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Abstract(11) HTML(5) PDF 1068KB(3)
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Pt/C, PtBi(95∶5)/C, Pd/C, and PdBi(95∶5)/C were synthesized by the sodium borohydride reducing method to produce metal nanoparticles with advanced electronic properties to enhance the ethanol oxidation reaction (EOR) mechanism. The Transmission Electron Microscopy (TEM) images and X-ray photoelectron spectroscopy (XPS) showed that a small Bi content does not affect the nanoparticle size PdBi/C; in contrast, it does affect the PtBi ones. The X-ray diffraction analysis revealed a lattice parameter modification by Bi dope in Pt crystalline structure. Furthermore, the ATR-FTIR results indicated the suppression of carbonate formation and increment in acetate production. The results of polarization and power density curves on DEFC, the material PtBi/C presented the more high power density, almost six times bigger than Pt/C. PtBi/C also has the highest current density (44 mW/cm2) and the lowest onset potential (−0.6 V) in linear sweep voltammetry experiments. It also has the highest final current density in current-time experiments. Hence, PtBi/C is a very promising electrocatalyst for DEFC.
Abstract(16) HTML(4) PDF 1028KB(3)
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Effects of calcium content on the performance of HZSM-5 nanoparticles of 150 nm with Si/Al ratio = 230 in the methanol to olefin conversion were investigated. The parent and modified catalysts showed their largest yields of ethylene and propylene at 490 °C and lower WHSV (= 3.3 h−1). The selectivity for propylene over HZSM-5 was 0.45 at 490 °C whereas it was promoted to 0.51 over Ca27-HZSM-5 (Ca/Al = 27). With decreasing temperature from 490 to 440, and 390 °C, the yield of propylene and ethylene remained nearly constant at 0.13−0.14 and 0.10−0.11 over Ca27-HZSM-5, respectively; more narrow than the corresponding range of yields for HZSM-5 (0.10−0.14 and 0.08−0.12). FT-IR results confirmed the formation of oxygenated and poly alkyl aromatic species in the carbon deposits. TG results indicated that oxygenate coke was formed and converted to heavier poly aromatic coke species with time. Increasing Ca in the porous structure of HZSM-5 may lead to heavier aromatic carbonaceous deposits. In general, Ca content positively affected activity through modification of the density, strength, and accessibility of Brønsted and Lewis acid sites. Long-term MTO activity test of HZSM-5 with Ca/Al = 27 showed stable performance over 100 h, although with an oscillatory feature.
Abstract(11) HTML(5) PDF 1850KB(1)
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Recently, the disposal of waste by beneficial and environmentally friendly methods has attracted great attention. In this work, we have studied the production of high-value carbon nanotubes (CNTs) which have remarkable applications by catalytic pyrolysis of sugarcane bagasse (SCB) as an agricultural waste using a two-stage process. Various reaction factors including the effects of zeolite catalysts (HZSM-5, HMOR, and HY), pyrolysis temperatures (450−700 °C), and SCB/ZSM-5 ratios (3−12) on SCB pyrolysis were investigated to generate CNTs from pyrolysis products. A Co-Mo/MgO catalyst was used for growing CNTs via the decomposition of pyrolysis products. The morphological structure and quality of CNTs were characterized using TEM and Raman spectroscopy, while the fresh Co-Mo/MgO catalyst was characterized by XRD and TPR analyses. The results showed that zeolite type, pyrolysis temperature, and SCB/ZSM-5 ratio had significant effects on the CNTs yield. The optimum carbon yield (24.9%) was achieved using the HZSM-5 catalyst at the pyrolysis temperature of 500 °C and with the SCB/ZSM-5 ratio of 6. TEM observations confirmed the growth of bamboo-like carbon nanotubes (BCNTs) and carbon nano-onions (CNOs) in different proportions according to the reaction parameters. Also, CNTs with the largest diameter distribution range (7−76 nm) were produced using the SCB/ZSM-5 ratio of 6. Raman spectra demonstrated the production of high-quality CNTs under all studied conditions
Abstract(8) HTML(6) PDF 1400KB(1)
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Tanning sludge, chrome tanned buffing dust and chrome shavings were selected as experimental materials. The non-isothermal distributed activation energy model (DAEM) was used to study the pyrolysis kinetic parameters. The effects of particle size and temperature on the distribution of co-pyrolysis products of various tanning wastes were investigated in a fixed-bed pyrolysis reactor, which provided a new approach for comprehensive thermal treatment of various tannery wastes. The results showed that the total activation energy required for the co-pyrolysis decreased and then increased in the range of conversion rate of 0.1 to 0.8. The tar yield decreased with raising particle size, while the yields of gas and char increased. With the increase of pyrolysis temperature, the tar yield increased rapidly to a peak value of 17% at 600 ℃, and then decreased, correspondingly the char yield decreased while the gas yield increased. When the pyrolysis temperature was 600 ℃ and the particle size of the material was 1.6–2.5 mm, the specific surface area of char was larger, and the light fractions in tar was higher. Thus the co-pyrolysis was conducive to the clean treatment of tannery wastes.
Abstract(25) HTML(8) PDF 1153KB(8)
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Since titanium silicalite molecular sieve was synthesized, its excellent catalytic oxidation performance has received the attention of scholars. Using TPAOH as the template, TEOS as the silicon source and TBOT as the titanium source, the as-prepared samples utilizing a dynamic crystallizating kettle have possessed regular morphology and the average particle size of 600 nm. By modulating the dosage of TBOT, and then changing the molar ratio of titanium to silicon in the initial synthesis solution, the effect of silicon to titanium ratio on TS-1 molecular sieve has been investigated. TS-1 zeolite properties were characterized by means of SEM、TEM、XRD、FT-IR、UV-Vis、XPS、N2 adsorption and desorption technology. Finally, using a simulated system of thiophene n-octane dissolved in octane, the catalytic oxidative desulfurization performance of TS-1 zeolite has been investigated.
Abstract(27) HTML(12) PDF 1431KB(0)
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MnOx/ZrO2-Cr2O3 catalysts was prepared by cocurrent coprecipitation and impregnation. The structure and surface properties of the catalyst were characterized by X-ray diffraction (XRD), N2 physical adsorption(BET), hydrogen programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS).These results show that the addition of Cr leads to the transformation of ZrO2 crystal form from m-ZrO2 to t-ZrO2, with the increase of Cr content, the specific surface area of the composite oxide ZrO2-Cr2O3 increased gradually, the average pore size decreased and the pore structure also changed. The impregnation of Mn caused the migration of Cr in the ZrO2-Cr2O3 composite oxide, and promoted the transformation of the ZrO2 crystal form from m-ZrO2 to t-ZrO2, the specific surface area and pore structure of the catalyst changed also. The conversion and selectivity of MnOx/ZrO2-Cr2O3 catalysts containing 4% Mn and 2.5% Cr for methyl benzoate hydrogenation were 93.86% and 86.05%, respectively.
Abstract(48) HTML(21) PDF 1863KB(11)
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The dramatic increase in atmospheric CO2 concentrations has attracted people's attention, and many strategies have been to convert CO2 into high-value chemicals. Metal–organic frameworks (MOFs), as a class of versatile materials, can be used in the CO2 capture and chemical conversion, It has unique porosity, large specific surface area, rich pore structure, multiple active centres, good stability and recyclability. Various functional nanomaterials designed and synthesized based on metal organic framework (MOF) of crystalline porous materials, It can be used as heterogeneous catalysts or carriers/precursors to address these challenges. Herein, the paper summarized the latest processes of MOFs in field of the CO2 hydrogenation to carbon monoxide, methane, formic acid, methanol and olefins, and analyzed the synthesis methods of catalysts based on MOFs and the reasons for their high catalytic activity. Besides, It made a brief introduction to improve the catalytic activity of the new MOF material and explore the feasible strategies for CO2 conversion, . Finally, the paper discussed the main challenges and opportunities of MOF-type catalysts in CO2 chemical conversion, and present a brief outlook on further developments in this research area.
Abstract(80) HTML(8) PDF 1250KB(19)
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A new Mo-Sn catalyst prepared by hydrothermal method has been used for the synthesis of dimethoxymethane (DMM) from methanol oxidation. The catalyst can achieve low temperature oxidation of methanol to DMM with high selectivity at low Mo content. The influence of Mo content on the structure and the catalytic performance of the catalyst was investigated. It was found that Mo1Sn10 catalyst showed good catalytic performance and under the conditions of 140 ℃ and atmospheric pressure, the methanol conversion was 14.2%, and the selectivity of DMM reached 88.9% without the formation of COx during the reaction process. The catalysts were characterized by XRD, Raman, FT-IR, XPS, NH3-TPD and H2-TPR. The results show that the catalysts with different Mo content have obvious differences in structure and performance. The presence of lower Mo content is more conducive to the formation of Mo5+ and MoOx, and the resulting changes in acidity and redox properties are the important reasons for the excellent performance of the catalysts.
Abstract(60) HTML(19) PDF 1025KB(3)
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Acetic acid, phenol, guaiacol and 4-methylguaiacol in the bio-oil aqueous fraction were extracted and separated experimentally with the choice of hydrophobic ionic liquid [Bmim][NTf2] as extractant. The effects of extraction time and extractant dosage on the extraction efficiency were explored. With the help of density functional theory (DFT) calculations, the interaction mechanism between [Bmim][NTf2] and phenol was also clarified. The results showed that under the optimal extraction condition (mIL/mW = 0.4, extraction time = 5 min), the extraction efficiencies of acetic acid, phenol, guaiacol and 4-methylguaiacol in the aqueous fraction were 2.71%, 95.41%, 92.04%, and 97.98%, respectively. It was indicated that [Bmim][NTf2] had better selectivity and superior extraction efficiency for phenols in bio-oil aqueous fraction. The results of the DFT calculation demonstrated that the strong hydrogen bonding interaction as well as weak vdW interaction between [Bmim][NTf2] and phenols played an important role in extraction and dephenolization of the bio-oil aqueous fraction. The phenols in [Bmim][NTf2] can be effectively removed by alkali washing treatment to achieve recovery of [Bmim][NTf2] accompanied by high extraction efficiency.
Abstract(47) HTML(14) PDF 3367KB(16)
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Accompanying with the rapid consumption of fossil fuel resources, a huge amount of CO2 has being released into the atmosphere, which brings serious environmental concerns. However, CO2 can also be considered as a clean and non-toxic carbon resource; the utilization of CO2 by converting it into various hydrocarbons can not only alleviate the greenhouse effect, but also provides a new sustainable route to produce clean fuel and chemical products. In this paper, we attempt to make a review on the recent research progresses in the hydrogenation of CO2 to certain hydrocarbons (including methane, olefins and aromatics) in recent years; in particular, the advance in the development of efficient catalysts for the hydrogenation of CO2 to methane, light olefins and aromatics as well as in the exploration of catalytic reaction mechanisms were retrospectively summarized. Lastly, we would like to have an outlook on the possible trends in the utilization of CO2 as a carbon resource through hydrogenation.
Abstract(6) HTML(1) PDF 1073KB(2)
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A novel and highly active nitrogen-doped porous carbon-supported nickel catalyst Ni@N-PC was successfully developed by a thermolysis of nickel-based zeolitic imidazolate frameworks growing on both sides of graphitic carbon nitride and used for catalyzing hydroconversion of isopropanol soluble portion from ultrasonic extraction of high-temperature coal tar (ISPHTCT). The active nickel nanoparticles were mainly encapsulated on the top of carbon nanotubes and partially dispersed on the surface of carbon nanosheets. Naphthalen-1-ol was used as a model compound to investigate the catalytic hydroconversion activity under different reaction conditions and reveal the mechanism for catalytic hydroconversion. The ISPHTCT and catalytic hydroconversion products of ISPHTCT (ISPCHCP) were analyzed with gas chromatograph/mass spectrometer. The results show that 70% of naphthalen-1-ol was converted at 160 °C and completely converted at 200 °C for 120 min, and the ISPHTCT was greatly upgraded. A total of 180 organic compounds including 33 nitrogen-containing organic compounds, 11 sulfur-containing organic compounds and 39 oxygenates were identified in ISPHTCT, while no obvious nitrogen-containing organic compounds, sulfur-containing organic compounds and oxygenates were detected in ISPCHCP, indicating the excellent performance of Ni@N-PC for heteroatom removal. All the alkenes, cyclenes and alkynes were saturated and the majority of arenes were converted to cyclanes by catalytic hydroconversion over Ni@N-PC, which exhibited high catalytic hydrogenation activity.
Abstract(18) HTML(4) PDF 1390KB(2)
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For the Fe-based catalysts in Fischer-Tropsch synthesis, the reduction and activation process of α-Fe2O3 precursor has a significant effect on the catalytic performance. As a crystalline material, the reduction and activation of α-Fe2O3 is assuredly influenced by the exposed crystal plane; however, there is a lack of necessary research in this regard. In this work, α-Fe2O3 nanocrystals of three different morphologies, viz., pseudo-cubic, hexagonal-plate and rhombohedra, were synthesized, which mainly expose the crystal planes of (102), (001) and (104), respectively. The evolution of α-Fe2O3 crystal structure was then investigated in CO atmosphere by using the Operando Raman spectroscopy (ORS). The results show that the α-Fe2O3 (001) plane has a better reductive activity in comparison to the (104) and (102) planes. The SEM, TEM, XPS and XRD characterization and DFT calculation results reveal that CO2 desorption is a decisive step for the reduction of α-Fe2O3; owing to the weak binding ability of (001) crystal plane to oxygen atoms, the desorption of CO2 on the (001) crystal plane is much easier, which can promote the reduction process.
Abstract(62) HTML(12) PDF 1247KB(17)
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A molecular modeling study based on density functional theory (DFT) and transition state theory (TST) was performed to investigate the influence of biomass gas CO on the N2O decomposition catalyzed by CaO during reburning in circulating fluidized bed boiler. The model for N2O adsorption onto the CaO(100) surfaces was constructed; and the processes of the N2O decomposition on the surface of CaO(100) and the surface recovery of CaO(100) was investigated. The results illustrate that the energy barrier of N2O decomposition on the surface of CaO(100) is much lower than the homogeneous case, and CaO is therefore able to catalyze N2O decomposition. The actomic O from N2O decomposition poisons the active site of O anion on the surface. Biomass gas CO can promote the regeneration of the active sites on the surface of CaO(100), which is beneficial for CaO to catalyze the N2O decomposition.
Abstract(31) HTML(20) PDF 1366KB(2)
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In this study, Zn-doped and Zn-Al co-doped La2O3 catalysts were prepared by citric acid sol-gel method. In situ characterization technology was used to investigate the structure-activity relationship of La2O3-based catalysts for oxidative coupling of methane (OCM). In situ XRD was conducted to detect the structural change of the La2O3-based catalysts and revealed that La2O3 crystal thermal expansion along the c-axis occurred at high temperature. Characterized by modified H2-TPR, two types of oxygen species, strong-binding oxygen and weak-binding oxygen species were found on La2O3-based catalysts. On the basis of XPS results, the strong-binding oxygen species may be anion radical O. Zn-doped La2O3 catalysts significantly increased the number of oxygen vacancies and possessed more strong-binding oxygen species, so the Zn doped La2O3 catalysts showed better OCM catalytic performance. The number of strong-binding oxygen species was enhanced significantly when the dispersion of Zn in La2O3 was promoted by co-doping of Al, the selectivity of C2+ hydrocarbons in the OCM enhanced.
Abstract(55) HTML(17) PDF 1625KB(6)
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The adsorption behaviors of CO2, CH4 and N2 on MER zeolites were investigated by Grand Canonical Monte Carlo (GCMC) simulation method. The pure gas uptake calculated in this work agreed well with available experimental data, which proved that simulation model and the COMPASS force field were reliable. On this basis, molecular dynamics (MD) simulations were carried out for diffusion and separation of CO2, CH4 and N2 on the K-MER zeolites, with the silicon MER zeolite as the reference. The results show that mean squared displacement (MSD) versus simulation time is sublinear. In MER zeolites, the configuration diffusion regime dominates as a consequence of the tight fit of the gas molecules and the zeolite pore size. The diffusion of CO2, CH4 and N2 along three-dimensional cage structures of MER zeolites is anisotropic. The gas molecules diffuse preferentially along the direction of x axis in the K-MER zeolites. Compared with the free energy between zeolite and gas molecules, zeolite extra-framework cations are the main factor affecting gas diffusion. In the K-MER zeolites, the self-diffusion coefficients of CO2 and N2 are negatively correlated with loading, the self-diffusion coefficient of CH4 increases first and then decreases with the increase of loading. The self-diffusion coefficients of CO2, CH4 and N2 all increase with the increase of temperature. The order of diffusion activation energy is N2 (16.51 kJ/mol) > CH4(8.39 kJ/mol) > CO2 (4.38 kJ/mol). K-MER zeolite membrane has good separation selectivity for gas mixture system of CO2/CH4, CO2/N2 and N2/CH4.The permeance of CO2 and N2 through K-MER zeolite membrane is as high as 104 GPU (1 GPU = 3.35 × 10−10 mol/(s/m2/Pa)).
Abstract(43) HTML(3) PDF 20402KB(9)
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The Zn-Co(OH)2 composite precursor was synthesized by using cobalt nitrate and zinc nitrate as raw materials, adding urea and sodium fluoride, and hydrothermally uniformly growing on carbon paper in a reactor at 120 ℃. CoSOH/Co(OH)2 catalytic material was synthesized by etching the precursor with 5 mol/L NaOH and 1 mol/L Na2S solution at room temperature and partially sulfided, and investigated its performance in the oxygen evolution reaction(OER) of electrolyzed water Catalytic performance. XRD, SEM, TEM, XPS were used to characterize the microstructure and physical and chemical properties of the catalyst. The results show that this method can etch the Zn component to leave oxygen vacancies and introduce doping element sulfur. The oxygen vacancies and sulfur doping play a positive role in promoting the OER reaction. In addition, amorphous CoSOH also has better OER activity. The synergy between CoSOH and Co(OH)2 makes the material show the best catalytic effect(overpotential η = 310 mV, Tafel slope b = 90 mV/dec) and long-term electrochemical stability, with high electrocatalytic production Oxygen performance.
Abstract(17) HTML(7) PDF 1102KB(0)
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TiO2 nanobelts were prepared by hydrothermal synthesis and acid treatment, then thermally treated at different temperature, and subsequently depositing Pt nanoparticles on the TiO2. Pt/TiO2 catalytic properties were investigated in the oxidation of formaldehyde. These catalysts were characterized by various techniques and the characterization results showed that the applied thermal treatment temperature greatly influenced the phase composition and surface structure of TiO2 nanobelts, as well as the number of oxygen vacancies and hydroxyl groups on the surface. The Pt/TiO2 nanobelts thermally treated at 600 °C had more oxygen vacancies, which was conducive to the activation of adsorbed oxygen, formed more Ti–(OH)x–Pt species, and showed higher catalytic activity. At 25 °C and relative humidity of 55%, the conversion of formaldehyde is 91.6%.
Abstract(24) HTML(14) PDF 1459KB(4)
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Carbon disulfide (CDS), methanol, acetone and isometric carbon disulfide/acetone mixture (IMCDSAM) were used as solvents to sequentially extract Naomaohu lignite (NL) via ultrasonic-assisted extraction to obtain extracts (E1-E4) and final extraction residue (ER). Composition and structure of the extracts in E1-E4 were analyzed by GC-MS. It was found that the main compounds in E1 were alkanes, aromatics, alcohols and esters. Alkanes, alcohols and esters are the main compounds in E2. Alcohols, phenolics and esters are the main components in E3, and esters are mainly phthalic diester compounds. Affected by synergistic effect of the two solvents CDS and acetone, the relative content of alkenes in E4 is relatively high. FT-IR was used to characterize functional groups in NL, E1-E4 and ER. Results showed that, the ultrasonic extraction process only extracts free small compounds from macromolecular skeleton of the coal and some other molecules, which connect the macromolecular skeleton by weak covalent bonds, and the process didn’t destroy the macromolecular skeleton structure. In addition, peak fitting results from FT-IR showed that the types of infrared absorption peaks in ER did not change after ultrasonic extraction, while the intensity of the peaks changed. From TG-DTG profiles of NL and ER, it can be seen that, after ultrasonic extraction, the weight loss of NL increased from 47.09% to 51.04%, and the peak of the maximum weight loss rate was advanced from 450 °C to 430 °C. Pyrolysis kinetic analysis of NL and ER based on Coast-Redfern model showed that, after ultrasonic extraction, the activation energy of ER in the rapid pyrolysis stage is lower than that of NL, and the pyrolysis process is easier to proceed.
Abstract(21) HTML(16) PDF 1160KB(3)
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A series of acid-activated montmorillonite (Acid-MMT) were prepared via Na- montmorillonite treated with nitric acid solution at different treatment temperature and time. And the Acid-MMTs used as solid acid were physically mixed with commercial Cu/ZnO/Al2O3 to prepare bifunctional catalysts for steam reforming of dimethyl ether (SRD) reaction. The results showed that the structure, texture and acidity of Acid-MMTs were significantly changed compared with Na-MMT, which was dependent on the acid treatment conditions. The structure and acidity of Acid-MMTs obviously affected the SRD performance of bifunctional catalyst. The bifunctional catalyst composed with the Na-MMT activated in 20% nitric acid solution at 80 °C for 12 hours (Acid-MMT-80/12) and Cu/ZnO/Al2O3 exhibited the best SRD performance, i.e., the dimethyl ether conversion and H2 yield reached 97% and 94% under the conditions of p = 0.1 MPa, t = 350 °C, GHSV = 3000 h−1, respectively, and DME conversion and H2 yield remained basically constant in 10 hours, which indicated the catalyst had good stability.
Abstract(29) HTML(27) PDF 1087KB(5)
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To obtain type II active phase with higher activity, MoS2 based catalysts were prepared by thermal decomposition of ammonium tetrathiomolybdate. The influence of Ni adding method and decomposition atmosphere on the microstructures of MoS2 slabs, chemical state of surface elements, as well as hydrodesulfurization and hydrodenitrogenation activities have been comparatively investigated and studied detailly. Results indicated that simultaneous impregnation of Mo and Ni sources caused in situ deposition of amorphous NiMoS4 over the support surface, which subsequently facilitated the substitution of Mo atoms by Ni atoms at MoS2 edges. Accordingly, these decorated catalysts exhibited higher dispersion of MoS2 slabs and more suitable slab length (3−5 nm) and stacking number (2−4), which attributed to a larger number of rim and corner active sites exposed at the edges. These active sites were active in hydrogenation and hydrogenolysis reactions. In comparison with N2 atmosphere, thermal decomposition in H2 atmosphere was more favorable for the substitution of Mo atoms by Ni atoms at MoS2 edges, which provided more active Ni−Mo−S structures. Hence, the adsorption, activation and hydrogenation of quinoline and dibenzothiophene molecules were enhanced. The catalyst prepared by thermal decomposition of NiMoS4 in H2 atmosphere showed superior activities in the quinoline hydrodenitrogenation where quinoline conversion reached 23.8%, and in the dibenzothiophene hydrodesulfurization where dibenzothiophene conversion acquired 93.3% accordingly, under the condition of 340 ℃ and 3 MPa of H2 atmosphere, with a weight hourly space velocity of 23.4 h−1, H2/oil volume ratio of 600 and 0.1 grams of NMS-H2 catalyst.
Abstract(54) HTML(15) PDF 1399KB(15)
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Mosaic coke is a kind of special artificial carbon material, which is usually used as the raw material to produce high-quality nuclear graphite. The quality of graphite has been usually focused on the properties of mosaic cokes. In order to investigate the influence on the contents of heavy-phase pitch and the micro-structure and properties of mosaic coke, 9 kinds of heavy-phase pitches with varied QI contents have been used as the raw materials to produce series of mosaic cokes in this study. Optical micro-scope, Scanning electronic micro-scope, X-ray diffraction, Raman spectrum and curve-fitted methods have been used to judge the micro-structure of 9 kinds of mosaic cokes. Also, the micro-strength of mosaic cokes has been determined. The results showed that, the higher contents of QI in heavy-phase pitch made the mosaic structure easier to produce during the liquid-phase carbonization process. What’s more, with the increase of QI content, the content of regular carbon microcrystals has been decreased, but the content of amorphous carbon and micro-strength have been improved. When the QI contents in the heavy-phase was higher than 7%, the derived mosaic cokes have the total contents of mosaic structure (the sum of fine mosaic structure, medium mosaic and coarse mosaic) rather than 82%, and the micro-strength was also higher than 85%. In other words, the heavy-phase pitch with the content of QI higher than 7% is a promised raw material to produce high-quality mosaic coke.
Abstract(35) HTML(26) PDF 2077KB(4)
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The LaCoO3/CeO2/cordierite, LaCoO3/γ-Al2O3/cordierite, LaCoO3/SiO2/cordierite monolithic catalysts were synthesized by the suspension coating method and sol-gel method in two steps using cordierite honeycomb ceramic as the substrate and nano-oxides (CeO2, γ-Al2O3, SiO2) as the coating carrier. The phase, microscopic morphology, element composition, redox property, adhesion strength, and texture properties of the samples were characterized and analyzed by XRD, SEM, XPS, H2-TPR, UT and N2 adsorption-desorption techniques. The catalytic activity, high-temperature stability, shutdown/restart cycle stability, and water vapor stability of the monolithic catalyst were evaluated through the catalytic combustion performance of VOCs. Experimental results show that three catalysts exhibit good catalytic activity and stability, and the type of coating can cause a difference in catalytic performance. Among three cattalysts, the LaCoO3/CeO2/cordierite catalyst has the best performance. When the volume fraction of toluene is 0.1% and the space velocity is 18000 mL/(g·h), the tempereratures for the conversion rates of 50% and 90% are 158 and 214 ℃, respectively. The toluene conversion rate is only reduced by 7% after 72 h of stability testing (high temperature, stop/restart cycle, water vapor). Characterization results show that the CeO2 nano-coating helps to form a catalytic layer with a porous and fluffy structure, which makes the catalyst have a higher ratio of adsorbed oxygen, strong low-temperature reducibility and good adhesion.
Abstract(25) HTML(9) PDF 1515KB(1)
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Chemical looping methane reforming is a potential route to co-produce syngas and hydrogen by using the oxygen carrier (metal oxide). The oxygen carrier CeO2/LaFeO3 was prepared by sol-gel method, and the structure and oxygen supply capacity of the oxygen carrier were analyzed by X-ray powder diffraction and hydrogen temperature programmed reduction. The influence of CeO2 ratio and reaction temperature on the performance of the oxygen carrier were discussed through fixed bed reaction tests. The content of CeO2 had a significant effect on the oxygen supply capacity of the oxygen carrier. Increasing reaction temperature was not only conducive to methane activation, but also could enhance lattice oxygen migration in the oxygen carrier. A suitable reaction temperature could match methane activation with lattice oxygen migration, thereby improving the selectivity of the oxygen carrier. Experimental results showed that performance of the oxygen carrier was in the optimal when CeO2 content was 10% and reaction temperature was 850 ºC. CH4 conversion rate could reach 94%, H2 selectivity and CO selectivity could reach 90% and 83%, respectively. The oxygen carrier 10%CeO2/LaFeO3 could maintain stable reaction performance and structure in the redox cycles.
Abstract(40) HTML(9) PDF 2578KB(6)
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A series of modified FER zeolite samples with different acid types, acid density and accessibility were prepared by using different concentrations of ammonium hexafluorosilicate(AHFS) for isomorphous substitution. The texture properties were characterized by XRD and N2 adsorption isotherms. And the acid properties were characterized by NH3-TPD and Py-FTIR. The results showed that when 1-butene and isobutene were respectively used as raw materials, the optimal reaction temperature for skeleton isomerization was 350 °C , and the side reaction was more obvious when isobutene was used as raw material. During the dealumination process, two new Lewis acid sites with different strength were generated, due to the interaction between the dealumination agent and the extra framework aluminum hydroxyl species on the zeolite. During the reaction, the above two Lewis acid sites promoted the oligomerization-cracking of isobutene, thereby, reducing the selectivity of the main reaction.
Abstract(50) HTML(12) PDF 2085KB(5)
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The utilization of carbon dioxide as a resource through electrocatalysis is one of the ideal ways to alleviate or solve the current ecological crisis mankind facing. The development of inexpensive and efficient catalysts is the key to promoting the industrialization of electrocatalytic carbon dioxide reduction. CO is an important industrial raw material, as a result, CO2 reduction to CO has important research significance. However, high-active noble metal catalysts that can convert CO2 to CO are difficult to apply in large scale. Zn-based catalysts are potential substitutes. However, the reduction activity of Zn-based catalysts still can not meet the actual needs. In this paper, ZnOHF material is employed in the electrocatalytic CO2 reduction for the first time. ZnOHF nanorods of different sizes are prepared through a simple hydrothermal synthesis method and tested in a Flow-cell. The large specific surface area of the nanorods and the existence of F atoms on the surface of the material lead to good catalytic activity. The Flow-cell accelerates the reaction mass transfer process. At -1.28V (vs. RHE), the R2-ZnOHF nanorods have the highest CO Faraday efficiency of 76.4% with the CO current density of 57.53 mA/cm2.
Abstract(67) HTML(18) PDF 3181KB(10)
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In order to obtain the mechanism of the effect of CO2 on the NO heterogeneous reduction, density functional theory (DFT) was adopted to investigate the interactions between char and NO with the participation of CO2. The armchair configuration composed with several aromatic ring clusters was selected as the carbonaceous surfaces. Geometric optimizations were carried out at the B3LYP-D3/6-31G(d) level. Energies of optimized geometries were calculated at the B3LYP-D3/def2-TZVP level. The results show that, the surface carbonyl groups produced by the adsorption of CO2 combine with the adsorbed NO to desorb CO2, thereby providing adjacent carbon active sites for subsequent NO adsorption and N2 desorption. Thermodynamic studies show that the exothermic heat of this reaction is 853.9 kJ/mol, and the highest energy barrier is 297.0 kJ/mol without the participation of CO2, but the exothermic heat of this reaction is 593.7 kJ/mol, and the highest energy barrier is 214.1 kJ/mol with the participation of CO2. Kinetic studies show that over the temperature range of 298.15–1800 K, the reaction rate constants of rate-limiting steps are calculated with conventional transition state theory. The rate constant with the participation of CO2 is higher than that without the participation of CO2. In summary, CO2 plays a promoting role in interacting with NO and char and reducing energy barrier to form N2 directly.
Abstract(49) HTML(33) PDF 2012KB(11)
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With H2WO4 and EDA as precursors, the WO3/C intermediate is obtained by mechanical stirring and in-situ solid-phase pyrolysis, and then WS2/C composite material is obtained by high temperature vulcanization. Characterize the structure and morphology of the prepared WS2/C composite material by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS)and other instrumental analysis methods . At the same time, the electrocatalytic steady-state polarization curve (LSV), Tafel slope (Tafel), cycle stability (CP), electrochemical impedance (PEIS) and Electrochemically Active Surface Area (ECSA) tests were performed on the material, and the electrocatalytic performance of the catalyst was analyzed. The results show that when the current density of the WS2/C composite is 10 mA/cm2, the overpotential is 179 mV, and the Tafel slope is 98 mV/dec.
Abstract(47) HTML(7) PDF 1067KB(5)
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The ZIF-8/Pt/SiO2 catalyst was prepared by combining atomic layer deposition technology and vapor phase conversion method. The Pt metal nanoparticles were deposited on SiO2 nanowires, and the ZIF-8 film covers Pt and SiO2 nanowires to form a sandwich structure. The structure of the catalysts was characterized by XRD, TEM, BET, IC-MS, XPS and CO-DRIFT, and the function of ZIF-8 film were studied by using the semi-hydrogenation of 1-heptyne as the probe reaction. The Pt particles are highly dispersed on the SiO2 nanowires before and after the ZIF-8 overcoating, and the ZIF-8 film coats continuously on the entire catalyst with high conformity. The ZIF-8 film induces an electron density increase of Pt surface and increase the olefin selectivity from 14% to 70% in the 1-heptyne hydrogenation reaction. A thinner ZIF-8 film increases the catalytic activity, and cannot change the selectivity of olefin.
Abstract(76) HTML(22) PDF 1306KB(4)
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The Fe3O4 loaded ceramic composite microwave absorbents were successfully prepared by recycling the solid waste coal gangue. First, the coal gangue based matrix was obtained by crushing, ball-milling, acid pickling, granulation and sintering process, and then the subsequent experiment involved loading precursor solution as well as in-situ carbothermal reduction. Moreover, the influence of Fe3O4 loading content on the microstructure and electromagnetic performance was also investigated. It was founded that the ceramic composites exhibited excellent microwave absorption when the reduction temperature kept 600 °C and the concentration of precursor solution was 1.25−1.5 M, under which the minimum reflection loss value reached −20.1 dB and the effective absorption bandwidth kept 4.7 GHz as the coating thicknesses was 2.0 mm. This was attributed to the better impedance match and attenuation characteristic. The simple technological process provided in this work could offer a novel method for the recycling of coal gangue, and was beneficial for the low-cost of microwave absorbents.
Abstract(54) HTML(7) PDF 1198KB(3)
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Low-cost and high-performance catalyst is crucial for hydrogen generation via the hydrolysis of ammonia borane (NH3BH3, AB) as a chemical hydrogen storage material. In this work, Co-CeOx nanocomposites supported on graphene (Co-CeOx/graphene) were prepared through a facile impregnation and chemical reduction method and used as a catalyst in the hydrolytic dehydrogenation of ammonia borane. The results indicate that the as-prepared Co-CeOx/graphene nanocomposite exhibits superior catalytic activity and recycling stability in the hydrolysis of ammonia borane, owing to the ultra-fine size of Co-CeOx particles, the strong synergistic electronic effect between Co and CeOx, as well as the strong metal-support interaction between Co-CeOx and graphene. For the hydrolysis of ammonia borane over the optimized Co-CeOx/graphene catalyst, the turnover frequency (TOF) reaches 45.1 min−1, with the activation energy (Ea) of 39.5 kJ/mol; such a TOF value is 12 times and 9 times higher than those over Co and Co/graphene, respectively, also much higher than those reported for most noble-metal-free catalysts.
Abstract(31) HTML(9) PDF 820KB(5)
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Conversion of cellulose and starch to furfural was investigated over four zeolites. The zeolites were characterized by X-ray diffraction, 27Al MAS NMR, IR spectra of pyridine adsorption and NH3 temperature-programmed desorption. The roles of acidity and pore structure of zeolites in conversion of cellulose and starch were discussed in detail. The results showed that Hβ zeolite with appropriate Brønsted acid sites, Lewis acid sites and pore structure was effective to produce furfural from cellulose and starch. HY zeolite could not catalyze cellulose reaction with high conversion because of its weak acidity. However, HY zeolite was effective to produce 5-hydroxymethylfurfural (HMF) from starch. H-mordenite and HZSM-5 zeolites with fewer Lewis acid sites could not cause the isomerization reaction from glucose to fructose. So, the further conversion of fructose to furfural or HMF was inhibited. The formation of HMF only depended on the acid properties of zeolites. The formation of furfural was not only determined by the acidity of zeolites, but also by their appropriate pore structure.
Abstract(87) HTML(14) PDF 1436KB(8)
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In recent years, metal-organic frameworks (MOFs) have gradually been used in the field of oxygen evolution reaction (OER). In order to improve OER performance, MOFs are usually used as precursors to prepare metal oxide/porous carbon composites by pyrolysis at high temperatures in previous studies. Although metal oxide/porous carbon composites show high catalytic activity, they require complicated preparation processes and high temperature. Therefore, it is very significant to find a highly efficient MOFs, which can be directly used as OER without pyrolysis treatment. The results show that when Co-ZIF-67/NF, Ni-MOF-74/NF and Fe-MIL-101/NF are used as OER catalysts in 1 mol/L KOH solution, 377, 383 and 272 mV overpotentials are required to make the current density achieve 10 mA/cm2. The charge transfer resistance (Rct) of Fe-MIL-101/NF is 1.53 Ω, which is smaller than that of Co-ZIF-67/NF (32.40 Ω) and Ni-MOF-74/NF (43.78 Ω). Therefore, the higher of the Rct of the catalyst, the smaller of the charge transfer capacity in the OER process. Thus, the fast charge transfer rate is the main reason for the excellent OER activity of Fe-MIL-101/NF. In addition, the OER activity of Fe-MIL-101/NF (272 mV) without pyrolysis treatment is much higher than that of commercial RuO2/NF (302 mV), indicating that MOFs with fast charge transfer rate can be used as an efficient catalyst for OER without calcination.
Abstract(18) HTML(3) PDF 1230KB(6)
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Nanocatalysis is facing a technological revolution, which puts forward higher requirements for the accurate control of the size distribution and morphology of metal nanoparticles. Atomic layer deposition (ALD) is proposed as solution to this problem because of its character of accurate controlling metal distribution on atomic level. In this review, the development history, deposition mechanism as well as equipment and technology are summarized. Subsequently, the substrate types and microstructure of obtained catalysts are discussed. In particular, the latest progress of the synthesis and application of metal catalysts prepared by ALD are highlighted. Lastly, the challenges and prospects in ALD are illustrated.
Abstract(64) HTML(8) PDF 1004KB(16)
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Metal-based zeolite catalysts are widely-used in the NH3 selective catalytic reduction (NH3-SCR) reactions due to their wide temperature window and good hydrothermal stability. In this review, the research progress, structural characteristics and catalytic performance of Cu- and Fe- based zeolite catalysts in NH3-SCR were summarized. In addition, the application of density functional theory (DFT) in NH3-SCR reaction mechanism is introduced. Finally, the study methods of reaction kinetics on catalysts has been described, and the typical apparent kinetic parameters under different metal-based zeolite systems were compared and discussed. Hopefully, this review could provide methods and ideas for the further study of NH3-SCR reaction mechanism over metal-based zeolite catalysts.
Abstract(43) HTML(15) PDF 2107KB(8)
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Two gas coals were respectively separated into four components with different vitrinite content using ZnCl2 solution. The carbon structure, composition of coal macerals and minerals, and plastic layer behavior of separating components were characterized by nuclear magnetic resonance spectrometer (13 CNMR), Coal rock analyzer, X-ray fluorescence spectrometry (XRF) and Gieseler fluidity. Combining with X-ray photoelectron spectroscopy (XPS), the effect of different gas coal separation components on the sulfur transformation behavior during pyrolysis of high-sulfur coal and distribution of sulfur forms in coke was investigated. The results show that with the increase of vitrinite content in gas coal, the relative ratio of aliphatic carbon in coal increases, and the release amount of volatiles increases during pyrolysis, the hydrogen free radicals in volatiles promote the decomposition of sulfur, stabilize the sulfur free radicals in time and release as sulfur-containing gases, the sulfur content in coke is thus reduced. Low density components in gas coal have the largest maximum fluidity and widest plastic range, and the stability of plastic layer is the best in the process of co-pyrolysis with high sulfur coal. The basic minerals in gas coal are mainly enriched in the high density components, which leads to the increase of sulfide sulfur and sulfate sulfur in the coke. For the utilization of gas coal in coal-blending pyrolysis, the enrichment of vitrinite, and the selection of coals with easier removal of alkaline minerals are beneficial to the reduction of sulfur in coke.
Abstract(61) HTML(15) PDF 1814KB(2)
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In this work, a rod-shaped Al2O3 with high specific surface area and rich in unsaturated pentahedral coordination Al3+ sites was synthesized by hydrothermal crystallization method, and the tungsten species was anchored on the surface of the Al2O3 support in the form of oligomeric nanoclusters using the incipient-wetness impregnation method. Then the platinum species are in close contact with the tungsten species in the form of small particle size and high dispersion through high temperature heat treatment. It greatly enhances the degree of interaction between platinum and tungsten species, is conducive to the generation of more active site structures, and significantly improves the catalytic activity of glycerol hydrogenolysis to 1,3-propanediol (1,3-PDO). In a fixed-bed reactor, when the reaction temperature is 160 ℃, the pressure is 5.0 MPa, and the 10 wt% glycerol aqueous solution is continuously fed into the liquid, the catalytic reaction performance evaluation results show that the glycerol conversion of the Pt-WOx/Al2O3 catalyst is 75.2%, and the yield of 1,3-PDO reached 33.1%.
Abstract(33) HTML(9) PDF 820KB(6)
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Three agricultural residues (peanut straw, sorghum stalk and reed) were first pretreated by water washing, and then pyrolysis experiments were carried out using a fixed bed reactor. The work is purposed to investigate how the pyrolysis characteristics are changed in relation to the removal of alkali earth metals (AAEMs) and a part of fibrous components by water washing. It was found that the water washing removed 52.7−92.6% potassium and approximately half of neutral detergent solute (NDS) from three agricultural residues. The removal of AAEMs and NDS exerted twofold influences on the pyrolysis of agricultural residues, and this effect was more remarkable for peanut straw duo to its higher contents of both AAEMs and NDS. The removal of AAEMs had an inhibitory effect on the reactions such as decarboxylation, decarbonylation, dehydrogenation and polycondensation, whereas the elution of NDS directly affected the yields and composition of gas and liquid products. For all three agricultural residues, overall, the water washing was favorable to the promoted production of bio-oil and bio-char, while the gas yield was lowered. The bio-oils generated from the water-washed agricultural residues had higher proportions of oxygenates, especially sugars and furans, with lower proportions of hydrocarbons and nitrogenous compounds. By water washing, peanut straw yielded less CO2, CO and CH4, opposite to an increase in long-chain fatty acids.
2021, 49(8): 1-8.
Abstract(15) HTML(4) PDF 2917KB(11)
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2021, 49(8): 1057-1076.   doi: 10.1016/S1872-5813(21)60093-2
Abstract(150) HTML(37) PDF 1125KB(25)
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Waste gasification has the potential to contribute to China’s transition towards carbon neutrality and zero waste cities via the recirculation of waste as secondary carbon feedstock for the production of chemicals with lower/and or zero carbon footprint, green hydrogen with zero carbon footprint and CO2-neutral synthetic liquid fuels. With China’s significant coal gasification capacity and associated experiences and expertise, Coal-to-X could act as a bridge to Waste-to-X for carbon intensive sectors such as the waste management, chemical production and mobility sectors. To illustrate the opportunities in these areas, this article presented highlights from dynamic global developments in waste gasification, focusing on pioneering industrial developments in Germany between 1980−2000’s as well as current international developments. Lessons learnt from previous and current waste gasification project deployment are shared and enabled the identification of problems which will have to be addressed in the transition from coal gasification towards mono-waste gasification technologies. Additionally, a qualitative evaluation of gasification technologies pointed to the strengths and weaknesses of fixed-bed, fluidized-bed and entrained-flow gasification principles in their application for waste gasification.
2021, 49(8): 1077-1085.   doi: 10.19906/j.cnki.JFCT.2021048
Abstract(72) HTML(27) PDF 932KB(14)
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During the direct coal liquefaction process, coal direct liquefaction residue (CDLR), which accounts for about 30% of the coal input, will be produced and the polycyclic aromatic hydrocarbons can be extracted from it by extraction to prepare high-value carbon materials. The influences of composition and structure of extractants on the extraction rate and properties of extracted products were systematically summarized. The extraction rate of the extractants which have aromatic structure or nitrogen and oxygen atom can reach more than 50%. The extracts in alkane organic solvents mainly contain condensed aromatic structure with 2–4 benzene rings and have a lower molecular weight and heteroatom content. The extracts in heteroatoms containing solvents are mainly composed of condensed aromatic structure with 4–7 benzene rings and have a larger molecular weight. And they are rich in heteroatoms, such as nitrogen, oxygen and sulfur, and have a high atomic ratio of C/H. The extracts of pyridinium-based ionic liquids have higher atomic ratio of C/H and aromaticity. And the ash content of the extracts of ionic liquids containing organic acid ions is close to 0. When coal liquefaction oil or coal tar distillate are used as extractants, the extraction rate can reach 60%, which are suggested for industrial applications of CDLR extraction.
2021, 49(8): 1086-1094.   doi: 10.1016/S1872-5813(21)60074-9
Abstract(268) HTML(13) PDF 1881KB(9)
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Pyrolysis is an effective way for clean and efficient use of coal, as well as an important way for the efficient conversion of waste plastics. Polyvinyl chloride (PVC) and Pingshuo (PS) coal were used in this research object. A two-step treatment scheme was proposed for chlorine-containing plastics that are difficult to be treated harmlessly. The PVC was preheated to remove most of the chlorine, and then the pretreated PVC residue (DPVC) and coal were co-pyrolyzed. GC, simulated distillation, GC-MS, elemental analysis, FT-IR and Raman spectroscopy were used to analyze and characterize the composition and properties of pyrolysis gas, tar and char. The results showed that the co-pyrolysis process of DPVC and PS coal has a synergistic effect, and the co-pyrolysis has an obvious positive synergistic effect on the formation of char and tar. The experimental value of tar yield is higher than theoretical calculation and the maximum increasing value is 3.35%. There is a negative synergistic effect on the formation of pyrolysis water and gas, in which CH4 has the largest decrease in yield, meaning the strongest negative synergy. Co-pyrolysis increases the content of light tar, significantly increases the content of naphthalenes, and reduces the asphalt. When the DPVC addition was 10%, the content of light tar increases by 5 percentage points over the theoretical calculation value. In addition, the co-pyrolysis char surface is smoother, the structure becomes more orderly, and the graphitization degree increases.
2021, 49(8): 1095-1101.   doi: 10.1016/S1872-5813(21)60081-6
Abstract(81) HTML(18) PDF 1350KB(12)
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In order to study the performance of DCLR (direct coal liquefaction residue) modified asphalt mortar, different DCLR modified asphalt mortar with different DCLR contents and filler-asphalt ratios (FA) was prepared. The high-and-low temperature and fatigue performance of asphalt mortar was analyzed by a dynamic shear rheometer and a bending beam rheometer. Using the variance analysis method the influence of the single factor (temperature, DCLR content, FA) and the coupling between these factors on the performance of asphalt mortar was investigated. The results show that the addition of DCLR and filler can significantly improve the high-temperature performance of asphalt mortar, but damage the low-temperature performance and the fatigue performance of asphalt mortar. To comprehensively balance the effects of DCLR content and FA on the performance of the mortar, the DCLR content of 10% and the FA of 1.0 are recommended. Besides, the single factor (temperature, DCLR content, FA) and the coupling between these factors have significant effects on the performance of asphalt mortar, but the effect of the coupling is smaller than that of the single factor.
2021, 49(8): 1102-1110.   doi: 10.19906/j.cnki.JFCT.2021051
Abstract(50) HTML(17) PDF 1830KB(5)
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8 kinds of mixed oil with different feeding time in the same coking cycle were the objects of the study. The optical structure, morphology structure and microcrystalline structure of needle coke formed by mixed oil with different feeding time in coking cycle were quantitatively analyzed by means of polarizing microscope, scanning electron microscope (SEM), XRD and Raman spectroscopy. The results show that the yield of coke after the thermal conversion of the mixed oil is higher than the theoretically calculated yield, indicating that the heavy oil participates in the thermal conversion reaction to form the coke with a streamlined optical structure. In the optical structure of calcined needle coke, MO-8" has the highest fiber content, followed by MO-16", and MO-32" has the lowest fiber content. SEM further proves that MO-8" has more lamellar number and more regular orientation. XRD analysis of needle coke confirms that the microcrystalline structure parameters (interlayer spacing d002, lamellar content N and the number of carbon atoms in each layer n) are very close. However, there are obvious differences in the content of graphite microcrystalline (Ig), and among which MO-8" has the highest content, followed by MO-4", and sample MO-32" has the lowest content. Furthermore Raman spectral analysis certifies that the basic microstructure of needle coke is similar. The fundamental reason is that the refined coal-tar pitch in the mixed oil determines the basic microstructure of needle coke. Due to the continuous circulation of heavy oil in the system, the microstructure of needle coke are different. Hence, the coking cycle is not easy to exceed 32 h in coal-based needle coke production, or else it will seriously affect the microstructure of needle coke.
2021, 49(8): 1111-1121.   doi: 10.1016/S1872-5813(21)60064-6
Abstract(99) HTML(66) PDF 1496KB(23)
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The effects of steaming at varying times and temperatures on ZSM-5 pore structures, framework Al distribution, acid properties and ethanol to propene (ETP) catalytic performance were systematically studied in this study. The results show that the crystallinity and specific surface areas of steam treated ZSM-5 samples decrease with the increase treatment time and temperature. 27Al MAS NMR and Co(Ⅱ) exchange-ICP results show that the isolated framework Al species (Alsingle) can be preferentially removed from the zeolite framework, while the paired Al sites (Alpairs) remain relatively stable after steam treatment. The characterization of Py-IR reveals that the concentration of B acid sites and the acid strength are all declined with the steaming time or temperature increase. The catalytic results of ETP at 450 ℃ show that the sample after steaming gives improved selectivities to propene and butene at the expense of ethene conversion and alkanes selectivity relative to the unmodified zeolite. Besides, a good positive correlation between ethylene conversion and Alsingle concentration is found, whereas the propene formation is influenced by the combination effect of Alsingle and Alpairs sites.
2021, 49(8): 1122-1131.   doi: 10.1016/S1872-5813(21)60124-X
Abstract(47) HTML(7) PDF 10230KB(10)
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The reaction mechanism of the isomerization of glucose to fructose and further dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) in subcritical water was investigated by the dispersion-corrected density functional theory (DFT-D) method with Dmol3 package in Materials Studio. The implicit solvent model was used to evaluate the bulk solvation under the conductor-like screening model (COSMO) approach, in which a dielectric constant ( ε ) of 27 was used to represent the subcritical water at 523.15 K. The explicit solvent model was adopted with a hybrid micro-solvation-continuum approach, to indicate the micro-solvation by explicit H2O molecules and the bulk solvation with ε = 27. The calculation results indicate that explicit H2O molecules participate in the reaction and catalytically promote the proton transfer processes, suggesting that the explicit solvent model is preferable to the implicit solvent model to represent the conversion of 5-HMF in subcritical water. The isomerization of glucose to fructose is exothermic by 5.26 kcal/mol, where the isomerization of open-chain glucose to enol form is the rate-determining step, with the activation energy of 33.89 kcal/mol; the free energy of transition state configuration depends upon both the difficulty in α–H extraction of open-chain glucose and the stability of formed carbocation. In contrast, the hydration of fructose to 5-HMF is exothermic by 12.93 kcal/mol and the first hydration is the rate-determining step, with the activation energy of 50.59 kcal/mol; the free energy of transition state configuration is determined by the stability of carbocation formed by the dehydration of protonated OH group at C(2) site of fructose. This work discloses the promoting effect of Brønsted base on the isomerization of glucose to fructose and that of Brønsted acid on the dehydration of fructose to 5-HMF, which may provide certain clues to the modification of catalytic sites and the selection of solvent in the conversion of glucose to 5-HMF.
2021, 49(8): 1132-1139.   doi: 10.1016/S1872-5813(21)60057-9
Abstract(75) HTML(48) PDF 1256KB(11)
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Highly selective synthesis of liquefied petroleum gas (LPG, ${\rm{C}}_3^0$ and ${\rm{C}}_4^0$) from CO2 hydrogenation have realized over the In2O3/SSZ-13 bifunctional catalyst. The physicochemical properties of the bifunctional catalyst were characterized by X-ray diffraction spectroscopy (XRD), N2 physical adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and NH3 temperature-programmed desorption (NH3-TPD). The particle size effect of In2O3 and reaction conditions were investigated for CO2 hydrogenation to LPG over the In2O3/SSZ-13 bifunctional catalyst. Results indicate that CO2 conversion and CO selectivity are related to the particle size of In2O3, and fresh 5 nm In2O3 shows the highest CO2 conversion (11.7%) and the highest CO selectivity (61.0%), since it is more prone to reverse water gas reaction (RWGS). However, the hydrocarbon distribution does not exhibit a dependence of In2O3 size changes, and the selectivity of LPG maintains at 90% and the selectivity of propane reaches up to 76.8% due to the 8-MR micropores and strong acid sites of SSZ-13 zeolite. Additionally, the yield of LPG shows a volcano type with increasing reaction temperature, and the optimal reaction temperature is 370 ℃. Low space velocity is more favorable to the CO2 conversion, and LPG selectivity in hydrocarbon products still maintains about 90%. High reaction pressure is beneficial to improving the yield of LPG via promoting the secondary hydrogenation reaction over the SSZ-13 zeolite and inhibiting CO formation. Furthermore, no obvious deactivation is observed after a time on stream (TOS) of 100 h over the In2O3/SSZ-13 bifunctional catalyst at 350 ℃, 3 MPa and 9000 mL/(gcat·h). The research provides a new strategy for highly selective synthesis of LPG from CO2 hydrogenation.
2021, 49(8): 1140-1147.   doi: 10.19906/j.cnki.JFCT.2021050
Abstract(54) HTML(12) PDF 902KB(7)
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High thermal conductivity supports, core-shell structure SiO2@Al, was successfully prepared by hydrolyzing tetraethyl orthosilicate (TEOS) under weak alkaline condition and using hexadecyl trimethyl ammonium bromide (CTAB) as the template. 15% (mass fraction) of cobalt was loaded on these supports by excessive impregnation method for Fischer-Tropsch synthesis reaction. The prepared catalysts have high metal aluminum content, high specific surface shell layer and relatively uniform pore size of 2.6−2.8 nm. By changing the added amount of TEOS, the content of silica in the supports and the thickness of the shell layer can be adjusted. As the thickness of the silica shell layer increases, the specific surface area of the supports gradually increases, the interaction between cobalt and the supports increases, and at the same time, the reduction degree of the catalysts decreases. The silica shell enhances the dispersion of metallic cobalt and avoids deactivation caused by agglomeration of metallic cobalt on aluminum particles. Under the condition of similar conversion rate, the catalyst 15Co/5-SiO2@Al with a thinner shell layer has the best performance in Fischer-Tropsch synthesis which is mainly due to the moderate metal-support interaction between the thin silica shell layer and metal cobalt particles. The thinner silica shell layer can anchor and disperse cobalt species to increase the reduction degree of cobalt species.
2016, 44(7): 777-783.
[Abstract](54) [FullText HTML](15) [PDF 2169KB](2)

2016, 44(4): 385-393.
[Abstract](58) [FullText HTML](39) [PDF 1138KB](5)

2016, 44(3): 263-272.
[Abstract](31) [FullText HTML](21) [PDF 1275KB](1)

2016, 44(7): 801-814.
[Abstract](75) [FullText HTML](39) [PDF 8665KB](11)

2016, 44(11): 1388-1393.
[Abstract](52) [FullText HTML](38) [PDF 780KB](0)

2016, 44(3): 279-286.
[Abstract](55) [FullText HTML](26) [PDF 12189KB](0)

2016, 44(6): 732-737.
[Abstract](37) [FullText HTML](15) [PDF 2776KB](1)

2016, 44(9): 1034-1042.
[Abstract](42) [FullText HTML](16) [PDF 809KB](0)

2017, 45(1): 113-122.
[Abstract](38) [FullText HTML](21) [PDF 1085KB](1)

2018, 46(2): 179-188.
[Abstract](34) [FullText HTML](7) [PDF 7028KB](2)

2013, 41(08): 1003-1009.
[Abstract](2033) [PDF 13334KB](0)
Abstract:
A core-shell catalyst CuO-ZnO-Al2O3@Al2O3 for one-step synthesis of dimethyl ether from synthesis gas was prepared using glucose, sucrose or starch as template, and characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The thickness of the Al2O3 shell in the catalyst was altered by controlling the synthesis condition, such as temperature and time. The catalytic performance of dimethyl ether (DME) synthesized from CO hydrogenation on the catalysts were investigated. The conversion of CO and the selectivity of DME on CuO-ZnO-Al2O3@Al2O3 achieved 35.2% and 61.1% at 260 ℃, 5.0 MPa and 1 500 mL/(h·gcat), respectively.
2009, 37(04): 501-505.
[Abstract](1493) [PDF 0KB](7)
Abstract:
The properties of pyrolysis and combustion for five different sewage sludges are studied by thermal gravimetric analysis at a heating rate of 10℃/min in the atomosphere of nitrogen and oxygen, respectively. The results show that both of the “anaerobic” wastewater treatment and the sludge anaerobic digestion make the organic compounds in sludge so complicated that the organic compounds decomposition and release temperature becomes higher during pyrolyzing, and the “aerobic + anaerobic” process makes the organic compounds in sludge more complicated than the “anaerobic +aerobic” process. There is no influence on the combustion process and the burnout point, but can make the combustion temperature of sludge higher. The thermal reaction mechanisms have been studied with šatava-šesták equation. It shows that the pyrolysis mechanism of these sludges is a process of volatile diffusion at first and then the chemical reaction function, while the combustion mechanism of them is a process of chemical reaction and diffusion function.