Abstract: In the present work, the synergistic effect of components on the mineral behavior in the SiO2-Al2O3-CaO-FeOx quaternary system was tentatively evaluated. The mineral transformation and reaction were analyzed by thermo-mechanical analyzer (TMA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and thermodynamic calculation (FactSage). In addition, the apparent viscosities of synthetic slags, expressed as a function of temperature and composition, were determined using a high temperature rotary viscometer with temperature ranging from 1 700℃ to re-solidifying temperature. The results demonstrated that the TMA and DSC approaches were applicable to characterize the mineral behavior under in-situ conditions. Silica and alumina preferred to be transformed to high temperature cristobalite and α-alumina with relatively stable structure and high viscosity, respectively. On the other hand, the reaction and transformation of silica and alumina could be accelerated by some valuable fluxing agents, particularly calcium oxide and iron oxides. The addition of ferrous oxide into synthetic slags could lower its viscosity compared with that of ferric oxide and ferroferric oxide. Furthermore, the reduction of iron oxides to metallic iron remarkably increased the viscosity. Ferric oxide may take part in the random glass network in a similar fashion with alumina. Besides, iron oxides with the oxidation state of Fe2+ may also act as a modifier under slightly reducing conditions and higher temperatures. The sensitivity of viscosity of mineral matters to temperature excursion decreased with increasing calcium oxide content as calcium oxide was able to enhance the solution ability of iron oxides in the SiO2-Al2O3-CaO-FeOx quaternary system.
Abstract: Coal ash and synthetic ash samples were used to detect effect of different ash components on ash fusion temperatures (AFTs). Thermodynamic database FactSage 7.0 was applied to simulate the melting process of ashes with different compositions, in order to provide theoretical basis for effect of ash components on ash fusibility. The reducing effect of Na2O on AFTs is due to the replacement of anorthite by albite and nepheline. The increasing content of MgO can initially lower and then raise the AFTs. When MgO exceeds certain content, forsterite is generated and raise the AFTs. The raising effect of sulfur on AFTs is due to the replacement of diopside by forsterite and calcium sulfate. The increasing content of CaO can also initially lower and then raise the AFTs. When CaO exceeds certain level, Si migrates from minerals with low melting points to those with higher melting points, thus raising the AFTs. Na2O is prior to CaO when being bound with silica-oxygen units to form minerals. The priority order of the oxides when being bound with CaO and silica-oxygen units is: Al2O3 > MgO > Fe2O3.
Abstract: Coal ash fusion temperature is important for large-scale gasifier/boiler designers and operators. There has been a big error for fusion temperature calculated by chemical composition of coal ash because the ash is composed of minerals actually, which has a strong impact on fusion temperature. A new calculation method, based on chemical composition and low temperature eutectics of minerals being considered, is proposed, according to 59 typical coal samples from the central and western regions in China. The most predictive values are not far from preciseness with a mean error lower than 5%, when the calculation is employed to 108 coal samples. Meanwhile, a roughly sufficient judgment to identify the ash fusion temperature greater than 1 500℃ is suggested by formula, which is 0.9≤SiO2/A12O3≤1.8 and SiO2+A12O3≥78% with accuracy of 92.2% among 167 coal samples.
Abstract: In order to obtain the influences of different reaction atmospheres on transformation and deposition characteristics of sodium in Zhundong high sodium coal for circulating fluidized bed technology, gasification (reducing atmosphere) and combustion (oxidizing atmosphere) experiments were carried out, respectively, at 950℃ for Xinjiang SEH high sodium coal in a 0.4 t/d circulating fluidized bed experimental apparatus. The results show that Na in fly ash and deposition ash exists mainly as NaCl. Na and Cl are easier to be reserved in bottom ash and fly ash during gasification comparing with combustion, and correspondingly less Na and Cl enter into gas phase. Part of NaCl is sulfurized by SO2 and more stable Na2SO4 is produced under combustion atmosphere and condenses on the surface of ash deposition probes. More fine particulates are produced during combustion and perform worse deposition problems. The corrosion of HCl to the metal wall exists in the process of SEH coals' combustion and gasification.
Abstract: XRD, Raman, XPS and FT-IR were used to examine microcrystalline structure changes of Shengli lignite eluted by inorganic acid (HCl, H2SO4 and HCl-HF). By adopting a designed surface adsorption instrument-GC, the samples were oxidized at low temperature through pulse method to investigate their oxygen adsorption under different temperatures. Via low-temperature oxidation, TG/DTG and fixed bed combustion tests, the spontaneous combustion tendency of coal samples were investigated. The results show that the removal of minerals increases the degree of order and graphitization of the coal structure. Compared with raw coal, oxygen absorption of inorganic acid elution samples decreases obviously. With the increase of adsorption temperature, oxygen absorption capacity increases significantly, but decreases with the increasing level of removed minerals, which reduces spontaneous combustion tendency of the treated coal.
Abstract: The combustion reactivity of two chars prepared from two low-rank coals in Northwest China were studied using a thermogravimetric analyzer (TGA). The effects of different atmospheres (O2/CO2, O2/N2 and O2/Ar) and different oxygen concentrations on the combustion characteristics were investigated. The results indicate that both atmosphere and oxygen concentration show effectiveness on combustion of char. Compared with N2 and Ar, CO2 could significantly promote the reaction. When combustion atmosphere changes from O2/CO2 to O2/Ar, the burnout temperature increases by 63.7 and 68.8℃ for the two chars respectively. Meanwhile, when the combustion atmosphere changes from O2/CO2 to O2/N2, that is 135.9 and 129.6℃, respectively. An increase in concentration of oxygen can also improve the combustion performance of chars in the test. At the same time, kinetic analysis of the combustion profiles of the chars reveals that both the apparent activation energy E and the pre-exponential factor A increased with increasing oxygen concentration and the compensation effect exists between activation energy E and pre-exponential factor A of chars' combustion.
Abstract: A series of BiOBr-graphene photocatalysts was synthesized using hydrothermal method, and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, ultraviolet-visible diffuse reflection spectroscopy (DRS) and photoluminescence (PL) emission spectroscopy. The photocatalysts were evaluated for photocatalytic oxidative desulfurization of model oil. The optimal temperature, graphene loading and the amount of hydrogen peroxide (H2O2) were investigated. The oxidation reactivity of the different sulfur compounds was found to be in the order of DBT>4, 6-DMDBT>BT. Moreover, the mechanism of photocatalytic oxidation of DBT by BiOBr-graphene was proposed based on the present experimental results.
Abstract: The adsorption behaviors of thiophene, cyclohexene and benzene, and competitive adsorption of thiophene & cyclohexene, and thiophene & benzene over NiY zeolites were studied by in situ Py-FTIR spectroscopy method. The results of single probe molecular adsorption indicate that the Lewis (L) acid sites according to Ni species are the major active centers for the thiophene adsorption, more over the Brönsted (B) acid sites of the NiY and HY are the catalytic active centers of the protonation and oligomerization of thiophene and cyclohexene, while the reaction intensity on NiY is significantly weaker than that on HY zeolite. The competitive adsorption results show that the strongly adsorbed dimeric cyclohexene on B acidic sites in NiY zeolite plays a significant competitive adsorption to thiophene adsorption behavior. The effective solutions to solve the competitive adsorption from olefins and aromatics to thiophene are to reduce the surface B acid centers of the adsorbent and to increase temperature of adsorption system.
Abstract: The metal-organic frameworks, MIL-53 (Al)-NH2 and MIL-53 (Al), were synthesized and used as the adsorbents for the removal of nitrogen-containing compounds (quinoline and pyrrole) from model fuel. The adsorbents were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-IR spectroscopy, and thermogravimetric analysis. Compared with the adsorption capacity of MIL-53 (Al), MIL-53(Al)-NH2 possesses a higher adsorption capacity for quinoline and pyrrole in the model fuel due to the hydrogen bonding interaction between MIL-53(Al)-NH2 and the nitrogen-containing compounds. The factors affecting the adsorption capacity are the adsorptive time and temperature. Furthermore, the pseudo-first-order and pseudo-second-order adsorption kinetics models were tested. It is found that the pseudo-second-order kinetics model is preferable to characterize the adsorption process. The adsorption isotherms and adsorption thermodynamics of quinoline and pyrrole on the MIL-53(Al)-NH2 were also evaluated. The calculation of separation factor RL and thermodynamic parameters (ΔG0, ΔH0和ΔS0) show that the adsorption of quinoline/pyrrole on the MIL-53(Al)-NH2 is a spontaneous and exothermic process. The used MIL-53 (Al)-NH2 could be regenerated by simple solvent washing with ethanol and reused in the adsorption process.
Abstract: The Keggin type H5PW10V2O40 was synthesized by Na2HPO4, NaVO3 and Na2WO4·12H2O. The divanadium-substituted phosphotungstate hybrid material [Bmim]5PW10V2O40 was synthesized by reacting H5PW10V2O40 and 1-butyl-3-methylimidazolium bromide ([Bmim]Br). The FT-IR, XRD and UV-vis characterization results show that the [Bmim]5PW10V2O40 hybrid materials possess Keggin structure and the interactions between the [Bmim]+ and the [PW10V2O40]5-. The SiO2-supported [Bmim]5PW10V2O40/SiO2 was prepared and used for oxidative desulfurization of dibenzothiophene (DBT) with the H2O2 as the oxidant. The experimental results show that the DBT conversion can reach 100% in the [Bmim]5PW10V2O40/SiO2-H2O2 oxidation system under the conditions of 40℃, oxigen/sulfur mol ratio 3.0 and 50 min reaction time. The catalyst was easily separated by centrifugation and could be reused for seven times without decreasing in oxidative desulfurization activity after drying treatment.
Abstract: With MCM-41 as support, the supported Ni2P/MCM-41 catalyst is prepared by first reducing the Ni2P precursors at low temperature (673 K) and then modifying the surface with air; the as-prepared Ni2P/MCM-41 catalyst was characterized by X-ray diffraction (XRD), N2-sorption, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and CO uptake. The catalytic performance of Ni2P/MCM-41 in hydrodeoxygenation (HDO) of benzofuran (BF) was investigated to elucidate the effect of surface modification with air on the catalyst structure and HDO activity. The results show that pure Ni2P acts as the active phase on the surface of modified Ni2P/MCM-41 catalyst; the surface modification can decrease the aggregation of P species and promote the formation of small and highly dispersed Ni2P active phase. Under 573 K, 3.0 MPa, a weight hourly space velocity of 4.0 h-1 and a H2/oil volume ratio of 500, the yield of O-free products reaches 88% for HDO of BF over the modified Ni2P/MCM-41 catalyst, which is about 50% higher than that over the catalyst prepared by conventional temperature-programmed reduction method.
Abstract: The catalysts M-Y/AC were prepared by incipient-wetness impregnation method and characterized by XRD, H2-TPR and BET analysis. The experiments of simultaneous removal for SO2 and NO over M-Y/AC catalyst were conducted in a fixed bed reactor using CO as reducing gas. Ni-Y/AC catalyst shows an excellent desulfurization and denitration performance. As the catalyst is loaded with 0.5% of Ni and 6% of Y, the t90 of SO2 and NO removal in the absence of oxygen is 370℃ and 360℃, respectively.
Abstract: A wet ball-milling method followed by calcination was adopted to prepare nanocrystalline Li4SiO4 materials by using different silicon and lithium sources. X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were applied to characterize the structure and morphology of the as-prepared Li4SiO4 materials. CO2 uptakes and recycle stability of the prepared Li4SiO4 materials were investigated on a thermogravity (TG) analyzer. Absorption equilibrium of 27.9% was achieved within 10 min at 550℃ and CO2 partial pressure of 2.5×104 Pa. The prepared nanocrystalline Li4SiO4 material kept the original absorption properties after 5 capture-regeneration cycles, indicating the good cycle stability. A mixture of 25% CO2-25% N2-50% He was introduced through the Li4SiO4 absorption bed, showing that CO2 can be efficiently captured at 550℃. The adsorption capacity showed no significant decrease in the presence of 10% humidity.
Abstract: Barium modified Cr2O3/Al2O3 catalysts were prepared by incipient impregnation. The catalysts were characterized by XRD, BET, NH3-TPD and O2-TPO and tested for isobutane dehydrogenation in a fixed-bed reactor at 560℃, 10 mL catalyst, pressure of 0.1 MPa, GHSV of 400 h-1 and atmospheric pressure. The results showed that the addition of Ba leads to the aggregation of Cr2O3, but no significant influence on the structure of the catalysts is observed. The surface acidity of the catalysts is weakened by the addition of Ba, which thereby inhibits the side reactions of cracking and carbon formation while the isobutene selectivity and stability of catalysts are improved. The optimal catalytic performance can be obtained when BaO content is around 3%.
Abstract: MgO-supported nickel catalysts were prepared by impregnation and hydrothermal coprecipitation methods; they were characterized by XRD, N2 sorption, H2-TPR, TEM and TG and used in the steam reforming of biomass oil model compound-phenol for hydrogen production. The results indicated that the NiO/MgO solid solution prepared by the impregnation method displays higher surface area (60.6 m2/g) and larger pore diameter (10.1 nm), in comparison with that prepared by hydrothermal coprecipitation. After reduction, the mesoporous Ni/MgO catalyst obtained from impregnation exhibits small and uniform Ni nanoparticles (5.0-6.0 nm) with high dispersion (19.44%). As high surface area is favorable for the dispersion of Ni nanoparticles and mesoporous structure can promote the mass transfer of reactants and products, the Ni/MgO catalyst exhibits high activity as well as excellent coke resistance ability and long-term stability in the steam reforming of phenol.
Abstract: The effect of acid and basic sites, support, cesium precursor and cesium loading on the performance of supported Cs catalysts in the etherification of phenol with methanol to anisole was investigated. The results illustrate that the cations of basic sites play an important role in the selective conversion of phenol to anisole; the basic sites give higher selectivity to anisole than the acid sites. The catalytic activity in phenol etherification decreases with the increase of the cesium ion binding energy, which is related to the support used. Moreover, the support also has an influence on the amount of strong basic sites, which is related to the selectivity to anisole; high amount of strong basic sites may promote the side reaction and decrease the selectivity to anisole. Cs/SiO2 catalysts prepared with various precursors are different in the surface Cs/Si atomic ratio, which may also influence the catalytic activity in phenol etherification; if the cesium loading exceeds the monolayer dispersion of cesium on SiO2, which is nearly 1.0 mmol/g, the average activity of Cs/SiO2 in phenol etherification decreases greatly.
Abstract: MFI/MFI core-shell composite zeolites with a low-silica ZSM-5 core and a high-silica shell were successfully synthesized by secondary hydrothermal crystallization on the low-silica ZSM-5 cores that was pretreated with a basic TPAOH aqueous solution; the preparation parameters for shell growth including the pH value, water amount, and crystallization time were well considered. The crystal structure, surface morphology, core/shell interface, textural properties and surface acidity of the resultant core-shell zeolites were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometer, transmission electron microscopy, N2 physisorption and NH3 temperature programmed desorption. The results indicated that in the core-shell composite zeolites, high-silica ZSM-5 shell with a particle size of 200 nm is well developed on the surface of core crystal. The growth of ZSM-5 shell results in an increase of external surface area, decrease of external acid density and increase of weak acid sites without influencing pore structure. The isomorphous epitaxial growth of high-silica ZSM-5 shells can be effectively controlled under the conditions of a pH value of 8.5, H2O/SiO2 mol ratio of 30 and crystallization for 24 h during the secondary crystallization.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
