The CO_2 absorption and desorption performance of the triethylenetetramine + N,N-diethylethanolamine + H_2O system

Post-combustion CO_2 capture(PCC) process faces significant challenge of high regeneration energy consumption.Biphasic absorbent is a promising alternative candidate which could significantly reduce the regeneration energy consumption because only the CO_2-concentrated phase should be regenerated. In this work, aqueous solutions of triethylenetetramine(TETA) and N,N-diethylethanolamine(DEEA) are found to be efficient biphasic absorbents of CO_2. The effects of the solvent composition, total amine concentration, and temperature on the absorption behavior, as well as the effect of temperature on the desorption behavior of TETA–DEEA–H2 O system were investigated. An aqueous solution of 1 mol·L-1 TETA and 4 mol·L-1 DEEA spontaneously separates into two liquid phases after a certain amount of CO_2 is absorbed and it shows high CO_2 absorption/desorption performance.About 99.4% of the absorbed CO_2 is found in the lower phase, which corresponds to a CO_2 absorption capacity of 3.44 mol·kg-1. The appropriate absorption and desorption temperatures are found to be 30 °C and 90 °C,respectively. The thermal analysis indicates that the heat of absorption of the 1 mol·L-1 TETA and 4 mol·L-1 DEEA solution is-84.38 kJ·(mol CO_2)-1 which is 6.92 kJ·(mol CO_2)-1 less than that of aqueous MEA. The reaction heat, sensible heat, and the vaporization heat of the TETA–DEEA–H2 O system are lower than that of the aqueous MEA, while its CO_2 capacity is higher. Thus the TETA–DEEA–H2 O system is potentially a better absorbent for the post-combustion CO_2 capture process.

Metal-Oxo Cluster Catalysts for Photocatalytic Water Splitting and Carbon Dioxide Reduction

Photocatalytic water splitting and carbon dioxide photoreduction are considered eff ective strategies for alleviating the energy crisis and environmental pollution.Polynuclear metal-oxo clusters possess excellent electron storage/release ability and unique catalytic properties via intermetallic synergy,which enables them with great potential in environmentally friendly photosynthesis.Importantly,metal-oxo clusters with precise structure can not only act as high-effi ciency catalysts but also provide well-defi ned structural models for exploring structure-activity relationships.In this review,we systematically sum-marize recent progress in the catalytic application of polynuclear metal-oxo clusters,including polyoxometalate clusters,low-cost transition metal clusters,and metal-oxo-cluster-based metal-organic frameworks for water splitting and CO_(2)reduction.Furthermore,we discuss the challenges and solutions to the problems of polynuclear metal-oxo clusters in photocatalysis.

Production of glycerol carbonate using crude glycerol from biodiesel production with DBU as a catalyst

The biodiesel production technology catalyzed by 1,8-diazabicycloundec-7-ene(DBU)is developed in this work.Crude glycerol containing DBU and DBU/glycerol/CO_2(DGC)ionic compounds reacts directly with dimethyl carbonate(DMC)to produce high value-added glycerol carbonate(GC)catalyzed by DBU and DGC.The catalytic performance of DBU and DGC,as well as the kinetics of the reaction catalyzed by DBU,were investigated.The results show that DGC has a weak catalytic effect on the transesterification of glycerol and DMC.When the temperature is higher than 60°C,DGC catalyzes the reaction jointly with DBU,which is produced from the decomposition of DGC.DBU has a good catalytic effect on the reaction between glycerol and DMC,with 90%conversion of glycerol and 84%selectivity to GC under the following conditions:DMC-to-glycerol molar ratio of 3:1,4.0%DBU(based on glycerol mass),reaction time of 60 min,and reaction temperature of 40°C.The apparent kinetics results show that the activation energies are 30.95 kJ·mol^(-1)and 55.16 kJ·mol^(-1)for the forward and reverse GC generation reactions,respectively,and the activation energy of the decomposition reaction of GC to glycidol(GD)is 26.58 kJ·mol^(-1).

Static and dynamic characteristics of SO_(2)-O_(2) aqueous solution in the microstructure of porous carbon materials

Porous carbon material facilitates the reaction SO2+O2+H2O!H2SO4 in coal-burned flue gas for sulfur resources recovery at mild conditions.It draws a long-term mystery on its heterogeneous catalysis due to the complicated synergic effect between its microstructure and chemical components.To decouple the effects of geometric structure from chemical components,classical molecular dynamics method was used to investigate the static and dynamic characteristics of the reactants(H2O,SO2 and O2)in the confined space truncated by double-layer graphene(DLG).Strong adsorption of SO2 and O2 by the DLG was observed,which results in the filling of the solute molecules into the interior of the DLG and the depletion of H2O.This effect mainly results from the different affinity of the DLG to the species and can be tuned by the separation of the two graphene layers.Such dimension dependence of the static and dynamic properties like distribution profile,molecular cluster,hydrogen bond and diffusion coefficient were also studied.The conclusions drawn in this work could be helpful to the further understanding of the underlying reaction mechanism of desulfurization process in porous carbon materials and other applications of carbon-based catalysts.

Growth of Ag/g-C_(3)N_(4) nanocomposites on nickel foam to enhance photocatalytic degradation of formaldehyde under visible light

Formaldehyde is a pollutant that significantly affects the indoor air quality.However,conventional remediation approaches can be challenging to deal with low-concentration formaldehyde in an indoor environment.In this study,Photocatalysts of Ag/graphitic carbon nitride(g-C_(3)N_(4))/Ni with 3D reticulated coral structure were prepared by thermal polymerization and liquid phase photo-deposition,using nickel foam(NF)as the carrier.Experiments demonstrated that when the Ag concentration was 3%,and the relative humidity was 60%,the Ni/Ag/g-C_(3)N_(4)showed the maximum degradation rate of formaldehyde at 90.19%under visible light irradiation,and the formaldehyde concentration after degradation was lower than the Hygienic standard stated by the Chinese Government.The porous structure of Ni/Ag/g-C_(3)N_(4)and the formation of Schottky junctions promoted the Adsorption efficiency and degradation of formaldehyde,while the nickel foam carrier effectively promoted the desorption of degradation products.Meanwhile,the degradation rate was only reduced by3.4%after 16 recycles,the three-dimensional porous structure extended the lifetime of the photocatalyst.This study provides a new strategy for the degradation of indoor formaldehyde at low concentrations.

CO2 absorption performance in a rotating disk reactor using DBU-glycerol as solvent

Gas–liquid mass transfer of rotating disk reactor was studied in CO2 absorption using 1,8-diazabicyclo-[5.4.0]-undec-7-ene(DBU)-glycerol solution as solvent. Effects of the rotating disk structure and various operation parameters on the CO2 absorption rate and CO2 removal efficiency were investigated. The rotating disk with optimal holes is conducive to mass transfer of CO2 and the formation of thin liquid film at the opening increases the gas–liquid contact area. With the increase of rotating speed, the liquid flow pattern on the rotating disk surface changes from thin film flow to separated streams and creates extra liquid lines attached to the rim of the disk,which leads to a very complicated change on the CO2 absorption rate and CO2 removal efficiency. The overall gas-phase mass transfer coefficient increases 138% as the rotating speed increasing from 250 to 1400 r·min^-1.Increasing temperature from 298 to 338 K can enhance the CO2 absorption rate due to lowering the viscosity of the solvent. The rate-determined step for the absorption is focused on the gas side. The rotating disk reactor can effectively enhance the absorption of CO2 with viscous DBU-glycerol solvents.

Jatropha curcas L. oil extracted by switchable solvent N, N-dimethylcyclohexylamine for biodiesel production

Biodiesel, which is a renewable and environmentally friendly fuel, has been studied widely to help remedy increasing environmental problems. One of the key processes of biodiesel production is oil extraction from oilseed materials. Switchable solvents can reversibly change from molecular to ionic solvents under atmospheric CO_2,and can be used for oil extraction. N, N-dimethylcyclohexylamine(DMCHA), a switchable solvent, was used to extract oil from Jatropha curcas L. oil seeds to produce biodiesel. The appropriate extraction conditions were:1:2 ratio of seed mass to DMCHA volume, 0.3–1 mm particle size, 200 r·min-1agitation speed, 60 min extraction time, and 30 °C extraction temperature. The extraction ratio was about 83%. This solvent extracted the oil more efficiently than hexane, and is much less volatile. By bubbling CO_2 under 1 atm and 25 °C for 5 h, the oil was separated, and DMCHA was recovered after releasing CO_2 by bubbling N_2 under 1 atm and 60 °C for 2 h. The residual solvent content in oil was about 1.7%. Selectivity of DMCHA was evaluated by detecting the protein and sugar content in oil. Using the oil with residual solvent to conduct transesterification process, the oil conversion ratio was approximately 99.5%.

Natural siderite derivatives activated peroxydisulfate toward oxidation of organic contaminant: A green soil remediation strategy

Natural siderite(FeCO_(3)),simulated synthetic siderite and nZVI/FeCO_(3) composite were used as green and easily available iron-based catalysts in peroxydisulfate activation for remediating 2-chlorophenol as the target contaminant and this technique can effectively degrade organic pollutants in the soil.The key reaction parameters such as catalysts dosage,oxidant concentration and pH,were investigated to evaluate the catalytic performance of different materials in catalytic systems.The buffering property of natural soil conduced satisfactory degradation performance in a wide pH range(3-10).Both the main non-radical of ^(1)O_(2) and free radicals of SO_(4)^(-) and OH·were evidenced by quenching experiment and electron paramagnetic resonance.The reduction of nZVI on FFC surface not only has the advantage for electronic transfer to promote the circulation of Fe(Ⅲ)to Fe(Ⅱ),but also can directly dechlorinate.Furthermore,the intermediates were comprehensively analyzed by GC-MS and a potential removal mechanism of three oxidant system for 2-CP soil degradation was obtained.Briefly,this research provides a new perspective for organic contaminate soil treatment using natural siderite or simulated synthetic siderite as efficient and environmental catalytic material.

DBU/CH_3OH/CO_2转极性离子化合物的合成与表征（英文）

Switchable ionic compounds have wide applications in chemical processes.A switchable ionic compound based on 1,8-diazabicyclo-[5.4.0]-undec-7-ene(DBU),CH_3OH and CO_2 was synthesized and characterized.DBU/CH_3OH/CO_2 ionic compound was prepared in the presence of excess methanol,and then the excess methanol was removed by reduced pressure distillation in CO_2 atmosphere.The product yield(100%) reached the theoretical maximum for the first time.Its structure was identified by NMR,FT-IR,and XRD.The crystal product shows 8strong peaks in XRD at 2θ values of 16.0547°,16.4308°,16.7651°,18.8714°,19.2140°,21.9471°,22.0780°,and25.5661°.Its decomposition onset temperature(53 ℃) was affirmed by TGA,which is lower than its melting point.And its ionic switch point was measured by conductivity.

One-pot synthesis of SrTiO_(3)-SrCO_(3) heterojunction with strong interfacial electronic interaction as a novel photocatalyst for water splitting to generate H_(2)

Photocatalytic hydrogen evolution from water splitting is a promising strategy for realizing the vision of carbon neutrality.Herein,a novel SrTi O_(3)-SrCO_(3)n-n heterojunction was used for the first time for water splitting to generate H_(2).The heterojunction was synthesized by a soft chemical one-pot hydrothermal method.The Sr TiO_(3)-SrCO_(3)loading with 3 wt%Pt shows the maximum photocatalytic H_(2)evolution rate of3.62 mmol h^(-1)g^(-1)under simulated sunlight irradiation,which is 20.1 times higher than that of pristine SrTiO_(3).The apparent quantum efficiency of Sr TiO_(3)-SrCO_(3)reaches 21.73%at 313 nm,and it shows good stability during cyclic experiment.The formation of compact Sr TiO_(3)-SrCO_(3)heterojunction with strong interfacial electronic interaction promotes the transmission and separation of photo-generated carriers.The results of XPS,PL,PC,EIS and DFT support the mechanism of improving photocatalytic activity based on carrier dynamics.This work provides a facile and effective method to enhance the activity of Sr Ti O_(3)-based heterojunction photocatalysts.

Thin-film composite forward osmosis membranes with substrate layer composed of polysulfone blended with PEG or polysulfone grafted PEG methyl ether methacrylate

To advance commercial application of forward osmosis （FO）, we investigated the effects of two additives on the performance of polysulfone （PSf） based FO membranes： one is poly（ethylene glycol） （PEG）, and another is PSf grafted with PEG methyl ether methacrylate （PSf-g-PEGMA）. PSf blended with PEG or PSf-g- PEGMA was used to form a substrate layer, and then polyamide was formed on a support layer by interfacial polymerization. In this study, NaC1 （1 mol·L^-1） and deionized water were used as the draw solution and the feed solution, respectively. With the increase of PEG content from 0 to 15 wt-%, FO water flux declined by 23.4% to 59.3% compared to a PSf TFC FO membrane. With the increase of PSf-g-PEGMA from 0 to 15 wt-%, the membrane flux showed almost no change at first and then declined by about 52.0% and 50.4%. The PSfwith 5 wt-% PSf-g-PEGMA FO membrane showed a higher pure water flux of 8.74 L·m^-2·h^-1 than the commercial HTI membranes （6-8 L·m^-2·h^-1） under the FO mode. Our study suggests that hydrophobic interface is very important for the formation ofpolyamide, and a small amount of PSf- g-PEGMA can maintain a good condition for the formation of polyamide and reduce internal concentration polarization.

Effect of doped strontium on catalytic properties of La_(1-x)SrxMnO_(3) for rhodamine B degradation

A series of La_(1-x)Sr_(x)MnO_(3) samples were prepared by sol-gel method and used to degrade rhodamine B(RhB) in water.All samples were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),N_(2) adsorption-desorption,temperature-programmed reduction of H_(2)(H_(2)-TPR) and temperature-programmed desorption of O_(2)(O_(2)-TPD).The results show that the degradation of RhB is highly dependent on the initial pH value of solution.Sr doping enhances the degradation ability of LaMnO_(3) for RhB in the time range of 0-40 min under a strong acidic environment,but all samples exhibit similar degradation rate from 40 to 60 min.In La_(0.7)Sr_(0.3)MnO_(3)-RhB reaction system,there are two different degradation pathways,including N-de-ethylation,chromophore cleavage,ring-opening and mineralization.La_(1-x)Sr_(x)MnO_(3)(x ≤0.3) has the perovskite structure of La-Mn oxides,while La_(0.6)Sr_(0.4)MnO_(3) exhibits a Sr_(0.4)MnLa_(0.6)O_(2).98 perovskite phase.Sr doping leads to distortion of rhombohedral crystal structure and increases the relative content of Mn^(4+).The perovskite structure is stable in strong acidic environment during RhB degradation,but the relative content of Mn^(4+)and Mn^(3+) on the material surface changes.Sr doped LaMnO_(3) achieves specific surface area of 58.8 m^(2)/g and total pore volume of 0.152 cm^(3)/g.Furthermore,Sr^(2+)doping improves redox properties of La-Mn oxides,and the presence of defects makes oxygen diffusion easier compared with the undoped samples.

PVDF ultrafiltration membranes of controlled performance via blending PVDF-g-PEGMA copolymer synthesized under different reaction times

Polyvinylidene fluoride grafted with poly（ethylene glycol） methyl ether methacrylate （PVDF-g- PEGMA） was synthesized using atomic transfer radical polymerization （ATRP） at different reaction times （9 h, 19 h, and 29 h）. The corresponding conversion rates were 10%, 20% and 30%, respectively. PVDF was blended with the copolymer mixtnre containing PVDF-g-PEGMA, solvent and residual PEGMA under different reaction times. In this study, we explored the effect of the copolymer mixture additives with different synthesis times on cast membrane performance. Increasing the reaction time of PVDF-g-PEGMA causes more PVDF-g-PEGMA and less residual PEGMA to be found in the casting solution. Incremental PVDF-g-PEGMA can dramatically increase the viscosity of the casting solution. An overly high viscosity led to a delayed phase inversion, thus hindering PEGMA segments in PVDF- g-PEGMA from migrating to the membrane surface. However, more residual PEGMA contributed to helping rnore PEGMA segments migrate to the membrane surface. The pure water fluxes of the blended membrane with reaction times of 9 h, 19 h, and 29 h are 5445 L. m 2.h I 1068 L- m 2.h land 1179 L.m 2.h I respectively, at 0.07 MPa. Delayed phase inversion can form smaller surface pore size distributions, thus decreasing the water flux for the membranes with PVDF-g-PEGMA at 19 h and 29 h. Therefore, we can control the membrane pore size distribution by decreasing the reaction time of PVDF-g-PEGMA to obtain a better flux performance. The membrane with PVDF-g-PEGMA at 19 h exhibits the best foulant rejection and cleaning recovery due to its narrow pore size distribution and high surface oxygen content.