Abstract: The pyrolysis of Huolinhe lignite under CO2 atmosphere was carried out in a thermobalance and a fast heating-up fixed bed reactor. The distribution of gases, char yield and its property such as element, surface structure, FT-IR spectra were analyzed. By this, the effect of CO2 on the pyrolysis behaviors was studied. The results show that CO2 gasification of the nascent char, which destroys the hydrogen-containing char structure, not only promotes cracking of benzene ring and fracture of hydroxyl, methyl and methylene groups etc., but also weakens the interaction between H and char matrix and increases the H fluidity, leading to the increase in the generation of H radicals. These H radicals can combine with other free radical fragments generated from fracture of the coal macromolecules to produce more volatiles. This will produce the char with a high specific surface and high pore volume and porosity. The introduction of CO2 promotes the coal pyrolysis and generation of volatile, resulting in decrease in char yield and increase in the evolution amount of H2, CO, CH4 and other small molecules hydrocarbons.
Abstract: The transformation of potassium during pyrolysis and gasification was studied in a fixed bed. The effects of potassium based catalyst on the steam gasification reactivity and the transformation of potassium were investigated by TG-DSC. Results show that all the potassium carbonate loaded by either impregnation or mechanical mixing has a marked catalytic effectiveness. The reactivity of Shenfu char increases with potassium loadings up to a saturation loading of about 10%. The catalytic effect has a maximum value. The transformation of potassium and the amount of potassium intermediate have been confirmed during pyrolysis and gasification. And the reactivity of chars depends on the amount of potassium intermediate. Potassium carbonate has an obvious catalytic effect, and potassium chloride has a poor catalytic effect. However, the catalytic effect of potassium sulfate increases obviously with the increasing of temperature in the range of 700～800℃.
Abstract: MOx/USY catalysts (M=Co,Mo,Co-Mo) were prepared by incipient wetness impregnation method. Catalytic pyrolysis of Huang Tu Miao (HTM) coal was investigated and the pyrolysis products were examined by TG-FTIR technique. TG results indicate that MOx/USY catalysts are effective in lowering degasifiction temperature (14, 23 and 9℃ respectively) in HTM coal pyrolysis. Kinetic calculations show that MOx/USY catalysts are effective in lowing activation energy of pyrolysis. FT-IR analyses show that the MOx/USY catalysts are effective in manipulating coal pyrolysis products. CoOx/USY catalyst promote the generation of CH4, CO and aromatic hydrocarbons and aliphatic hydrocarbons in HTM coal pyrolysis. MoOx/USY catalyst show little effect in manipulating pyrolysis products. CoOx-MoOx/USY catalyst is a promising catalyst in giving high yield of volatile products, however the pyrolysis temperature moved to high temperature region. These results indicate that different metal oxides incorporated zeolite USY have different impact on manipulating pyrolysis products.
Abstract: Polystyrene spheres were prepared by soap free emulsion polymerization method,then three dimensional ordered macroporous (3DOM) oxides Fe2O3 were successfully prepared after impregnation and calcination using nitrates as raw materials and citric acid as complexing agent. The samples were characterized by the techniques of scanning electron microscopy (SEM), X-ray diffraction(XRD), BET and mercury porosimetry. Pyrolysis and gasification of biomass with Fe2O3 as oxygen carriers in helium atmosphere were carried out in a thermogravimetric analyzer coupled with mass spectrometry (TG-MS). The possibility of 3DOM Fe2O3 functioning as gasification agent in biomass gasification substituted for pure oxygen, oxygen-enriched air or steam were investigated. Furthermore, a comparison experiment was carried out by using analytically pure Fe2O3 to analysis the high-performance of 3DOM Fe2O3. The characterization results showed that 3DOM Fe2O3 presented a three-dimensional ordered macroporous morphology, its tiers were arranged alternatively and connected through three-dimensional pore structures. By contrast with the XRD pattern of analytically pure Fe2O3. TG-MS results showed that Fe2O3 contributed to biomass gasification in high temperature stage. When used 3DOM Fe2O3 as oxygen carrier, the maximum weight loss and maximum weight loss rate raised 7.1% and 0.29%/min in the gasification stage, respectively, meanwhile two generation peaks of CO, CO2, and CH4 appeared in the MS curves.
Abstract: In order to understand the pyrolysis mechanism of hemicellulose and to identify the formation pathways of key products during pyrolysis, the pyrolysis processes of O-acetyl-xylopyranose are investigated by using density functional theory methods at B3LYP/6-31G++(d,p) level. In the pyrolysis, O-acetyl-xylopyranose firstly decomposes to form acetic acid and IM1 with an energy barrier of 269.4 kJ/mol, and then IM1 is converted to acyclic carbonyl isomer IM2 with a low energy barrier of 181.8 kJ/mol. IM2 further decomposes to form all sorts of small molecules through four possible pyrolytic reaction pathways. The equilibrium geometries of the reactants, transition states, intermediate and products were fully optimized, and the standard thermodynamic and kinetic parameters of every reaction pathway were calculated. The calculation results show that reaction pathways (2) and (4) are the major reaction channels in pyrolysis of O-acetyl-xylopyranose and the major products are low molecular products such as acetic acid, acetaldehyde, glycolaldehyde, acetone, CO, CO2 and CH4, which is according with related analysis of experimental results.
Abstract: The tar and char from a fluidized bed Chinese herb residue (CHR) pyrolysis were cracked and gasified in a fixed char bed. The change in chemical species of tar before and after passing through a fixed char bed was analyzed. The results show that increasing the residence time of tar and pyrolysis gas in the char bed from 0 s to 0.95 s causes a significant decrease in the chemical species containing -OH, C-H, C-O, C=O and C=C groups, but leads to an obvious increase in the aromatic species. Introducing steam into the char bed results in the formation of more species containing aromatic rings, C-O and -OH groups, while adding the oxygen to the atmosphere increases the amount of aromatic components but has little effect on the amount of species containing -OH, C-H, C=O, C=C and C-O. Both steam and oxygen are effective to remove tar from the gasification gas, but the effect of steam is relatively weaker. Introducing steam together with oxygen will have a rather higher tar removal efficiency, and the tar in the producer gas can be ignored.
Abstract: The influences of potassium salts on the decomposition of formaldehyde in supercritical water were investigated in a continuous reactor under 400～650℃, 23～29 MPa and a residence time of 4～12 s, as formaldehyde is one of the most important intermediate products for the gasification of biomass with supercritical water. The results showed that KHCO3, K2CO3, KCl and mixed potassium salts are able to reduce the fraction CO in the gaseous product and increase the fraction of CO2, which then depresses the heating value of the gaseous product. All these potassium ingredients exhibit an inhibitive effect on the formation of H2, CO and CO2 and the gasification efficiency; the inhibition strength of various potassium ingredients follows the order of mixed potassium salts > KHCO3 > K2CO3 > KCl. The inhibitive effect on the formation of gaseous products is enhanced under high reaction temperature and long residence time, but is almost independent on the reaction pressure. Under high temperature, high pressure and long residence time, gas generation may be inhibited considerably by the mixed potassium salts, possibly due to a synergetic effect of different potassium salts.
Abstract: The changes of the content and structure of four fractions in the vacuum residue of Saudi Arabia light crude oil (ALVR) pre- and post hydrotreating were investigated in an autoclave at different reaction temperatures. The results showed that after the hydrotreating, the saturate content is increased greatly, while the aromatic and resin contents are decreased in the hydrotreated residue; the contents of four fractions changes regularly with the increase of the reaction temperature. The H/C mol ratio and molecular weight of four fractions in the hydrotreated residue are decreased while the fraction of aromatic carbons (fa) is increased after the hydrotreating. With the increase of reaction temperature, the H/C mol ratio, molecular weight and the fraction of paraffin carbons (fp) of four fractions are decreased, while fa and the content of resin and asphaltene are increased in the hydrotreated residue; meanwhile, the total rings and aromatic rings of resin and asphaltene are decreased. The four fractions in the residue have undergone hydrogenolysis and hydrodealkylation during the hydrotreating. Bridge bonds between the units of resin and asphaltene may break by hydrotreating, leading a decrease of the unit number of resin and asphaltene, which is more prominent at higher reaction temperature.
Abstract: In-situ DRIFTS and chemical trapping techniques were employed to investigate the adsorbed species over the surface of precipitated iron-based catalysts and the mechanism of oxygenates formation in high temperature Fischer-Tropsch synthesis. The results showed that both linear and bridged CO molecules are present on the catalyst surface, which leads the formation of numerous oxygenated precursors. Some crucial surface intermediates are detected by the in-situ DRIFTS, such as acetate, acetyl and methoxide. The surface of precipitated iron-based catalysts is characterized by following facts: (ⅰ) alcohols are able to react with free surface hydroxyls to form alkoxy species; (ⅱ) surface adsorbed molecules exhibit certain oxidizing ability; (ⅲ) basic sites such as OH- and lattice oxygen may react with CH3OH or CH3CHO molecules. By chemical trapping of the CH3OH + CO and CH3I + CO + H2 reactions, it was found that acetyl is an important intermediate for oxygenates and the hydrogenation of acetyl is a crucial step for the formation of oxygenates. On the basis of these observations, the mechanism of oxygenates formation in high temperature Fischer-Tropsch synthesis over the precipitated iron-based catalysts was then proposed.
Abstract: A series of Pd/Cd0.8Zn0.2S/SiO2 photocatalysts were prepared by incipient wet impregnation. The catalysts were characterized by XRD, H2-TPR, XPS, and UV-vis DRS and used in the photocatalytic evolution of H2 from glycerol and water mixture; the effects of Pd loading on the surface structure, photo absorption and H2 evolution rate were investigated. The results showed that the chemical interaction between ZnS and CdS results in the formation of Cd0.8Zn0.2S solid solution on the surface of SiO2; after the modification with Pd, the light absorption region of Cd0.8Zn0.2S/SiO2 is expanded and the photo absorption efficiency is enhanced obviously. The loading of Pd exhibits significant influence on the rate of photocatalytic H2 evolution; over 0.5%Pd/Cd0.8Zn0.2S/SiO2 with a Pd loading of 0.5%, the maximum hydrogen production rates under UV light irradiation and under solar-simulated light irradiation reach 831 μmol·h-1 and 153 μmol·h-1, respectively, which are almost 4 times and 2 times higher than those obtained over unmodified Cd0.8Zn0.2S/SiO2 under UV and solar-simulated light irradiation, respectively. The superior photocatalytic performance of Pd/Cd0.8Zn0.2S/SiO2 can be partly related with the improvement of photo absorption, the enhancement in chemisorption and activation of H2O and the increase in separation efficiency of photo induced electron-hole arising from the Pd modification.
Abstract: To reduce the energy consumption of CO2 reforming of CH4, the synergies of thermal plasma and catalysts in the reforming process was studied in three elaborate modes: plasma only, combination of plasma and catalysts (CPC), and CPC with part of feed gases introduced into plasma discharge region. The optimal specific energy of 193 kJ/mol and energy conversion efficiency of 66.4% were achieved under the conditions of CH4/CO2 of 4/6, input power at 14.4 kW, feed gases of 5 m3/h in mode 3, when the conversions of CH4 and CO2 were 77.00% and 62.40%, and the selectivities of H2 and CO were 88.60% and 96.70%, respectively. These results were closed to that of CH4-H2O(g) reforming process. The excellent performance of the present process benefits from three different reaction courses: discharge reaction, thermochemical reaction and catalytic reaction.
Abstract: Thermal decomposition of nickel hypophosphite precursor into nickel phosphide (Ni2P) was studied using thermogravimetry-mass spectrometry analysis. The results indicated that nickel ion (Ni2+) influenced the decomposition pathway of hypophosphite, because it might catalyze the reaction of hypophosphite to produce PH3 at lower temperature. Silica-supported Ni2P catalysts with different loadings were prepared and characterized using X-ray diffraction, N2 adsorption-desorption, and high resolution transmission electron microscopy. It was indicated that Ni2P was well dispersed on the support with a particle size of 5～8 nm. The catalytic performance of as-prepared catalysts was evaluated in a fixed-bed reactor for hydrodenitrogenation of quinoline. Under the reaction temperature of 360℃, hydrogen pressure of 2.0 MPa, LHSV of 2.0 h-1, and H2/oil volume ratio of 500:1, the conversion of quinoline over Ni2P(20%)/SiO2 catalyst reached 41.5%.
Abstract: Cu(I)Y, NiY and CeY zeolites were prepared by liquid phase ion exchange and characterized by means of XRD, ICP/MS and N2 physisorption. Properties of selective adsorptive desulfurization of FCC gasoline on the adsorbents have been investigated by fixed-bed adsorption experiment and GC-SCD technique, especially the removal selectivity of the sulfur compounds in the oils. The results indicated that the removal selectivities of the sulfur compounds in the gasoline were quite discrepant for different adsorbents, among which, CeY had the sequence of 2-ethyl-5-methylthiophene3 mercaptan2-thiophene<2 or 3-methylthiophene3 mercaptan<2-ethyl-5-methylthiophene2-thiophene<2 or 3-methylthiophene
Abstract: Exhaust emissions from a vehicle diesel engine with different property fuels were studied, and the emissions include exhaust smoke, particulate matter (PM), nitrogen oxide (NOx), unburned hydrocarbon (HC), carbon monoxide (CO) and sulfur dioxide (SO2). Engine bench test and simulated New European Driving Cycle (NEDC) test cycle were operated on the engine with five kinds of fuel, and the fuels have different sulfur content, aromatic content and cetane number. The results show that exhaust smoke, HC, CO and SO2 emissions decrease with fuel sulfur content decreasing, and the PM emission under the simulated NEDC test cycle decreases remarkably, while NOx emissions was not affected obviously. With fuel aromatic content decreasing, emissions including exhaust smoke, PM, NOx, HC and CO descend distinctly. With cetane number ascending, the exhaust smoke, PM and HC emissions decline evidently, while NOx and CO emissions have very small changes.
Abstract: Pulverized coals were burned in a tube furnace under O2/CO2 atmosphere, and an electrical low pressure-impactor (ELPI) was used to collect the PM2.5. The results show that a bimodal distribution of PM2.5 appears, which is located at 0.1 μm and 2.0 μm, respectively. The mass concentrations of PM2.5 increase with5 enhancing the O2 concentraion. The enrichment of S, Na and K on the sub-micron particles is observed, but that of Si and Ca is not observed. It is proposed that sub-micron particles are formed via the mechanism of vaporization and condensation, and the super-micron particles are formed by the fragmentation of coal char and the coalescence of inherent mineral matter based on the analyses of particle size distribution, elements distribution and morphology of PM2.5.
Abstract: A series of iron-cerium mixed oxide catalysts modified titanium, zirconium, tungsten and molybdenum were prepared by co-precipitation. The selective catalytic reduction of NOx with NH3(NH3-SCR) activity of the catalysts were carried out in a fixed-bed quartz tube reactor. The research results indicated that the addition of tungsten and molybdenum could increase the high-temperature NH3-SCR activity of the iron-cerium mixed oxide catalysts, but decreased its low-temperature NH3-SCR activity. Titanium could improve the NH3-SCR activity of the iron-cerium mixed oxide catalyst within the range of reaction temperature, especially at low-temperature. Titanium was the most suitable assistant. When increasing the molar fraction of titanium from 0.10 to 0.40, the low-temperature NH3-SCR activity of iron-cerium-titanium mixed oxide catalysts firstly increased and then decreased while the high-temperature activity gradually increased to 100%, and the optimum molar fraction of titanium was 0.15. The results of X-ray diffraction(XRD) and N2 adsorption isotherms showed that the addition of titanium could optimize the pore structure of iron-cerium mixed oxide catalyst, and increased the BET surface and the pore volume of the iron-cerium mixed oxide catalyst, meanwhile refined its pore size. At the some cases, titanium could react with iron oxide and cerium oxide within the iron-cerium mixed oxide catalyst to form the solid solution. Therefore, the addition of titanium could enhance the NH3-SCR activity of iron-cerium mixed oxide catalyst. Under the condition of the test, more than 90% of NOx conversion could be achieved over Fe0.8Ce0.05Ti0.15Oz catalyst at the temperature range of 150～400℃.
Abstract: The effects of SO2 on the cyclic calcination and carbonation characteristics and the cycling stability of calcium-based CaCO3 sorbent for CO2 capture were investigated in a cycling calcination/carbonation system. The results indicated that the capacity of CaCO3 sorbent for CO2 capture decreases with the increase of the number of calcination/carbonation cycling and the addition of SO2 will further reduce the capacity for CO2 capture; moreover, the decrease of the capacity for CO2 capture may be aggravated at higher SO2 concentration. After 10th cycling, the carbonation conversions of the sorbent under SO2 concentration of 0, 0.1% and 0.2% are 25.5%, 16.9% and 5.2%, respectively. SEM characterization results revealed that sulfate products are formed on the surface of CaCO3 particles in the presence of SO2; the sulfate products block the sorbent holes and then reduce the diffusion rate of CO2 into the sorbent, which may then reduce the capacity of the calcium-based sorbent for CO2 capture.
Abstract: The dry methane with different concentration was used to research the dry methane reactions at Ni-YSZ anode in solid oxide fuel cell (SOFC). The anode exhaust gases were measured by on-line chromatography. The reactions of dry methane with different concentration at SOFC Ni-YSZ anodes were analyzed by summarizing the anode exhaust gases regular pattern for different reactions. The mathematical relationships between dry methane concentration and current for different anode reaction were studied. As the oxygen ion concentration at the anode three-phase boundary increasing continuously, the following reactions with low concentration methane occurs in sequence of CH4+O2- → CO+2H2+2e-, CH4+2O2- → CO+H2O+H2+e-, CH4+3O2- → CO+2H2O+6e- and CH4+4O2- → CO2+2H2O+8e-. The first two or three reactions occurred with medium methane concentration, while the first reaction occurred only with high methane concentration. The judgment for methane in low, medium or high concentrations were qv(CH4)≤I/(4F)、I/(4F)≤qv(CH4)≤I/(2F)、qv(CH4)≥I/(2F) which are based on Faraday's first law and the relationship among the reactant species.
Abstract: Comparisons of accuracies of adsorption models in predicting adsorption data of supercritical methane on activated carbon were carried out for practical application of adsorption of natural gas (ANG). Ajax activated carbon was selected as an adsorbent, six isotherms of excess adsorption amount of methane were measured at temperature from 268.15 K to 338.15 K and pressure up to 12.5 MPa. Parameters of Langmuir, Langmuir-Freundlich and Toth equations were firstly set by the linear fit of adsorption data, absolute amounts and densities of the adsorbed phase of supercritical methane were then determined by the modified models. Isosteric heats of methane adsorption on Ajax activated carbon were determined by adsorption isosteres on the absolute amounts. Comparisons were made between experimental data and those predicted by models. Results showed that the adsorbed phase densities of supercritical methane on the activated carbon varied with equilibrium temperatures and pressures, the mean value of isosteric heat of adsorption set by absolute amounts was 15.72 kJ/mol, which was smaller than that plotted from the excess amounts. The relative errors between the experimental data and those predicted by Langmuir, Langmuir-Freundlich and Toth equations varied with the pressure, The accumulated relative errors were respectively 6.449 8%, 7.918 4% and 0.910 0% at lower pressure range from 0 to 0.025 MPa, but will respectively be 0.491 1%, 0.161 3% and 0.369 4% while pressure was in range of 1～10 MPa. Toth equation performed well in predicting the equilibrium data in the whole pressure range, but the results from Langmuir-Freundlich equation had higher prediction accuracies while the pressure got higher.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
