Abstract: One coal and two representative fly ashes from the Shell gasification process were used in the study. One fly ash was the captured fly ash, and the other was taken from the heat exchanger. The particle size distribution, chemical composition, surface morphology of samples were studied by laser particle analyzer, X-ray fluorescence spectrometer and scanning electron microscopy respectively to explore the mechanisms of adhesion. The enrichment coefficient was used to describe the element migration from the coal to the fly ash. The results show that the formation of iron-bearing minerals and the enrichment of Na, K, Fe, S, P especially the enrichment of Na and Fe on the surface of fly ash particles are the main factors on the adhesion.
Abstract: The effect of calcium on the adsorption of NO on char surface was studied by using density functional theory. Periodic boundary graphene model was adopted to simulate the graphitic structure of char surface; the catalytic effect of calcium on NO adsorption was investigated by decorating the graphene surface with calcium atoms which have a coverage rate of 13.3%. The results demonstrated that NO is physically adsorbed on the pristine graphene surface, with a binding energy of -19.34 kJ/mol; after decorating the graphene surface with calcium atoms, the adsorption is turned into a chemical sorption with a binding energy of -206.02 kJ/mol, due to the transfer of electrons in 4s and 3d orbitals of Ca atom to the NO molecule.
Abstract: The burning behaviors of Datong coal and char under O2/N2, O2/CO2 and O2/H2O/CO2 atmosphere were comparatively investigated by thermogravimetric analyzer. The influence of CO2 and H2O gasification on the oxy-fuel combustion characteristics of coal and char were mainly studied. The results indicate that at 5% oxygen concentration the burning rate of pulverized coal in each atmosphere decreases in the order of O2/N2, O2/CO2 and O2/H2O/CO2. When the oxygen concentration reduces to 2%, owing to the CO2 and H2O gasification, the overall reaction rate of pulverized coal increases in the same order at high temperatures. The burning rate of char is slower in O2/CO2 than that in O2/N2 at 5% oxygen concentration, but as the burning process is delayed, the overall reaction rate of char in O2/H2O/CO2 rises significantly due to the action of gasification. At 2% oxygen concentration, the overall reaction rate of char in O2/CO2 is higher than the burning rate of char in O2/N2 with the rise in temperature. The overall reaction rate of char in O2/H2O/CO2 further increases because the H2O gasification plays a major role in CO2 and H2O co-gasification. The kinetic analysis shows that at 5% oxygen concentration the apparent activation energy in the atmosphere increases in the order of O2/N2, O2/CO2 and O2/H2O/CO2. However, the apparent activation energy of different atmospheres declines with the decrease of oxygen concentration.
Abstract: 2,5-diketopiperazine (DKPs) was selected as N-containing model compound to investigate fuel-N conversion pathway during straw pyrolysis. The experiments were conducted using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer (TG-FTIR) in Ar atmosphere. The results show that NH3, HCN and HNCO are the major N-containing species during DKPs pyrolysis at 20, 40 and 60℃/min. The yield of NH3 is the largest, followed by HCN and the amount of HNCO is the lowest. With increase of heating rate, the weight loss curve moves to right and the yields of HNCO and HCN increase, while that of NH3 decreases. K, Ca and Fe have a catalytic effect on nitrogen conversion during DKPs pyrolysis. In the presence of K and Ca, the formation of NH3 and HCN is enhanced. Fe can promote the formation of NH3, but inhibit the formation HCN.
Abstract: The influence of alkali metal volatilization on the performance of nickel-based catalyst in the steam gasification of cellulose biomass was investigated in a two-stage fixed bed reactor. The results show that potassium is deposited on the catalyst surface with the volatilization of potassium salt during the catalytic steam reforming of potassium-loaded cellulose. The existence and deposition of proper amount of potassium may suppress the coke deposition and enhance the activity of nickel-based catalyst, which is of benefit to producing more hydrogen in the steam gasification of biomass. However, excessive amount of potassium loaded in cellulose may reduce the activity of nickel-based catalyst; moreover, with the repetitious operations, potassium is accumulated on the catalyst surface, which may lead to an obvious inhibitory effect on the activity and stability of nickel-based catalyst in the steam gasification of biomass.
Abstract: The basic physical and chemical properties, yields and organic ingredients of the refined wood vinegar obtained from pyrolysis of Chinese fir sawdust (CFS), cotton stalk (CS) and bamboo sawdust (BS) were investigated. The results show that yields of crude wood vinegar and the refined one from the three biomasses at 350℃ are nearly the same. However, yield of the wood vinegar from KCl-treated CFS (KCl-CFS) under the same conditions decreases. The physical and chemical properties of the three refined wood vinegars are different from each other. The pH value of CFS wood vinegar is the lowest and its density is the highest. The content of the organic acids contained from BS and CS wood vinegars is higher than that of CFS wood vinegar. The organic components in the refined wood vinegars were analyzed by gas chromatography and mass spectrometry (GC-MS). The results indicate that CFS wood vinegar includes acids, phenols and ketones. Besides the three ingredients, alcohols with high relative content are found in BS and CS wood vinegars. The relative contents of the acids and phenols contained in the three wood vinegars are in the order of BS > CS > CFS and that of the ketones is CFS > CS > BS. The relative contents of the phenols and ketones contained in the refined wood vinegar produced from KCl-CFS decrease and that of the acids increases, especially the acetic acid. The relative content of the alcohols contained in the refined KCl-CFS wood vinegar roughly doubles compared with that of CFS wood vinegar.
Abstract: A series of self-reducing bifunctional catalysts Ni-W/SBA-15 were prepared through reduction of metal oxides by reducing gas produced in the calcination process of bio-carbon source. These catalysts were directly applied to the hydrogenolysis agroforestry waste lignocellulose to low carbon polyols. TG and XRD results showed that when added 3.0 g sucrose into catalysts precursors, reduction of active metal oxides was supreme and Ni particles increased gradually as the further increase of Ni. The tungsten species were amporphous state seen from XRD patterns. The micrographs from SEM showed that the nickel and tungsten species were loaded on SBA-15 surface with a good dispersion and the particles were tiny which was beneficial to promote the reaction. Thus, the transformation of microcellulose was complete and low carbon polyols yield was up to 68.14%. In contrast, the target product yield was 52.66% when the wheat straw as the substrate under the reaction condition of 240℃ and 6.0 MPa H2 for 6 h.
Abstract: Ruthenium catalysts supported on carbon nanotubes with different functional groups (MCN, AMCN and GMCN) were prepared by incipient wetness impregnation with ultrasonic-assistance and used for the hydrogenolysis of sorbitol. The catalysts were characterized by X-ray diffraction (XRD), HRTEM, X-ray photoelectron spectroscopy (XPS) and ICP-AES. The effects of functional group species, and base additives on the catalytic performance of Ru/CNTs in the sorbitol hydrogenolysis reaction were investigated. Nearly 99.5% of sorbitol conversion and 47.7% total yield of ethylene glycol and 1,2-propanediol (1,2-PD) could be achieved over Ru/AMCN under mild reaction conditions (205℃, 5.0 MPa), using Ca(OH)2 as additive. The conversion of sorbitol and the selectivity to ethylene glycol (EG) and 1,2-propanediol (1,2-PD) did not decrease over the five repeated runs, which confirmed that the Ru/AMCN catalyst exhibited high stability in the aqueous hydrogenolysis of sorbitol to glycols.
Abstract: Modified with different contents of phosphorus, the NiW/γ-Al2O3 catalysts prepared using the impregnation method were used to catalyze the hydrogenation reaction of naphthalene and the aromatics compounds separated from low temperature coal tar in a fixed-bed reactor. The properties of the catalysts were characterized by N2 adsorption, XRD, H2-TPR, XPS and NH3-TPD. The products were analyzed by GC-MS and GC×GC-TOFMS. Results showed that the addition of P can enhance the distribution of Ni and W compounds on the surface of supports and expand the pore diameter. Adding 1%~1.5%P could generate more Ni-W-O phase and increase the proportion of the weak acid. The results of naphthalene hydrogenation indicated that the highest conversion rate of nearly 80% and the decalin yield of over 50% were achieved when using the NiW+1%P catalyst. For the tests using the catalyst with 1.0%P to catalyze the hydrogenation of enriched aromatics compounds from coal tar, the results indicated that the effect of transforming aromatics into cycloalkanes and the removal of heteroatoms were remarkable in the presence of the catalyst.
Abstract: A series of NiO-Fe2O3 catalysts loaded on palygouskite were prepared by co-precipitation method and used in the catalytic steam reforming to produce hydrogen in a self-made three-stage fixed bed reactor. The loading of NiO-Fe2O3, reaction temperature and ratio of steam to carbon (S/C) on hydrogen production were investigated, with a water-soluble mixture of acetic acid, ethanol and phenol as the bio-oil model compounds. The results indicated that under the optimum conditions, viz., 650℃, an S/C ratio of 8~10 and 50%NiO-50%Fe2O3/PG as the catalyst, the relative content of H2 reaches 66.15% in the gaseous product.
Abstract: The CuWO4/C composite was synthesized via a simple mixing-calcination method and characterized by various techniques including X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller and so on. The removal of dibenzothiophene (DBT) in model oil was studied by using CuWO4/C as catalysts, hydrogen peroxide as oxidant, 1-ethyl-3-methylimidazole ethyl sulfate (EMIES) ionic liquid (IL) as the extractant. Results indicated that the CuWO4/C composite exhibited a much higher desulfurization ratio than pure CuWO4 under the same experimental conditions. The influence of reaction temperature, amount of hydrogen peroxide, amount of extractant on the desulfurization efficiency were investigated. The results indicated that under the optimal reaction conditions of 5 mL model oil, 0.02 g of CuWO4/C, 0.2 mL of hydrogen peroxide, 1.0 mL of extractant, reaction temperature 70℃ and reaction time 180 min, the desulfurization efficiency of CuWO4/C was 98.2%. The catalyst could be recycled 4 times without a significant decrease in activity.
Abstract: In this paper, the adsorption behaviours of naphthalene on two popular mesoporous molecular sieves, SBA-15 and MCM-41 were studied. The adsorption isotherms were obtained, and fitted with isotherm models of Langmuir, Freundlich and D-R. The breakthrough curves of naphthalene at different initial concentrations were measured, and well predicted by the constant-pattern wave model. Results show that the Langmuir model can well describe the adsorption isotherms of naphthalene at low concentration with R2 higher than 99%. The adsorption ability of SBA-15 with a microporous structure is stronger than that of MCM-41 which contains only mesoporous structures. The predictions on breakthrough curves by the constant-pattern model exhibited higher correlation coefficient for SBA-15 than for MCM-41.The overall mass transfer coefficient Ka of naphthalene on SBA-15 is higher than that on MCM-41, indicating that there is a lower mass transfer resistance and the mass transfer equilibrium can be achieved faster over SBA-15.
Abstract: The mixed supports were obtained at different weight ratios of HZSM-5 to MCM-41 by physical mixing processes. Tetraethylenepentamine (TEPA) modified mixed supports sorbents were prepared by the impregnation method. The sorbents were characterized by nitrogen adsorption/desorption, Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) techniques. The effects of mixing ratios of HZSM-5 to MCM-41, TEPA loadings, adsorption temperatures, influent velocities, and CO2 partial pressures on CO2 adsorption capacity were investigated in a fixed bed reactor. It showed that the maximum CO2 adsorption capacity was 3.57 mmol/g of HZSM-5/MCM-41-30%TEPA at the adsorption temperature of 55℃ and influent velocity of 30 mL/min. After ten-cycles, the CO2 adsorption capacity decreased by 8.1%. CO2 adsorption was determined by a two-stage process, a fast breakthrough adsorption and a gradual approaching equilibrium stage. Moreover, the breakthrough adsorption capacity accounted for approximately 80% of the equilibrium adsorption capacity. The Avrami model could fit well with the experimental data of HZSM-5/MCM-41-30%TEPA. It illustrated that the adsorption mechanism was dominated by both chemical and physical adsorption.
Abstract: A series of TiO2-modified magnesium-based sorbents, for thermo-swing absorption process in intermediate-temperature working range (250~500℃), were prepared by precipitation, and characterized by XRD, SEM and N2 absorption etc. The sorbents were evaluated by dynamic absorption-desorption cyclic tests. With the increase of TiO2 amount, the crystallinity of the sample decreased, and the BET surface area also decreased due to the formation of MgTiO3.When the TiO2 content was 2%, uniform particle size (nanostructured spheres with 4.0~5.0μm in diameter) was obtained. The absorption capacity was stabilized from the second cycle of the absorption-desorption cyclic test, and the capacity could reach 6.64% after 50 cycles, suggesting good stability of the sorbent. This should be attributed to the formation of MgTiO3, which provided a rigid framework for the sample and improved the dispersion of active species.
Abstract: The nano V2O5-WO3/TiO2 catalysts were prepared. NaCl was loaded on the catalysts by impregnation and Hg0 was loaded by adsorption. The samples were characterized by XRD, SEM, BET, NH3-TPD and FT-IR measurements to investigate the effect of NaCl and Hg0 on the performance of V2O5-WO3/TiO2 SCR catalysts. Besides, the functional mechanism was proposed combining with previous conclusions. The results indicate that NaCl causes the agglomeration of catalysts, leading to the decrease of BET surface area. For NaCl poisoning catalysts, the deactivation is observed obviously with the increase of NaCl loadings. Brønsted acid sites (-V-OH) are neutralized by Na to ultimately form -V-O-Na and Cl-V-O-Na, resulting in the decline of catalytic activity. Hg0 shows no influence on the microstructure and phase composition of the catalysts. However, it can be adsorbed on the V active sites to weaken the De-NOx activities slightly. When NaCl and Hg0 exist simultaneously, Hg0 will combine with Cl that is introduced from NaCl to form HgCl or HgCl2 and partly replace Na, and -V-O…Hg or-V-O-Hg-Cl is produced finally.
Abstract: Based on V2O5-WO3/TiO2 catalyst, the size distribution, morphology, element compositions and chemical compositions of fine particles at the output of SCR-DeNOx system were analyzed, and the formation mechanism of fine particles were discussed based on DRIFTS systematically. The results show that great quantities of particles can be formed during the process of SCR-DeNOx. The main components of particles are ammonium bisulfate and a small amount of ammonium sulfate. The effects of SCR-DeNOx system on emission characteristics of fine particles attribute to three aspects. Firstly, some SO2 can be oxided to SO3 during SCR process at the function of catalyst, and then SO3 would react with NH3 and H2O to form ammonium sulfate and ammonium bisulfate particles, which is a reversible process simultaneous with the de NOx reactions. Secondly, SO3 can also react with the escaped NH3 and H2O to form ammonium sulfate and ammonium bisulfate particles after SCR system. Moreover, the free alkaline earth metal oxide in the flue gas(such as CaO) reacts with SO3 and changes the physical properties of the fine particles.
Abstract: TiO2/Cu2O composite photocatalysts were prepared by hydration hydrazine reduction method and loaded on activated carbon fiber (ACF). The SEM, XPS, BET and XRD were used to analyze the property changes and reaction behaviors of catalysts. The NO and SO2 removal efficiencies of the catalysts were also investigated. The results show that the pore size of ACF is decreased after modified by TiO2/Cu2O. The surface functional groups including graphite carbon and carbonyl group are increased, which enhance the NO and SO2 adsorption capacity of ACF. The highest desulfurization and denitrification efficiency are 90% and 60% at 40℃ under visible-light.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
