Abstract: The transformation behavior of mineral matters in direct coal liquefaction residue from Shenhua Corporation under gasification atmosphere at high temperatures was examined by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Mssbauer spectroscopy was also applied to investigate the iron-bearing minerals and the valence distribution of iron in ash at different temperatures. The results show that the major minerals in coal liquefaction residue are quartz, calcium sulfate, millosevichite, pyrrhotite, kaolinite, and calcite. At high temperatures, they become anorthite, gehlenite, maghemite and magnetite. Due to the formation of anorthite, gehlenite eutectic, ash of coal liquefaction residue exhibits low fusion temperature. The iron-bearing minerals characterized in ash include maghemite, magnetite, fayalite, and the vitreous matter. The content of iron in vitreous matter increases with increasing temperature. Meanwhile, Fe2+/Fe3+ significantly increases from 1.08 to 2.39 as temperature increases from 1 100 to 1 200 ℃ for the reduction of maghemite, and it is not obviously changed above 1 200 ℃. Furthermore, the liquid phase in ash calculated by FactSage increases with temperature owing to the increase of iron in vitreous phase. In hence, high content of iron in ash from coal liquefaction residue is the major reason for its low ash fusion temperatures.
Abstract: Unreacted ammonia in Selective Catalytic Reduction (SCR) and Selective Non-catalytic Reduction (SNCR) technology may be adsorbed by fly ash and lead to ash blocking in the air preheater or hindering the secondary utilization of ash. Ammonia adsorption by fly ash may have a close relationship to the concentration of ammonia in flue gas. Regarding Ximeng lignite and Yangquan anthracite as the subjects investigated, NH3 Temperature-programmed Desorption (NH3-TPD) was utilized to study the relationship between ammonia chemical adsorption and mineral composition of the ash, the atmosphere of ash production, cooling rate of ash as well as the amount of residual carbon in the ash. The results show that rapid cooling and reduction atmosphere could increase the amount of amorphous phase in the ash and facilitate ammonia adsorption. On the other hand, ash with residual carbon could adsorb more ammonia than mineral ash as a result of acidic functional group on the surface of residual carbon.
Abstract: The pyrolysis of brown coal and the in-situ gasification of "hot" char were carried out in a newly-designed two-stage fixed-bed reactor. Firstly, the brown coal was pyrolyzed in ultrapure argon for 5 s under the temperature of 400 ℃, 600 ℃, and 800 ℃ at the pyrolysis stage. Then the reactor was shifted to the "gasification stage" immediately and the "hot char" obtained at the pyrolysis stage was gasified in-situ for 2~30 min at 900 ℃ with a 15%H2O balanced with argon to obtain a so-called in-situ gasification char. TGA and Raman spectroscope were used to characterize the reactivity and microstructure of char, respectively. Results show that the yields of in-situ gasification char decrease significantly within the initial 10 min, and then decrease slowly with prolonging the holding time further (10~30 min). Plenty of O-containing functional groups are released in the first 2 min during gasification. The ratio of small aromatic ring systems to big aromatic ring systems decreases dramatically within 2 min, and then decreases slowly from 2 min to 30 min. Microstructure of char has an effect on its reactivity. With the char gasification, the amorphous carbon as well as small aromatic ring systems with high activity decreases, leading to the char reactivity decreaseing consequently.
Abstract: Two bituminous coals were extracted with tetrahydrofuran (THF) solvent at 50 ℃ and atmospheric pressure by microwave-assisted extraction. The experiments of methane sorption isotherms, desorption and radial seepage for raw coals and their residues were carried out. The results indicate that the ability to adsorb methane is reduced after extraction of the small organic molecule, and the methane desorption rate is improved. Pore volume and average pore diameter of raw coal is higher than that of the residual coal,while the specific surface area and micropore volume are reduced. After solvent extraction, the desorption velocity and desorption quantity are higher that of raw coal because the resistances of surface mass transfer and diffusion are reduced. Permeability of residues is higher than that of raw coal under the same seepage condition. The gas adsorption is lowered, the internal and external diffusion resistance of methane is decreased, and the gas flow channel in coal is expanded. These behaviors are caused by the change of coal pore structure after dissolving some small organic molecule in coal. Therefore, solvent extraction can change the storage and transportation of coal seam features, which provides the basis for improving the permeability of the coal reservoir with chemical methods.
Abstract: The hydrogasification of Inner Mongolia lignite semicoke to produce methane was investigated in a high-temperature and high-pressure (1 000 ℃, 12 MPa) fixed bed reactor; the specific surface area, pore structure and surface feature of the coke residues were characterized by nitrogen physisorption and scanning electron microscope (SEM). The results showed that the hydrogasification process of semicoke can be divided into three stages, viz., hydropyrolysis, rapid hydrogenation and slow hydrogenation, in which the hydrogenation of oxygen-containing functional group and alkyl side chain, the hydrogenation of aromatic structure, and the hydrogenation of hydrogen depleted carbon skeleton structure take place successively. The optimum reaction temperature and pressure for the semicoke hydrogasification are 800 ℃ and 3.0~4.0 MPa, respectively. An increase of heating rate may shorten the reaction time of earlier hydrogasification stage with a carbon conversion below 46%, but has little effect on the later stage with a carbon conversion above 46%. The nitrogen physisorption of the coke residues exhibits a reversed S-shape isotherm with a H3 hysteresis loop. Along with the progress of hydrogasification, the average pore size of semicoke decreases first and then increases, the total pore volume and mesopore volume increase gradually, whereas the micropore volume and specific surface area increase first and then decrease.
Abstract: Ni/Al2O3 catalyst was selected as the reference catalyst for steam reforming of model bio-oil to produce hydrogen. Ni-Cu/Al2O3, Ni-Co/Al2O3 and Ni-Co-Cu/Al2O3 were prepared to investigate the influence of Co and Ni on steam reforming of bio-oil. The results show that Co can enhance the water gas shift (WGS) reaction rate, and Cu can prevent the formation of coke. The reaction conditions for the steam reforming of bio-oil with the Ni-Co-Cu/Al2O3 catalyst were optimized as the follows: temperature of 900 ℃, water-oil ratio (the mass ratio of steam to oil) of 6 g/g and weight hourly space velocity (WHSV) of 1 h-1. The carbon selectivity of 87.5%, hydrogen yield of 84.2% and potential hydrogen yield of 92.4% can be obtained at the optimum conditions.
Abstract: The reduced pressure distillation of bio-oil and the ethanol with the mixing ratio of 2:3 by weight were subjected to catalytic co-cracking over ZSM-5/MCM-41 molecular sieve in a fixed-bed reactor. The effects of reaction temperature and WHSV on cracking products were investigated. The catalyst is characterized by NH3-TPD, BET, N2 adsorption and desorption. The gaseous products were analyzed by gas chromatograph, and reduced pressure distillation of bio-oil and the upgraded bio-oil were quantified by gas chromatograph-mass spectrometry. It is found that the optimum conditions for the upgrading of bio-oil are 500 ℃ of the reaction temperature and 3.75 h-1 of the WHSV, under which the acid substance in upgraded bio-oil is markedly reduced from 25.6% in reduced pressure distillation of bio-oil to 0.1% after upgrading. Meanwhile, the yield of upgraded bio-oil is 46.8%, and the concentration of CO2 and CO in the gaseous products is 9.5%.
Abstract: The catalytic properties of MgO(111) nanosheet-supported Ni were investigated for the reforming of methane with carbon dioxide with the emphasis on the effect of nickel loadings. The catalytic activity and stability increased with increasing Ni loadings from 2% to 10%, while a further increase in the Ni loading from 10% to 20% led to a negative result. The TEM, XRD, H2-TPD, TG and Raman characterization results show that the deactivation behavior of Ni/MgO(111) depends on the amount of Ni, while the Ni particle size increased with increasing Ni loadings. The deactivation of the sample with 2% of Ni was probably caused by the Ni oxidation, whereas that of the catalyst with higher content of Ni was due to the deposition of carbonaceous materials.
Abstract: A series of K modified Ag-Fe/ZnO-ZrO2 catalysts were prepared by co-precipitation method under different calcination temperatures. The effect of calcination temperature on the catalytic performance for higher alcohols and dimethyl ether(DME) synthesis from CO hydrogenation was investigated. The catalysts were characterized by nitrogen adsorption, XRD, H2-TPR and CO-TPD. The results showed that the catalyst calcined at 250 ℃ could not reach the optimal performance due to insufficient active sites formed at the lower calcination temperature. The catalyst calcined at 300 ℃ exhibited highest CO conversion and higher selectivity of higher alcohols and DME and highest space time yield of higher alcohols and DME reached. As the calcination temperature increased further, the CO conversion decreased, while the selectivity of higher alcohols decreased at first and then increased, the selectivity of DME increased. The catalytic performance of the catalyst was mainly related with its specific surface area, reduction capacity, the dispersion of the σ-AgFeO2 species and CO adsorption-desorption properties. It was proved that the catalyst with larger specific surface area, being easily reduced, higher dispersion of σ-AgFeO2 specie and more CO adsorption active sites, would be helpful for CO hydrogenation conversion. The decrease of the non-dissociative adsorption strength for CO on the surface active sites of the catalyst is favorable for the generation of higher alcohols and DME, while the increase of the dissociative adsorption strength for CO is not favorable for the formation of hydrocarbons.
Abstract: A hybrid catalyst for the direct synthesis of liquefied petroleum gas (LPG) from syngas was prepared through mechanical mixing of methanol synthesis catalyst with dehydration catalyst; its catalytic performance was tested in a single-tube reactor with a simulated biogas at 220~330 ℃, 1.2~5.1 MPa and a space velocity of 500~3 000 h-1. The results indicated that the hybrid catalyst has a good activity; at 325 ℃, 2.1 MPa, and a space velocity of 1 500 h-1, CO conversion and LPG content in the hydrocarbons product are 72.36% and 71.21%, respectively. At 325 ℃ and 2.1 MPa, a stable operation can be realized at a space velocity below 2 500 h-1, whereas the temperature cannot be well controlled at a space velocity over 3 000 h-1, which may lead to the catalyst deactivation. The NH3-TPD, XRD, N2 sorption and TPO characterization results suggest that the deposition of coke and decrease of the mount of strong acid sites and surface area are responsible for the catalyst deactivation.
Abstract: This paper introduces a simple and mild route to prepare Ni2P catalysts. Ni2P/MCM-41 catalysts were successfully prepared using MCM-41 as the support. The catalysts were characterized by H2 temperature program reduction (H2-TPR), X-ray diffraction (XRD), N2-adsorption specific surface area measurements (BET), and X-ray photoelectron spectroscopy (XPS) analysis. The effects of initial Ni/P molar ratio on hydrodesulfurization (HDS) performance of catalysts and catalyst stability were studied with a lab-scale continuous flow type fixed-bed reactor systemusing a feed containing 1% dibenzothiophene (DBT) in decahydronaphthalene. The results indicated that a pure Ni2P phase was obtained when the initial Ni/P molar ratios were 1/2 and 1/3. The catalyst prepared with initial Ni/P mol ratios of 1/2 exhibited the highest activity. At a reaction temperature of 340 ℃, a pressure of 3.0 MPa, a H2/oil volume ratio of 500, and a weight hourly space velocity (WHSV) of 2.0 h-1, the HDS conversion was close to 100%.
Abstract: Development of inexpensive non Pt based high electrocatalytic energy materials is the need of the hour for fuel cell electrode to produce clean alternative green energy from synthesized bio alcohol using biomass. MnO2, electro synthesized at different current density is found to be well performed electrocatalytic material, comparable to Pt, with higher current density, very low overvoltage for the electrochemical oxidation of methanol. From EIS study, the polarization resistance of the coated MnO2 is found to be much low and electrical double layer capacitance is high, the effect increases with increase in current density of electro deposition. XRD, EDX and AAS analysis confirm the MnO2 deposition. The morphology of SEM images exhibits an enhanced 3D effective substrate area, for electro oxidation of the fuel. A few nano structured grains of the deposited MnO2 is also observed at higher current density. The fact supports that a high energetic inexpensive electro catalytic material has been found for fuel cell electrode to synthesis renewable energy from methanol fuel.
Abstract: Cobalt-polypyrrole-carbon black supported Pt catalyst (Pt/Co-PPy-C) was prepared by pulse-microwave assisted chemical reduction and used as a cathode catalyst for oxygen reduction reaction (ORR) in a single cell; the influence of operation temperature and H2/air stoichiometric ratio on the cell performances was investigated, in comparison with the commercial Pt/C catalyst. The results indicated that the cell performs best at 70 ℃ and with a H2/Air ratio of 1.2:2.5. During the 150 h durability test at a galvanostatic operation condition of 600 mA/cm2, the voltage degradation rate with Pt/Co-PPy-C as the cathode catalyst is 0.119 mV/h, about 26% of that with the commercial Pt/C catalyst. The cathode charge transfer impedances before and after durability test are about 7.176 and 8.767 mohm, respectively, much smaller than those with the Pt/C catalyst. The average particle size of Pt in Pt/Co-PPy-C is increased from 2.46 to 3.18 nm, also smaller than that for the Pt/C catalyst. The Pt/Co-PPy-C catalyst exhibits superior performance in ORR and may have an enormous application potential in fuel cell.
Abstract: The Hg0 catalytic oxidation and adsorption capabilities of 3 activated carbons (ACs) and one active coke were evaluated in a simulated coal-derived atmosphere containing hydrogen sulfide (H2S) and oxygen (O2). The examined adsorbent properties that may affect adsorption capacity are pore structure and the presence of sulfur on surface of ACs. N2 isothermal absorption data was treated by BET equation and to calculate the special surface area. The absorption data was settled by HK method to obtain the micro porous structure. The medium pore diameter distribution was calculated by BJH method. The results reveal that with the increasing of micro pore and medium pore volume, Hg0 adsorptive capacity of activated carbons is enhanced. In all cases, Hg0 removal efficiency increases with sulfur addition.
Abstract: In order to improve the mechanical strength and reactivity of CaSO4 oxygen carrier, the addition of glycerinum, silica sol and pseudo-boehmitewere to CaSO4 oxygen carriers was applied by mechanical mixing, and the effect on the mechanical strength and the characteristics of reaction was experimentally investigated. The results show that the addition of glycerinum and silica sol significantly improves the mechanical strength of CaSO4 oxygen carrier, while the pseudo-boehmite has little effect. TGA results indicate that the addition of glycerinum and silica sol can accelerate the reaction rate and decrease the reaction time. The XRD analysis demonstrates that the addition of binders doesn't affect the conversion from CaSO4 to CaS and the conversion is nearly complete.
Abstract: The Ni-Co-P catalysts supported on carbon nanofibers (CNFs) were prepared via electroless deposition; the mass fractions of nickel, cobalt and phosphorus in Ni-Co-P layer are 13.30%, 82.25% and 4.45%, respectively, as determined by ICP-AES. The effects of catalyst amount, sodium borohydride and sodium hydroxide concentrations and reaction temperature on the rate of hydrogen generation in the hydrolysis of alkaline NaBH4 solution were investigated. The results indicated that the rate of hydrogen generation is proportional to the used catalyst amount; a maximum hydrogen generation rate of 18.044 L/(g·min) is achieved at 45 ℃ by hydrolysis of 2.5% NaBH4 solution containing 5% NaOH and 7.5 g/L Ni-Co-P/CNFs catalyst with a Ni-Co-P loading of 18.127%. Moreover, a kinetic study shows that the activation energy for the hydrolysis of alkaline NaBH4 solution under those conditions is 51.57 kJ/mol.
Abstract: Dual mesoporous, micro-mesoporous and mesoporous molecular sieves were prepared and their pore structures were characterized by Ar adsorption and X-ray diffraction (XRD). The calculation methods of pore size distribution for the hierarchical porous molecular sieves were studied, to reveal the relationships among the adsorption-desorption isotherm, pore size distribution, pore shape and pore volume. The results showed that SF and BJH methods are reliable for microporous and mesoporous pores of the hierarchical porous molecular sieves, respectively, whereas NLDFT method is appropriate to calculate the full range pore size distribution. For the synthesis of mesoporous TS-1 zeolite, TPAOH promotes not only the generation of mesopores, but also the secondary crystallization.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
