Gas Fraction Research Articles

The structure and dynamics of massive high-z cosmic-web filaments: three radial zones in filament cross-sections

ABSTRACT We analyse the internal structure and dynamics of cosmic-web filaments connecting massive high-z haloes. Our analysis is based on a high-resolution arepo cosmological simulation zooming-in on three Mpc-scale filaments feeding three massive haloes of $\sim 10^{12}\, \text{M}_\odot$ at z ∼ 4, embedded in a large-scale sheet. Each filament is surrounded by a cylindrical accretion shock of radius $r_{\rm shock} \sim 50 \, {\rm kpc}$. The post-shock gas is in virial equilibrium within the potential well set by an isothermal dark-matter filament. The filament line-mass is $\sim 9\times 10^8\, \text{M}_\odot \, {\rm kpc}^{-1}$, the gas fraction within rshock is the universal baryon fraction, and the virial temperature is ∼7 × 105 K. These all match expectations from analytical models for filament properties as a function of halo mass and redshift. The filament cross-section has three radial zones. In the outer ‘thermal’ (T) zone, $r \ge 0.65 \, r_{\rm shock}$, inward gravity, and ram-pressure forces are overbalanced by outward thermal pressure forces, decelerating the inflowing gas and expanding the shock outwards. In the intermediate ‘vortex’ (V) zone, 0.25 ≤ r/rshock ≤ 0.65, the velocity field is dominated by a quadrupolar vortex structure due to offset inflow along the sheet through the post-shock gas. The outward force is dominated by centrifugal forces associated with these vortices, with additional contributions from global rotation and thermal pressure. Shear and turbulent forces associated with the vortices act inwards. The inner ‘stream’ (S) zone, $r \lt 0.25 \, r_{\rm shock}$, is a dense isothermal core, $T\sim 3 \times 10^4 \, {\rm K}$ and $n_{\rm H}\sim 0.01 \, {\rm cm^{-3}}$, defining the cold streams that feed galaxies. The core is formed by an isobaric cooling flow and is associated with a decrease in outward forces, though exhibiting both inflows and outflows.

Modeling pyrolysis kinetics of extracted biomass components with the bio-chemical percolation devolatilization model

Within the pyrolysis modeling of biomass, the solid is typically interpreted as a mixture of cellulose, hemicellulose, and lignin, where the components react independently before the products are linearly superimposed. This assumption applies to the bio-chemical percolation devolatilization model (Bio-CPD), which, as a network model, represents the physicochemical processes very realistically. A literature review regarding available structural and kinetic parameters for the Bio-CPD model revealed four hits. To investigate and evaluate the model predictivity, experiments from extracted lignocellulosic biomass components pyrolyzed separately in a fluidized bed reactor are used as reference data. Using single-component data simplifies the reaction chemistry by minimizing interactions between the components and best approximates the model assumptions. The comparison between experimentally obtained total volatile release rates and model predictions revealed the parameter set from Vizzini et al. (2008) for cellulose and the one from Sheng and Azevedo (2002) for hemicellulose as best-suitable candidates to predict the pyrolysis behavior for the boundary conditions of the fluidized bed reactor. For lignin, instead, the Genetti correlation (Genetti, Fletcher, and Pugmire, 1999) to estimate structural parameters based on the ultimate and proximate analysis led to better results than all other sets. Further, the analysis of light gas and tar fractions showed a high relevance to model secondary tar cracking reactions in the fluidized bed reactor system.

Efficient Selective Capture of Carbon Dioxide from Nitrogen and Methane Using a Metal-Organic Framework-Based Nanotrap

Selective carbon capture from exhaust gas and biogas, which mainly involves the separation of CO2/N2 and CO2/CH4 mixtures, is of paramount importance for environmental and industrial requirements. Herein, we propose an interesting metal-organic framework-based nanotrap, namely ZnAtzCO3 (Atz− = 3-amino-1,2,4-triazolate, CO32− = carbonate), with a favorable ultramicroporous structure and electrostatic interactions that facilitate efficient capture of CO2. The structural composition and stability were verified by FTIR, TGA, and PXRD techniques. Particularly, ZnAtzCO3 demonstrated high CO2 capacity in a wide range of pressures, with values of 44.8 cm3/g at the typical CO2 fraction of the flue gas (15 kPa) and 56.0 cm3/g at the CO2 fraction of the biogas (50 kPa). Moreover, ultrahigh selectivities over CO2/N2 (15:85, v:v) and CO2/CH4 (50:50, v:v) of 3538 and 151 were achieved, respectively. Molecular simulations suggest that the carbon atom of CO2 can form strong electrostatic Cδ+···δ−O-C interactions with four oxygen atoms in the carbonate ligands, while the oxygen atom of CO2 can interact with the hydrogen atoms in the triazolate ligands through Oδ−···δ+H-C interactions, which makes ZnAtzCO3 an optimal nanotrap for CO2 fixation. Furthermore, breakthrough experiments confirmed excellent real-world separation toward CO2/N2 and CO2/CH4 mixtures on ZnAtzCO3, demonstrating its great potential for selective CO2 capture.

Valorization of Agricultural Polyolefin Plastic Waste in the Kingdom of Morocco through Thermal Pyrolysis: Influence of Thermal Parameters on Pyrolytic Oil Yields

This article focuses on exploring the recycling of agricultural plastic waste mixtures through the route of thermal cracking. In an experimental setting within a pilot-scale batch reactor, the impact of temperatures and heating rates on the yields obtained in the pyrolysis process have been meticulously examined. The temperatures of the pyrolysis process were varied between 360°C and 480°C, while the heating rates underwent changes, including 10, 15, and 30°C/min. The response parameters were the liquid, solid, and gas fractions. This research indicates that moderate temperatures and slower heating rates, resulting in extended reaction times, promote the generation of liquid fuel from pyrolysis. We achieved an optimal liquid fuel yield of 79% at 380°C, employing a temperature ramp of 10°C/min. Characterization of pyrolysis fuel resulting from the pyrolysis process revealed an extensive variety of hydrocarbons, requiring prior fractionation for optimal use in internal combustion engines. This step led to the separation into three distinct fractions: a light fraction (analogous to gasoline), accounting for 22.62% of the total weight, a middle fraction (similar to diesel), weighing 53.67% of the weight, and a heavy fraction (comparable to heavy diesel), totaling 23.71% of the weight. The light fraction presents an octane rating in line with conventional gasoline values, while the middle fraction meets the required cetane criteria for diesel.

Starbursts driven by central gas compaction

ABSTRACT Starburst (SB) galaxies are a rare population of galaxies with star formation rates (SFRs) greatly exceeding those of the majority of star-forming galaxies with similar stellar mass. It is unclear whether these bursts are the result of either especially large gas reservoirs or enhanced efficiencies in converting gas into stars. Tidal torques resulting from gas-rich galaxy mergers are known to enhance the SFR by funnelling gas towards the centre. However, recent theoretical works show that mergers do not always trigger an SB and not all SB galaxies are interacting systems, raising the question of what drives an SB. We analyse a large sample of SB galaxies and a mass- and redshift-matched sample of control galaxies, drawn from the FIREbox cosmological volume at z = 0–1. We find that SB galaxies have both larger molecular gas fractions and shorter molecular depletion times than control galaxies, but similar total gas masses. Control galaxies evolve towards the SB regime by gas compaction in their central regions, over time-scales of ∼70 Myr, accompanied by an increase in the fraction of ultradense and molecular gas. The driving mechanism behind the SB varies depending on the mass of the galaxy. Massive ($M_\star \gtrsim 10^{10}~\rm {M}_\odot$) galaxies undergoing intense, long-lasting SBs are mostly driven by galaxy interactions. Conversely, SBs in non-interacting galaxies are often triggered by a global gravitational instability, which can result in a ‘breathing’ mode in low-mass galaxies.

Gas phase interactions between tellurium and organic material in severe nuclear accident scenarios

One of the volatile fission products potentially released during a severe nuclear accident is tellurium. Recently, tellurium has been shown to form volatile organic tellurides from paint solvents in aqueous solutions which could further increase the release. However, not much is known about the possible interactions between tellurium and organic material in gas phase. In this study, tellurium was exposed to conditions simulating the containment atmosphere during an accident. Moreover, volatile organic compounds were introduced to the gas phase representing the presence of organic material in the containment during the accident. The results suggest that tellurium aerosols and organic material interact in the gas phase which was observed as an increase in the gaseous fraction and a change in the XPS spectra. Although no exact species were identified, the results raise questions about the behavior of tellurium in severe accident conditions, especially, regarding the reactions involving organic material.

Quantification of fossil fuel CO2 from combined CO, δ13CO2 and Δ14CO2 observations

Abstract. We present a new method for partitioning observed CO2 enhancements (CO2xs) into fossil and biospheric fractions (Cff and Cbio) based on measurements of CO and δ13CO2, complemented by flask-based Δ14CO2 measurements. This method additionally partitions the fossil fraction into natural gas and petroleum fractions (when coal combustion is insignificant). Although here we apply the method only to discrete flask air measurements, the advantage of this method (CO- and δ13CO2-based method) is that CO2xs partitioning can be applied at high frequency when continuous measurements of CO and δ13CO2 are available. High-frequency partitioning of CO2xs into Cff and Cbio has already been demonstrated using continuous measurements of CO (CO-based method) and Δ14CO2 measurements from flask air samples. We find that the uncertainty in Cff estimated from the CO- and δ13CO2-based method averages 3.2 ppm (23 % of the mean Cff of 14.2 ppm estimated directly from Δ14CO2), which is significantly less than the CO-based method which has an average uncertainty of 4.8 ppm (34 % of the mean Cff). Using measurements of CO, δ13CO2 and Δ14CO2 from flask air samples at three sites in the greater Los Angeles (LA) region, we find large contributions of biogenic sources that vary by season. On a monthly average, the biogenic signal accounts for −14 to +25 % of CO2xs with larger and positive contributions in winter and smaller and negative contributions in summer due to net respiration and net photosynthesis, respectively. Partitioning Cff into petroleum and natural gas combustion fractions reveals that the largest contribution of natural gas combustion generally occurs in summer, which is likely related to increased electricity generation in LA power plants for air-conditioning.

Analysis of two-phase gas-liquid flow in an Electric Submersible Pump using A CFD approach

This study comprehensively analyzes a mixed-flow Electric Submersible Pump's (ESP) performance under challenging conditions of low flow rates and high gas fractions. The research leverages a computational model built on the Eulerian-Eulerian methodology, adeptly solving the 3D incompressible Navier-Stokes equations for each phase. To ensure an encompassing depiction of the flow dynamics within the ESP, the model considers critical parameters such as the bubble diameter and interphase forces, including drag, lift, and virtual mass force.Key findings reveal that the ESP's performance deteriorates markedly under the studied conditions. One of the primary influencers is the phenomenon of gas locking, where gas accumulation within the impeller hampers the consistent flow of liquid, thereby degrading the pump's efficiency. In addition, the model delineated the occurrence of the surging phenomenon across diverse gas volume fractions and rotational speeds, which further exacerbates the reduction in the ESP's performance. Intriguingly, the bubble diameter was identified as a decisive factor, especially at minuscule flow rates. Large bubble diameters instigate the formation of gas pockets on the suction side of the vane, culminating in a segregated flow pattern and further declining pump efficiency.On the other hand, the drag force is the primary interaction force between phases of gas-liquid flow. Other interfacial forces, such as lift and virtual mass force, change the pump's performance but do not affect the gas flow and distribution patterns for a one-stage configuration. Results show that the Schiller-Neuman drag coefficient offers a better fit than the Bozano-Dente coefficient.Conclusively, the study underscores the indispensable role of nuanced computational models in elucidating the intricate flow dynamics within ESPs, especially under conditions fraught with operational challenges. The insights gleaned enrich our understanding of ESP performance dynamics and provide a roadmap for designing more resilient and efficient pumping systems in the future.

The algorithm used for the calculation of gas exchange affects the estimation of O2 uptake kinetics at the onset of moderate-intensity exercise.

At the start of a moderate-intensity square-wave exercise, after a short delay, breath-by-breath O2 uptake at the mouth is approximated to a mono-exponential function, whose time constant is considered matched to that of the O2 uptake of the working muscles. We compared the kinetic parameters obtained from the breath-by-breath gas exchange data yielded by the 'Independent-breath' algorithm (IND), which accounts for the changes in lung gas stores, with those obtained with the classical 'Expiration-only' algorithm (EXP). The two algorithms were applied on the same flow and gas fraction traces acquired on 10 healthy volunteers, performing 10 times the same moderate-intensity exercise transition. Repeated O2 uptake responses were stacked together and the kinetic parameters of a mono-exponential function were estimated by non-linear regression, removing the data pertaining to 1-s progressively longer initial periods (ΔTr ). Independently of ΔTr , the mean response time (time constant + time delay) obtained for the IND data was faster compared to the EXP data (∼43s vs. ∼47s, P<0.001), essentially because of shorter time delays. Between ΔTr =16s and ΔTr =29s, the time constants of the IND data decreased (30.7s vs. 28.0s, P<0.05; drop=10%), but less than those of the EXP data (32.2s vs. 26.2s, P<0.001; drop=23%); with the same ΔTr , the time constants of the two algorithms' data were not different (P>0.07). The different decrease in the time constant, together with the different mean response time, suggests that the data yielded by the two algorithms provide a different picture of the phenomena occurring at the beginning of the exercise.

Processing plastic waste via pyrolysis-thermolysis into hydrogen and solid carbon additive to ethylene-vinyl acetate foam for cushioning applications

A strategy for enhancing value creation from pyrolysis gas and oil, derived from plastic waste, through the generation of two additional outputs of solid carbon and hydrogen was investigated. Three types of hard-to-recycle plastic waste (marine plastic litter, household mixed plastics and cosmetic products packaging) were thermally treated in two stages: (i) decomposition of feedstock into gas and oil via pyrolysis at 600 °C; and (ii) thermolytic conversion of the pyrolysis gas and a fraction of oil into hydrogen and solid carbon at 1300 °C separately. The thermolysis of both pyrolysis gas and oil fractions predominantly resulted in the production of solid carbon (39–70 wt% per plastic feedstock and carbon content of 91.3–98.6 wt%) and H2-rich gas (H2 yield of 5.9–10.8 wt% per plastic waste feedstock and H2 content of 71.4–97.2 vol% per gas volume). The incorporation of pyrolysis oil into the thermolysis process could enhance the outputs of solid carbon and hydrogen. Characterizations of solid carbon and hydrogen obtained from pyrolysis gas and oil fractions were further conducted. The observed similar properties of H2 and solid carbon from pyrolysis gas and oil supported the feasibility of introducing all the pyrolytic products together into the thermolysis process without condensation of oil. To enhance the value of these solid carbon derived from plastics for practical usage, we utilized the obtained solid carbon as a reinforcing agent for polymer composite foam development. The solid carbon reinforced composite foam displayed great abrasion resistance (wear loss: 240 mg), compression strength (0.347 MPa), and dynamic impact properties (energy returned: 124 J/m and energy absorbed: 57.3 J/m), emphasizing the viability of solid carbon as a nucleating agent and reinforcing filler in polymer foam for cushioning applications. Overall, the strategy of pyrolysis-thermolysis, which harnesses both pyrolysis gas and oil, unlocks additional value creation by producing two new outputs from plastic waste. Depending on the market prices for solid carbon and hydrogen, this can substantially change the economics of plastic waste management and create new revenue streams, incentivizing plastic waste collection and processing.

Predicting the UV Escape Fraction of the First Galaxies in the Renaissance Simulations with Machine Learning

Cosmic reionization is likely driven by UV starlight emanating from the first generations of galaxies. A galaxy’s UV escape fraction, or the fraction of photons escaping from the galaxy, is useful to quantify its contribution to reionization. However, the UV escape fraction is notoriously difficult to predict due to local environment dependency and variability over time. Using data from the Renaissance Simulations, we attempt to make predictions about the impact of the first stars and galaxies on their environments. We present a time-independent classification model using a general artificial neural network architecture to predict the UV escape fraction given other galaxy properties—namely halo mass, stellar mass, redshift, star formation rate, lookback time, and gas fraction. We find our validation accuracy to be approximately 50%–65%, depending on the data set size from each zoom-in region of the Renaissance Simulations.

Assessment of the Void Fraction Correlations for Gas–Liquid Two-Phase Flows in Pipeline-Risers

In the past decades, studies on a void fraction of gas–liquid two-phase flow have mainly focused on straight pipes, while voidage in pipeline-riser flows have been largely neglected. In this work, the void fraction of gas–liquid two-phase flow in pipeline-riser was investigated. The test loop consists of a 12 m horizontal pipe, followed by a 2 m downward inclined pipe, and ended at a riser. Both vertical riser and catenary riser were used in the experiment. Slip in severe slugging and annular flow was more pronounced than in bubbly flow. The transition from the mixed to the separated flow occurs at gas–liquid volumetric flow rate ratio equals to 0.8. However, the separated flow forms when the gas–liquid volumetric flow rate ratio is greater than 0.9 for catenary riser. A total of 28 correlations for predicting the void fractions were evaluated with the experimental data. The Mishima and Hibiki correlation was found to be the most accurate among the studied correlations, predicting 68.5% and 69.3% of the measured data within ±30% for vertical and catenary riser, respectively. A new correlation considering the effect of the elbow is still needed for more accurate prediction of void fraction in pipeline-riser.

Catalytic Gasification and Reforming of Residual Biomass in a Bench Scale System with Low Cost Catalysts.

This paper demonstrates the effectiveness of using of different catalysts for reforming tars contained in the syngas of biomass gasifiers. The conversion of the tar content allows to obtain high quality syngas and to maximize the gas fraction. A bench scale equipment consisting of an autothermal fluidized bed gasifier and a downstream packed bed reformer was used. Pine sawdust was selected as the feedstock for gasification. TGA analysis showed that the temperature must be above 350 °C to ensure the ignition of the biomass and maintain the process in an autothermal steady-state. Dolomite and pyrolysis char were used to test of the fluidized bed catalysts. In the reformer, dolomite, pyrolysis char, iron doped activated carbon and spent HDS catalyst were used. All catalysts decreased the CO2 concentration in the product gas and increased H2 , CH4 and CO. When iron doped activated carbon is used, tar contents below 60 g/Nm3 in the product gas could be obtained, reaching less than 1 g/Nm3 . The best value of LHV (lower heating value) was obtained with pyrolysis char as a catalyst (4.8 MJ/Nm3 ). The results demonstrate that catalytic biomass gasification with downstream tar reforming with low-cost catalysts is a promising solution for energy applications.

Study on flow regulation characteristics of fuel feeding systems for powder engines

Changing the mass flow rate of powder propellant with high precision and large range is essential and challenging for adjusting thrust of the powder engine. In this paper, the regulation characteristics of the powder flow rate are investigated by adjusting two gases, namely driving gas and regulating gas. Firstly, the effect of driving gas on powder flow are analyzed, which provides the large ranged flow regulation with the adjustment rate of 2.39 and high precision with resolution ratio of 0.8 g/s. The powder flow rate is successfully predicted based on the Bernoulli equation, not only with an less deviation of 4.73%, but also more conducive to development of the lightweight system. Second, the introduction of regulating gas provides a new method for powder flow regulation. The powder flow rate can achieve a regulation rate of 1.36 with a small amount of regulating gas. The linear relationship between powder flow rate and regulating gas fraction is established to enable its prediction. Finally, the regulation logic is proposed, based on which the flow rate can be increased or decreased by adjusting the quantities of these two gases flexibly. This study can provide a reference for the thrust regulation of powder engines.

AGN radiation imprints on the circumgalactic medium of massive galaxies

ABSTRACT Active galactic nuclei (AGNs) in cosmological simulations generate explosive feedback that regulates star formation in massive galaxies, modifying the gas phase structure out to large distances. Here, we explore the direct effects that AGN radiation has on gas heating and cooling within one high-resolution z = 3 dark matter halo as massive as a quasar host (Mh = 1012.5M⊙), run without AGN feedback. We assume AGN radiation to impact the circumgalactic medium (CGM) anisotropically, within a bi-cone of angle α. We find that even a relatively weak AGN (black hole mass M• = 108M⊙ with an Eddington ratio λ = 0.1) can significantly lower the fraction of halo gas that is catastrophically cooling compared to the case of gas photoionized only by the ultraviolet background (UVB). Varying M•, λ, and α, we study their effects on observables. A 109M⊙ AGN with λ = 0.1 and $\alpha \approxeq 60^{^{\rm o}}$ reproduces the average surface brightness (SB) profiles of Ly α, He ii, and C iv, and results in a covering fraction of optically thick absorbers within observational estimates. The simulated SB$_{\rm C\, \rm{\small IV}}$ profile is steeper than observed, indicating that not enough metals are pushed beyond the very inner CGM. For this combination of parameters, the CGM mass catastrophically cooling is reduced by half with respect to the UVB-only case, with roughly same mass out of hydrostatic equilibrium heating up and cooling down, hinting to the importance of self-regulation around AGNs. This study showcases how CGM observations can constrain not only the properties of the CGM itself, but also those of the AGN engine.

Formation, coalescence and behaviour of bulk nanobubbles in dodecane and isooctane and their thermophysical properties: A comprehensive molecular study

In recent decades, nanobubbles (NBs) have attracted great attentions of researchers in a number of fields, including aquaculture, water treatment, biomedical engineering and energy/power engineering. However, the fundamental understanding of these tiny bubbles through experimental techniques is very challenging. Dodecane, as a phase change material with a high boiling point, and isooctane, as an alternative fuel with high octane number and low volatility, have been researched and used in energy applications. In this work, the nucleation, coalescence and behaviour of formed NBs of carbon dioxide (CO2), oxygen (O2), nitrogen (N2), and hydrogen (H2) gases in dodecane and isooctane samples as well as their effects on the thermo-physical properties of the samples were investigated by means of molecular dynamics (MD) simulations. The weight fraction of the added gas and temperature were also investigated to understand their effects on the bubble dynamics and inherent properties. The results reveal that the addition of CO2 gas leads to the biggest drop in the viscosity of the dodecane by 20.47%, while the dispersion of oxygen gas in dodecane increases the viscosity. It is also found that samples containing NBs have higher specific heat capacity than samples without NBs and the highest specific heat capacity improvement can be obtained by dissolving hydrogen NBs. Furthermore, it is found that specific heat capacity of isooctane sample increases by increasing the weight fraction of dispersed gas. However, dodecane shows the opposite trend. By increasing the system temperature, the specific heat capacity of dodecane sample increases while isooctane sample again shows the opposite trend.

BUTEN-1-in BUTEN-2-yə İZOMERLƏŞMƏSİ REAKSİYASINDA BİNAR KOBALT TƏRKİBLİ KATALİZATORLARIN AKTİVLİYİ

Hydrogen is considered the main source of chemical energy that can be converted directly into electricity and with the help of fuel cells into zero emissions of harmful waste, such as volatile organic compounds, nitrogen oxides and carbon. The production of hydrogen in accordance with the generation of energy using a fuel cell is considered a promising alternative to stationary and portable power generation plants in the future. Various methods are used to produce hydrogen: water electrolysis, gasification, partial oxidation of heavy oil and steam corrugation of organic compounds. Currently, in industry, about 90% of hydrogen is produced by the reaction of high-temperature steam reforming of light fractions of natural gas or oil. An attractive alternative to hydrogen production is the reaction of ethanol steam reforming. The activity of binary iron-cobalt, zinc-cobalt and magnesium-cobalt oxide catalysts in the reaction of isomerization of butene-1 to butenes-2 was studied. Iron-cobalt, zinc-cobalt and magnesium-cobalt oxide catalysts were prepared by co-precipitation from aqueous solutions of iron, zinc, magnesium and cobalt nitrate salts. The resulting mixture was evaporated at 95-100°C, then the resulting precipitate was dried at 100-120°C and then decomposed at 250°C until the nitrogen oxides were completely separated. The resulting solid was calcined at 700°C for 10 hours. Thus, 27 catalysts were prepared satisfying the following conditions: mA/NB, where A is Mo, Ti, Cu; cis, m,n=1-9, m+n=10. The isomerization reaction of butene-1 to butene-2 was carried out at a rate of 1200 h-1 volume of feedstock in the temperature range of 150-400°C. The reactor was filled with 5 mL of 1-2 mm thick catalyst and fed with a reaction mixture consisting of butene-1 and nitrogen. The ratio of butene-1 to nitrogen is 1:9. It is shown that with increasing cobalt content in the Fe-Co-o catalyst composition, its activity in the isomerization reaction reaches a maximum on catalysts with equivalent ratio of initial elements. The ratio of trans- and cis-butenes-2 practically does not change and is equal to 1.2. It is found that both Lewis acid centers and Bransted acid centers are present on the surface of this catalyst in approximately equal amounts. It was found that with increasing zinc content in the catalyst composition, the degree of butene-1 isomerization decreases and the ratio of trans-butene-2 to cis-butene-2 increases from 0 to 2.1, indicating the presence of Lewis and Bronsted acid centers on the surface of Zn-Co-O catalysts. It is found that for the Mg-Co-O catalytic system the ratio of trans and cis butenes-2 yields varies in the range 0.8-1.5. It is shown that, in the whole temperature range studied, the atomic ratio of cobalt and magnesium has a strong influence on their activity in the reaction of Butene-1 isomerization into Butene-2. It is found that the number of Lewis and Bronsted acid centers is practically independent of the composition of the Mg-Co-O catalytic system. Based on the study of the reaction of butene-1 to butene-2 isomerization on binary cobalt-containing catalysts, it was found that the samples with equimolar ratios of primary elements in Fe-Co-O catalysts, as well as samples with one of the predominant elements in the catalytic systems Zn-Co-O and Mg-Co-O are active. Keywords: Isomerization, butene-1, butenes-2, binary catalysts Cobalt oxide.

A prediction of interfacial tension by using molecular dynamics simulation: A study on effects of cushion gas (CO2, N2 and CH4) for Underground Hydrogen Storage

Carbon Dioxide (CO2) emissions from fossil fuel consumption have caused global warming and remain challenging problems for mitigation. Underground Hydrogen Storage (UHS) provides clean fuel and replaces traditional fossil fuels to reduce emissions of CO2. Geological formations such as depleted oil/gas reservoirs, deep saline aquifers and shale formations have been recognized as potential targets to inject and store H2 into the subsurface formations for large-scale implementation of CCS and UHS. However, the presence of H2 with cushion gas at different fractions under different geo-storage conditions, which can influence Hydrogen's flow properties, was not investigated widely. Until now, studies of interfacial properties between water and a mixture of cushion gas (CO2, N2 or CH4) in the presence of H2 are very limited or unavailable data in experiments and simulations. In this study, many predictions by using molecular dynamics simulation were conducted to predict the interfacial tension (γ) for the systems of H2/CO2/H2O, H2/N2/H2O and H2/CH4/H2O at different pressures, temperatures, and fractions of cushion gases A comparison between the predicted γ results from the simulation and previous research were also made. The findings of this study indicated that γ of H2/CO2/H2O, H2/CH4/H2O, and H2/N2/H2O, as a function of pressure, temperature, and fraction of H2, decreased with increasing pressures and temperatures and increased with increasing H2% in the mixture. Additionally, an extending or new γ data in simulation for the CO2/H2/H2O, N2/H2/H2O and CH4/H2/H2O systems from this study were reported and support evaluating the stability and storage capacity of H2 combined with the cushion gas in geological formations. Furthermore, it can contribute to de-risking and proceeding safely and efficiently for the large-scale implementation of Underground Hydrogen Storage.

Absorption of HCl on sodium-based absorbents at medium and high temperatures: The effect of competing absorption of SO2 and H2O

The utilization of sodium bicarbonate (NaHCO3) as a solid reactant for the mitigation of acidic pollutants from industrial flue gas streams represents a straightforward and efficient process solution. The paper addresses the problem of medium- to high-temperature flue gas dechlorination by investigating the effects of base particle size, temperature, water vapour and different flue gas fractions on the removal of HCl from simulated flue gases by NaHCO3 in a fixed-bed reactor, and the effects of the presence of SO2 and H2O on the chlorination reactivity of NaHCO3 are also investigated by density functional theory (DFT) calculations. The adsorption results implied that 300 °C was the optimum temperature for HCl removal by NaHCO3 in a reaction system not affected by SO2 or H2O; The higher the HCl concentration, the greater the HCl capture, but when the concentration is too high, due to the dense product layer makes the HCl gas molecules to the internal diffusion is blocked, the dechlorination effect becomes poor. The smaller the particle size of NaHCO3, the better the removal of HCl. In the system containing SO2, theoretical calculations based on density functional theory show that the presence of SO2 affects the exchange of electrons between the Cl atoms in HCl and Na2CO3, and the bonding ability of the Na-Cl bond is weakened, thus weakening the dechlorination ability of Na2CO3; However, SO2 has little effect on HCl removal at the same concentration, due to the fact that HCl rapidly consumes the easily accessible surface of the absorber and SO2 must diffuse deeper into the particles for the reaction to occur, suggesting a preferred reaction between HCl and NaHCO3. After the addition of H2O, the adsorption energy of HCl on the surface of Na2CO3(200) was greater than the adsorption energy of SO2 on the surface of Na2CO3(200), and HCl was preferentially adsorbed on the surface of Na2CO3(200), which preferentially reacted with the absorber. These findings help to elucidate the principle of HCl absorption by NaHCO3 and the competition mechanism between HCl and SO2, and improve the theoretical knowledge of acid gas absorption by NaHCO3.

HCN emission from translucent gas and UV-illuminated cloud edges revealed by wide-field IRAM 30 m maps of the Orion B GMC

Context. Massive stars form within dense clumps inside giant molecular clouds (GMCs). Finding appropriate chemical tracers of the dense gas (n(H2) &gt; several 104 cm−3 or AV &gt; 8 mag) and linking their line luminosity with the star formation rate is of critical importance. Aims. Our aim is to determine the origin and physical conditions of the HCN-emitting gas and study their relation to those of other molecules. Methods. In the context of the IRAM 30m ORION-B large program, we present 5 deg2 (~250 pc2) HCN, HNC, HCO+, and CO J =1–0 maps of the Orion B GMC, complemented with existing wide-field [C I] 492 GHz maps, as well as new pointed observations of rotationally excited HCN, HNC, H13CN, and HN13C lines. We compare the observed HCN line intensities with radiative transfer models including line overlap effects and electron excitation. Furthermore, we study the HCN/HNC isomeric abundance ratio with updated photochemical models. Results. We spectroscopically resolve the HCN J = 1–0 hyperfine structure (HFS) components (and partially resolved J = 2−1 and 3−2 components). We detect anomalous HFS line intensity (and line width) ratios almost everywhere in the cloud. About 70% of the total HCN J = 1−0 luminosity, L′(HCN J = 1−0) = 110 K km s−1 pc−2, arises from AV &lt; 8 mag. The HCN/CO J = 1−0 line intensity ratio, widely used as a tracer of the dense gas fraction, shows a bimodal behavior with an inflection point at AV &lt; 3 mag typical of translucent gas and illuminated cloud edges. We find that most of the HCN J = 1−0 emission arises from extended gas with n(H2) &lt; 104 cm−3, and even lower density gas if the ionization fraction is χe ≥ 10−5 and electron excitation dominates. This result contrasts with the prevailing view of HCN J = 1−0 emission as a tracer of dense gas and explains the low-AV branch of the HCN/CO J = 1−0 intensity ratio distribution. Indeed, the highest HCN/CO ratios (~ 0.1) at AV &lt; 3 mag correspond to regions of high [C I] 492 GHz/CO J = 1−0 intensity ratios (&gt;1) characteristic of low-density photodissociation regions. The low surface brightness (≲ 1 K km s−1) and extended HCN and HCO+ J = 1−0 emission scale with IFIR – a proxy of the stellar far-ultraviolet (FUV) radiation field – in a similar way. Together with CO J = 1−0, these lines respond to increasing IFIR up to G0 ≃ 20. On the other hand, the bright HCN J = 1−0 emission (&gt; 6 K km s−1) from dense gas in star-forming clumps weakly responds to IFIR once the FUV field becomes too intense (G0 &gt; 1500). In contrast, HNC J = 1−0 and [C I] 492 GHz lines weakly respond to IFIR for all G0. The different power law scalings (produced by different chemistries, densities, and line excitation regimes) in a single but spatially resolved GMC resemble the variety of Kennicutt-Schmidt law indexes found in galaxy averages. Conclusions. Given the widespread and extended nature of the [C I] 492 GHz emission, as well as its spatial correlation with that of HCO+, HCN, and 13CO J = 1−0 lines (in this order), we argue that the edges of GMCs are porous to FUV radiation from nearby massive stars. Enhanced FUV radiation favors the formation and excitation of HCN on large scales, not only in dense star-forming clumps, and it leads to a relatively low value of the dense gas mass to total luminosity ratio, α (HCN) = 29 M⊙/(K km s−1pc2) in Orion B. As a corollary for extragalactic studies, we conclude that high HCN/CO J = 1−0 line intensity ratios do not always imply the presence of dense gas, which may be better traced by HNC than by HCN.