Helium-3 NMR chemical shifts of various 3He-encapsulated fullerenes (3He@Cn) and their derivatives have been calculated at the GIAO-B3LYP/3-21G and GIAO-HF/3-21G levels with AM1 and PM3 optimized structures. A good linear relationship between the computed 3He NMR chemical shifts and the experimental data has been determined. Comparisons of the calculation methods of 3He NMR chemical shifts show that GIAO-B3LYP/3-21G with AM1-optimized structures yields the best results. The corrected 3He NMR chemical shifts were calculated from the correction equation that is obtained through linear regression fitting of the experimental and calculated 3He NMR chemical shifts over a wide range of 3He-encapsulated fullerene compounds. The corrected 3He NMR chemical shifts match the experimental data very well. The current computational method can serve as a prediction tool and can be applied to the assignments and reassignments of the 3He NMR chemical shifts of 3He@Cn and their derivatives.
Abstract Enthalpy‐entropy compensation remains a mystery in chemistry and biophysics. Recent study suggested that the solvent reorganization might constitute the physical origin of the compensation, which was unfortunately not widely applicable because compensation was also observed in solid phase reactions. In this study, a general theoretical model based upon strict mathematical deduction was presented, which indicated that the redistribution of the distinguishable subspecies might be the physical origin of the enthalpy‐entropy compensation in complex systems. As examples, the enthalpy‐entropy compensations in solvation and surface adsorption were discussed.
CBS-Q and G3 methods were used to generate a large number of reliable Si–H, P–H and S–H bond dissociation energies (BDEs) for the first time. It was found that the Si–H BDE displayed dramatically different substituent effects compared with the C–H BDE. On the other hand, the P–H and S–H BDE exhibited patterns of substituent effects similar to those of the N–H and O–H BDE. Further analysis indicated that increasing the positive charge on Si of XSiH3 would strengthen the Si–H bond whereas increasing the positive charge on P and S of XPH2 and XSH would weaken the P–H and S–H bonds. Meanwhile, increasing the positive charge on Si of XSiH2· stabilized the silyl radical whereas increasing the positive charge on P and S in XPH· and XS· destabilized P- and S-centered radicals. These behaviors could be reasonalized by the fact that Si is less electronegative than H while P and S are not. Finally, it was demonstrated that the spin-delocalization effect was valid for the Si-, P- and S-centered radicals.
Abstract The development of new catalytic systems for the conversion of biomass‐derived molecules into liquid fuels has attracted much attention. We propose a non‐noble bimetallic catalyst based on nickel–tungsten carbide for the conversion of the platform molecules 5‐(hydroxymethyl)furfural into the liquid‐fuel molecule 2,5‐dimethylfuran (DMF). Different catalysts, metal ratios and reaction conditions have been tested and give rise to a 96% yield of DMF. The catalysts have been characterized and are discussed. The reaction mechanism is also explored through capture of reaction intermediates. The analysis of the reaction mixture over different catalysts is presented and helps to understand the role of nickel and tungsten carbide during the reaction.
Laboratory-scale experiments and pilot scale experiments were performed to study the separation and recycle of phenol from wastewater with 200 to 6000 mg/L phenol and 5% salt. Liquid–liquid extraction (LLE) was an efficient means to separate phenol from wastewater. Some commercial extraction reagents, such as N-503, ABK, and QH1, were used to compare the extractive efficiency. The extraction time, mixed intensity, and separated factor were the key factors during the process of extraction and reverse extraction. In this work, the conditions of extraction were studied, and optimum conditions were obtained, except for conditions of pH 3.0, 1 atm, and ambient temperature. Stirred time (t1) and separated time (t2) were 3 seconds and 6 seconds, respectively. The optimum mixed Renault's value was in the range of 309,000 to 367,000, and the mass ratio of extraction reagent to wastewater was 1 to 3. A pilot-scale extractive system was designed based on the laboratory-scale experiment, which has been working for 5 years in a plant located in China.
A catalytic system over Ru-HAP catalyst is established to hydrodeoxygenate various oils to long-chain alkanes in water, for potential large-scale renewable diesel production, which has the following advantages. (i) This system is versatile to different oil sources, including Jatropha oil, palm oil, waste cooking oil, and cooking waste. (ii) Ru-HAP is highly efficient at achieving full conversion from stearic acid to alkanes at as low as 100 °C, and the isolated yield from Jatropha oil, palm oil, and waste cooking oil to long-chain alkanes reached up to 95, 96, and 87 mol % at 180 °C and 2 MPa H2 within 4–4.5 h, respectively. (iii) The catalyst showed high stability during five runs of recycling, ICP-OES analysis, and a hydrothermal treatment. The activity decreased less than 5% after the catalyst was treated in water at 200 °C for 24 h with a stirring speed of 1000 rpm due to the strong metal and hydrothermally stable support interaction. (iv) Ru-HAP is compatible with most impurities such as various salts, sugars, and macromolecules. (v) The system required low cost for operation since no dehydration before the reaction was necessary and the alkane product can be easily separated from water. The reaction route was investigated and indicated that the coexisting hydrodehydration and hydrodecarbonylation are affected by water, temperature, and H2 pressure. The catalyst was also characterized in detail, and its high reactivity and stability may result from the fact that highly distributed Ru nanoclusters anchored on the HAP support absorbed fatty acids by forming a metastable calcium carboxyl phosphate.
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