Herein, a selective tandem C–C bond-forming reaction with CO2 was developed to realize the bridging of enaminones and synthesis of 1,4-dihydropyridines, respectively. n-Butylamine significantly ...promoted this CO2 deoxymethylenation procedure catalyzed by 1,5,7-triazabicyclo4.4.0dec-5-ene (TBD) and ZnCl2. The mechanism involving the formation of bis(silyl)acetal, nucleophilic addition, and amine elimination was also interpreted to clarify the bridging of two molecules of enaminones with CO2 and the generation of dihydropyridine derivatives.
Conversion of the abundant agricultural residual cotton stalk (CS) into useful chemicals or functional materials could alleviate the fossil fuels caused energy shortages and environmental crises. ...Although some advances have been achieved, less attention has been paid to the plant tissues effect. In this study, the plant tissue of CS was changed by part degradation of some components (hemicelluloses and lignin, for example) with the aid of acid/base (or both). The pretreated CS was transformed into hydrochar by hydrothermal carbonization (HTC) method. Morphological and chemical compositions of CS hydrochar were analyzed by various techniques, including elemental analysis, Fourier transform infrared (FTIR), BET analysis, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Methylene blue (MB) removal of prepared CS hydrochar was used to evaluate CS hydrochar pollutions adsorption capacity. Results reveal acid/base (or both) pretreatment is beneficial for CS raw material to prepare high-quality CS hydrochar. The effects of some parameters, such as initial MB concentration, temperature, pH value and recyclability on the adsorption of MB onto both acid and base-pretreated CS hydrochar (CS-H
2
SO
4
+ NaOH-HTC) were studied. The present work exhibits the importance of agricultural waste biomass material plant tissues on its derived materials, which will have a positive effect on the direct utilization of waste biomass.
Surfactants and nanoparticles play crucial roles in controlling the oil-water interfacial phenomenon. The natural oil-wet mineral nanoparticles that exist in crude oil could remarkably affect ...water-oil interfacial characteristics. Most of recent studies focus on the effect of hydrophilic nanoparticles dispersed in water on the oil-water interfacial phenomenon for the nanoparticle enhanced oil recovery. However, studies of the impact of the oil-wet nanoparticles existed in crude oil on interfacial behaviour are rare. In this study, the impacts of Span 80 surfactant and hydrophobic SiO2 nanoparticles on the crude oil-water interfacial characteristics were studied by measuring the dynamic and equilibrium crude oil-water interfacial tensions. The results show the existence of nanoparticles leading to higher crude oil-water interfacial tensions than those without nanoparticles at low surfactant concentrations below 2000 ppm. At a Span 80 surfactant concentration of 1000 ppm, the increase of interfacial tension caused by nanoparticles is largest, which is around 8.6 mN/m. For high Span 80 surfactant concentrations, the less significant impact of nanoparticles on the crude oil-water interfacial tension is obtained. The effect of nanoparticle concentration on the crude oil-water interfacial tension was also investigated in the existence of surfactant. The data indicates the less significant influence of nanoparticles on the crude oil-water interfacial tension at high nanoparticle concentration in the presence of Span 80 surfactant. This study confirms the influences of nanoparticle-surfactant interaction and competitive surfactant molecule adsorption on the nanoparticles surfaces and the crude oil-water interface.
Two kinds of Al2O3 ceramic samples with and without Al film deposited were designed respectively. The influences of temperature and high kinetic energy sputtering particles on the wettability and ...interface strength of Al/Al2O3 were studied by comparing the wetting behavior of molten aluminum on two samples. The results show that molten aluminum does not wet the Al2O3 sample without Al film deposited at 700 °C, the contact angle is 165°, and the interfacial shear strength is 28 MPa. With the increase of temperature, the contact angle decreases continuously, and the interface shear strength gradually increases. The fracture of the brazed joint is transferred from the interface to the brazing seam. In comparison, the sample deposited with Al film is wetted by molten aluminum at 700 °C, and the contact angle is only 12°. The interface shear strength is about 120 MPa and is less affected by temperature. The shear fracture of the joint occurs in the brazed seam of Al metal. Therefore, the high energy generated by either the temperature increase or the particle sputtering enable the Al atoms to overcome the energy barrier to form Al–O bonds with the O atoms on the Al2O3 ceramic surface, thereby improving the wettability of Al/Al2O3.
•We achieved continuous separation by dissolution, hydrate formation, and dissociation.•The continuous separations of various gas mixtures were conducted in THF solution.•We measured the ...concentration and refractive index of THF solution.•The dissolved quantities of gas mixtures in THF solution were calculated by UniSim.
Hydrate separation technology has been widely applied to the separation of various gas mixtures with its own unique advantages over the past several decades. However, so far the relevant studies seem to be elementary and exploratory, and most of the separation processes are batch-type and not appropriate of practical uses. To promote the development of hydrate separation technology and to realize its industrial application early, we systematically investigated the continuous separation of CH4–N2, CH4–H2 and CO2–N2 gases respectively by hydrate method using 6mol% tetrahydrofuran (THF) solution as the liquid medium in this work. The results demonstrate that the continuous process of sequential hydrate formation and dissociation can be achieved in the presence of THF under appropriate temperatures and pressures, and the gas mixtures can be separated to some extent after liquid absorption and hydration reaction. The continuous separation process in this work provides an achievable approach for the application of hydrate separation method.
In order to reduce the emission of coal bed methane mixed with air (can be regarded as a CH4 and N2 mixture), which will be helpful to adequately utilize the natural resources and protect ...environment, the separation of CH4 and N2 via hydrate formation in tetra-n-butylammonium bromide (TBAB) solution was systematically studied in this work. The CH4−N2 hydrate formation conditions were determined in TBAB solution first, and then the separation experiments were carried out in TBAB and TBAB−sodium dodecyl sulfate (SDS) solution, respectively. The experimental results show that CH4 and N2 form a hydrate much easier after adding TBAB to water. The composition of CH4 in the hydrate after single-stage equilibrium separation in TBAB solution can be increased from 46.25 mol % to 67.86 mol %. At the same conditions, the composition of CH4 after separation in TBAB−SDS solution is 68.66 mol % and the reaction time shortens greatly. Besides, the recovery of CH4 is more than 47%, and the gas storage capacity of hydrate is 19−21 m3/m3. Higher composition and recovery of CH4 are expected to be obtained if multistage separation is applied. It indicates that CH4 can be concentrated effectively from CH4 and N2 via hydrate formation in TBAB solution. Since the hydrate separation technology can substantially avoid the explosion problem caused by CH4 and on the basis of the results obtained in this work, we may say that this technology is quite suitable for the separation of coal bed methane mixed with air and has broad prospects for industrial applications.
A smoothing localization method for Global Navigation Satellite System (GNSS) and visual Simultaneous Localization and Mapping (SLAM) system is proposed to identify GNSS spoofing, optimize the ...cumulative error of the GNSS/visual SLAM system, and obtain smoothing localization results. The proposed method analyzes the joint error distribution of the GNSS/visual SLAM system, uses the visual frame to invert the relative error offset of the GNSS from the dimensions of time and localization, performs error analysis and mutual verification based on the verification threshold. According to the mutual verification results, the GNSS spoofing is identified, and the corresponding back-end optimization strategy is selected to obtain a smoothing localization result. Through simulation, the time verification threshold and localization verification threshold of the proposed method are obtained under the condition that the sensors frequency and accuracy are set. The KITTI datasets in rural and urban scenes are used for verification. The simulation results show that our method can identify GNSS spoofing and provide credible and smoothing localization results in the case of GNSS spoofing occurs.
Hydrate-based technologies (HBTs) have high potential in many fields. The industrial application of HBTs is limited by the low conversion rate of the water into hydrate (RWH), and sodium lignin ...sulfonate (SLS) has the potential to solve the above problem. In order to make the HBTs in the presence of SLS applied in industry and promote the advances of commercial HBTs, the effect of SLS on the thermodynamic equilibrium hydrate formation pressure (Peq) was investigated for the first time, and a new model (which can predict the Peq) was proposed to quantitatively describe the thermodynamic effect of SLS on the hydrate formation. Then, the effects of pressure and initial SLS concentration on the hydrate formation rate (rR) at different stages in the process of hydrate formation were investigated for the first time to reveal the kinetic effect of SLS on hydrate formation. The experimental results show that SLS caused little negative thermodynamic effect on hydrate formation. The Peq of the ethylene-SLS solution system predicted by the model proposed in this work matches the experimental data well, with an average relative deviation of 1.6% and a maximum relative deviation of 4.7%. SLS increased RWH: the final RWH increased from 57.6 ± 1.6% to higher than 70.0% by using SLS, and the highest final RWH (77.0 ± 2.1%) was achieved when the initial SLS concentration was 0.1 mass%. The rR did not significantly change as RWH increased from 35% to 65% in the formation process in the presence of SLS. The effect of increasing pressure on increasing rR decreased with the increase in RWH when RWH was lower than 30%, and the difference in pressure led to little difference in the rR when RWH was higher than 30%.
C8min BF4 was used in this work to combine with TBAB or THF for the investigation about thermodynamic and kinetic additives on CO2 and CH4/CO2 hydrates. The results show that C8min BF4 has the ...inhibition effect on the equilibrium of hydrate formation. About the kinetic study, C8min BF4 could improve the rate of CO2 hydrate formation and increase the gas uptake in hydrate phase. At the same time, the combination of TBAB and C8min BF4 could increase the mole friction of CH4 in residual gas comparing with the data in THF solution. CH4 separation efficiency was strongly enhanced. Since that the size of CO2 and CH4 molecules are similar, CH4 and CO2 could form the similar hydrate, so the recovery of CH4 from biogas decreases lightly. The CH4 content in biogas can purified from 67 mol% to 77 mol% after one-stage hydrate formation. In addition, the combination of THF and C8min BF4 do not have obvious promoting effect on CH4 separation comparing with the gas separation results in pure THF solution.
Because of the technology limitation and safety requirement, a large amount of air-mixed coal bed methane is released directly to the atmosphere. It leads to severe waste of resources and exacerbates ...the greenhouse effect. This work tries to alleviate this problem by separating CH4 from a mixture of CH4 and N2 via hydrate separation method. Several experiments were systematically carried out in 6 mol % tetrahydrofuran (THF) solution to separate CH4/N2 gas mixtures containing 4.90 to 71.23 mol % CH4. The results that THF can significantly reduce the formation pressure of CH4–N2 hydrate materialize the possibility of separating CH4 and N2 using hydrate separation technology in industrial scale. CH4 can be separated effectively from CH4/N2 mixture and concentrated in hydrate phase with the presence of THF. The recovery of CH4 ranges from 34.06% to 58.16% and the separation factor is between 2.29 and 5.17. A two-stage separation process of 46.28 mol % CH4/53.72 mol % N2 with recycle is designed to increase the recovery of CH4. The calculated results indicate that CH4 concentration in hydrate gas could reach 82.61 mol % with a recovery yield of 47.28%. Hydrate separation technology is an effective way to process and utilize the air-mixed coal bed methane. Multistage separation process does have wide application prospects.
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