Methane Formation Research Articles

WHAT IS THE MAXIMAL POSSIBLE SOIL METHANE UPTAKE?

WHAT IS THE MAXIMAL POSSIBLE SOIL METHANE UPTAKE?

The Promoting Role of Ni on In2O3 for CO2 Hydrogenation to Methanol.

Ni-promoted indium oxide (In2O3) is a promising catalyst for the selective hydrogenation of CO2 to CH3OH, but the nature of the active Ni sites remains unknown. By employing density functional theory and microkinetic modeling, we elucidate the promoting role of Ni in In2O3-catalyzed CO2 hydrogenation. Three representative models have been investigated: (i) a single Ni atom doped in the In2O3(111) surface, (ii) a Ni atom adsorbed on In2O3(111), and (iii) a small cluster of eight Ni atoms adsorbed on In2O3(111). Genetic algorithms (GAs) are used to identify the optimum structure of the Ni8 clusters on the In2O3 surface. Compared to the pristine In2O3(111) surface, the Ni8-cluster model offers a lower overall barrier to oxygen vacancy formation, whereas, on both single-atom models, higher overall barriers are found. Microkinetic simulations reveal that only the supported Ni8 cluster can lead to high methanol selectivity, whereas single Ni atoms either doped in or adsorbed on the In2O3 surface mainly catalyze CO formation. Hydride species obtained by facile H2 dissociation on the Ni8 cluster are involved in the hydrogenation of adsorbed CO2 to formate intermediates and methanol. At higher temperatures, the decreasing hydride coverage shifts the selectivity to CO. On the Ni8-cluster model, the formation of methane is inhibited by high barriers associated with either direct or H-assisted CO activation. A comparison with a smaller Ni6 cluster also obtained with GAs exhibits similar barriers for key rate-limiting steps for the formation of CO, CH4, and CH3OH. Further microkinetic simulations show that this model also has appreciable selectivity to methanol at low temperatures. The formation of CO over single Ni atoms either doped in or adsorbed on the In2O3 surface takes place via a redox pathway involving the formation of oxygen vacancies and direct CO2 dissociation.

Gas Diffusion Characteristics and Size Effect in Coal Particles with Different Degrees of Metamorphism

Coalbed methane (CBM) is a green unconventional energy source where the gas diffusion efficiency in coal directly limits the production capacity. Therefore, different gas adsorption experiments were used to determine the diffusion characteristics of coal samples with varying degrees of metamorphism. The influence law based on the gas type, pore structure, and coal sample size on the gas diffusion coefficient was analyzed, and the synergistic control effect of various factors on diffusion was discussed. The results show that when the particle size is the same, the diffusion coefficient of different gases shows the change rule of CO2 > N2 > CH4, and the diffusion coefficient of different samples is positively correlated with the degree of pore development. When the particle size is different, the diffusion coefficient is negatively correlated with the pore development degree and positively correlated with the sample particle size. The effective diffusion coefficient is consistent with the diffusion coefficient when the particle size of the sample is the same, and the effective diffusion coefficient is opposite to the diffusion coefficient when the particle size decreases. The analysis reveals that the diffusion coefficients of different gas are limited by the diameter of gas molecular dynamics, and the diffusion coefficient is reduced with the decrease in the diameter of the gas molecular dynamics. The change of diffusion coefficient caused by particle size change is positively correlated with the change of diffusion cross section caused by size effect. The difference between the effective diffusion coefficient and the diffusion coefficient mainly comes from whether the effective diffusion path is calculated. Therefore, when the particle size is constant, the effective diffusion coefficient can replace the diffusion coefficient to characterize the diffusion behavior. When the particle size is different, it is more appropriate to use the diffusion coefficient to characterize the gas diffusion behavior. The significance of the research findings in revealing gas transport in the coal matrix and coalbed methane formation is substantial.

Redox Behavior of In−O−Ti Interface for Selective Hydrogenation of CO2 to CO in Doped In−TiO2 Catalyst

AbstractIn the CO2 hydrogenation reaction, selective synthesis of CO at low temperature and high pressure is needed to integrate the reverse water gas shift reaction with Fischer‐Tropsch synthesis. Here, we show that a mixed oxide catalyst prepared by doping indium (In) into TiO2 produces CO with the formation rate of 22 μmol g−1 s−1. The CO selectivity was more than 99 % at 350 °C and 3 MPa pressure. Moreover, the catalyst was durable for over 100 h on stream. During reaction the interfacial In3+−O−Ti4+ sites were first reduced in presence of H2 and then oxidized back with CO2 producing CO. Because of the redox mechanism, the formation of methanol and methane was limited. This study shows the development of a promoter‐free oxide catalyst for CO2 hydrogenation and the importance of the redox property at the oxide interface for selective hydrogenation of CO2 to CO under unfavorable conditions.

Enhanced carbon emission driven by the interaction between functional microbial community and hydrocarbons: An enlightenment for carbon cycle

Soil microbial communities are usually regarded as one of the key players in the global element cycling. Moreover, an important consequence of oil contamination altering the structure of microbial communities is likely to result in an increased carbon emission. However, understanding of the complex interactions between environmental factors and biological communities is clearly lagging behind. Here it showed that the flux of carbon emissions increased in oil-contaminated soils, up to 13.64 g C·(kg soil)−1·h−1. This phenomenon was mainly driven by the enrichment of rare degrading microorganisms (e.g., Methylosinus, Marinobacter, Pseudomonas, Alcanivorax, Yeosuana, Halomonas and Microbulbifer) in the aerobic layer, rather than the anaerobic layer, which is more conducive to methane formation. In addition, petroleum hydrocarbons and environmental factors are equally important in shaping the structure of microbial communities (the ecological stability) and functional traits (e.g., fatty acid metabolism, lipid metabolism and amino acid metabolism) due to the different ecological sensitivities of microorganisms. Thus, it can be believed that the variability of rare hydrocarbon degrading microorganisms is of greater concern than changes in dominant microorganisms in oil-contaminated soil. Undoubtedly, this study could reveal the unique characterization of bacterial communities that mediate carbon emission and provide evidence for understanding the conversion from carbon stores to carbon gas release in oil-contaminated soils.

Feasibility of successive hydrogen and methane production in a single-reactor configuration of batch anaerobic digestion through bioaugmentation and stimulation of hydrogenase activity and direct interspecies electron transfer

Two-stage anaerobic digestion is a promising way to increase the efficiency of decomposition of organic waste. However, spatial separation of stages makes this technology less economically attractive. In this work, we studied a model of two-stage anaerobic digestion with stages separated in time in one reactor. To implement this model, we used a combination of (1) bioaugmentation with a hydrogen-producing Thermoanaerobacterium thermosaccharolyticum SP-H2, resistant to low pH, (2) setting a low initial pH (5.5) to reduce the activity of hydrogenotrophic methanogens, (3) supplementing additives in the form of soluble iron (II) and granular activated carbon (GAC) to stimulate hydrogenase activity and direct interspecies electron transfer (DIET), respectively. For comparison, two methanogenic inoculums with different dominant microbial groups and initial iron concentrations were used. With the simultaneous addition of GAC and iron (II), sequential production of hydrogen and methane was observed for both methanogenic inoculums. Without the addition of GAC, methane formation was practically not observed, which, apparently, indicated the impossibility of syntrophic degradation of acidogenesis products due to the high partial pressure of hydrogen and the absence of conductive material for activation of DIET. Significant differences in hydrogenase activity and the kinetics of hydrogen and methane formation according to the modified Gompertz equation depending on the iron content in the system may indicate the importance of this additive. Further studies should be aimed at determining the optimal initial pH, concentrations of stimulating additives, bioaugmentation and methanogenic cultures, as well as confirming the stability of the proposed single-reactor two-stage anaerobic digestion system in semi-continuous mode.

Feedstock flexible numerical analysis of sewage sludge gasification

Sewage sludge properties vary with the origin and treatment method of the wastewater. When converting the sewage sludge thermally for material and energy recovery, these properties affect the composition of the products and the efficiency of the process. Rotary kiln gasifiers can handle these variations in the raw materials. For further development, process integration, optimization of the process, upscaling, and industrial application, it is helpful to understand and describe the impact of the sewage sludge properties on operating parameters and product quality. This work analyses the impact of sewage sludge properties numerically using detailed chemistry and the surrogate approach. Sewage sludge is described using woody biomass components, sugars, lipids, proteins, inorganic species, moisture, and ash. The stochastic reactor model (SRM) is used to model the gasification process. In contrast to ideal reactors, stochastic reactors allow for resolving inhomogeneity. Hence, the predicted gas composition results from local temperature and available oxygen. For the analysis, temperature, airflow rate, and fuel properties, i.e., the amount and composition of volatiles, including fuel-bonded nitrogen and sulfur, and the moisture level are varied. Their results are analysed regarding the produced gas composition, emission precursor formation, and cold gas efficiency of the process. The highest efficiencies are found for temperatures of 1223 K and rich conditions. High concentrations of methane and hydrogen accompany this maximum. However, the producer gas’s highest heating value is found at low temperatures thanks to the presence of small hydrocarbons. Furthermore, a high volatile amount and a dry feedstock favour methane and carbon monoxide formation. The hydrogen concentration is found to be sensitive to the moisture content and is the highest at 30%. The cold gas efficiency is predicted to depend strongly on the feedstock and varies for the same operating conditions up to 60%. With increasing fuel-bonded nitrogen and sulfur content, the concentrations of NO and SO2 formation and their precursors increase, respectively. The released ammonia leads to significantly reducing emitted NO through the ThermalDeNOx mechanism. Overall, the generated maps provide a detailed insight in species formation and allows for the prediction of process parameters sensitive to the sewage sludge properties.

Improving the hydrothermal stability and hydrogen selectivity of Ni-Cu based catalysts for the aqueous-phase reforming of methanol

Non-precious metal catalysts suitable for hydrogen production via aqueous phase reforming (APR) of methanol show important technical and commercial value in the development of distributed, small/micro-scale on-site hydrogen production systems. They still face the challenges of reduced activity and stability due to sintering and oxidation of active metal nanoparticles, change of the surface state and collapse of the pore structure of used supports under hydrothermal conditions. To solve these problems, a series of ZnO/Ni-xCu/Al2O3 (x = 0, 2, 4, 6, 8, 10) catalysts were prepared by a simple impregnation method in this work. The addition of Cu improved the reducibility of NiO, and promoted the formation of smaller and more dispersed metal particles on the surface of Al2O3, facilitating hydrogen production and hindering methane formation. Among them, the highest average hydrogen production rate (362.1 μmol‧min−1‧gcat−1) and the highest hydrogen selectivity (99%) were reached using ZnO/Ni-8Cu/Al2O3 catalyst, which were 1.6 times and 20.7% higher than those obtained on the mono-metallic ZnO/Ni/Al2O3 catalyst, respectively. On the other hand, the modification of Ni-8Cu/Al2O3 with ZnO prevented effectively the reaction of surface water with Al2O3 and inhibited the formation of boehmite phase, leading to dramatical improvement of its stability during APR of methanol with a prolonged lifetime (72 h) by 6 times. This new developed ZnO/Ni-xCu/Al2O3 catalysts offer great potential for the development of commercial catalysts to produce hydrogen from APR of methanol.

Изучение процессов образования гидрата природного газа в пористой среде из смеси растворов полимеров с нефтью

The article presents the results of studies of equilibrium conditions and kinetic characteristics of the processes of formation of natural gas hydrate in systems of porous medium - water - polymer - calcium chloride - oil under static conditions. It has been established that, formation of methane and natural gas hydrates mixture occurs in the systems under study. The presence of oil in the reaction system does not affect the equilibrium conditions of the gas hydrates formation within the error but reduces the hydrate formation rateand water-to hydrate convertion. The presence of the CaCl2 salt in the system shifts the equilibrium conditions of hydrate formationto the region of low temperatures. The effect of calcium chloride on the kinetics in a system without polymers has an extreme dependenceand makes it possible to double the gas uptake rate at 50 g/L. The addition of polymers (polyacrylamide, sodium carboxymethyl cellulose, or polyethylene glycol) to the system suppresses the salt effect. The data obtained can be useful in the developmentof reagents for polymer flooding of an oil reservoir during oil production under conditions of gas hydrate stability.

Methanobrevibacter boviskoreani JH1T growth on alcohols allows development of a high throughput bioassay to detect methanogen inhibition

Rumen methanogenic archaea use by-products of fermentation to carry out methanogenesis for energy generation. A key fermentation by-product is hydrogen (H2), which acts as the source of reducing potential for methane (CH4) formation in hydrogenotrophic methanogens. The in vitro cultivation of hydrogenotrophic rumen methanogens requires pressurised H2 which limits the ability to conduct high-throughput screening experiments with these organisms. The genome of the hydrogenotrophic methanogen Methanobrevibacter boviskoreani JH1T harbors genes encoding an NADP-dependent alcohol dehydrogenase and a F420-dependent NADP reductase, which may facilitate the transfer of reducing potential from ethanol to F420 via NADP. The aim of this study was to explore the anaerobic culturing of JH1T without pressurised H2, using a variety of short chain alcohols. The results demonstrate that in the absence of H2, JHIT can use ethanol, 1-propanol, and 1-butanol but not methanol, as a source of reducing potential for methanogenesis. The ability to use ethanol to drive CH4 formation in JH1T makes it possible to develop a high throughput culture-based bioassay enabling screening of potential anti-methanogen compounds. The development of this resource will help researchers globally to accelerate the search for methane mitigation technologies for ruminant animals. Global emissions pathways that are consistent with the temperature goal of the Paris Agreement, rely on substantial reductions of agricultural greenhouse gasses, particularly from ruminant animals.

HOW THE LOWERING OF PRESSURE OR THE FORMATION OF ICE AFFECT THE FORMATION AND DISSOCIATION OF METHANE HYDRATES: VARIATIONS IN TERMS OF METASTABLE PHASE AND ANOMALOUS SELF-PRESERVATION

This research proposes the multiple and consecutive formation of methane hydrates with the same gas-water mixture and in a small-scale reactor. The scope consisted of better exploring how the variation of the initial pressure of the system modified the formation and dissociation processes. One of the most promising solutions for gas hydrates exploitation consists in the replacement of methane with carbon dioxide. This process inevitably requires the formation of CO<sub>2</sub> hydrates; thus, more details and analyses on the driving forces of the formation process are required in order to improve the overall replacement efficiency. Also, the competition with ice was analyzed. Nine tests were carried out in order to consider all these parameters. Each test was characterized thermodynamically and the time required to complete each specific phase of the process was measured. The tests were carried out at two different initial pressures: 60 and 50 bar, respectively. It was found that the main effect, associated with a lower initial pressure and/or with the presence of ice, is the stretching of the so-called metastable phase; since the local conditions became suitable for the formation of hydrates, the system required more time to begin in these latter cases. In the tests made at 60 bar, the delay in hydrate formation related to the metastable phase was equal to 0.73-1.04 h, while it ranged from 7.29 to 15.16 h in the tests made at 50 bar. Moreover, the results proved that the presence of ice hindered the formation process by reducing the heat transfer rate and by lowering the volume available for the process. Conversely, the begin of the dissociation phase was similar in all the experiments: the anomalous self-preservation, or the capability of the system to preserve itself even outside the hydrate stability zone was not observed, proving again that these limiting factors (lower initial pressure and ice formation) mainly affected the process during the formation phase.

Methane gas hydrates of the Black Sea – environmental problem or energy source?

Purpose. The purpose of this paper is to substantiate the technological solution of equilibrium conditions in the system “methane – water phase – hydrate – R-2M”; to reveal existing ecological problems of methane gas hydrate extraction from the Black Sea bottom; to determine whether gas hydrate deposits of Black Sea methane are an ecological problem or should be considered as an energy source, to explain the necessity of introduction of the effect of forced self-preservation of methane gas hydrates into development of gas hydrates from the sea bottom.
 Results. This article analyses current research on gas hydrates specifically in the Black Sea. It shows that the necessary conditions exist for the accumulation of gas hydrates in certain areas of the deep Black Sea (one of the most favourable regions among modern sea basins). This article discusses some ideas for the development of experimental studies of the metastable state of methane gas hydrates at negative temperatures: stability and mechanisms of decomposition. Despite the great variety of technological solutions and schemes of gas hydrates application proposed by the leading researchers in the world, they have been tested practically on a small number of laboratory and model installations, mainly for water desalination and concentration of water solutions, separation of two-component gas mixtures. In fact, there is no data to calculate the processes of formation and melting of ice-gas hydrate methane. The effect of self-preservation of methane gas hydrates deserves special attention.
 Scientific novelty. An attempt was made to substantiate the issue of whether gas hydrate deposits of methane in the Black Sea are an environmental problem or should they be considered as an additional source of energy and even as a “fuel of the future”. The authors for the first time introduced the concept of “forced preservation (activation) effect of methane gas hydrates”, which makes it possible to stabilize methane hydrate decomposition when the system is transferred from the area of hydrate stability to the area of thermodynamic parameters, thus significantly reducing the environmental problems of the Black Sea.
 Practical value. This article offers a technological solution for stabilization of equilibrium conditions by hydrophobic material “Ramsinks-2M” in the system “methane-water phase-hydrate-R-2M” to regulate the self-preservation effect of methane gas hydrates

Correlating Oxidation State and Surface Ligand Motifs with the Selectivity of CO2 Photoreduction to C2 Products.

The design for non-Cu-based catalysts with the function of producing C2+ products requires systematic knowledge of the intrinsic connection between the surface state as well as the catalytic activity and selectivity. In this work, photochemical in-situ spectral surface characteristic technique combined with the first principle calculations (DFT) were applied to investigate the relationships among the composition of surface states, coordinated motifs, and catalytic selectivity of the titanium oxynitride catalyst. By adopting the process of CO2 photoreduction, we found that C2 product selectivity is positively correlated with the surface Ti2+/Ti3+ ratio while the surface oxidation state is regulated and controlled by coordinated motifs of N-Ti-O/V[O], which can reduce the potential dimerization energy barriers of *CO-CO* and promote the spontaneous formation of the subsequent *CO-CH2* intermediate. On the contrary, relatively high or low N/O coordination ratios will cause imbalance of coordination motifs in reducing surface states and abate the hydrogenation barriers of the methoxy group, thus facilitating methane formation. Such phenomenon provides a new design perspective and by such, researchers make a step close to the accurate production of photo-transformed CO2 products.

Evaluation of certain pollutants generation inside municipal solid waste landfills

Municipal solid waste disposal sites act as sources of secondary pollution of the environment with waste destruction products that undergo further chemical and biochemical transformations. The research deals with the issues of quantitative assessment of greenhouse gases and persistent organic pollutants formation within municipal solid waste landfills. It uses such methods as mathematical models of pollutants formation inside a municipal solid waste landfill body, namely methane and persistent organic pollutants formation. Bioorganic substance forming the major part of municipal solid waste generates methane, carbon dioxide and other compounds; presence of chlorine in various compounds included in the composition of waste causes unintentional formation of persistent organic pollutants, in particular PCDD/F. The article presents the results of measurements of methane formation (according to the National Gas Formation Model), carbon dioxide and non-methane volatile organic compounds formation (according to the LandGEM model) with relation to the conditions of the municipal solid waste landfill «Dalnytsky Kariery» that accepts waste from the Odesa industrial-and-urban agglomeration. It shows the municipal solid waste landfill as a significant source of greenhouse gases the amount of which increases rapidly under the conditions of long-term operation and constant delivery of waste. The discrepancy in the results of methane formation measurements indicates the need to adapt the LandGEM model that matches the Ukrainian conditions. It would allow determining a wide range of atmospheric polluting substances. The author's design determines the formation of persistent organic pollutants as exemplified by PCDD/F. The measurements showed that landfills act as a significant source of unintentional formation of PCDD/F, 99% of which accumulate inside a landfill itself. They also indicated that, under the conditions of a constant delivery of waste to a landfill, there is a rapid increase in the amount of PCDD/F formed, even with consideration of the half-life period. The landfill itself is considered as a main source of unintentional formation of PCDD/F within the whole Odesa agglomeration.

Optimal Icosahedral Copper-Based Bimetallic Clusters for the Selective Electrocatalytic CO2 Conversion to One Carbon Products.

Electrochemical CO2 reduction reactions can lead to high value-added chemical and materials production while helping decrease anthropogenic CO2 emissions. Copper metal clusters can reduce CO2 to more than thirty different hydrocarbons and oxygenates yet they lack the required selectivity. We present a computational characterization of the role of nano-structuring and alloying in Cu-based catalysts on the activity and selectivity of CO2 reduction to generate the following one-carbon products: carbon monoxide (CO), formic acid (HCOOH), formaldehyde (H2C=O), methanol (CH3OH) and methane (CH4). The structures and energetics were determined for the adsorption, activation, and conversion of CO2 on monometallic and bimetallic (decorated and core@shell) 55-atom Cu-based clusters. The dopant metals considered were Ag, Cd, Pd, Pt, and Zn, located at different coordination sites. The relative binding strength of the intermediates were used to identify the optimal catalyst for the selective CO2 conversion to one-carbon products. It was discovered that single atom Cd or Zn doping is optimal for the conversion of CO2 to CO. The core@shell models with Ag, Pd and Pt provided higher selectivity for formic acid and formaldehyde. The Cu-Pt and Cu-Pd showed lowest overpotential for methane formation.

CFD-Simulation of Isobutane Dehydrogenation for a Fluidized Bed Reactor

In the present study, a mathematical model of the isobutane dehydrogenation process for a laboratory reactor with a diameter of 2.8 cm and a height of 70 cm was created using CFD methods. A two-fluid model was selected as a model for the fluidization simulation, when the gas and solid granular phases were considered as continuous. The model of chemical kinetics considers three reactions that make the main contribution to the products mass fraction at the reactor outlet: the reaction of catalytic dehydrogenation of isobutane to isobutylene, the reaction of thermal cracking of isobutylene with the formation of methane and propylene, and the reaction of catalytic hydrogenation of propylene. The model was verified in a series of experimental studies. Experimental studies and numerical simulations were carried out for the process parameters: gas velocity 0.008, 0.012 and 0.016 m/s, gas temperature 550, 575, 600 and 625 °C, and catalyst mass 75, 100 and 125 g. The optimal process temperature was 575 °C, where the yield of isobutylene averaged 47.6% of the mass. As the temperature decreased, the yield of isobutylene decreased to 40.1% by weight on average. With an increase in temperature, the yield of isobutylene increased to 52.8% by weight on average, and the total yield of products of side reactions increased to 20% by weight on average. Changes in the gas velocity and catalyst mass had an insignificant effect on the values of the yield of isobutylene, but significantly affected the values of the yield of the by-products.

TECHNOLOGIES TO REDUCE EMISSION OF METHANE AND NITROUS OXIDE IN RICE FIELDS: A BRIEF REVIEW

Climate change caused by increasing anthropogenic greenhouse gas concentrations can threaten food security. Agricultural land is a source of food availability, however it is one source of GHG emissions, especially methane and nitrous oxide. Integration management of land, water, and plants in an integrated manner can be an effort to reduce the impact of climate change. This paper aims to inform the technologies to reduce emissions of methane and nitrous oxide in rice fields. One of the technologies to mitigate greenhouse gas emissions on agricultural land is through the use of natural materials as an inhibitor for the formation of methane and nitrous oxide in the soil due to the content of secondary metabolites in natural ingredients. Natural materials can simultaneously increase nitrogen nutrient uptake and improve crop yields. The methane production in rice fields is suppressed by more than 30% by coconut fiber, turmeric rhizomes, leaf of Ageratum conyzoides, and the leaf of Cosmos caudatus; while application of Cosmos caudatus and Ageratum conyzoides can also reduce the production of nitrous oxide more than 20%, respectively.

CO2 Hydrogenation to Renewable Methane on Ni/Ru Modified ZSM-5 Zeolites: The Role of the Preparation Procedure

Mono- and bimetallic Ni- and Ru-modified micro-mesoporous ZSM-5 catalysts were prepared by wet impregnation. The influence of the Ni content, the addition of Ru and the sequence of the modification by two metals on the physicochemical properties of the catalysts were studied. They were characterized by X-ray powder diffraction (XRD), N2 physisorption, temperature-programmed reduction (TPR-TGA), TEM and XPS spectroscopy. Formation of finely dispersed nickel and/or ruthenium oxide species was observed on the external surface and in the pores of zeolite support. It was found that the peculiarity of the used zeolite structure and the modification procedure determine the type of formed metal oxides, their dispersion and reducibility. XPS study revealed that the surface became rich in nickel and poorer in ruthenium for bimetallic catalysts. Ni had higher dispersion in the presence of ruthenium, and TPR investigations also confirmed its facilitated reducibility. The studied catalysts were tested in CO2 hydrogenation to methane. 10Ni5RuZSM-5 material showed the highest activity and high selectivity for methane formation, reaching the equilibrium conversion and 100% selectivity at 400 °C. Stability and reusability of the latter catalyst show that it is appropriate for practical application.

CIRCULAR ECONOMY APPLIED TO METHANE PRODUCTION FROM NATURAL GAS HYDRATE RESERVOIRS: POTENTIALITIES OF RESIDUAL DUST COMING FROM STEEL PLANTS

Natural gas hydrate represents one of the most promising solutions to answer to the constantly increasing energy demand; in addition, the possibility of recover methane via carbon dioxide injection, with a theoretical exchange ratio equal to 1, makes it a potential carbon neutral energy source. Among them, energetical costs associated to practical operations in marine deposits. The use of chemical inhibitors and or promoters to improve the exchange process is gaining increasing interest and researchers are mainly focused on finding less environmental unfriendly additives and on reducing their costs. In that direction, the present work deals with the possible use of waste dust, produced during steel mill processes, as promoter of the CO2/CH4 replacement process. That sand commonly contains a great variety of compounds, such as metal oxides, alumina, salts, and so on. Some of them have a chemical composition close to well-known hydrate inhibitors/promoters. Moreover, that application could be a further energetic cycle for a waste product. In this work, both methane and carbon dioxide hydrate formation were tested in absence and in presence of cupper oxides, with different concentrations. Hydrate formation and dissociation results where then compared among each other and with hydrate equilibrium values for those compounds.

Synergistic effect of sulfonated castor oil and porous medium on kinetics of gas hydrates formation

In recent years, interest in gas hydrates has increased as they represent a potential energy source and an alternative to the current environmentally friendly method of storing and transporting natural gas. In this study, the synergistic effect of a new promoting reagent – sulfonated castor oil (SCO) – and a porous medium on the formation and decomposition of methane and methane-propane hydrates was compared to that of sodium dodecyl sulfate (SDS) using the high-pressure differential scanning calorimetry (HP-μDSC) method. DSC tests demonstrated that water conversion in the presence of SCO in a porous substrate for methane hydrates reached 95% at high water saturation, which can be attributed to improved mass transfer in the presence of surfactants. However, this value did not exceed 60% for the hydrate of methane–propane mixture, indicating that the mechanism of promotion of the sI and sII hydrates differs. According to kinetic calculations based on the Avrami equation, both SDS and SCO accelerate the formation of hydrates, but for SCO, this is possible with less supercooling. The calorimetric measurements and kinetic parameter calculations demonstrated that SCO is comparable to the well-known reagent SDS in promoting activity in porous media with varying water saturation.