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Taking the block polyether which made from ethylene oxide/propylene oxide, and acrylic acid as the main polymerization monomer, and then acrylamide containing amide groups, and 2-acrylamide-2-methylpropane sulfonic acid were selected as functional monomers to produce early-strength polycarboxylate superplasticizer under normal temperature and pressure. The effects of different amounts of acrylic acid, redox system, chain transfer agent, reaction temperature and other factors on the products performance were investigated. The results showed that the early-strength performance of the superplasticizer was outstanding under the reaction conditions of n (polyether monomer) :n (acrylic acid) :n (acrylamide) =1:8:0.24, H2O2/ascorbic acid redox system at 40 °C. When the cement content of superplasticizer is 0.28% of the cement content, compared with conventional polycarboxylic acid superplasticizer, the 1 d and 3d compressive strength of the superplasticizer which containing acylamide group could be increased by 18.5% and 17.8% respectively. The initial and final setting time were reduced by 53% and 35% respectively. [ABSTRACT FROM AUTHOR]

The geometric structure, energy properties, and electronic properties of the aerogen-bonding interaction formed by C2H4 and NgOX2 (Ng = Kr, Xe; X = F, Cl, Br) have been studied at the B2PLYP-D3(BJ)/ aug-cc-pVTZ (PP) level. Two kinds of aerogen-bonding interactions were observed among the title systems: the σ-hole and the π-hole complexes. The σ-hole aerogen-bonding complex has a binding energy in the range of − 6.29 ~ − 8.17 kcal/mol, which is the most stable. The binding energies of C2H4···NgOX2 increased as X = F < Cl < Br and Ng = KrOX2 < XeOX2 for the σ/π-hole aerogen-bonding complexes. The atoms in molecules (AIM), the non-covalent interaction (NCI) index, and the LMO-EDA energy decomposition analysis were adopted to study the nature of the σ/π-hole aerogen-bonding interaction. The results show that the electrostatic term contributes the most to the total interaction energy for the σ/π-hole aerogen-bonding complexes. [ABSTRACT FROM AUTHOR]

The oxidation mechanisms of thiophene (Tp) with H2O2 over defect and perfect titanium silicalite-1 (TS-1) were investigated by means of DFT/ONIOM2 calculations for different models 7T:45T, 9T:45T and 13T:45T. The B3LYP, ωB97X-D, and M06-2X functionals were used in the high-level part of ONIOM2, with PM6 in the lower-level part. The related potential energy surface profiles are constructed based on the ωB97X-D/ONIOM2 method for 13T:45T cluster. Four possible paths are proposed for the oxidation of Tp into sulfoxide and sulfoxide into sulfone using H2O2 as an oxidant over defect and perfect TS-1. The dimerization of sulfoxide and sulfone through Diels-Alder cycloaddition is also studied. It is found that perfect TS-1 is highly unfavorable compared to defect TS-1 (TS-d). The calculated activation energy of Tp oxidation with TS-d is found to be remarkably lower than that without any zeolite catalyst. The calculated results may contribute to the understanding of the reaction mechanism of the catalytic oxidative desulfurization of sulfides in liquid fuels. [ABSTRACT FROM AUTHOR]

The oxidative desulfurization mechanisms of aromatic sulfur compounds, including thiophene, benzothiophene, and dibenzothiophene, with H2O2 on fully coordinated and defective Ti sites on Ti-beta zeolites are investigated by means of density functional theory calculations. In this work, three current concerns are explored: First is the oxidation of sulfides into the sulfoxides and sulfones in the presence of H2O2; the second is the comparison between the sulfide oxidation mechanism on T5 and T2 defective sites in Ti-beta zeolites; and finally the comparison with the oxidation mechanism on fully coordinated Ti site on the Ti-beta zeolite. The model shows that T5 defect site in Ti-beta is the most catalytically active site for the oxidation of aromatic sulfides. [ABSTRACT FROM AUTHOR]

Incorporating multiple functional sites in porous frameworks to enormously enhance the host-guest interactions is an effective strategy to obtain high-performance CO 2 capture and chemical fixation MOF materials. Herein, we designed and constructed a microporous (3, 36)-connected txt -type Cu(II)-based MOF (HNUST-17) from dicopper(II)-paddlewheel clusters and a novel pyridine-based acylamide-linking V-shape diisophthalate ligand with amino groups. Interestingly, with a high density of multiple strong CO 2 -philic sites (open metal sites, acylamide and amino functionalities) integrated in the framework, which have been identified by GCMC (Grand canonical Monte Carlo) simulations and DFT (Density functional theory) calculations, HNUST-17 exhibits high and selective capture for CO 2 over CH 4 and N 2 at ambient temperature. Moreover, HNUST-17 possesses efficiently catalytic activity and recyclability for chemical fixation of CO 2 coupling with epoxides into cyclic carbonates in the presence of tetrabutylammonium bromide as the cocatalyst under mild, solvent-free conditions.