Abstract: The flotation fractions of a long-flame coal were obtained by heavy medium separation method, and its effect on regulation of sulfur and coke reactivity during pyrolysis of high-sulfur coking coal were investigated by FT-IR, Raman, TG, Gieseler fluidity, N2 adsorption, XRD. The results show that the low density fractions contain more aliphatic side chains and unstable aliphatic structure, while the high-density fractions show higher amount of minerals and inert components. Low density fractions have the highest sulfur removal rate due to lower content of alkaline minerals and more aliphatic side chains. The medium molecular weight component in the low density fractions has little effect on properties of metaplast. Higher minerals and inert components in high-density fractions deteriorate the metaplast more obviously. Meanwhile, order of the coke's microcrystalline structure is reduced and the defect sites increase, and consequently, reactivity of the coke increases.
Abstract: Petroleum ether, carbon disulfide, methanol, acetone, and acetone/carbon disulfide were selected as solvents for ultrasonic-assisted extraction of acid-washed Hefeng sub-bituminous coal. The extract and residue were identified as Ei and Ri (i = 1, 2, 3, 4, 5) for each stage. By FT-IR characterization of Ei and Ri, molecular structure of the extracted product was analyzed by means of segmented peak fitting. The results show that the hydroxy hydrogen bond in the fifth-order extract is dominated by self-associating hydroxy hydrogen bond; in aliphatic substances, only E3 was dominated by aliphatic −CH3 and asymmetric −CH2 stretching vibration, while the other extracts were dominated by symmetric and asymmetric −CH2 stretching vibration. E1 is dominated by symmetric bending vibration of aliphatic chain terminal −CH3 and asymmetric deformation vibration of −CH3 and −CH2, indicating that petroleum ether mainly break the easily dissociated chemical bonds in coal samples; CS2 dissolve a higher proportion of aromatic structure containing aliphatic side chains. The functional groups contained in the five residues are the same, indicating that the main structure of the coal sample is not changed due to the stepwise extraction. Extraction has an obvious influence on aromatic structure and hydroxy hydrogen bond in the residue. Aromatic structures change from di-substituted benzene dominant to tetra-substituted benzene dominant. Before extraction, the hydroxyl hydrogen bond in the acid-washed coal sample was dominated by hydroxyl ether hydrogen bonds, and after extraction, it was transformed into self-associated hydroxyl ones. In addition, sequential extraction has little effect on oxygen-containing functional groups and aliphatic functional groups. By comparing structural parameters, it is found that E1, E3, and R5 has a higher degree of aromatic condensation, and E4 has a longer straight-chain and less branched chain.
Abstract: The hydrogenation and co-hydrogenation behaviors of Hami coal and Tahe residue were investigated in an autoclave, and the feasible technical route for co-hydrogenation was explored. The experimental results showed that Hami coal had good hydroliquefaction performance and the suitable reaction temperature was 445℃. At 445℃ and 9 MPa, the coal conversion rate reached 98.74%, and the oil yield reached 68.54%. The hydrogenation tests of Tahe residue showed obvious coking tendency at the lower temperature, and it was difficult to achieve lightening. At 430℃, the conversion rate of Tahe residue was only 66.38%, the light oil yield was only 50.01%, and its coking rate was as high as 9.45%. The coking rate increased with the reaction temperature. When the mixtures of Hami coal and Tahe residue were co-hydrogenated directly, the conversion rate of the raw materials was lower, and the coke phenomenon was obvious. At the coal/oil ratio was 40:60, the conversion rate was 97.79%, and oil yield was 73.36%. Adding hydrogen solvents into the co-hydrogenation system could effectively inhibit coke formation, increase the conversion rate, and lighten co-hydrogenation products. When the amount of coal was 45% and Tahe residue was 20%, the conversion rate of raw materials was 98.38% and the oil yield was 74.82%.
Abstract: The effect of desulfurizer, modified TiO2 prepared by different methods on the NO emission from inferior coal burning and the adaptability of coal type were studied by using a tube furnace. The prepared Zr-TiO2 and the char were characterized by XRD, BET, SEM, XPS, TGA, and the mechanism of denitrification was explored. The results show that the addition of desulfurizer can promote NO emission. When the combustion temperature is 850 ℃, oxygen flow rate is 40 mL/min and the desulfurizer is MgO, the NO emission is the lowest as the catalyst of 5% Zr-TiO2 prepared by impregnation method is added, which is 51.0% lower than that with addition of pure TiO2 and 84.6% lower than that with pure coal under the same conditions. The catalyst 5% Zr-TiO2 can be applied to the coal with sulfur < 3% and ash < 30%, having a wide application range. The doping of Zr can inhibit the growth of grain, enhance the active component, increase the content of adsorbed oxygen, promote the transformation of the valence states of the elements, accelerate the devolatilization of volatiles, promote the combustion, increase the specific surface area of chars, and enhance the ability of heterogeneous reduction of chars.
Abstract: Herein quantum chemistry methods were used to discuss the microscopic mechanism in the arsenic/hydrogen/oxygen reaction system during combustion by Gaussian09 and GaussView at the theoretical level of B3LYP/6-311G (3df, 3pd). Configuration of the reactants, intermediates, transition states, and products of 13 elementary reactions were optimized and the authenticity of these reactions were verified by frequency and intrinsic reaction coordinates. Finally, the kinetic parameters were calculated through KiSThelP based on the classic transition state theory. This study focused on some of the most important reations in the arsenic/hydrogen/oxygen system, which makes sense to establish arsenic dynamic model during combustion.
Abstract: The reaction behaviors of primary volatiles from oil shale pyrolysis were investigated using a two-stage reactor under different in-situ thermal reaction conditions. The reaction parameters of secondary reactor, such as, reactor temperature, atmosphere and residence time, were studied for their effects on the pyrolysis oil/gas yield and quality. The results showed that the reaction temperature had profound influence on the oil and gas yield. The pyrolyzed shale oil and gas yield reduced by 15% and increased by 20% (mass) respectively, with the temperature of 2nd stage reactor increasing from 600 to 650 °C under optimized reaction condition of 1st stage. Comparing with nitrogen atmosphere, the liquid oil yield could be enhanced by 5% when steam was added as the reaction atmosphere in the second stage, and the corresponding oil was mainly concentrated in the gasoline and diesel distillations (that is, boiling point < 350 °C). The GC-MS analysis illustrated that the secondary reaction at the residence time of 0−3 s was mainly pyrolysis while the presence of steam could increase the content of aromatics in the oil and meanwhile suppress the condensation of aromatics. When the residence time was greater than 3−5 s, the secondary reaction was mainly condensation of poly-aromatics, which led to the increase of coke. Meanwhile, the gasoline and diesel oil yield remained stable, and the VGO fractions decreased by about 30%.
Abstract: Despite that iron-based catalysts are preferred for the high selectivity to value-added α-olefins via Fischer-Tropsch synthesis (FTS) reaction, the carbon deposition leads to deactivate catalyst more readily and CO2 selectivity as high as ~50% leads to low carbon efficiency. Herein, we developed an innovative approach to fabricate iron-based catalysts to deal with this issue. In detail, Fe3O4 microspheres with an average particle size of ~580 nm were prepared via hydrothermal method and mixed with GO. The GO modification can effectively inhibit the sintering and coking of the large Fe3O4 microspheres (580 nm) by assisting its evolution into much smaller iron carbide nanocapsules (~9.1 nm). The obtained catalyst exhibits excellent reaction activity, stability and high α-olefin selectivity. The addition of K into Fe3O4 microsphere produces major ε′-Fe2.2C about 58.9% in the evolution process and facilitates lower CO2 emission obviously.
Abstract: SBA-15 zeolite supported amorphous ternary Co-Ni-B was prepared by the ultrasonic-assisted impregnation method for catalyzing the hydroformylation of 1-octene to nonanal. Supporting on SBA-15 increased the dispersion of nano amorphous Co-Ni-B. The crystallization temperature of amorphous Co-Ni-B was elevated by 280 ℃ that improves the thermal stability of Co-Ni-B. Using Co-Ni-B/SBA-15 with Co loading of 17.22% and the ratio of n(Ni)/n(Co) of 0.157 and n(B)/n(Co + Ni) of 0.434, the conversion of 1-octene and the selectivity of nonanal reached 100% and 91.24%, respectively, in the hydroformylation reaction at 120 °C and 5 MPa. The selectivity of side-product was reduced by 1 time compared with that of Co-Ni-B. The Co-Ni-B/SBA-15 is stable after repeated used for 5 times.
Abstract: A series of metal phosphides including MoP, WP, CoP and NiP was prepared by temperature-programmed reduction with hydrogen from different phosphorus precursors. The effect of phosphorus precursor and feed H2/CO ratio on the catalytic performance of metal phosphides in the methanation was investigated. In comparison with diammonium hydrogen phosphate (DAP), phytic acid (PA) as a chelating agent can effectively disperse the metal precursor, reduce the reduction temperature, promote to form pure phosphide phase, and give the phosphide catalyst a higher surface area and a smaller particle size; as a result, the metal phosphides prepared with PA as a phosphorus precursor exhibit higher catalytic activity in methanation. In addition, the catalytic activity of various metal phosphides in methanation follows the sequence of MoP > WP > CoP > NiP. A high H2/CO ratio in the feed is favorable for the methanation over the phosphide catalysts; the selectivity to methane increases with an increase in the H2/CO ratio.
Abstract: Ni/SSZ-13 catalyst was prepared by the impregnation method and used to catalyze CO2 methanation in a fixed-bed reactor. The microstructure and physical-chemical properties of catalyst were characterized by N2 physical adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results show that Ni/SSZ-13 catalyst initiates catalytic activity towards CO2 methanation at 250 ℃. Ni/SSZ-13 catalyst shows the optimal performance for CO2 methanation at 450 ℃. CO2 conversion rate and CH4 selectivity are 70% and 95%, respectively. SSZ-13 support shows a cuboid structure. Moreover, SSZ-13 support mainly possesses microporous and contains some mesopores, which provide larger surface area for nickel species dispersion. During the reduction process of the calcined catalyst at 500 ℃, NiO is reduced by H2 into metal Ni, which is the main active component for CO2 methanation.
Abstract: In this work, simultaneous toluene removal and syngas methanation using the combination of packed-bed dielectric barrier discharge and Ni/γ-Al2O3 catalyst were conducted with the research object of simulated gasification gas (SGG) containing toluene. The effects of reaction temperature, H2/CO ratio and H2O addition on the reaction performances of both toluene removal and SGG methanation were investigated. The results show that high-efficiency simultaneous toluene removal and SGG methanation can be achieved at 400°C under plasma catalysis treatment. When the H2/CO ratio is 3.2, the toluene removal rate and the tar removal rate are close to 100% and 97%, the CO conversion rate and CH4 selectivity approach about 88% and 97%, and the energy efficiencies in toluene removal and SGG methanation processes can reach 9.7 g/(kW·h) and 17.3 mol/(kW·h). Both the high H2/CO ratio and the H2O addition can promote toluene removal and SGG methanation, and reduce the amount of carbon deposition but increase its graphitized degree. Moreover, high H2/CO ratio can rise the heating value of SGG and achieve higher energy efficiencies in both toluene removal and SGG methanation processes, while the H2O addition is difficult to obtain high CH4 selectivity to increase the heating value and is not conducive to the promotion of energy efficiency in SGG methanation process. In addition, for these two simultaneous processes, the SGG methanation process exerts a significant inhibiting effect on toluene removal, but process of toluene removal has less influence on the other process due to the lower concentration of toluene.
Abstract: PtTi catalysts with particle size distribution of 8.3−12.5 nm and Pt loading capacity of 0.1 mg/cm2 were prepared by ultra-high vacuum dual-target co-sputtering system, and ultra-pure target as raw material. The structure, catalytic activity and durability of the prepared PtTi catalysts were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), durability pressure test (DST) and chronocurrent (I-t) methods, and the effect of the addition amount of Ti on the electrocatalytic performance of Pt-based alloy catalysts was investigated. The results show that the highest electrochemical active area (ECSA) is 186.14 m2/g, and after in-situ annealing at 600 ℃, the peak current density of direct-ethanol catalytic oxidation is 1448 A/g, and the stable current density value of 1100 s is 147.47 A/g, the attenuation rate of 3000 durability stress tests is 8.6%. The catalytic electrode studied in this work has excellent catalytic activity and high stability characteristics. It can be applied to the use of direct ethanol fuel cell electrodes and has extremely high application potential.
Abstract: Electrocatalytic water splitting is one of the most prospective technology for hydrogen production. Molybdenum disulfide (MoS2), as one of the most promising non-noble metal electrocatalysts, suffers from the disadvantages of limited catalytic sites and weak conductivity which urgently needs to be further optimized. Herein, the C3N4-Ti4O7-MoS2 heterostructure is constructed through a simple hydrothermal strategy. The interfacial interaction between the active components leads to more exposed active sites, the redistribution of the surface charge, the optimization of the hydrogen adsorption kinetics and stability, which makes up the typical shortcomings of MoS2. The results indicate that the interface effect endows C3N4-Ti4O7-MoS2 catalyst with excellent electrocatalytic activity for hydrogen evolution reaction (HER). The current density of 50 mA/cm2 for HER is obtained at the overpotential of 300 mV, with the lower Tafel slope (54 mV/dec) and stable catalytic activity over 33 h, which is much better than that of the pure MoS2. This work indicates that the interface effect, as an effective strategy for rational design of MoS2-based electrocatalysts, is crucial to the future development of catalytic hydrogen production.
Abstract: As one of the important solid adsorbents for CCUS (CO2 Capture, Utilization and Storage), the calcium-based adsorbents have attracted wide attention because they can directly capture CO2 from high-temperature flue gas and have a low cost and good adsorption performance. However, the calcium-based adsorbents are easy to sinter during repeated adsorption-desorption cycles, which will cause a sharp drop in adsorption performance. In this work, the reaction kinetics, thermodynamics and the sintering mechanism of the calcium-based adsorbents were summarized. At the same time, the advantages and limitations of various anti-sintering modification methods were compared and analyzed. The results show that the hydration modification can cause the adsorbent to collapse and obtain a larger surface area. The acid solution modification will generate more gas and small molecules during the preparation process to increase the porosity of the absorbent. Doping modification can promote the adsorption and diffusion of CO2, and the dopant can be acted as a framework to separate CaO particles. It can be concluded that the doping modification is a relatively promising modification method due to its simple process and good performance; and the use of calcium-containing solid waste for preparation of anti-sintering modified adsorbents has great potential for application.
Abstract: In this paper, γ-Al2O3 supported nickel, manganese, cobalt, and other metal oxide catalysts were prepared by the impregnation method respectively, and its ozone catalytic decomposition performance was studied at 25 ℃ under a WHSV of 200000 mL/(gcat·h). The results showed that 10% NiO/γ-Al2O3 catalyst demonstrates superior catalytic activity, and the ozone conversion rate is higher than 96% within 20 h. According to the characterizations of XRD, XPS, TEM, SEM-EDS and H2-TPR, its excellent ozone may be attributed to the formation of NiAl2O4 spinel on the surface of NiO/γ-Al2O3 catalyst. Furthermore, the mechanism of ozone decomposition on different transition metal oxide catalysts is divergent. The related study sheds new light on the reaction mechanism of ozone catalytic decomposition over transition metal oxides such as nickel and manganese, it also provides the guidelines for the development of efficient ozone decomposition catalysts.
Abstract: Slurry sample was collected from a 300 MW ultra-low emissions coal-fired power unit. The migration and transformation behaviors of mercury in the sample were investigated, and the effect of additive on the stability of mercury in solid gypsum was explored by considering the thermal release behavior and environmental risk. The results show that gaseous Hg0 is increased with the increase of slurry temperature, while Hg is increased in both gas phase and gypsum with the increase of slurry pH. The concentration of Cl− or $ {\rm{SO}}^{2-}_{4} $ increases in slurry could inhibit the reduction of Hg2+ to Hg0 and increase Hg proportion in gypsum. However, the increase of $ {\rm{SO}}^{2-}_{3} $ concentration is beneficial to the Hg enriched in gypsum and a part of Hg2+ reduced to Hg0. When Na2S, EDTA-2Na or DTCR-4 is added, Hg2+ is turned into HgS, Hg(EDTA)2 or [ −Hg-DTCR] −n, respectively among which more than 75% Hg is transferred to gypsum and Hg2+ is inhibited to reduce into Hg0. The thermal stability of Hg in gypsum can be ordered as Gypsum + EDTA-2Na < Gypsum + DTCR-4 < Gypsum + Na2S < Gypsum due to the stability difference among Hg(EDTA)2, [ −Hg-DTCR] −n and HgS(black). By using TCLP, SPLP and MEP, the chemical stability of Hg in gypsum can be ordered as Gypsum < Gypsum + Na2S < Gypsum + EDTA-2Na < Gypsum + DTCR-4 due to the concentration difference of water soluble mercury, acid soluble mercury and oxidizable mercury among gypsums.
Abstract: Ethylene is an important chemical raw material. In the process of traditional steam cracking to produce ethylene, by-products such as acetylene and ethane are produced. How to effectively separate these three hydrocarbon gases is very important. Based on the density functional theory, this paper systematically explored the adsorption, selection and permeation properties of the graphyne membrane for three gases. Combining adsorption analysis and reduced density gradient analysis, the interaction type, strength and action area of the three gas molecules penetrating the graphyne membrane were explored, and a quantum mechanical explanation of the separation performance was given. The results show that the selectivity of graphyne membrane to acetylene/ethylene, acetylene/ethane, ethylene/ethane can reach 2 × 105, 4 × 107, 165, respectively at room temperature; the permeability of acetylene at room temperature is about 6.54 × 10−5 mol/(m2·s·Pa), which is about 5 orders of magnitude higher than the industrial standard, and the ethylene permeability reaches the industrial standard at about 400 K. Through the analysis of quantum mechanics, the interaction area between the gas molecules and the graphyne film is between the gas molecules and the center of the graphyne framework, and the type of action is mainly van der Waals interaction, as the gas molecules penetrate closer to the graphite acetylene membrane, the interaction becomes stronger and the strength of interaction is higher than that of acetylene, which is consistent with the energy barrier calculation.
Abstract: Using 325 mesh flake graphite as raw material, graphite oxide (GO) was synthesized by improved Hummers method. Nitrogen-doped reduced graphene oxide (N-rGO) carrier was prepared by hydrothermal method using urea as nitrogen source, and then supported Ni/N-rGO catalyst was prepared by impregnation method. The prepared catalysts were characterized and analyzed by N2 adsorption-desorption, XRD, SEM, H2-TPR and other methods. The hydrogenation performance of Ni catalysts supported by N-rGO, reduced graphene oxide (rGO) and activated carbon (AC) were compared under the reaction conditions of 150 ℃, 0.4 MPa and 2.0 h with selective hydrogenation of phenol to cyclohexanone as probe reaction. The results show that the N-rGO support not only has a large specific surface area and suitable pore structure, but also has good synergistic effect with nickel metal, and the Ni/N-rGO catalyst thus shows excellent catalytic activity and selectivity.
Abstract: The porous materials of rod-like γ-alumina interlaced in pores of volcanic rock were prepared by in-situ growth using volcanic rock as matrix material, aluminum nitrate and ammonium bicarbonate as raw materials. The structure and properties of the materials were characterized by XRD, SEM, N2 adsorption-desorption and TG-DSC technology. The adsorption performance of Congo red was also studied. It was found that the aluminum nitrate solution filled the pores of volcanic matrix materials by diffusion and adsorption, and amorphous alumina was formed after calcination. During hydrothermal treatment and calcination, the formed alumina was transformed into ammonium aluminum carbonate hydroxide and γ-alumina. The optimal reaction conditions for the preparation of rod-like γ-alumina/volcanic rock porous materials were as following: the concentration of ammonium bicarbonate solution was 0.8 mol/L, the reaction temperature was 140 ℃, and the reaction time was 4 h. The rod-like γ-alumina stacked in the channels of volcanic rock with a diameter of 50−150 nm and length of 3−10 μm. The specific surface area and pore volume of the porous material was 0.1 mL/g and 47 m2/g, respectively. When the concentration of Congo red solution was 500 mg/L and the dosage of porous material was 2 g/L, the removal rate was 96% with the adsorption amount of 243 mg/g.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
