Abstract: The char samples were prepared from the coal impregnated with NaCl under different steam concentrations and temperatures. The mode of occurrence of sodium and the contents of sodium in different chars with the same conversion ratio were analyzed by inductively coupled plasma mass spectrometry. The effects of steam and temperature on the migration and transformation of sodium in the coal during the thermal conversion processes were studied. The results showed that the increase of steam concentration enhanced the release of water-soluble sodium during the thermal conversion of coal and promoted the transformation of water-soluble sodium into ammonium acetate, hydrochloric acid and insoluble sodium. As a result, the release of sodium was suppressed to a certain extent. It was also observed that increasing the reaction temperature could promote the release of water-soluble sodium and promote the transformation of water-soluble sodium to the other soluble forms of sodium. The evolution of char structure was an important influence on the release of sodium. The results revealed that the degrees of char condensation increased with the steam gasification reaction. The formation of large aromatic ring structures from the condensation of the small aromatic rings played the important role in the encapsulation of sodium, which would inhibit the release of sodium.
Abstract: The occurrence forms of organic nitrogen in Xianfeng lignite (XL), Xiaolongtan lignite (XLT) and Shengli lignite (SL) as well as their extraction residues were characterized by X-ray photoelectron spectroscopy (XPS). The results show that the content distributions of organic nitrogen in the three extraction residues are different, but all are mainly dominated by pyrrole nitrogen. The NaOH-catalyzed supercritical methanolysis of lignite extraction residues at 300℃ was then investigated, which indicates that the yields of petroleum ether soluble portions from supercritical methanolysis of extraction residues derived from XL, XLT and SL are 46.0%, 43.8%, and 47.6% (mass ratio), respectively. The characterization of nitrogen-containing compounds (NCCs) in petroleum ether soluble portions by Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS) indicates that NCCs are mainly composed of N1, N1O1-N1O5, N2, N2O1-N2O4, N3O2 and N5O2-N5O4 class species. The molecular structural characteristics of NCCs were speculated according to the distributions of double bond equivalent values and carbon numbers, which shows that most of NCCs contain oxygen-functional groups like hydroxyl and carboxyl groups, and the nitrogen atoms are mainly present in aromatic structures (mainly 1-3 aromatic rings) in the forms of pyrrolic, pyridinic and amino groups. The cleavage of C-O bridged bonds in lignite is an important pathway for producing NCCs.
Abstract: In this paper, the citric acid method was used to prepare the Co-doped iron-based oxide sorbent. The mercury removal performance of the FeCo sorbent was investigated by a fixed-bed mercury removal experimental device system, and the characterization methods of the specific surface area (BET), X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), Fourier infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) were performed to analyze the physical and chemical characteristics of the sorbent. The results of the study indicate that the specific surface area and pore structure characteristics are improved after the addition of Co into α -Fe2O3, and the redox performance of α -Fe2O3 is also improved. The maximum mercury removal efficiency of FeCo sorbent is obtained at 200-250 ℃ at the value of about 97%. The presence of O2 and NO in the gas benefits the removal of Hg0 over FeCo sorbent, while SO2 and H2O inhibit the removal of Hg0 over FeCo sorbent. The presence of NO can weaken the inhibitory effect of SO2 on mercury removal performance over FeCo. During the mercury removal process, the active components Fe3+, Co3+, and O* on the surface of the FeCo sorbent are consumed, particitate in the Hg0 oxidation process, and HgO is formed on the surface of the sorbent. After the mercury removal reaction in the atmosphere containing SO2, the sulfation of the sorbent surface is occurred, which weakens the mercury removal performance of the adsorbent.
Abstract: The influence of dolomite as an additive on the slagging and potassium fixation characteristics of rice straw upon burning was investigated in a tube furnace; the slagging mechanism as well as the interaction between the rice straw ash and dolomite were explored by using the inductively coupled plasma optical emission spectrometry (ICP-OES) and X-ray diffraction (XRD). The results show that the slagging characteristics of rice straw are significantly influenced by adding 5% dolomite. Dolomite can greatly improve the potassium fixation ability, especially at 900-1000℃; moreover, the Mg and Ca elements rich in dolomite can react with SiO2 in the rice straw ash, forming high-melting silicate minerals including diopside, monticellite and merwinite.
Abstract: A series of nitrogen-doped carbon nanotubes (xN-CNTs) were obtained by treating the mixture of melamine and carbon nanotubes at high temperature; the CuCoCe catalysts supported on xN-CNTs were then prepared by impregnation method and used in the synthesis of higher alcohols from syngas. The CuCoCe/xN-CNTs catalysts were characterized by XRD, N2 sorption, H2-TPR, NH3-TPD and XPS and the effect of nitrogen content in xN-CNTs on the catalytic performance of CuCoCe/xN-CNTs in the higher alcohols synthesis was investigated. The results show that the content of nitrogen in xN-CNTs has a significant influence on the existence and dispersion of Cu on the CuCoCe/xN-CNTs catalysts; the presence of nitrogen can reduce the number of reducible Co species and lower the acid strength and amount on the catalyst surface, which helps to suppress the long-chain hydrocarbons formation and improve total alcohol selectivity. It is proposed that the morphological distribution and doping amount of nitrogen on the carbon tubes may play a crucial role in enhancing the catalytic performance of CuCoCe/xN-CNTs in the higher alcohols synthesis.
Abstract: Polyimide (PI) modified Fe3O4@PI and Fe3O4-PI catalyst samples were prepared by hydrothermal-coating and ball milling methods, respectively. The effect of PI modification on the product distribution of the Fe-based catalysts for Fischer-Tropsch synthesis was investigated. The catalysts were characterized by XRD, SEM, TEM, H2-TPR, CO-TPD, FT-IR, XPS, TG and contact angle measurements. The results showed that Fe3O4, Fe3O4@PI and Fe3O4-PI were spherical with uniform particle size, and the Fe3O4@PI particle size was smaller. PI modification promoted the reduction and the hydrophilicity of Fe3O4. For Fe3O4@PI sample, PI was uniformly coated on Fe3O4 surface, which led to good thermal stability. Compared with Fe3O4 and Fe3O4-PI samples, CO adsorption was promoted on Fe3O4@PI. Compared with Fe3O4, the catalytic activity of Fe3O4@PI and Fe3O4-PI decreased, and the secondary hydrogenation ability was inhibited, resulting in increase of olefin selectivity. For Fe3O4@PI, the olefin selectivity was enhanced significantly with olefin to alkane ratio in C2-4 fraction increased from 0.50 to 2.15. PI modification with suitable content favored the formation of C5+ hydrocarbons.
Abstract: HZSM-5 zeolite was synthesized under hydrothermal condition with TEOS as silicon source and glycerin as auxiliary agent. The effects of glycerol addition and crystallization time on the grain size, relative crystallinity and acidity of HZSM-5 molecular sieves and their catalytic performance for anaerobic aromatization of methane were investigated. XRD, SEM, NH3-TPD and other analytical methods were used to characterize the HZSM-5 molecular sieve samples synthesized under different conditions. The results show that the relative crystallinity of HZSM-5 molecular sieve can be increased through adding certain amount of glycerol adjuvant and adjusting the crystallization time, meanwhile, the formation of amorphous SiO2 can be suppressed and the acid content can be increased. The HZSM-5 prepared with glycerol assistance shows excellent catalytic performance in methane anaerobic aromatization. Compared with the HZSM-5 catalyst synthesized without the addition of glycerin, the methane conversion rate, benzene selectivity and aromatic selectivity are all greatly improved, and it has better stability and resistance to carbon deposition.
Abstract: A series of MTiO3 (M=Mg, Ca, Sr, Ba) supported Ni catalysts (with a Ni loading of 5%) for methane reforming with carbon dioxide (DRM) were prepared by the impregnation method. The Ni/MTiO3 catalysts were characterized by XRD, N2 sorption, H2-TPR, CO2-TPD, XPS and TG; the effect of alkaline earth metals (M) on the catalytic performance of Ni/MTiO3 in the DRM was then investigated. The results indicate that the metal-support interaction, the surface Ni atomic concentration and the mobility of lattice oxygen species on the Ni/MTiO3 catalysts are related to the alkaline earth metal M used in the MTiO3 supports. The Ni/CaTiO3 catalyst shows superior performance in DRM to other catalysts, which is ascribed to the strong metal-support interaction, large amount of reduced active Ni and relatively high mobility of lattice oxygen species. In contrast, the SrTiO3 support has a relatively large particle size, leading to poor Ni dispersion on the Ni/SrTiO3 catalyst as well as weak metal-support interaction, low lattice oxygen mobility, and less surface active Ni atoms; as a result, the Ni/SrTiO3 catalyst exhibits relatively poor performance in DRM.
Abstract: Ni2P/SiO2 catalysts were prepared by temperature-programmed reduction method and hypophosphite disproportionation method to investigate their naphthalene hydrogenation performance. The prepared catalysts were characterized by ICP-OES, X-ray diffraction, H2 temperature-programmed reduction, N2 adsorption-desorption method and transmission electron microscopy, etc. Results showed that Ni2P/SiO2 catalyst with pure Ni2P crystal phase could be successfully prepared by the temperature-programmed reduction method and hypophosphite disproportionation method. When the naphthalene hydrogenation reaction was performed at 340℃, 4 MPa, H2/oil volume ratio of 600, and a weight hourly space velocity (WHSV) of 20.8 h-1, Ni2P/SiO2 catalyst prepared by the temperature-programmed reduction method possessed superior hydrogenation activity. This result was ascribed to the advantages of temperature-programmed reduction method. It not only installed the higher number of Ni2P species (CO adsorption amount 21.6 μmol/g) over SiO2, but also obtained more weak acid sites on the catalyst surface, which promoted the adsorption of aromatic hydrocarbons and subsequently resulted in the higher hydrogenation activity. Furthermore, when the temperature-programmed reduction method was used to prepare Ni2P/SiO2 catalyst, the lower Ni/P molar ratio was more beneficial to enhance the naphthalene hydrogenation activity of the as-prepared catalyst.
Abstract: CeO2 support was synthesized by precipitation method and used to prepare CuO/CeO2 catalyst using impregnation method. The effects of cerium sources (Ce(NO3)3·6H2O, CeCl3·6H2O, Ce(NH4)2(NO3)6 and Ce(SO4)2·4H2O) on the catalytic performance of CuO/CeO2 catalyst were investigated. XRD, SEM, N2O titration, BET and H2-TPR were used to study the structure and properties of the catalysts. The CuO/CeO2 catalysts with different cerium sources have obvious differences in Cu specific surface area, reduction performance and interaction between active component and support. Moreover, CuO/CeO2 catalyst prepared with Ce(NO3)3·6H2O has large Cu specific surface area, low reduction temperature and strong interaction between CeO2 support and CuO and shows better catalytic activity in methanol steam reforming. The methanol conversion is 100% at reaction temperature of 553 K, water/methanol ratio in feed of 1.2 and methanol water gas hourly space velocity of 1760 h-1. Besides, the CO molar content in reformed gas is 0.84%.
Abstract: The physicochemical properties of the prepared bimetallic NiFe/γ-Al2O3 catalysts can be affected by reduction temperature, which can change the hydrogenation activity and product selectivity for methyl laurate catalytic hydrogenation. The metal Ni active sites mainly promote the decarbonylation/decarboxylation (DCO/DCO2) reaction, and the addition of Fe can promote the hydrodeoxygenation (HDO) reaction of methyl laurate to produce C12 alkanes. The results of H2-TPR, XRD, H2-TPD and BET indicate that high reduction temperature is beneficial to the formation of metal or alloy active centers. The hydrogenation activity of bimetallic catalysts depends on the content of metal Ni, Fe and NiFe alloy. The ability of NiFe bimetallic catalyst to adsorb and activate H2 is obviously affected by reduction temperature. In the studied temperature range, Ni active centers have excellent hydrogenation and cracking performances, and the introduction of Fe species can effectively inhibit the cracking performance. The sequence of catalytic hydrogenation activity for these bimetallic catalysts is:NF420 > NF360 > NF450 > NF300. When the reduction temperature is 420℃, the prepared NF420 catalyst owns the best catalytic hydrogenation performances. The conversion of methyl laurate and the selectivity of alkanes are 93.3% and 90.0% at the reaction temperature of 380℃, respectively.
Abstract: A series of Mg-modified Co/MgO/γ-Al2O3-TiO2 catalysts were prepared by multi-step impregnation method and characterized by X-ray diffraction (XRD), diffuse reflectance visible ultra violet spectroscopy (DR-UV-vis), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS) and H2 temperature-programmed reduction (H2-TPR); the effect of Mg modification on the catalytic performance of Co/MgO/γ-Al2O3-TiO2 in the combustion of propane was investigated. The results indicate that Co exists in the form of Co3O4 on both the pristine γ-Al2O3-TiO2 and Mg-modified MgO/γ-Al2O3-TiO2 supports; Mg added in the MgO/γ-Al2O3-TiO2 support interacts with Al2O3, forming MgAl2O4 spinel, which can improve the textural properties and promote the dispersion of Co3O4. Moreover, the interaction between MgAl2O4 and Co3O4 can increase the proportions of Co3+/Co2+ and Oads/Olatt on the catalyst surface, weaken the Co-O bond, and thereby enhance the activity of Co-based catalyst in propane combustion. For the propane combustion over the Co/MgO(15%)/γ-Al2O3-TiO2 catalyst with an Mg loading of 15%, the temperature to achieve a propane conversion of 90% is decreased by 45℃ in comparison with that over the Mg-free Co/γ-Al2O3-TiO2 catalyst; moreover, the Co/MgO(15%)/γ-Al2O3-TiO2 catalyst exhibits excellent stability and no decrease in the activity is observed in a 40 h continuous reaction test for propane combustion.
Abstract: A sulfonic polymer-based catalyst (PDS-1.0) was synthesized by the hydrothermal and in situ sulfonation method, which is further modified by grafting with CF3SO3H, to get the PDS-1.0-F catalyst. The physical and chemical properties of the PDS-1.0 and PDS-1.0-F catalysts were characterized by N2 sorption, TG, FT-IR, 31P MAS NMR and XPS; the effect of CF3SO3H modification on the catalytic performance of PDS-1.0-F in the carbonylation of formaldehyde to glycolic acid was then investigated. The results show that after the CF3SO3H modification, the framework of PDS-1.0-F catalyst was grafted with strong electron withdrawing groups. In comparison with PDS-1.0, the CF3SO3H-modified PDS-1.0-F catalyst has a lower surface area, pore volume and concentration of acid sites, but much stronger acidity and higher thermal stability. As a result, the PDS-1.0-F catalyst exhibits excellent performance in the carbonylation of formaldehyde and over it the yield of glycolic acid reaches 91.2%.
Abstract: The effects of silicon source on the synthesis and physicochemical properties of MCM-22 zeolite were studied by using silica sol, fumed silica, silicic acid and silica gel as synthesis materials under dynamic hydrothermal conditions. MCM-22 zeolite with high crytallinity and purity was synthesized by using silica sol, silica, silicic acid and silica gel as silicon sources. The average sizes of zeolite particle are 190, 220 and 750 nm, respectively. Three silicon sources can affect the aggregate morphology of the zeolites, which are grain dispersion, grain semi dispersion and grain aggregation. The distribution of acid strength of the three groups of samples are almost same, all of them have more medium and strong acidity, and the total acid content of zeolite synthesized by fumed silica is the highest. MCM-22 obtained from silica sol and silicic acid has higher B/L acid ratios in the range of medium strong acid. The results of NMR show that the main aluminum in the samples is skeleton aluminum without obvious non-skeleton aluminum. MCM-22 zeolite can not be obtained when silica gel is used as silicon source because silica gel can adsorb the free water in the preparation system, suppressing the hydrothermal reaction. The reaction conditions should be carefully set up when silica gel is used as silicon source to prepare zeolite.
Abstract: As a green and clean renewable energy technology, microbial fuel cells (MFCs) have attracted extensive attention. The electrocatalysts with high activity and low-cost towards oxygen reduction reaction (ORR) are of great importance for the large-scale commercial applications of MFCs. Among multifarious cathode catalysts, manganese-based oxides showed high catalytic activity close to that of the precious metals. In this work, a sponge-like manganese dioxide (MnO2) electro-catalyst was successfully prepared by the electrodeposition method. The surface morphology and composition of as-prepared MnO2 catalyst were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and so on; the electrocatalytic activity of the obtained MnO2 material towards ORR were evaluated by the linear sweep voltammetry (LSV) in a neutral phosphate buffer solution. The results demonstrate that the as-prepared MnO2 catalyst appears as crystalline γ-MnO2 and has a high Mn3+/Mn4+ ratio, which is beneficial to improving the catalytic activity in ORR. The as prepared γ-MnO2 catalyst exhibits superior activity for the ORR under neutral conditions to the commercial MnO2 catalyst. An MFC coupled with as-prepared catalyst generates an open circuit voltage of 0.52 V, with a maximum power density of 975.6 mW/m2, about 1.7 times of that achieved with the MFC using commercial MnO2 as cathode catalyst, which suggests that the MnO2 catalyst prepared by the electrodeposition could be an economical alternative for Pt free catalysts in practical application of MFC.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
