more soluble in the crude oil at the given pressure and temperature. The viscosity of gas-saturated crude oil can decrease from 9.50 cP to 1.89 cP and the averaged MMP from 1490 psi to 1160 psi at 50 °C with the addition of an average 16.02 mol% C3H8 in the CO2-oil mixture.

Morphology-Dependent Chemiresistive-Potentiometric Gas Sensing Properties of ZnO Nanorods for CH4 and CO

In this study, one-dimensional ZnO nanorods sensing electrodes were grown in situ on the surface of the Ce0.8Gd0.2O1.9 electrolyte to fabricate chemiresistive-potentiometric (C-P) bivariate sensors for the detection and identification of CH4 and CO. Four C-P sensors were developed by adjusting the hydrothermal growth time of the nanorods. The effect of hydrothermal duration on the morphology of nanorods was examined. The C-P response to CH4 and CO initially increased and then decreased with increasing hydrothermal duration. Similar variations in the response to the gas mixtures of CH4 and CO with the hydrothermal duration were observed. The highest C and P response values for CH4, CO, and their mixtures were obtained at a hydrothermal duration of 1.5 h. The enhanced C-P sensing performance was discussed in terms of the defect density, the number of contact junctions, and the length of ZnO nanorods. Accurate differentiation of five different gases (CH4, CO, and three gas mixtures) with an identification accuracy of 100% was achieved by the array assembled with the ZnO-1.0 and the ZnO-1.5 sensors. Our findings demonstrate the morphology-dependent C-P sensing behaviors of ZnO nanorods and provide a facile and cost-effective method for the detection and identification of CH4 and CO.

Performance and Enhanced Efficiency Induced by Cold Plasma on SAPO-34 Membranes for CO2 and CH4 Mixtures.

In this study, we investigate the influence of cold-plasma-induced enhanced performance and efficiency of SAPO-34 membranes in the separation of CO2 and CH4 mixtures. Placing the herein presented research in a broader context, we aim to address the question of whether cold plasma can significantly impact the membrane performance. We subjected SAPO-34 membranes to plasma mild disturbances and analyzed their performance in separating CO2 and CH4. Our findings reveal a notable enhancement in membrane efficiency and sustained performance when exposed to cold plasma. The pulsed plasma separation displayed improved structural integrity, and the experimental results indicated that the linear structure of CO₂ facilitates the distortion of electron clouds in response to the electric field, a property known as polarizability, which aids in effective separation. Plausible mechanistic insight indicated that the intermolecular forces facilitated an integral role in SAPO-34 membranes exhibiting strong electrostatic interactions. In conclusion, our research highlights the potential of cold plasma as a promising technique for improving the performance of SAPO-34 membranes in gas mixtures at atmospheric pressures, providing valuable insights for optimizing membrane technology in carbon capture and gas separation applications.

A PLC-Embedded Implementation of a Modified Takagi–Sugeno–Kang-Based MPC to Control a Pressure Swing Adsorption Process

The paper presents a case study that applies a model predictive control (MPC) approach in a Micro850 programmable logic controller (PLC) to a laboratory pressure swing adsorption (PSA) process used for separating gas mixtures of CO2 and CH4. PLC is an industrial hardware characterized by its robustness to hazardous environments and limited computational capacities, which poses computational challenges for MPC implementation. This paper’s main contribution is the application of the modified Takagi–Sugeno–Kang-based MPC (MTSK-MPC) algorithm to this PSA unit, which provides features to investigate and implement feasible MPC designs in PLCs. The investigation consists of a sensitivity analysis of how some design parameters influence the PLC memory and the MPC implementation and a comparative evaluation of the computational processing from different MPC algorithms and simulations. The comparison comprises software-in-the-loop simulations with three algorithms in the PC: an implicit MPC, an explicit MPC, and the MTSK-MPC. Additionally, it includes a hardware-in-the-loop simulation with the implemented MTSK-MPC in Micro850. The results show that the MPC algorithms achieve close performance, tracking setpoint changes and rejecting output disturbances, with the MTSK-MPC presenting the lower processing time among the MPCs in the PC. The study concludes that the implementation of MTSK-MPC in the Micro850 is feasible.

Experimental study and thermodynamic modeling of CO2+CH4 gas mixture hydrate phase equilibria for gas separation efficiency

Gas separation is a critical application of gas hydrates, and accurately predicting separation performance is crucial. In this study, we used thermodynamic calculations to predict the equilibrium phase of gas hydrates for various mole fractions of CO2 + CH4 gas mixtures. We also determined the mole fraction of each gas component trapped within the hydrate clathrate. To predict the equilibrium points, we used the Soave–Redlich–Kwong（(SRK) equation of state for the gas phase, the nonrandom two-liquid (NRTL)model for the liquid phase, and the Chen–Guo model for the hydrate phase. We modified the hydrate fugacity formula and introduced a new function to improve the accuracy of the Chen–Guo model. By incorporating experimental equilibrium results from our study and another study, we developed a correlation based on gas mixture composition and temperature, resulting in highly accurate predictions. The use of this new correlation for hydrate fugacity calculation significantly improved precision, as evidenced by an average absolute deviation percent of calculated pressures (AADP) of 1.34% for pure CO2 and 1.25% for CH4. When considering the 27 data points of different CO2 + CH4 mixtures, the AADP% was 1.98%.To implement the model to predict equilibrium phases, we used the Chen–Guo framework to determine the mole fraction of each gas component in the hydrate mixture. Interestingly, we discovered a linear correlation between the CO2 mole fraction in the hydrate and equilibrium pressure, with a slope of approximately 0.001 and a y-intercept of less than one, for all gas compositions. Therefore, we can conclude that low thermodynamic conditions (temperature and pressure) result in a high CO2 mole fraction in the hydrate phase and great separation efficiency.

Effects of buoyancy on the spherical flame and explosion pressure of a CH4 mixture under dilution conditions

To determine the effects of buoyancy on the spherical flame and explosion pressure under dilution conditions, a series of explosion experiments were conducted in a 20-L spherical container. The schlieren technique was used to record CH4 flames to assess the buoyancy effect. The change in the explosion pressure was recorded and correlated with the flame shape to analyze the explosion characteristics. The methane explosion occurred in two stages: initial ignition and flame development. During initial ignition, the addition of CO2 caused the flame buoyancy to increase considerably. Flames with different buoyancies had different shapes, such as spherical, ellipsoidal, and “ω” shapes. The radius of the flame at 12 mm may serve as the threshold for the onset of buoyancy effects; once the radius exceeds this value, the flame could deform due to buoyancy effects. Increasing the added CO2 concentration caused the buoyancy effect to be enhanced and appear at a very low radius of the flame. The combined effects of buoyancy and dilution reduced the flame expansion speed. The difference between the horizontal and upward expansion speeds linearly increased with the CO2 concentration. At a high CO2 concentration, the flame stagnated at speeds below 0.5 m/s. During flame development, CO2 addition made the flame surface smoother. Suppressing the cellular flame structure delayed the maximum explosion pressure rise rate and reduced the pressure peak. A coupled analysis of the flame shape and the maximum explosion pressure rise rate showed a dense cellular structure for a high explosion pressure rise rate and a smooth flame surface for a low maximum explosion pressure rise rate. The size and number of cellular structures for different mixtures were similar at a fixed maximum explosion pressure rise rate.

Optimizing methane plasma pyrolysis for instant hydrogen and high-quality carbon production

The European Green Deal has set a target for Europe to achieve net-zero greenhouse gas emissions by 2050, necessitating a transition to more sustainable energy sources. Hydrogen gas (H2) has emerged as a promising solution, with methane pyrolysis presenting a viable method for its production. This study explores the optimization of methane plasma pyrolysis for hydrogen and high-quality carbon production. Employing a statistical approach by a design of experiment software, critical process parameters are systematically analyzed to predict their impact within a defined range. Additionally, the paper conducts comprehensive characterization of the solid carbon produced during pyrolysis using imaging, spectroscopic and elemental analysis, and gas sorption analysis methods. The experimental investigation was conducted using a thermal plasma reactor with several settings of influential parameters including methane gas (CH4) content in the plasma gas, electric current, and arc length. The DC-transferred plasma arc is formed using a variable gas mixture of argon gas (Ar) and CH4, with a constant flow rate of 5 Nl/min. Thirteen tests were designed, evaluating responses such as power input, process stability, and H2 yield. The H2 yield indicates the hydrogen produced from CH4, with 100% representing total conversion. While the process exhibited inconstancy, attributed to reactor design constraints, a high H2 yield of 67%–100% was achieved. The results indicate that a higher CH4 content in the plasma gas and extended arc lengths disturb the plasma arc, hence reducing the H2 yield. Increased power input, achieved through higher amperage levels, and a wider reaction zone eased by extending the arc length both led to an improved H2 yield. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) revealed microstructural differences, with carbon samples from the filter exhibiting finer textures and carbon samples from the reactor larger sizes and dendritic particles. Raman spectroscopy confirmed crystalline graphitic-like structures with low defect concentrations, a finding supported by X-ray diffraction (XRD) analysis. Inductively coupled plasma mass spectroscopy (ICP-MS) analysis confirmed high-purity carbon with slight impurities from initial filter contamination. Brunauer-Emmett-Teller (BET) specific surface area calculations based on gas sorption analysis showed significant variations, with filter-collected samples exhibiting 40–170 m2/g and reactor-collected ones showing 7–30 m2/g.

Electrostatically driven kinetic inverse CO2/C2H2 separation in LTA-type zeolites

The identical molecular size and similar physical properties of carbon dioxide (CO2) and acetylene (C2H2) make their adsorptive separation extremely challenging to achieve with most adsorbents. Reports on the separation of CO2 and C2H2 mixtures by zeolites are even rarer with the mechanism of adsorptive separation requiring further exploration. In this paper, we report that ion modulation of zeolite 5A promotes the difference in kinetic diffusion of CO2 and C2H2, realizing the inverse separation of zeolite from selective adsorption of C2H2 to selective adsorption of CO2. Creating a compact pore space restricting the orientation of gas molecules enables charge recognition. The positive electrostatic potential at the pore openings was utilized to hinder the diffusion of C2H2 between the cages while ensuring the transfer of CO2, increasing their diffusion differences in pore channels and leading to the CO2/C2H2 kinetic selectivity of 31.97. Grand canonical Monte Carlo (GCMC) simulation demonstrates that the CO2 distribution in K-5A-β is significantly higher than that of C2H2. Dynamic breakthrough experiments verify the excellent performance of material in practical CO2/C2H2 separation, for CO2/C2H2 (50/50 and 1/99, V/V) mixtures can be separated in one step, thus directly generating high purity C2H2 (> 99.95%), which provides a promising thought for the zeolite-based separation of CO2 and C2H2.

Novel superhard BC10N synthesized by microwave plasma CVD

Microwave Plasma Chemical Vapor Deposition (MPCVD) was used to synthesize novel superhard BC10N on silicon substrates. Feedgas mixtures of H2, CH4, N2, and B2H6 were used for a range of systematically varied microwave power, chamber pressure, and flow rate conditions. Optical Emission Spectroscopy (OES) was used to guide the synthesis of BC10N. Plasma optical emission from the C2 peak increases with pressure up to 80 Torr and saturates in the 80–100 Torr range. The C2 emission also follows the same trend, growing non-linearly with increasing microwave power (for fixed chamber pressure of 30 Torr). The presence of abundant C2 in the plasma is advantageous under specific growth conditions to produce superhard carbon-rich BC10N, a material that has been theoretically predicted but not yet synthesized. Findings obtained from X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) elucidate the existence of BC, CN, BN, and B-N-C bonding in the synthesized coating. Nanoindentation hardness measurements are within the superhard regime, showing an average hardness of 63 GPa.

Microwave plasma-assisted hydrogen production via conversion of CO2–CH4 mixture

A method concerning re-use of the main greenhouse gases: CO2 and CH4 at the same time producing value-added chemicals (H2 + CO) is presented in this paper. The method involves the methane dry reforming using an atmospheric pressure operated 915 MHz microwave plasma source with a swirl gas flow. The effect of the CO2 to CH4 flow rates ratio, the total gas flow rate and the absorbed microwave power on the volume concentration of the gaseous plasma component in the outlet gas (%), CO2 and CH4 conversion rate (%), hydrogen production rate (g h−1) and energy yield of hydrogen production (g kWh−1) was investigated experimentally. The recorded results of the CO2 and CH4 conversion rate were about 82% and 88%, respectively. The best results in terms of the hydrogen production rate and energy yield of hydrogen production were equal to 156 g h−1 and 24 g kWh−1, respectively.

Retrofitting Natural Gas–Fired Boiler for Hydrogen Combustion: Operational Performance and NOx Emissions

Abstract The effects of hydrogen fraction (HF: volumetric fraction of H2 in the fuel mixture of CH4 + H2) from 0% to 100% by volume, on the thermal and environmental performance of a 207-MW industrial water tube boiler, are investigated numerically at a fixed excess air factor, λ = 1.15. This study aims to determine the hardware modifications required for boilers to be retrofitted for pure hydrogen operation and investigates how NOx emissions are affected by hydrogen enrichment. The results showed insignificant increases in maximum combustion temperature with increasing the HF, though the distributions of temperature profiles are distinct. In reference to the basic methane combustion, H2 flames resulted in a positive temperature rise in the vicinity of the burner. Increasing the HF from 0% to 2% resulted in higher average thermal NOx emissions at the boiler exit section from 37 up to 1284 ppm, then it decreased to 1136 ppm at HF = 30%, and later it leveled up to 1474 ppm at HF = 100%. The spots for higher differences in NO formation compared to the reference case are shifted downstream at higher HFs. The effect of hydrogen enrichment on CO2 and H2O as radiation sources, as well as the volumetric absorption radiation of the furnace wall and the heat flux at furnace surfaces, has all been presented in relation to the effect of hydrogen addition on boiler performance.