Abstract: The abundant pore structure and large number of oxygen-containing groups cause high water content of lignite, which limit its efficient utilization. In this paper, high concentration, low viscosity and high stability coal water slurry was prepared by hydrophobic modification of low rank coal to make it have the property of high rank coal. Using anionic surfactant sodium stearate and nonionic surfactant OP-10 as emulsifier emulsified alkyl ketene dimer (AKD), anionic AKD modifier and non-ionic AKD modifier were prepared, which were coated on the surface of microwave drying coal to improve the hydrophobic properties of coal particles. The surface properties of coal particles before and after modification such as chemical composition, pore distribution, hydrophobic properties and Zeta potential were studied. Combined with the adsorption results of NSF dispersant on the surface of coal particles before and after modification, the slurryability, rheology and stability of lignite coal water slurry were discussed. It is found that surface of the modified coal particles has higher carbon content and lower oxygen content, while their pore volumes are reduced, the contact angles of coal-water interface are increased, and hydrophobicity of the coal particles is enhanced. The adsorption capacity of NSF dispersant on surface of modified coal increases, which makes the surface electronegativity of coal particles increases, and coal particles have better dispersion effect in water. The maximum concentrations of CWS prepared by anionic AKD modified coal and non-ionic AKD modified coal increase from 56.6% of raw coal to 61.0% and 62.5% respectively, and the water evolution rates of CWS decrease from 13.97% of raw coal to 7.45% and 7.89% respectively. At the same time, the CWS prepared by modified coal particles show shear-thinning pseudoplastic fluid. Overall, the physical and chemical properties of coal particles have significantly changes after modification, and high-quality slurry fuels with high solid concentration, superior pseudo-plastic behavior, and good stability are easier to be prepared.
Abstract: The mechanism of NO reduction with CO catalyzed by char was studied via density function theory (DFT). The optimized configurations and stationary points of homogeneous and heterogeneous reactions on the char surfaces of Zigzag and Armchair were obtained. Finally, kinetic analysis for both homogeneous and heterogeneous reactions were carried out. The results show that the activation energy of homogeneous NO reduction reaction is 254.06 kJ/mol, while only 86.94 and 52.16 kJ/mol for heterogeneous reaction on Zigzag and Armchair models, respectively. This indicates that char is able to play an activating role in the NO reduction reaction. The NO reduction reaction on the char surface undergoes four stages of N2 formation, N2 release, and two stages of CO2 release, and finally generates one N2 molecule and two CO2 molecules. Moreover, the surface structure of char has a great influence on the characteristics of NO reduction reaction. Compared to Zigzag char surface, NO reduction reaction with Armchair-type has a lower energy barriers and higher reaction rate constants. That is, the NO reacts easily with CO on the Armchair surface.
Abstract: The corn stalk was used as the raw material and the deionized water was used as the medium to study the effect of aqueous phase recirculation on characteristics of bio-crude oil formation during hydrothermal liquefaction of corn stalk. No additional deionized water was added during the recirculation. The results show that the aqueous phase recirculation can enrich the concentration of organic acids in aqueous phase and promote the conversion of ketophenols, which can improve the yield and quality of bio-crude oil and solid products. Specifically, the aqueous phase recirculation has little effect on the pH value of the aqueous phase (3.62-3.91), but the organic acids such as acetic acid and propionic acid are continuously accumulated and the content of ketones and phenols is gradually reduced. Also, the yield of bio-crude oil is gradually increased from 20.42% to 24.31%, the quality of bio-crude oil is slightly improved, and the carbon content of the solid product is increased from 60.94% to 61.74%.
Abstract: Polypropylene (PP) and bamboo were selected as typical representatives of waste plastics and biomass. And the biomass and plastic co-pyrolysis weight loss, kinetic mechanism and product distribution were studied by thermogravimetric analyzer and fixed-bed reactor. The synergistic mechanism between biomass and plastic during co-pyrolysis was discussed. As the ratio of plastic increases, the ending temperature of co-pyrolysis decreases from 501 to 471℃, while the main temperature range for co-pyrolysis is shortened. What's more, the total activation energy required for the co-pyrolysis decreases when the plastic ratio is below 0.25 and then increases. Comparing the experimental with theoretical data, it is found that the synergistic effect during biomass and waste plastics co-pyrolysis is obvious. Due to the synergistic effect, the total activation energy for co-pyrolysis is much lower than calculated value. In addition, the synergistic effect can promote the conversion of macromolecular volatiles into small-molecule gas, accelerate the generation of hydrocarbons like aromatics and alkanes, and inhibit the formation of oxygen-containing substances like CO2, phenol, carboxylic acids, furans and ketones.
Abstract: La:Cu:Zn:X (X=Zr, Al, Al+Zr) perovskite-like catalysts were prepared by coprecipitation method followed by liquid phase reduction by NaBH4. The physicochemical properties of the catalysts were tested by a series of characterization methods, and the catalysts were tested for methanol synthesis from CO2 hydrogenation in a fixed-bed reactor. The results showed that the as-prepared catalysts were mainly composed of La2CuO4 perovskite-like crystal structure and doping of elements led to the spatial distortion of the perovskite-like structure. After reduction by NaBH4, metal copper species and some high-valence copper species were found, which could be further reduced during the reaction. The CO2 conversion was positively correlated with the Cu surface area, the dispersion of Cu, and the (Cuα++Cu0)/Cutotal of the catalyst. The higher methanol selectivity was obtained when Cuα+ binding energy was farther away from Cu+ binding energy. LCZA had the highest CO2 conversion, LCZ catalyst possessed the highest methanol selectivity, and LCZZA catalyst presented the optimal methanol space time yield.
Abstract: KCuZrO2 catalysts modified with different F-T elements (Fe, Co, Ni) were prepared by co-precipitation method and then were tested for isobutanol synthesis from catalytic CO hydrogenation. The catalysts were characterized by N2 adsorption and desorption experiments (BET), XRD, TEM, XPS, H2-TPR, CO-TPD and in situ DRIFTS. The results showed that the addition of F-T components promoted the formation of ethanol and propanol, and had different effects on the selectivity of isobutanol. The characterization results showed that Fe promoted the dispersion of catalyst components, and enriched the active component Cu on the catalyst surface, which improved the active adsorption of H2 and CO. In addition, more C1 species were formed on the KFeCuZrO2 catalyst surface, and these C1 species could further react with ethanol and propanol to produce isobutanol. However, the catalysts modified by Co and Ni lacked sufficient C1 species, so the selectivity of isobutanol did not increase significantly. The introduction of Co had little effect on the structure of catalyst and the dispersion of Cu, but the activity of catalyst decreased after Co addition, which might be due to the deactivation of catalyst. After adding Ni to the catalyst, the specific surface area decreased and the particle size increased, and the Cu/Zr molar ratio on the catalyst surface also decreased to 0.19. The interaction between Cu-Zr was weakened, and the isobutanol selectivity was also reduced.
Abstract: ZSM-5 zeolite is considered as an effective catalyst in the synthesis of trioxane from formaldehyde. In this work, a series of ZSM-5 zeolites with different SiO2/Al2O3 molar ratios were used in the synthesis of trioxane from formaldehyde; through characterization by XRF, XRD, SEM, NH3-TPD, Py-FTIR and 27Al MAS NMR, the effect of acidity including the Brønsted and Lewis acid sites on the catalytic performance of ZSM-5 zeolites in the trioxane synthesis was investigated. The results indicate that the ZSM-5-250 zeolite with a SiO2/Al2O3 molar ratio of 250 exhibits excellent catalytic performance in the synthesis of trioxane. The ZSM-5-250 zeolite owns sufficient amount of Brønsted acid sites which are active for the synthesis of formaldehyde to trioxane; meanwhile, it has few Lewis acid sites and can then effectively inhibit various side-reactions like the Cannizzaro or Tishchenko reactions. Moreover, the ZSM-5-250 zeolite displays high stability with a single-pass lifetime of 114 h and can be regenerated easily through calcination at 550℃.
Abstract: Based on the density functional theory, the photocatalytic water splitting reaction has been studied over the monolayer MoS2 alloying with MoSe2, MoTe2 and WS2 under stress condition. The calculated results show that the monolayer MoS2 alloyed with MoSe2, MoTe2 and MoWS2 under the compressive stress condition can increase the band gap and improve the position of CBM (conduction band minimum) band edge to enhance the efficiency of photocatalytic water splitting. The calculated energy band and density of states show that the alloy elements form energy band instead of isolated energy level, which has little effect on carrier life.
Abstract: Four natural aluminosilicate minerals including kaolin, rectorite, montmorillonite and illite were activated by thermal activation, alkali fusion activation, sub-molten salt activation and quasi-solid-phase activation method, respectively. Comparing the activation effects of the four methods, it is found that both sub-molten salt method and quasi-solid-phase method present better activation effect at lower energy consumption, which are obviously superior to the other two activation methods. The quasi-solid-phase activation method is the most promising method for activating the natural aluminosilicate minerals due to its much lower energy consumption and more feasible industrial operation. Comparatively, the framework structure of kaolinite rectorite and montmorillonite are relatively more easily to be depolymerized, the structure of illite is much stable, after being sub-molten salt activated and quasi-solid-phase activated, the resulted illite has little active SiO2 and Al2O3 which can be used to synthesize zeolites due to their high chemical reactivity. Therefore, different from the other three natural aluminosilicate minerals, illite is not an ideal raw material for zeolite synthesis.
Abstract: Cu-Al spinels were synthesized by a solid phase method using Cu(OH)2 and pseudo-boehmite as the raw materials. The effects of synthesis temperature, synthesis time and Cu/Al molar ratio on the formation and properties of Cu-Al spinels were fully investigated by the thermogravimetry(TG/DTG), X-ray diffraction(XRD), H2 temperature programmed reduction(H2-TPR). The non-isothermal kinetics of Cu-Al spinel formation process were analyzed using Coats-Redfern method and two diffusion-controlled kinetic models. Characterization results showed that the Cu-Al surface spinels with unsaturated coordination formed easily at the temperature as low as 400℃, and the content of these surface spinel decreased sharply with the synthesis temperature rising. The hardly-reducible spinel Cu2+ species and easily-reducible spinel Cu2+ species were identified at the synthesis temperature of 700 and 800℃, respectively. The spinel content increased gradually with the synthesis temperature increasing, leading to the formation of Al-rich spinel solid solutions with different Cu/Al molar ratios. At a higher temperature of 1200℃, however, the formation of stoichiometric CuAl2O4 spinel was observed. Hence, the spinel reducibility varied dramatically with the synthesis temperature as illustrated by the drastic change of the molar ratio of hardly-reducible spinel Cu2+ species and easily-reducible spinel Cu2+ species. An appropriate excess of Al3+(Cu/Al=1:3) could result in the formation of spinel solid solution with more hardly-reducible spinel Cu2+ species, while an excess of Cu2+ would lead to the formation of delafossite-type CuAlO2. Both samples owned low reducibility as compared to the stochiometric CuAl2O4 spinel. Besides, a longer synthesis time would favor the spinel formation as well but to a limited extent. Non-isothermal kinetics analysis showed that the formation process of Cu-Al spinel owned three kinetic regions in terms of synthesis temperature, namely 700-850, 850-950 and 950-1200℃, and the apparent activation energies were determined to be 85.2, 304.4 and 38.1 kJ/mol, respectively. The diffusion of reactants via product layer could be considered as an one-dimensional diffusion below 950℃, whereas it was more likely to be a three-dimensional diffusion above 950℃, indicating that the product layer became much thicker.
Abstract: β-Mo2C support was first prepared by the temperature-programmed carbonization and the Au/β-Mo2C catalysts with different Au loadings were then obtained by using the in -situ precipitation method. The Au/β-Mo2C catalysts were characterized by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and nitrogen physisorption; their performance, the thermal stability at the high temperature in particular was then investigated in the reverse water-gas shift (RWGS). The XRD results reveal that the diffraction peaks appeared at 34.44°, 38.02°, 39.44°, 52.12°, 61.53°, 69.62° and 74.65° correspond to the (100), (002), (101), (102), (110), (103) and (200) planes of β-Mo2C, respectively, whereas no characteristic peak of Au species is detected, suggesting the high dispersion of Au nanoparticles on the Au/β-Mo2C catalysts with a low Au loading (0.1%-0.5%). The STEM results illustrate that for the Au/β-Mo2C catalysts with an Au loading of 0.5%-2.0%, gold nanoparticles in the form of atom clusters (about 2 nm) are anchored and uniformly dispersed on the β-Mo2C surface. The nitrogen physisorption results demonstrate that the Au/β-Mo2C catalysts have plenty of mesopores. The catalytic evaluation results indicate that the 0.2%Au/β-Mo2C catalyst exhibits high activity and high selectivity to CO for the RWGS reaction; moreover, after the reaction, the Au nanoparticles are still evenly dispersed and the pore structure remain intact, suggesting that the Au/β-Mo2C catalyst owns excellent performance and high thermal stability in the he reverse water-gas shift at high temperature.
Abstract: MoO3 was used as precursor, CH4/H2 as carbon source, and a direct reduction carbonization method with programmed temperature rise was used to prepare molybdenum carbide catalysts at different final carbonization temperatures (640, 660, 680, 700, and 720℃). The physical properties and structural properties of molybdenum carbide were characterized by XRD, N2 adsorption, SEM, TEM, XPS and Raman. The effect of final carbonization temperature on the catalytic performance of molybdenum carbide in quinoline hydrodenitrogenation was studied. The results showed that the molybdenum carbide catalysts with different final carbonization temperatures were all existed in the phase of β-Mo2C. The final carbonization temperature could significantly change content of species on the surface, average pore size, and mesopore distribution of molybdenum carbide. When the final carbonization temperature was 680℃, a higher carbonization degree, the lowest content of oxygen species on the surface and the highest surface C/Mo molar ratio of catalyst were obtained; accordingly, the best catalytic activity of catalysts was achieved. At 340℃ and 4 MPa, the conversion and denitrification rate of quinoline were up to 99%, while the selectivity of aromatic compounds was up to 37.8%, showing a lower aromatic ring destruction. Surface composition, especially surface oxygen, was essential for the regulation of the quinoline hydrodenitrogenation reaction pathway on β-Mo2C.
Abstract: DESs/SG catalyst was prepared by supporting the proline-based deep eutectic solvent (DES) on the silica-gel (SG) matrix using a sol-gel method; the catalyst structure was characterized by FT-IR, XRD, SEM/EDS and N2 adsorption-desorption. The results showed that the DESs were successfully incorporated into the silica-gel matrix, leading to a decrease in the surface area and pore volume, but an increase in the pore diameter. With hydrogen peroxide as oxidant, the catalytic performance of DESs/SG in the oxidative desulfurization of a model oil containing dibenzothiophene (DBT) was investigated; the effects of deep eutectic solvent loading, reaction temperature, n(H2O2)/n(S) ratio, catalyst amount, sulfur compound type and catalyst recycle times on the desulfurization efficiency were considered. The results indicated that under optimum desulfurization conditions, the desulfurization degrees for DBT, 4, 6-dimethyl-dibenzothiophene (4, 6-DMDBT) and benzothiophene (BT) over the DESs/SG catalyst were 97%, 96.5% and 46.4%, respectively; after recycling for 9 times, the DESs/SG catalyst still displayed a desulfurization degree of above 89.4%.
Abstract: An immobilized nano-photocatalyst H4SiW12O40/Bi2WO6 was quickly prepared by the supercritical hydrothermal synthesis method. The properties, morphology and structure of the prepared catalysts were investigated and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), and transmission electron microscope (TEM) and BET, respectively. The photocatalytic denitrification properties were evaluated by using the model oil with 15 mg/g pyridine. The results show that the photocatalyst is the self-assembly three-dimensional spherical structure by two-dimensional nano-flakes, and the relationship between Bi2WO6 and H4SiW12O40 is not a simple solid loading, but is a new crystal under the condition of supercritical water. It is because the existence of this kind of crystal that the H4SiW12O40 is firmly fixed on the Bi2WO6 photocatalyst and the photocatalytic activity and service life of H4SiW12O40/Bi2WO6 photocatalyst are improved. In view of the contradiction between the preparation period of photocatalyst and the crystal development, the supercritical hydrothermal technology and the photocatalyst template-oriented synthesis technology are organically combined to obtain the H4SiW12O40/Bi2WO6 photocatalyst with good crystal heterostructure and greatly shorten the preparation period of the photocatalyst, greatly reduce the preparation cost of the catalyst and overcome the main contradiction of the industrialized application of the photocatalyst. The nitrogen removal efficiency of the prepared H4SiW12O40/Bi2WO6 photocatalyst for light oil is as high as 97%.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
