Abstract: This paper analyzes the coal to char stages of char formation of six coals of different ranks by using Fourier transform infrared coupled with attenuated total reflectance (ATR-FTIR). The chars were obtained by coal pyrolysis carried out at temperature range of 450 ~700. The data obtained shows the pragmatic disappearance of the aliphatic hydrogen content with increasing char formation temperature. Numerical evaluation of the spectra enabled the determination of aromaticity, fa. The aromaticity was found to be between 0. 66 ~0. 79 for lignite, 0. 75 ~0. 90 for sub-bituminous, 0. 84 ~1. 00 for low volatile bituminous, 0. 83 ~ 1. 00 for high volatile bituminous, 0. 94 ~1. 00 for semi-anthracite, and 0. 97 ~1. 00 for anthracite respectively. With increasing rank of coal samples, spectra exhibit rising aromaticity and enhanced condensation of aromatic rings, whereas the aliphatic chain lengths decrease.
Abstract: The interfacial properties between three types of coal slags (A, J1 and J2 with various base/acid ratio) and two refractory materials (mullite and corundum) were studied. The results indicate that the slag A has good wettability on both of refractory materials. While, the slags J1/J2 have experienced the process from incomplete wetting to whole wetting. The contact angles decrease with increasing of interface width of slag and refractory materials (S-R). The contact angles of J1 on mullite decrease with increasing of inclination angles from deformation temperature to 1 520 ℃, but significantly increase when the inclination angle is 20°. The SEM-EDS analysis show that the quantity of slag A permeating into the refractory material is more than that of J1 slags because of interfacial reaction. The infusion and acid-base reactions are the key factors for the refractory corrosion.
Abstract: 3 ash samples with nearly same chemical compositions were obtained by blending two raw coal ashes and mixing with different additives. There exists obvious difference among the ash fusion temperatures (AFTs) of the three ash samples. Mineral transformation at high temperature (>800 ℃) was studied by SEM-EDX and XRD. The results show that different regulative methods have different impact on AFTs. This is because that the mineral composition at high temperature is related with the type of chemical elements and their occurrence in minerals. Both of them determine the ash fusion characteristics.
Abstract: The Zhujixi washed coal has high ash fusion temperature which were studied by adding fluxes calcium carbonate, ferric oxide, complex flux and dolomite. The results indicate that all fluxes can reduce the ash fusion temperature which is varied depending on different species and mass of fluxes addition. Ash fusion temperature can remarkably be reduced by adding small amount of complex flux or dolomite. By using thermodynamic FactSage software, the mineral compositions at high temperature of coal ash with flux were studied. This will be helpful to explain how the fluxes can improve the fusion properties.
Abstract: Two lignocellulosic municipal solid wastes including waste paper and camphor tree leaf were pyrolyzed at temperatures of 500~1 000 ℃ in a horizontal tube furnace. The mineral matter and carbonaceous structure of both municipal solid wastes were characterized by X-ray diffraction (XRD) and Raman spectroscopy, respectively. The evolution of mineral matter and carbonaceous structure during pyrolysis was investigated. The results demonstrate that the original mineral matter in waste paper and camphor tree leaf is principally calcite and weddellite, respectively. Weddellite can completely decompose to calcite below 500 ℃, and then turn to lime above 800 ℃. In addition, Raman spectroscopy is found to be considerably sensitive to the carbonaceous structure of municipal solid wastes. At relatively low temperatures, the macromolecules of municipal solid wastes are subjected to the condensation and depolymerization, resulting in an increase in the amount of isolated sp2 carbon, thus the D1 band full width at half maximum (FWHM) and band area ratio ID1/IG increase with increasing pyrolysis temperature. In contrast, at relatively high temperatures, the D1 band FWHM and ID1/IG decrease, which is attributed to the increase of ordered sp2 carbon. Consequently, the order of carbonaceous structure of both municipal solid wastes shows an initial decrease and then an increase with the increasing of pyrolysis temperature.
Abstract: Through mechanical-mixing, impregnating and sol-gel methods, Fe2O3-based oxygen carriers (OC) were prepared with natural attapulgite (ATP) as an inert support and characterized by X-ray diffraction (XRD), energy dispersive spectrometer (EDS), and nitrogen adsorption-desorption measurements. The reactivity of Fe2O3-based oxygen carriers (Fe2O3/ATP OCs) in coal chemical looping combustion (CLC) was investigated in a fluidized-bed reactor at 900 ℃ by using steam as the gasification agent. The results indicated that the surface area and attrition resistance of Fe2O3/ATP OCs are improved significantly by using ATP as the support. Owing the synergy between ATP and Fe2O3, both are catalytic active, carbon conversion is enhanced significantly. ATP is an appropriate support for Fe2O3 oxygen carriers, whereas the sol-gel method gives the carriers best performance. U-Fe4ATP6 prepared by the sol-gel method, with a surface area of 4.920 7 m2/g and Ca content of 4.3%, exhibits much better performance than other two oxygen carriers. When used in CLC, the initial carbon conversion rate reaches 0.168 min-1, with an average CO2 concentration of 98.6% and a combustion efficiency of 98.7%. The catalytic activity of U-Fe4ATP6 is slightly decreased after twenty cycles; the initial carbon conversion rate is decreased to 0.108 min-1 and the residence time (t95) is extended to 18 min, whereas the CO2 capture efficiency and combustion efficiency remain at about 98.6% and 96.7%, respectively.
Abstract: Effect of attapulgite on PM2.5 emissions and agglomeration during coal combustion was investigated in a fixed bed system. The effects of addition amount, combustion temperature, mole ratio of calcium to sulfate and combustion atmosphere on mass and number concentration and collection efficiency of PM2.5 were analyzed. The results show that attapulgite added during coal combustion can effectively reduce PM2.5 emissions. The suitable amount of attapulgite is no more than 3%. PM2.5 emission during coal combustion in air is higher than that in O2/CO2 atmosphere. PM1 mass concentration decreases with increasing mole ratio of calcium to sulfate, while PM1~2.5 mass concentration increases, indicating an increasing trend in particle size. Increasing combustion temperature will increase PM2.5 emission and reduce its collection.
Abstract: Xylopyranose and O-acetyl-xylopyranose, the two monomers of xylan, were employed as the model compounds to study the mechanism for the formation of hydroxyacetaldehyde (HAA) from xylan by pyrolysis. Six possible pathways from xylopyranose and three from O-acetyl-xylopyranose were proposed by employing the density functional theory (DFT) at B3LYP/6-31+G(d,p) level; the energetically favored pathways for HAA formation were revealed. Xylopyranose may undergo ring-opening, dehydration, rearrangement and retro-aldol reactions sequentially, to form HAA that contains C4/C5; the rate-determining step is the dehydration reaction, with an energy barrier of 253.3 kJ/mol. From O-acetyl-xylopyranose, the side chain is cleaved in the first place, forming acetic acid (AA) and a cyclic intermediate; the ring-opening and H-shift reactions happen afterwards from the cyclic intermediate to generate HAA containing C4/C5; the rate-determining step is the H-shif reaction, with an energy barrier of 317.6 kJ/mol.
Abstract: In this research, 1-butyl-pyridinium tetrafluoroborate ([C4Py][BF4]-) was prepared by ion exchange method and was characterized by 1H-NMR, 13C-NMR, and FT-IR techniques. The synthesized ionic liquid was used for removal of dibenzothiophene as a typical organosulfur pollutant from organic medium. The effect of different parameters on the extraction efficiency was studied and optimized. At the optimized conditions, 97.68% of dibenzothiophene was extracted from 1 000 mg/L n-hexane solution. The extraction efficiency obtained in this work was higher than the previous reported values. The desulfurization reaction was kinetically followed the second order mechanism. The ionic liquid was reusable and after four regeneration cycles 97% of its original extraction efficiency was retained.
Abstract: Through the impregnation of Mo/AC catalyst with an aqueous solution of ammonium thiosulfate (ATS), the ex-situ presulfided Mo/AC-ATS catalyst was prepared; the influence of activation temperature and time on the catalytic performance in the hydrodesulfurization (HDS) of thiophene as a probe reaction was investigated. The result indicated that under the optimized activation conditions, viz., 300 ℃ and 0.5 h, the conversions of thiophene over the presulfided Mo/AC-ATS catalyst are 34% and 42% higher than those obtained over the Mo/AC catalysts sulfided with traditional DMDS and CS2 sulfiding agents, respectively. The XPS, TPR-MS and TEM results demonstrated that the presulfided Mo/AC-ATS has a high content of Mo4+, which may contribute to its high activity in HDS.
Abstract: To improve sulfur resistance of bimetallic nitrides in benzene hydrogenation reaction, K-promoted (K-Ni2Mo3N) catalysts were prepared to investigate the effect of potassium on sulfur resistance. K-Ni2Mo3N expressed a higher sulfur resistance than Ni2Mo3N when used in benzene hydrogenation with 0.01% thiophene condition. Combined XPS and H2-TPR characterization results, it could be concluded the potassium species might donate electrons to nickel species to make nickel species an electron-enriched state, which might weaken the interaction bewteen thiophene and nickel species. The TPD-MS results also confirmed the potassium species weakened the thiophene adsorption on the catalyst surface. The critical parameter of sulfur resistance are the suitable adsorption strength which could be handled by the electron condition of active site.
Abstract: NaY molecular sieve, modified by NH+4, Zn2+, Cu2+, Cr3+ metallic cations, were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR) and nitrogen adsorption. XRD and FT-IR results indicated that the crystalline structure of the Y molecular sieve was not changed after modification. The average pore size, Brunauer-Emmett-Teller (BET) surface area and the pore volume of CrY was smaller than other modified molecular sieves. CrY had some mesopores. The modified molecular sieve was used to adsorb nitrogen from simulated fuel containing quinoline. The molecular size of quinoline, calculated by using density functional theory (DFT), was 0.711 6 nm×0.500 2 nm, implying that the quinoline can not access easily to the 0.74 nm microporous pores of Y molecular sieve. The denitrification performance of modified catalysts was in the order: CrY, CuY, ZnY and NH4Y, which implying that the absorption denitrification performance of modified Y molecular sieve related to valence state of metal ion. The result showed that the effects of absorption time on denitrification removal at modified Y molecular sieve by same valence metal ions were showed the same trend and the higher the valence, the higher the denitrification removal. Adsorption temperature had little influence on the denitrification removal by using CrY and NH4Y molecular sieve could be used at room temperature. The adsorption removal of quinoline by CuY and ZnY increased with the increasing temperature. The calcination had effects on the denitrification performance of CrY. The XRD measurement showed that the skeleton of CrY molecule sieve had been burned down and had almost totally lost its denitrification capability.
Abstract: ZnO/SiO2/ZSM-5 zeolites were prepared from ZSM-5 by vacuum metal impregnation of metallic oxides and silicon deposition. The resulted zeolite were characterized by XRD, BET, NH3-TPD, SEM and TEM. Furthermore, the influence of silicon deposition time and the content of impregnated ZnO to the selectivity and yield of p-xylene (PX) on the reaction of aromatization of methanol was investigated. The results indicated that by twice silicon deposition and 2.0% ZnO, the modified ZSM-5 had the highest PX selectivity. The yield of PX could reach up to 28% at 420 ℃, 0.2 MPa and 1.25 h-1 of methanol WHSV.
Abstract: A series of Ni-based catalysts with different supports (Al2O3, ZrO2, CeO2, CeO2-Al2O3 and ZrO2-Al2O3) were prepared by the methods of impregnation. The effects of supports on the physical structures and catalytic performance of the resultant catalysts in partial oxidation of methane (POM) were investigated. The catalysts were characterized by N2 physical adsorption, X-ray diffraction, temperature programmed reduction by hydrogen, temperature programmed desorption of ammonia and temperature programmed oxidation. The results showed that the Ni/Al2O3 catalyst had a large BET specific surface area and high initial activity. However, the Ni/Al2O3 catalyst showed a serious deactivation due to the formation of large amount of carbon deposited on the surface of the catalyst. Ni/ZrO2 and Ni/CeO2 catalysts displayed low activity, which resulted from its low BET specific surface area and poor NiO dispersion. The Ni/ZrO2-Al2O3 catalyst showed high activity and the Ni/CeO2-Al2O3 catalyst exhibited the best activity and coking resistance among the catalysts. CeO2 could effectively suppress carbon formation and the transformation to inactive carbon species, due to the oxygen storage and release ability.
Abstract: The direct conversion of methane to acetylene and the indirect conversion of mathane to syngas were studied by using the atmospheric pressure spark discharge, and with the in-situ diagnosis of optical emission spectroscopy. The results were compared with the dielectric barrier discharge. Results show that, the spark discharge, having remarkable advantage of high energy efficiency, was able to easily activate the methane molecules into species such as C, H and C2. C2H2 was formed as a major hydrocarbon product when methane was fed alone, while the syngas was formed with adjustable H2/CO ratio when CO2 and O2 were co-fed with methane. It is worth of mention that, the addition of O2 overcame completely the troublesome problem of reactor coking during the spark discharge of CH4 and CO2, the production of syngas was allowed to be carried out at a temperature as low as 225 ℃. Therefore, the new syngas preparation method is very attractive comparing with the traditional catalytic routes.
Abstract: A series of Mn doped γ-Fe2O3 catalysts(Fe0.7Mn0.3Oz) were prepared with different calcining temperatures via a coprecipitation method, and the influences of calcination temperature on the low-temperature selective catalytic reduction (SCR) activity of Fe0.7Mn0.3Oz catalysts were investigated. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The results indicate that Fe0.7Mn0.3Oz catalysts calcined at 350 ℃ exhibit the best low-temperature SCR activity, and the NOx conversion reaches above 90% at 70 ℃ and 100% at 100~200 ℃, while the catalysts calcined at 450 ℃ show a poor low-temperature SCR activity. When the calcination temperature is 350 ℃, the catalysts possess the highest specific surface area and pore volume, flourishing pore structure and appropriate γ-Fe2O3 crystallinity. However, when the calcination temperature is increased to 400 or 450 ℃, the sintering takes place and α-Fe2O3 appears in Fe0.7Mn0.3Oz catalysts, which is unfavorable to the low-temperature SCR reaction. Therefore, 350 ℃ is recommended as the optimum calcination temperature for Fe0.7Mn0.3Oz catalysts.
Abstract: Hollow dendritic mesoporous tungsten trioxide (d-WO3) was synthesized by combining the hydrothermal method with the template-sacrificing method; with d-WO3 as a support, Pt/d-WO3 catalyst was prepared through an improved liquid phase reduction method. The Pt/d-WO3 catalyst was characterized by XRD, BET and TEM and its electrocatalytic activity and stability towards methanol electro-oxidation were investigated by cyclic voltammetry and chronoamperometry. The results indicated that d-WO3 exhibits hollow microsphere dendritic structure with a length of 6 μm and a width of 2 μm; Pt nanoparticles with a size of 7.2 nm were highly dispersed on the surface of d-WO3. The nitrogen physisorption on d-WO3 displays type IV isotherms, which are typical for the mesoporous materials. Moreover, d-WO3 shows a BET surface area of 24 m2/g, with a large number of pores around 20~120 nm. The as-prepared Pt/d-WO3 catalyst exhibits higher electrocatalytic activity and better stability in methanol electro-oxidation in comparison with the Pt/WO3 and Pt/C catalysts. The enhanced catalytic performance of Pt/d-WO3 is attributed to its unique hollow mesoporous structure and the double function, which greatly accelerates the dehydrogenation of methanol on Pt.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
