Abstract: The understanding of the structural characteristics of lignite is of very importance to the lignite utilization. The structure parameters of Mile lignite in Yunnan were ascertained via Fourier transform infrared spectroscopy, 13C solid-state nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy and ultimate analysis. The results indicate that the aromaticity and number of aromatic ring substituents of Mile lignite are 38.79% and 3, respectively. The aromatic carbon structure typically contains benzene and naphthalene, while the aliphatic carbon structure mainly includes methyl and methylene. Oxygen dominantly exists in ether oxygen, carboxyl and carbonyl; nitrogen occurs in the form of pyrrole nitrogen and pyridine nitrogen; and sulfur is mainly present in thiophenol and mercaptan. According to the analysis results, a molecular structure model of Mile lignite is constructed, with a molecular formula of C147H148O36N2S. The semi-empirical PM3 basis set and the density functional theory M06-2X were adopted to optimize the molecular configuration. The optimized model has a significant three-dimensional configuration, in which the aromatic layers are arranged irregularly in space and the aromatic rings are connected by methyl, methylene, methoxy and alicyclic rings. The simulated FT-IR spectrum and simulated 13C NMR spectrum are in great agreement with the experimental spectrum, which proves the accuracy and rationality of the molecular model of Mile lignite.
Abstract: The migrating and diffusion of alkali metals affect catalytic gasification of coal char. The paper investigated in-situ gasification behaviors of coal char by TG and hot stage microscope, and studied catalytic performance of single NaAlO2 particle and Na distribution by SEM-EDX. The results show that in the beginning stage, the curve of carbon conversion obtained by area method is consistent with that by TG method. In the ending stage, the ash in coal char acts as framework of the particles, as a result, area of the particles keeps unchanged. Meanwhile, the ash hinders diffusion of gasifying agent into coal char, and decreases the gasification rate, so carbon conversion rate calculated by area change is lower than that from TG. The single NaAlO2 particle has catalytic performance. The coal char particles, which are closer to NaAlO2, have higher gasification reactivity, because the amount of migrating alkali is higher. The migrating distance of NaAlO2 is higher than 840 μm at 900 ℃ .
Abstract: Four HRTEM images of Yangquan No. 3 anthracite were quantitatively characterized, including fringe length, orientation and stacking distribution. The result indicates that the fringe characteristics are consistent with the coal rank characteristics of anthracite. The fringe of three different microcrystalline regions in image 1 was statistically analyzed. In region 1, the average fringe length is 0.87 nm, the overall fringe orientation distribution is disorderly, but there is still a small range of orderly arrangement between the short fringes and between the long fringes, and the maximum number of stacking layers is 4; In region 3, the fringe length is 1.01 nm on average, the orientation is higher in the range of 135°−180° with a ratio of 62.46%, and the maximum number of stacking layers can reach 6. The fringe distribution characteristic of region 2 is between 1 and 3. Most of the fringes are curved, and there may be heterocyclic rings and aliphatic rings. The FT-IR and 13C NMR data show that the aliphatic structure mainly exists in the form of aliphatic rings, which plays an important role in the process of forming long fringes by short fringes.
Abstract: Alkali metals are important factors affecting the process of biomass pyrolysis. In this paper, rice straw (RS) with different occurrence forms of alkali metals was used as the research object. The heat decomposition characteristics, the release law of small molecule gases and the change law of in-situ pyrolysis tar composition were investigated by the thermal mass spectrometer (TG-MS) and thermal pyrolysis-GC/MS (Py-GC/MS) to reveal the action mechanism of different occurrence forms of alkali metals in the pyrolysis process. The results showed that with the increase of the removal degree of alkali metal from rice straw, the release temperature of small molecules during the pyrolysis shifted to the high temperature region, due to the catalytic effect of alkali metals on the escape of small molecules. The different occurrence forms of alkali metals had different influences on the tar components. Water-soluble alkali metals inhibited the production of alcohols and promoted the production of ketones and aldehydes. Ion-exchanged alkali metals had different effects on oil composition at different temperatures. At the pyrolysis of 300 ℃, the presence of ion-exchanged alkali metals inhibited the production of aldehydes and ethers, and promoted the production of esters and ketones, but opposite effect was obtained at the temperature higher than 400 ℃. Kinetic analysis showed that both water-soluble alkali metal ions and exchanged alkali metal could reduce the activation energy of biomass pyrolysis.
Abstract: In order to investigate the evolution of carbon microstructure and gasification activity during circulating fluidized bed gasification, the simulated circulating gasification of a rice husk was carried out in a laboratory fixed bed reactor, and the pore structure, carbon microstructure and gasification activity of char during gasification were investigated. The results show that the BET surface area of char increases firstly and then decreases with an increase in gasification cycle times, and the surface areas of rice husk chars obtained from circulating gasification process are much higher than that of original char. The ID1/IG values of char decrease monotonously with an increase in gasification cycle times, indicating that the graphitization degree of carbon structure in char increases. Meanwhile, the relative content of AD3+D4 of chardecreases firstly and then increases slightly with the progress of circulating gasification, and the relative contents of AD3+D4 of all chars obtained from a circulating gasification process are lower than that of original char. Moreover, the gasification activity of char increases gradually with an increase in gasification cycle times, and the gasification activity of all chars obtained from a circulating gasification process are higher than that of original char.
Abstract: The extracted oil of intermediate base FCC slurry is split into eight narrow fractions with a boiling point interval of 20 °C by vacuum distillation. The aromatic composition and constitution of these narrow fractions were determined by measuring their density, carbon residue and kinematic viscosity as well as elemental analysis, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (GC×GC TOF MS). The results indicate that the density, carbon residue and kinematic viscosity of each narrow fraction increase with the increase of boiling point, in particular with a boiling point higher than 420 °C. The aromatics consist of mainly tricyclic and tetracyclic aryl hydrocarbons in the narrow fractions with a boiling point lower than 440 °C; the content of pentacyclic aromatics increases rapidly with the increace of boling point over 440 °C, though the pentacyclic aromatics are also present in the narrow fractions with a boiling point of 400–420 °C. The aromatics in the FCC slurry are highly-condensed and contain a small amount of short-alkyl groups. The heteratomic compounds in the narrow fractions include mainly sulfur- and oxygen-containing compounds, whereas the content of nitrogen- and halogen-containing compounds is very low.
Abstract: The content, distribution and forms of the ferrum or calcium compounds in a crude oil, the corresponding vacuum residue (VR), hydrogenation feedstock and hydrogenation products were studied. The separation method was studied by column chromatography and solvent extraction method. This work indicated that in the process of column chromatographic separation, some ferrum or calcium compounds in the oil samples were irreversibly adsorbed on the chromatographic column, resulting in the loss of 58% of the ferrum compounds and 76% of calcium compounds. The solvent extraction method could effectively reduce the loss of the metal components and was suitable for the study of the content of metal elements. More than 97% of the ferrum or calcium compounds were distributed in the VR fraction. The 60% to 90% of the ferrum or calcium compounds were distributed in the resin and asphaltene components. During the hydrogenation reaction, the ferrum or calcium compounds in vacuum residue were mainly removed from the resin components, and the overall removal ratio was close to 30%. The ferrum compounds prefered to bond in the asphaltene components and were difficult to remove. Through the process of atmospheric distillation and vacuum distillation of the crude oil, the relative distribution of the oil-soluble ferrum compounds decreased from 95.6% to 64.7%, and the relative distribution of the water-soluble ferrum compounds increased from 4.4% to 35.3%. Through the process of the hydrogenation reaction, 38% of the oil-soluble ferrum compounds were converted into the water-soluble ferrum compounds and 30% of the oil-soluble calcium compounds were converted into the water-soluble calcium compounds in the reaction.
Abstract: 1,2-pentanediol (1,2-PeD) and 1,5-pentanediol (1,5-PeD) are high-value fine chemicals with a wide range of uses. It is a green process with well application prospects and research value for the preparation of 1,2-PeD and 1,5-PeD from furfural and its derivatives. Here, the recent advances of furfural and its derivatives furfuryl alcohol and tetrahydrofurfuryl alcohol in the synthesis of 1,2-PeD and 1,5-PeD were reviewed systematically. We focused on the summary of the catalysts used in the catalytic hydrogenation of furfural, furfuryl alcohol and tetrahydrofurfuryl alcohol to prepare 1,2-PeD and 1,5-PeD. The design and application of the catalysts were elaborated from many aspects, including the catalyst type, the reaction mechanism with assist acid/base in different catalytic systems, the synergistic catalysis between active metals and doped transition metal oxides, the influence of acidity of doped transition metal oxides in the catalyst, the structure-activity relationships and so on. On this basis, the development trend of this research direction is prospected. It provides the theoretical guidance and useful reference for developing a new, efficient and stable catalyst system for the hydrogenation of furfural and its derivatives.
Abstract: The effect of Si content on the performance of slurry CuZnAl catalyst prepared by complete liquid phase technology for direct synthesis of dimethyl ether from syngas was investigated. Among them, catalyst with Si/Al ratio of 0.5 showed the best catalytic performance with the CO conversion of 63.31% and the dimethyl ether selectivity of 72.96%. The catalyst was stable after 480 h reaction. As revealed by the X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen adsorption and desorption characterizations, the introduction of Si promoted the dispersion of Cu species nanoparticles and led to increased specific surface area, which was beneficial for improving the CO conversion. Besides, temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) characterizations showed that an electronic interaction between Cu species and other components of the catalyst (especially, Si species) could inhibit the reduction of Cu species, resulting in the abundant Cu+ species on the catalyst surface. This was conducive to the synthesis of methanol and could effectively inhibit the formation of CO2, which was a by-product of the water-gas shift reaction. Moreover, a large amount of Al species (AlOOH) was enriched on the SA0.5 catalyst surface, which might contribute to the dehydration of methanol to produce dimethyl ether. In conclusion, the synergetic catalysis of Cu+ and AlOOH in slurry CuZnAlSi system improved the catalytic activity and dimethyl ether selectivity.
Abstract: Composite oxides of copper and manganese are widely used in oxidation reactions, and the main active component is copper-manganese spinel, whereas the copper oxide and manganese oxide show extremely low activity, despite that they are beneficial for CO oxidation. In this paper, it was found that the synergistic effect of Cu1.5Mn1.5O4 and CuO could promote the catalytic oxidation of CO. The catalysts were prepared using the citric acid complexation method and they were characterized through combined the techniques of N2-adsorption desorption, XRD, H2-TPR, TEM, CO-TPD and O2-TPD. The catalytic performance of various catalysts in CO oxidation was then evaluated. The results confirmed that Cu1.5Mn1.5O4 modified with CuO exhibited the best catalytic performance and the highest unit surface activity (defined as the CO conversion rate per unit surface area of catalyst). CuO and Cu1.5Mn1.5O4 had a synergistic effect, where O2 was activated by CuO and it then interacted with CO, activated by Cu1.5Mn1.5O4, to form CO2, thus increasing the catalytic activity.
Abstract: The isomerization-transalkylation coupling reaction between 1-methylnaphthalene and 1,3,5-trimethylbenzene was studied over zeolite catalysts to produce 2-methylnaphthalene and dimethylnaphthalene. The catalytic performance of zeolites with MWW, BEA, FAU and MFI topological structure was investigated and the reaction mechanism was discussed. The properties of zeolites were characterized by XRD, N2 adsorption-desorption, SEM, NH3-TPD, Py-FTIR and ICP. Compared with MFI zeolite with 10-membered ring channel, MWW, BEA and FAU zeolite with 12-membered ring channel showed better catalytic activity. BEA zeolite exhibited higher selectivity to dimethylnaphthalene, while MWW zeolites showed higher selectivity to 2-methylnaphthalene and the best catalytic stability. As a branch of MWW zeolites, HMCM-22 showed a 1-methylnaphthalene conversion of 70.27% and a 2-methylnaphthalene yield of 66.69%. It was worth noting that a relatively high yield of 2-methylnaphthalene (35.74%) and dimethylnaphthalene (19.00%) were obtained on HMCM-56 at the same time. This research has opened up a promising route using C10 aromatics as raw materials for the preparation of 2,6-dimethylnaphthalene, an important polyester monomer.
Abstract: Carbon-based oxygen reduction catalysts are widely used in catalyzing the oxygen reduction reaction (ORR) due to their low cost, good electrical conductivity, controllable pore structure and good electrochemical stability. In this paper, carbon materials were prepared from different parts of biomass (leaves and stems) through one-step pyrolysis method. The performance of the obtained catalysts was analyzed by X-ray diffraction (XRD), Raman, X-ray Photoelectron Spectroscopy (XPS) and Linear Sweep Voltammetry (LSV). The results demonstrate that compared with the stem carbon, the leaf carbon contains high contents of P, S and N, especially quaternary-N and pyridinic-N, which are responsible for the high performance in the ORR with onset potentials of 0.529, 0.215 and −0.046 V (vs. SCE) in wide ranges of pH (acid, alkali and neutral solutions, respectively). This indicates that biomass based carbon material especially leaf based shows a great application potential for catalyzing ORR in fuel cells.
Abstract: A series of Ce-Fe-Ox catalysts containing sulfate species was prepared by four different methods including sol-gel (Fe-SG), hydrothermal (Fe-HT), co-precipitation (Fe-10) and solid state grinding synthesis (Fe-SSGS) methods. The Ce-Fe-Ox catalysts were used in the selective catalytic reduction (SCR) of NOx by NH3 and the effect of sulfate species on the catalytic performance was investigated. The results indicate that the Fe-HT catalyst prepared by the hydrothermal method exhibits excellent performance in the NH3-SCR of NO, with a NO conversion of nearly 100% even at 250 °C. The Fe-HT catalyst contains proper amount of sulfate, which can decrease the CeO2 crystallinity and enhance the catalytic performance in the NH3-SCR of NO. The Fe-HT catalyst has a high content of surface Ce3+ and Fe3+ and there is a synergy between the Fe and Ce species, which can improve the redox capacity and greatly increase the quantity of chemisorbed oxygen. In contrast, excessive amount of sulfate species in Fe-SSGS and Fe-SG may reduce the synergy between Fe and Ce and then impair the catalytic performance of Ce-Fe-Ox in NH3-SCR.
Abstract: In order to study the formation pathway of N2O in NH3-mediated selective catalytic reduction (NH3-SCR) of NOx process and the variation of N2O selectivity affected by pressure, in situ synchrotron radiation photoionization mass spectrometry (SR-PIMS) and flow tube reactor were used to detect the gaseous species in the NH3-SCR reaction over 3Mn10Fe/Ni catalyst. The variations of N2O selectivity, NOx conversion and NH3 conversion were analyzed under different conditions. The results show that the formation of N2O is mainly from non-selective catalytic reaction (NSCR) and adsorbed NH3 oxidation (NSNO). Among them, NSCR plays a dominant role in N2O formation in the temperature range of 100−250 ℃. The contributions of the two formation pathways in the temperature range of 250−400 ℃ are equivalent, and NSNO is the main source in the temperature range of 400−500 ℃. In addition, low pressure reduces the denitration activity of the catalyst at low temperature, but promotes the formation of N2O via NSNO reaction at high temperature.
Abstract: The adsorption behaviors of the model molecule dibenzofuran (DBF) with similar molecule structure and size to dioxins on the activated carbon was elucidated. The activated carbon adsorbent was coconut shell-based. The adsorption experiments were conducted at 120 ℃. The activated carbon samples were modified by nitric acid at 300, 500, and 800 ℃, and their DBF adsorption capacities were compared. The physico-chemical properties of samples were characterized by BET, TPD-MS, elemental analysis, and other instruments. The results demonstrated that nitric acid treatment could inhibit the adsorption of DBF on activated carbon. The DBF adsorption capacity of activated carbon was related to its surface oxygen-containing functional groups. Lactone groups on activated carbon had the biggest influence on the DBF adsorption. Heat treatment reduced the content of surface oxygen-containing functional groups, and improved the adsorption capacity of DBF.
Abstract: NiFe oxyhydroxide and hydroxide have been proven to be efficient and earth-abundant non-noble metal catalysts for the oxygen evolution reaction (OER). However, the fragile nature of these oxyhydroxides or hydroxides severely reduces the long-term stability and hinders the industrial applications. Meanwhile, the poor electrical conductivity of these materials also has seriously led to the higher overpotential when applying to the OER. Herein, a novel method using polyurethane (PU) sponge as electroplating was carried out to design NiFe alloy foam with different Fe content for OER. The physical properties of NiFe alloy foams were characterized by Scanning Electronic Microscopy (SEM), Energy Dispersive System (EDS) and X-Ray Diffraction (XRD), respectively, suggesting that the porous NiFe alloy is formed with uniform distribution of Ni and Fe. The OER performance was tested by Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV), Electrochemical Impedance Spectroscopy (EIS), I-t, etc. The results showed that the doped Fe could significantly improve the conductivity and OER performance of Ni foam. The NiFe alloy foam with 30% Fe exhibited 292 mV overpotential at 10 mA/cm2 and the Tafel slope 126.12 mV/decade in alkaline solution with excellent long-term stability. Without any complex electrode preparation processes and binders, NiFe alloy foam is much convenient to use as anode of water splitting in alkaline media for industrial applications.
Abstract: In this study, multi-walled carbon nanotube (MWCNTs)-SiO2 composite adsorbents MWCNTs-SiO2-2, MWCNTs-SiO2-4, MWCNTs-SiO2-6 (CS2, CS4, CS6) with molar percentages of MWCNTs of 38%, 52%, and 66% were synthesized using the sol-gel method. The effects of the MWCNT content, temperature (30−60 °C), water vapor concentration (1%−5%), and the number of cycles on the adsorption capacity of toluene were studied, and an adsorption kinetics analysis was performed. The results showed that the adsorption capacity for toluene at 30−60 °C was AC (activated carbon) < CS2 < CS4 < CS6, and the adsorption capacity of CS6 to toluene was up to 50.28 mg/g. For every 10 °C increase in temperature, the penetration time decreased by 10−20 min, and the adsorption content decreased by 3.5% for every 1% increase in water vapor concentration. The phase with the fastest mass transfer rate of toluene could be described by the quasi-secondary adsorption kinetics model, in which intraparticle diffusion plays a major role. The mole percentage of MWCNTs ranged from 38% to 66%, the higher the content was, the easier it was to adsorb toluene. The functional group types of the MWCNTs-SiO2 adsorbent after regeneration did not change, and the adsorbent maintained good adsorption performance.
Abstract: Pd-based catalysts have been widely used in alkaline fuel cells. However, up to now, the effects of oxidation treatment of Pd-based catalysts on their application in alkaline fuel cells have been rarely reported. In this paper, PdCo nano-metal catalyst was prepared by calcination-oxidation treatment. It was found that the mass specific activity and area specific activity of the resulting PdO-Co3O4 nano-composite for electrocatalytic oxidation of ethylene glycol in alkaline solution were 3.8 and 2.4 times that of commercial Pt/C, respectively. Compared with PdCo nanometals, the mass specific activity and area specific activity of the PdO-Co3O4 nanocomposite for the electrocatalytic oxidation of ethylene glycol in the alkaline solution increased by 1.6 and 1.2 times, respectively. The experimental and calculated results showed that the surface morphology and active center of the catalyst changed after calcination and oxidation treatment. The adsorption energies of O2 and OH on the Co doped PdO (101) surface decreased, which was beneficial to stabilize the intermediate C2H4OHO*. As a result, the energy barrier for the O−H dissociation on the Co-doped surface was reduced. The strong binding of Co doped PdO (101) with ethylene glycol and its intermediate species led to different electrochemical kinetics and reaction path to produce excellent electric catalytic activity. The synergistic effect of PdO and Co3O4 significantly enhanced the interaction between active oxygen and catalyst surface, which not only facilitates the formation of superoxide species on the catalyst surface, but also improves the redox properties of the catalyst and promotes the electrocatalytic oxidation activity of ethylene glycol. The strategy of bi/multi-metallic oxidation proposed in this paper provides a general methodology for the construction of other catalysts.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
