Order Of CO2 Research Articles

Microscopic insights into water wetting behaviors and physical origin on α-quartz exposed to varying underground gas species

Understanding the wetting behaviors of water on quartz surfaces and underlying mechanisms when immersed in varying gas environments is crucial for the efficient implementation of geological engineering projects, such as H2gas geo-storage, natural gas production, and greenhouse gas geo-sequestration.In the present work, classical molecular dynamic (MD) simulations are applied to investigate the deionized (DI) water and brine (with a salinity of ∼1.5 M and ∼3.5 M) wettability of quartz surfaces and interfacial properties in the presence of various gas species (i.e., H2, CH4, and CO2) under a typical geological condition (333K and 20 MPa). The inherent mechanisms regulating surface wettability are revealed by Young’s equation and interaction energy analysis. Thanks to the strong electrostatic interaction, water forms several adsorption layers on quartz surfaces, whereas gas molecules are mainly adsorbed on the region where the water is not accessible through van der Waals interaction. The presence of salt ions has negligible effects on water and gas distributions as they tend to be depleted from the surface area. When immersed in varying gas species, the contact angle (CA) of water on quartz follows an order of CO2 > CH4 > H2due to the faster decay in gas–solid interaction compared with gas–water interaction. Increasing salt ions is generally unfavorable for the spreading of water on quartz surfaces regardless of gas types resulting in a larger CA value, which is primarily attributed to the augmented gas–water interfacial tension. This study provides important insights into the wettability behaviors of water on quartz surfaces under varying gas conditions and deepens the understanding of the molecular origin of wetting characteristics on quartz surfaces, which is beneficial for explaining relevant phenomena and leading engineering practice.

Observed kinetics for the production of diethyl carbonate from CO2 and ethanol catalyzed by CuNi nanoparticles supported on activated carbon

Monometallic and bimetallic Cu:Ni catalysts with different Cu:Ni molar ratios (3:1, 2:1, 1:1, 1:2, 1:3) were synthesized by wetness impregnation on activated carbon and characterized by TPR (temperature programmed reduction), XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy). The synthesized catalysts were evaluated in the gas phase production of diethyl carbonate from ethanol and carbon dioxide. The largest catalytic activity was obtained over the bimetallic catalyst with a Cu:Ni molar ratio of 3:1. Its improved activity was attributed to the formation of a Cu–Ni alloy on the surface of the catalyst, evidenced by XPS and in agreement with a previous assignment based on Vegard law and TPR analysis. During the reaction rate experiments, it observed the presence of a maximum of the reaction rate as a function of temperature, a tendency also reported for other carbon dioxide–alcohol reactions. It showed that the reaction rate-temperature data can be adjusted with a reversible rate equation. The initial rate as a function of reactant partial pressure data was satisfactorily adjusted using the forward power law rate equation and it was found that the reaction rate is first order in CO2 and second order in ethanol.

Solvent Exsolution and Liberation from Different Heavy Oil–Solvent Systems in Bulk Phases and Porous Media: A Comparison Study

In this paper, experimental and numerical studies were conducted to differentiate solvent exsolution and liberation processes from different heavy oil–solvent systems in bulk phases and porous media. Experimentally, two series of constant-composition-expansion (CCE) tests in a PVT cell and differential fluid production (DFP) tests in a sandpacked model were performed and compared in the heavy oil–CO2, heavy oil–CH4, and heavy oil–C3H8 systems. The experimental results showed that the solvent exsolution from each heavy oil–solvent system in the porous media occurred at a higher pressure. The measured bubble-nucleation pressures (Pn) of the heavy oil–CO2 system, heavy oil–CH4 system, and heavy oil–C3H8 system in the porous media were 0.24 MPa, 0.90 MPa, and 0.02 MPa higher than those in the bulk phases, respectively. In addition, the nucleation of CH4 bubbles was found to be more instantaneous than that of CO2 or C3H8 bubbles. Numerically, a robust kinetic reaction model in the commercial CMG-STARS module was utilized to simulate the gas exsolution and liberation processes of the CCE and DFP tests. The respective reaction frequency factors for gas exsolution (rffe) and liberation (rffl) were obtained in the numerical simulations. Higher values of rffe were found for the tests in the porous media in comparison with those in the bulk phases, suggesting that the presence of the porous media facilitated the gas exsolution. The magnitudes of rffe for the three different heavy oil–solvent systems followed the order of CO2 > CH4 > C3H8 in the bulk phases and CH4 > CO2 > C3H8 in the porous media. Hence, CO2 was exsolved from the heavy oil most readily in the bulk phases, whereas CH4 was exsolved from the heavy oil most easily in the porous media. Among the three solvents, CH4 was also found most difficult to be liberated from the heavy oil in the DFP test with the lowest rffl of 0.00019 min−1. This study indicates that foamy-oil evolution processes in the heavy oil reservoirs are rather different from those observed from the bulk-phase tests, such as the PVT tests.

Fe2+-driven Mo(IV)/Mo(VI) redox-catalyzed PMS degradation of RhB

Molybdenum disulfide (MoS2) can activate peroxymonosulfate (PMS) to degrade organic pollutants, but due to the continuous consumption of Mo(IV) during the reaction and the slow conversion of Mo(VI) to Mo(IV), the severe shortage of Mo(IV) regeneration will cause a large loss of catalyst, thus increasing the operation cost. In this study, different transition metal ions were introduced directly into the reaction system. The effects of conditions such as light, initial pH, transition metal ion concentration and PMS dose on the degradation effect of rhodamine B were investigated. The coupling mechanism was proposed based on the free radical scavenging reaction. The experimental results showed that the different transition metals activated PMS in the order of Co2+> Fe2+> Cu2+> Mn2+> Zn2+> Ni2+. In the Fe2+/MoS2/PMS/light system, the Fe2+ concentration ranging from 0.05 mM to 0.2 mM was proportional to the activation PMS efficiency. Free radical burst experiments suggested that ·OH and SO4−· were the main reactive radicals that effectively promoted the degradation of pollutants. Humic acid had an inhibitory effect on the removal of RhB from the MoS2/Fe2+/PMS/light system. Fe2+ completed its own redox cycle (Fe3+/Fe2+) while continuously catalyzing the conversion of Mo species (Mo(VI)/Mo(IV)) in 5 cycles.

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

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

Analysis on combustion kinetics and emission characteristics of disposable paper cups

Most disposable paper cups (DPCs) end up being incinerated like most household waste due to high costs and technical limitations in China. And this has raised concerns due to potential environmental and health hazards. A combination of thermogravimetric analysis, fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS) was employed to analyze the combustion process and identify the emitted gases during DPCs burning in this study. The combustion kinetics were elucidated through the Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods. The physicochemical characterization revealed remarkably high volatile matter (94.51 wt%) and an impressively high heating value of pistachio shell (19.54 MJ/kg). Combustion experiments were conducted in air atmosphere, starting from 30 ℃ to 1000 ℃, at four different heating rates of 10, 20, and 40 K/min. The TG results showed that combustion process of the DPCs included four stages and more than 80% of weight loss occurred at active combustion with temperature of 210–520 ℃, whose reaction mechanism can be described by the P5 model. The activation energies were calculated as 219.79 and 218.56 kJ/mol, respectively. TG-FTIR analysis revealed that CO2, H2O, CO, C = O, C-O and C-H functional group as the main combustion gas products. The relative concentration of the main volatile products was in the order of CO2 > H2O > C = O > aromatic compounds > C-O > CO > C-H according to TG-MS. This study provided a comprehensive understanding of the combustion behavior of DPCs and highlighted the importance of proper waste management to mitigate the environmental impact of DPCs.

Influence of Zinc Substitution on the Structural, Dielectric, and Gas-Sensing Properties of Mg1-xZnxFe2O4 Nanoparticles.

In the present work, Mg1-xZnxFe2O4 (MZFO) nanoparticles with x = 0.0, 0.2, 0.35, and 0.5 were synthesized via a chemical coprecipitation method. The study aimed to explore the effect of substituting Mg with Zn in MZFO on its structural, dielectric, and gas-sensing properties. The spinel phase formation was confirmed using X-ray diffraction, and the morphology of the prepared nanoparticles was revealed using scanning electron microscopy. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the band ranges of 500-600 cm-1 for tetrahedral and 390-450 cm-1 for octahedral lattice sites. The dielectric data showed that Zn substitution in MZFO decreased both the dielectric constant and loss with increasing frequencies and attained a stagnant value at higher frequencies. Furthermore, the gas-sensing characteristics of Zn-substituted spinel ferrites at room temperature for CO2, O2, and N2 were studied. The nanostructured MZFO exhibited high sensitivity in the order of CO2 > O2 ≫ N2 and showed a good response time of (∼1 min) for CO2, demonstrating that MZFO can be a good potential candidate for gas-sensing applications.

Molecular Simulation Study Based on Adsorption of Gas (CO2,O2,CH4) on Coal

This study aimed to further explore the adsorption properties of different gases (CO2, O2, and CH4) on the coking coal surface by establishing a molecular model. Changes in the absolute adsorption capacity and the isosteric heat of adsorption of gases under different temperatures, pressures, and compositions were simulated using grand canonical Monte Carlo (GCMC) and molecular dynamics simulations. Interaction energy and energy distribution were used to analyze the adsorption behavior of gases, and the diffusion properties were investigated using the diffusion coefficient and diffusion activation energy. The absolute adsorption results fit well with the Langmuir–Freundlich model. The absolute adsorption capacity had a significant positive correlation with pressure and the corresponding mole fraction, and a significant negative correlation with temperature. The competitiveness, based on binary adsorption selectivity, was in the order of CO2 > O2 > CH4. The isosteric heat of adsorption of CH4 was slightly higher than that of O2, and that of CO2 was 1.49–1.64 times that of O2 and CH4. The isosteric heat of the adsorption of gases was also barely influenced by temperature and pressure. The interaction energy between CO2 and coal was greater than that of O2 or CH4, but the high pressure and high content were not conducive to the adsorption of O2 by CO2. The preferred adsorption site for CO2 was stronger than that for O2 and CH4, and its peak value negatively correlated with the molar fraction. The diffusion coefficient for single component gases initially increased and then decreased with increased pressure, showing a positive correlation with temperature. A close inverse correlation existed between diffusion activation energy and pressure. These results revealed the microscopic adsorption and diffusion regularities of CO2, O2, and CH4 in the coal model, indicating great significance in accurately predicting coal fires.

Inhibitory effects of typical inert gases on the flame propagation and structures in TiH2 dust clouds

The inhibitory effects of CO2, N2 and Ar on TiH2 dust explosion had been experimentally studied. The results showed that the inhibitory effects of the three inert gases on the flame morphology, propagation velocity and temperature of TiH2 dust explosion were in the order of CO2 > N2 > Ar under the same oxygen concentration. CO2 accelerated the cooling and extinguishing processes of the incomplete burning particles to inhibit the further dehydrogenation and combustion reactions of TiH2 particles. N2 reacted with TiH2 particles and form ternary Ti-O-N solutions on its surface to hinder the binding progress of TiH2 and O2. In the process of Ar dilution, OH radical was adsorbed on the surface of TiH2-x to enhance its surface reactivity. N2 and CO2 mainly inhibited the explosion of TiH2 dust cloud through dilution of O2, cooling and chemical reactions, whereas Ar mainly played the roles of diluting O2 and cooling.

Carbon sink and greenhouse gas emission of dryland vegetation cover in tourism villages in Flores Island, East Nusa Tenggara, Indonesia

Abstract. Lestari F, Tua IN, Muzanni A, Nugroho DF, Wibowo AA, Wartono T, Widanarko B, Saepullah A, Modjo R, Farida M, Erwandi D, Aryani DD, Kadir A, Widiatmoko AI, Hendra, Herwanto ZJ, Tejamaya M, Hamid RA, Fatmah, Gunawan EL, Setyowati DL, Hafids MF, Yuliani R. 2023. Carbon sink and greenhouse gas emission of dryland vegetation cover in tourism villages in Flores Island, East Nusa Tenggara, Indonesia. Biodiversitas 24: 1998-2005. Due to its natural features and scenery, the dryland ecosystem has recently become a tourist destination. One of the growing dryland ecosystems for village tourism is Flores Island, East Nusa Tenggara, Indonesia. Those tourism villages have the potential to promote carbon sequestration through the preservation of natural resources and, at the same time, can release Green-House Gases (GHG). Despite growing research on carbon stock, there is little information on the carbon budget of a dryland tourism village, which includes the values of carbon stock sequestered from the atmosphere and greenhouse gas emissions. This research aimed to measure the carbon stock and GHG emissions in three villages containing paddy fields, savanna, and forest covers. The measured gases, including CO2, CH4, and N2O, were collected using the gas chamber method and analyzed using gas chromatography. The result shows that forest land covers have the highest carbon stock, with average values of 97.44 Mg ha-1 within the 57.34-117.5 Mg ha-1. A low average carbon stock of 17.39 Mg ha-1 was observed in paddy fields. The GHG was in the order of CO2 > CH4 > N2O. The paddy field has higher GHG than other land covers, with average CO2, CH4, and N2O values of 292.45 ppm, 1.35 ppm, and 1.09 ppm. While CO2, CH4, and N2O values for the forest were 281.05 ppm, 1.30 ppm, 1.05 ppm, 272.83 ppm, 1.26 ppm, and 1.02 ppm for savanna covers.

Formula omitted]-antisite disorder driven exchange bias effect and Griffiths-like phase in 25% Sr-doped [formula omitted

The unusual magnetic behaviour and multiple magnetic phases in double perovskite systems mainly originate from B-antisite disorder and various exchange couplings. Here we report the detailed exchange bias study in the hole doped Sm1.5Sr0.5CoMnO6 double perovskite system. The existence of structural antisite-disorder (Co-O-Co-O-Mn or Mn-O-Mn-O-Co) in the system is revealed. The ordering of Co2+ and Mn4+ gives rise to two ferromagnetic transitions, Tc1∼133 K and Tc2∼114 K. A Griffiths-like phase at ∼153 K is identified by the dc magnetization data above the ferromagnetic ordering temperature. The isothermal magnetization measurements further probe the exhibition of the conventional exchange bias effect and training effect phenomena in our sample. Maximum field shift ∼3.43 kOe in exchange bias effect is observed owing to the exchange couplings at the interfaces of FM/AFM at low temperature induced by B-antisite-disorder. In the 64–300 K temperature range, this disordered double perovskite exhibits insulating characteristics with a variable range hopping type of conduction mechanism. We also notice a negative magnetoresistance of −2.74% at 64 K and 60 kOe magnetic field.

The role of surface hydroxyls on ZnZrOx solid solution catalyst in CO2 hydrogenation to methanol

ZnZrOx solid solution catalyst is an excellent catalyst in methanol synthesis from CO2 hydrogenation. It is still highly aspiration to make any further improvement in catalytic performance. In this work, ZnZrOx solid solution catalyst is prepared with different methods, resulting in different surface property. The ZnZrOx solid solution catalyst prepared by reflux ammonia (ZnZrOx-RA) exhibits higher methanol selectivity of 95.2% and CO2 conversion of 3.3% than that of the catalyst obtained via co-precipitation (ZnZrOx-CP) at 280 °C, 5 MPa. Subsequent kinetics analysis shows that ZnZrOx-RA, in comparison to ZnZrOx-CP, shows a decreased activation energy for methanol synthesis, an increased reaction order in H2, and a similar reaction order in CO2. Structural characterizations indicate that these two catalysts are in solid solution state, while ZnZrOx-RA possesses more Zn-OH species on the surface. The surface Zn-OH species enhance the activation and adsorption of CO2 and H2, and improve the generation and stability of HCOO* species, which promote CO2 hydrogenation to methanol.

Kinetic process assessment of H2 purification over highly porous carbon sorbents under multicomponent feed conditions

As a universal energy carrier, the need for pure H2 is ever increasing due to its ubiquitous role in petrochemical refining, metal reduction, and the up-and-coming fuel cell market. Hydrogen produced from steam methane reforming (SMR) is typically laden with impurities such as CO2, CO, and CH4 and a full efficiency screening for potential H2 purification sorbents requires evaluating the thermodynamic and kinetic behaviors associated with multicomponent pressure swing adsorption (PSA). As such, in this study we assessed three commercially available activated carbons with high surface area and pore volume for the PSA upgrading of H2 from simulated SMR off-gas stream consisting of H2/CO/CH4/CO2 (75/5/5/15 vol%). In addition to high-pressure adsorption isotherms for pure gases, H2 purity and recovery, and H2 productivity were estimated from cyclic PSA experiments, while actual (CO + CH4 + CO2)/H2 selectivity values were estimated from breakthrough experiments. For the best performing material, the results demonstrated H2 purity and recovery of 99.6 and 55.3 %, respectively with a productivity of 18.3 molH2/kg.h and multicomponent (CO + CH4 + CO2)/H2 selectivity of 59.86 %. Moreover, the affinity of the different adsorbates toward the activated carbons presented from the most adsorbed to the least adsorbed gas was in the order of CO2 > CH4 > CO ≫ H2. The H2 purification over these carbon-based adsorbents was found to be an equilibrium-controlled process.

Influence of pressure and dilution gas on the explosion behavior of methane-oxygen mixtures

This study investigates the influence of initial pressure (P0) and dilution gas (N2, CO2, He, or Ar) on the explosion behavior of CH4-O2 mixtures. Spherical premixed flames in a 20 L spherical vessel are recorded by high-speed schlieren photography. The explosion parameters, explosion duration (τe), maximum explosion pressure (Pmax), maximum explosion pressure change rate ((dP/dt)max), flame speed, burning velocity, and Markstein length, are experimentally investigated at various pressures up to 250 kPa and at room temperature (280 ± 3 K). The experimental results show that Pmax and (dP/dt)max increase linearly with P0. The influence on the explosion intensities, (dP/dt)max, and flame speed, from high to low with the dilution is in the order of CO2, N2, Ar, and He, which indicates that CO2 and N2 more significantly inhibit CH4-O2 explosion. The results suggest that CO2 not only has a strong endothermic ability and reacts with H, but also changes the active free radicals to molecules due to three-element collision. The experimental phenomena are explained and validated by the results from the Chemkin package using two detailed mechanisms, indicating that (dP/dt)max is closely related to the content of H, O, OH, and CH3. The cellular instability is analyzed by the flame thickness and Markstein length, and it becomes more obvious as the flame thickness and Markstein length decrease. The buoyancy instability, Rayleigh-Taylor instability, and a series of phenomena due to the dilution of CO2 are analyzed. The maximum explosion pressure and flame speed decrease significantly with the addition of CO2 into CH4-air mixtures, and CO2 affects the generation of flame. The buoyancy instability of CH4-air mixtures with CO2 addition is examined. The experimental results contribute to a deeper understanding of the explosion behavior of CH4-O2 mixtures and the dilution effect of other gases on it.

Effect of the Iron Component on Microcrystalline Structure Evolution of Hydrochloric Acid-Demineralized Lignite during the Pyrolysis Process.

Hydrochloric acid-demineralized Shengli lignite (SL+) and iron-added lignite (SL+-Fe) were thermally degraded using a fixed-bed device to better understand the effect of the iron component on the microcrystalline structure transformation properties of lignite during the pyrolysis process. The primary gaseous products (CO2, CO, H2, and CH4) were detected by pyrolysis–gas chromatography. X-ray diffraction and Raman spectra were adopted to analyze the microcrystalline structure of lignite and chars. The results indicated that the iron component had a catalysis effect on the pyrolysis of SL+ below 602.6 °C. The pyrolysis gases released in the order of CO2, CO, H2, and CH4, and the addition of the iron component did not change the sequences. The iron component promoted the generation of CO2, CO, and H2 in the low-temperature stage. During the high-temperature stage, the iron component inhibited the formation of CO and H2. The formation of CH4 was inhibited by the iron component throughout the pyrolysis process. The evolution characteristics of −OH, C=O, C=C, and C–H functional groups were not significantly affected, and the fracture of aliphatic functional groups and C–O functional groups was inhibited by the iron component during the pyrolysis process. The iron component restricted the spatial regular arrangement tendency of aromatic rings and facilitated the decrease in the small-sized aromatic ring but inhibited the formation of large aromatic rings (≥6 rings) and the content decrease in side chains during the pyrolysis process. Notably, the effects of the iron component on the formation of gaseous products were associated with the microstructure evolution of lignite.

Determination of diffusivities of triolein in pressurized liquids and in supercritical CO2

Pressurized liquid extraction and supercritical fluid extraction are attracting attention. The accurate design and scale-up of these processes need the knowledge of transport property, namely, diffusion coefficients. In this study, the measurements of diffusion coefficients D12 of triolein with a high molecular weight were carried out in pressurized fluids with different viscosities. The D12 values in various pressurized liquids of ethanol, methanol, and hexane were determined by the Taylor dispersion method at 298.15 to 323.15 K and pressures of 1.00 to 12.08 MPa. We found that the D12 data in supercritical CO2 cannot be accurately measured by the Taylor dispersion method because the response peaks of triolein in supercritical CO2 obtained by the Taylor dispersion method were severe tailing. However, the tailings were significantly improved by using the chromatographic impulse response method. Therefore, the D12 values in supercritical CO2 were measured by the chromatographic impulse response method at 303.15 to 333.15 K and pressure up to 31.02 MPa. The magnitude of determined D12 of triolein in fluids is in the order of CO2 > hexane > methanol > ethanol. The D12 increased from 0.306 × 10−9 m2 s−1 at 298.15 K and 10.00 MPa in liquid ethanol to 6.323 × 10−9 m2 s−1 at 333.15 K and 13.77 MPa in supercritical CO2. All the diffusivity data of triolein measured in CO2, hexane, methanol, and ethanol in this study can be satisfactorily represented by the hydrodynamic equation over a wide range of fluid viscosity of 37 to 1179 μPa s from liquid to supercritical states.

Assessment of household air pollution exposure of tribal women

There is a growing evidence that the burning of unprocessed biomass fuels is associated with adverse health impacts. This study estimated the gaseous pollutants (CO, CO2, O3, SO2, and NO2) and particulate matters (PM2.5 and PM10) during the burning of biomass and liquefied petroleum gas (LPG) fuels and their impacts on the health of tribal women. The results revealed that the tribal women mainly used six types of unprocessed biomass fuels (dry leaves, cow dung cake, dry woods, twigs, rice straw, and agricultural residues) along with five types of traditional earthen stoves. The concentration of gaseous and PM was recorded as in the order of CO2 > SO2 > CO > O3 and total suspended particulate matter (TSPM) > PM10 > PM2.5, respectively. The pollutant concentration inside the kitchen room for biomass users was significantly (p < 0.001) higher than LPG users. The biomass using tribal women might be suffering from higher cardiovascular risk than LPG users. The lung function study results also indicated that the mean values of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1/FVC were lower among biomass users than LPG users. The correlation study shows that tribal women who were exposed to biomass smoke were in a more vulnerable position than those who used LPG. Moreover, the toxicological risk among tribal biomass users was observed high (3.52) compared to LPG users (0.39). On the other hand, the Monte Carlo probabilistic simulation model for uncertainty analysis revealed that the mean value of Hazard Quotient (HQ) for PM2.5 in kitchen room was observed as 4.31E-00 and 9.40E-01 for biomass and LPG users, respectively. Modelling study also revealed that exposure of duration and cooking time are extremely important for toxicological risk assessment. However, further long-term comprehensive studies are extremely important.

Products distribution and hazardous elements migration during pyrolysis of oily sludge from the oil refining process

Oily sludge is a hazardous waste due to the enrichment of nitrogen, sulfur, PAHs, and heavy metals. In this work, an oily sludge from oil refining factory was pyrolyzed at various temperatures of 250–850 °C in a fixed bed reactor focusing on product distribution and migration of hazardous compounds of PAHs, sulfur, nitrogen-containing compounds, and heavy metals. The mechanism of PAHs formation and migration of nitrogen, sulfur, heavy metals were elucidated by comprehensive analysis of the solid, liquid, and gas products. The distribution and risk analysis of heavy metals were also conducted. The pyrolytic products distribution was markedly affected by pyrolysis temperatures. A maximum oil yield was observed at 500 °C, which can further crack into gas due to secondary reaction. The pyrolytic gas was enriched in the order of CO2 > CO > CH4 > H2. At lower temperatures, CO2 was largely generated due to the elimination of oxygen-containing functional groups, while H2 was mainly formed above 450 °C due to the recombination reaction. Higher temperatures promoted more N-/S-containing compounds into tar and gas phases. The N-/S-containing compounds mainly included NH3, HCN, H2S, SO2, COS in the gas phase and amines, indoles, pyridines, nitriles, thiophenes in liquid phase. PAHs with 2-ring to 5-ring were mainly generated due to the secondary reaction at higher temperatures. Moreover, Pyrolysis caused the accumulation of heavy metals in chars. Cd presented a high potential risk while the other heavy metals in chars presented a low risk.

Nature of Griffiths phase and ferromagnetic 3d-4f interaction in double-perovskite Dy2CoMnO6

Double perovskites Dy2CoMnO6 (DCMO) was synthesized by a sol-gel method and the structure and magnetic properties were systematically investigated. Both X-ray diffraction and Raman spectrum indicate that double pervoskite DCMO has a monoclinic structure with a space group P21/n. A Griffiths phase is confirmed to be existing in DCMO by the magnetic behaviors, which is significantly different from the behaviors of the non-Griffiths phase of Gd2CoMnO6 (GCMO) recently reported in reference. It is suggested that the origins of the different short-range magnetic orders of them can be attributed to the different 3d-4f exchange interactions in DCMO and GCMO, besides the effect of the unavoidable anti-site disorder, interrupting the long-range ferromagnetic (FM) order of Co2+-O-Mn4+, resulting in the formation of short-range FM order. The effects of A-site rare-earth Re3+ ions on the magnetism of double perovskite Re2Co(Ni)MnO6 are dominated by the combining and competing functions of the radius and the moments of rare earth ions (or the 3d-4f exchange interactions). The FM/AFM coupling is not only related to the most outer 4f electrons of the rare earth ions, but also to the inner 5d/6s orbital electrons.

Molecular insight into the oil displacement mechanism of gas flooding in deep oil reservoir

Gas flooding has become one important development method for deep reservoir. In this work, employing molecular dynamic simulation method, the displacement behavior of nanoslit oil by injected gases (CO2, CH4, N2, C3H8) was investigated. Simulation results indicate that the injected gases exhibit great advantage in deep reservoir than that in medium-shallow reservoir, the displacement capability follows order of CO2 > C3H8 > CH4 > N2. The dissolubility of gas, adsorption strength of oil, and detachment capability of injected gas play crucial roles in displacement performance. Our work highlights the effect of gas types on displacement performance, which is significant for the development of deep oil reservoirs.