Abstract: The gasification reactivity and crystallite structure of Shenfu char were measured via thermogravimetric analysis (TGA) and X-ray diffraction technology (XRD) to investigate the catalytic effect of AAEM during CO2 gasification. The interest was focused on effects of loading method (pyrolysis before loading or pyrolysis after loading), catalyst species (Na, K, Ca) and loading amount (1%, 3%, 5% on metal atom). For Na and K, the reactivity of char pyrolyzed before loading catalyst is better than that pyrolyzed after loading. The order of catalytic efficiency is Na~K >Ca. In addition, catalytic efficiency of AAEM catalyst increases with the increasing of loading amount. Catalyst addition inhibits the progress of char graphitizing during pyrolysis. The order of inhibition is K > Na > Ca, and the inhibition is enhanced with the increase of loading amount.
Abstract: In order to integratedly utilize the relatively rich coal resource of Zhaotong mine, temperature-programmed pyrolysis experiments of Zhaotong lignite were performed in fixed bed reactor at different temperatures. The resultant coal tar and char were characterized by GC-MS and Raman Spectroscopy, respectively. Char-H2O isothermal gasification characteristics were evaluated in fixed bed reactor at 850℃. The results show that in pyrolysis at 700℃ the cumulative content of H2, CO and CH4 in gases accounts for about 70%, and the growth rate of low calorific value of gas is the fastest, which is 90% based on the value at 500℃. A large number of phenolic compounds are generated at 500-700℃. Above 700℃ the decomposition reactions of the phenolic compounds is intensified. With the increase of pyrolysis temperatures, the apparent reaction rate of char decreases, while the molar ratio of CO2 and CO increases. The molar ratio of H2 and CO in gasification from char pyrolyzed at 700℃ was the highest.
Abstract: Six possible reaction pathways for the thermal degradation of 4-O-methyl-glucuronic acid as a hemicellulose model compound were proposed; the reactants, products, intermediates and trasistion states involved in these reaction pathways were structurally optimized and the related standard kinetic parameters were calculated. The results show that for the thermal degradation of the hemicellulose model compound, 4-O-methyl-glucuronic acid is first converted to catenulate intermediate through a ring-opening reaction with a intramolecular hydrogen transfer, the intermediate is then decomposed, with methanol, glycolaldehyde, 2-hydroxy-3-methoxy-butyl aldehyde acid, glyoxal, 2-hydroxy-butyl aldehyde acid and so on as the major products; the competitive degradation products are formic acid, CO2, CO, 4-hydroxy-3-vinylmethylketone, methoxyethene and so on. During the thermal degradation of hemicellulose, CO2 is likely formed through decarboxylation of unsaturated reactants or intermediates, whereas acetic acid is probably produced through the elimination of O-acetyl.
Abstract: The CaO@SiO2 alkaline catalyst was prepared by sol-gel method that chooses polystyrene as hard template and P123 as soft template to control the microstructure. Furthermore, the prepared catalyst was applied to the transesterification of soybean and methanol. Also, the nano-solid based catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), CO2-TPD and N2 absorption-desorption (BET). The results show that the catalyst possesses an ordered morphology and core-shell structure. In addition, the effect of the ratio of SiO2/CaO (mass ratio), reaction temperatures, catalyst dosages and the ratio of oil/methanol (mol ratio) on the yield of biodiesel was examined. Under the best reaction condition, the yield of biodiesel can reach 95.6%.
Abstract: The raw multi-walled carbon nanotubes (MWCNTs) were treated with nitric acid. The shift of the surface functional groups on the MWCNTs was observed with XPS. The Pd/MWCNTs catalysts were synthesized by the ultrasonic impregnation method. The total contents of oxygen, hydroxyl and carbonyl groups were measured. The dispersion and size distribution of Pd particles were characterized with TEM. The dependence of Pd dispersion on the oxygen-containing functional groups was validated. The effect of pretreatment on the catalytic activity and stability for methane combustion was investigated under lean fuel conditions. It is shown that the catalytic activity depends on the valence state and particle size of palladium. The transformation from Pd to PdO possibly caused the decrease in the catalytic activity. Another factor inducing deactivation is Pd particle aggregation. The reaction mechanism for methane combustion over the Pd/MWCNTs catalyst is postulated on the basis of the intermediate species detected by in-situ FT-IR spectroscopy.
Abstract: BiOBr, BiOBr/Graphene and Au/BiOBr/Graphene composites were prepared by hydrothermal synthesis and dopamine in-situ reduction method; their morphology, composition, phase structure and optical absorption properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflection spectroscopy (DRS) and photoluminescence (PL) emission spectroscopy. The photocatalytic performance of Au/BiOBr/Graphene in phenol degradation under visible light was investigated. The results indicate that the Au/BiOBr/Graphene composite exhibits enhanced absorption in the visible light region as well as superior photocatalytic activity in the degradation of aqueous phenol, in comparison with BiOBr and BiOBr/Graphene, owing to the enhanced quantum efficiency, narrowed band gap (2.25eV) and surface plasmon resonance of Au nano particles. Over Au/BiOBr/Graphene composite, the degradation rate of phenol reaches 64% in 180min under visible light irradiation.
Abstract: In this work, the impact of CeOx doping on a TiO2-SiO2 supporter on the Ag based adsorptive desulfurization for Chinese standard diesel was studied. The dispersion and valence states of Ce, Ti and Ag species were characterized, and the impact of Ce doping was investigated. The results indicated that Ce species and Ti species were dispersed evenly on the surface of SiO2 via a novel co-impregnation method. Following CeOx doping, the Ag species were in the form of oxides (about 5nm) instead of metallic Ag particles (about 35nm), which is due to the large amount of coordinative unsaturated sites provided by the interaction between CeOx and TiO2, as well as the oxidation-reduction property of CeOx. The Ag in the active oxide state (Ag2O2) and dispersed evenly on the supporter could interact with sulfur compounds more favorably, and therefore showed a good performance in the adsorptive desulfurization. In both static batch and dynamic breakthrough desulfurization tests, Ag-CeOx/TiO2-SiO2 was proved to be a more efficient adsorbent compared with Ag-TiO2-SiO2. It was found that the desulfurization performance of Ag-TiO2-SiO2 exhibited an excellent improvement (22.5%) after being doped with CeOx. In the static equilibrium tests, the equilibrium sulfur capacity of Ag-CeOx/TiO2-SiO2 was up to 5.38mg/g for CN-II diesel (sulfur content 952.9mg/kg) and the sulfur content of the CN-IV diesel (sulfur content 39.0mg/kg) after desulfurization was less than 10mg/kg, which could meet the CN-V standard.
Abstract: Amorphous CeO2@TiO2 catalyst was prepared by spontaneous deposition method and characterized by XRD, Raman spectra, TEM, N2 physisorption, H2-TPR, NH3-TPD and FT-IR; its performance in the selective catalytic reduction (SCR) of NO with NH3 was investigated. The results show that there is a strong interaction between Ce and Ti which are combined at atomic level. In comparison with the crystal CeO2/TiO2 catalyst prepared by impregnation, the amorphous CeO2@TiO2 catalyst exhibits larger surface area and pore volume, excellent redox ability and acidity, and outstanding catalytic performance in SCR. Over the CeO2@TiO2 catalyst, the conversion of NO reaches 80% at 175℃ and retains 96.0%-99.4% at 200-400℃. Moreover, the amorphous CeO2@TiO2 catalyst also shows strong resistance to H2O and SO2 poisoning.
Abstract: The behaviors of thiophene adsorption and hydrodesulfurization on cubic octahedral M13 (M=Au, Pt) clusters were investigated by density functional theory. The results show that the adsorption energy of thiophene on Pt13 is higher than that on Au13; on the Au13 cluster, the Hol-tri site is most stable for the thiophene adsorption with ring, whereas on the Pt13 cluster, the Hol-quadr site is most stable. By the indirect desulfurization mechanism, the desulfurization is achieved probably via the cis-hydrogenation; the removal of C-S is the rate-determining step. By the direct desulfurization mechanism, the HS hydrogenation turns to be the rate-determining step. The desulfurization is most likely via the direct desulfurization mechanism, which exhibits much lower activation energy than the indirect desulfurization mechanism. The energy change for thiophene desulfurization on the Au13 cluster is exothermic, whereas on the Pt13 cluster it is endothermic; as a result, the hydrodesulfurization on Au13 is much easier than that on Pt13.
Abstract: The supported Ni2P/Ti-MCM-41 catalyst is prepared by temperature-programmed reduction method with nickel chloride (NiCl2·6H2O) as the nickel precursor, ammonium hypophosphite (NH4H2PO2) as the phosphorus precursor and Ti-MCM-41 as the support. The Ni2P/Ti-MCM-41 catalyst was characterized by H2-TPR, XRD, BET, XPS, and TEM; the effect of reduction temperature on its catalytic performance in hydrodesulfurization (HDS) was investigated by using dibenzothiophene (DBT) as a model compound. The results show that the precursors on the catalyst prepared in this way can be reduced at 318℃, which is at least 200℃ lower than that prepared by traditional methods. Pure Ni2P phase can be obtained by reduction at 350-500℃; the low reduction temperature is in favor of forming small Ni2 Pcrystallite size. The Ni2P/Ti-MCM-41 catalyst obtained at a reduction temperature of 400℃ exhibits the highest surface area, the best dispersion of Ni2P crystallite size, the lowest surface phosphorus content and the highest HDS activity; under 340℃, 3.0MPa, a H2/oil ratio of 500 (volume ratio) and a weight hourly space velocity (WHSV) of 2.0h-1, the conversion of DBT for HDS reaches 99.4%.
Abstract: NO reduction by propene with iron was experimentally studied. NO reduction efficiency at different conditions was tested in a flow-type ceramic tube reactor at 300-1100℃. The effect of SO2 was also investigated. XRD, SEM and EDS techniques were used to analyze the composition and surface microstructure of the iron sample after reaction. Results showed that propene was effective to reduce NO with iron. More than 95% of NO was reduced above 800℃ in N2 atmosphere and more than 90% of NO was reduced above 900℃ at fuel-rich conditions in simulated flue gas atmosphere by propene with iron respectively. SO2 had minor effect on NO reduction. The analysis on reaction mechanism showed that when propene was used to reduce NO with iron, on one hand, NO was directly reduced by iron while propene reduced the iron oxides to iron; on the other hand, propene reduced NO via reburning reaction while the re-burning intermediates were oxidized by iron.
Abstract: The methanation of synthesis gas is the key process of coal to natural gas. Considering the existence of CO2 in the synthesis gas, it is important to investigate the influence of CO2 on the sulfur-resistant methanation. In this paper, the effect of CO2 on methanation activity of Mo-based catalysts was investigated at the reaction temperature of 550℃ and the gas space velocity of 5000h-1 with the syngas containing 1.2% H2S (volume ratio). The results show that the promoter Co and the cerium-aluminum composite support can improve the stability of the catalyst and reduce the deactivation. The CO2 is proved to promote the reverse water gas shift reaction, which would inhibit the activity of MoO3/Al2O3 catalyst more heavily than MoO3-CoO/CeO2-Al2O3 catalyst. When the CO2 adding to the inlet gas is less than 10% for 20h, the catalyst activity could be restored to its original activity after stopping the addition of CO2. However, as the added CO2 in inlet gas is over 10%, more H2O will be generated through reverse water gas shift reaction to damage the catalyst structure and decrease the active component, resulting in an irreversible loss of catalyst activity.
Abstract: Ni-Fe/montmorillonite (MMT) catalysts were prepared by impregnation method for hydrogen production via ethanol steam reforming. The catalysts were characterized by XRD, H2-TPR, and N2 adsorption-desorption. It was found that Ni-Fe bimetallic catalysts exhibited higher activities and stability than single metallic catalysts due to the well dispersed Ni-Fe, small nickel crystallites and stronger interaction between Ni2+ and carrier. The conversion and selectivity were affected by the ratio of Ni to Fe. The 10Ni5Fe/MMT catalyst showed the optimum catalytic performance, its ethanol conversion was 100%, the selectivity of hydrogen gas remained at 72%, and selectivity of CO and CH4 were significantly decreased at 500℃ during 30h testing. This could be attributed to the promoter Fe, which improves the dispersion of Ni and results in a good ESR activity at low reaction temperature. Small Ni particles can suppress methane formation and Fe addition can enhance the methane reforming with water and water gas shift reaction, resulting in higher selectivity of hydrogen.
Abstract: Silicalite-1 zeolite hollow sphere structured material was hydrothermally synthesized via the aid of carbon microspheres as hard-template. The morphology, structure, textural and physicochemical properties of the material were characterized with XRD, SEM, FT-IR, N2 adsorption-desorption isotherm, 29Si MAS NMR, TG, and XPS techniques. It was suggested that the obtained Silicalite-1 hollow spheres were highly crystallized with developed multiple channel structure and abundant surface hydroxyl groups, which endowed the material with excellent catalytic properties in Beckmann rearrangement reaction of cyclohexanone-oxime. Compared with the Silicalite-1 catalyst prepared from conventional method, the Silicalite-1 hollow sphere catalyst showed much higher activity to the conversion of cyclohexanone-oxime (99%) and selectivity of caprolactam (94%), with excellent stability at the same time. The abundant nest silanols and terminal silanols in Silicalite-1 hollow sphere were main active sites for Beckmann rearrangement reaction, and could be easily recovered from the deactivated catalysts by calcination.
Abstract: The ZSM-22 molecular sieves with various morphologies were synthesized by different methods. XRD, SEM, BET, MAS NMR, NH3-TPD and Py-FTIR were used to study the structure, morphology, surface area, Si-Al coordination and acidity of the samples. Furthermore, the toluene-methanol alkylation as probe reaction was used to investigate the effect of ZSM-22 zeolites morphology on catalytic performance. The lattice parameters, surface areas, Si-Al coordination and acidity of all samples are obviously different. As a result, the interaction of each bundle of the bundle-like ZSM-22 zeolites leads to the structure change of Si (4Si) coordination, the increase of T3 and T4 with decrease of T2 location, and thus displays more L acid sites. At 380℃ reaction temperature, the bundle-like ZSM-22 zeolite catalyst shows high selectivity to p-xylene (76.1%) at about 16.7% conversion in the toluene-methanol alkylation.
Abstract: A series of hydrotalcite-like Ti/Li/Al-LDHs materials were prepared by co-precipitation method and characterized by atomic absorption spectrophotometer (AAS), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TG) and Fourier transform infrared (FT-IR); the influence of metal composition and calcination temperature on the structure, morphology and CO2 adsorption capacity of Ti/Li/Al-LDHs was investigated. The results showed that Ti1Li3Al4-LDHs obtained with a Ti/Li/Al ratio of 1:3:4 displays the highest crystallinity and regular morphology, whereas Ti1Li3Al2-LDHs300 prepared with a Ti/Li/Al ratio of 1:3:2 and calcined at 300℃ exhibits the best adsorption performance towards CO2. The CO2 adsorption capacity over Ti1Li3Al2-LDHs300 reaches 53.5mg/g; in addition, the adsorption capacity is only decreased by 2.4% after adsorption for 10 cycles.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
