V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for N...V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for NOx conversion using NH3 as the reductant. Hydrothermal ageing decreased the NOx conversion of V2O5/WO3‐TiO2 catalyst severely over the entire measured tem‐perature range. Interestingly, the NH3‐SCR activity of the silica‐modified catalyst at 220–480℃ is enhanced after ageing. The catalysts were characterized by X‐ray diffraction, nitrogen adsorption, X‐ray fluorescence, Raman spectroscopy, H2 temperature‐programmed reduction, and NH3 temper‐ature‐programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V2O5/WO3‐TiO2 catalyst was significantly improved.展开更多
A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts c...A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 ℃ exhibited the highest conversion of acetylene （94.6%） and highest selectivity to vinyl fluoride （83.4%） and lower coke deposition selectivity （0.72%）. The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.展开更多
The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO_(2) from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonizatio...The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO_(2) from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonization.However,steelwork off-gases typically contain various impurities,including H_(2)S,which can deactivate commercial methanol synthesis catalysts,Cu/ZnO/Al_(2)O_(3)(CZA).Reverse water-gas shift(RWGS)reaction is the predominant side reaction in CO_(2) hydrogenation to methanol which can occur at ambient pressure,enabling the decouple of RWGS from methanol production at high pressure.Then,a series of activated CZA catalysts has been in-situ pretreated in 400 ppm H_(2)S/Ar at 250℃and tested for both RWGS reaction at ambient pressure and CO_(2) hydrogenation to methanol at high pressure.An innovative decoupling strategy was employed to isolate the RWGS reaction from the methanol synthesis process,enabling the investigation of the evolution of active site structures and the poisoning mechanism through elemental analysis,X-ray Diffraction,X-ray Photoelectron Spectroscopy,Fourier Transform Infrared Spectroscopy,Temperature Programmed Reduction and CO_(2) Temperature Programmed Desorption.The results indicate that there are different dynamic migration behaviors of ZnO_(x) in the two reaction systems,leading to different poisoning mechanisms.These interesting findings are beneficial to develop sulfur resistant and durable highly efficient catalysts for CO_(2) hydrogenation to methanol,promoting the carbon emission reduction in steel industry.展开更多
Deactivation mechanism of Cr-Al2O3catalyst and the interaction of Cr-A1 in the dehydrogenation of isobutane, as well as the nature of the catalytic active center, were studied using XRD, SEM, XPS, H2-TPR, isobutane-TP...Deactivation mechanism of Cr-Al2O3catalyst and the interaction of Cr-A1 in the dehydrogenation of isobutane, as well as the nature of the catalytic active center, were studied using XRD, SEM, XPS, H2-TPR, isobutane-TPR and TPO techniques. The results revealed that the deactivation of Cr-Al2O3 catalyst was mainly caused by carbon deposition on its surface. The Cr3＋ ion could not be reduced by hydrogen but could be reduced to Cr2＋ by hydrocarbons and monoxide carbon. The active center for isobutane dehydrogenation could be Cr2＋/Cr3＋ produced from Cr6＋ by the on line reduction of hydrocarbon and carbon monoxide. The binding energy of Al3＋ was strongly affected by the state of chromium cations in the catalysts.展开更多
A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization （in moderate conditions：200 ＆#176;C, 12 h） of red liquor solids, a by-product of paper-making process. The prepared sulfonate...A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization （in moderate conditions：200 ＆#176;C, 12 h） of red liquor solids, a by-product of paper-making process. The prepared sulfonated cata-lyst （SC） had aromatic structure, composed of carbon enriched inner core, and oxygen-containing （SO3H, COOH, OH） groups enriched surface. The SO3H, COOH, OH groups amounted to 0.74 mmol·g^-1, 0.78 mmol·g^-1, 2.18 mmol·g^-1, respectively. The fresh SC showed much higher catalytic activity than that of the traditional solid acid catalysts （strong-acid 732 cation exchange resin, hydrogen type zeolite socony mobile-five （HZSM-5）, sulfated zir-conia） in esterification of oleic acid. SC was deactivated during the reactions, through the mechanisms of leaching of sulfonated species and formation of sulfonate esters. Two regeneration methods were developed, and the catalytic activity can be mostly regenerated by regeneration Method 1 and be fully regenerated by regeneration Method 2, respectively.展开更多
Ni catalysts supported on Al2O3, ZrO2-Al2O3, CeO2-Al2O3 and ZrO2-CeO2-Al2O3 were prepared by coprecipitation method, and their catalytic performances for autothermal reforming of methane to hydrogen were investigated....Ni catalysts supported on Al2O3, ZrO2-Al2O3, CeO2-Al2O3 and ZrO2-CeO2-Al2O3 were prepared by coprecipitation method, and their catalytic performances for autothermal reforming of methane to hydrogen were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. The relationship between the structures and catalytic activities of the catalysts was discussed. The results showed that the catalytic activity and stability of the Ni/ZrO2-CeO2-Al2O3 catalyst was better than those of other catalysts with the highest CH4 conversion, H2/CO and H2/COx ratio at 750 ℃. The catalyst showed a little deactivation along the reaction time during its 72 h on stream with the mean deactivation rate of 0.08%/h. The catalytic performance of the Ni/ZrO2-CeO2-Al2O3 catalyst was also affected by reaction temperature, no2 ： nCH4 molar ratio and nH2O ： nCH4 molar ratio. TPR, XRD and XPS measurements indicated that the formation of ZrO2-CeO2 solid solution could improve the dispersion of NiO, and inhibit the formation of NiAl2O3, and thus significantly promoted the catalytic activity of the Ni/ZrO2-CeO2-Al2O3 catalyst.展开更多
Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various technique...Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various techniques, including N2 adsorption-desorption （Brunauer-Emmet-Teller method, BET）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and fourier transform infrared absorption spectroscopy （FT-IR）. Catalytic activity for microalgae oil conversion to methyl ester via transesterification was evaluated and analyzed by GC-MS and GC. BET results showed that the support possessed high specific surface area, suitable pore volume and pore size distribution. Activity results indicated that the catalyst with 25 wt% KOH showed the best activity for microalgae oil conversion. XRD and SEM results revealed that Al-O-K compound was the active phase for microalgae oil conversion. The agglomeration and changing of pore structure should be the main reasons for the catalyst deactivation when KOH content was higher than 30 wt%.展开更多
γ-A12O3-supported CeO2 catalysts were pre- pared by microemulsion and impregnation methods and characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM） techniques. At the same time, the des...γ-A12O3-supported CeO2 catalysts were pre- pared by microemulsion and impregnation methods and characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM） techniques. At the same time, the desulfurization activity of catalysts was investigated. The results show that nanoscale active substances and a high desulfurization effect are achieved by microemulsion, exhibiting a significant dominance compared with traditional impregnation method. The optimal preparation condition is temperature of 30 ℃ and ratio of [H20]/[surface active agent] of 7 with slow demulsification. The activated catalysts still keep high and stable desulfurization activity during a wide temperature range of 450-600 ℃. Among a series of prepared catalysts, the desulfurization rate of 6CeOz/γ-A1203 is the highest, reaching up to 80 % when temperature is higher than 550℃. The catalytic reduction mechanism of SO2 over nano-CeOz/γ-A1203 follows redox mechanism.展开更多
In this work, Pd–Cu/γ-Al2O3 is prepared by the impregnation method and investigated for selective oxygenization of cyclopentene to cyclopentanone. A series of bimetallic Pd–Cu/γ-Al_(2)O_(3) nanocatalysts were prep...In this work, Pd–Cu/γ-Al2O3 is prepared by the impregnation method and investigated for selective oxygenization of cyclopentene to cyclopentanone. A series of bimetallic Pd–Cu/γ-Al_(2)O_(3) nanocatalysts were prepared and the structures characterized by XRD, XPS and TEM. We determined that the obtained Pd–Cu/γ-Al_(2)O_(3)(molar ratio Pd:Cu = 5:1) was an efficient catalyst for the oxygenization of cyclopentene to cyclopentanone with 95% selectivity and 85% conversion(100 °C, 1 MPa initial O2 pressure, 7 h).展开更多
In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) st...In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.展开更多
A series of 3.0Mo/MCM-22-Al2O3 catalysts with γ-Al2O3 contents in the range of 0-100 wt% were prepared and applied in the metathesis reaction of ethene and butene-2. Addition of γ-Al2O3did not affect the structure o...A series of 3.0Mo/MCM-22-Al2O3 catalysts with γ-Al2O3 contents in the range of 0-100 wt% were prepared and applied in the metathesis reaction of ethene and butene-2. Addition of γ-Al2O3did not affect the structure of MCM-22 zeolite as evidenced by XRD and N2 adsorption measurements. It was deduced from TPR experiments that γ-Al2O3 phase favored the formation of polymolybdate or multilayered Mo oxide, while more Al2（MoO4）3 species were generated over MCM-22 zeolites. Alumina content in the support was directly related to the metathesis activity of ethene and butene-2 to propene. Mo species with higher valence （Mo6＋or Mo5＋） contributed more to the excellent performance of catalyst than metallic Mo. The best catalyst activity and stability was obtained over 3.0Mo/（MCM-22-30%Al2O3） under the reaction condition of 1.0 MPa and 125℃ using N2 as the pretreatment gas.展开更多
Ni/α-Al2O3 catalysts were found to be active in the temperature range 600 ～ 900℃ for both CO2 reforming and partial oxidation of methane.The effects of Ni loading,reaction temperature and feed gas ratio for the com...Ni/α-Al2O3 catalysts were found to be active in the temperature range 600 ～ 900℃ for both CO2 reforming and partial oxidation of methane.The effects of Ni loading,reaction temperature and feed gas ratio for the combination of CO2 reforming and partial oxidation of CH4 over Ni/α-Al2O3 were investigated.Catalysts of xwt%Ni/α-Al2O3（x=2.5,5,8 and 12） were prepared by wet impregnating the calcined support with a solution of nickel nitrate.XRD patterns and activity tests have verified that the 5wt%Ni/α-Al2O3 was the most active catalyst,as compared with the other prepared catalyst samples.An increase of the Ni loading to more than 5wt% led to a reduction in the Ni dispersion.In addition,by combining the endothermic carbon dioxide reforming reaction with the exothermic partial oxidation reaction,the loss of catalyst activity with time on stream was reduced with the amount of oxygen added to the feed.展开更多
Granular CuO-CeO2-MnOx/γ-Al2O3 catalysts were synthesized by the sol-gel method. The performance of the CuO-CeO2-MnOx/γ-Al2O3 catalysts for the selective catalytic reduction (SCR) was studied in a fixed bed system. ...Granular CuO-CeO2-MnOx/γ-Al2O3 catalysts were synthesized by the sol-gel method. The performance of the CuO-CeO2-MnOx/γ-Al2O3 catalysts for the selective catalytic reduction (SCR) was studied in a fixed bed system. Preliminary tests were carried out to analyze the behavior of NH3 and NO over catalyst in the presence of oxygen. The optimum temperature range for SCR over the CuO-CeO2-MnOx/γ-Al2O3 catalysts is 300-400 ℃ . The catalysts maintain nearly 100% NO conversion at 350 ℃. The NH3 oxidation experiments show that both NO and N2O are produced gradually with the increase of temperature. The catalysts in this experiment have a stronger oxidation property on NH3, which improves the denitrification activity at low temperature. The over-oxidation of NH3 at high temperature is the main cause leading to a decrease in the NO conversion. The NH3 and NO desorption experiments show that NH3 and NO can be adsorbed on CuO-CeO2-MnOx/γ-Al2O3 granular catalysts. The transient response of NH3 and NO indicates that the SCR reaction proceeds in accordance with the Eley-Rideal mechanism. The adsorbed NO has little influence on the denitrification activity in SCR process.展开更多
A coaxial dielectric barrier discharge (DBD) reactor was used for plasma-catalytic degradation of tetracycline hydrochloride over a series of Mn/γ-Al2O3 catalysts prepared by the incipient wetness impregnation method...A coaxial dielectric barrier discharge (DBD) reactor was used for plasma-catalytic degradation of tetracycline hydrochloride over a series of Mn/γ-Al2O3 catalysts prepared by the incipient wetness impregnation method.The combination of plasma and the Mn/γ-Al2O3 catalysts significantly enhanced the degradation efficiency of tetracycline hydrochloride compared to the plasma process alone,with the 10% Mn/γ-Al2O3 catalyst exhibiting the best tetracycline hydrochloride degradation efficiency.A maximum degradation efficiency of 99.3% can be achieved after 5 min oxidation and a discharge power of 1.3 W,with only 69.7% by a single plasma process.The highest energy yield of the plasma-catalytic process is 91.7 g kWh-1.Probable reaction mechanisms of the plasma-catalytic removal of tetracycline hydrochloride were also proposed.展开更多
A series of Pd/La-Al2O3（PLA） catalysts with La-Al2O3（LA） support calcined at different temperatures（500, 700, 900 and 1050 oC） were prepared using an incipient wetness impregnation method. The activity of the fr...A series of Pd/La-Al2O3（PLA） catalysts with La-Al2O3（LA） support calcined at different temperatures（500, 700, 900 and 1050 oC） were prepared using an incipient wetness impregnation method. The activity of the fresh and hydrothermally aged PLA catalysts were tested for total oxidation of CO and C3H8. The activity of the fresh PLA catalysts for CO and C3H8 oxidation increased with increasing calcination temperature of the support, while the activities of the aged catalysts declined and became essentially the same. CO chemisorption results revealed that the suppressed activities of the aged catalysts were mainly due to the decline of palladium dispersion. The turnover frequency（TOF） of CO oxidation increased with increasing reduction ability of the catalysts, with a fresh catalyst calcined at 1050 oC having the highest value（0.048 s–1）. However, the TOF of C3H8 total oxidation was affected by not only the redox properties of catalysts but also the size of Pd particle, and large Pd particles possessed higher TOF value of C3H8 oxidation, with the highest value（0.125 s–1） being obtained on an aged catalyst calcined at 500 oC.展开更多
Three different regeneration processes including hydrogen or nitrogen purging and coke-burning treatment were used to restore the Pt-Sn/γ-AlOcatalysts, through which propane dehydrogenation reaction was performed in ...Three different regeneration processes including hydrogen or nitrogen purging and coke-burning treatment were used to restore the Pt-Sn/γ-AlOcatalysts, through which propane dehydrogenation reaction was performed in a consecutive reaction-regeneration mode. It was found that the catalyst using hydrogen regeneration showed the best stability compared with those regenerated by nitrogen purging and coke-burning treatment, suggesting that hydrogen regeneration is an effective approach for maintaining the performance of Pt-Sn/γ-AlOcatalysts in propane dehydrogenation reaction. The effect of different regeneration atmospheres on the metal active center and the coke deposition was investigated by XRD,TEM, N-physisorption, TPO, TG and Raman technologies, and the results revealed that hydrogen or nitrogen regeneration resulted in little impact on the size and structure of metal active center, retaining the effective Pt Sn phase over the catalyst. Moreover, hydrogen regeneration not only removed the low dense components of the coke, but also altered the property of the residual coke through hydrogenation, leading to a higher mobility of coke, and thus a higher accessibility of the metal active centers. Whereas nitrogen regeneration only removed the low dense components of the coke. Although coke-burning regeneration caused a thorough coke removal, the catalyst subjected to repeated redox exhibited poor stability due to metal agglomeration, phase segregation and the resulting large PtSn particle and core-shell structure with a Sn-rich surface.展开更多
The crystal size distribution（CSD）was determined with small angle X-ray scattering technique.Theanticoking property of Ni-catalysts was investigated with the steam reforming of n-heptane in a TG-monitoredflow reacto...The crystal size distribution（CSD）was determined with small angle X-ray scattering technique.Theanticoking property of Ni-catalysts was investigated with the steam reforming of n-heptane in a TG-monitoredflow reactor.The results of this study show that the rate of coking on the supported Ni-catalysts depends main-ly on the percentage content of the large size fraction（25-70nm）of Ni-crystallites,and that the dispersion ofNi-crystallites and the anticoking property of the Ni/α-Al<sub>2</sub>O<sub>3</sub> catalysts were promoted obviously by theLa<sub>2</sub>O<sub>3</sub>-modification method.The variation of the Ni-CSD and the anticoking property of the catalysts were fur-ther tested through different periods of hydrothermal treatment.It is found that the content of the largeNi-crystal size fraction and the coking rate pass correspondingly through a maximum.展开更多
The various surface species[H_XRu_3(CO)_9(CCO)]^(2-X)(X=0-2)prepared from impregnation of[PPN]_2[Ru_3(CO)_9(CCO)]on SiO_2-Al_2O_3,SiO_2 and MgO show quite different activities and selectivities for oxygenates and etha...The various surface species[H_XRu_3(CO)_9(CCO)]^(2-X)(X=0-2)prepared from impregnation of[PPN]_2[Ru_3(CO)_9(CCO)]on SiO_2-Al_2O_3,SiO_2 and MgO show quite different activities and selectivities for oxygenates and ethane in ethylene hydroformylation.展开更多
V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy ...V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy （XPS） and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature （〈300 ？C） were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ？C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4＋ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4＋ and Pd2＋ species on the surface, which might be favorable for the formation of active sites.展开更多
基金supported by the National Natural Science Foundation of China (51372137)the National High Technology Research and Development Program of China (863 Program,2015AA034603)~~
文摘V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for NOx conversion using NH3 as the reductant. Hydrothermal ageing decreased the NOx conversion of V2O5/WO3‐TiO2 catalyst severely over the entire measured tem‐perature range. Interestingly, the NH3‐SCR activity of the silica‐modified catalyst at 220–480℃ is enhanced after ageing. The catalysts were characterized by X‐ray diffraction, nitrogen adsorption, X‐ray fluorescence, Raman spectroscopy, H2 temperature‐programmed reduction, and NH3 temper‐ature‐programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V2O5/WO3‐TiO2 catalyst was significantly improved.
基金ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China （No.20873125）,
文摘A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 ℃ exhibited the highest conversion of acetylene （94.6%） and highest selectivity to vinyl fluoride （83.4%） and lower coke deposition selectivity （0.72%）. The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.
基金supported by the National Natural Science Foundation of China(Nos.22276060 and 21976059)Guangdong Basic and Applied Basic Research Foundation(No.2024A1515012636)China Scholarship Council Scholarship(No.201906155006)。
文摘The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO_(2) from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonization.However,steelwork off-gases typically contain various impurities,including H_(2)S,which can deactivate commercial methanol synthesis catalysts,Cu/ZnO/Al_(2)O_(3)(CZA).Reverse water-gas shift(RWGS)reaction is the predominant side reaction in CO_(2) hydrogenation to methanol which can occur at ambient pressure,enabling the decouple of RWGS from methanol production at high pressure.Then,a series of activated CZA catalysts has been in-situ pretreated in 400 ppm H_(2)S/Ar at 250℃and tested for both RWGS reaction at ambient pressure and CO_(2) hydrogenation to methanol at high pressure.An innovative decoupling strategy was employed to isolate the RWGS reaction from the methanol synthesis process,enabling the investigation of the evolution of active site structures and the poisoning mechanism through elemental analysis,X-ray Diffraction,X-ray Photoelectron Spectroscopy,Fourier Transform Infrared Spectroscopy,Temperature Programmed Reduction and CO_(2) Temperature Programmed Desorption.The results indicate that there are different dynamic migration behaviors of ZnO_(x) in the two reaction systems,leading to different poisoning mechanisms.These interesting findings are beneficial to develop sulfur resistant and durable highly efficient catalysts for CO_(2) hydrogenation to methanol,promoting the carbon emission reduction in steel industry.
基金supported by the Natural Science Foundation of Shandong Provence of China(ZR2013BM008)
文摘Deactivation mechanism of Cr-Al2O3catalyst and the interaction of Cr-A1 in the dehydrogenation of isobutane, as well as the nature of the catalytic active center, were studied using XRD, SEM, XPS, H2-TPR, isobutane-TPR and TPO techniques. The results revealed that the deactivation of Cr-Al2O3 catalyst was mainly caused by carbon deposition on its surface. The Cr3＋ ion could not be reduced by hydrogen but could be reduced to Cr2＋ by hydrocarbons and monoxide carbon. The active center for isobutane dehydrogenation could be Cr2＋/Cr3＋ produced from Cr6＋ by the on line reduction of hydrocarbon and carbon monoxide. The binding energy of Al3＋ was strongly affected by the state of chromium cations in the catalysts.
基金Supported by the National Natural Science Foundation of China(21276076)the Fundamental Research Funds for the Central Universities of China(WA1014003)State Key Laboratory of Chemical Engineering(SKL-ChE-10C06)
文摘A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization （in moderate conditions：200 ＆#176;C, 12 h） of red liquor solids, a by-product of paper-making process. The prepared sulfonated cata-lyst （SC） had aromatic structure, composed of carbon enriched inner core, and oxygen-containing （SO3H, COOH, OH） groups enriched surface. The SO3H, COOH, OH groups amounted to 0.74 mmol·g^-1, 0.78 mmol·g^-1, 2.18 mmol·g^-1, respectively. The fresh SC showed much higher catalytic activity than that of the traditional solid acid catalysts （strong-acid 732 cation exchange resin, hydrogen type zeolite socony mobile-five （HZSM-5）, sulfated zir-conia） in esterification of oleic acid. SC was deactivated during the reactions, through the mechanisms of leaching of sulfonated species and formation of sulfonate esters. Two regeneration methods were developed, and the catalytic activity can be mostly regenerated by regeneration Method 1 and be fully regenerated by regeneration Method 2, respectively.
基金supported by Guangdong Provincial Natural Science Foundation of China(030514)Science and Technology Plan of Guangdong Province of China(2004B33401006)Doctoral Startup Foundation of Guang Dong Pharmaceutical University.
文摘Ni catalysts supported on Al2O3, ZrO2-Al2O3, CeO2-Al2O3 and ZrO2-CeO2-Al2O3 were prepared by coprecipitation method, and their catalytic performances for autothermal reforming of methane to hydrogen were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. The relationship between the structures and catalytic activities of the catalysts was discussed. The results showed that the catalytic activity and stability of the Ni/ZrO2-CeO2-Al2O3 catalyst was better than those of other catalysts with the highest CH4 conversion, H2/CO and H2/COx ratio at 750 ℃. The catalyst showed a little deactivation along the reaction time during its 72 h on stream with the mean deactivation rate of 0.08%/h. The catalytic performance of the Ni/ZrO2-CeO2-Al2O3 catalyst was also affected by reaction temperature, no2 ： nCH4 molar ratio and nH2O ： nCH4 molar ratio. TPR, XRD and XPS measurements indicated that the formation of ZrO2-CeO2 solid solution could improve the dispersion of NiO, and inhibit the formation of NiAl2O3, and thus significantly promoted the catalytic activity of the Ni/ZrO2-CeO2-Al2O3 catalyst.
基金supported by the Institute of Chemical Materials Foundation of CAEP(No.626010937)
文摘Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various techniques, including N2 adsorption-desorption （Brunauer-Emmet-Teller method, BET）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and fourier transform infrared absorption spectroscopy （FT-IR）. Catalytic activity for microalgae oil conversion to methyl ester via transesterification was evaluated and analyzed by GC-MS and GC. BET results showed that the support possessed high specific surface area, suitable pore volume and pore size distribution. Activity results indicated that the catalyst with 25 wt% KOH showed the best activity for microalgae oil conversion. XRD and SEM results revealed that Al-O-K compound was the active phase for microalgae oil conversion. The agglomeration and changing of pore structure should be the main reasons for the catalyst deactivation when KOH content was higher than 30 wt%.
基金financially supported by the Natural Science Foundation of Hubei Province, China(No. 2009CDB246)the Applied Basic Research Project of Wuhan City (No. 2015060101010068)
文摘γ-A12O3-supported CeO2 catalysts were pre- pared by microemulsion and impregnation methods and characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM） techniques. At the same time, the desulfurization activity of catalysts was investigated. The results show that nanoscale active substances and a high desulfurization effect are achieved by microemulsion, exhibiting a significant dominance compared with traditional impregnation method. The optimal preparation condition is temperature of 30 ℃ and ratio of [H20]/[surface active agent] of 7 with slow demulsification. The activated catalysts still keep high and stable desulfurization activity during a wide temperature range of 450-600 ℃. Among a series of prepared catalysts, the desulfurization rate of 6CeOz/γ-A1203 is the highest, reaching up to 80 % when temperature is higher than 550℃. The catalytic reduction mechanism of SO2 over nano-CeOz/γ-A1203 follows redox mechanism.
基金financial assistance from the National Natural Science Foundation of China (Nos. 21272050, 21371044, 21472033 and 21571047)
文摘In this work, Pd–Cu/γ-Al2O3 is prepared by the impregnation method and investigated for selective oxygenization of cyclopentene to cyclopentanone. A series of bimetallic Pd–Cu/γ-Al_(2)O_(3) nanocatalysts were prepared and the structures characterized by XRD, XPS and TEM. We determined that the obtained Pd–Cu/γ-Al_(2)O_(3)(molar ratio Pd:Cu = 5:1) was an efficient catalyst for the oxygenization of cyclopentene to cyclopentanone with 95% selectivity and 85% conversion(100 °C, 1 MPa initial O2 pressure, 7 h).
基金the National Natural Science Foundation of China (51676090)the Natural Science Foundation of Jiangsu Province (BK20150513), and the Six Talent Peaks Project in Jiangsu Province.
文摘In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.
基金supported by the National Natural Science Foundation of China (Grant No. 20903088 and 20773120)the Ministry of Science and Technology of China through the National Key Project of Fundamental Research (Grant No.2009CB623507)
文摘A series of 3.0Mo/MCM-22-Al2O3 catalysts with γ-Al2O3 contents in the range of 0-100 wt% were prepared and applied in the metathesis reaction of ethene and butene-2. Addition of γ-Al2O3did not affect the structure of MCM-22 zeolite as evidenced by XRD and N2 adsorption measurements. It was deduced from TPR experiments that γ-Al2O3 phase favored the formation of polymolybdate or multilayered Mo oxide, while more Al2（MoO4）3 species were generated over MCM-22 zeolites. Alumina content in the support was directly related to the metathesis activity of ethene and butene-2 to propene. Mo species with higher valence （Mo6＋or Mo5＋） contributed more to the excellent performance of catalyst than metallic Mo. The best catalyst activity and stability was obtained over 3.0Mo/（MCM-22-30%Al2O3） under the reaction condition of 1.0 MPa and 125℃ using N2 as the pretreatment gas.
文摘Ni/α-Al2O3 catalysts were found to be active in the temperature range 600 ～ 900℃ for both CO2 reforming and partial oxidation of methane.The effects of Ni loading,reaction temperature and feed gas ratio for the combination of CO2 reforming and partial oxidation of CH4 over Ni/α-Al2O3 were investigated.Catalysts of xwt%Ni/α-Al2O3（x=2.5,5,8 and 12） were prepared by wet impregnating the calcined support with a solution of nickel nitrate.XRD patterns and activity tests have verified that the 5wt%Ni/α-Al2O3 was the most active catalyst,as compared with the other prepared catalyst samples.An increase of the Ni loading to more than 5wt% led to a reduction in the Ni dispersion.In addition,by combining the endothermic carbon dioxide reforming reaction with the exothermic partial oxidation reaction,the loss of catalyst activity with time on stream was reduced with the amount of oxygen added to the feed.
基金Projects (50776037,50721005) supported by the National Natural Science Foundation of China
文摘Granular CuO-CeO2-MnOx/γ-Al2O3 catalysts were synthesized by the sol-gel method. The performance of the CuO-CeO2-MnOx/γ-Al2O3 catalysts for the selective catalytic reduction (SCR) was studied in a fixed bed system. Preliminary tests were carried out to analyze the behavior of NH3 and NO over catalyst in the presence of oxygen. The optimum temperature range for SCR over the CuO-CeO2-MnOx/γ-Al2O3 catalysts is 300-400 ℃ . The catalysts maintain nearly 100% NO conversion at 350 ℃. The NH3 oxidation experiments show that both NO and N2O are produced gradually with the increase of temperature. The catalysts in this experiment have a stronger oxidation property on NH3, which improves the denitrification activity at low temperature. The over-oxidation of NH3 at high temperature is the main cause leading to a decrease in the NO conversion. The NH3 and NO desorption experiments show that NH3 and NO can be adsorbed on CuO-CeO2-MnOx/γ-Al2O3 granular catalysts. The transient response of NH3 and NO indicates that the SCR reaction proceeds in accordance with the Eley-Rideal mechanism. The adsorbed NO has little influence on the denitrification activity in SCR process.
文摘A coaxial dielectric barrier discharge (DBD) reactor was used for plasma-catalytic degradation of tetracycline hydrochloride over a series of Mn/γ-Al2O3 catalysts prepared by the incipient wetness impregnation method.The combination of plasma and the Mn/γ-Al2O3 catalysts significantly enhanced the degradation efficiency of tetracycline hydrochloride compared to the plasma process alone,with the 10% Mn/γ-Al2O3 catalyst exhibiting the best tetracycline hydrochloride degradation efficiency.A maximum degradation efficiency of 99.3% can be achieved after 5 min oxidation and a discharge power of 1.3 W,with only 69.7% by a single plasma process.The highest energy yield of the plasma-catalytic process is 91.7 g kWh-1.Probable reaction mechanisms of the plasma-catalytic removal of tetracycline hydrochloride were also proposed.
基金Project supported by National Natural Science Foundation of China(21173195,21203167)
文摘A series of Pd/La-Al2O3（PLA） catalysts with La-Al2O3（LA） support calcined at different temperatures（500, 700, 900 and 1050 oC） were prepared using an incipient wetness impregnation method. The activity of the fresh and hydrothermally aged PLA catalysts were tested for total oxidation of CO and C3H8. The activity of the fresh PLA catalysts for CO and C3H8 oxidation increased with increasing calcination temperature of the support, while the activities of the aged catalysts declined and became essentially the same. CO chemisorption results revealed that the suppressed activities of the aged catalysts were mainly due to the decline of palladium dispersion. The turnover frequency（TOF） of CO oxidation increased with increasing reduction ability of the catalysts, with a fresh catalyst calcined at 1050 oC having the highest value（0.048 s–1）. However, the TOF of C3H8 total oxidation was affected by not only the redox properties of catalysts but also the size of Pd particle, and large Pd particles possessed higher TOF value of C3H8 oxidation, with the highest value（0.125 s–1） being obtained on an aged catalyst calcined at 500 oC.
基金supported by the National Natural Science Foundation of China(nos.21103182,21273049)the Natural Science Foundation of Guangdong Province(no.S2013050014127)Education Department Funding of Guangdong Province(nos.CGZHZD1104,2013CXZDA016).
文摘Three different regeneration processes including hydrogen or nitrogen purging and coke-burning treatment were used to restore the Pt-Sn/γ-AlOcatalysts, through which propane dehydrogenation reaction was performed in a consecutive reaction-regeneration mode. It was found that the catalyst using hydrogen regeneration showed the best stability compared with those regenerated by nitrogen purging and coke-burning treatment, suggesting that hydrogen regeneration is an effective approach for maintaining the performance of Pt-Sn/γ-AlOcatalysts in propane dehydrogenation reaction. The effect of different regeneration atmospheres on the metal active center and the coke deposition was investigated by XRD,TEM, N-physisorption, TPO, TG and Raman technologies, and the results revealed that hydrogen or nitrogen regeneration resulted in little impact on the size and structure of metal active center, retaining the effective Pt Sn phase over the catalyst. Moreover, hydrogen regeneration not only removed the low dense components of the coke, but also altered the property of the residual coke through hydrogenation, leading to a higher mobility of coke, and thus a higher accessibility of the metal active centers. Whereas nitrogen regeneration only removed the low dense components of the coke. Although coke-burning regeneration caused a thorough coke removal, the catalyst subjected to repeated redox exhibited poor stability due to metal agglomeration, phase segregation and the resulting large PtSn particle and core-shell structure with a Sn-rich surface.
文摘The crystal size distribution（CSD）was determined with small angle X-ray scattering technique.Theanticoking property of Ni-catalysts was investigated with the steam reforming of n-heptane in a TG-monitoredflow reactor.The results of this study show that the rate of coking on the supported Ni-catalysts depends main-ly on the percentage content of the large size fraction（25-70nm）of Ni-crystallites,and that the dispersion ofNi-crystallites and the anticoking property of the Ni/α-Al<sub>2</sub>O<sub>3</sub> catalysts were promoted obviously by theLa<sub>2</sub>O<sub>3</sub>-modification method.The variation of the Ni-CSD and the anticoking property of the catalysts were fur-ther tested through different periods of hydrothermal treatment.It is found that the content of the largeNi-crystal size fraction and the coking rate pass correspondingly through a maximum.
文摘The various surface species[H_XRu_3(CO)_9(CCO)]^(2-X)(X=0-2)prepared from impregnation of[PPN]_2[Ru_3(CO)_9(CCO)]on SiO_2-Al_2O_3,SiO_2 and MgO show quite different activities and selectivities for oxygenates and ethane in ethylene hydroformylation.
基金supported by the National Natural Science Foundation of China (No. 21073131)the Shanxi Natural Science Foundation(No. 2009011011-3)
文摘V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy （XPS） and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature （〈300 ？C） were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ？C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4＋ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4＋ and Pd2＋ species on the surface, which might be favorable for the formation of active sites.
