Login In
2017 Volume 45 Issue 5
2017, 45(5): 513-522
Abstract:
The char samples were prepared from the partial gasification of Shengli lignite in a fluidised-bed/fixed-bed reactor, and characterised by BET, Raman, FT-IR, microwave digestion ICP-AES, and TGA. The results indicate that at 800 ℃ and steam atmosphere the decomposition of ether group is made by the inherent char activation, leading to the decrease in the content of short chain or amorphous carbon between aromatic rings to prevent the graphitizing and the enhancement in the degree of defective aromatic structure. With the increasing of steam concentration (10%-25%) the char reactivity is reduced, which is attributed to the weakening of the regeneration of active sites by forming more ether group via the reaction "Ar, R-CO-Ar, R+2H2O→Ar, R-O-Ar, R+2H2+CO2". However, with the continual increasing of steam concentration (25%-40%) the char reactivity is slightly promoted because the content of defective aromatic structure (3-5 rings) is increased due to the enhancement of the reaction (Ar, R-CH=CH2+H2O→Ar, R-CO-CH3+H2) and the reaction (Ar, R-+H-→Ar, R-H).
The char samples were prepared from the partial gasification of Shengli lignite in a fluidised-bed/fixed-bed reactor, and characterised by BET, Raman, FT-IR, microwave digestion ICP-AES, and TGA. The results indicate that at 800 ℃ and steam atmosphere the decomposition of ether group is made by the inherent char activation, leading to the decrease in the content of short chain or amorphous carbon between aromatic rings to prevent the graphitizing and the enhancement in the degree of defective aromatic structure. With the increasing of steam concentration (10%-25%) the char reactivity is reduced, which is attributed to the weakening of the regeneration of active sites by forming more ether group via the reaction "Ar, R-CO-Ar, R+2H2O→Ar, R-O-Ar, R+2H2+CO2". However, with the continual increasing of steam concentration (25%-40%) the char reactivity is slightly promoted because the content of defective aromatic structure (3-5 rings) is increased due to the enhancement of the reaction (Ar, R-CH=CH2+H2O→Ar, R-CO-CH3+H2) and the reaction (Ar, R-+H-→Ar, R-H).
2017, 45(5): 523-528
Abstract:
Yima (YM) coal and Pingshuo (PS) coal as well as their deashed coals and depyrited coals were used to investigate the effects of CO2 and Ar on the sulfur release behavior during coal pyrolysis by pyrolysis connected with mass spectrometer (Py-MS) and pyrolysis connected with gas chromatogram (Py-GC). It is found that CO2 atmosphere can promote the release of H2S, COS and SO2, especially the remarkable releasing of COS. In addition, CO2 atmosphere can decrease the maximum release peak temperature of H2S, COS and SO2 for raw coals, while there is no obvious effect for their deashed coals. At the same time, CO2 is beneficial to the decomposition of organic sulfur at higher temperature. That the COS formation is related to CO at higher temperatures and has nothing to do with CO at lower temperatures is validated.
Yima (YM) coal and Pingshuo (PS) coal as well as their deashed coals and depyrited coals were used to investigate the effects of CO2 and Ar on the sulfur release behavior during coal pyrolysis by pyrolysis connected with mass spectrometer (Py-MS) and pyrolysis connected with gas chromatogram (Py-GC). It is found that CO2 atmosphere can promote the release of H2S, COS and SO2, especially the remarkable releasing of COS. In addition, CO2 atmosphere can decrease the maximum release peak temperature of H2S, COS and SO2 for raw coals, while there is no obvious effect for their deashed coals. At the same time, CO2 is beneficial to the decomposition of organic sulfur at higher temperature. That the COS formation is related to CO at higher temperatures and has nothing to do with CO at lower temperatures is validated.
2017, 45(5): 529-536
Abstract:
Based on the simple collision theory (SCT), the calculation method of biomass char gasification rate was developed and the combined parameters to characterize the pre-exponential factor were found. Furthermore, some experimental tests for six acid-washed biomass chars, such as the isothermal gasification and so on, were performed under CO2 atmosphere, using a thermo-gravimetric analyzer (TGA) over the temperature ranges of 800-1000 ℃, respectively. Through the comparison of experimental data and modeling results, it is found that a good agreement is made and the developed model equations can provide an effective guidance to clarify the general gasification law of biomass chars.
Based on the simple collision theory (SCT), the calculation method of biomass char gasification rate was developed and the combined parameters to characterize the pre-exponential factor were found. Furthermore, some experimental tests for six acid-washed biomass chars, such as the isothermal gasification and so on, were performed under CO2 atmosphere, using a thermo-gravimetric analyzer (TGA) over the temperature ranges of 800-1000 ℃, respectively. Through the comparison of experimental data and modeling results, it is found that a good agreement is made and the developed model equations can provide an effective guidance to clarify the general gasification law of biomass chars.
2017, 45(5): 556-563
Abstract:
Series of Ru-based F-T synthesis catalysts, respectively with different supports of SiO2, Al2O3 and Beta zeolite, were prepared by impregnation method. Characterization techniques such as N2-adsorption, XRD, NH3-TPD, H2-TPR, H2-TPD, XPS and CO-DRIFTS were used to study the textural structure, phase, acidity, reduction behavior, chemical adsorption and electron properties of the catalysts. F-T synthesis performances of the catalysts were investigated as well. The results indicated that the supports imposed obvious effects on the reduction and dispersion of Ru, therefore led to the differences in acidity and surface properties of the catalysts. F-T reaction performance showed that the relatively stable Ru/SiO2 catalyst exhibited high selectivity to heavy hydrocarbons, ascribing to its less acidity, weaker metal-support interaction, and better Ru particle dispersion.
Series of Ru-based F-T synthesis catalysts, respectively with different supports of SiO2, Al2O3 and Beta zeolite, were prepared by impregnation method. Characterization techniques such as N2-adsorption, XRD, NH3-TPD, H2-TPR, H2-TPD, XPS and CO-DRIFTS were used to study the textural structure, phase, acidity, reduction behavior, chemical adsorption and electron properties of the catalysts. F-T synthesis performances of the catalysts were investigated as well. The results indicated that the supports imposed obvious effects on the reduction and dispersion of Ru, therefore led to the differences in acidity and surface properties of the catalysts. F-T reaction performance showed that the relatively stable Ru/SiO2 catalyst exhibited high selectivity to heavy hydrocarbons, ascribing to its less acidity, weaker metal-support interaction, and better Ru particle dispersion.
2017, 45(5): 564-571
Abstract:
The B3PW91/LANL2DZ (ECP) method has been used to calculate the geometric parameters of adsorption and dehydrogenation of methanol on PtnCum(n+m=4). All the calculations have been used the Gaussian09 program package. Compared the adsorption energy with dehydrogenation energy barrier, it can be concluded that the path of the adsorption of methyl on the Pt site and the C-H broken is the most favorable reaction in all of the possible paths. When the catalyst of PtnCum (n+m=4) have different Pt and Cu proportions we find the catalytic activity is the best with the Pt and Cu ratio of 1:1.
The B3PW91/LANL2DZ (ECP) method has been used to calculate the geometric parameters of adsorption and dehydrogenation of methanol on PtnCum(n+m=4). All the calculations have been used the Gaussian09 program package. Compared the adsorption energy with dehydrogenation energy barrier, it can be concluded that the path of the adsorption of methyl on the Pt site and the C-H broken is the most favorable reaction in all of the possible paths. When the catalyst of PtnCum (n+m=4) have different Pt and Cu proportions we find the catalytic activity is the best with the Pt and Cu ratio of 1:1.
2017, 45(5): 572-580
Abstract:
MoO3-SnO2 catalysts with a Mo/Sn molar ratio of 1:3 was prepared by the co-precipitation method and calcined in different atmospheres (O2, air, N2 and H2); the effect of calcination atmosphere on the catalytic performance of MoO3-SnO2 in the oxidation of dimethyl ether (DME) to methyl formate (MF) was investigated. The results show that the MoO3-SnO2 catalyst prepared by calcination in O2 exhibits the highest activity; the conversion of DME reaches 25.10%, with the selectivity of 72.21% to MF. Over the catalyst calcined in H2, the conversion of DME is only 7.01%, with the selectivity of 75.82% to MF. The activity of the MoO3-SnO2 catalysts calcined at different atmospheres follows the order of O2 > air > N2 > H2. The results of XRD, Raman, XPS and ESR characterization indicate the presence of MoOx domains on the surface of the MoO3-SnO2 catalyst with a Mo/Sn molar ratio of 1:3. The terminal Mo=O groups of oligomeric MoO3 may be the active sites for the methoxy intermediate and the penta-coordinated Mo5+ species in the Mo-Sn interface may be able to promote the oxidation of DME to MF. Consequently, methoxy species are absorbed on the Mo5+ species in the Mo-Sn interfaces, which are oxidized to HCHO on the terminal Mo=O groups; after that, the absorbed HCHO may then react with the neighboring absorbed methoxy species, forming MF.
MoO3-SnO2 catalysts with a Mo/Sn molar ratio of 1:3 was prepared by the co-precipitation method and calcined in different atmospheres (O2, air, N2 and H2); the effect of calcination atmosphere on the catalytic performance of MoO3-SnO2 in the oxidation of dimethyl ether (DME) to methyl formate (MF) was investigated. The results show that the MoO3-SnO2 catalyst prepared by calcination in O2 exhibits the highest activity; the conversion of DME reaches 25.10%, with the selectivity of 72.21% to MF. Over the catalyst calcined in H2, the conversion of DME is only 7.01%, with the selectivity of 75.82% to MF. The activity of the MoO3-SnO2 catalysts calcined at different atmospheres follows the order of O2 > air > N2 > H2. The results of XRD, Raman, XPS and ESR characterization indicate the presence of MoOx domains on the surface of the MoO3-SnO2 catalyst with a Mo/Sn molar ratio of 1:3. The terminal Mo=O groups of oligomeric MoO3 may be the active sites for the methoxy intermediate and the penta-coordinated Mo5+ species in the Mo-Sn interface may be able to promote the oxidation of DME to MF. Consequently, methoxy species are absorbed on the Mo5+ species in the Mo-Sn interfaces, which are oxidized to HCHO on the terminal Mo=O groups; after that, the absorbed HCHO may then react with the neighboring absorbed methoxy species, forming MF.
2017, 45(5): 589-595
Abstract:
Three amorphous silica-alumina supports with similar textural properties and different amounts of acidity were successfully synthesized through ammonium exchange processing and their structures, acidity properties and the coordination of Si and Al in the as-synthesized supports were characterized using XRD, N2 adsorption-desorption, NH3-TPD, Py-FTIR and NMR. Amorphous silica-alumina was impregnated into a solution of H12N4PtCl2·XH2O to obtain hydrocracking catalysts. The relationship between acidic properties of supports and catalytic performance was studied by hydrocracking of Fischer-Tropsch (F-T) wax to diesel in a continuous-flow type fixed-bed reactor as a model reaction. The results illustrated that the diesel selectivity was mainly related to Brønsted acid properties of the supports while Lewis acid showed little correlation. The amount of strong Brønsted acid was reversely related to the selectivity of diesel:the smaller the amount, the higher the selectivity. The as-synthesized Pt/B-1 catalyst showed high selectivity of 87.12% to diesel at the conversion of F-T wax of about 62.52%, under the reaction conditions of 370℃, 7.0 MPa, LHSV of 1.0 h-1 and a hydrogen-to-wax ratio of 1 000:1. Pt/B-1 had better catalytic performance than Pt/ASA prepared by commercial amorphous silica-alumina (ASA).
Three amorphous silica-alumina supports with similar textural properties and different amounts of acidity were successfully synthesized through ammonium exchange processing and their structures, acidity properties and the coordination of Si and Al in the as-synthesized supports were characterized using XRD, N2 adsorption-desorption, NH3-TPD, Py-FTIR and NMR. Amorphous silica-alumina was impregnated into a solution of H12N4PtCl2·XH2O to obtain hydrocracking catalysts. The relationship between acidic properties of supports and catalytic performance was studied by hydrocracking of Fischer-Tropsch (F-T) wax to diesel in a continuous-flow type fixed-bed reactor as a model reaction. The results illustrated that the diesel selectivity was mainly related to Brønsted acid properties of the supports while Lewis acid showed little correlation. The amount of strong Brønsted acid was reversely related to the selectivity of diesel:the smaller the amount, the higher the selectivity. The as-synthesized Pt/B-1 catalyst showed high selectivity of 87.12% to diesel at the conversion of F-T wax of about 62.52%, under the reaction conditions of 370℃, 7.0 MPa, LHSV of 1.0 h-1 and a hydrogen-to-wax ratio of 1 000:1. Pt/B-1 had better catalytic performance than Pt/ASA prepared by commercial amorphous silica-alumina (ASA).
2017, 45(5): 608-615
Abstract:
TiO2-CeO2 mixed oxides were prepared by urea gelation and co-precipitation method and then characterized by N2 sorption and X-ray diffraction (XRD). The synergy of photocatalysis and adsorption on TiO2-CeO2 adsorbents for the removal of organosulfur compounds from diesel fuel was investigated. The results show that the UV irradiation can greatly enhance the adsorption of organosulfur in model fuel on TiO2-CeO2; the organosulfur compounds is first photocatalytically oxidized to polar sulfoxides and sulfones over TiO2-CeO2, which are then selectively adsorbed on the bifucntional TiO2-CeO2 material due to their much higher polarities than the original oranosulfur compounds and other organic compounds in the diesel fuel. The TiO2-CeO2 material with a Ti/Ce molar ratio of 9:1 and calcined at 500℃ exhibits the highest synergistic photocatalysis-adsorption desulfurization performance; over it the sulfur removal rate reaches 99.6% for a model fuel after reaction for 5 h under UV irradiation. The low desulfurization selctivity because of the strongly competitive adsorption of aromatics in the diesel fule could be greatly improved by employing the synergistic photocatalysis-adsorption desulfurization process; the sulfur removal rate is still higher than 96.6% for the model fuel containing 25% toluene after reaction for 7 h under UV irradiation. The desulfurization performance of TiO2-CeO2 for different organosulfur compounds in the diesel fuel follows the order of 4, 6-DMDBT > DBT > BT. Moreover, TiO2-CeO2 can be well regenrated by washing with acetonitrile followed by heat treatment in air; it still gives a high synergistic photocatalysis-adsorption desulfurization performance even after four regeneration cycles.
TiO2-CeO2 mixed oxides were prepared by urea gelation and co-precipitation method and then characterized by N2 sorption and X-ray diffraction (XRD). The synergy of photocatalysis and adsorption on TiO2-CeO2 adsorbents for the removal of organosulfur compounds from diesel fuel was investigated. The results show that the UV irradiation can greatly enhance the adsorption of organosulfur in model fuel on TiO2-CeO2; the organosulfur compounds is first photocatalytically oxidized to polar sulfoxides and sulfones over TiO2-CeO2, which are then selectively adsorbed on the bifucntional TiO2-CeO2 material due to their much higher polarities than the original oranosulfur compounds and other organic compounds in the diesel fuel. The TiO2-CeO2 material with a Ti/Ce molar ratio of 9:1 and calcined at 500℃ exhibits the highest synergistic photocatalysis-adsorption desulfurization performance; over it the sulfur removal rate reaches 99.6% for a model fuel after reaction for 5 h under UV irradiation. The low desulfurization selctivity because of the strongly competitive adsorption of aromatics in the diesel fule could be greatly improved by employing the synergistic photocatalysis-adsorption desulfurization process; the sulfur removal rate is still higher than 96.6% for the model fuel containing 25% toluene after reaction for 7 h under UV irradiation. The desulfurization performance of TiO2-CeO2 for different organosulfur compounds in the diesel fuel follows the order of 4, 6-DMDBT > DBT > BT. Moreover, TiO2-CeO2 can be well regenrated by washing with acetonitrile followed by heat treatment in air; it still gives a high synergistic photocatalysis-adsorption desulfurization performance even after four regeneration cycles.
2017, 45(5): 616-623
Abstract:
Mo-Ni/Al2O3 catalysts were prepared by different impregnation sequences of Mo and Ni; the effect of impregnation sequence on the performance of Mo-Ni/Al2O3 catalysts in thioetherification was investigated. The results showed that the activity of the catalyst obtained by first impregnating Mo and then Ni (SI-mn) is close to that prepared by co-impregnation of Mo and Ni (MN); both are much more active than the catalyst obtained by first impregnating Ni and then Mo (SI-nm). For the SI-mn catalyst, Mo loaded on Al2O3 at the first stage can weaken the interaction between Ni and supporter, leading to a strong electronic effect between Ni and Mo, which can promote the formation of active phase in the presulfidation process and then enhance the catalytic performance of Mo-Ni/Al2O3 in thioetherification and selective hydrogenation of diene. Similar phenomena are observed for the MN catalyst obtained by co-impregnation, which also exhibits high activity in thioetherification.
Mo-Ni/Al2O3 catalysts were prepared by different impregnation sequences of Mo and Ni; the effect of impregnation sequence on the performance of Mo-Ni/Al2O3 catalysts in thioetherification was investigated. The results showed that the activity of the catalyst obtained by first impregnating Mo and then Ni (SI-mn) is close to that prepared by co-impregnation of Mo and Ni (MN); both are much more active than the catalyst obtained by first impregnating Ni and then Mo (SI-nm). For the SI-mn catalyst, Mo loaded on Al2O3 at the first stage can weaken the interaction between Ni and supporter, leading to a strong electronic effect between Ni and Mo, which can promote the formation of active phase in the presulfidation process and then enhance the catalytic performance of Mo-Ni/Al2O3 in thioetherification and selective hydrogenation of diene. Similar phenomena are observed for the MN catalyst obtained by co-impregnation, which also exhibits high activity in thioetherification.
Catalytic performance of MnOx/TiO2 prepared with different precursors in the oxidation of NO with O3
2017, 45(5): 624-632
Abstract:
MnAc/TiO2, MnCl/TiO2 and MnN/TiO2 were prepared by impregnation method using manganese acetate (MnAc), manganese chloride (MnCl2) and manganese nitrate (Mn (NO3)2) as precursors, respectively. These catalysts were characterized by SEM, N2 physisorption, H2-TPR, O2-TPD, XRD and XPS; their catalytic performance in the oxidation of NO with ozone (O3) was investigated in a fixed bed reactor. The results illustrate that the MnAc/TiO2 catalyst with manganese acetate as the precursor exhibits the highest activity among three catalysts, which is ascribed to its highly dispersible particles, large surface area and high content of surface Mn3+.
MnAc/TiO2, MnCl/TiO2 and MnN/TiO2 were prepared by impregnation method using manganese acetate (MnAc), manganese chloride (MnCl2) and manganese nitrate (Mn (NO3)2) as precursors, respectively. These catalysts were characterized by SEM, N2 physisorption, H2-TPR, O2-TPD, XRD and XPS; their catalytic performance in the oxidation of NO with ozone (O3) was investigated in a fixed bed reactor. The results illustrate that the MnAc/TiO2 catalyst with manganese acetate as the precursor exhibits the highest activity among three catalysts, which is ascribed to its highly dispersible particles, large surface area and high content of surface Mn3+.
2017, 45(5): 633-640
Abstract:
Mg/Ce-SBA-15 mesoporous molecular sieves were synthesized by using Ce-SBA-15 as support and magnesium nitrate as precursor through impregnation method. The samples were characterized by XRD, N2 adsorption-desorption, BET, SEM, NH3-TPD, Py-FTIR and TG-DTA techniques. The results indicate that the original crystal structures of SBA-15 remain unchanged after modification with Mg, but the number of weak acids were increased especially L acids. The performances of catalysts in phenol alkylation with methanol were studied in a fixed bed reactor. The results showed that the catalyst showed the highest catalytic activity under the conditions of Mg content=7%, calcination temperature=550℃ and calcination time=4.5 h.At 460℃, n(phenol):n(methanol)=1:4, WHSV=3.0 h-1 and atmospheric pressure, the conversion of phenol was 80.1% and the selectivity to o-cresol was 86.4%.
Mg/Ce-SBA-15 mesoporous molecular sieves were synthesized by using Ce-SBA-15 as support and magnesium nitrate as precursor through impregnation method. The samples were characterized by XRD, N2 adsorption-desorption, BET, SEM, NH3-TPD, Py-FTIR and TG-DTA techniques. The results indicate that the original crystal structures of SBA-15 remain unchanged after modification with Mg, but the number of weak acids were increased especially L acids. The performances of catalysts in phenol alkylation with methanol were studied in a fixed bed reactor. The results showed that the catalyst showed the highest catalytic activity under the conditions of Mg content=7%, calcination temperature=550℃ and calcination time=4.5 h.At 460℃, n(phenol):n(methanol)=1:4, WHSV=3.0 h-1 and atmospheric pressure, the conversion of phenol was 80.1% and the selectivity to o-cresol was 86.4%.
2017, 45(5): 537-546
Abstract:
The laminar MgO with high specific area and the organometallic precursor Cu (acac)2 were used for the successful synthesis of Cu/MgO catalysts by metal-organic chemical vapor deposition (MOCVD) method. The copper supported on MgO catalysts were characterized by means of X-ray diffraction, Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and N2-physisorption. Characterization results indicated that the organic precursor was successfully deposited onto MgO and the crystal structure of MgO remained intact after deposition. The hydrogenation of γ-valerolactone (γ-GVL) was employed to evaluate the catalytic performance of the Cu/MgO catalysts. It was found that the 18% Cu/MgO catalyst exhibited excellent catalytic activity (90.5%) and selectivity (94.4%) for 1, 4-PDO at 473 K and 10 MPa, and the catalytic activity of Cu/MgO did not diminish significantly after cycling for three times.
The laminar MgO with high specific area and the organometallic precursor Cu (acac)2 were used for the successful synthesis of Cu/MgO catalysts by metal-organic chemical vapor deposition (MOCVD) method. The copper supported on MgO catalysts were characterized by means of X-ray diffraction, Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and N2-physisorption. Characterization results indicated that the organic precursor was successfully deposited onto MgO and the crystal structure of MgO remained intact after deposition. The hydrogenation of γ-valerolactone (γ-GVL) was employed to evaluate the catalytic performance of the Cu/MgO catalysts. It was found that the 18% Cu/MgO catalyst exhibited excellent catalytic activity (90.5%) and selectivity (94.4%) for 1, 4-PDO at 473 K and 10 MPa, and the catalytic activity of Cu/MgO did not diminish significantly after cycling for three times.
2017, 45(5): 547-555
Abstract:
The effect of various promoting additives (Mn, Zn, Co) on the performance of CuFeZr catalyst in the synthesis of higher alcohol from syngas was investigated. The results of nitrogen physisorption, XRD and H2-TPR characterization show that these additives can reduce the particle size and enhance the surface basicity and the adsorption capacity towards CO. Especially, the doping of Zn in the CuFeZr catalyst can effectively enhance the interaction between Cu and Fe, strengthen the surface basicity, and improve the reducibility and CO adsorption ability. For the synthesis of higher alcohol from syngas over the CuFeZr catalyst, the catalytic evaluation results in a fixed bed reactor illustrate that the activity and selectivity to alcohols are greatly enhanced by the addition of Zn promoter; the space time yield (STY) of ROH is increased from 0.026 to 0.071 g/(gcat·h). Meanwhile, it was found that CO2 in the feed can improve the CO conversion as well as the STY to alcohols and hydrocarbons, but suppress the chain growth and decrease the ratio of olefin to paraffin; proper amount of CO2 (2.5%) is beneficial to the formation of alcohols and hydrocarbons of short chains.
The effect of various promoting additives (Mn, Zn, Co) on the performance of CuFeZr catalyst in the synthesis of higher alcohol from syngas was investigated. The results of nitrogen physisorption, XRD and H2-TPR characterization show that these additives can reduce the particle size and enhance the surface basicity and the adsorption capacity towards CO. Especially, the doping of Zn in the CuFeZr catalyst can effectively enhance the interaction between Cu and Fe, strengthen the surface basicity, and improve the reducibility and CO adsorption ability. For the synthesis of higher alcohol from syngas over the CuFeZr catalyst, the catalytic evaluation results in a fixed bed reactor illustrate that the activity and selectivity to alcohols are greatly enhanced by the addition of Zn promoter; the space time yield (STY) of ROH is increased from 0.026 to 0.071 g/(gcat·h). Meanwhile, it was found that CO2 in the feed can improve the CO conversion as well as the STY to alcohols and hydrocarbons, but suppress the chain growth and decrease the ratio of olefin to paraffin; proper amount of CO2 (2.5%) is beneficial to the formation of alcohols and hydrocarbons of short chains.
2017, 45(5): 581-588
Abstract:
A series of as-synthesized HZSM-5 zeolites with different Si/Al ratios (25, 90, 120, 240 and 400) were post-treated by ultrasonication for an optimum time of 60 min. The morphology, acidity and textural properties of HZSM-5 were characterized with XRD, SEM, N2 adsorption and NH3-TPD techniques. The catalytic performance was evaluated by dehydration of methanol to dimethyl ether (DME), which is a promising gaseous automotive fuel in future. It was found that the Si/Al ratio of HZSM-5 had considerable impacts on its catalytic performance for dehydration of methanol to DME. Its activity increased with decreasing Si/Al ratio from 400 to 25. Ultrasonication of HZSM-5 could significantly improve its catalytic performance.
A series of as-synthesized HZSM-5 zeolites with different Si/Al ratios (25, 90, 120, 240 and 400) were post-treated by ultrasonication for an optimum time of 60 min. The morphology, acidity and textural properties of HZSM-5 were characterized with XRD, SEM, N2 adsorption and NH3-TPD techniques. The catalytic performance was evaluated by dehydration of methanol to dimethyl ether (DME), which is a promising gaseous automotive fuel in future. It was found that the Si/Al ratio of HZSM-5 had considerable impacts on its catalytic performance for dehydration of methanol to DME. Its activity increased with decreasing Si/Al ratio from 400 to 25. Ultrasonication of HZSM-5 could significantly improve its catalytic performance.
2017, 45(5): 596-607
Abstract:
The ternary catalyst Pt75Ru5Ni20 was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt75Ru5Ni20/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC.
The ternary catalyst Pt75Ru5Ni20 was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt75Ru5Ni20/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC.
