Abstract: The effects of heating rate on migration, transformation and occurring forms of nitrogen during pyrolysis of Shengli brown coals were studied in a fixed-bed/fluidised-bed quartz reactor. The results indicate that the yields of NH3 and HCN from the fast pyrolysis were much higher than those from the slow pyrolysis. The difference in the yields of NH3 and HCN between the fast and slow heating rates increases with the increasing pyrolysis temperature. The maximum productions of NH3 and HCN mostly occur at 973K, which is attributed to the enhanced condensation and secondary reactions with the increasing pyrolysis temperature. The release rate of char-N is faster than the weight loss rate of char itself at fast heating rate. The results from X-ray photoelectron spectroscopy (XPS) analysis imply that the pyrolysis process has facilitated the transformation of pyrrolic (N-5) to quaternary type nitrogen (N-Q) and pyridinic (N-6). It seems that the fast heating rate favors the formation of N-6 while the content of N-Q in char is relatively high at the slow heating rate.
Abstract: Ximeng brown coal was leached by HF, HNO3 and HCl solution step by step in order to study the effects of acid pretreatment on the formation of gaseous products during coal pyrolysis. A fixed bed pyrolysis-gas chromatography was used to analyze the release behaviors of gaseous products from pyrolysis of raw and the pretreated coals. The results show that there is an obvious influence of acid pretreatment on the release behaviors of hydrogen-, oxygen-and sulfur-containing gases during coal pyrolysis. The formation routes, stages and release temperature intervals for various gases are different, which result in that the influences of minerals removed by acid leaching behave significantly different. The gaseous products were also dramatically influenced by oxidative characteristic during HNO3 pretreatment, which causes that the release amount of hydrogen-containing gases decreases, and that of oxygen-containing gases increases. There is a discrepant influence on the release of H2S and COS by HNO3 pretreatment; the former decreases and the later increases.
Abstract: The steam gasification kinetics of four different metamorphosed coals at mid-temperature (700~850℃) using potassium carbonate as catalyst was investigated with the isothermal thermogravimetric analysis under ambient pressure. The results show that the catalysis is greater for the high metamorphosed coal gasification. The integrated model and modified random pore model are good to correlate the relationships between carbon conversion and time for the case with potassium carbonate catalyst. However, the volumetric reaction model is poor in the fitting of data. The activity energy and pre-exponential factor were predicted from the modified random pore model. The activity energy of coal char catalytic gasification ranges from 90.317~167.861 kJ/mol. And there are compensation effects between reaction activity energy and pre-exponential factor.
Abstract: The occurrence characteristic and contents of 32 trace elements in 15# and 16# coals in Yimin were analyzed using ICP-MS combined with demineralization and extraction of humic acid. Compared with Clark values and contents of trace element in Jurassic-Cretaceous coal in China and lignite in the world, there were no obvious enrichment of the trace elements in Yimin raw coal. Contents of most trace elements, expect Ni and As, in demineralized coals are lower than those in the raw coal. Some trace elements, Ni, Mo, Cd, Sn, and W significantly enriched in humic acid extracted from raw coal and demineralized coal, which indicates that these elements form the stable organic-compounds with humic acid. Meanwhile V, Ni and As were found to be enriched in raw coal and demineralized coal,which showed that the stable organic-compounds could be formed between V, Ni,As and coal macromolecule. 6 kinds of trace elements in Yimin coal are classified based on correlation coefficient between ash and trace element: inorganic enriched elements-Cr and U; inorganic affinity element-Cu, Cd, In, Sn, Ga, Y, Zr, Hf, Bi and Th; the tendency of inorganic affinity element-Be, Sc, Rb, Sr, Nb, Cs, Ta and Pb; the tendency of organic affinity element-V, Cr, Co, Cu, Se, Y, Mo, Cd, Sn, Sb, Ta and Tl; the organic affinity element-Li, Co and W; the organic enriched elements-Ni, Zn, Mo and Sb.
Abstract: Cotton stalk and wood scraps were burnt in a tube furnace to generate soot under different combustion conditions. Soot particles were sampled and detected by TEM, EDS and GC-MS to study their physicochemical properties, then the formation mechanics of soot during biomass burning was deduced. The results show that the typical morphological structures of soot are capsule-like, spherical, catenulated and reticular. Combustion conditions enfluence the burning process and result in the different morphology of the soot. The soot particles collided and coagulated during nucleation and growth of soot, which leads to formation of complicated clustered particles. During biomass burning the soot is mainly generated from pyrolysis of cellulose, which contains furfurans, phenols, aldehydes, furans, alkanes and alkenes. The formation mechanics of soot has been speculated. During burning of biomass, the chemical bonds of cellulose fractured and restructured, which generate CO, CO2, residual carbon molecule fragments, and so on. Then residual carbon goes on a series of reactions such as reforming, dehydration, carbonization and bond-breaking to generate aldehydes and ketones. And these compounds polymerized and cyclized to form benzene ring structure, and further converted to toluenes and phenols.
Abstract: The relative hydrogen-donating abilities of different heavy oils were determined by 1H-NMR. Three typical heavy residues and the corresponding subfractions were thermally treated with equal weight of chemical accepting probe (i.e. anthracene) at 380℃ for 8 min under the nitrogen pressure of 4MPa; the toluene insoluble yield, gas yield and composition, and the distillation curve of liquid products were determined. The results show that the thermal reaction of samples under the testing conditions is relatively moderate with no apparent structural changes. By comparing the hydrogen distribution of samples with that of residues after reaction, it is proved that the primary reaction during the thermal process can make the hydrogen transfer from oil samples to anthracene. The reduction value of the hydrogen content of Hcβ(chemical shift ranging from 1.4~2.0 in 1H-NMR spectrum, representing naphthenic hydrogen two positions from the aromatic ring of naphtheno-aromatics) and Hcα (chemical shift ranging from 2.5~4.7 in 1H-NMR spectrum, representing hydrogen on naphthenic ring adjacent to fused aromatic ring of naphtheno-aromatic) is correlated well to the donated hydrogen content measured by chemical method. Thus it is reasonable to regard Hcβ and Hcα as the main donated hydrogen during mild thermal conversion of heavy oils, and to entatively evaluate the relative hydrogen-donating ability of heavy oil using the two type protons content in 1H-NMR is acceptable.
Abstract: The effect of ultrasomic treatment on the hydrotreating of residue was studied using 4 vacuum residues. Ultrasonic treatment can change the average structure of residue and the content of SARA fractions, and the structure of asphaltene at the same time, improving the hydrogenation performance. The hydrogenation of residue after ultrasonic treatment makes a decrease in the yield of coke and residue of above 500℃ but a increase in the yield of gas, gasoline, diesel distillate fractions and VGO and an increase of about 6 to 10 percentage points in light oil yield. The conversion of residue is improved, and the upgrading action is apparent. The upgrading of residue with ultrasonic treatment is related to the material type. The changes can be explained by the syphonage model in a macro level. It is also found that the removal of heteroatom, especially vanadium metal, is improved with the average removal rate of over 96%. After hydrogenation of residue, SARA fractions of residue are changed, the content of saturate and asphaltene is increased, but the aromatic and resin is reduced.
Abstract: A novel mesoporous Ni-CaO-ZrO2 catalyst with high surface area and pore volume was prepared by one-pot template-free method and applied in CH4-CO2 reforming. The mesoporous Ni-CaO-ZrO2 catalyst was characterized by means of nitrogen sorption, SEM, TEM, XRD, H2-TPR and TG-DSC. The results indicated that a strong metal support interaction (SMSI) present in the Ni-CaO-ZrO2 catalyst induces an intimate contact between Ni and ZrO2 nano-particles, which is favorable for the surface reaction of adsorbed reactant species for CH4-CO2 reforming. Owing to the mesoporous framework and SMSI, the Ni-CaO-ZrO2 catalyst shows promising activity and stability in CH4-CO2 reforming. Most of the carbonaceous deposits on the catalyst surface are in whisker form, which does not cover the active sites and then has little influence on the catalyst stability.
Abstract: The CuO-ZnO-Al2O3/HZSM-5 catalyst prepared by co-precipitation and mechanical mixing with HZSM-5 was used for hydrogen production from steam reforming of dimethyl ether. The effects of Cr, Zr, Co and Ce promoters on catalyst performance were investigated by means of X-ray diffraction(XRD), temperature programmed reduction (H2-TPR), SEM and BET. The results showed that addition of promoter Cr can reduce the average pore diameter and reduction temperature of catalyst effectively, and inhibited the form of Zn(OH)2 in the catalyst preparation process. The conversion of dimethyl ether and hydrogen yield reaches 99% and 95% respectively at low reaction temperature. The effects of reaction termperature, space velocity and steam-to-DME ratio were investigated. At the conditions of 250℃, the space velocity of 3884mL/(g.h), H2O/DME=5, over 97% of DME conversion was obtained over the CuO-ZnO-Al2O3-Cr2O3/HZSM-5 catalyst and the catalytic activity has no obvious deactivation during 50h durability test.
Abstract: Two Al2O3-modified catalysts were prepared by urea hydrolysis method and precipitation disposition method respectively. Combined with N2 adsorption, XRD, XPS and H2-TPR, the effects of Al2O3 on the physico-chemical properties and catalytic properties for the Fischer-Tropsch synthesis were investigated. It was found that the metal-support interaction could be effectively strengthened for both catalysts. Consequently, the dispersion of the catalyst was enhanced and the Fischer-Tropsch synthesis activity was increased. The results also indicated that the modification of Co/SiC catalyst strongly depended on the preparation method. The highest CO conversion was observed on the catalyst prepared by urea hydrolysis method due to the superior dispersion and good reducibility. Besides, the catalytic stability was enhanced due to the stronger interaction between cobalt and Al2O3 prepared by precipitation disposition method.
Abstract: Vanadyl sulfate (VIVOSO4) was used to prepare carbon-supported vanadium catalyst for flue gas desulfurization. The VIVOSO4 impregnated on activated carbon (AC) was easily oxidized into vanadium(V) sulfate phase (possibly V2O3(SO4)2) in air, which exhibited high catalytic activity toward SO2 oxidation, thus significantly enhancing SO2 retention on AC. Furthermore, the vanadium(V) sulfate can be decomposed upon calcination in nitrogen with optimum temperature of 500 ℃ to form vanadium(V) oxide, further improving SO2 retention mainly due to increase in micorpore volume suitable for sulfate storage and showing suitability of vanadyl sulfate to prepare traditional V2O5/AC catalyst. To obtain fully oxidized vanadium oxides, preoxidation was carried out on catalyst after calcination. However, due to ablation of carbon support, reduction of vanadium and/or formation of surface oxygen groups, the preoxidation was negative for SO2 retention. Additionally, this paper provided preliminary evidence indicating transformation of vanadium(V) oxide in V2O5/AC into vanadium(V) sulfate during desulfurization. Combined with catalytic role of vanadium(V) sulfate for SO2 oxidation, SO2 removal on V2O5/AC likely followed a mechanism that the vanadium(V) oxide firstly transformed into vanadium(V) sulfate and the latter was then responsible for subsequent SO2 oxidation into H2SO4.
Abstract: Au/Co3O4 catalysts with different gold loadings were prepared by the deposition-precipitation method using HAuCl4 solution through adjustment of the pH value to 7, 9 or 11. Their catalytic properties for N2O decomposition in the presence of oxygen were investigated. 0.29%Au/Co3O4 catalyst prepared at the pH value of 9 exhibited higher catalytic activity than 0.31%Au/ZnCo2O4 prepared under optimal conditions although ZnCo2O4 was more active than Co3O4. AES, BET, XRD, SEM, XPS and H2-TPR characterization results indicated a synergistic effect existed between gold and cobalt species in Au/Co3O4, which is, however, absent in the Au/ZnCo2O4. Despite that N2O was completely decomposed at 500 ℃ in oxygen atmosphere for both the samples, the N2O conversion was decreased to 92% and 63% after the reaction was carried out for 10 h in the presence of both oxygen and steam over the 0.29%Au/Co3O4 and the 0.31%Au/ZnCo2O4, respectively.
Abstract: A series of M/REY(M=Cu, Mn, Fe, Ce) catalysts were prepared by impregnation method. The catalysts were characterized by XRD, NH3-TPD, NO-TPD and H2-TPR, and XPS. The catalytic activity of the catalysts was evaluated in the fixed-bed reactor for the selective catalytic reduction of NO with NH3 in the presence of SO2. The results show that the performance of catalysts was affected by the type and load of active component. The Cu(3)/REY catalyst exhibited good activity at low temperature in presence of SO2. The NO conversion is over 95% at the temperature range of 254~390℃. The catalytic activity of Cu(3)/REY catalyst is related with its excellent redox properties and the performance of NO adsorption-desorption.
Abstract: Qualitative and quantitative analysis methods for ultra trace sulfides in natural gas were established based on GC-MS and GC-SCD, and utilized to determine the sulfides in the domestic natural gas of Beijing. The results indicate that the natural gas contains three kinds of sulfides, and the main component accounting for 94.2% is tetrahydrothiophene (THT). ZnO/Al2O3 was prepared by co-precipitation, and ZnO/γ-Al2O3, CuO/γ-Al2O3 and CuO-ZnO/γ-Al2O3 were prepared by impregnation. Experimental research on the deep removal of THT in the city natural gas was carried out with these desulfurizers. It is found that THT can be removed to less than 10×10-9 (molar fraction)with CuO/γ-Al2O3 and CuO-ZnO/γ-Al2O3 in a wide temperature range from 50~500℃, which can meet the requirements of desulfurization depth and working temperature width for distributed PEMFC power station based on natural gas.
Abstract: ZSM-5 zeolites were treated by Na2CO3 solutions with different concentrations and characterized by XRD, XRF, SEM, N2 sorption and NH3-TPD techniques; the influence of Na2CO3 treatment on their pore structure, acidity and performance in thiophene alkylation was investigated. The results showed that the BET surface area, external surface area and mesoporous volume of the ZSM-5 zeolites were enhanced through Na2CO3 treatment and the acidity was also modulated without altering the microporous structure of ZSM-5 zeolites. The activity and the selectivity to alkylates of the ZSM-5 zeolites in thiophene alkylation are also improved after Na2CO3 treatment. With the increase of Na2CO3 solution concentration, the thiophene conversion over the hierarchical ZSM-5 zeolites increases gradually, while the selectivity to alkylates increases first, reaches a maximum and then decreases along with the Na2CO3 solution concentration. When the Na2CO3 concentrations are 2 and 3 mol/L the thiophene conversions and alhylation selectivities are 81.26%, 73.15% and 90.57%, 72.59%, respectively.
Abstract: Novel hexagonal prism polycrystalline γ-Al2O3 particles were hydrothermally synthesized in ammonia medium by using AlCl3·6H2O as aluminum precursor. The γ-Al2O3 particles were characterized by means of XRD, SEM, TEM and nitrogen sorption measurements and the formation mechanism of crystal morphology was investigated. The results indicated that after the hydrothermal treatment of aluminum precursor in ammonia medium as well as the later calcination process, γ-Al2O3 particles with perfect hexagonal prism shape can be obtained; the border size and length of the hexagonal prism are about 0.3 and 2.5 μm, respectively. TEM images show that the hexagonal prism γ-Al2O3 particles are aggregated with fine particles of about 10 nm and then take the polycrystalline gamma phase. Such a γ-Al2O3 material exhibits a BET area of 274 cm2/g and pore volume of 0.51 cm3/g with a narrow pore size distribution centered at 5.5 nm. The results also suggest that the formation of the hexagonal prism γ-Al2O3 particles is closely related to the arrangement of the steady AlOOH precursors interacted with NH+4 ions.
Abstract: ZSM-5/MCM-41 composite molecular sieves with multiple micro-mesoporous structure were hydrothermally synthesized via self-assembly by using the alkali-treated ZSM-5 seriflux as the source of silica and aluminum. The as-synthesized molecular sieves were characterized by XRD, N2 adsorption, HRTEM, Py-IR, and hydrothermal treatment methods. The results showed that the crystallinity of the as-synthesized molecular sieves is dependent on the intensity of the alkali-treatment; the suitable alkali treatment conditions for ZSM-5 are 80℃ for 1 h with a NaOH concentration of 1 mol/L. The composite molecular sieves obtained exhibit a typical MCM-41 structure, with a hierarchical micro-mesoporous structure and large specific surface area. Compared with MCM-41, the ZSM-5/MCM-41 composite molecular sieves show higher quantity of Bronsted acid sites (especially strong ones) and higher hydrothermal stability.
Abstract: β-cyclodextrin (β-CD) with a special cavity structure was firstly grafted on the surface of multi-walled carbon nanotubes (MWCNTs), which were then immobilized on Ti plates to obtain the β-CD/MWCNT/Ti substrate. Binary Pd-Ni nanoparticles were electrodeposited on the surface of β-CD/MWCNT/Ti substrate to prepare the PdNi-β-CD/MWCN/Ti electrode; its activity in electrocatalytic oxidation of propanol and butanol isomers in alkaline media was then investigated by voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results indicated that the binary PdNi nanoparticles are highly dispersed with the size of 90~130 nm on the β-CD/MWCNT/Ti substrate. The configuration of alcohols plays a significant role in their electrochemical oxidation activity in alkaline media on the PdNi-β-CD/MWCNT/Ti electrode. For the two propanol isomers, the PdNi-β-CD/MWCNT/Ti electrode exhibits much higher electroactivity for 1-propanol oxidation than that for 2-propanol oxidation. For the four butanol isomers, the electrocatalytic activity of the PdNi-β-CD/MWCNT/Ti electrode towards their oxidation follows the order of 1-butanol > 2-methyl-propanol > 2-butanol >> 2-methyl-2-propanol; the electrode shows almost no electrocatalytic activity in the oxidation of tertiary butanol. The mechanism for the electrocatalytic oxidation of various propanol and butanol isomers was also analyzed by considering the Muliken net charge on the different carbon atoms bonded with hydroxyl –OH, which indicates that the alcohol molecule with lower Muliken net charge value will be more easily oxidized over the PdNi-β-CD/MWCNT/Ti electrode.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
