Abstract: 5 typical pyrrolic-nitrogen compounds were chosen as the investigating objects according to the different pyrrole cycle combination forms with other heterocycles in coal. The Mayer bond orders of these 5 pyrrolic-nitrogen compunds and their intermediate pyrolysis products were calculated. By comparing the Mayer bond orders, the bonds cracking during pyrolysis were deduced, and NH3 and HCN formation mechanisms during pyrrolic-N pyrolysis were analyzed consequently. The results show that the pyrrolic-nitrogen is released in -NH and -NH2 free radicals, which mainly form NH3. The diversity of pyrrole cycles combination forms with other cycles can lead to the variety of nitrogen release processes. To verify the conclusions from calculation, the rapid pyrolysis of pyrrolic-N model compounds pyrrole and carbazole was carried out in a drop style high frequency furnace. The experiment results show that both NH3 and HCN are formed during pyrolysis of pyrrole and carbazole, but NH3 is the main nitrogen containing gaseous product. The conclusions deduced from calculation can get some supports from the experiment results.
Abstract: A comprehensive density functional study was carried out to get an insight into the mechanisms of heterogeneous formation and decomposition of N2O on the char surface by using a char model with zig-zag configuration. The geometry optimizations of reactants, intermediates, transition states and products were made by using density functional theory at the UB3LYP/6-31G(d) level. On the basis of the reaction pathways analysis, the energies of optimized geometries were calculated and corrected with zero point energy; the relative energies and the change of enthalpy were then worked out. Two different reaction pathways are found for N2O formation from reactions between gaseous NO and another pre-adsorbed NO on the surface of char, with the energy barriers of 69.3kJ/mol and 200.0kJ/mol, respectively. N2O may also be released through direct attacking pyridinic nitrogen by NO; the highest energy barrier is 418.0kJ/mol. N2O can be decomposed to N2 on the surface of char; the energy barrier is 100.8kJ/mol. Both the heterogeneous formation and decomposition of N2O are exothermic. Reaction rate constants for rate-determining steps were calculated with transition state theory. The rate of N2O destruction is slightly lower than that of N2O formation on the char surface at low temperature; two rates become close at higher temperature. High temperature is favorable for the heterogeneous decomposition of N2O.
Abstract: In order to study the effect of ambient atmosphere on the coal ash slagging on the surface of corundum liner, the slag samples from the high-temperature slagging experiments were analysed by Scanning Electron Microscopy(SEM), Energy Dispersive Spectrometer (EDS) and X-ray diffraction(XRD), and the slagging samples' properties of morphology and the sintering characteristics between ash compositions and corundum under different atmospheres were studied. The results show that under oxidative atmosphere, the basic substance can promote the cohesive action between coal ash and corundum refractory liner, especially the aluminum rich corundum refractory liner, in which the nucleating and crystaling reactions occur. Under reducing atmosphere, Fe3+ is transformed into Fe2+ in the ash to form eutecticum compounds with low melting temperature, which will increase the bonding degree between molten ash slag and corundom refractory liner, and the segregation and slagging-resistant effect of Fe, Cr, Ti is weakened
Abstract: The changes in hydrogen bond and valence bonds of methanol, ethanol, and propanol with temperature and pressure, the mixed state of methanol/oil, and the reaction process and mechanism of transesterification in sub/supercritical methanol in the temperature range of 15℃~300℃ and pressure range of 0.1MPa～25MPa were studied by using in situ attenuated total reflectance (ATR) infrared spectrum technology. The results showed that hydrogen bonds become weak for methanol, ethanol, and propanol in the temperature range of 15℃~250℃ at a pressure of over 14MPa, especially at the temperature of 75℃~225℃. But temperature almost had no influence on the vibrating peak of their -CH3 bond. When temperature was over 225℃, the vibrating peaks of hydroxyl group of methanol got split, which could not be found for ethanol and propanol. Throughout the whole range of temperature and pressure, the obvious change in infrared spectrum of triolein was not found. At the same time, in situ ATR-FTIR also displayed that methanol and triglycerides were dissolved mutually to form a single phase when the temperature was higher than 185℃ at high pressure of 14MPa. For transesterification between methanol and triglycerides without catalyst at 14MPa, the initiative reaction temperature is about 220℃, which is near subcritical temperature of methanol. Therefore, the transesterification in supercritical methanol occurs in homogeneous state, and the new vibration form of C+…O-…H+, which strengthens the electrophilicity and the nucleophilicity of small molecule alcohols, should be the main reason for accelerating supercritical transesterification.
Abstract: The tar model compound (benzene) reforming to produce hydrogen-rich gas was investigated in a fluidized bed, where the steam acts as the gasification medium. The influences of operating parameters on producing hydrogen-rich gas were fully investigated by changing the reactor temperature, the ratio of steam mass to tars mass(S/T) and the bed height; in addition, the effects of various bed materials(catalysts) on the reforming reaction are also focused on in this paper. The reactor temperature was varied from 780℃ to 900℃, S/T from 3.0 to 6.0, and the bed height from 5.0cm to 20.0cm. The experimental results demonstrate that the optimum operating parameters for producing hydrogen-rich gas are the reactor temperature of 860℃~900℃, S/T of 5.0 and the bed height of 15.0cm~20.0cm. Under the condition of optimum operation, the synthesized alkaline earth metal-based catalyst (20CaAl) displays a better catalysis than natural ores(dolomite and limestone). And the modified catalyst SCaFeNiAl based on 20CaAl exhibits a higher catalytic activity with the activation energy of 58.87kJ/mol and pre-exponential factor of 1.36×107h-1. With SCaFeNiAl, the H2 content of 67.28%, the H2 yield of 303.50(g/kg-tar), the tar conversion ratio of 95.93% and the total gas yield of 5.05(m3/kg-tar) are obtained.
Abstract: Potassium carbonate was supported on hydrotalcite by microwave radiation and used as catalyst to remove acids from crude oil. To better understand the influence of the preparation method on the properties and activity of the catalyst, a series of catalysts with the same K2CO3 content were prepared by impregnation, ultrasonic, microwave radiation and mechanical mixing methods, respectively. Their properties were characterized by XRD, N2 adsorption-desorption and Hammett indicator-benzene carboxylic acid titration. Moreover, their catalytic activity was tested by esterification deacidification reaction between high-acid crude oil and glycol. In addition, the effect of microwave radiation time and the K2CO3 content was also investigated. The presence of carboxyl acid in crude oil and ester in deacidified oil was characterized by FT-IR. It was found that the catalyst with high hydrotalcite crystallinity, well-dispersed K2CO3 and more basic sites shows the best deacidification activity. Among the four methods, microwave radiation can provide adequate energy to disperse K2CO3 species on the surface of hydrotalcite homogeneously and rapidly, and thus can greatly reduce the contacting time of hydrotalcite and basic K2CO3 solution to keep the regular layer structure of hydrotalcite. Furthermore, microwave radiation can produce a high temperature instantaneously, which strengthens the interaction of K+ and hydrotalcite to promote the formation of more basic sites. The catalyst loading 15% K2CO3 and radiated by microwave for 5min showed superior activity, which can increase the deacidification ratio from 89.2% to 97.7% and decrease the acid number of Suizhong high-acid crude oil from 3.72mgKOH/g to 0.08mgKOH/g at 200℃, at a reaction time of 2h and at catalyst and glycol mass ratios to crude oil of 1% and 2%, respectively.
Abstract: Two series of NiMo catalysts supported on alumina with different loadings of molybdenum and nickel were prepared and characterized by X-ray diffraction, N2 sorption, and high-resolution transmission electron microscopy. The performance of NiMo catalysts for hydrodesulfurization was evaluated in a fixed-bed microreactor using dibenzothiophene as a model compound. The effect of morphology of MoS2 phase in NiMo catalyst on its hydrogenation selectivity was investigated. The results indicated that the morphology of MoS2 phases is affected by the loadings of molybdenum and nickel. Mo18Ni4 catalyst (containing 18% MoO3 and 4% NiO), which is provided with the well-known MoS2 slab structures with a multilayered morphology, exhibits high hydrodesulfurization activity and hydrogenation selectivity. The hydrogenation selectivity of NiMo catalyst is linearly correlated with the stacking number of MoS2 slab; the higher the stacking number, the better is the hydrodesulfurization selectivity.
Abstract: Experiments involving hydrogen production from dimethyl ether (DME) were performed with a multistage plasma converter at atmospheric pressure. The results of these experiments show that the DME conversion and H2 yield initially increase and then decrease with the pulse duty ratio increasing. The maximal values of the DME conversion and H2 yield are 87.6% and 39.4% at a pulse duty ratio of 80%, respectively. As the increase in voltage of the electric source, the conversion and H2 yield increase significantly, since both the spark energy and the resident time of a spark in chamber are enhanced. When the heat preservation configuration or humidifying reactant is employed, the DME conversion rate and the H2 yield are enhanced, while the energy consumption is much lower than standard situation at each discharge frequency and the thermal efficiency is enhanced. Owing to insufficient oxygen, the carbon deposit is formed on the electrodes. With the increase in the A/D ratio, the carbon deposit on both the electrodes is clearly reduced.
Abstract: The structures and surface acidities of F-Nb/HZSM-5 catalysts with different F/Nb mol ratio were studied using BET, NH3-TPD, FT-IR, MAS-NMR and SEM. The catalytic performance of these catalysts for ethanol dehydration to ethylene was evaluated and correlated with the characterization results. It is found that, dealumination of HZSM-5 occurred after modification and the depth of dealumination increased with the increase of the amount of F added. The extra-framework aluminum species were observed by 27Al MAS NMR with a signal appeared at -13.5. With the increase of F/Nb mol ratio, both weak and strong acid amounts decreased and a new strong acid site was found in the NH3-TPD profile at 500℃. The catalyst with F/Nb mol ratio of 0.7 gave the highest catalytic activity and selectivity. The stability of the catalyst was greatly improved by the addition of F-Nb.
Abstract: The process of arsenic poisoning for the loading catalyst of V2O5-WO3 /TiO2 was simulated in the experiment. The poisoning characters of the catalyst were studied by means of activity testing, NH3-TPD, H2-TPR and XPS. The results show that after the poisoning of arsenic, the activity of catalyst decreases greatly. Meanwhile, the NH3-TPD, H2-TPR and XPS analyses show that the acidity of catalyst decreases with the poisoning of arsenic. The chemical forms of W and Ti do not change with the interaction of arsenic, but the chemical form of V changes greatly. So the poisoning of the catalyst is attributed to the changing of chemical form of V and the decreasing of acidity of the catalyst.
Abstract: A new type of tubular material, boehmite nanotube, was prepared by adjusting reaction condition with H2O2 in hydrothermal synthesis system. The nanotubes were characterized by XRD, nitrogen absorption and TEM etc. XRD results showed that the AlOOH nanotubes converted to γ-alumina nanotubes upon calcination at 520℃ for 2h. The nanotubes were about 300nm in length with outer diameter of 20nm, as recorded on TEM. BET surface area of the γ-Al2O3 nanotubes was higher than 230m2/g. γ-Al2O3 nanotubes were used as catalyst carriers by impregnating Cu(NO3)2 solution with different Cu content for the titled reaction. The influences of the amount of Cu, different carriers, O2 concentration and SO2 on the selective catalytic reduction of NO were studied. The results indicated that the γ-Al2O3 nanotubes loaded with 7% Cu possessed the highest activity which could reach 90% at 600℃; Further, the catalysts with nanotubes as carrier showed more active catalytic performance at low temperature (bellow 500℃) than those non-nano scale carrier fabricated based on alumina. Oxygen at low concentration (less than 0.25%(φ)) showed little effect on the conversion of NO while it improved the methane conversion when the concentration of O2 was higher than 0.25%; the Cu-nanotubes catalyst also showed sulfur-resistant property.
Abstract: A series of CeO2 promoted Cu-ZnO catalysts with different CeO2 content were prepared by co-precipitation method and characterized by X-ray diffraction, N2 adsorption-desorption (BET), hydrogen temperature-programmed reduction, N2O chemisorption, and H2 chemisorption. Hydrogenation of maleic anhydride to γ-butyrolactone was conducted over these catalysts in a fixed-bed continuous-flow reactor. Addition of CeO2 not only influenced the catalyst structure significantly by decreasing the CuO particle size, increasing the BET surface area, and Cu0 active area, but also had a significant enhancements in both reducibility and H2 uptakes of the catalysts. Promotion of CeO2 resulted in proper structural and good reducibility, which significantly increased the activity and the stability. With 3%~5% of CeO2 , CeO2-promoted Cu-ZnO catalysts showed highest activity and stability for the titled reaction.
Abstract: The reaction of CaCl2 solution with CO2 in ternary amine was studied. In this multiphase reaction, calcium carbonate yield and amine extraction efficiency increased with the increase of CO2 pressure and CaCl2 concentration. The equilibrium of the reaction was analyzed by thermodynamics model coupled with Pitzer electrolytic solution model and a modified Henry’s law CO2 solubility model. The distribution of hydrochloric acid in aqueous and amine is restricted by extraction equilibrium. The concentration of H+ could affect the dissociation of carbonic acid, which determines calcium carbonate precipitation/dissolution equilibrium. The activity coefficients of HCO3- and CO32- decreased with the increase of CaCl2 concentration at constant CO2 pressure condition, and influenced the equilibrium. The calcium carbonate yield and amine extraction efficiency were close to the calculated equilibrium values, and the reaction is controlled by chemical equilibrium.
Abstract: Catalyst coated membrane (CCM) was prepared by direct spraying deposition of the catalyst on the surface of proton exchange membrane, which was then assembled with carbon paper diffusion layers to form a membrane electrode assembly (MEA) for the proton exchange membrane fuel cell (PEMFC). The mixture solution for preparing CCM was composed of 20%(mass ratio) Pt/C catalyst, 5%(mass ratio) Nafion solution, organic solvent and de-ionized water. The surface morphology and pore structure were characterized by the environmental scanning electron microscopy (SEM) and the polarization characteristics of MEA were evaluated by the current-voltage curves of a single PEMFC. The results indicated that the selection of solvent (ethanol, isopropyl alcohol and tert-butyl alcohol) as well as its content and volatility exhibit direct impact on the pore structure of catalyst layers of CCM, which affects the electrochemical performances of MEA. CCM fabricated with isopropyl alcohol solvent and a mass ratio of 4.28 to Nafion solution under 50℃~75℃ exhibits an improved pore structure and I-V characteristic of MEA obtained.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
