Abstract: This paper focuses on preparation of colloidal solution of graphene-like structures from different ranks of coals: brown coal, bituminous coal, low-volatile bituminous coal, anthracite. It was found that brown coal thermo-oxidative destruction leads to formation of small d=32 nm (V=17%) and large d=122 nm (V=11%) fractions of nanoparticles. The thermo-oxidative destruction of bituminous coal leads to formation of nanoparticles d=50 nm (V=5.2%) and d=164 nm (V=16%). Thermo-oxidative destruction of low-volatile bituminous coal and anthracite leads to formation of nanoparticles, predominantly, d=122-190 nm. Carbon nanostructures obtained from coal are negatively charged at pH=2-12. Colloidal solution of carbon nanostructures at dispersed phase concentration 0.01 mg/mL is stable for 1 month. Electron diffraction patterns and X-ray analysis of carbon nanostructures showed that nanostructure from brown coal is amorphous and nanostructure from anthracite is crystalline. Results of coal macromolecules modeling and graphene-like structures obtained from them are presented.
Abstract: To decrease tar yield and thus improving gasification efficiency, tar from pyrolysis of Shengli brown coal was catalytically reformed in situ in a two-stage quartz reactor using char (as catalyst) prepared from the pyrolysis of same coal. The properties of char catalysts before and after reactions were analyzed and compared. The results show that the mass of char generally decreases after the reforming reactions, which means that char is a kind of consumptive catalyst. The maximum reduction in specific surface area after reactions is from 422 to 231.8 m2/g. Results from Raman spectroscopy show that the O-containing functional groups, as well as the ratio of small aromatic rings (3-5 aromatic rings) to big aromatic rings (more than 5 aromatic rings) in char, decrease after the reactions. Besides, it appears that during the interaction between char and volatile, char from fast-heating pyrolysis mainly cracks the volatiles into small-molecule gases, while char from slow-heating pyrolysis removes the volatiles by coking on its surface.
Abstract: A Cu-olivine oxygen carrier was prepared using impregnation method and used for steam gasification of coal char in a fixed bed reactor. It is shown that higher gasification temperature and steam/C molar ratio conduce to an increase in carbon conversion and syngas yield. The increase of CuO loading on the oxygen carrier and the oxygen carrier/char weight ratio leads to a higher carbon conversion but a lower syngas yield. The reaction activity of oxygen carrier has not been reduced after multiple regenerations at 950 ℃, which indicates that the olivine could inhibit the sintering of the supported Cu/CuO. The gasification at 800 ℃ in the presence of the oxygen carrier after 8th regeneration has a carbon conversion of 42.3%, a water conversion of 57.3% and a syngas yield of 2.12 L/(g·h).
Abstract: Different kinds of rice husk (RH) char were prepared in an entrained flow reactor under reburning conditions. The physico-chemical properties of pyrolyzed RH chars were characterized by scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), specific surface area and pore size analyzer, X-ray diffraction (XRD) and Fourier transform infra-red (FT-IR) spectroscopy, respectively. The effects of temperature on evolution of physico-chemical structures of RH chars were discussed. The results indicate that the specific surface area and pore volume of RH chars increase significantly from 850 to 1 150 ℃. The order of release of alkaline and alkaline earth metals (AAEMs) bound in RH is Na > Ca > Mg > K. With increasing reaction temperature, release fractions of AAEMs generally increase firstly and then being stable, and the chlorine release fraction increases gradually. AAEMs in RH chars are mainly in the form of silicate and sulfate. The surface oxygen-containing functional groups in RH chars decrease significantly with increasing temperature.
Abstract: An amorphous NiB/SiO2-Al2O3 catalyst was prepared and characterized by XRD, TEM, N2 sorption and XPS. The catalytic performance of the prepared catalysts was evaluated in an oil-water bi-phase system using anisole and guaiacol as model compound of bio-oil. The results showed that Ni was in the electron-rich state with the modification of B, leading to the much higher hydrogenation activity of amorphous NiB/SiO2-Al2O3 catalyst than that of Ni/SiO2-Al2O3 catalyst. Increasing reaction temperature or prolonging reaction time was beneficial to the conversion of guaiacol and anisole. On the basis of the experimental results, the reaction pathway of guaiacol and anisole was analyzed, which provided a reference for the mechanism of bio oil hydrogenation.
Abstract: In this study, H3PW12O40 (Tungstophosphoric acid) was applied as matrix, and which was modified by La3+ through conventional impregnation method, ultrasonic impregnation method and sol-gel method, obtained three solid acid catalysts: A-LaPW12O40, B-LaPW12O40/SiO2 and C-LaPW12O40. These above catalysts were characterized by X-ray fluorescence spectrometer, specific surface area and porosity analyzer, X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectoscopy, thermogravimetric analysis, N2/adsorption-desorption, NH3 temperature programmed desorption, pyridine adsorption IR spectra and X-ray photoelectron spectroscopy. The catalytic activities and stabilities of them were compared when they were used for the catalytic synthesis of biodiesel from the esterification reaction of oleic acid and methanol. Results shown that the B-LaPW12O40/SiO2 has highest catalytic activity and stability: the conversion of oleic acid can be high to 93% when the molar ratio of methanol to oleic acid was 8:1, mass ratio of catalyst to reactants was 2%, reaction temperature was 65 ℃ and reaction time was 1 h; the conversion of oleic acid maintained 86.4% after B-LaPW12O40/SiO2 had been cycled six times. The high catalytic activity and stability of B-LaPW12O40/SiO2 can be explained as follows: a SiO2 network was formed from the hydrolytic action of Si(OC2H5)4 (TEOS) under acidic conditions via Sol-Gel process. The H+ of H3PW12O40 will bond with Si-OH in SiO2 network to form a (≡Si-OH2+)(H2PW12O40-) complex with strong electrostatic adsorption force, thus promoting the adsorption of La3+ on the surface of SiO2, greatly. As a result, the pore structure of H3PW12O40 will be blockaged, the grow up of H3PW12O40 particles in the roasting process also will be inhibited. In addition, SiO2 may be existed in the form of dry gel in the B-LaPW12O40/SiO2 catalyst and acted as carrier. It will be favorable for the improvent of the surface area of B-LaPW12O40/SiO2 since SiO2 has high surface area, so the surface area of B-LaPW12O40/SiO2 has increased from the 1.4 m2/g of H3PW12O40 to the 31.3 m2/g. And more, LaPW12O40/SiO2 has been determined from the Py-FTIR spectra of pyridine adsorption analysis, which is a Brönsted-Lewis solid acid. The formation of Lewis acid sites can help to reduce the deactivation of a solid acid catalyst: some H2O will be generated from the esterification reaction, and hydration will occur between Brönsted acid site and H2O, so the deactivation will occur. The formation of Lewis acid sites can be ascribed to the strong electrophilic action of La3+ after it has been bonded with (≡Si-OH2+)(H2PW12O40-) to form LaPW12O40/SiO2.
Abstract: Uniform ZSM-5 nanoparticles (around 180 nm) were synthesized by steam assisted crystallization method (SAC), which have a hierarchically porous structure, composed of abundant open mesopores from the stacking of ZSM-5 particles and micropores in the ZSM-5 crystallites. The hierarchical ZSM-5 supported cobalt catalyst, with a cobalt loading of 15%, was then prepared through incipient impregnation and used in Fischer-Tropsch synthesis (FTS). The hierarchical ZSM-5 support and Co-based catalyst were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 sorption. The results indicate that the hierarchical ZSM-5 supported cobalt catalyst performs excellently in FTS, since the mesoporous structure in the hierarchical ZSM-5 support can enhance the mass transfer of the reaction products and the acid sites on the microporous ZSM-5 framework can promote the hydrocracking of long chain hydrocarbon products. In comparison with the cobalt catalysts supported on bulk ZSM-5 and commercial ZSM-5, the hierarchical ZSM-5 supported cobalt catalyst exhibits much higher activity in FTS, lower selectivity to CH4, and higher selectivity to C5-20 hydrocarbons (68.9%).
Abstract: CO2 enhanced sorption methane steam reforming for hydrogen production is a potential approach to economically provide hydrogen and to reduce CO2 emission. The key point for this process is to develop a composite catalyst with high catalytic and adsorptive capacity. Considering the tunable structure of hydrotalcite-like compounds, co-precipitation method was employed to synthesize Ni/CaO-Al2O3 composite catalysts by varying the molar ratio of Ca to Al. The results show that the specific surface area and Ni dispersion of the as-synthesized composite catalysts are greatly influenced by molar ratio of Ca to Al, which derives from the variable interaction between Ni and the support. When the molar ratio of Ca to Al is 3, the composite catalyst obtains a specific surface area of 12.9 m2/g and Ni dispersion of 1.07%. Catalytic evaluation shows that the composite catalyst possesses a H2 concentration of 95% and a CH4 conversion of 88%, and H2 concentration exceeds 93% even after 10 cyclic runs.
Abstract: The MgO support was first synthesized by the solution method, with which the Pd/MgO nanocatalyst was then prepared by the impregnation method. The structure and performance of prepared catalyst were characterized by XRD, CO2-TPD, BET, TG, SEM, TEM and catalytic evaluation device. The research result shows that the synthesized MgO support consists of uniform nanosheets and strong Lewis basic sites. The active Pd nanoparticles of Pd/MgO catalyst are highly dispersed on the surface of MgO support with small and homogeneous size. Moreover, the Pd/MgO nanocatalyst with a low Pd loading (0.5%) exhibits an excellent catalytic performance with 65% CO conversion, 96% selectivity to DMO and more than 100 h on stream at 130 ℃. for CO oxidative coupling to dimethyl oxalate, much higher than industrial catalyst (Pd/α-Al2O3), which has a good prospect of industrial application.
Abstract: A series of ZnFe-LDHs were prepared via microwave-assisted co-precipitation method based on the structural properties of layered double hydroxides (LDHs) and the advantages of microwave-assisted synthesis and used for oxidative dehydrogenation of isopentene. The H2O/C5H10 molar ratio was lowered due to the easily hydroxylic surface. The results indicate that the microwave method can significantly shorten the synthesis time. ZnFe-LDHs with high crystallinity and purity were obtained at the microwave power of 600 W, microwave temperature of 95 ℃ and microwave time of 1 h. Compared with conventional method, the ZnFe-LDHs catalysts prepared with microwave method generated precursors exhibited higher activity and selectivity in oxidative dehydrogenation of isopentene. 52% yield of isoprene and 83% selectivity were achieved when the H2O/C5H10 molar ratio was 5.7, which was greatly lowered.
Abstract: SiO2, siliceous MCM-41 (Si-MCM-41), physical mixture of Si-MCM-41 and ZSM-5 (Z-MCM-41-M), and Z-MCM-41 composite obtained by coating MCM-41 on ZSM-5 zeolite particles were prepared and characterized by XRD, HRTEM, N2 adsorption-desorption and NH3-TPD. The performances of the supported Pd catalysts in hydrodesulfurization (HDS) were evaluated in a fixed-bed reactor with dibenzothiophene (DBT) as the model sulfur-containing molecule; the effect of support properties on the performance of supported Pd catalysts in HDS was then investigated. The results indicated that the performance in HDS of supported Pd catalysts are significantly influenced by the support properties. Although the specific surface has a minor influence on the HDS activity of the supported Pd catalysts, the hydrogenation (HYD) selectivity is probably related to the pore structure of support; the mesoporous structure is beneficial to the improvement of HYD selectivity. The acid supports can give the Pd catalysts higher HDS activity, owing to the hydrogen spillover effect. The Z-MCM-41 composite is an excellent support for noble metal Pd catalyst in HDS, which can be ascribed to the synergy of the mesoporous structure of MCM-41 and acidic properties of ZSM-5.
Abstract: A series of CeWTiOx catalysts were prepared by self-propagating high-temperature synthesis method, and their NH3-SCR activities were evaluated. X-ray diffraction, N2 adsorption-desorption, H2-temperature-programmed reduction, X-ray photoelectron spectroscopy and NH3-temperature-programmed desorption were performed to investigate the relationship between the catalyst activity and its physicochemical properties such as crystalline phase, specific surface area, redox ability and acidity. The results showed that 80% of NO conversion could be reached on the Ce40W10TiOx catalyst sample in a range of 150-430 ℃. NO conversion of Ce40W10TiOx could be kept above 97% in SO2 atmosphere. The characterization indicated that the excellent low temperature activity and SO2 resistance of Ce40W10TiOx were mainly associated with the tungsten doping. The existence of tungsten weakened the strength of Ce-O bond, lowered the crystallinity and crystal size of CeO2, increased the surface active oxygen content and the acid sites, thus improved the NH3-SCR performance of the catalyst.
Abstract: MnOx/TiO2 catalysts were prepared by spontaneous deposition, co-precipitation and impregnation methods, respectively. The structure and properties of the MnOx/TiO2 catalysts were studied by means of XRD, TEM, N2 adsorption-desorption, XPS, H2-TPR and NH3-TPD. The activity of the catalysts in the selective catalytic reduction of NO was investigated. The results showed that the MnOx/TiO2(s) catalyst prepared by the spontaneous deposition method had a completely amorphous structure and a strong interaction between Mn and Ti, showed stronger redox ability than other two catalysts. In addition, the MnOx/TiO2(s) catalyst exhibited larger surface area, more surface acid sites, which were beneficial to NH3 adsorption and activation, as well as the high Mn4+ and adsorbed oxygen content of catalyst surface, which could greatly enhance the activity for NO oxidation to NO2, as a result, facilitating the "fast-SCR" reaction. Thus, a superior denitrification activity was exhibited over MnOx/TiO2(s) catalyst. For MnOx/TiO2(s) catalyst, the conversion of NO reached 92.8% at 150 ℃ and retained over 90% in the range of 150-350 ℃. Moreover, the MnOx/TiO2(s) catalyst also showed strong resistance to H2O and SO2 poisoning.
Abstract: MoS2/TiO2 nanocomposites was prepared by mixing MoS2 with hydrothermally synthesized TiO2; the effects of MoS2 loading on the photocatalytic performance of MoS2/TiO2 in phenol degradation were investigated. The XRD, SEM, EDS, FT-IR and UV-vis DRS characterization results show that for the MoS2/TiO2 nanocomposites, lamellar MoS2 is uniformly dispersed around the TiO2 nanoparticles. The increase of MoS2 loading is beneficial to the photocatalytic degradation of phenol; with a MoS2 loading of 27%, the MoS2/TiO2 nanoparticles exhibited the highest photocatalytic activity, over which phenol can be completely degraded in 80 min. The intermediates during reaction are further tracked to investigate the reaction kinetics of photodegradation of phenol over MoS2/TiO2 nanocomposties. The results reveal that an increase in MoS2 loading is able to promote the formation of various intermediates such as benzoquinone, hydroquinone and catechol, which can further enhance the overall photodegradation efficiency.
Abstract: The mercury emission characteristics are investigated and compared at a coal-fired power plant with 330 MW pulverized coal (PC) boiler and a coal-fired power plant with 350 MW circulating fluidized bed (CFB) boiler. EPA 30B method and Ontario method were used to test the mercury concentration in flue gas at the inlet of dust extraction unit, outlet of dust extraction unit, outlet of desulfurization unit, and outlet of wet dust extraction unit. The feed coal, bottom ash, fly ash and gypsum sample were collected at the same time together with gas sampling. The effect of the existing air pollution control device on mercury control was discussed toward PC and CFB units based on the mercury distribution data. The results show that the mercury concentration at fabric filter (FF) outlet of CFB power plant is decreased to 0.43 μg/m3 and the mercury removal efficiency of FF reaches 98.9%. A predominating portion of mercury is enriched in fly ash. With respect to a PC power plant, the mercury concentrations at inlet and outlet of ESP are both higher than those in the CFB power plant, and the mercury concentration gradually drops from electrostatic precipitator (ESP) inlet to wet flue gas desulfurization (WFGD) outlet. The mercury concentration reaches a low value of 0.42 μg/m3 at the WFGD outlet, and the mercury removal efficiency of ESP and WFGD is 75.0% and 22.4%, respectively, which can meet the ultra low mercury emission controlling.
Abstract: The oxidation activity of elemental mercury (Hg0) by transition metal modified KIT-6 was investigated using a simulated element mercury (Hg0) adsorption reactor. The physical and chemical propertied of the catalysts were characterized by scanning electron microscope (SEM), N2 adsorption-desorption (BET), Fourier Transform Infrared spectroscopy (FT-IR) Analysis, H2-Temperature programmed reduction (H2-TPR), thermogravimetric analysis (TGA). The results show that Ce-Co/KIT-6 surface area and total pore volume of the catalysts decrease after the modification. However, the pore structure and distribution after modification have little variation. The mean pore size and BET surface area of mesoporous Ce-Co/KIT-6 are 4.6 nm and 495.2 m2/g, respectively. The Ce-Co/KIT-6 shows a high Hg0 adsorption efficiency without O2, the removal efficiency of Hg0 is about 50.67%; moreover, it has a high Hg0 removal efficiency of O2 above 95% for 250 ℃, the presence of O2 greatly contributes to mercury removal capacity of the catalyst. Oxygen enters the metal structure through changes in the valence state of Ce-Co and reacts with mercury, which may be the main mechanism of this process.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
