Abstract: A series of hierarchical ZSM-5 zeolites was prepared by seed induction method and alkali-treated method, and their crystal structural, textural and acidic properties were characterized by XRD, TEM, NH3-TPD, and N2-sorption. The effect of hierarchical ZSM-5 zeolites on product distribution of low rank coal fast pyrolysis in fluidized bed was investigated. The results showed that the specific surface area, mesoporous pore volume and average pore size of the zeolites were increased to different degree after alkali treatment. Hierarchical ZSM-5 zeolites promoted the cyclization of aliphatics and the dissociation of phenol pool of volatile from coal pyrolysis, and increased the content of light aromatics. The yield of light aromatics reached the maximum at 0.3 mol NaOH. The content of mono-aromatics and naphthalene/methylnaphthalene increased by 2.7 times and 0.9 times respectively compared with microporous zeolites. The catalysts performance decreased at 0.4 mol NaOH due to excessive desilication.
Abstract: A fixed-bed pyrolysis experiment was adopted to generate solid products of Shengli lignite (SL) and hydrochloric acid-demineralized lignite (SL+) at different temperatures. The structural properties of the chars were investigated by FT-IR, XPS, XRD, and Raman spectroscopy to correlate with the microstructural evolution of SL and SL+ during pyrolysis. The results indicated that the concentration of oxygen-containing structures in hydrochloric acid-demineralized lignite/chars was relatively high and decreased with increasing pyrolysis temperature. The mineral components demineralized by hydrochloric acid limited the orderly arrangement of aromatic rings, promoted the condensation of aromatic ring clusters, caused more crystalline defects in the chars, and was adverse to the development of side chains during pyrolysis.
Abstract: Naomaohu sub-bituminous coal (NMH) was thermally dissolved in isometric methanol/toluene mixed solvent affording soluble portions (SPs) and thermal dissolution residues (RTD), then hydroconversion of SP320 was catalyzed over Co/C@N-700 catalyst affording CSP320. The composition and structural characteristics of SP320 before and after catalytic hydroconversion were analyzed with a gas chromatograph/mass spectrometer (GC/MS), and pyrolysis reactivity and structural characteristics of NMH and RTD were characterized with Fourier transform-infrared spectroscopy (FT-IR), thermogravimetry, as well as solid state 13C nuclear magnetic resonance (13C NMR). The SPs yields increase with increasing temperature, and reach a maximum (36.46%) at 320 oC. GC/MS analysis shows that SP320 are mainly composed of alkanes, phenols and arenes, and their relative contents are 45.45%, 18.03% and 24.75%, respectively. After catalytic hydroconversion, relative contents of arenes and phenols in CSP320 decrease to 3.86% and 13.6%, respectively, while those of alkanes and alcohols increase to 66.99% and 9.36%, respectively, and kinds of cycloalkanes increase from 8 to 24. These results indicate that arenes and phenols in SP320 could be hydrogenated into alkanes and alcohols catalyzed by Co/C@N-700. Compared to NMH, RTD possesses higher thermal stability, more aromatic carbons, and less carbonyl carbons in its skeleton structure. In addition, intensity of adsorption peaks attributed to O−H, −CH2−, C=O and C−O−C in the FT-IR spectrum of RTD are weaker, while adsorption peaks assigned to aromatic C=C are stronger than those of NMH.
Abstract: Hydroliquefaction behavior of preasphaltenes, derived from direct coal liquefaction, was carried out in a 30 mL autoclave with FeS + S catalyst and tetralin at initial hydrogen of 5.0 MPa, residence time of 0−60 min and reaction temperature of 380−440 °C in order to optimize the conditions of direct coal liquefaction and improve oil yield. The products distribution and kinetic parameters of preasphaltenes catalytic hydroliquefaction were investigated. A new kinetic model was established to simulate the preasphaltenes hydroliquefaction catalyzed by FeS + S catalyst using lump kinetic model. It was found that preasphaltenes were hydroliquefaction into asphaltenes and char directly, and then asphaltenes were hydrocracked into oil + gas products. Regressive reactions of preasphaltenes to char and asphaltenes to preasphaltenes occurred at higher temperatures. Higher temperature and longer time were favorable for increasing the conversion of preasphaltenes and the oil + gas yield. The hydroliquefaction of preasphaltenes under 440 °C and 60 min reached 79.45% with 34.7% of oil + gas yield. The hydroliquefaction conversions calculated from the model agreed well with the experimental data, and the activation energies ranged within 50−245 kJ/mol.
Abstract: A vitrinite-rich low rank coal, Baishihu (BSH) coal with moderate sulfur content was treated by dehydration and crushing. The treated samples were pyrolyzed in an alloy tubular reactor under 2 MPa. Influence of iron catalyst and atmosphere on sulfur transformation during pressurized low-temperature coal pyrolysis was investigated. Molecular composition of sulfur compounds in tar was characterized by gas chromatography with sulfur chemiluminescence detector (GC-SCD) combined with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Sulfur K-edge XANES was used to study sulfur molecular structure after pyrolysis. Sulfur compounds in BSH coal are predominantly S1 class species in branch chain of the coal. Elemental sulfur in catalyst enters the tar and forms mercaptan or thioether compounds during pyrolysis. Iron catalyst promotes activation of hydrogen atoms in coal and contributes to hydrogenation saturation and cracking of aromatic sulfide in tar. The catalyst preferentially captures H2S to increase content of pyrite in char and inhibits formation of sulfate. Under H2 atmosphere, significant decrease of thiophene compounds is observed with catalyst coupled with decrease of sulfoxide compounds.
Abstract: Four kinds of organic solvents were used to pretreat Ordos lignite to obtain swelling coal. The effect of swelling on the structure and pyrolysis characteristics of Ordos lignite was investigated by fast pyrolysis of swelling coal in a powder-particle fluidized bed. The swelling coal and pyrolysis products were characterized by FT-IR, TGA, GC-MS, 13C NMR, XRD. The results show that non-polar solvent has little effect on coal structure. The polar solvents can reduce the hydrogen bond crosslinking of oxygen-containing functional groups of lignite, increase the fluidity of small molecules and the average pore diameter of coal. After swelling, The yield of coal tar and gas phase yield increases, the pyrolysis water yield decreases. After pretreatment with methanol, acetone, and tetrahydrofuran, the yield of pyrolysis tar increased by 18.88%, 26.72%, 33.58% respectively. Compared with raw coal, and the contents of phenolic, monocyclic and bicyclic aromatic hydrocarbons components in the light components of tar were significantly increased.
Abstract: Mercury (Hg), a kind of heavy metal pollutant, has a great impact on the environment and human health. The highly efficient technology for Hg removal has attracted widespread attention from researchers. In this study, the coal gasification slag (CGS) and the slag after sorting were used as sorbents, and the Hg0 removal performance of the sorbents were investigated through the fixed-bed reactor and entrained flow reactor. The characterization methods such as N2 adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) were performed to analyze the physical and chemical characteristics of the sorbents. According to the results of fixed-bed Hg0 removal experiment, the Hg0 removal efficiency of the origin slag (OS) and high carbon slag (HCS) could maintain more than 91% at 60−120 ℃. The high ash slag (HAS) showed the highest Hg0 removal efficiency of 97% at 60 ℃, which was greatly affected by the Hg0 removal temperature. The Hg-TPD (Hg-temperature program desorption) and XPS results indicated that the chemisorbed oxygen on the sorbent participated in the Hg0 oxidation process with HgO formed on the surface of the sorbent. According to the results of entrained flow Hg0 removal experiments, the Hg0 removal efficiencies of OS and HCS were 56% and 57% at C/Hg ratio of 40000 and the Hg0 removal temperature of 60 ℃, respectively. When the C/Hg ratio was 80000 and the Hg0 removal temperature was 60 ℃, the Hg0 removal efficiencies of OS and HCS were 100% and 82%, respectively.
Abstract: Direct solid-solid reaction characteristics of cotton stalk char (CSC) and nickel loaded olivine (Ni/olivine) were studied using micro-fluidized bed reaction analyzer (MFBRA). Model fitting method was used to fit 29 model functions under isothermal conditions. Three optimal models were selected to calculate kinetics of the solid-solid reaction of cotton char and oxygen carries. The results show that CO and CO2 are main gas products of CSC and Ni/olivine. CO is first and then CO2 is evolved during the reaction. CSC does not completely convert into CO2, and concentration of CO is higher than that of CO2. With increasing reaction temperature, concentration and yield of CO and CO2 in the product gas increase obviously. The average activation energies for CO, CO2 and CSC are 27.5, 46.4 and 69.8 kJ/mol, respectively. The non-isothermal reaction characteristics and kinetics of CSC and Ni/olivine were studied by thermogravimetric analyzer (TGA). The results show that reaction of CSC and Ni/olivine starts at 750 ℃, and reached the peak at 890 ℃. The activation energy of non-isothermal reaction is 72.05 kJ/mol, which is in accordance with the result of MFBRA. It indicates that the solid-solid reaction between char and nickel-based oxygen carrier easily occurs in during chemical looping gasification of biomass.
Abstract: Catalysts for methane dehydroaromatization (MDA) were prepared using melamine as nitrogen source, doped with modified HZSM-5 zeolites and loaded with active metal component Mo. Using XPS, N2-isothermal adsorption and desorption, XRD, H2-TPR, TEM and NH3-TPD, properties of the catalyst and state of active metal components were analyzed. Its catalytic performance for MDA reaction was investigated. The results showed that HZSM-5 after modified with melamine not only formed a layer of carbon and nitrogen groups on surface of the zeolites, but also controlled the medium and strong acid sites of the zeolites in orderly. At the same time it induced better anchor of Mo metal components on surface of the catalyst. The Mo/HZSM-5-CN catalyst prepared by this method could effectively increase methane conversion rate and aromatic selectivity of the MDA reaction, slow down generation of carbon deposits, and exhibit better catalytic performance.
Abstract: Low selectivity to target products and poor catalytic stability remain two crucial issues for the conversion of methanol to aromatics (MTA) catalyzed by ZSM-5 zeolites. In this work, the variance in catalytic performance of ZSM-5 zeolites with the time on stream during a long term MTA test was monitored and related to the structural changes which were characterized by XRD, physisorption, NH3-TPD, TEM, TG and 27Al MAS NMR; the key structural factors affecting the catalytic performance and structure were then investigated. The results illustrate that within the early 19 h after starting the reaction, the amount of acid sites decreases significantly from 0.41 to 0.17 mmol/g due to the damage to the structure of aluminum species under high temperature hydrothermal conditions; the selectivity to light alkenes increases significantly, accompanying with a rapid increase of the liquid hydrocarbons yield from 14.7% to 19.3%. In the next stable reaction stage of 24 h, the rate of coke formation increases and the surface area decreases significantly from 340 to 275 m2/g, whilst the amount of acid sites decreases continuously to 0.10 mmol/g; the liquid hydrocarbon yield keeps above 19.5%, suggesting that a small amount of acid sites will be sufficient to stably bolster the MTA reaction. In contrast, in the next 31 h, although the rate of coke formation decreases obviously, the catalyst is deactivated gradually, dominantly by the coke deposition on the external surface; in this period, the surface area and the amount of acid sites decreases continuously and slowly and the liquid hydrocarbon yield drops to 17.3%, accompanying with a decrease in the selectivity to aromatics. At the end of the reaction of 7 h, the liquid hydrocarbon yield drops to 12.2%, due to the complete coverage of the acid sites and serious blockage of the pore by coke deposition; meanwhile, the selectivity to CH4 increases significantly from 13.2% to 24.2%, whereas the fraction of p-xylene in xylenes increases from 24.4% to 33.1%, owing to the suppression of isomerization on the external surface acid sites which are covered by coke deposition. As the agglomerated particles are covered by coke in the deactivated catalyst, it is then proposed that a diminution of the contact between the external surfaces of particles could improve the accessibility of the reactant molecules to the active sites and enhance the coke capacity. The results may provide some relevant suggestions for the control of acidity and morphology in the preparation of MTA catalysts.
Abstract: CO2 hydrogenation to light olefins is an exothermic reaction, while propane dehydrogenation to propylene is an endothermic reaction, and with generating of hydrogen. Coupling of the two reactions can break the equilibrium limit of thermodynamics and dynamics of the single reaction and improve yield of propylene. Therefore, the effects of different crystalline zeolites (HZSM-5, SAPO-34 and Al-SBA-16) on the reactivity of propane coupled with CO2 to propylene were investigated. The properties of different zeolites were characterized by means of XRD, SEM, NH3-TPD, N2 desorption and TG, and the catalytic performance of the three different zeolites in the reaction of propane and carbon dioxide coupling to propylene was investigated in a fixed bed reactor. The experimental results showed that HZSM-5 zeolite had high content of weak acid, large specific surface area and excellent catalytic activity. Typically the propane conversion rate is 10.5%, the CO2 conversion is 3.0%, the propylene selectivity is 38.4 and the yield is 4.0% when the volume ratio of propane to CO2 is 1:4, the reaction pressure is 0.1 MPa, the reaction temperature is 580 ℃, the catalyst mass is 0.2 g and the space velocity is 6000 mL/(gcat·h).
Abstract: The K-Fe3O4 and Ni-AlMCM-41 catalysts were first prepared by a solvothermal and ion-exchange methods, respectively; they are then assembled to K-Fe3O4/Ni-AlMCM-41 tandem catalyst for CO2 hydrogenation to long-chain hydrocarbons. The catalyst samples were characterized in detail by means of XRD, SEM, TEM, NH3-TPD, olefin-TPD, ICP-OES, XRF and XPS; the effect of potassium modification and Si/Al ratio on the performance of Fe3O4/Ni-AlMCM-41 tandem catalyst in the hydrogenation of CO2 was investigated. The results illustrate that the Fe3O4 component has a uniform spherical particles in the size range of 400–800 nm, whilst the Ni-AlMCM-41 component displays mesoporous structure, dominantly with weak acid sites on the surface. CO2 is first converted to gaseous products rich in light olefins over the K-Fe3O4 catalyst and the light olefins is then transformed to long-chain hydrocarbons by a series of oligomerization and hydrogenation reactions over the acid sites of Ni-AlMCM-41. Appropriate content of potassium can improve the selectivity to light olefins over the Fe3O4 catalyst in the first stage. In particular, for CO2 hydrogenation under 2 MPa and with a space velocity of 1000 h−1 and a H2/CO2 ratio of 3, when 0.5%K-Fe3O4 (320 °C) is connected with Ni-AlMCM-41(Si/Al = 50) (250 °C), the conversion of CO2 reaches 32.9% and the selectivities to CO, CH4, and long-chain hydrocarbons are 7.1%, 10.9% and 49.8%, respectively. That is, the selectivity to long-chain hydrocarbons over the K-Fe3O4/Ni-AlMCM-41 catalyst (49.8%) is much higher than that over the single K-Fe3O4 catalyst (12.2%).
Abstract: The $ {\rm{Cu(}}{{\rm{C}}_{\rm{2}}}{{\rm{O}}_{\rm{4}}}{\rm{)}}_2^{2 - } $ complexed anion intercalated ZnAl-LDH hydrotalcite pure phase precursors were prepared by co-precipitation, ion exchange and calcination-reconstruction methods; after that, the Cu-ZnAl-LDO catalysts with lamellar structure were obtained by calcination of the precursors. The precursors and catalysts were characterized by XRD, TEM, ICP, H2-TPR, N2O-H2 TPD titrations and N2 physisorption; the effect of preparation method on the confinement degree of intercalated active Cu species and the catalytic activity and stability of Cu-ZnAl-LDO in methanol synthesis was investigated. The results indicate that compared with the ion exchange and calcination-reconstruction methods, the CP-Cu-ZnAl-LDO catalyst prepared by co-precipitation method has a higher interlayer Cu content as well as a stronger confinement effect of layer plate on the Cu species. In addition, the unique ordered layered structure of hydrotalcite can also improve the dispersion of active Cu species between the layers and inhibit the sintering of Cu particles. As a result, the CP-Cu-ZnAl-LDO catalyst prepared by co-precipitation method exhibits excellent performance in methanol synthesis; the space-time yield of methanol reaches 3412 mg/(gCu·h) and basically no deactivation is observed after continuous reaction for 60 h.
Abstract: CoMoS/ZrO2 catalysts with different Co-Mo atomic ratios (0.25, 0.30, 0.35, 0.40 and 0.45) and Co-Mo loading amounts (2.35%, 4.36%, 7.48% and 10.79%) were prepared by incipient wetness impregnation. These catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (H2-TPR), nitrogen adsorption/desorption and X-ray photoelectron spectroscopy (XPS). 4-methylphenol was used as model compound for hydrodeoxygenation reaction. The result showed that when the atomic ratio of Co-Mo (Co/Co + Mo) was 0.30 and the Mo loading amount was 4.36%, the highest hydrogenation activity was observed. The conversion of 4-methylphenol was up to 99.86% and the selectivity of main product toluene reached to 87.85%. The formation of CoMoO4 was unfavourable to the formation of toluene. An appropriate interaction between Co-Mo and ZrO2 was required.
Abstract: Catalytic decomposition of methane is a promising route for hydrogen production owing to simple operation, easy separation of the products and no COx emission. In this work, a mesoporous Ni/SiO2 catalyst was prepared by impregnation method and used in methane decomposition; the fresh and spent catalysts and the morphology of deposited carbon were characterized by N2 adsorption-desorption, X-ray diffraction, hydrogen temperature programmed reduction, scanning electron microscopy and transmission electron microscopy. The effects of calcination temperature, metal loading and reaction temperature on the catalytic performance of Ni/SiO2 in methane decomposition were investigated. The results show that the Ni/SiO2 catalyst exhibits mesoporous structure. The calcination temperature has a slight effect on the textural properties and catalytic performances of Ni/SiO2, but a significant influence on the agglomeration degree of Ni particles on the catalyst surface. The catalytic activity of Ni/SiO2 increases first with increasing the metal loading up to 30% and then declines with a further increase of metal loading. Meanwhile, the reaction temperature has a remarkable influence on the catalytic activity and stability and the state of the deposited carbon; a high temperature results in the decrease of the catalytic stability and the formation of encapsulated carbon. In particular, for the methane decomposition over the 30% Ni/SiO2 catalyst, the methane conversion of about 9.8% was obtained at 500 °C after reaction for 1000 min; the yield of carbon nanofiber at 500 °C is about 7.2 times higher than that at 650 °C.
Abstract: The spherical structure can reduce the transmission distance of electrode ions. Preparation the porous carbon spheres with spherical structure, high specific surface area and simple method is critical for the electricity storage device. In this paper, the porous carbon spheres were obtained from waste liquid via hydrothermal treatment followed with K2FeO4 activation. The effect of K2FeO4 mass on the capacitive behavior of porous carbon spheres was investigated in detail. The results show that the samples obtained display spherical structure with hierarchical pore size distribution, which contain rich micropores and some mesopores. In the three system, the sample (PCS-2) with the mass ratio of K2FeO4 to char of 2 possesses high specific surface area and good electrochemical performance. In addition, the specific capacitance of PCS-2 is as high as 323 F/g at the current density of 0.5 A/g in 6 mol/L KOH electrolyte. The symmetric supercapacitor assembled with K2FeO4 to char of 3 electrode can deliver 47.2 W·h/kg energy density and maintain 89% capacitance after 10000 cycles in 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid.
Abstract: The refined raw material was first prepared from the low-medium temperature coal tar through hydrogenation for 1.5 h under 330–390 °C and 8 MPa, with a catalyst/oil mass ratio of 1∶40, which was then used to produce needle coke through thermal polymerization and calcination. The composition of refined raw materials was analyzed by elemental analysis, Fourier-transform IR spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) and the structure of needle coke was characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD) and polarizing microscope; the effect of raw material composition (related to the hydrogenation temperature) on the structure of needle coke was then investigated. The results indicate that a proper increase in the hydrofining temperature is beneficial to the removal of heteroatoms (especially sulfur). By hydrogenation at 390 °C, the aromatics in the feedstock are polarized due to the cracking and polycondensation. In addition, a higher content of tricyclic and tetracyclic aromatics in the refined raw materials may also lead to a higher graphitization degree for the needle coke product.
Abstract: Different contents of calcite (CaCO3) were loaded on a deminerized Ningxia anthracite during the activated coke (AC) preparation, the influence of which on the preparation, desulfurization and/or denitrification of AC was investigated. The results show that calcite can regulate the pore structure and surface chemistry of AC. The total specific surface area and the micropore specific surface area decrease from 746 m2/g and 645 m2/g to 408 m2/g and 244 m2/g, respectively, when the calcite addition is up to 8%. The total volume and the micropore volume also decrease with the increase in the content of calcite, while the volume of mesopores and macropores increases. As the calcite addition rises, the oxygen-containing functional group and π−π* are increased linearly, and the sulfur capacity of AC first increases and then decreases during single desulfurization, the NX-2%CaCO3-AC having the best desulfurization capacity (84.0 mg/g). The increase in the content of π−π* by the addition of calcite promotes the SO2 oxidation process, and also promotes the denitrification process, the NO conversion (16.9%) with the addition of 2%CaCO3 is 1.14 times higher than that of AC (7.9%), mainly owing to the increase in the number of basic groups. However, during simultaneous desulfurization and denitrification, the presence of CaO in the AC promotes the sulfur capacity but decreases the NO removal efficiency due to the competitive adsorption and ammonium salt generation.
Abstract: Simultaneous desulfurization and denitrification of marine diesel exhaust was carried out by coupling the dielectric barrier discharge (DBD) with corona discharge pulse (CDP) to generate non-thermal plasma (NTP). The effect of various gas components in the exhaust gas and the amount of monoethanolamine, discharge current, gas flow rate and other factors on the desulfurization and denitrification were then investigated and the mechanism of denitrification by NTP was discussed. The results show that when the total gas flow rate is 650 mL/min, applying 1.67 A current discharge and adding 0.48% monoethanolamine to the simulated marine diesel exhaust (N2/O2/SO2/NOx/CO2/H2O) can weaken the negative effects of oxygen and water vapor on the denitrification. Besides, monoethanolamine can also weaken the negative effects of carbon dioxide by absorbing carbon dioxide from the exhaust and the final denitrification rate reaches 94%. Meanwhile, a high desulfurization rate (97%) is also achieved, as monoethanolamine can absorb sulfur dioxide rapidly, which is almost unaffected by any exhaust gas components.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
