•Ru10%[BMIM]BF4/AC catalyst exhibits high activity for acetylene hydrochlorination.•Ru10%[BMIM]BF4/AC catalyst has favorable anti-coking deposition property.•Ru species interact with [BMIM]BF4 and the oxygen-containing functional groups on the AC support.Imidazolium-based Ionic Liquids (IBILs) were employed to synthesize Ru-based catalysts using the Supported Ionic Liquid Phase (SILP) technique for acetylene (C2H2) hydrochlorination, combining the characterizations of transmission electron microscopy (TEM), N2 adsorption-desorption (BET), thermogravimetric analysis (TGA), temperature-programmed desorption (TPD), and X-ray photoelectron spectra (XPS), etc. The optimal Ru10%[BMIM]BF4/AC catalyst achieved the C2H2 conversion of 98.9% and the selectivity to vinyl chloride monomer (VCM) of 99.8% under the temperature of 170 °C and the C2H2 gas hourly space velocity (GHSV) of 180 h−1. Further, other IBILs with different anions were chosen to fabricate Ru-based catalysts, and the catalysts showed high activity and selectivity similar with Ru10%[BMIM]BF4/AC catalyst. It is demonstrated that IBILs additives can significantly improve the dispersion of ruthenium species and prevent the appearance of coke deposition owing to the interactions between Ru species and [BMIM]BF4. Moreover, the oxygen-containing functional groups on the carbon support are associated with the interactions among Ru species and [BMIM]BF4.Download full-size image

•There are three routes for BaP degradation in SCW at different oxygen concentrations.•Fuel gases are produced in the SCWG and SCWPO systems.•H2 molecules are mainly produced from H radical-rich water.•CO molecules are mainly produced from aldehydes losing its H atoms.•There is a time delay between the production and the consumption of H2 and CO.The degradation mechanism of benzo[a]pyrene (BaP), a representative component of coking wastewater, and the pathway for the production of H2 and CO in supercritical water have been investigated via ReaxFF reactive molecular dynamics simulations. The BaP molecules in the SCWG, SCWPO and SCWO systems show different degradation pathways. The maximum H2 yield is obtained at the oxygen ratio of 0.2. There are three routes for the generation of H2 molecules and production from H radical-rich water is the main route. CO molecules are formed by the CC bond breakage and CO bond breakage in the reforming fragments. There is a time delay between the fuel gas generation reaction and the side reactions due to the change of the instantaneous concentrations of H2 and CO, providing a possible pathway to increase the amount of the produced fuel gases by designing a suitable reactor and recovering the gas fuel in time. Finally, kinetic behaviors of coking wastewater have been analyzed.Download high-res image (261KB)Download full-size image

A series of bimetallic PdRu catalysts supported on γ-Al2O3 were prepared by incipient wetness impregnation method and were assessed in the 2-ethylanthraquinone hydrogenation process. It is found that the addition of Ru to Pd can improve the catalyst's activity and maintain high selectivity at the same time for 2-ethylanthraquinone hydrogenation. Several analysis techniques including N2 adsorption–desorption, ICP-AES, XRD, TEM, H2-TPR, H2-TPD and XPS were adopted for characterizing the structural and electronic properties of the samples. It is revealed that PdRu bimetallic system shows stronger hydrogen desorption behavior in contrast to the monometallic catalysts. In addition, the higher fraction of Pd2+ and the presence of Ru4+ in the PdRu system may act as the electrophilic sites for the adsorption and activation of the CO of the 2-ethylanthraquinone molecule through the lone electron pair of the oxygen atom. These factors may be attributed to the superior performance of PdRu bimetallic samples for 2-ethylanthraquinone hydrogenation.

•A modified method is used to test the sulfur forms in char.•FeS2 transforms into Fe1−xS, FeS and Fe3O4 after coal SCW gasification.•Liquid S after coal pyrolysis is S + 4 and S + 6, while S − 2 also exists in SCW case.•Supercritical water restricts thiophene and SO2 forming.The efforts of supercritical water (SCW) on sulfur transformation during coal gasification process were studied in a batch autoclave. Sulfur morphological distribution of two different rank coals on solid, liquid and gas phase at different temperatures were thoroughly investigated during coal SCW gasification compared with coal pyrolysis. Compared with coal pyrolysis, the removal of sulfate-sulfur and pyritic-sulfur in solid state were enhanced during coal SCW gasification, especially with temperature rising. Both in coal pyrolysis and coal SCW gasification, the XRD analysis showed that the pyrite which blended with coal transformed into pyrrhotite, whereas pyrrhotite further converted into magnetite during SCW gasification. Supercritical water had the ability not only restrict thiophene forming, but also oxidize organic-sulfur to produce sulfone, causing that the forming of organic-sulfur was restrained. The sulfate and sulfite were the main liquid-sulfur composition after coal pyrolysis, whereas sulfide also existed in spite of sulfate and sulfite after coal SCW gasification. The sulfide may be produced via H2S absorbing in water. Because the sulfide can be oxidized into sulfate and sulfite by OH radicals in SCW condition, the amount of sulfate and sulfite was much larger than that after coal pyrolysis. The gas sulfur after coal pyrolysis included H2S and SO2, but the abundant H radicals provided by SCW system caused much more H2S produced and inhibited the formation of SO2. The sulfur transformation could be explained by free radical mechanism. Those transformation properties were important for further environmental evaluation and the better using of coal SCW gasification technology with low sulfur pollution.

2,4,6-Trinitrotoluene (TNT), as a representative component of explosive wastewater, is treated in supercritical water gasification (SCWG) and supercritical water oxidation (SCWO) using molecular dynamic simulations based on ReaxFF reactive force field as well as density functional theory (DFT). The detailed reaction processes, important intermediates and products distribution, and kinetic behaviors of SCWG and SCWO systems have been analyzed at the atomistic level. For the SCWG system, TNT is activated by water cluster or H radical and the N atom is mainly converted into NH3 more than N2 through two significant intermediates NOH and C–N fragment. In addition to water cluster and H radical, the TNT is activated by O2 in the SCWO system. Besides, the N atom is transferred into N2 more than other N-containing products after 750 ps simulation. Combined with the calculated cracking energy of the bonds in TNT, SCWG can accelerate its degradation and is easier for C–N bond breaking or changing through other reactions because of its low cracking energy (69.6 kcal/mol in thermal decomposition and 59.0 kcal/mol in SCWG). In addition, a large amount of H2 molecules is produced in SCWG, which is a meaningful way of transforming waste to assets. On TNT degradation, SCWO with inadequate O2 that can be treated as partial oxidation reaction (SCWPO) can combine the advantages of SCWG and SCWO (with enough O2) to convert TNT into CO2, H2O, as well as H2 and NH3 with high economic value. Finally, a kinetic description is performed whose activation energies (17.6 and 18.4 kcal/mol) are theoretically consistent with experimental measurements.

The rapid-cooling crystallization of tolbutamide (TB) was carried out from ethanol and ethanol–water solutions at different initial supersaturations (3.5 and 2.7). PXRD and FTIR were used to characterize the polymorphs. It was found that the metastable Form IV with advanced solubility and bioavailability was obtained from ethanol–water solutions at the higher supersaturation, while stable Form III directly crystallized from ethanol at both supersaturations and from ethanol–water solution at the lower supersaturation. Hirshfeld surface analysis and the associated 2D fingerprint plots of the five TB polymorphs clearly quantify the interactions within the crystal structures. The mechanism of selective crystallization of the metastable polymorph of tolbutamide in ethanol–water solution was disclosed by molecular dynamics simulation. It was indicated that stronger interactions between TB and solvents weaken the TB–TB intermolecular NH⋯O hydrogen bonds and thus promote TB molecules to form dimers by π⋯π stacking. This work provides a feasible approach, combining experimental and molecular dynamics simulation methods, to better understanding the effect of solvent and supersaturation on polymorph outcomes by studying the competitive relationship between solute–solute and solute–solvent interactions, which is fundamental to the rational design of experimental work for controlling organic crystal polymorphs by simply varying solvents and supersaturations.

The reaction mechanism of coal pyrolysis and hydrogen production in supercritical water (SCW) was investigated using the molecular dynamic simulations via the reactive force field (ReaxFF) method combined with the density functional theory (DFT) method. Our calculations present that the water clusters in SCW weaken the C–C bonds in aromatic rings, thus the C(ring)–C(ring) bond cracking energy decreases as much as 287.3 kJ/mol and 94.6 kJ/mol compared with that in pure coal pyrolysis and in coal pyrolysis in vapor state, respectively. After the aromatic rings break into small cyclic structures, such as quaternary rings and ternary rings, the water clusters in SCW further weaken their C–C ring bonds to induce the small cyclic rings to open. During this process, the water clusters (without any radicals) in SCW turn into H radical-rich water clusters after providing OH radicals to the cyclic rings. This is the main source for the production of hydrogen molecules in SCW–coal system. The combination of H radicals produced by coal with water clusters in SCW is another pathway which forms H radical-rich water clusters. Under the catalysis of water molecules or clusters, H radical-rich water clusters decompose into H2 and OH radicals. These OH radicals further bind with coal intermediates and result in the breaking of coal intermediates into smaller products. Therefore, the cooperative effects between SCW and coal form a virtuous circle, which greatly enhances the reaction rate of coal gasification, promotes the production of small molecules, and increases the yield of hydrogen.Graphical abstractHighlights► Water clusters weaken C–C bonds to promote aromatic ring-opening reactions. ► H radical-rich water clusters improve the production of small molecules. ► H radical-rich water clusters increase the H2 yield. ► The cooperative effects between SCW and coal form a virtuous circle.

The stability and activity of alkaline carbonate catalysts in supercritical water coal gasification has been investigated using density functional theory method. Our calculations present that the adsorption of Na2CO3 on coal are more stable than that of K2CO3, but the stability of Na2CO3 is strongly reduced as the cluster gets larger. In supercritical water system, the dispersion and stability of Na2CO3 catalyst on coal support is strongly improved. During coal gasification process, Na2CO3 transforms with supercritical water into NaOH and NaHCO3, which is beneficial for hydrogen production. The transformation process has been studied via thermodynamics and kinetics ways. The selectively catalytic mechanism of NaOH and the intermediate form of sodium-based catalyst in water-gas shift reaction for higher hydrogen production has also been investigated. Furthermore, NaOH can transform back to Na2CO3 after catalyzing the water-gas shift reaction. Thus, the cooperative effects between supercritical water and Na2CO3 catalyst form a benignant circle which greatly enhances the reaction rate of coal gasification and promotes the production of hydrogen.