Abstract: A thermogravimetric analyzer and in-situ heating microscope were used to study gasification reaction of coal char particles on the interface of ash layer and slag at 1100, 1200 and 1300 ℃, using typical Ningdong coal-Yangchangwan coal as gasification raw material. The results show that the shape change of ash layer interface and slag interface under different gasification temperature is the main factor that affects the gasification reactivity of coal char particles. When the gasification temperature is 1100 ℃, the ash layer shrinks and wraps on the surface of coal char particles at high temperature, preventing the contact between gasifying agent and coal char particles and reducing the gasification reaction of char particle. However, the interface of slag does not change significantly, and the gasification reaction rate of coal char on the slag interface remains unchanged. When the gasification temperature is 1300 ℃, the interface of both ash layer and slag turns into a liquid phase. Under the surface tension, the char particles are broken, the effective reaction area became larger, and the heat transfer rate increases, thereby increasing gasification reaction rate of the coal char.
Abstract: Char samples were prepared by pyrolysis of oily sludge and blended coal at 850-1150 ℃. The pore structure and crystallite structure of chars were analyzed by N2 adsorption-desorption and X-ray diffraction (XRD). Effects of pyrolysis temperature and amount of oily sludge on gasification reactivity of the char was investigated by thermogravimetric analysis (TGA). The results show that increasing pyrolysis temperature and adding oily sludge can promote the formation of more abundant pore structure of chars, strengthen chars-CO2 gasification reaction and inhibit graphitization process of chars, thus improving gasification reactivity of the chars. However, too high pyrolysis temperature or too much sludge will also result in dense structure or pore plugging of coal char, and reduce gasification reactivity of the char.
Abstract: The chemical structure, content and distribution of sulfur forms in coal and coke of four high-sulfur coking coals were characterized by FT-IR, Raman, TG, and sulfur K-edge XANES technique, and effects on sulfur transformation during pyrolysis were also investigated. The results show that sulfur transformation behavior is related to the sulfur forms in coal as well as the release of volatile matters during pyrolysis. For lower rank coking coals, decomposition of unstable aliphatic structure releases plenty of volatiles with wider range. The interactions between sulfur radicals from cleavage of sulfur forms and hydrogen-rich radicals in volatiles promote release of sulfur into gas phase. This increases total sulfur removal and results in the higher content of thiophene in coke bulk than that on coke surface, while sulfide compounds have an opposite distribution. The degree of aromatization and relative content of thiophene increase with increasing coal rank, leading to lower desulfurization rate and unapparent difference of sulfur distribution between bulk and surface of coke. Inorganic sulfur removal is related to degree of decomposition of pyrite directly, and inter-conversions of sulfur species during pyrolysis process would generate new inorganic sulfur and retain in coke ultimately. Organic sulfur removal is determined by the coal structure and organic sulfur forms, and decreases obviously with increasing coal rank.
Abstract: The medium temperature pyrolytic coal tar was used as raw material and was analyzed, in which the fraction with boiling point > 350 ℃ that contains the resin of 30.88%, the asphaltene of 37.27% and the tetrahydrofuran insolubles of 3.36% is difficult to hydrocrack directly by conventional fixed bed. A Mo-based ultra-dispersed catalyst was synthesized, and characterized by FT-IR, XPS, XRD, SEM and TEM, etc. The catalyst contains Mo=O and Mo-S characteristic structure and has an excellent dispersibility in the reaction system, and the vulcanization ratio of molybdenum reaches 84.34%. The catalyst can be decomposed into hyper dispersive MoS2 particle in the reaction system. The suspension bed hydrocracking experiments were carried out in a 0.25 t/d continuous unit with heavy fraction of tar. Moreover, the effects of reaction conditions on product distribution and coking rate were investigated. The optimum reaction conditions were 19 MPa, 440 ℃ and 300 mg/kg of catalyst addition. Under these conditions, the naphtha yield is 24.47%, the diesel fraction yield is 49.71%, and the coking rate is 1.32%.
Abstract: The effect mechanism of Ca on nitric oxide (NO) heterogeneous reduction by char was investigated using density functional theory (DFT). The electronic structure of char model was analyzed to predict reactive sites. Mayer bond orders were used to quantify formation and breaking of chemical bonds in the reactions. There is a region with high electron localization function values in the extended outer region of unsaturated carbon atoms at the edge. The minimum electrostatic potential of char model, -101.1 kJ/mol, also exists at the edge, indicating the presence of lone pair electrons on edge carbon atoms. The doping of Ca could promote adsorption of the first NO molecule, but has little effect on that of the second NO molecule. The activation energy of rate-determining step is 124.4 kJ/mol for heterogeneous reduction of NO at the edge of char, whereas it is 91.9 kJ/mol at the Ca-decorated char edge. The kinetic analysis shows that the anterior factor increases after doping of Ca, meaning more sites are activated. The promotion of Ca to NO heterogeneous reduction is attributed to combination of the above two aspects.
Abstract: The influence of strontium doping on the adsorption of methanol on calcium oxide surface was investigated by molecular simulation. The model for methanol adsorption onto the CaO(100) and CaO(100)-Sr surfaces was constructed; the adsorption energy and activation energy were then calculated and the density of states was portrayed for the methanol bond on the calcium oxide surface. The methanol activation degrees on the calcium oxide surface before and after strontium doping were then compared by analyzing the Mulliken atomic charge population and deformation density. The results illustrate that the adsorption of methanol onto the calcium oxide surface can be significantly enhanced through the strontium doping; moreover, the enhancement increases with an increase in the doping content of strontium. After doping calcium oxide with strontium, the energy required for methanol activation is reduced; as a result, the strontium doping can also enhance the activation degree of methanol, as methanol is activated upon adsorption onto the calcium oxide surface.
Abstract: In order to achieve the low-temperature (200-250℃) NH3-SCR, highly dispersed VOx-MnOx/CeO2 catalysts with different exposed facets were produced. The NH3-SCR performance results indicate that the NO conversion over VOx-MnOx/CeO2-R with preferentially exposed {110} facets can achieve NO conversion >95% over a wide temperature span of 220-330℃. From the in-situ DRIFTs, gaseous NH3 and NO are favorable to be absorbed on the surface of the VOx-MnOx/CeO2-R catalyst with preferentially exposed {110} facets, which improves the efficiency of NO conversion. The mechanism study via in situ DRIFTs demonstrates that the well dispersed vanadium species on CeO2 {110} absorb NH3 to generate NH3(L) and NH4+(B) species, which in turn become highly reactive toward bridging nitrate and bidentate nitrate species to form N2 and H2O according to the Langmuir-Hinshelwood mechanism.
Abstract: A series of V-Mo/TiO2 catalysts were prepared by impregnation method, sol-gel method and hydrothermal method. The denitrification performance and anti-SO2/H2O performance of the catalysts were investigated.The physical and chemical properties of the catalyst were characterized by XRD, BET, NH3-TPD, H2-TPR and XPS.The results showed that the catalyst prepared by sol-gel method had smaller grain size, larger specific area and pore volume, more surface acidity, stronger redox ability and higher V4+ and surface active oxygen.Therefore, the 3% V2O5-6% MoO3/TiO2 (sol-gel) catalyst exhibited the best denitration efficiency in the temperature range of 80-360℃. After introducing 10% H2O and 0.03% SO2, the NO conversion of 3% V2O5-6% MoO3/TiO2 (sol-gel) catalyst decreased by only 7 percentage points, showing the best resistance to SO2/H2O.
Abstract: Ag(x)/ZSM-5 (x=3, 6, 9) catalysts for selective catalytic reduction of nitric oxide by methane (CH4-SCR) were prepared by impregnation method. The physicochemical properties of the catalysts were characterized by XRD, SEM, NH3-TPD, Py-FTIR, XPS and NO-TPD. The catalytic performance for selective catalytic reduction of nitric oxide by methane was evaluated in a fixed-bed micro-reactor under atmospheric pressure and the influence of Ag loading were investigated.The results show that the impregnation of Ag has changed the acidity and amount of acid of the catalyst and improved the adsorption and desorption performance of NO on ZSM-5 molecular sieve. With the increase of Ag loading, Ag particle size increases and results in higher methane activation as well as the denitration activity of CH4-SCR over Ag(x)/ZSM-5 catalyst. Ag(9)/ZSM-5 has better denitration activity and the NO conversion is 41.87% at 350℃.
Abstract: A series of Ce-Mn/ZSM-5 catalyst with different mass ratios of Ce and Mn was prepared by impregnation method, and the influence of Ce loading on denitrification performance was investigated in a fixed-bed reactor. XRD, TEM, NH3-TPD, H2-TPR, in-situ DRIFTS were used to characterize the catalysts. The results show that the bimetallic Ce-Mn/ZSM-5 have a broad active temperature window. Especially, the catalyst with Ce/Mn mass ratio of 0.4 has the best denitrification efficiency, and the denitrification rate can be higher than 80% between 266 and 465℃, and up to 97.28% at 370℃.Manganese and cerium species can be well dispersed on the surface of the support without changing the crystal structure of ZSM-5.0.4Ce-Mn/ZSM-5 catalyst has abundant acidic sites, good redox performance. There are both E-R mechanism and L-H mechanism in NH3-SCR reaction.
Abstract: The LaNiO3 perovskite support was synthesized by sol-gel method. The CuO/LaNiO3 catalyst was prepared by impregnation method. The catalyst was characterized by XRF, XRD, BET, H2-TPR and XPS. The effect of calcination temperature of LaNiO3 perovskite on the structure of CuO/LaNiO3 catalyst and its catalytic performance for methanol steam reforming were investigated. The results show that the calcination temperature of the support mainly affects the surface oxygen vacancy of the catalyst, the interaction between the active component and the support. When the calcination temperature of the support is 800℃, the surface of the catalyst has more oxygen vacancy, and the interaction between the active component and the support is stronger. Therefore, the hydrogenation activity of methanol steam reforming is higher.
Abstract: Three Ni/Al2O3 catalysts were prepared with different aluminum sources by the solution combustion method and characterized by XRD, H2-TPR, NH3-TPD, N2 sorption, TG-DTG and TPH. The effect of aluminum source on the structure and performance of Ni/Al2O3 catalysts in CO2-CH4 reforming was then investigated. The results show that the NiNO-AlNO catalyst with Al(NO3)3·9H2O as aluminum source owns a large surface area of 102 m2/g and a wide and intense high-temperature reduction peak; besides, the Al2O3 support displays certain crystallinity. In contrast, the NiNO-AlSO and NiNO-AlCl catalysts, prepared with Al2(SO4)3·18H2O and AlCl3·6H2O sources, respectively, are composed of amorphous Al2O3 as support and crystal Ni as active component; the Ni species is poorly dispersed and present as large grains, with a small reduction peak and weak interaction with the support. In particular, because of the high stability of Al2(SO4)3 and difficulty in converting Al2(SO4)3 to active Al2O3 at high temperature, certain sulfur-containing substances are preserved and the resultant NiNO-AlSO catalyst shows strong surface acidity. The catalytic evaluation results indicate that the NiNO-AlNO catalyst exhibits high activity and stability in the CO2-CH4 reforming; the conversions of CH4 and CO2 are 31.21% and 48.97%, respectively. The carbon deposition analysis illustrates that the content of deposited carbon (present mainly in the amorphous form) on the NiNO-AlNO catalyst is rather low, suggesting a high resistance against carbon deposition.
Abstract: A series of CeO2-ZrO2-MnOx catalysts with different Mn contents (denoted as CZMX, where X is the molar fraction of MnOx) were prepared by the redox precipitation method; the effect of Mn content on the catalytic performance of CZMX in the oxidative degradation of toluene was then investigated. The results indicate that that the CZM0.6 catalyst exhibits the best performance in toluene oxidation; a complete conversion of toluene can be achieved at 230℃. The XRD results suggest that the crystallinity of CZMX decreases first, steps over the valley and then increases again with the increase of Mn content. From the H2-TPR characterization, in contrast, a volcanic tendency is observed for the interaction among Ce-Zr-Mn. In particular, the CZM0.6 catalyst displays poorest crystallinity and strongest Ce-Zr-Mn interaction, which can enhance the surface oxygen species. Meanwhile, the Raman and O2-TPD results prove that the abundant oxygen vacancies on the catalyst surface can promote the migration of surface active oxygen species and then enhance the catalytic performance of CZMX in toluene oxidation. In addition, the in-situ DRIFTS results illustrate that the reaction of toluene oxidation over the CeO2-ZrO2-MnOx catalysts proceeds via benzoic acid as the essential intermediate, which is rapidly converted to CO2 and H2O in the presence of O2.
Abstract: The Ag-Y/MIL-101 adsorbents were successfully prepared via loading Ag and Y onto MIL-101. The adsorbents were characterized by XRD, SEM-EDS, BET and TG-DTG methods. The effects of the loading order and concentrations of metals, the amount of AgNO3 solution and Y(NO3)3 solution, and the loading residence time on adsorptive removal performance of thiophene were studied. The conditions of adsorptive desufurization were also optimized. The results show that the lattice structure of MIL-101 remains after the introduction of metals. Compared with MIL-101, the specific surface area and pore volume of Ag-Y/MIL-101 decrease. The optimal preparation conditions of Ag-Y/MIL-101 adsorbent are to load Ag first and then Y with 30 mmol/L of both the loading concentrations of Ag and Y ion, 1 mL of both the dosages of AgNO3 solution and Y(NO3)3 solution, and 8 h of the loading residence time. The optimal desulfurization conditions are 10 mL of model oil, 0.05 g of Ag-Y/MIL-101 dosage, the adsorption temperature of 60℃, and the adsorption time of 8 h. At these conditions, the thiophene desulfurization capacity over Ag-Y/MIL-101 reaches 21.7 mg/g. The Ag can significantly improve the adsorption sulfur capacity of MIL-101, and Y can significantly improve the adsorption selectivity of MIL-101. Therefore, the synergistic effect of Ag and Y in Ag-Y/MIL-101 adsorbent makes it have higher sulfur capacity and thiophene desulfurization selectivity than MIL-101.
Abstract: Thermal oxidation stability is one of the important properties for evaluating fuel quality during the storage and use of endothermic hydrocarbon fuels; it reflects the extent to which jet fuel is affected by dissolved oxygen below 260℃ and the depth of oxidation reaction. In this work, the basic properties and thermal stability of endothermic hydrocarbon fuels with oxygen scavengers were evaluated by accelerated oxidation method combined with titration, infrared spectroscopy, particle size distribution and JFTOT. The effect of three oxygen scavengers, viz., triphenylphosphine (TPP), dicyclohexylphenylphosphine (DCP) and 1, 2, 5-trimethylpyrrole (TMP), on the auto-oxidation process of endothermic hydrocarbon fuels were comparatively investigated and the optimal addition amount within the test range was determined. The results show that there is no significant change in the fuel composition and basic physical properties after the addition of oxygen scavengers. The dissolved oxygen concentration in the fuel decreases with the increase of the amount of oxygen scavengers, and the maximum drop is 31.95 mg/m3. The peroxide value and acid value of the samples show different degrees of decline after accelerated oxidation, and the particle size distribution of the micelles tends to be smaller. The JFTOT test results can meet the national standards. In general, the addition of oxygen scavenger can effectively improve the thermal oxidation stability of the fuel; the effect of three oxygen scavengers follows the order of TMP >TPP ≈ DCP and the optimal addition amount is 1.5×10-5 (by mass fraction).
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
