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Abstract(20) HTML(18) PDF 1837KB(4)
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Torrefaction atmosphere is one of the key problems in industrial application of torrefaction technology. In this paper, the effects of oxygen concentration and torrefaction temperature on the physicochemical properties of rice straw during oxidative torrefaction were investigated by simulating the atmosphere of oxy-fuel combustion flue gas. The results show that the effect of temperature on oxidative torrefaction is more significant compared with oxygen concentration. At low temperature (< 250 ℃), oxygen concentration has little effect on the mass and energy yield of torrefied rice straw, but it has obvious effect at high temperature (> 250 ℃). With an increase of temperature (> 250 ℃), the mass and energy yield of torrefied rice straw decreased significantly. When the temperature and oxygen concentration are 250 ℃ and 6%, respectively, it is a suitable oxidative torrefaction condition. Under this condition, the mass and energy yield of torrefied rice straw can be maintained above 70% and 80%, respectively. Increasing the temperature mainly enhances the torrefaction reaction, and the oxidation reaction has an obvious effect when the oxygen concentration exceeds 6%. The retention ratio of chlorine and potassium showed an downward trend with the increase of temperature and oxygen concentration, but the effect of increasing temperature was more significant.
Abstract(54) HTML(17) PDF 1280KB(11)
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The characteristics of pelletized cyanobacteria pyrolysis and gasification during chemical looping process with red mud oxygen carrier was investigated in the present work. The objective is to evaluate the influence of red mud oxygen carrier on the pyrolysis and gasification behavior. Based on fluidized bed reactor, the effects of reaction temperature (750–900 ℃) and oxygen carrier to fuel ratio (0.1–0.7) on the syngas distribution, carbon conversion and its conversion rate, syngas content and the ratio of H2/CO in syngas were investigated. Results indicated that the presence of oxygen carrier has remarkably positive effect on the pelletized cyanobacteria pyrolysis and gasification processes. It improves the pressure gradient caused by the pelletized cyanobacteria devolatilization. Consequently, the volatiles could be released gradually through the relatively developed channels. During chemical looping gasification process, the H2 content in the syngas has the highest concentration with its value higher than 45%, followed by CO2, CH4 and CO. The increase of the reaction temperature or oxygen carrier to fuel ratio leads to the increase of carbon conversion. When the reaction temperature increases from 750 ℃ to 950 ℃, the ratio of H2/CO in the syngas decreases from 7.26 to 4.83. Meanwhile, with the increasing oxygen carrier to fuel ratio, the ratio of H2/CO first increases and then decreases, and the peak is 5.6 with the value of the oxygen carrier to fuel ratio as 0.5.
Abstract(76) HTML(24) PDF 1042KB(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(39) HTML(11) PDF 2054KB(7)
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The deep eutectic solvent (DES) delignification process has received increasing attention due to the relatively complete structure of the extracted lignin. However, the co-achievement of high lignin removal rate and structural integrity remain challenging. In this work, the effects of ChCl/carboxylic acids, molar ratio of hydrogen bond acceptor to donor, pretreatment temperature and time on the poplar delignification were investigated. XRD, FTIR, GPC, and HSQC were used to analyze the solid residue and extracted lignin for the study of the structural evolution of the three components. The results showed that under low temperature of 90ºC, the delignification in the ChCl/FA pretreatment of poplar wood was as high as 91%, and the lignin recovery and purity were as high as 63% and 90%, respectively. The cellulose retention was over 98%, in addition, the cellulose crystal form remained cellulose I and the crystallinity of solid residue was up to 70%. The extracted lignin contains 84.8% β−O−4 bond (71% of the original β−O−4 bond) with Mn of 1400 g/mol, which is ideal raw materials of monophenlics.
Abstract(22) HTML(26) PDF 1214KB(1)
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Uranium is a kind of radionuclide and also an important strategic resource. In some areas of China, the content of U in coal is extremely enriched. After high temperature transformation, U in coal would be enriched in solid products, which may cause radioactivity risk. In order to control the release of U and transform U in coal products into resource, it is necessary to investigate the migration law of uranium during thermal utilization of coal. Based on the thermodynamic equilibrium principle, this paper calculated and analyzed the morphology distribution of uranium in the pyrolysis, gasification and combustion processes of Ganhe coal, Xiao Longtan coal and Shengli coal. Also the influence of calcium based additives on U migration was analyzed, to provide theoretical guidance for subsequent experimental studies. The results show that: uranium has different forms under different thermal techniques; UO3(g) is the only gas phase product produced under different working conditions, and higher temperature, lower pressure and stronger oxidation environment will increase the amount of UO3(g); volatilization of uranium has been significantly week, since the fixation of uranium in calcium uranate. Especially, the amount of calcium uranate in Ganhe coal during combustion is increased obviously after the use of calcium based additives and the effect of CaO is the most significant.
Abstract(11) HTML(5) PDF 1144KB(4)
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During the coal pyrolysis with the coal ash as heat carrier, the interactions of coal ash and volatile matters could occur in the secondary reactions, which would affect the final sulfur-containing product yields of volatile matter. The objective of this paper was to reveal the effects of coal ash on the sulfur transformation during the secondary reactions. The results showed that the presence of XLT ash during secondary reactions inhibited H2S and COS release at low temperatures due to the sulfur fixation of Fe2O3 existed in the ash. However, it enhanced H2S and COS release at high temperatures, which was mainly caused by the formation of sulfur-containing gases through the reactions between CaSO4 and reducing gas (i.e. H2, CO, and CH4). The influences of Fe2O3 and CaSO4 were also investigated to reveal the mechanism of the influence of coal ash, and it was found that H2S and COS yields were reduced with the addition of Fe2O3, but those two gases were slightly increased by the presence of CaSO4 at 800 ℃, indicating that Fe2O3 and CaSO4 played important roles in the interactions between the coal ash and sulfur-containing gases.
Abstract(25) HTML(9) PDF 33390KB(4)
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In order to reveal the pyrolysis and coking characteristics of different components in coal, the macerals in Huangling coal were enriched by centrifugation, and the pyrolysis characteristics of macerals were studied. The transformation characteristics of macerals during pyrolysis were observed in-situ by heating stage microscope. The purities of vitrinite and inertinite are more than 90% and 80%, respectively, while the purity of liptinite is nearly 70%. The initial pyrolysis temperature of liptinite is about 385 ℃, and those of the other macerals are all about 410 ℃. The maximum pyrolysis temperatures are between 470−480 ℃ for all macerals studied. The maximum weight loss rate and the total weight loss rate decrease in the order of liptinite, vitrinite, semi-vitrinite and inertinite. The softening temperature of the liptinite (including sapropelic groundmass) is 350−370 ℃, while that of vitrinite is about 410−420 ℃ as shown by the in-situ pyrolysis in a heating stage microscope. The pyrolysis process of vitrinite goes through the stages of edge shrinking, pore formation, surface softening, the formation of liquid phase, and solidification. Only slight morphological changes are observed in semi-vitrinite, while no changes are observed in inertinite. The active components in Huangling coal are vitrinite and liptinite, and the liptinite can promote the softening and melting characteristics of the adjacent vitrinite.
Abstract(26) HTML(9) PDF 845KB(4)
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In this paper, the influence of NiO support on the synthesis of methanol from CO2 hydrogenation on In2O3(110) defect surface was studied with density functional theory (DFT). Two methanol synthesis pathways, namely HCOO pathway and reverse water gas (RWGS) pathway, were analyzed. The reaction energy and activation energy barrier of each elementary reaction involved in the HCOO and RWGS pathways were calculated. The results show that the NiO support can enhance the adsorption performance of In2O3 catalyst for CO2 and promote the generation of methanol through the HCOO reaction path. In the HCOO path, the hydrogenation of HCOO to H2COO is the rate-determining step for the HCOO reaction path, and the activation energy barrier is 1.66 eV. The NiO-supported In2O3(110) defect surface has a promoting effect on the hydrogenation of CO2, which is conducive to the synthesis of methanol from CO2 along the HCOO pathway, thus improving the efficiency of methanol synthesis from CO2 hydrogenation.
Abstract(27) HTML(7) PDF 1024KB(3)
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Using cheap coal pitch as raw material and adding pore-forming agent, the carbon material with three-dimensional skeleton structure was obtained by mixing process, air oxidation stabilization process and carbonization process successively, and then the porous carbon material with high specific surface area was obtained by water vapor activation. Thermogravimetric and elemental analysis were used to study the thermal reaction characteristics and structural changes of the samples after oxidation stabilization and carbonization. The surface morphology, pore structure and electrochemical properties of the activated samples were characterized by scanning electron microscope, BET method and electrochemical workstation. After water vapor activation, BET of porous carbon can reach 1638 m2/g. The water-based double layer capacitors prepared with this porous carbon as the electrode material of supercapacitors have good cyclic performance, and the specific capacitance can reach 252 F/g at 1 A/g current density. After 10000 cycles, the specific capacity can still maintain 97.3%. Therefore, the porous carbon materials prepared by this method have low cost and good chemical stability, and can be used as an ideal electrode material for supercapacitors.
Abstract(71) HTML(18) PDF 3368KB(19)
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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(27) HTML(7) PDF 1100KB(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(16) HTML(5) PDF 976KB(3)
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Conductive carbon film has a wide range of application prospects, especially in the fields of electric heating devices, energy storage devices, and solar cells. Coal tar is an ideal precursor for preparing carbon film. In order to improve the performance of coal tar-based carbon film, it is necessary to study the influence of tar composition on the structure and performance of carbon film. In this paper, a carbon film is prepared using aromatic compounds, heteroatom compounds and tar as carbon sources. It is found that the carrier concentration of aromatic hydrocarbon-based carbon films is higher than 1022/cm3, but the mobility of the carrier is lower than 1 cm2/Vs. The resistivity and sheet resistance of the aromatic hydrocarbon-based carbon film are lower than that of the coal tar-based carbon film. Naphthalene-based carbon film has the best electrical and thermal properties. The maximum heating temperature of naphthalene-based carbon film at 30 V exceeds 300 °C. The thickness of the carbon film has a decisive influence on the sheet resistance of the carbon film. The performance of the heteroatom compound-based carbon film is significantly lower than that of aromatic compound-based film.
Abstract(14) HTML(3) PDF 465KB(3)
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The effects of pretreatment methods (DR, R, ROR) on the microstructure of Co/SiO2 catalysts and the activity for Fischer-Tropsch synthesis (FTS) were investigated. The pretreated catalysts were characterized by TEM, HRTEM, XRD, XPS, H2-TPD, TG and TPR. The results showed that after the pretreatments, specific morphological of the Co species changed, forming new Co active surface species. The Co particles redispersed and the Co species was facile to be re-reduced. The Co/SiO2 catalysts pretreated by different method showed different catalytic performance. The catalyst treated by the reduction-passivation had higher activity and ${\rm{C}}_{5}^ {+}$ selectivity for FTS.
Abstract(44) HTML(15) PDF 1164KB(9)
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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(39) HTML(8) PDF 1383KB(5)
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Previous works manifested that the catalyst of Fe-Ag/Al2O3/CM can efficiently convert NO into N2 using C3H6, with a good resistance to H2O and SO2. More efforts were carried out to study on the influence of the preparation processes on the catalytic activity. Three typical loading methods were compared, namely, physical grinding (PG), direct impregnation (DI) and sol-gel-impregnation (SGI) methods. Experimental results showed that, all the three groups of catalysts had a good tolerance with water vapor and SO2. Regarding the order of the maximum NO removal efficiency, it is: SGI (100%) > PG (62%) > DI (58%). Based on the results of multiple characterizations, it’s analyzed that the porous surfaces and the Fe-Ag interactions were important factors. When the SGI approach was adopted, the primary support of cordierite and the secondary support of Al2O3 worked together to achieve a pretty large specific area and a satisfactory interaction between Fe and Ag irons, resulting in the bimetal oxide of AgFeO2. Consequently, the SGI sample obtained the largest area of reduction peak over H2-TPR profiles. In terms of the PG method, the prepared sample was in powder form with the largest specific area. However, without the cordierite serving as the monolithic support, there was no porous surfaces to facilitate the Fe-Ag interactions. They existed in the form of separate oxides (Ag2O and Fe3O4) and a little hint of elemental Ag, and their H2-TPR reduction ability was weaker. As far as the DI method was concerned, due to the absence of the secondary support of Al2O3, the dispersion of Fe and Ag was poor and their individual oxides agglomerated on the catalysis surface, without AgFeO2 detected. Even worse, its specific area was just 1/4 of the SGI sample. Therefore, the DI approach offered the poorest activity.
Abstract(46) HTML(20) PDF 3317KB(4)
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Alkylbenzenes are important bulky chemicals. The production of alkylbenzenes through benzene and syngas alkylation technology of coal chemical industry can reduce the domestic dependence on petroleum. In this study, mechanical mixture of ZnAlOx and ZSM-5 were used to catalyze the alkylation reaction of benzene and syngas. The results showed that the best performance catalyst was obtained with the 1∶1 mass ratio of the two components and the 2∶1 molar ratio of zinc to aluminum. It was suggested that the main reaction intermediates of methanol and dimethyl are produced on the O vacancy of ZnO and L acidic center of Al2O3 in ZnAlOx. And the alkylated benzenes are formed by the reaction of benzene with the intermediates over ZSM-5. Due to the high temperature property of ZnAlOx for methanol synthesis which can accommodate to the reaction of ZSM-5 for benzene alkylation, the high catalytic activity and selectivity was obtained.
Abstract(26) HTML(18) PDF 1123KB(2)
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By changing the simulation incineration conditions of municipal solid waste incineration experiment (nickel catalyst, water), analysing the reaction temperature, incineration exhaust gas flow, concentration of exhaust gas composition, the dioxin concentrations, the toxicity of dioxin equivalent of absorbing liquid, and the change of the absorption liquid organic matter concentration, to explore the effect of different combustion conditions on dioxins from simulated municipal solid waste incineration. The results showed that the addition of nickel catalyst and water could promote the conversion of macromolecule organic matter to small molecule organic matter during the incineration process, and effectively inhibited the precursor synthesis of dioxins, the suppression ratio of dioxins were decreased by 80.7% and the total equivalent toxicity of dioxins were decreased by 98%.
Abstract(63) HTML(15) PDF 1666KB(8)
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The size distribution of aromatic nuclei in coal influences the composition of tar and char during pyrolysis. Pyrolytic experiments of Naomaohu (NMH) coal from Xinjiang in China were carried out in a fixed-bed reactor at different temperatures to study the size distribution of aromatic nuclei during coal pyrolysis. With the increase of pyrolysis temperature, the aromaticity of char, the graphitization degree, and the order degree of aromatic layers increase. The tar is mainly composed of aromatic clusters with 1-2 rings and contains a small amount of aromatic clusters with 3 or more rings. The tar yield increases first and then decreases with increasing temperature (maximum at 550 ℃). However, the changes in the Synchronous fluorescence spectra of the tars with increasing temperature are not significant, indicating that the size distribution of aromatic nuclei in tar changes little with no significant condensation polymerization, and also indicating that the number of bridged bonds and the cracking activity distribution of these bridge chains in different size aromatic rings are relatively uniform. With the increase of pyrolysis temperature, the content of 1 × 1 aromatic layers in the pyrolysis products (char and tar) decreases gradually. When the pyrolysis temperature is at between 500 ℃ and 600 ℃, the 1 × 1 aromatic layers are mainly transformed into 2 × 2 and 3 × 3 aromatic layers. When the temperature is higher than 650 ℃, the formation of aromatic layers with the size of 4 × 4 and above takes the main part of condensation polymerization.
Abstract(57) HTML(10) PDF 1561KB(12)
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Abstract(40) HTML(5) PDF 1175KB(4)
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In this work, the separation of phenol from oil mixtures was proposed by using mildronate (THP), Girard's Reagent T, and Girard's Reagent P. The results showed that the mentioned separation agents could form deep eutectic solvent (DES) with phenol and then separate phenol. The highest separation efficiency of phenol was 96.5% by THP, and the residual phenol content in oil was as low as 1.3 g/L; it was enough to finish separation in 10 min; the initial phenol content had no effect on the minimum residual phenol content (about 8.8 g/L) in oil after separation. An n-hexane washing method was used to remove the neutral oil entrained in DES. The results showed that the neutral oil to phenol mass ratio in DES was reduced to 0.04, which indicated that the purity of phenol product was greatly improved. THP was renewable and reused for 5 times, and its properties remained unchanged. Finally, FT-IR spectra showed that there was hydrogen bonds formed between THP and phenol.
Abstract(48) HTML(21) 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(28) HTML(11) PDF 1457KB(4)
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In this study, the structure and combustion performance of pyrolysis chars from Daliuta raw coal, vitrinite-rich sample, inertinite-rich sample and demineralized coal sample were studied by Raman spectroscopy. The results showed that under the same pyrolysis conditions, compared with the pyrolysis char from Daliuta raw coal sample, the pyrolysis char from the demineralized coal sample has more large aromatic ring systems (≥ 6 rings), higher ignition temperature and much low combustion performance. The combustion performance of pyrolysis char from inertinite-rich sample is lower than that from vitrinite-rich sample, and the burnout capacity of pyrolysis char from inertinite-rich sample is far lower than that from vitrinite-rich sample. The ignition temperature (ti), the combustion reactivity index (tindex) and the wavenumber of D band (WD) in the Raman spectrum of Daliuta coal char has a good correlation, the correlation coefficients R2 obtained by the quadratic curve fitting are 0.9159 and 0.7133, respectively. There is no obvious correlation between burn-out temperature and WD of Daliuta coal char, indicating that the carbon structure of Daliuta coal char has a significant impact on the ignition temperature and combustion reactivity index of the char, but is no regular effect on the burn-out ability of the char.
Abstract(23) HTML(8) PDF 1399KB(4)
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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(38) HTML(15) 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 E1−E4 were analyzed by GC-MS. It is found that the main compounds in E1 are 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. The results show that the ultrasonic extraction process only extracts free small compounds from macromolecular skeleton of the NL and some other molecules, which connect the macromolecular skeleton by weak covalent bonds, and the process does not destroy the macromolecular skeleton structure. In addition, peak fitting results from FT-IR show that types of infrared absorption peaks in ER does not change after ultrasonic extraction, while intensity of the peaks varies. TG-DTG profiles of NL and ER indicate that after ultrasonic extraction weight loss of NL increases from 47.09% to 51.04%, and peak of the maximum weight loss rate is advanced from 450 to 430 ℃. Pyrolysis kinetic analysis of NL and ER based on Coast-Redfern model show that after ultrasonic extraction activation energy of ER in rapid pyrolysis stage is lower than that of NL, and the pyrolysis process is easier to proceed.
Abstract(30) HTML(5) PDF 1318KB(2)
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N-hexane was used as a model compound to study the catalytic cracking behavior of light hydrocarbon in HZSM-5 zeolites, and the law of product selectivity of real acid-catalyzed reaction was investigated by analyzing the product distributions. The results showed that no pyrolysis reaction was found at 300 ℃. Only the acid catalytic reaction took place by the mechanism of carbocation, whose activity was positively correlated to the amount of Brønsted (B) acid sites. The selectivity of ethane, ethylene and propane was negatively correlated, while that of propylene was positively correlated with the Si/Al ratios and catalyst to oil ratios, suggesting that low acid density might be more favorable for monomolecular cracking reactions. It was worth nothing that the total selectivity of C4 products was much higher than that of C2 products. Combined with the quantum chemistry calculation results, it could be confirmed that the super-stability of ${{\rm{C}}_{{2}}}{\rm{H}}_{{5}}^ {{+}}$ carbenium ion from the monomolecular cracking of n-hexane made it difficult to produce ethylene and ethane through hydrogen transfer reaction. It’s easier to form a C8 carbenium ion (${{\rm{C}}_{{8}}}{\rm{H}}_{{{19}}}^ {{+}}$) with another n-hexane molecule, and then to generate more C4 products. These results revealed the nature of the low selectivity of ethylene in light hydrocarbon catalytic cracking products. It could be concluded that the product selectivity of catalytic cracking of light hydrocarbons could be modulated by controlling reaction paths depending on the catalyst acid properties and the catalyst to oil ratios. This work will provide important theoretical support for the catalyst design and process development of naphtha catalytic cracking.
Abstract(34) HTML(15) PDF 1083KB(7)
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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(73) HTML(30) PDF 1829KB(14)
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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(78) HTML(14) PDF 1240KB(20)
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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(48) HTML(21) PDF 1366KB(5)
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Zn-doped and Zn-Al co-doped La2O3 catalysts were prepared by citric acid sol-gel method and characterized by a series of in situ technologies, to investigate the structure-activity relationship of La2O3-based catalysts in the oxidative coupling of methane (OCM). The in situ XRD results reveal a thermal expansion of the La2O3 crystal along the c-axis at high temperature. The H2-TPR results show two types of oxygen species on the La2O3-based catalysts, viz., the strong-binding oxygen species and weak-binding oxygen species; in addition, the XPS results indicate that the strong-binding oxygen species is probably attributed to anion radical O. The doping with Zn can significantly increase the number of oxygen vacancies in the Zn-doped La2O3 catalysts, which can promote the activation of oxygen and generate more strong-binding oxygen species; as a result, the Zn-doped La2O3 catalyst shows better performance in OCM in comparison with the unmodified La2O3 catalyst. Moreover, the co-doping with Al can promote the dispersion of Zn in La2O3 and further raise the number of strong-binding oxygen species in the Zn-Al co-doped La2O3 catalysts, which is beneficial to enhance the selectivity to C2+ hydrocarbons in the OCM reaction
Abstract(95) HTML(29) PDF 1861KB(8)
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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 types (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(23) HTML(3) PDF 1342KB(0)
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The effects of K, Ru or La promoters on the structure, surface area, crystal phase, and catalytic behavior during FT synthesis of carburized and uncarburized fused Fe catalysts were studied by XRD, XPS, TPD, N2-physisorption and catalytic reaction evaluation techniques. Addition of K improved selectivity of C5+ products for both the carburized and uncarburized catalysts. Addition of Ru suppressed catalytic activity of the carburized catalyst, but had little influence on the uncarburized one. Addition of La led to the encapsulation of the iron carbide, which consequently severely inhibited the carburization and decreased the activity. While Ru and La promote the formation of light components due to their ability to promote hydrogen adsorption. The performance of the reaction in the experiment indicated that the U-K catalyst had the best product distribution, in which the methane selectivity was 4.04%, and the C5+ selectivity was 75.84%.
Abstract(33) HTML(11) PDF 1389KB(3)
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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(37) HTML(28) PDF 1087KB(6)
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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 way and decomposition atmosphere on the microstructures of MoS2 slabs, chemical state of surface elements, as well as hydrodesulfurization and hydrodenitrogenation activities was investigated. Results indicated that simultaneous impregnation of Mo and Ni precursors 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 with more suitable slab length (3–5 nm) and stacking number (2–4), which attributed to larger numbers of rim and corner active sites exposed at the edges. These active sites were essential in hydrogenation and hydrogenolysis reactions. In comparison with N2 atmosphere, thermal decomposition in H2 atmosphere was more conducive to the substitution of Mo atoms by Ni atoms at MoS2 edges, which provided more active Ni-Mo-S structures for the adsorption, activation and hydrogenolysis of quinoline and dibenzothiophene molecules. The catalyst prepared by thermal decomposition of NiMoS4 in H2 atmosphere showed superior activities in the quinoline hydrodenitrogenation with 23.8% conversion and in the dibenzothiophene hydrodesulfurization with 93.3% conversion, under the conditions of 340 °C, 3 MPa, a weight hourly space velocity of 23.4 h–1, H2/oil volume ratio of 600 and 0.1 grams of NMS-H2 catalysts.
Abstract(80) HTML(19) PDF 1624KB(12)
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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 calculated pure gas uptake was agree well with the experimental data, which proved that the current simulation model and COMPASS force field are reliable. On this basis, molecular dynamics (MD) simulations were carried out for diffusion and separation of CO2, CH4 and N2 on 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 is dominant resulted from the tight fit of the gas molecules and the zeolite pore size. The diffusion of CO2, CH4 and N2 in MER zeolites with three-dimensional cage structures is anisotropic. The gas molecules diffuse preferentially along with the direction of x axis in K-MER zeolites. Extra-framework cations in zeolite plays important influence on the gas diffusion. In K-MER zeolites, the self-diffusion coefficients of CO2 and N2 are negative correlated with loading, whereas for the self-diffusion coefficient of CH4, it firstly increases and then decreases with the increase of loading. All of the self-diffusion coefficients of CO2, CH4 and N2 increase with the elevation 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(54) HTML(6) PDF 20401KB(9)
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Zn-Co(OH)2 precursor was hydrothermally deposited on carbon paper at 120 ℃, using cobalt nitrate and zinc nitrate as raw materials. Then Zn-Co(OH)2 was etched and partially sulfided into CoSOH/Co(OH)2 with 5 mol/L NaOH and 1 mol/L Na2S aqueous solution at room temperature. The catalytic performance in oxygen evolution reaction (OER) was investigated. XRD, SEM, TEM, XPS were used to characterize the microstructure, physical and chemical properties of the catalyst. The results show that the used method can etch Zn atoms, create oxygen vacancies and dope sulfur. The oxygen vacancies and doped sulfur play a positive role in enhancing the OER performance. In addition, amorphous CoSOH also exhibited better OER activity. The synergy between CoSOH and Co(OH)2 finally induces the best catalytic properties (overpotential η=310 mV, Tafel slope b=90 mV/dec) and long-term electrochemical stability, that is CoSOH/Co(OH)2 possess superior electrocatalytic oxygen evolution performance.
Abstract(35) HTML(7) PDF 1028KB(4)
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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(104) HTML(9) 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(17) 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(33) HTML(19) 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(63) HTML(24) PDF 1399KB(16)
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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.
2021, 49(9): 1-8.
Abstract(25) HTML(12) PDF 5907KB(5)
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2021, 49(9): 1219-1230.   doi: 10.1016/S1872-5813(21)60091-9
Abstract(83) HTML(19) PDF 2105KB(17)
Abstract:
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 (13C NMR), coal rock analyzer, X-ray fluorescence spectrometry (XRF) and Gieseler fluidity. Combining with X-ray photoelectron spectroscopy (XPS), effect of different gas coal separation components on sulfur transformation behavior during pyrolysis of high-sulfur coal and distribution of sulfur forms in coke was investigated. The results show that with 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; hydrogen free radicals in volatiles promote decomposition of sulfur, stabilize sulfur free radicals in time and release as sulfur-containing gases, and thus sulfur content in coke is reduced. Low density components in gas coal have the largest maximum fluidity and widest plastic range, and stability of plastic layer is the best during co-pyrolysis with high sulfur coal. The basic minerals in gas coal are mainly enriched in high density components, which leads to increase of sulfide sulfur and sulfate sulfur in the coke. For utilization of gas coal in coal-blending pyrolysis, enrichment of vitrinite and selection of coals with easier removal of alkaline minerals are beneficial for reducing sulfur in coke.
2021, 49(9): 1231-1238.   doi: 10.1016/S1872-5813(21)60088-9
Abstract(98) HTML(22) PDF 937KB(21)
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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.
2021, 49(9): 1239-1249.   doi: 10.1016/S1872-5813(21)60073-7
Abstract(65) HTML(11) PDF 817KB(8)
Abstract:
Three agricultural residues (peanut straw, sorghum stalk and reed) were first pretreated by water washing, with which the pyrolysis experiments were carried out in a fixed bed reactor to investigate how the pyrolysis characteristics are changed by removing the alkali earth metals (AAEMs) and a part of fibrous components by water washing. The result shows that the water washing removes 52.7%–92.6% potassium and approximately half of neutral detergent solute (NDS) from three agricultural residues. The removal of AAEMs and NDS has a complex influence on the pyrolysis of agricultural residues, especially for peanut straw due to its higher contents of both AAEMs and NDS. However, the removal of AAEMs has an inhibitory effect on the reactions such as decarboxylation, decarbonylation, dehydrogenation and polycondensation, and the elution of NDS directly affects the yields and composition of gas and liquid products. For all three agricultural residues, overall, the water washing promotes the production of bio-oil and bio-char, but it lowers the gas yield. The bio-oils generated from the water-washed agricultural residues have higher proportions of oxygenates, especially sugars and furans, with lower proportions of hydrocarbons and nitrogenous compounds. Besides, after washing, the yields of CO2, CO and CH4 with peanut straw decrease significantly, while the proportion of long-chain fatty acids in bio oil increases.
2021, 49(9): 1250-1260.   doi: 10.19906/j.cnki.JFCT.2021053
Abstract(48) HTML(17) PDF 1537KB(5)
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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 not only was conducive to methane activation, but also enhanced 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.
2021, 49(9): 1261-1269.   doi: 10.1016/S1872-5813(21)60083-X
Abstract(56) HTML(20) PDF 820KB(11)
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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.
2021, 49(9): 1270-1280.   doi: 10.1016/S1872-5813(21)60101-9
Abstract(100) HTML(17) PDF 1910KB(5)
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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 were 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% glycerol aqueous solution is continuously added, 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 reach 33.1%.
2021, 49(9): 1281-1293.   doi: 10.19906/j.cnki.JFCT.2021068
Abstract(43) HTML(13) PDF 1229KB(13)
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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.
2021, 49(9): 1294-1315.   doi: 10.1016/S1872-5813(21)60080-4
Abstract(92) HTML(12) PDF 1005KB(25)
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Metal-supported zeolite catalysts have been 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 in the structural characteristics, catalytic performance and reaction mechanism of Cu- and Fe-based zeolite catalysts in NH3-SCR was summarized. In addition, the application of density functional theory (DFT) calculation in clarifying the reaction mechanism of NH3-SCR was introduced. Finally, the reaction kinetics and the apparent kinetic parameters of different metal-based zeolite catalysts in NH3-SCR were compared and discussed. We hope this review could provide new ideas for the study of NH3-SCR reaction mechanism over metal-supported zeolite catalysts.
2021, 49(9): 1316-1325.   doi: 10.1016/S1872-5813(21)60075-0
Abstract(69) HTML(10) PDF 1095KB(8)
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In this work, ZIF-8/Pt/SiO2 catalysts were prepared by combining atomic layer deposition (ALD) and vapor phase conversion methods. First, Pt metal nanoparticles were deposited on SiO2 nanowires by ALD. Then, ZnO was further deposited, also by ALD. Subsequently, the ZnO film was converted into ZIF-8 film by vapor phase crystallization to form a sandwich structure (ZIF-8/Pt/SiO2). The microstructures of the catalysts were characterized by XRD, TEM, BET, IC-MS, XPS, and CO-DRIFT. It was shown that the Pt particles were highly dispersed on the SiO2 nanowires before and after coating with ZIF-8, and the ZIF-8 film was coated continuously on the entire catalyst with high conformity. The performance of the catalyst was studied by using the semi-hydrogenation of 1-heptyne as a probe reaction. The ZIF-8 film induces an electron density increase in the Pt component, leading to an increase of the olefin selectivity from 14% to 70% in the 1-heptyne hydrogenation reaction. A reduced thickness of the ZIF-8 film increases the catalytic activity but does not affect the selectivity of 1-heptylene.
2016, 44(4): 385-393.
[Abstract](82) [FullText HTML](61) [PDF 1138KB](6)

2016, 44(7): 777-783.
[Abstract](72) [FullText HTML](28) [PDF 2169KB](2)

2016, 44(3): 263-272.
[Abstract](42) [FullText HTML](37) [PDF 1275KB](2)

2016, 44(7): 801-814.
[Abstract](109) [FullText HTML](58) [PDF 8665KB](11)

2016, 44(11): 1388-1393.
[Abstract](63) [FullText HTML](44) [PDF 780KB](0)

2016, 44(3): 279-286.
[Abstract](63) [FullText HTML](38) [PDF 12189KB](1)

2016, 44(6): 732-737.
[Abstract](54) [FullText HTML](24) [PDF 2776KB](1)

2016, 44(9): 1034-1042.
[Abstract](74) [FullText HTML](35) [PDF 809KB](0)

2017, 45(1): 113-122.
[Abstract](48) [FullText HTML](28) [PDF 1085KB](1)

2018, 46(2): 179-188.
[Abstract](48) [FullText HTML](17) [PDF 7028KB](2)

2013, 41(08): 1003-1009.
[Abstract](2037) [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](1505) [PDF 0KB](8)
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.