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
Y-β zeolite composites were hydrotherrnally synthesized by using high silica Y zeolite as the precursor and characterized by XRD, N2 adsorption, SEM and IR spectra of pyridine. The result showed that the N2 adsorptio...Y-β zeolite composites were hydrotherrnally synthesized by using high silica Y zeolite as the precursor and characterized by XRD, N2 adsorption, SEM and IR spectra of pyridine. The result showed that the N2 adsorption-desorption isotherm of the zeolite composites had a distinct hysteresis loop, and the SEM result showed that the zeolite composites had a different morphology from Y, β and the corresponding physical zeolite mixture. The acid catalytic performance of the zeolite composite catalysts was investigated in the hydrocracking and hydroisomerization of n-octane, and the results showed that the composite materials exhibited an excellent hydrocracking activity and good hydroisomerization performance. The yield of i-C4 over the zeolite composite catalyst was 4.45% higher than that on the corresponding zeolite mixture in the n-octane hydrocracking process at 553 K. The isomerization ability of n-octane over the composite catalyst was 3.6 fold that of the corresponding mixture at 503 K.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
The objective of this study is to explore the optimum composition of Y and ZSM-5 zeolites to develop novel catalysts for obtaining lower gasoline olefins content and higher propylene yield. Five composite zeolite cata...The objective of this study is to explore the optimum composition of Y and ZSM-5 zeolites to develop novel catalysts for obtaining lower gasoline olefins content and higher propylene yield. Five composite zeolite catalysts with varying Y zeolite/ZSM-5 zeolite ratios have been prepared in this work to investigate the synergy between the Y zeolite and ZSM-5 zeolite on the selectivity to protolytic cracking, β-scission, oligomerization, and hydrogen transfer reactions using a FCC naphtha feedstock at 480 ℃ in a confined fluidized bed reactor. Experimental results showed that the composite catalyst with a Y zeolite/ZSM-5 zeolite ratio of 1:4 had the highest protolytic cracking and β-scission ability, which was even higher than that of pure ZSM-5 catalyst. On the other hand, the catalyst with a Y zeolite/ZSM-5 zeolite ratio of 3:2 exhibited the strongest hydrogen transfer functionality while the pure Y zeolite based catalyst had the highest oligomerization ability. For all the catalysts tested, increasing conversion enhanced the selectivity to protolytic cracking and hydrogen transfer reactions but reduced the selectivity to β-scission reaction. However, no clear trend was identified for the selectivity to oligomerization when an increased conversion was experienced.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
Red soil,the most critical soil resource in tropical/subtropical regions worldwide,faces tremendous threats,including nutrient deficiency,acidification,and heavy metal contamination.There is a great demand for multifu...Red soil,the most critical soil resource in tropical/subtropical regions worldwide,faces tremendous threats,including nutrient deficiency,acidification,and heavy metal contamination.There is a great demand for multifunctional eco-materials capable of modifying this situation.Herein,we used widely distributed soil and biomass to develop a zeolite/biochar composite for synergistic red soil remediation and amendment.With the composite material,the Pb^(2+) and Cd^(2+) remediation efficiencies reached 92.8%and 92.9%,respectively,in stems under optimal conditions.Moreover,the acidity and nutrient deficiency conditions of red soil significantly improved.The atomic-scale interaction mechanism during the remediation and amendment process was elucidated with complementary characterization methods,which revealed that in the zeolite/biochar composite material,zeolite contributes to longterm heavy metal remediation effects.Simultaneously,biochar is responsible for soil quality amendment and short-term heavy metal remediation.Furthermore,for the first time,single-atom heavy metal ions were observed on biochar during the remediation process,indicating the broad distribution of single atoms in the natural environment.展开更多
In order to further improve the catalytic performance of zeolite catalyst for methanol to aromatics(MTA)technology, the double-tier SAPO-34/ZSM-5/quartz composite zeolite films were successfully synthesized via hydrot...In order to further improve the catalytic performance of zeolite catalyst for methanol to aromatics(MTA)technology, the double-tier SAPO-34/ZSM-5/quartz composite zeolite films were successfully synthesized via hydrothermal crystallization. The Si/Al ratio of SAPO-34 film was used as the only variable to study this material. The composite zeolite material with 0.6Si/Al ratio of SAPO-34 has the largest mesoporous specific surface area and the most suitable acid distribution. The catalytic performance for the MTA process showed that 0.6-SAPO-34/ZSM-5/quartz film has as high as 50.3% benzene-toluenexylene selectivity and 670 min lifetime. The MTA reaction is carried out through the path we designed to effectively avoid the hydrocarbon pool circulation of ZSM-5 zeolite, so as to improve the aromatics selectivity and inhibit the occurrence of deep side reactions to a great extent. The coke deposition behavior was monitored by thermogravimetric analysis and gas chromatograph/mass spectrometer, it is found that with the increase of Si/Al ratio, the active intermediates changed from low-substituted methylbenzene to high-substituted methylbenzene, which led to the rapid deactivation of the catalyst. This work provides a possibility to employ the synergy effect of composite zeolite film synthesizing anti-carbon deposition catalyst in MTA reaction.展开更多
A bifunctional catalyst Pt/HY-β was prepared from a bimicroporous composite zeolite Y-β. Characterization results showed that the specific surface area, pore volume, and acid amount of the catalyst Pt/HY-β all decr...A bifunctional catalyst Pt/HY-β was prepared from a bimicroporous composite zeolite Y-β. Characterization results showed that the specific surface area, pore volume, and acid amount of the catalyst Pt/HY-β all decreased compared to the original zeolite. The catalytic performance of this catalyst in n-octane hydroisomerization was investigated in a fixed bed stainless steel tubular reactor. The results showed that at a hydrogen/n-octane volume ratio of 1000, pressure of 0.6 MPa, temperature of 230 ℃ and LHSV of 3 h^-1, the conversion of n-octane, yield of liquid, hydrocracking rate and yield of iso-octane were 52.32%, 88.66%, 12.60%, 39.51%, respectively.展开更多
A zeolite composite composed of ZSM-5 and β-zeolites has been synthesized by a procedure of the nucleation and crystallization of ZSM-5 zeolite in the hollow β-zeolite. The property of β-zeolite crystals with alumi...A zeolite composite composed of ZSM-5 and β-zeolites has been synthesized by a procedure of the nucleation and crystallization of ZSM-5 zeolite in the hollow β-zeolite. The property of β-zeolite crystals with aluminum-poor interior and aluminum-rich outer rim results in silicon extraction favorably in the aluminum-poor bulk rather than the aluminum-rich external surface. Subsequently, alkaline treatment offl-zeolite crystals during the second-step synthesis leads to a preferential dissolution of the aluminum-poor center and the formation of hollow β-zeolite crystals. ZSM-5 zeolite crystals are therefore embedded and grown within the hollow β-zeolite. The catalytic activities of Co-Hβ, Co-HZSM-5 and Co-HZSM-5/BEA are investigated during the reaction of methane catalytic reduction NO in the presence of O2.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Y-β zeolite composites were hydrotherrnally synthesized by using high silica Y zeolite as the precursor and characterized by XRD, N2 adsorption, SEM and IR spectra of pyridine. The result showed that the N2 adsorption-desorption isotherm of the zeolite composites had a distinct hysteresis loop, and the SEM result showed that the zeolite composites had a different morphology from Y, β and the corresponding physical zeolite mixture. The acid catalytic performance of the zeolite composite catalysts was investigated in the hydrocracking and hydroisomerization of n-octane, and the results showed that the composite materials exhibited an excellent hydrocracking activity and good hydroisomerization performance. The yield of i-C4 over the zeolite composite catalyst was 4.45% higher than that on the corresponding zeolite mixture in the n-octane hydrocracking process at 553 K. The isomerization ability of n-octane over the composite catalyst was 3.6 fold that of the corresponding mixture at 503 K.
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financial support from the National Key Technology R&D Program (2012BAE05B01) of China
文摘The objective of this study is to explore the optimum composition of Y and ZSM-5 zeolites to develop novel catalysts for obtaining lower gasoline olefins content and higher propylene yield. Five composite zeolite catalysts with varying Y zeolite/ZSM-5 zeolite ratios have been prepared in this work to investigate the synergy between the Y zeolite and ZSM-5 zeolite on the selectivity to protolytic cracking, β-scission, oligomerization, and hydrogen transfer reactions using a FCC naphtha feedstock at 480 ℃ in a confined fluidized bed reactor. Experimental results showed that the composite catalyst with a Y zeolite/ZSM-5 zeolite ratio of 1:4 had the highest protolytic cracking and β-scission ability, which was even higher than that of pure ZSM-5 catalyst. On the other hand, the catalyst with a Y zeolite/ZSM-5 zeolite ratio of 3:2 exhibited the strongest hydrogen transfer functionality while the pure Y zeolite based catalyst had the highest oligomerization ability. For all the catalysts tested, increasing conversion enhanced the selectivity to protolytic cracking and hydrogen transfer reactions but reduced the selectivity to β-scission reaction. However, no clear trend was identified for the selectivity to oligomerization when an increased conversion was experienced.
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supported by the National Key Research and Development Program of China(No.2021YFA1202500)the Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control(No.2023B1212060002)+1 种基金the Stable Support Plan Program of Shenzhen Natural Science Foundation(No.20231122110855002)the High level of special funds(No.G03050K001)from SUSTech and a Special Fund for the Science and Technology Innovation Strategy of Guangdong Province(No.PDJH2021C0033).
文摘Red soil,the most critical soil resource in tropical/subtropical regions worldwide,faces tremendous threats,including nutrient deficiency,acidification,and heavy metal contamination.There is a great demand for multifunctional eco-materials capable of modifying this situation.Herein,we used widely distributed soil and biomass to develop a zeolite/biochar composite for synergistic red soil remediation and amendment.With the composite material,the Pb^(2+) and Cd^(2+) remediation efficiencies reached 92.8%and 92.9%,respectively,in stems under optimal conditions.Moreover,the acidity and nutrient deficiency conditions of red soil significantly improved.The atomic-scale interaction mechanism during the remediation and amendment process was elucidated with complementary characterization methods,which revealed that in the zeolite/biochar composite material,zeolite contributes to longterm heavy metal remediation effects.Simultaneously,biochar is responsible for soil quality amendment and short-term heavy metal remediation.Furthermore,for the first time,single-atom heavy metal ions were observed on biochar during the remediation process,indicating the broad distribution of single atoms in the natural environment.
基金supported by the National Natural Science Foundation of China (51974312, 51974308)the National Key Research & Development Program of China (2019YFE0100100)。
文摘In order to further improve the catalytic performance of zeolite catalyst for methanol to aromatics(MTA)technology, the double-tier SAPO-34/ZSM-5/quartz composite zeolite films were successfully synthesized via hydrothermal crystallization. The Si/Al ratio of SAPO-34 film was used as the only variable to study this material. The composite zeolite material with 0.6Si/Al ratio of SAPO-34 has the largest mesoporous specific surface area and the most suitable acid distribution. The catalytic performance for the MTA process showed that 0.6-SAPO-34/ZSM-5/quartz film has as high as 50.3% benzene-toluenexylene selectivity and 670 min lifetime. The MTA reaction is carried out through the path we designed to effectively avoid the hydrocarbon pool circulation of ZSM-5 zeolite, so as to improve the aromatics selectivity and inhibit the occurrence of deep side reactions to a great extent. The coke deposition behavior was monitored by thermogravimetric analysis and gas chromatograph/mass spectrometer, it is found that with the increase of Si/Al ratio, the active intermediates changed from low-substituted methylbenzene to high-substituted methylbenzene, which led to the rapid deactivation of the catalyst. This work provides a possibility to employ the synergy effect of composite zeolite film synthesizing anti-carbon deposition catalyst in MTA reaction.
基金sponsored by China Petroleumand Chemical Corporation(No.:090701)
文摘A bifunctional catalyst Pt/HY-β was prepared from a bimicroporous composite zeolite Y-β. Characterization results showed that the specific surface area, pore volume, and acid amount of the catalyst Pt/HY-β all decreased compared to the original zeolite. The catalytic performance of this catalyst in n-octane hydroisomerization was investigated in a fixed bed stainless steel tubular reactor. The results showed that at a hydrogen/n-octane volume ratio of 1000, pressure of 0.6 MPa, temperature of 230 ℃ and LHSV of 3 h^-1, the conversion of n-octane, yield of liquid, hydrocracking rate and yield of iso-octane were 52.32%, 88.66%, 12.60%, 39.51%, respectively.
基金supported by the"973"project(No.2005CB221204)SinoPEC(No.107009)
文摘A zeolite composite composed of ZSM-5 and β-zeolites has been synthesized by a procedure of the nucleation and crystallization of ZSM-5 zeolite in the hollow β-zeolite. The property of β-zeolite crystals with aluminum-poor interior and aluminum-rich outer rim results in silicon extraction favorably in the aluminum-poor bulk rather than the aluminum-rich external surface. Subsequently, alkaline treatment offl-zeolite crystals during the second-step synthesis leads to a preferential dissolution of the aluminum-poor center and the formation of hollow β-zeolite crystals. ZSM-5 zeolite crystals are therefore embedded and grown within the hollow β-zeolite. The catalytic activities of Co-Hβ, Co-HZSM-5 and Co-HZSM-5/BEA are investigated during the reaction of methane catalytic reduction NO in the presence of O2.
