For investigating the effect of dealumination on the pore structure and catalytic performance, ZSM-5/Y composite zeolites synthesized in situ from NaY gel were dealuminated by steaming at different temperatures. XRD ...For investigating the effect of dealumination on the pore structure and catalytic performance, ZSM-5/Y composite zeolites synthesized in situ from NaY gel were dealuminated by steaming at different temperatures. XRD (X-ray diffraction) characterization indicates that the relative crystallinity of the composite zeolites decreases with the increase in Si/Al ratio after steaming. N2 adsorption-desorption suggests that more mesopores are formed while the BET (Brunauer, Emmett and Teller) specific surface area and the micropore specific surface area decrease as the temperature of steaming rises. Daqing heavy oil was used as feedstock to test the catalytic cracking activity of ZSM-5/Y composite zeolites. The experimental results of the catalytic cracking performance reveal that the distribution of products differs due to the different conditions of hydrothermal treatment. Further hydrothermal treatment leads to an increase in the yield of light oil, and a decrease in the yield of gas products and coke.展开更多
The composite ZSM—5 zeolite/vermiculite catalyst,in which tiny ZSM—5 zeolite parti- cles embedded in the vermiculite substrate,has been synthesized by hydrothermal method with vermiculite as silicon source.The catal...The composite ZSM—5 zeolite/vermiculite catalyst,in which tiny ZSM—5 zeolite parti- cles embedded in the vermiculite substrate,has been synthesized by hydrothermal method with vermiculite as silicon source.The catalytic behavior of resulting catalyst for xylene isomerization,propylene aromatization and toluene disproportionation is better than that of HZSM—5 zeolite.展开更多
A ZSM-5/MAPO composite catalyst was prepared by adding ZSM-5 zeolite powder to a conventional molecular sieve synthesis system, followed by modification with NH_4H_2PO_4. The samples were characterized by XRD, SEM, IR...A ZSM-5/MAPO composite catalyst was prepared by adding ZSM-5 zeolite powder to a conventional molecular sieve synthesis system, followed by modification with NH_4H_2PO_4. The samples were characterized by XRD, SEM, IR, NH_3-TPD, and BET analyses. The catalytic property of the samples toward the methanol-to-olefin(MTO) reaction was evaluated in a connected in series two-stage unit equipped with a continuous flow(once-through) fixed-bed tubular reactor similar to an industrial reactor. The first reactor mainly converted methanol into dimethyl ether and water, followed by being subject to continuous reaction in the second reactor, in which DME was converted to hydrocarbons. The composites exhibited the typical framework topology of MFI, AEI and AFI, which represented the ZSM-5 zeolite, the molecular sieves AlPO-18 or SAPO-18, AlPO-5 or SAPO-5, respectively. The composites showed several advantages for optimizing the zeolite acidity, enhancing the mass transfer, and restraining the side reactions. Catalytic reaction results showed that the composites exhibited higher selectivity to light olefins(84.0%) and lower selectivity to C_2―C_4 alkanes and C_5^+ hydrocarbons than pure ZSM-5. Moreover, the composite zeolite loaded with 3% of P demonstrated improved catalytic activity and stability for the conversion of methanol to propylene, because the coking rate was obviously suppressed.展开更多
In this paper,the kaolin/urea intercalation composites prepared by direct intercalation method and the catalysis composites containing ZSM-5 molecular sieve synthesized based on the kaolin/urea intercalation composite...In this paper,the kaolin/urea intercalation composites prepared by direct intercalation method and the catalysis composites containing ZSM-5 molecular sieve synthesized based on the kaolin/urea intercalation composites by an in-situ crystallization technique were investigated.The effects of the intercalation ratios and de-intercalation rate and the amounts of added kaolin/urea intercalation composite on the synthesis of the catalysis composites containing the ZSM-5 molecular sieve were studied.The samples were characterized by X-ray diffraction,FT-IR,TG-DTA,N2 adsorption-desorption,and SEM,respectively.The results showed that the structure of the samples prepared by kaolin/urea intercalation composite was pure ZSM-5 molecular sieve.The crystallinity of ZSM-5 molecular sieve increased at first and then decreased with the increase of intercalation ratio of kaolin/urea intercalation composite.When the intercalation ratio was 62%,the crystallinity of ZSM-5 molecular sieve was lower.When the amount of added kaolin/urea intercalation composite with an intercalation ratio of 22%was 3%,the crystallinity of ZSM-5 zeolite was improved to reach 65%.Compared to the crystallization product formed without adding kaolin/urea intercalation composite,the crystallinity of ZSM-5 molecular sieve has increased by 54.8%.The catalytic composites containing ZSM-5 molecular sieve had better thermal stability with a wide pore structure,featuring a particle diameter of about 2.5μm,a BET specific surface area of 236 m^2/g,and a pore size of 10.6 nm.展开更多
Cu–Mn bimetal catalysts were prepared to remove nitrogen oxides(NOx)from diesel engine exhaust at low temperatures.At a Cu/Mn ratio of 3:2,the NOx conversions at 200°C reached 65%and 90%on Cu–Mn/ZSM‐5 and Cu–...Cu–Mn bimetal catalysts were prepared to remove nitrogen oxides(NOx)from diesel engine exhaust at low temperatures.At a Cu/Mn ratio of 3:2,the NOx conversions at 200°C reached 65%and 90%on Cu–Mn/ZSM‐5 and Cu–Mn/SAPO‐34,respectively.After a hydrothermal treatment and reaction in the presence of C3H6,the activity of Cu–Mn/SAPO‐34 was more stable than that of Cu–Mn/ZSM‐5.No obvious variations in the crystal structure or dealumination were observed,whereas the physical structure was best maintained in Cu–Mn/SAPO‐34.The atomic concentration of Cu on the surface of Cu–Mn/SAPO‐34 was quite stable,and the consumption of octahedrally coordinated Cu2+could be recovered.Conversely,the proportion of octahedrally coordinated Cu2+on the surface of Cu–Mn/ZSM‐5 significantly decreased.Therefore,besides the structure,the redox cycle between Cu+and octahedrally coordinated Cu2+played an important role in the stability of the catalysts.展开更多
文摘For investigating the effect of dealumination on the pore structure and catalytic performance, ZSM-5/Y composite zeolites synthesized in situ from NaY gel were dealuminated by steaming at different temperatures. XRD (X-ray diffraction) characterization indicates that the relative crystallinity of the composite zeolites decreases with the increase in Si/Al ratio after steaming. N2 adsorption-desorption suggests that more mesopores are formed while the BET (Brunauer, Emmett and Teller) specific surface area and the micropore specific surface area decrease as the temperature of steaming rises. Daqing heavy oil was used as feedstock to test the catalytic cracking activity of ZSM-5/Y composite zeolites. The experimental results of the catalytic cracking performance reveal that the distribution of products differs due to the different conditions of hydrothermal treatment. Further hydrothermal treatment leads to an increase in the yield of light oil, and a decrease in the yield of gas products and coke.
文摘The composite ZSM—5 zeolite/vermiculite catalyst,in which tiny ZSM—5 zeolite parti- cles embedded in the vermiculite substrate,has been synthesized by hydrothermal method with vermiculite as silicon source.The catalytic behavior of resulting catalyst for xylene isomerization,propylene aromatization and toluene disproportionation is better than that of HZSM—5 zeolite.
基金financially supported by the National International Cooperation S & T Project of China (No.2015DFA40660)
文摘A ZSM-5/MAPO composite catalyst was prepared by adding ZSM-5 zeolite powder to a conventional molecular sieve synthesis system, followed by modification with NH_4H_2PO_4. The samples were characterized by XRD, SEM, IR, NH_3-TPD, and BET analyses. The catalytic property of the samples toward the methanol-to-olefin(MTO) reaction was evaluated in a connected in series two-stage unit equipped with a continuous flow(once-through) fixed-bed tubular reactor similar to an industrial reactor. The first reactor mainly converted methanol into dimethyl ether and water, followed by being subject to continuous reaction in the second reactor, in which DME was converted to hydrocarbons. The composites exhibited the typical framework topology of MFI, AEI and AFI, which represented the ZSM-5 zeolite, the molecular sieves AlPO-18 or SAPO-18, AlPO-5 or SAPO-5, respectively. The composites showed several advantages for optimizing the zeolite acidity, enhancing the mass transfer, and restraining the side reactions. Catalytic reaction results showed that the composites exhibited higher selectivity to light olefins(84.0%) and lower selectivity to C_2―C_4 alkanes and C_5^+ hydrocarbons than pure ZSM-5. Moreover, the composite zeolite loaded with 3% of P demonstrated improved catalytic activity and stability for the conversion of methanol to propylene, because the coking rate was obviously suppressed.
基金This work was financially supported by the National Natural Science Foundation of China(No.21371055)the Key Project of Scientific Research Project of Hunan Education Department(No.18A313).
文摘In this paper,the kaolin/urea intercalation composites prepared by direct intercalation method and the catalysis composites containing ZSM-5 molecular sieve synthesized based on the kaolin/urea intercalation composites by an in-situ crystallization technique were investigated.The effects of the intercalation ratios and de-intercalation rate and the amounts of added kaolin/urea intercalation composite on the synthesis of the catalysis composites containing the ZSM-5 molecular sieve were studied.The samples were characterized by X-ray diffraction,FT-IR,TG-DTA,N2 adsorption-desorption,and SEM,respectively.The results showed that the structure of the samples prepared by kaolin/urea intercalation composite was pure ZSM-5 molecular sieve.The crystallinity of ZSM-5 molecular sieve increased at first and then decreased with the increase of intercalation ratio of kaolin/urea intercalation composite.When the intercalation ratio was 62%,the crystallinity of ZSM-5 molecular sieve was lower.When the amount of added kaolin/urea intercalation composite with an intercalation ratio of 22%was 3%,the crystallinity of ZSM-5 zeolite was improved to reach 65%.Compared to the crystallization product formed without adding kaolin/urea intercalation composite,the crystallinity of ZSM-5 molecular sieve has increased by 54.8%.The catalytic composites containing ZSM-5 molecular sieve had better thermal stability with a wide pore structure,featuring a particle diameter of about 2.5μm,a BET specific surface area of 236 m^2/g,and a pore size of 10.6 nm.
基金supported by the National Natural Science Foundation of China(51008277)the Natural Science Foundation of Zhejiang Province(LY14E080001)the Key Project of Zhejiang Provincial Science and Technology Program(2012C03003-4)~~
文摘Cu–Mn bimetal catalysts were prepared to remove nitrogen oxides(NOx)from diesel engine exhaust at low temperatures.At a Cu/Mn ratio of 3:2,the NOx conversions at 200°C reached 65%and 90%on Cu–Mn/ZSM‐5 and Cu–Mn/SAPO‐34,respectively.After a hydrothermal treatment and reaction in the presence of C3H6,the activity of Cu–Mn/SAPO‐34 was more stable than that of Cu–Mn/ZSM‐5.No obvious variations in the crystal structure or dealumination were observed,whereas the physical structure was best maintained in Cu–Mn/SAPO‐34.The atomic concentration of Cu on the surface of Cu–Mn/SAPO‐34 was quite stable,and the consumption of octahedrally coordinated Cu2+could be recovered.Conversely,the proportion of octahedrally coordinated Cu2+on the surface of Cu–Mn/ZSM‐5 significantly decreased.Therefore,besides the structure,the redox cycle between Cu+and octahedrally coordinated Cu2+played an important role in the stability of the catalysts.
