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Highlights: [•] Solid acid catalysts reduce both the size of stripper and heat duty simultaneously. [•] Tertiary amine splits the free energy barrier for regeneration to small achievable steps. [•] Bicarbonates with tertiary amines split the free energy into even much smaller steps. [•] Solid Lewis acid catalyst replaces the role of HCO3 − ions especially in HCO3 − depleted regions. [•] Solid Brϕnsted acid catalyst provides protons which aid carbamate breakdown. [Copyright &y& Elsevier]

Newprocedures were developed for our recently developed 1D NMRcalibration method for quantitative liquid phase speciation analysisof a complex quaternary CO2loaded blended amine solutionsuch as MEA–DEAB–CO2–H2O at high and low temperatures respectively representing CO2stripping and absorption conditions. The ion speciation analyseswere performed in conjunction with the corresponding vapor–liquidequilibrium (VLE) of the system to enable the estimation of possibleCO2capture performance. Accurate speciations were performedfor a quaternary amine system using four concentrations consistingof 5.0 M MEA blended with 0.5, 1.0, 1.5, and 1.25 M DEAB solutionswith different CO2loadings at 24 °C, and for thefirst time, at higher temperatures using only the NMR calibrationmethod. By comparison, the NMR calibration method with the new procedureswas shown to be valid and perhaps the only approach for determiningion speciation for quaternary amine solutions at higher temperatures. [ABSTRACT FROM AUTHOR]

In the present work, ion speciation studies in solutions of the novel amine 4-(diethylamine)-2-butanol (DEAB), at various CO2 loadings (0–0.8 mol of CO2/mol of amine) and amine concentrations (0.52–1.97 M), were determined by 13C nuclear magnetic resonance (NMR) spectroscopy. In addition, the dissociation constant K of DEABH+ was determined at 24.5, 35, and 45 °C using a pH meter. The ion speciation plot, which contains various sets of concentrations of DEAB, protonated DEAB, bicarbonate, and carbonate, was successfully generated. Because DEAB is a novel solvent, this is the first time that the ion speciation plots of the DEAB–CO2–H2O system have been developed. It is also the first time that the 13C NMR calibration technique was applied to develop the vapor–liquid equilibrium (VLE) model for an amine–CO2–H2O system. The results obtained from the present work can be a great help for the further analysis of the DEAB VLE model, as well as CO2 absorption and kinetics studies. Furthermore, it was found that the novel 13C NMR calibration technique developed in this work provides higher accuracy than the conventional technique. [ABSTRACT FROM AUTHOR]

A simple hydrothermal process was developed to synthesize Co 0.5 Cd 0.5 S/g-C 3 N 4 composite photocatalysts. The crystal structure and surface morphology were characterized with XRD and TEM. The chemical state on the material surface, the chemical structure as well as the ultraviolet–visible light response of the photocatalyst were investigated with XPS and UV–vis DRS. The hydrogen production experiments indicated that the Co 0.5 Cd 0.5 S catalyst exhibits enhanced efficiency and stability with the addition of g-C 3 N 4 , which effectively inhibited the occurrence of photo-corrosion and promoted the separation efficiency of the photogenerated electron–hole pairs. The highest rate of H 2 generation from the composite catalyst is up to 6.31 mmol g −1 h −1 under visible light (λ > 400 nm). [ABSTRACT FROM AUTHOR]

Highlights: [•] La2O3-modified Ni/SBA-15 catalysts were studied in CH4 reforming with CO2. [•] Ni dispersion and the catalytic performance were improved with La addition. [•] The promoting intermediates were trapped in a designed infrared cell. [•] La promotes the reforming mainly by adsorbing CO2 and facilitating CO* and CH x O*. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, the reaction kinetics and mass transfer performance of CO2 absorption into aqueous solutions of blended MDEA–MEA solutions were comprehensively studied. The reaction kinetics was investigated using a laminar jet absorber in terms of a second order reaction rate constant and enhancement factor. The mass transfer performance was evaluated experimentally in a lab-scale absorber packed with high efficiency DX structured packing in terms of CO2 concentration profile and over all mass transfer coefficient (KGav ). The experiments were conducted over the MDEA/MEA concentrations of 27/3, 25/5, and 23/7wt% MDEA/wt% MEA (which equivalent to MDEA–MEA molar ratios of 2.3/0.5, 2.1/0.8, and 1.95/1.16M, respectively). It was found that kMEA was successfully extracted and can be expressed as: . The results also show that the operating parameters (i.e., MDEA–MEA blended ratio, temperature, and CO2 loading) affect both the reaction kinetics and mass transfer performance significantly. Lastly, the MDEA–MEA blended ratio of 1.95/1.16 provided the highest reaction kinetics and mass transfer performance among the three concentrations investigated in this study. [Copyright &y& Elsevier]

Herein, three g-C 3 N 4 (MCN/TCN/UCN), obtained by the direct pyrolysis of melamine/urea/thiourea respectively, were introduced as supports to optimize the NH 3 -SCR activity of Ce-W-Ti catalyst. Compared to CWT-400-Air, CWT@g-C 3 N 4 (2)-300-N 2 exhibits lower crystalline anatase TiO 2 and larger specific surface area, which improves the dispersion of Ce/W/Ti species on catalysts surface. Furthermore, the introduction of g-C 3 N 4 as supports also contributes to doping C/N elements into Ce-W-Ti catalyst and increases the Ce 3+ /(Ce 3+ +Ce 4+ ) and O α /(O α +O β ) molar ratios on catalyst surface. These all are advantageous to the NH 3 -SCR activity. However, UCN shows better promotional effect than MCN and TCN. This might be mainly attributed to the loose and porous stacked layered fold structure of UCN, the larger BET surface area, higher dispersion of Ce/W/Ti species and moderate weak/medium-strong acid sites of CWT@UCN(2)-300-N 2 . At the same time, the influence of carbon nitride amount, calcination atmosphere and calcination temperature on the NH 3 -SCR activity of CWT@g-C 3 N 4 catalyst were also investigated.

To reduce the huge energy cost of CO 2 capture technology applicable in industry, the CO 2 absorption-desorption performance was conducted in a novel bench-scale pilot plant with hot water as a heat source. The trisolvent MEA(monoethanol amine)-BEA(butylethanol amine)-AMP(2-amino-2-methyl-1-propanol) was prepared at a specific concentration to analyze the CO 2 capture performance and compared with 5 M MEA as the benchmark. Meanwhile, several solid acid catalysts, blended H-ZSM-5/γ-Al 2 O 3 (1/2), or HND-8, were packed in the desorber, and the solid base catalyst, CaCO 3 or CaMg(CO 3 ) 2 , was packed in the absorber with random packing. The CO 2 absorption efficiency (AE), cyclic capacity (CC), and heat duty (HD) were tested onto MEA-BEA-AMP and MEA under various operating conditions. Experimental results indicated that the performance of 4.3 mol/L MEA-BEA-AMP was significantly better than 5 M MEA under both catalytic and noncatalytic operation. The most energy efficient combination of this study was discovered as 0.3 + 2 + 2 mol/L MEA-BEA-AMP, with 50 g (CaCO 3 /CaMg(CO 3 ) 2 ) in the absorber and 150 g H-ZSM-5/γ-Al 2 O 3 (1/2) in the desorber. The heat duty reached as low as 2.4 GJ/tCO 2 at a F G of 7.0 L/min and a F L of 70 mL/min. These results were highly applicable in an industrial amine scrubbing pilot plant for CO 2 capture., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

A bubbling reactor is an important type of gas scrubber to reduce SO 2 emissions in maritime shipping. Both experiments and simulations were conducted to study the relationship between the periodic gas bubbling process and SO 2 concentration at the outlet of the reactor, and the entrainment of liquid droplets on SO 2 absorption. The accuracy of the model was verified by comparing the bubble size, the depth of bubbles injected into the water, and the SO 2 concentration obtained in both experiments and simulations. The gas bubbling process is accompanied by bubble formation, rise, and collapse. The gas bubbling period is affected by the disturbance of the liquid level. The period of the SO 2 concentration at the outlet of the gas bubbling reactor is smaller than that at the gas jar outlet which acts as the gas buffering region. The amounts of water carried out of the bubbling reactor by the gas bubbling process increase with the gas flow rates. The droplets and liquid film in the gas jar and the connecting tube play an important role in the absorption of SO 2 . This study encourages more research to reduce the fluctuation of SO 2 concentration and consider droplet entrainment in the design of bubbling reactors.

Antibiotic drugs have become dominating organic pollutants in water resources, and efficient removal of antibiotic drugs is the priority task to protect the water environment. Cu 3 P/SnO 2 photocatalysts of various Cu 3 P loadings (10-40 wt% Cu 3 P) were synthesized using a combination of hydrothermal synthesis and a partial annealing method. Their photocatalytic activity was tested for tetracycline hydrochloride (TC-HCl) degradation under visible light irradiation. Cu 3 P/SnO 2 samples were characterized by X-ray diffraction (XRD), N 2 -adsorption, ultraviolet-visible diffuse reflectance spectra (UV-vis DRS), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The results showed that the p-n type heterostructure between Cu 3 P and SnO 2 was successfully constructed, and addition of Cu 3 P to SnO 2 could improve its photocatalytic activity at an optimized loading of 30 wt% Cu 3 P. In photocatalytic degradation studies, removal rates of around 80% were found in 30 minutes of dark reaction and 140 min of photodegradation. The removal rate was superior to that of Cu 3 P and SnO 2 alone under the same experimental conditions. According to trapping experiments and electron spin resonance (ESR) measurements, photogenerated holes (h + ) and superoxide radicals ˙O 2 - were considered as the main oxidation species in the present system. Finally, the reuse experiments showed high stability of Cu 3 P/SnO 2 . This study reports Cu 3 P as a cocatalyst combined with semiconductor SnO 2 to form a highly efficient heterogeneous photocatalyst for the degradation of tetracycline hydrochloride for the first time., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A computational chemistry approach was used to elucidate and verify the different nitrosamine formation mechanisms and pathways. These included nitrosamine formation under acid or basic environments in the presence of NO, O 2 , SO 2 and CO 2 without NO 2 . The results clearly showed that nitrosamine could be formed without NO 2 via 2 different types of mechanisms, namely, addition and elimination forming N-N bond before proton transfer and proton transfer before N-N bond formation, respectively. The essence of these mechanisms identified in this work was that two reaction steps were required to complete both reaction mechanisms with different nitrosating agents. Two steps were both necessary neither of which could be neglected, if the nitrosamine formation reaction was to be completed. Computational simulation performed on the reactant, intermediate, transition state, and product for each set of reactions also validated the proposed mechanisms. Experiment also detected nitrosamine from the reaction of diethylamine and NO, SO 2 , O 2 , and CO 2 in both liquid and gas phase. Thus, NO 2 is not necessary for nitrosamine formation to occur in the CO 2 capture system.

Pericyclic reaction theory arose from ideas presented in 1965, based on orbital-energy correlation diagrams (Woodward and Hoffmann) and state-energy correlation diagrams (Longuet-Higgins and Abrahamson). Here we have used ab initio complete-active-space self-consistent field (CASSCF) calculations to generate such diagrams. First we present diagrams for the classic case of cyclobutene ring opening, to demonstrate agreement between the CASSCF results and the classic diagrams of both Woodward/Hoffmann and Longuet-Higgins/Abrahamson. Then we present diagrams for the more difficult cases of N(2) + photoexcited O(2), to produce either 2 NO or NNO + O. These N(2) + O(2) cases feature significant electron reorganization, for which elementary pencil-and-paper diagrams are less accurate. Finally, the benefits and limitations of such diagrams for predicting photochemistry are briefly discussed., ((c) 2007 Wiley Periodicals, Inc.)