High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,...High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,N2physisorption,27Al magic angle spinning nuclear magnetic resonance(MAS NMR),and temperature-programmed desorption of ammonia results indicated that the hightemperature treatment at 650℃ hardly affected the inherent crystal and texture of HZSM-5zeolites but facilitated the conversion of framework Al to extra-framework Al,reducing the acid site and enhancing the acid strength.Moreover,the high-temperature treatment improved the performance of HZSM-5 zeolites in n-heptane catalytic cracking,promoting the conversion and light olefins yield while inhibiting coke formation.Based on the kinetic and mechanism analysis,the improvement of HZSM-5 performance caused by high-temperature treatment has been attributed to the formation of extra-framework Al,which enhanced the acid strength,facilitated the bimolecular reaction,and promoted the entropy change to overcome a higher energy barrier in n-heptane catalytic cracking.展开更多
Hydroisomerization of n-heptane is an efficient method for producing gasoline with a high octane number.The focus of this study was to find a highly efficient catalyst that could both promote the conversion of n-hepta...Hydroisomerization of n-heptane is an efficient method for producing gasoline with a high octane number.The focus of this study was to find a highly efficient catalyst that could both promote the conversion of n-heptane and inhibit the cracking side reaction.MIL-101(Cr)is a chromium-based metal-organic framework(MOF)with good hydrothermal stability,and exhibits a three-dimensional pore structure that is similar to that of zeolites.Using phosphomolybdic acid(PMA;H3PMo12O40·xH2O)can increase the number of Brønsted acid sites on MIL-101(Cr),which contributes to improving the catalytic performance during isomerization.In this study,0.4%Pt/PMA-MIL-101(Cr)catalyst was successfully crystallized at 220℃using a hydrothermal synthetic method.The results showed that the synthesized samples were mesoporousmicroporous composite materials with the typical octahedral structure,and the MIL-101(Cr)framework was not damaged following modification with PMA.It was found that 0.4%Pt30%PMA-MIL-101(Cr)exhibited the best performance for isomerization of n-heptane,with a conversion rate and selectivity at 260°C of 47.6%and 96.6%,respectively.After five hours of reaction,the conversion rate and selectivity of the catalyst remained above 38%and 80%,respectively.展开更多
Single-crystalline hierarchical ZSM-5 zeolites with different particle sizes(namely 100,140,and 200 nm)were successfully prepared by adjusting the amount of tetrapropylammonium hydroxide(TPAOH),and investigated in n-h...Single-crystalline hierarchical ZSM-5 zeolites with different particle sizes(namely 100,140,and 200 nm)were successfully prepared by adjusting the amount of tetrapropylammonium hydroxide(TPAOH),and investigated in n-heptane catalytic cracking reaction.Diffusional measurements by zero-length column(ZLC)method showed that the apparent diffusivities of n-heptane decreased with the reduction of particle size,indicating the existence of surface barriers.Moreover,with the decrease of particle size,the additional diffusion path length increased,which meant the influence of surface barriers became more apparent.Despite the change of surface barriers,the intracrystalline diffusion still dominated the overall diffusion.Catalytic performance showed that the zeolite with smaller particle size had better stability.展开更多
Since paraffins catalytic cracking was of significant importance to light olefins and aromatics production,this work was intended to gain insights into the feature and model of coke formation and catalyst deactivation...Since paraffins catalytic cracking was of significant importance to light olefins and aromatics production,this work was intended to gain insights into the feature and model of coke formation and catalyst deactivation in n-heptane catalytic cracking over HZSM-5 zeolites. 18 tests of n-heptane catalytic cracking were designed and carried out over HZSM-5 zeolites in a wide range of operating conditions. A particular attention was paid to the measurement of the conversion, product distribution, coke content, and the porosity and acidity of the fresh and spent HZSM-5 zeolites. It was found that alkene and aromatic promoted coke formation, and it reduced the pore volume and acid site of HZSM-5 zeolites, tailoring its performance in n-heptane catalytic cracking. The specific relationship between HZSM-5 zeolites, n-heptane conversion, product distribution and coke formation was quantitively characterized by the exponential and linear function. Based on the reaction network, the coupled scheme of coke formation and catalyst deactivation were specified for n-heptane catalytic cracking. The dual-model was proposed for the process simulation of n-heptane catalytic cracking over HZSM-5 zeolites. It predicted not only the conversion and product distribution but also coke content with the acceptable errors.展开更多
The thermal decomposition of n-heptane is an important process in petroleum industry. The theoretical investigations show that the main products are C2H4, H2, CH4, and C3H6, which agree well with the experimental resu...The thermal decomposition of n-heptane is an important process in petroleum industry. The theoretical investigations show that the main products are C2H4, H2, CH4, and C3H6, which agree well with the experimental results. The products populations depend strongly on the temperature. The quantity of ethylene increases quickly as the temperature goes up. The conversion of n-heptane and the mole fraction of primary products from reactive molecular dynamic and chemical kinetic modeling are compared with each other. We also investigated the pre-exponential factor and activation energy for thermal decomposition of n-heptane by kinetic analysis from the reactive force field simulations, which were extracted to be 1.78×10^14 s^-1 and 47.32 kcal/mol respectively.展开更多
n-Heptane is the most important straight chain paramn in the fossil-fuel industry. In this work, pyrolysis behavior of n-heptane at high temperature is investigated by a se- ties of ReaxFF based reactive molecular dyn...n-Heptane is the most important straight chain paramn in the fossil-fuel industry. In this work, pyrolysis behavior of n-heptane at high temperature is investigated by a se- ties of ReaxFF based reactive molecular dynamics simulations. Temperature effects on the n-heptane pyrolysis and related products distributions have been detailedly analyzed. The simulation results indicate that the temperature effect is characterized in stages. High tern- perature can accelerate the decomposition of n-heptane, but the influence becomes small after it reaches a certain level. According to the different reaction behaviors, pyrolysis of n-heptane could be divided into three stages. The variation trends of the mass fraction evolu- tion of ethylene （C2H4）, C3, and C4 calculated from reactive molecular dynamics simulations are in good agreement with the previous experimental results. The apparent activation en- ergy extracted from the first-order kinetic analysis is 53.96 kcal/mol and a pre-exponential factor is 55.34×10^13 s-1, which is reasonably consistent with the experimental results.展开更多
A series of Pt catalysts supported on the Hβ-zeolite that is ion-exchanged with the rare earth metal ions of Ce（III） and La（III）,are prepared by impregnation,characterized by inductively coupled plasma （ICP）,X-...A series of Pt catalysts supported on the Hβ-zeolite that is ion-exchanged with the rare earth metal ions of Ce（III） and La（III）,are prepared by impregnation,characterized by inductively coupled plasma （ICP）,X-ray diffraction （XRD）,BET,temperature-programmed desorption of ammonia （NH3-TPD）,temperature-programmed reduction of hydrogen （H2-TPR） and H2-chemisorption techniques,and evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor.The reaction temperature,time on stream,space velocity,and the ratio of H2/n-heptane are changed to get the optimal conditions.The Ce（III） and La（III）-exchanged Hβ-zeolites exhibit higher selectivity for isomerized products than the neat Hβ-zeolite.Moreover,the Ce（III）-exchanged catalysts give higher conversions of n-heptane,whereas the La（III）-exchanged ones do not show any improvement in con-version.Under optimal conditions,the catalyst with 0.4% （by mass） Pt and 0.5% （by mass） Ce loading presents very high selectivity of isomerized products of 95.1% coupled with high n-heptane conversion of 68.7%.Effects of the ion-exchange of Ce（III） and La（III） on the catalytic performance are discussed in relation with the physico-chemical properties of catalysts.展开更多
Pt-（Sn,Re）/HZSM5-HMS catalysts were evaluated for n-heptane isomerization at 200–350 ℃.To characterize the catalyst,X-ray diffraction,X-ray fluorescene,Fourier transform infrared spectroscopy,ultraviolet-visible d...Pt-（Sn,Re）/HZSM5-HMS catalysts were evaluated for n-heptane isomerization at 200–350 ℃.To characterize the catalyst,X-ray diffraction,X-ray fluorescene,Fourier transform infrared spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,temperature-programmed reduction of H2,temperature-programmed desorption of NH3,infrared spectroscopy of adsorbed pyridine,H2 chemisorption,nitrogen adsorption-desorption,scanning electron microscopy and thermogravimetric analysis were performed.Kinetics of n-C7 isomerization were investigated under various hydrogen and n-C7 pressures,and the effects of reaction conditions on catalytic performance were studied.The results showed that bi-and trimetallic catalysts exhibit better performance than monometallic catalysts for this reaction.For example,a maximum i-C7 selectivity（ 〉74%） and multibranched isomer selectivity（40%） were observed for Pt-Sn/HZSM5-HMS at 200 ℃.展开更多
The SiO2 and g-Al2O3 supported MoOx catalyst and a MoOx-SiO2 catalyst have been studied in a conventional fixed-bed flow reactor for n-alkanes isomerization. It is shown that the MoOx-SiO2 catalyst with SiO2 framewor...The SiO2 and g-Al2O3 supported MoOx catalyst and a MoOx-SiO2 catalyst have been studied in a conventional fixed-bed flow reactor for n-alkanes isomerization. It is shown that the MoOx-SiO2 catalyst with SiO2 framework, in which the bulk MoOx phase is large enough to form typical mesoporous structure, is promising in terms of its advantages of both improved mechanical strength and high catalytic properties over the supported MoOx and bulk MoOx catalyst.展开更多
The mesoporous materials supported zirconium （Zr-MCM-48） and magnesium （Mg-MCM-48） with three-dimen- sional pore structures and different Zr or Mg contents were prepared via the hydrothermal method, respectively. ...The mesoporous materials supported zirconium （Zr-MCM-48） and magnesium （Mg-MCM-48） with three-dimen- sional pore structures and different Zr or Mg contents were prepared via the hydrothermal method, respectively. The prepared samples were characterized by means of X-ray diffraction （XRD）, scanning electron microscope （SEM）, transmission electron microscope （TEM）, Fourier transform infrared spectroscopy （FT-IR）, NH3 temperature programmed desorption （NH3-TPD） and N2 adsorption-desorption. The XRD, TEM and N2 adsorption-desorption results suggested that M-MCM-48 （where M = Zr, Mg） samples still maintained typical cubic mesoporous framework of MCM-48, with slight decrease of specific surface areas and mesopore orders. The isomerization of n-heptane was carried out as a probe reaction at various factors including the zirconium or magnesium content, reaction time, reaction temperature and weight hourly space veloc- ity （WHSV）. Preliminary results demonstrated that the Mg-MCM-48 catalyst exhibited a higher catalytic activity with a maximum heptane conversion of 91.5% and a corresponding isomerization selectivity of 72.3% as compared to that of Zr- MCM-48. However, for catalytic stability of Mg-MCM-48 for n-heptane isomerization was poorer than Zr-MCM-48, because the Mg-MCM-48 catalyst could maintain a relatively high catalytic activity for only 130 rain, while the Zr-MCM-48 catalyst could maintain a relatively high catalytic activity for more than 190 min without any obvious decrease in performance.展开更多
The 0.4%Pt/xSTA-MIL-101(Cr)metal-acid bifunctional catalysts were prepared by impregnation using STA-MIL-101(Cr)as the support.The synthesized samples were verified to exhibit a typical octahedral structure of MIL-101...The 0.4%Pt/xSTA-MIL-101(Cr)metal-acid bifunctional catalysts were prepared by impregnation using STA-MIL-101(Cr)as the support.The synthesized samples were verified to exhibit a typical octahedral structure of MIL-101(Cr)and the pore structure was arranged orderly.The specific surface area of the samples was extremely high and the samples were made of micro-mesoporous composite materials.Silicotungstic acid could retain its Keggin structure in the 0.4%Pt/xSTA-MIL-101(Cr)samples and the catalyst possessed moderately strong Brønsted acid sites.Besides,the dispersion of Pt particles in MIL-101(Cr)was relatively high.n-Heptane isomerization was first used as a probe to test the novel 0.4%Pt/xSTA-MIL-10(Cr)catalyst.Compared with the conventional silicate catalysts,the catalytic performance of 0.4%Pt/30%STA-MIL-101(Cr)was significantly improved with a n-heptane conversion of 58.93%and an iso-heptane selectivity of 95.68%,respectively,under conditions covering a reaction time of 2 h and a reaction temperature of 260°C.The catalyst could still maintain a relatively high catalytic performance after a reaction time of 5 h.Compared with the non-noble metal catalyst,the catalytic efficiency of 0.4%Pt/30%STA-MIL-101(Cr)is relatively high.The mechanism model of n-heptane isomerization over 0.4%Pt/xSTA-MIL-101(Cr)catalyst was established.展开更多
The effect of iridium loading on the properties and catalytic isomerization of n-heptane over Ir-HZSM-5 is studied. Ir-HZSM-5 was prepared by impregnation method and subjected to isomerization process in the presence ...The effect of iridium loading on the properties and catalytic isomerization of n-heptane over Ir-HZSM-5 is studied. Ir-HZSM-5 was prepared by impregnation method and subjected to isomerization process in the presence of flowing hydrogen gas. XRD and BET studies show that the presence of iridium stabilizes the crystalline structure of HZSM-5, leading to more ordered framework structure and larger surface area. TGA and FTIR results substantiate that iridium species interacts with OH group on the surface of HZSM-5. Pyridine FT-IR study verifies the interaction between iridium and surface OH group slightly increased the Bro¨nsted and Lewis acid sites without changing the lattice structure of HZSM-5. The presence of iridium and the increase of strong Lewis acid sites on HZSM-5 were found to bring an increase about 4.1%, 33.2% and 11.8% in conversion, selectivity and yield of n-heptane isomerization, respectively.展开更多
Polyimide（PI） is a type of important membrane material. A soluble polymer was synthesized from 4,4′-（hexafluoroisopropylidene） diphthalic anhydride（6FDA） and 2,2-bis[4-（4-aminophenoxy） phenyl] hexafluoroprop...Polyimide（PI） is a type of important membrane material. A soluble polymer was synthesized from 4,4′-（hexafluoroisopropylidene） diphthalic anhydride（6FDA） and 2,2-bis[4-（4-aminophenoxy） phenyl] hexafluoropropane（BDAF） by the two-step polymerization method. The polymer was proved to be polyimide 6FDA-BDAF by the Fourier transform infrared（FT-IR）, the 1H-NMR and ^（19）F-NMR spectra. An asymmetric membrane was prepared with the synthesized polyimide 6FDA-BDAF, it was porous in the 50 μm height bulk and dense in a 3–5 μm height surface. The membrane was used to separate n-heptane/thiophene mixtures by pervaporation with sulfur（S） contents from 50 to 900 μg g^（–1）. The total flux was enlarged from 7.96 to 37.61 kg m^（–2） h^（–1） with temperature increasing from 50 to 90°C. The membrane＇s enrichments factor for thiophene were about 3.13 and dependent on the experimental conditions. The experimental results demonstrated that polyimide 6FDA-BDAF would be a potential membrane material for desulfurization and controlled release of the S-containing fertilizer.展开更多
Solubilities of CO<sub>2</sub> in binary mixtures of n-decane-n-hexadecane and n-heptane-toluenewere measured in a glass apparatus by a synthetic method.Henry’s constants at several temperaturesand solven...Solubilities of CO<sub>2</sub> in binary mixtures of n-decane-n-hexadecane and n-heptane-toluenewere measured in a glass apparatus by a synthetic method.Henry’s constants at several temperaturesand solvent compositions were reported.While the Henry’s constants of CO<sub>2</sub> in mixtures of decaneand hexadecane can be satisfactorily predicted by a simple linear interpolation,prediction of Henry’sconstants for CO<sub>2</sub> in mixtures of heptane and toluene requires excess Gibbs energy of the solvent mix-tures.The standard thermodynamic functions of solution（ΔH<sup>0</sup>,ΔG<sup>0</sup>,and ΔS<sup>0</sup>）were reported.展开更多
In this article,numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture.The present work tried to optimize column by analyzing...In this article,numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture.The present work tried to optimize column by analyzing significant parameters such as feed flow rate,temperature and cut.In order to obtain the hydrodynamic and temperature and mass distribution inside thermal diffusion column,computational fluid dynamic(CFD) method is applied to solve the Navier-Stocks equations.Numerical simulations are conducted to study the main parameters in both stationary and time-dependent conditions.By using the separation work unit as a function of cut,the optimal cut for maximum SWU occurs within a limited range of 0.47-0.5 for feed rate between 0.5 and 4 g min^-1.Our findings reveal that the optimum feed rate in the range of optimum cut is about 1 g min^-1.In transient study,results show that the best cut for reaching to steady-state condition is θ=0.5.展开更多
The present paper reports new results regarding the addition of pseudo-boehmite as a binder during the synthesis of shaped Pt/WO_(3)-ZrO_(2)-Al_(2)O_(3) (PtWZA) catalysts. Binder shaping can noticeably influence not o...The present paper reports new results regarding the addition of pseudo-boehmite as a binder during the synthesis of shaped Pt/WO_(3)-ZrO_(2)-Al_(2)O_(3) (PtWZA) catalysts. Binder shaping can noticeably influence not only the structure and acidity of catalyst and improve its catalytic performance with regard to n-heptane isomerization, but the mechanical strength of the catalyst. A suitable binder content can improve the isomerization activity or selectivity by changing the acidity of PtWZA. The influence of the binder content depends on the WO_(3) content of the catalyst. PtWZA catalysts that contain 5%-15% binder on a dry basis exhibit favorable isomerization performance that depends on WO_(3) content. Suitable catalysts include Pt20WZ5A and Pt30WZ15A, which provide conversions of approximately 80%-90% and a selectivity of 90%. These new findings enrich researcher knowledge of the effect of the binder on the catalyst shaping process and are useful in the production of industrial catalysts.展开更多
The plasma liquid phase oxidation of n-heptane was investigated. The selectivity of product formation is far superior to plasma oxidation in the gas phase.
Effects of exhaust gas recirculation （EGR） on homogeneous charge combustion of n-heptane was studied through simulation and experiment. Experiments were carried out in a single cylinder, four-stroke, air cooled engi...Effects of exhaust gas recirculation （EGR） on homogeneous charge combustion of n-heptane was studied through simulation and experiment. Experiments were carried out in a single cylinder, four-stroke, air cooled engine and a single cylinder, two-stroke, water cooled engine. In the four-stroke engine, experiments of the effects of EGR were examined using heated N2 addition as a surrogate for external EGR and modifying engine to increase internal EGR. The ignition timing was sensitive to EGR due to thermal and chemical effects. EGR or extra air is a key factor in eliminating knock during mid-load conditions. For higher load operation the only way to avoid knock is to control reaction timing through the use of spark ignition. Experimental and modeling results from the two-stroke engine show that auto-ignition can be avoided by increasing the engine speed. The two-stroke engine experiments indicate that high levels of internal EGR can enable spark ignition at lean conditions. At higher load conditions, increasing the engine speed is an effective method to control transition from homogeneous charge compression ignition （HCCI） operation to non-HCCI operation and successful spark ignition of a highly dilute mixture can avoid serious knock.展开更多
Phospbomolybdate （PMo） with varying Mo loadings ranging from 5-30 wt% on alumina were prepared by incipient wetness impregnation method. 0.5 wt% of Pt was further loaded in order to prepare the bifunctional （metal-...Phospbomolybdate （PMo） with varying Mo loadings ranging from 5-30 wt% on alumina were prepared by incipient wetness impregnation method. 0.5 wt% of Pt was further loaded in order to prepare the bifunctional （metal-acid） Pt-PMo/Al2O3 catalysts. Thus prepared catalysts showed very high catalytic activities for n-heptane hydroisomerization compared with Pt impregnated MoO3 catalysts supported either on Al2O3 or on AIPO4. The conversion of n-heptane increased with Mo loading up to 20 wt% and slightly decreased with further Mo loading. However, the selectivity towards isomers showed an increasing trend up to 30 wt% of Mo in the catalyst. A relationship between catalytic activity and acidic strength was established in the present study.展开更多
基金the financial support from the National Natural Science Foundation of China(21908010)Jilin Provincial Department of Science and Technology(20220101089JC)the Education Department of Jilin Province(JJKH20220694KJ)。
文摘High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,N2physisorption,27Al magic angle spinning nuclear magnetic resonance(MAS NMR),and temperature-programmed desorption of ammonia results indicated that the hightemperature treatment at 650℃ hardly affected the inherent crystal and texture of HZSM-5zeolites but facilitated the conversion of framework Al to extra-framework Al,reducing the acid site and enhancing the acid strength.Moreover,the high-temperature treatment improved the performance of HZSM-5 zeolites in n-heptane catalytic cracking,promoting the conversion and light olefins yield while inhibiting coke formation.Based on the kinetic and mechanism analysis,the improvement of HZSM-5 performance caused by high-temperature treatment has been attributed to the formation of extra-framework Al,which enhanced the acid strength,facilitated the bimolecular reaction,and promoted the entropy change to overcome a higher energy barrier in n-heptane catalytic cracking.
基金National Natural Science Foundation of China(Grant No.22272129).
文摘Hydroisomerization of n-heptane is an efficient method for producing gasoline with a high octane number.The focus of this study was to find a highly efficient catalyst that could both promote the conversion of n-heptane and inhibit the cracking side reaction.MIL-101(Cr)is a chromium-based metal-organic framework(MOF)with good hydrothermal stability,and exhibits a three-dimensional pore structure that is similar to that of zeolites.Using phosphomolybdic acid(PMA;H3PMo12O40·xH2O)can increase the number of Brønsted acid sites on MIL-101(Cr),which contributes to improving the catalytic performance during isomerization.In this study,0.4%Pt/PMA-MIL-101(Cr)catalyst was successfully crystallized at 220℃using a hydrothermal synthetic method.The results showed that the synthesized samples were mesoporousmicroporous composite materials with the typical octahedral structure,and the MIL-101(Cr)framework was not damaged following modification with PMA.It was found that 0.4%Pt30%PMA-MIL-101(Cr)exhibited the best performance for isomerization of n-heptane,with a conversion rate and selectivity at 260°C of 47.6%and 96.6%,respectively.After five hours of reaction,the conversion rate and selectivity of the catalyst remained above 38%and 80%,respectively.
基金The support from the National Natural Science Foundation of China(22278353)is greatly appreciated。
文摘Single-crystalline hierarchical ZSM-5 zeolites with different particle sizes(namely 100,140,and 200 nm)were successfully prepared by adjusting the amount of tetrapropylammonium hydroxide(TPAOH),and investigated in n-heptane catalytic cracking reaction.Diffusional measurements by zero-length column(ZLC)method showed that the apparent diffusivities of n-heptane decreased with the reduction of particle size,indicating the existence of surface barriers.Moreover,with the decrease of particle size,the additional diffusion path length increased,which meant the influence of surface barriers became more apparent.Despite the change of surface barriers,the intracrystalline diffusion still dominated the overall diffusion.Catalytic performance showed that the zeolite with smaller particle size had better stability.
基金the financial support from the National Natural Science Foundation of China (21908010)the Education Department of Jilin Province (JJKH20220694KJ)。
文摘Since paraffins catalytic cracking was of significant importance to light olefins and aromatics production,this work was intended to gain insights into the feature and model of coke formation and catalyst deactivation in n-heptane catalytic cracking over HZSM-5 zeolites. 18 tests of n-heptane catalytic cracking were designed and carried out over HZSM-5 zeolites in a wide range of operating conditions. A particular attention was paid to the measurement of the conversion, product distribution, coke content, and the porosity and acidity of the fresh and spent HZSM-5 zeolites. It was found that alkene and aromatic promoted coke formation, and it reduced the pore volume and acid site of HZSM-5 zeolites, tailoring its performance in n-heptane catalytic cracking. The specific relationship between HZSM-5 zeolites, n-heptane conversion, product distribution and coke formation was quantitively characterized by the exponential and linear function. Based on the reaction network, the coupled scheme of coke formation and catalyst deactivation were specified for n-heptane catalytic cracking. The dual-model was proposed for the process simulation of n-heptane catalytic cracking over HZSM-5 zeolites. It predicted not only the conversion and product distribution but also coke content with the acceptable errors.
基金This work was supported by the National Natural Science Foundation of China （No.21103117）.
文摘The thermal decomposition of n-heptane is an important process in petroleum industry. The theoretical investigations show that the main products are C2H4, H2, CH4, and C3H6, which agree well with the experimental results. The products populations depend strongly on the temperature. The quantity of ethylene increases quickly as the temperature goes up. The conversion of n-heptane and the mole fraction of primary products from reactive molecular dynamic and chemical kinetic modeling are compared with each other. We also investigated the pre-exponential factor and activation energy for thermal decomposition of n-heptane by kinetic analysis from the reactive force field simulations, which were extracted to be 1.78×10^14 s^-1 and 47.32 kcal/mol respectively.
基金This work was supported by the National Natural Science Foundation of China （No.20273066）.
文摘n-Heptane is the most important straight chain paramn in the fossil-fuel industry. In this work, pyrolysis behavior of n-heptane at high temperature is investigated by a se- ties of ReaxFF based reactive molecular dynamics simulations. Temperature effects on the n-heptane pyrolysis and related products distributions have been detailedly analyzed. The simulation results indicate that the temperature effect is characterized in stages. High tern- perature can accelerate the decomposition of n-heptane, but the influence becomes small after it reaches a certain level. According to the different reaction behaviors, pyrolysis of n-heptane could be divided into three stages. The variation trends of the mass fraction evolu- tion of ethylene （C2H4）, C3, and C4 calculated from reactive molecular dynamics simulations are in good agreement with the previous experimental results. The apparent activation en- ergy extracted from the first-order kinetic analysis is 53.96 kcal/mol and a pre-exponential factor is 55.34×10^13 s-1, which is reasonably consistent with the experimental results.
基金Supported by the Jiangsu Provincial Key Natural Science Foundation for Universities（06KJA53012） the National Natural Science Foundation of China（20476046 20976084）
文摘A series of Pt catalysts supported on the Hβ-zeolite that is ion-exchanged with the rare earth metal ions of Ce（III） and La（III）,are prepared by impregnation,characterized by inductively coupled plasma （ICP）,X-ray diffraction （XRD）,BET,temperature-programmed desorption of ammonia （NH3-TPD）,temperature-programmed reduction of hydrogen （H2-TPR） and H2-chemisorption techniques,and evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor.The reaction temperature,time on stream,space velocity,and the ratio of H2/n-heptane are changed to get the optimal conditions.The Ce（III） and La（III）-exchanged Hβ-zeolites exhibit higher selectivity for isomerized products than the neat Hβ-zeolite.Moreover,the Ce（III）-exchanged catalysts give higher conversions of n-heptane,whereas the La（III）-exchanged ones do not show any improvement in con-version.Under optimal conditions,the catalyst with 0.4% （by mass） Pt and 0.5% （by mass） Ce loading presents very high selectivity of isomerized products of 95.1% coupled with high n-heptane conversion of 68.7%.Effects of the ion-exchange of Ce（III） and La（III） on the catalytic performance are discussed in relation with the physico-chemical properties of catalysts.
文摘Pt-（Sn,Re）/HZSM5-HMS catalysts were evaluated for n-heptane isomerization at 200–350 ℃.To characterize the catalyst,X-ray diffraction,X-ray fluorescene,Fourier transform infrared spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,temperature-programmed reduction of H2,temperature-programmed desorption of NH3,infrared spectroscopy of adsorbed pyridine,H2 chemisorption,nitrogen adsorption-desorption,scanning electron microscopy and thermogravimetric analysis were performed.Kinetics of n-C7 isomerization were investigated under various hydrogen and n-C7 pressures,and the effects of reaction conditions on catalytic performance were studied.The results showed that bi-and trimetallic catalysts exhibit better performance than monometallic catalysts for this reaction.For example,a maximum i-C7 selectivity（ 〉74%） and multibranched isomer selectivity（40%） were observed for Pt-Sn/HZSM5-HMS at 200 ℃.
文摘The SiO2 and g-Al2O3 supported MoOx catalyst and a MoOx-SiO2 catalyst have been studied in a conventional fixed-bed flow reactor for n-alkanes isomerization. It is shown that the MoOx-SiO2 catalyst with SiO2 framework, in which the bulk MoOx phase is large enough to form typical mesoporous structure, is promising in terms of its advantages of both improved mechanical strength and high catalytic properties over the supported MoOx and bulk MoOx catalyst.
基金supported by the postdoctoral programme for chemical engineering and technology of Northeast Petroleum Universitythe Youth Fund of Northeast Petroleum University(grant number NEPUQN2015-1-08)+2 种基金the Cultivation Fund of Northeast Petroleum University [grant number 2017PYYL-03]the Daqing Science and Technology Plan Projects [grant number szdfy-2015-04]the College Students’ Innovative Entrepreneurial Training Plan Projects of Heilongjiang Province [grant number 201710220030]
文摘The mesoporous materials supported zirconium （Zr-MCM-48） and magnesium （Mg-MCM-48） with three-dimen- sional pore structures and different Zr or Mg contents were prepared via the hydrothermal method, respectively. The prepared samples were characterized by means of X-ray diffraction （XRD）, scanning electron microscope （SEM）, transmission electron microscope （TEM）, Fourier transform infrared spectroscopy （FT-IR）, NH3 temperature programmed desorption （NH3-TPD） and N2 adsorption-desorption. The XRD, TEM and N2 adsorption-desorption results suggested that M-MCM-48 （where M = Zr, Mg） samples still maintained typical cubic mesoporous framework of MCM-48, with slight decrease of specific surface areas and mesopore orders. The isomerization of n-heptane was carried out as a probe reaction at various factors including the zirconium or magnesium content, reaction time, reaction temperature and weight hourly space veloc- ity （WHSV）. Preliminary results demonstrated that the Mg-MCM-48 catalyst exhibited a higher catalytic activity with a maximum heptane conversion of 91.5% and a corresponding isomerization selectivity of 72.3% as compared to that of Zr- MCM-48. However, for catalytic stability of Mg-MCM-48 for n-heptane isomerization was poorer than Zr-MCM-48, because the Mg-MCM-48 catalyst could maintain a relatively high catalytic activity for only 130 rain, while the Zr-MCM-48 catalyst could maintain a relatively high catalytic activity for more than 190 min without any obvious decrease in performance.
文摘The 0.4%Pt/xSTA-MIL-101(Cr)metal-acid bifunctional catalysts were prepared by impregnation using STA-MIL-101(Cr)as the support.The synthesized samples were verified to exhibit a typical octahedral structure of MIL-101(Cr)and the pore structure was arranged orderly.The specific surface area of the samples was extremely high and the samples were made of micro-mesoporous composite materials.Silicotungstic acid could retain its Keggin structure in the 0.4%Pt/xSTA-MIL-101(Cr)samples and the catalyst possessed moderately strong Brønsted acid sites.Besides,the dispersion of Pt particles in MIL-101(Cr)was relatively high.n-Heptane isomerization was first used as a probe to test the novel 0.4%Pt/xSTA-MIL-10(Cr)catalyst.Compared with the conventional silicate catalysts,the catalytic performance of 0.4%Pt/30%STA-MIL-101(Cr)was significantly improved with a n-heptane conversion of 58.93%and an iso-heptane selectivity of 95.68%,respectively,under conditions covering a reaction time of 2 h and a reaction temperature of 260°C.The catalyst could still maintain a relatively high catalytic performance after a reaction time of 5 h.Compared with the non-noble metal catalyst,the catalytic efficiency of 0.4%Pt/30%STA-MIL-101(Cr)is relatively high.The mechanism model of n-heptane isomerization over 0.4%Pt/xSTA-MIL-101(Cr)catalyst was established.
基金supported by the Ministry of Science,Technology and Innovation,Malaysia through E-Science Fund Research Project(No.03-01-06-SF0564 and 03-01-06-SF0289)the Hitachi Scholarship Foundation for the Gas Chromatograph Instrument Grant
文摘The effect of iridium loading on the properties and catalytic isomerization of n-heptane over Ir-HZSM-5 is studied. Ir-HZSM-5 was prepared by impregnation method and subjected to isomerization process in the presence of flowing hydrogen gas. XRD and BET studies show that the presence of iridium stabilizes the crystalline structure of HZSM-5, leading to more ordered framework structure and larger surface area. TGA and FTIR results substantiate that iridium species interacts with OH group on the surface of HZSM-5. Pyridine FT-IR study verifies the interaction between iridium and surface OH group slightly increased the Bro¨nsted and Lewis acid sites without changing the lattice structure of HZSM-5. The presence of iridium and the increase of strong Lewis acid sites on HZSM-5 were found to bring an increase about 4.1%, 33.2% and 11.8% in conversion, selectivity and yield of n-heptane isomerization, respectively.
基金support from the Key Technology R&D Program of China(2011BAD11B05)the National Nonprofit Institute Research Grant of Chinese Academy of Agricultural Sciences(2011-28,2013-17)+3 种基金supported by the National Basic Research Program of China(973 Program,2003CB615701)the National Natural Science Foundation of China(20576059,20676067,31572204)the China Petroleum&Chemical Corporation(SINOPEC Foundation,X505002)the China National Petroleum Corporation(CNPC)InnovationFoundation(05051143)
文摘Polyimide（PI） is a type of important membrane material. A soluble polymer was synthesized from 4,4′-（hexafluoroisopropylidene） diphthalic anhydride（6FDA） and 2,2-bis[4-（4-aminophenoxy） phenyl] hexafluoropropane（BDAF） by the two-step polymerization method. The polymer was proved to be polyimide 6FDA-BDAF by the Fourier transform infrared（FT-IR）, the 1H-NMR and ^（19）F-NMR spectra. An asymmetric membrane was prepared with the synthesized polyimide 6FDA-BDAF, it was porous in the 50 μm height bulk and dense in a 3–5 μm height surface. The membrane was used to separate n-heptane/thiophene mixtures by pervaporation with sulfur（S） contents from 50 to 900 μg g^（–1）. The total flux was enlarged from 7.96 to 37.61 kg m^（–2） h^（–1） with temperature increasing from 50 to 90°C. The membrane＇s enrichments factor for thiophene were about 3.13 and dependent on the experimental conditions. The experimental results demonstrated that polyimide 6FDA-BDAF would be a potential membrane material for desulfurization and controlled release of the S-containing fertilizer.
文摘Solubilities of CO<sub>2</sub> in binary mixtures of n-decane-n-hexadecane and n-heptane-toluenewere measured in a glass apparatus by a synthetic method.Henry’s constants at several temperaturesand solvent compositions were reported.While the Henry’s constants of CO<sub>2</sub> in mixtures of decaneand hexadecane can be satisfactorily predicted by a simple linear interpolation,prediction of Henry’sconstants for CO<sub>2</sub> in mixtures of heptane and toluene requires excess Gibbs energy of the solvent mix-tures.The standard thermodynamic functions of solution（ΔH<sup>0</sup>,ΔG<sup>0</sup>,and ΔS<sup>0</sup>）were reported.
文摘In this article,numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture.The present work tried to optimize column by analyzing significant parameters such as feed flow rate,temperature and cut.In order to obtain the hydrodynamic and temperature and mass distribution inside thermal diffusion column,computational fluid dynamic(CFD) method is applied to solve the Navier-Stocks equations.Numerical simulations are conducted to study the main parameters in both stationary and time-dependent conditions.By using the separation work unit as a function of cut,the optimal cut for maximum SWU occurs within a limited range of 0.47-0.5 for feed rate between 0.5 and 4 g min^-1.Our findings reveal that the optimum feed rate in the range of optimum cut is about 1 g min^-1.In transient study,results show that the best cut for reaching to steady-state condition is θ=0.5.
基金financial support from the National Natural Science Foundation of P. R. China (21103049)
文摘The present paper reports new results regarding the addition of pseudo-boehmite as a binder during the synthesis of shaped Pt/WO_(3)-ZrO_(2)-Al_(2)O_(3) (PtWZA) catalysts. Binder shaping can noticeably influence not only the structure and acidity of catalyst and improve its catalytic performance with regard to n-heptane isomerization, but the mechanical strength of the catalyst. A suitable binder content can improve the isomerization activity or selectivity by changing the acidity of PtWZA. The influence of the binder content depends on the WO_(3) content of the catalyst. PtWZA catalysts that contain 5%-15% binder on a dry basis exhibit favorable isomerization performance that depends on WO_(3) content. Suitable catalysts include Pt20WZ5A and Pt30WZ15A, which provide conversions of approximately 80%-90% and a selectivity of 90%. These new findings enrich researcher knowledge of the effect of the binder on the catalyst shaping process and are useful in the production of industrial catalysts.
基金The project was supported by National Natural Science Foundation of China.
文摘The plasma liquid phase oxidation of n-heptane was investigated. The selectivity of product formation is far superior to plasma oxidation in the gas phase.
基金Supported by National Natural Science Foundation and GM Fund (No.50322261).
文摘Effects of exhaust gas recirculation （EGR） on homogeneous charge combustion of n-heptane was studied through simulation and experiment. Experiments were carried out in a single cylinder, four-stroke, air cooled engine and a single cylinder, two-stroke, water cooled engine. In the four-stroke engine, experiments of the effects of EGR were examined using heated N2 addition as a surrogate for external EGR and modifying engine to increase internal EGR. The ignition timing was sensitive to EGR due to thermal and chemical effects. EGR or extra air is a key factor in eliminating knock during mid-load conditions. For higher load operation the only way to avoid knock is to control reaction timing through the use of spark ignition. Experimental and modeling results from the two-stroke engine show that auto-ignition can be avoided by increasing the engine speed. The two-stroke engine experiments indicate that high levels of internal EGR can enable spark ignition at lean conditions. At higher load conditions, increasing the engine speed is an effective method to control transition from homogeneous charge compression ignition （HCCI） operation to non-HCCI operation and successful spark ignition of a highly dilute mixture can avoid serious knock.
文摘Phospbomolybdate （PMo） with varying Mo loadings ranging from 5-30 wt% on alumina were prepared by incipient wetness impregnation method. 0.5 wt% of Pt was further loaded in order to prepare the bifunctional （metal-acid） Pt-PMo/Al2O3 catalysts. Thus prepared catalysts showed very high catalytic activities for n-heptane hydroisomerization compared with Pt impregnated MoO3 catalysts supported either on Al2O3 or on AIPO4. The conversion of n-heptane increased with Mo loading up to 20 wt% and slightly decreased with further Mo loading. However, the selectivity towards isomers showed an increasing trend up to 30 wt% of Mo in the catalyst. A relationship between catalytic activity and acidic strength was established in the present study.
