Abstract: The microscopic characteristics of solid particles have important influence on the formation of fluid slag, coarse slag and fine slag during entrained-flow gasification process. Based on the bench-scale opposed multi-burner (OMB) gasifier, solid particles were sampled at different axial distances along the gasifier chamber under typical operating conditions (oxygen and carbon atomic ratio at 1.0). The microscopic characteristics of solid particles were studied by using N2 adsorption-desorption and scanning electron microscopy (SEM) methods. The results show that the solid particles are comprised mainly of porous irregular particle and spherical particle, and few solid particles generated at burner plane perform as dense irregular and hollow shape. As the gasification reaction proceeds along the axis of gasifier, the surface structure of particles becomes rougher, and the pore structure increases. The isotherms of particle samples are all type Ⅱ, and the particle samples consist of continuous and complete system of pores. The hysteresis loops are H3-type, and there are a large amount of fractured pores. BET surface area and pore volume increase with increasing distance from the burner plane, and average pore diameter gradually reduces, and larger changes occur in the vicinity of the burner plane. The mesopores less than 10 nm vary apparently and increase with increasing distances from the burner plane, while the pores larger than 10 nm are almost unchanged.
Abstract: The gasification characteristics of Huolinhe lignite char (HLH char), SM bituminous coal char (SM char) and Jincheng anthracite char (JC char) with the mixtures of steam and H2 at elevated pressures were investigated in a pressurized fixed bed differential (PFBD) reactor. The results show that the inhibition of H2 on the coal-char gasification with steam is remarkable, and the intensity of the inhibition increases with increasing H2 partial pressure, total pressure and coal rank, respectively; while it decreases with increasing temperature. Coal-char gasification with steam or steam/H2 can be described by the same kinetic model, and the final carbon conversion of coal-char gasification with steam/H2 is lower than that with steam. The inhibition mechanism is related to the H2 partial pressure. When H2 partial pressure is low, H atom dissociated from H2 molecule occupies the active point on the coal-char surface directly; while when the H2 partial pressure is high, the irreversible reaction of oxygen-exchange reaction is strengthened.
Abstract: The specific heat capacities of chars during primary pyrolysis of biomass with different conversion and the heat capacities of virgin biomass were determined. The ratio method was employed to measure the specific heat capacities of two biomass samples and their pyrolyzed chars through thermogravimetry and differential scanning calorimetry (TG-DSC). A mathematical model was developed to calculate values of specific heat of chars. The results show that the specific heat capacities of the two biomass samples and their derived chars increase linearly within 60~200℃. The values of the specific heat capacity of the chars are lower than those of the virgin biomass samples. The specific heat of chars decreases as the extent of pyrolysis increases. The calculated specific heat capacities from the developed mathematical model are quite close to those measured by TG-DSC analyses between 150~200℃.
Abstract: The catalytic performance of coal char loaded with potassium carbonate on the CO methanation reaction was investigated in a pressurized fixed bed reactor. The results show that the catalytic activities of raw coal pyrolysis char and demineralized coal pyrolysis char are very low, while with loading 10% potassium carbonate, the catalytic activity of chars increases obviously and the yield of methane reaches to 30%. The gasification rate changes with the progress of carbon conversion and has a maximum value at a carbon conversion around 22%. The analysis by FT-IR indicates that the interaction of potassium carbonate with coal can form C-O-K complexes during pyrolysis at 700℃, with an infrared band around 1 100 cm-1. The intensity of this band is found to be proportional to the steam gasification rate of the carbon. After reaction in CO-H2 mixture gas at 700℃ for 180 min, the intensity of C-O-K vibration increases more or less.
Abstract: The release behavior of sulfur, chlorine and fluorine during pressurized oxy-fuel combustion was investigated by a pressurized thermogravimetric analyzer (PTGA) combined with Fourier transform infrared (FT-IR) spectroscopy, in which the influence of pressure on the release characteristics was mainly focused on. The results show that the changes in pressure have a remarkable effect on the migration and transformation of sulfur, chlorine and fluorine. The conversion of pyrite to COS increases with the rise in pressure, which leads to an increase in SO2 yield, but at 3 MPa, the SO2 yield drops somewhat. Besides, the increase of CO partial pressure at higher pressure promotes the COS generation, leading to an increase in COS yield. Because the release of chlorine is close related to the volatile yield, the increase of volatile yield at higher pressure makes more organic chlorine release and conversion to HCl. Moreover, the enhanced burning rate and combustion temperature by volatiles at higher pressure accelerate the mineral fluorine resolving, and more HF is formed. Also, the hydrolytic reactions are strengthened at higher pressure, which results in an increase of HF yield.
Abstract: A Ca-based compound oxygen carrier was prepared with industrial grade natural anhydrite, bentonite (ben) and iron nitrates by using the mechanical mixing-prilling method. The experiments were carried out in a fluidized bed with steam as the gasification-fluidization medium. The influence of active component content, temperature as well as multi-cycle on the reactivity between CaSO4/bentonite and coal was investigated. The results show that the CaSO4 mass content of 60% and the adding Fe2O3 can make a better reactivity and less attrition of the oxygen carrier particles. The attrition rate is 0.089%/h. The time to reach a carbon conversion of 95% is shortened to 20.8 min, and the average dry concentration of CO2 approaches 95.99%. Ten redox tests demonstrate that the concentration of CO2 can be kept in 80% and the CaSO4-Fe2O3/ben (Ca-Fe/ben) oxygen carrier has a good cyclic stability. Moreover, four types of coal are tested, indicating that the coals with high volatile content and high ash content have higher combustion efficiencies with above 90% CO2 concentration in gasification products in all cases.
Abstract: The ash fusion characteristics of coal mixed with different kinds of sludge were investigated. Mineral ternary phase diagram and XRD analysis were used to identify interaction mechanism of different mineral components and transformation of ash melting characteristics during burning of coal with municipal and industrial sludge. The results show that ternary phase diagram can effectively predict the variation of ash melting temperature for co-combustion of coal and sludge. When the content of iron oxide is low, the formation of eutectic, diopside and anorthite can reduce the ash fusion temperature. Monticellite, mullite and monomer form of iron oxide improve the ash fusion temperature. The sulfur in municipal sludge easily forms low temperature eutectic of sulfate. The influence of phosphorus on the ash fusion temperature is related to the ratio of alumina and alkali. When the alumina is dominant, phosphorus will reduce the ash fusion temperature. When the alkali is primary, phosphorus will raise the ash fusion temperature.
Abstract: The online catalytic cracking of bio-oil over HZSM-5 was investigated. The HZSM-5 catalyst samples used for different reaction times were analyzed in terms of physicochemical properties and chemical compositions to investigate the effects of bio-oil catalytic online cracking. Simultaneously, the used HZSM-5 catalysts were analyzed by TG, BET, XRD, SEM and TEM to explore the mechanism of HZSM-5 catalyst deactivation. The regeneration of the deactivated catalyst was also studied. It was found that acids, aldehydes and ketones as the undesirable organics contained in the bio-oil were reduced by deoxidization over HZSM-5 and more desirable organics like phenols and aromatic hydrocarbons could be produced. Meanwhile, the activity of the catalyst declined after 80 min reaction, leading to the worse quality of the refined bio-oil. The coke deposited was mainly fibrous carbon with a little graphite carbon, where the total amount of the coke was 14.12%. The graphite coke deposited inside the pore of the catalyst and the fibrous coke deposited outside the surface of the catalyst were contributed to the deactivation of the catalyst. The basic structure of the catalyst remained unchanged, but the specific area and pore volume of the catalyst were decreased simultaneously and the agglomeration of grain was increased, leading to the decrease of crystallinity. The change of some crystal structure of the catalyst resulted in the deactivation of catalyst. After the regeneration, the catalytic activity could be recoveried.
Abstract: Three kinds of CuFe2O4 catalysts were synthesized by co-precipitation method using potassium hydroxide (A), sodium carbonate (B) and sodium bicarbonate (C) as the precipitants. Their catalytic activity and thermal stability were evaluated in water-gas shift reaction (WGSR). The microstructure and surface property of as-prepared catalysts was investigated by X-ray diffraction (XRD), N2-physisorption, H2-temperature programmed reduction (H2-TPR), CO2-temperature programmed desorption (CO2-TPD) and cyclic voltammetry (CV). The results show that the catalyst prepared with potassium hydroxide as precipitant exhibits excellent WGSR activity. Potassium hydroxide plays an important role in promoting the generation of CuFe2O4, restraining growth of crystalline CuO and CuFe2O4, resulting in much better dispersion of CuO on the surface of catalysts, enhancing the reducibility of catalysts, and increasing the amount of weak basic sites. These factors remarkably improve the activity and thermal stability of catalysts.
Abstract: Mn-Ce/TiO2 (M) and Cu-Ce/TiO2 (C) were prepared by sol-gel method, and the cordierite honeycomb ceramics (CC) was coated with M and/or C and V2O5-WO3 in sequence by impregnation method. A series of monolith catalysts were evaluated for the selective catalytic reduction (SCR) of NOx by urea. The physical and chemical properties of the catalysts were well examined using nitrogen adsorption, CO2-TPD, NH3-TPD, XRD, XPS and H2-TPR experiments. The results showed that when the M phase was coated onto catalyst prior to C phase, the complex catalyst V/3C/3M/CC was more active than the catalysts with only M or C phase in the presence of 0.01% SO2 and 10% H2O, and a small quantity of SO2 may favor the urea-SCR activity. XRD analysis indicated that Cu, Ce modified TiO2 sol favors the formation of anatase phase, and Mn, Ce modified TiO2 sol facilitates the formation of rutile phase. The BET surface area of catalyst only has relationship with the amount of M or C phase, and loading sequence does not influence it so much. The introduction of M phase and C phase increases the surface acid sites of different intensity. H2-TPR results showed the interaction between vanadium and copper and/or manganese species enhances the reduction of vanadium, which can increase the amount of H2 consumption. XPS results indicated that both high V4+/V5+ ratio and large amount of surface chemisorbed oxygen may beneficial to the activity of the catalysts.
Abstract: Cu/Al-PILC, Fe/Al-PILC and CuFe/Al-PILC were prepared by rotary evaporation-impregnation method using Al-PILC as support. Selected catalytic reduction of NO with NH3 (NH3-SCR) was carried out in a fixed bed reactor to evaluate their catalytic performance. Compared to Cu/Al-PILC and Fe/Al-PILC, CuFe/Al-PILC showed better NO removal efficiency (97%) and a wider temperature range (290~450℃) of 90% DeNO because of the strong synergetic effect of Cu-Fe composite oxides. Moreover, CuFe/Al-PILC showed good resistance to water vapor and SO2. XRD, UV-vis, XPS and N2 adsorption were used to characterize the structure of the catalysts. A new phase CuFe2O4 formed in CuFe/Al-PILC, which changed the surface properties of CuFe/Al-PILC, improved the dispersion of Cu and Fe on the Al-PILC surface and increased ABET and vp of CuFe/Al-PILC. H2-TPR confirmed the existence of CuFe2O4, which improved the re-dox property of CuFe/Al-PILC. The result of NH3-TPD implied that the surface acidity of CuFe/Al-PILC made it possible to adsorb and desorb NH3 in a wide temperature range. The concentration of reducible species on the surface of CuFe/Al-PILC increased, which resulted in high NO removal efficiency.
Abstract: A monolithic CeO2/TiO2/cordierite deNOx catalyst was prepared by an impregnation method, with cordierite as the substrate and CeO2 as the active component. The CeO2/TiO2/cordierite catalyst exhibits excellent resistance against SO2 and H2O in the selective catalytic reduction (SCR) of NOx with NH3, compared with the commercial vanadium-based catalyst (V2O5-WO3/TiO2/cordierite); the CeO2/TiO2/cordierite catalyst gives a conversion of NOx above 70% after 30 h resistance test against SO2+H2O, only declined by 5%. BET, XRD, FT-IR and TG results indicated that ammonium sulfate is formed on the surface of both CeO2/TiO2/cordierite and V2O5-WO3/TiO2/cordierite catalysts during the SCR reaction in the presence of SO2 and H2O, but on the former, the amount of ammonium sulfate deposited is much less. NH3-DRIFT results suggested that the surface Brønsted acidity is strengthened, whereas the surface Lewis acidity is weakened during the SCR reaction in the presence of SO2 and H2O. XPS results further displayed that SO2+H2O in flue gas may induce a reduction of Ce from Ce4+ to Ce3+ on CeO2/TiO2/cordierite catalyst, resulting in an increase of the chemisorbed oxygen amount, which contributes to the excellent resistance of the CeO2/TiO2/cordierite catalyst against SO2 and H2O during the SCR reaction.
Abstract: Five zeolites ZSM-5, ZSM-22, EU-1, MCM-22, and ITQ-13 with 10 member ring channels were hydrothermally synthesized and their structure, acidity, morphology and catalytic behaviors in methanol aromatization reaction were compared. The results indicate that the morphology, microporous volumes, and physicochemical properties of the zeolites differ significantly from each other, and thus results in considerable influence on the catalytic activity and stability. Among the five zeolites studied, ZSM-5 shows the highest aromatic yield of 34.8%, followed by MCM-22 with the aromatic yield of 21.9%. However, unlike ZSM-5 and MCM-22, the other three catalysts are inactivitive for methanol aromatization. The introduction of Ga species into ZSM-5 and MCM-22, however, can improve the aromatic yield significantly. The aromatic yields on Ga/ZSM-5 and Ga/MCM-22 reach 40.8% and 27.1%, respectively. The TG/DTA and GC analyses of the coke compounds deposited on the deactivated catalysts suggest that the five zeolites display much differences in composition, location and distribution of coke deposition.
Abstract: ZSM-5 zeolites were treated by alkali Na2CO3 solution; the effect of treatment temperature and time on the structural feature and physical and chemical properties of ZSM-5 zeolites were investigated. The ZSM-5 samples before and after alkali treatment were characterized by XRD, N2 sorption, XRF, SEM and NH3-TPD. With n-butyl mercaptan and isoprene as the model compounds for thioetherfication, the activity of Ni-Mo/HZSM-5 prepared from alkali treated HZSM-5 zeolites with micro- and meso-porous structure were evaluated. The results show that the original zeolite frame structure is reserved after Na2CO3 solution treatment; moreover, the performance of the Ni-Mo/HZSM-5 catalyst in thioetherfications is improved and the modification process was gentle and controllable. An appropriate increase of the treatment temperature and treatment time was beneficial to the increase of surface area, meso-pore volume and average pore size, as well as the regulation of the acid properties without affecting the microporous structure. However, excessive long treatment time was disadvantageous to the formation of mesopores and the modulation of acidity. The Ni-Mo/HZSM-5 catalyst from ZSM-5 treated with Na2CO3 solution at 90℃ for 5 h exhibits high thioetherfication performance; the conversions of n-butyl mercaptan and isoprene reach 92.36% and 97.33%, respectively.
Abstract: In this study, a portable direct-flame solid oxide fuel cell (DF-SOFC) stack has been demonstrated using the conventional butane gas as fuel. The stack is constructed by bundles of the 3 single cells in a series with conventional Ni/YSZ anode. The fuel cell structure and performance are characterized by scanning electron microscopy (SEM) and electrochemical workstation, respectively. The results show that the stack presents an open circuit voltage (OCV) of about 2.1 V and an output power of 0.24 W, which powers an USB fan in 4 h. The cell voltage is quite stable for 4 h, moreover, no carbon deposition is found in the anode layer. This indicates that the DF-SOFC stack can be used for portable applications.
Abstract: An experimental investigation of methane combustion on copper-based catalyst was carried out in a micro-fixed bed reactor under atmospheric pressure at 450~500℃ with inlet methane volume fraction between 10% and 35%. The influence of methane partial pressure on reaction rate is found to be significant, while that of oxygen is neglectable. Parameters of the kinetic model were estimated using the least squares method. The resulted kinetic model of methane catalytic combustion is -rCH4=1.61×107×e-108 000/RT×pCH40.5. Predicted and experimental values of methane conversion agree well with each other, which shows the reliability and accuracy of the model. The above reaction can be described as a two-step reaction according to the experimental result. Oxygen reacts quickly with the active vacancy sites of the catalyst to form adsorbed oxygen molecules which reacts with methane molecule to form carbon dioxide and water.
Abstract: Pd/La0.8Ce0.2MnO3/ZSM-5 catalysts were prepared by incipient wetness impregnation and characterized by nitrogen physical adsorption, X-ray diffraction (XRD), scanning electron microscope (SEM), and temperature-programmed reduction (H2-TPR). The catalytic combustion of toluene as a target pollutant over the Pd/La0.8Ce0.2MnO3/ZSM-5 catalysts was investigated in a fixed-bed reactor and the effect of calcination temperature, active component loading and ZSM-5 properties on the catalytic performance was investigated. The results indicated that the Pd/La0.8Ce0.2MnO3/ZSM-5 preserves the perovskite structure and the active Pd component is evenly dispersed on the catalyst surface, which endures the catalyst with high activity in toluene combustion. Over the La0.8Ce0.2MnO3/ZSM-5 catalyst with La0.8Ce0.2MnO3 loading of 20%, ZSM-5 Si/Al atomic ratio of 25, and calcination temperature of 750℃, the ignition and complete combustion temperatures for toluene combustion are only 200 and 279℃, respectively. After being modified with 0.3% Pd, the activity of the Pd/La0.8Ce0.2MnO3/ZSM-5 catalyst is even largely enhanced; over it, the ignition temperature for toluene combustion is decreased by 90℃ and complete combustion is achieved at 230℃.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
