Abstract: Baishihu lignite was subjected to Soxhlet extraction by tetrahydrofuran (THF). The extract was reacted with iodomethane in the presence of silver tetrafluoroborate and converted to methylsulfonium salts. The methylsulfonium salts and nitrogen compounds were characterized by electrospray ionization (ESI) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Combined with sulfur and nitrogen chemiluminescence detectors (GC-SCD and GC-NCD), the forms of sulfur and nitrogen compounds in THF extracts were studied. The results showed that S1, S2, N1 and N1O1 class species were identified in THF extract. The sulfur and nitrogen compounds were mostly dibenzothiophene and carbazole compounds.
Abstract: The effect of different additives on sintering characteristics of Wucaiwan coal ash was studied by TMA combined with XRD, in-situ hot stage microscope and FactSage thermodynamic software. The results show that the additives could improve the sintering problems of coal ash, but the effect of different additives on sintering characteristics is various. For example, the sintering temperature increases by 70 ℃ when 10% of the sand is added, but the sintering temperature does not increase by addition of coal gangue in the range of 0-15%. Further studies show that the variation of sintering characteristics can be attributed to the change of initial liquid phase temperature, compositions, content and decomposition temperature of sulfates in coal ash.
Abstract: Xiaolongtan lignite was upgraded by hydrothermal dewatering (HTD). The main factors affecting slurry-ability of the lignite including coal property, oxygen functional groups, surface hydrophilicity, and particle size distribution were analyzed. The effect of HTD on solid concentration, rheology, and stability of the upgraded coal was also investigated. The results show that a substantial amount of moisture was removed, oxygen content decreased, and the coal rank was enhanced by HTD upgrading. The contact angle between coal and water increased after removal of oxygen functional groups by HTD, thereby improving surface property of the upgraded lignite. A typical bimodal distribution of the lignite particle size was observed. The mean particle diameter of lignite decreased and the lignite particles became more regular after HTD. HTD upgrading significantly improved slurry-ability of the lignite. The solid concentration of raw coal was 44.09%, while that of the upgraded coal after HTD increased to 61.94%. The consistency coefficient K decreased, while the rheological index n increased for the CWS prepared from the upgraded coals. HTD upgrading decreased the apparent viscosity, and maintained the shear-thinning behavior of pseudo-plastic fluid. Moreover, as the water separation ratio decreased and formation of hard sedimentation was delayed, stability of the CWS was enhanced after HTD upgrading. Overall, the physico-chemical properties of Xiaolongtan lignite were significantly modified after HTD, thus a high-quality slurry fuel with high solid concentration, superior pseudo-plastic behavior, and good stability could be achieved.
Abstract: Density functional theory was used to investigate the reaction pathways for the reduction of NO by nitrogen-containing char with char-bound nitrogen, viz., char(N); the reaction paths of heterogeneous reduction of NO by char(N) were analyzed from the thermodynamic and kinetic point of view. The results show that the energy barrier of the rate-determining step via the indirect NO reduction path by char(N), viz., first producing NH2 intermediate and then reducing NO, is 183.76 kJ/mol higher than that via the direct heterogeneous NO reduction path, suggesting that the later direct heterogeneous NO reduction path is more favorable. Thermodynamically, the direct heterogeneous NO reduction by char(N) is a spontaneous and exothermic process in the coal combustion system. Kinetically, the rate constant of the rate-determining step in indirect NO reduction path by char(N) is at least 10 orders of magnitude lower than that in direct heterogeneous reduction, also illustrating the superiority of the direct heterogeneous NO reduction path by char(N).
Abstract: The upgrading of coal tar by means of steam catalytic cracking (SCC) is a promising method. In this study, Al/Ce and Al/Zr co-doped Fe2O3 catalysts were prepared and used for SCC of coal tar for improving the light tar yield. The SCC was conducted at 550 ℃ for 1 h. It was found that the crystal size decreased over doped Fe2O3 catalysts, and the pore volume and specific surface area increased. XPS analysis showed that lattice oxygen was the majority oxygen species and doping can increased the O- concentration. It was shown that Al/Ce and Al/Zr co-doped Fe2O3 could improve the catalytic activity of Fe2O3. The light tar yield over FeAlZr1, FeAlZr2, FeAlCe1 and FeAlCe2 were 63.2%, 58.1%, 60.2% and 55.1%, respectively, higher than that on Fe2O3 being 49.7%. The oxygen species from steam dissociation and Fe2O3 could take part in the upgrading of coal tar. It was revealed that the specific surface area and the O- on the Fe2O3 catalysts were the primary factors in determining the SCC performance.
Abstract: To get more insight into the pore structure characterization of nanoporous biomass chars, different probe molecules, models, and calibration steps were used and compared. The coconut shell chars (CSCs) were prepared under a steam atmosphere and characterized using N2, Ar, and CO2 adsorption. The results show that coconut shell chars are suitable for further activation, due to the high carbon content and abundant porosity. Ar adsorption with application of Non-Local Density Functional Theory (NLDFT) model can more accurately characterize the pore structure of CSC. When the calibration step is performed before adsorption measurement, the important results of N2 and Ar adsorption, such as pores size distribution (PSD) and isotherm, are affected by pore blocking, leading to the erroneous understanding of CSC in special applications. Vacuum treatment at 273 K for 1 h after He calibration is enough to remove He, which could reduce effect of pore blocking.
Abstract: The reactivity of biomass with CoFe2O4 oxygen carrier was investigated through thermodynamic analysis. The effects including amount of oxygen carrier, temperature and steam content on gasification characteristics of biomass were examined. Meanwhile, the reaction was experimentally investigated using thermogravimetric analysis. The phase of fresh and reacted oxygen carrier was characterized by X-ray diffraction (XRD).Thermodynamic analysis results show that CoFe2O4 can provide lattice oxygen and effectively improve gasification of biomass and carbon conversion efficiency. As the temperature goes up, amount of H2 and CO increases, while CO2 decreases. With amount of steam increases, H2 and CO2 yield increases while CO yield decreases. The ratio of H2 to CO increases and high quality syngas can be obtained with the addition of steam. Thermogravimetric analysis and XRD results show that cobalt can be first reduced which can promote the further reduction of iron due to the synergistic effect. With the amount of oxygen carrier increases, reduction degree of oxygen carrier decreases. The optimal mass ratio of oxygen carrier to biomass is 0.8.
Abstract: In order to separate and enrich the high value-added chemicals in bio-oil, solvent extraction and distillation methods were combined to separate and purify bio-oil. Ethyl-acetate, dichloromethane, diethyl ether and toluene were elected as extracting agents, which were mixed with bio-oil in a certain mass ratio. The 4 oil phases distilled from four extract phases were compared with bio-oil to study effects of different solvents on the yield, moisture and high value-added components of distillate. The results show that the distillate had higher yield and lower moisture content compared with that of bio-oil after the extraction and distillation. Among the 4 solvents, toluene had the poorest ability to extract high value-added components of bio-oil, achieving the lowest yield of phenols of distillate. The extraction efficiency of ethyl-acetate and diethyl ether was higher than that of toluene, but the contents of high value-added components in their oil phases were lower than those of others. The relative content of guaiacol and its derivatives was 34.11% in the oil phases of dichloromethane, which was 15.52% higher than that of bio-oil, and conducive to further extract for high value-added chemicals such as guaiacol and its derivatives.
Abstract: To solve the problems of chlorine loss and equipment corrosion caused by the conventional alumina-type reforming catalyst, zeolite L was modified with Ce3+ by ion exchange method and with Ce3+-modified L (CeL) as the support, the Pt/CeL reforming catalyst without any chlorine was prepared by impregnation method. The CeL support and Pt/CeL catalyst were characterized by XRD, N2 adsorption-desorption, NH3-TPD and Py-FTIR; the catalytic performance of Pt/CeL in aromatization was investigated in a continuous-flow fixed-bed micro-reactor, with an industrial hydrofining naphtha containing 0.50 μg/mL sulfur as the feedstock. The results indicate that the modification with Ce3+ by ion exchange has little influence on framework structure of zeolite L; however, it can raise the acid content and acid strength of the CeL support and then remarkably enhance the performance of the Pt/CeL reforming catalyst in aromatization. The activity and selectivity of the Pt/CeL catalyst are comparable to those of the commercial alumina-type reforming catalysts, suggesting that proper acidity can facilitate the aromatization reaction.
Abstract: The objective of this work is to investigate the effect of Al contents on the performance of methanol-synthesis catalysts. A series of catalyst samples with various Al contents were prepared with fractional precipitation method, and characterized with methods including XRD, TG-MS, XRF, N2 physisorption and H2-TPR. Results show that Al addition affected the subcarbonate structure in precursors, which promoted the formation of high temperature carbonates, and thus has an effect on the catalyst performance. With Al addition, the BET surface area of the calcined catalysts, catalyst activity and thermostability increased to different degrees. When the molar ratio of Al3+ in catalyst increased to 30%, the CO conversions before and after heat treatment were 76% and 67%, respectively, at the conditions of 230 ℃, 4 MPa and syngas composition of 13%CO, 1.2%CO2, 80%H2 and 5.8%Ar. The catalyst sample with 0.3 of Al3+/(Cu2++Zn2++Al3+) molar ratio remains good catalyst performance.
Abstract: Ni/W-USY/Al2O3 with full mesoporous structure was prepared and used for hydrocracking of Fischer Fropsch wax. The catalyst was evaluated for its reaction performance, product characteristics and catalyst properties change. In a 312 h experiment, the result showed that the catalyst possessed high initial activity, and maintained stable after 120 h, and did not show obvious deactivation afterward. When the heavy wax conversion reached 73.95% at the stable stage, the fuel oil selectivity reached to 98.46% and C3, 4 constituted the most cracked gas. Gasoline, kerosene and diesel, as the products, were transparent and composed of paraffins and iso-paraffins substituted by methyl-groups. The iso-paraffin contents in the three products were 63.98%, 52.26% and 48.90% respectively. The fresh catalyst contained two main active states of WS2 and NiWS, had good metal dispersion and rich mesoporous structure. With transition from high activity to stable state of the catalyst property, part of W migrated and formed more Ni-S-W bonds with Ni, and some W-S bonds broke to form W-W bonds after releasing S, resulting in the increase of active states of NiWS and the decrease of WS2, and forming more Brönsted acid sites and less Lewis acid sites.
Abstract: The metal-organic framework of Cu3(NH2BTC)2 was synthesized by solvothermal method with the prepared grafted amine-based trimesic acid as organic ligand. The synthesized adsorbent was characterized by XRD, N2 adsorption-desorption, thermogravimetry, FT-IR and in-situ FT-IR. The performance of the CO2 adsorption was studied by the breakthrough curve based on the fixed-bed reactor. The results showed that the amine groups had been successfully grafted into the skeleton of Cu3(BTC)2. The CO2 adsorption capacity of Cu3(NH2BTC)2 was improved to 1.41 mmol/g at 10 kPa and 50 ℃. The improvement of CO2 uptake might due to the effect of both the physical and chemical adsorption of CO2.
Abstract: The CeO2-doped CaO-based sorbent was prepared by the homogeneous precipitation method using P123 as the soft template. The influence of CeO2 doping on the capture of CO2 was investigated. The CeO2 doping can promote the formation of surface oxygen species, and facilitate the carbonation reaction. The interactions in CaO-CeO2 lead to the electrons transfer from Ca to surface oxygen species. Moreover, when Ce ions are substituted by Ca ions, the charge neutrality is destroyed in the CeO2 crystal, which promotes the formation of oxygen vacancies and O2-. Ea is tested to be 28.1 kJ/mol for the carbonation reaction of pure CaO sorbent, while Ea decreases to the minimal value of 10.2 kJ/mol when adding CeO2 to CaO sorbent with a Ce/Ca molar ratio of 0.25. Also, the doping of CeO2 is beneficial to the high dispersion of CaO and prevention of CaO sintering. The Ce-doped sorbents exhibit a superior capture capacity and cyclic stability in carbonation/calcination cycles.
Abstract: Coconut char is prepared by pyrolysis and used as the fuel for the direct carbon solid oxide fuel cell (DC-SOFCs), which are composed of yttrium-stabilized zirconia (YSZ) electrolyte and silver and gadolinium-doped ceria (Ag-GDC) cermet electrodes. The microstructure and composition of coconut char are characterized and the performances of DC-SOFCs with coconut char as fuel was investigated. The results show that the as-prepared coconut biochar has a mesoporous structure and a particle size of several microns; moreover, it contains K and Ca elements, favorable for the Boudouard reaction. A peak power density of 255 mW/cm2 is observed for the DC-SOFC operated at 800 ℃ with coconut char as fuel; it increases to 274 mW/cm2 when the char is loaded with Fe as a promoter to improve the reverse Boudouard reaction. The discharging time of the cell with 0.5 g Fe-loaded coconut char operated at a constant current density of 0.5 A/cm2 lasts for 17.6 h, representing a fuel conversion of 39%, demonstrating the feasibility and superiority of coconut char as a fuel for DC-SOFCs.
Abstract: Ce-TiO2 and Ce-Co-TiO2 powders were prepared by the sol-gel hydrothermal method with butyl titanate as the source of Ti, cerium nitrate as the source of Ce, cobalt nitrate for Co source. The modified TiO2 catalysts were characterized with BET, XRD, SEM, UV-vis, XPS and NH3-TPD. The NO reduction efficiency by visible light over the modified TiO2 catalysts was carried out. The experimental results show that the catalyst Ce (1% molar)-Co (5% molar)-TiO2 prepared under the conditions of 24 h hydrothermal synthesis at 160 and 200 ℃of calcination showed the best performance. At room temperature, the visible light catalytic efficiency of the catalyst reached 92.69% when the NO initial concentration was 762 μg/m3. When the NO initial concentration was 1148 μg/m3, the visible light catalytic efficiency could still reach 85.94%, which was improved by nearly 50% compared with pure TiO2. Moreover, it was found that in the resistance of SO2 and continuous usage, the efficiency of the Ce (1%)-Co (5%)-TiO2 catalyst was better than the commercial catalysts (TiO2 with V2O5 doping).
Abstract: The siderite denitration catalysts modified by Ce and Zr were prepared by mixing and stirring method. The effects of Ce and Zr co-doping on the catalytic denitration performance and sulfur resistance of the catalyst were studied. The results show that the 3%Ce+3%Zr-doped siderite catalyst(Ce0.03/Zr0.03-siderite) has the highest catalytic denitration activity and good sulfur resistance. The catalytic denitration efficiency is above 92% in the temperature range of 180-330 ℃. Furthermore, the denitration efficiency is still more than 95% after introducing SO2 gas with a volume fraction of 0.01% for 8 h at 210 ℃. The characteristics of the catalyst, such as components, microporous structure and crystal phase were determined by XRF, BET, XRD, NH3-TPD, TG and other experimental means. The characterization results show that the doping of Ce and Zr can significantly improve the specific surface area and surface crystal dispersion of the catalyst, enhance the surface acidity of the catalyst, and promote the decomposition of ammonium sulfate on the catalyst surface; thus the modified siderite catalyst has an excellent low-temperature catalytic denitration activity and a good sulfur resistance.
Abstract: A series of Mn-Ce catalysts with different Mn/Ce ratios were prepared by a redox co-precipitation method and characterized by N2 sorption, XRD, XRF and XPS; their catalytic performance in lean methane combustion was investigated. The results indicate that the Mn/Ce ratio has a great influence on the activity of Mn-Ce catalyst in lean methane combustion. With an increase of the Mn/Ce ratio from 3:7 to 9:1, the activity of the Mn-Ce catalyst increases gradually and the reaction temperature needed for a methane conversion of 50% (t50) decreases from 501 ℃ to 446 ℃; however, a further increase in the Mn/Ce ratio may lead to a decrease in the catalytic activity. The performance of Mn-Ce catalyst is related to many factors such as the surface area and the concentration of higher valence manganese (Mn4+) species, lower valence cerium (Ce3+) species and lattice oxygen; in particular, KMn8O16 is of benefit to enhancing the activity of Mn-Ce catalyst.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
