Abstract: Through observing the change of morphology and contact angle of coal ash column on the surface of refractories with increasing temperature, surface wettability of refractories was determined. The erosion and permeation behavior of coal ash on refractories during coal ash sintering process were observed and analyzed by using scanning electron microscope (SEM) and energy spectrum analysis. The morphology of slag sample, cross-section image of refractories and the change of element were studied. The results show that temperature is an important factor which influences the wettability and erodibility of coal ash on the surface of refractories. The erosion-resistance to coal ash varies between different refractory, which depends mainly on the composition and structure of refractories. Among these factors, compact structure is especially important. In fact, the corrosion of coal ash on refractories is the result of corrosion and permeation mineral elements between coal ash and refractory materials. During the process of corrosion, chemical reaction inhibits or promotes the corrosion. The wettability of coal ash on the surface of refractories is accordant with erosion behavior of coal ash on refractories.
Abstract: Extraction of direct liquefaction residue from Shenhua coal with three solvents was investigated in a batch autoclave at supercritical conditions to clarify the impacts of pressure, temperature, and extraction time on the yields of heavy liquid and its compositions. It is found that when toluene is used as a solvent, extract time has no obvious effect on yield of heavy liquid, hexane soluble(HS) and asphaltene(A). Extract temperature, extract pressure and mass ratio of solvent to residue have significant effect on yield and composition of residue extract. During the supercritical solvent extraction of liquefaction residue, some other components are transformed into HS and this results in increasing yield of HS. Benzene shows similar extraction ability to toluene while ethanol is poor in dissolving heavy liquid. There are more light components in heavy liquid extracted by ethanol than those by benzene and toluene. Sulfur and ash are mainly enriched in extract residue during extraction process.
Abstract: The catalysis of K2CO3, Na2CO3, Ca(OH)2 and Ni(NO3)2 on the hydrogasification of Hohhot coal was studied in a pressurized fixed-bed reactor, in which the effects of temperature were investigated. The experimental results show that different kinds of metal have a significant difference in the catalysis to the hydrogasification reaction, and the order of catalytic activity is as follows: K > Na> Ni > Ca. Compared with the non-catalytic coal hydrogasification, the temperature of hydrogasification catalysed by K2CO3 is dropped by more than 150℃ under the same carbon conversion at the same time and reduced about 150℃ by Na2CO3 and more than 50℃ by Ni(NO3)2. However, the adding of Ca(OH)2 even decreases the observed carbon conversion due to the sorption of Ca(OH)2 for CO2 produced. The SEM and BET results show that coal samples loaded with different metal compounds catalysts have different surface morphologies and pore structures as well.
Abstract: To better understand the combustion process of pulverized coal under pressurized oxy-fuel atmosphere, the influence of pressure on the combustion characteristics and mineral conversion during the pressurized oxy-fuel combustion was investigated by using the combination of pressurized thermogravimetric analyzer (PTGA) and X-ray diffractometer (XRD). The results indicate that the heterogeneous ignition at atmospheric pressure changes to the homogeneous ignition with the increase of pressure, but starts to change to the heterogeneous ignition gradually at 3 MPa, and becomes the heterogeneous ignition at 5 MPa. As a result of the transformation of ignition mechanism of pulverized coal, the combustibility index S increases firstly and then reduces with pressure. And the combustion temperatures may be different for different ignition mechanisms. Because of higher combustion temperature of the heterogeneous ignition at atmospheric pressure, some minerals, such as mullite, are generated in the ash, while some other minerals, such as illite, are found in the ash owing to lower combustion temperature of the homogeneous ignition at 1 MPa. As the pressure continues rising, the illite converts to mullite due to the homogeneous ignition transforming to the heterogeneous ignition.
Abstract: Oxygen carrier is one of the essential issues of Chemical Looping Combustion (CLC). In this paper, Fe-based oxygen carriers were prepared by the following seven methods: sol-gel method, co-precipitation method, hydrothermal synthesis method, low-heating solid-state reaction method, mechanical mixing method, combustion synthesis method, and freeze granulation method. The appropriate preparation methods were selected and optimized for preparation process through physical and chemical characterization. Firstly, the hardness tests of the oxygen carriers showed that the oxygen carriers prepared by sol-gel, co-precipitation, mechanical mixing, combustion synthesis, and freeze granulation are harder than others. Then, these oxygen carriers were tested by X-Ray Diffraction (XRD), and Fe2O3/Al2O3 crystalline phase were found in all these samples. Further XRD analysis showed that the crystallinity and crystallite size of oxygen carriers gradually increased with the increase of calcining time and temperature. The mechanical property, crystal structure and composition of crystalline phase are the most stable when the calcining temperature is 1 200℃. Finally, Temperature Programmed Reduction Reaction (TPR) experiments by the Chemisorption Instrument were carried out to characterize the reactivity of the oxygen carriers, and the activity degree of oxygen carriers was obtained. Following these physicochemical characterizations, the sol-gel method and freeze granulation method were recognized as best for the preparation of Fe2O3/Al2O3 oxygen carrier.
Abstract: A process of light oil recovery from oil-shale pyrolysis gas by using active carbon fiber adsorption was explored, and a moving-bed pyrolysis apparatus and a light oil recovering system were set up. By cooling the gas to room temperature and condensation, more than 20 g/m3 of light oil faction during the pyrolysis of Huadian oil shale are obtained. The light oil can be recovered completely by using the activated carbon fiber adsorption. The competitive adsorption of various compounds by activated carbon fiber shows that benzene, toluene, xylene, ethylbenzene and the hydrocarbons with more than ten carbon atoms are absorbed strongly, while the alkane, olefin and cyclane with six to nine carbon atoms are absorbed weakly. The research can provide fundamental data to the process development of light oil recovery from oil-shale pyrolysis gas.
Abstract: The pyrolysis mechanism of levoglucosan (one of the major product from cellulose pyrolysis) was investigated by using density functional theory at B3LYP/6-31++G(d,p) level. Four possible reaction pathways were proposed and the geometries of reactant, transition states, intermediates and products for each pathway were fully optimized; the standard thermodynamic and kinetic parameters of each reaction at different temperatures were calculated. The results showed that levoglucosan is converted to intermediate IM1 via transition state TS1 with an activation energy of 296.53 kJ/mol by breakage of C(1)-O(7) and C(6)-O(8) hemiacetal linkages and formation of C(5)-C(6)-O(7) circular structure, and then IM1 is converted to intermediate IM2 via transition state TS2 with an activation energy of 234.09 kJ/mol. IM2 can be further decomposed via four different pathways. Pathways 1 and 4 involve decarbonylation reactions with high energy barriers, and as a result, they are unlikely to occur; on the other side, the energy barriers for the rate-determining steps of pathways 2 and 3 are much lower, which are kinetically favorable and possible the major reaction channels for IM2 pyrolysis.
Abstract: The production of syngas from partial oxidation of bio-oil under atmospheric air was investigated. The effects of temperature and the ratio of oxygen to bio-oil on the quality of syngas were examined. The reaction mechanism of the process was discussed. The results show that raising temperature can promote the production of syngas from bio-oil by non-catalytic partial oxidation. The appropriate ratio of oxygen to bio-oil is beneficial to enhance the effective components of syngas. When the temperature reaches to 1 050℃, air flow is 0.2 L/min and feed rate is 72 g/h, the contents of H2 is the highest and that of CH4, CO and CO2 is very low. Both H2/CO and H2/(CO+CO2) value reached the maximum.
Abstract: A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method. The variables studied were difference ratio and calcination temperatures. Pt/Co(10:90)/Al2O3 catalyst calcined at 700℃ was found to be the best catalyst which able to convert 70.10% of CO2 into methane with 47% of CH4 formation at maximum temperature studied of 400℃. X-ray diffraction analysis showed that this catalyst possessed the active site Co3O4 in face-centered cubic and PtO2 in the orthorhombic phase with Al2O3 existed in the cubic phase. According to the FESEM micrographs, both fresh and spent Pt/Co(10:90)/Al2O3 catalysts displayed small particle size with undefined shape. Nitrogen Adsorption analysis showed that 5.50% reduction of the total surface area for the spent Pt/Co(10:90)/Al2O3 catalyst. Meanwhile, Energy Dispersive X-ray analysis (EDX) indicated that Co and Pt were reduced by 0.74% and 0.14% respectively on the spent Pt/Co(10:90)/Al2O3catalyst. Characterization using FT-IR and TGA-DTA analysis revealed the existence of residual nitrate and hydroxyl compounds on the Pt/Co(10:90)/Al2O3 catalyst.
Abstract: Ni-ZrO2 and Ni-Mg-ZrO2 catalysts were prepared by a co-precipitation method, and then were characterized by BET, XRD, H2-TPR and CO2-TPD techniques. The performances of catalysts in the tri-reforming of coal bed methane to syngas were studied in a fixed bed reactor. The reaction conditions (temperature and feed gas composition) were mainly investigated. The results showed that at t=800℃, atmospheric pressure, CH4/CO2/H2O/O2/N2=1.0/0.45/0.45/0.1/0.4, GHSV=30 000 mL/(g·h), about 99% of CH4 conversion, 65% of CO2 conversion, and VH2/VCO of 1.5 could be achieved during 58 h of reaction, which are related to the strong metal-support interaction, the good thermal stability and basic nature of the catalyst. Furthermore, high temperature favors the tri-reforming of methane. By adjusting the feed gas composition, a specific VH2/VCO could be achieved.
Abstract: In oleum, a series of the catalyst such as sulfate compound, transition metal compound, iodine compound that could be used for catalyzing low concentration of CBM were observed. The experimental results show that catalytic effect of iodine was the best, conversion rate of low concentration of CBM could reach 79.69% and the methane selectivity reached 83.74%.Then, the effect of concentration of iodine catalyst was studied. With the concentration of iodine catalyst increased, the conversion of low concentration of CBM increased untill it reached a maximum and then dropped down. According to the liquid partial oxidation reaction mechanism of methane in oleum solution, the liquid partial oxidation reaction mechanism of low concentration of CBM in oleum solution may be the electrophilic substitution.
Abstract: Dimethyl ether (DME) synthesis from biomass-derived syngas in a slurry-bed reactor was investigated over a hybrid catalyst composed of methanol synthesis catalyst and molecular sieve. The results showed that the catalyst containing SAPO-11 exhibits higher DME selectivity and catalytic stability, which is closely related to the weak acidity of SAPO-11 in the hybrid catalysts. 40% CO conversion and 95% DME selectivity in organic products could be kept during 35 h stability test over the hybrid catalyst when the weight ratio of methanol synthesis catalyst to SAPO-11 was 3.
Abstract: A series of Ru based ammonia synthesis catalysts supported by ceria with different promoter precursors,such as KF、KNO3、Ba(NO3)2、CsNO3,were prepared.Not only studied the effect of single and double promoters for the catalytic activity but also studied the effect of promoters’ kinds and content.N2 physisorption,CO chemisorption and X-ray diffraction were carried out to investigate the effect of promoter on surface area,pore size distribution and ruthenium dispersion of catalysts.It has been found that the effectiveness of F ion just like the role of alkaline or alkaline-earth-promoter for ammonia synthesis.For the single-promoted Ru/CeO2 catalyst,cesium proved to be most effective in the studied four promoters.For the double-promoted one,the activity of the catalyst was affected remarkably by cesium and barium co-exists.Ammonia synthesis concentration of over 13.3% was obtained over Ba+Cs-Ru/CeO2 catalyst under 400℃,10 MPa and 10 000 h-1.The structure and the surface property of Ru/CeO2 catalyst were changed when promoters added.But the real factor to improving catalytic activity is electronic effect rather than structural factors.
Abstract: Ordered mesoporous alumina (OMA) with high surface area, large pore volume, and narrow pore-size distribution was synthesized from organic aluminum precursors and anionic templates; the influence of various preparation parameters such as hydrolysis speed of the aluminum precursor, chain length of the carboxylic templates and washing medium on the properties of as-synthesized OMA was investigated. With OMA as support, rhenium-based catalyst was prepared by incipient-wetness impregnation method and used in the metathesis of butene to propene. The results showed that increasing hydrolysis speed of the aluminum precursor as well as using ethanol as the washing medium are beneficial to the formation of the organized pore structure; the pore volume and pore diameter of as-synthesized OMA increase with an increase of the chain length of the carboxylic templates used here. Compared with the rhenium catalyst supported on conventional mesoporous alumina, the rhenium-based catalyst prepared with OMA as the support exhibits better performance in the metathesis of butane, i.e. higher selectivity to propene and longer catalytic life; the conversion of butane and selectivity to propene reach 50% and 60%, respectively.
Abstract: Beta-Y composite zeolites were prepared by two methods and were characterized by XRD, SEM, FT-IR and N2 adsorption. The results indicated that sample A synthesized with Beta zeolite as unique silica source is a composite zeolite of Beta and Y in a mechanical mixed mode, while sample B synthesized with mother liquor of Beta zeolite as precursors is a composite zeolites with core-shell structure. The core-shell Beta-Y composite zeolite (sample B) owns crystal lattices of Y zeolite as shell and Beta zeolite as core and is provided with centralized mesopore.
Abstract: In order to improve the activity of catalytic oxidation of NO over MnOx/TiO2,a certain amount of cerium nitrate was doped into the catalyst while the MnOx/TiO2 catalyst was prepared by impregnation on TiO2.Ce(1)Mn(3)Ti catalyst was characterized,using XRD,BET and XPS.At the same time,the effects of H2O and SO2 on catalytic oxidation of NO were investigated.The deactivation mechanisms in the presence of H2O and SO2 were analyzed by FT-IR,SEM and BET.The results showed that Ce(1)Mn(3)Ti yielded a 58% NO conversion at 200℃,and 85% at 250℃ when the space velocity was 41 000 h-1,O2 and NO concentrations were 10% and 300×10-6respectively.The activity of catalyst declined in the presence of only 4% H2O but this negative effect could be counteracted by increasing the reaction temperature.After in the presence of 4%H2O and 100×10-6 SO2 together,NO conversion was maintained at 48%.The activity of the deactivated catalyst could recover to 61% after removing H2O and SO2.H2O and SO2 make catalyst deactivation because of the active component has been sulfuric acid stalinization.
Abstract: NiCoAl ternary mixed oxides derived from hydrotalcite-like compounds (HLc) with (Ni+Co)/Al atomic ratio of 3 and Ni/Co of 0.2 were incipiently impregnated by potassium carbonate solution to prepare K-promoted NiCoAl mixed oxides for catalytic decomposition of N2O. The effects of catalyst preparation parameters such as K loadings, calcination temperatures, and reaction atmospheres on catalytic activity were investigated. The catalysts were characterized by BET, XRD, H2-TPR, and XPS techniques. The results show that the catalytic activity of NiCoAl mixed oxides is largely enhanced by the addition of K species in the presence of oxygen and steam, and the optimal catalyst preparation parameters are K/(Ni+Co) atomic ratio of 0.05 and calcination temperature of 400℃. XPS and H2-TPR data show that the electron binding energy of active Co3O4 and NiO species over K-promoted catalysts surface shifted to lower value, indicating the surface Co-O and Ni-O bonds were weakened, thus the reduction peaks of Co3+ to Co2+ and Ni2+ to Ni0 moved to lower temperature, and the catalytic activity and resistance towards water is improved.
Abstract: High-performance catalyst of molecular sieve supported transition metals and rare earth element was prepared by traditional impregnation method,and the catalytic activity was checked by microwave assisted catalytic oxidation of benzene in our study.It indicated that 5A type molecular sieve obtained from Tianjin kermel was an excellent carrier,and molecular sieve supported copper (Cu),manganese (Mn) and cerium (Ce) catalyst had a complete combustion temperature of 230℃ for benzene.The appearance of Cu1.5Mn1.5O4 with crystalline spinel phase and amorphous phase improved the catalytic activity greatly,and the promoting effect of Ce was also significant.Molecular sieve loaded Cu-Mn-Ce catalyst showed good stability and high catalytic capacity after operating with 30 h.Based on the characteristics of the special surface area and surface morphology,it was found that the special surface area and pore size of the catalyst were enlarged during calcination and reaction,which are beneficial to the adsorption and oxidation of benzene.X-ray diffraction results showed that the crystalline structure of molecular sieve did not change significantly,and CuO and Mn2O3 were dispersed mainly onto the surface of the catalyst.
Abstract: Catalytic combustion of ultra-low content methane was carried out in a fluidized bed reactor with Cu/γ-Al2O3 catalysts as particle bed material; the effects of bed temperature (450~700℃), fluidizing velocity ratio (ω, 1.5~4), and inlet methane concentration (0.3%~2%) on the combustion characteristics were investigated. The results show that the bed temperature is a major influencing factor for the catalytic combustion; methane conversion increases with the bed temperature. When the bed temperature reaches 650℃, methane conversion exceeds 95% with the methane concentration lower than 1%; methane can be almost completely converted when the bed temperature reaches 700℃ and the fluidizing velocity ratio ω is not higher than 2. Methane conversion decreases with the increase of the fluidizing velocity and inlet methane concentration; when ω exceeds 3.5, the influence of temperature on methane conversion becomes less significant with an increase of the unburned methane content. Under a low temperature, the combustion is controlled by the catalytic reaction rate; activation energy Ea and reaction order m estimated by regression are 1.26×105 J/mol and 0.73, respectively. When the bed temperature exceeds 450℃, mass transport limitations turns to an important factor influencing the methane conversion.
Abstract: Equilibrium adsorption data of methane on Ajax activated carbon were volumetrically measured under a temperature of 268.15~338.15 K and a pressure up to 13.5 MPa. Accessible volumes for methane molecules and critical pore width for methane effective adsorption were introduced; on the basis of these concepts, the mass balance of the adsorbate confined within the adsorption cell was used to determine the relationship among the total amount, excess adsorption amount and absolute adsorption amount. By considering the accessible volume and critical pore width, the excess adsorption amount was obtained by the pore size distribution (PSD) determined by Nonlocal Density Functional Theory (NDFT) calculation. The equilibrium adsorption data were fitted by Toth model through nonlinear regression, which was verified the accuracy in predicting the absolute adsorption amount. The isosteric heat of methane adsorption on activated carbon was over-estimated by using the excess amounts, but underestimated by using the total amounts. The isosteric heat of adsorption should be determined from the adsorption isosteres of absolute adsorption amount when considering the thermal effect in adsorption process.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
