The conversion of CO_(2) into specific aromatics by modulating the morphology of zeolites is a promising strategy.HZSM-5 zeolite with hollow tubular morphology is reported.The morphology of zeolite was precisely contr...The conversion of CO_(2) into specific aromatics by modulating the morphology of zeolites is a promising strategy.HZSM-5 zeolite with hollow tubular morphology is reported.The morphology of zeolite was precisely controlled,and the acid sites on its outer surface were passivated by steam-assisted crystallization method,so that the zeolite exhibits higher aromatic selectivity than sheet HZSM-5 zeolite and greater p-xylene selectivity than chain HZSM-5 zeolite.The tandem catalyst was formed by combining hollow tubular HZSM-5 zeolites with ZnZrO_(x)metal oxides.The para-selectivity of p-xylene reached 76.2%at reaction temperature of 320℃,pressure of 3.0 MPa,and a flow rate of 2400 mL g^(-1)h^(-1)with an H_(2)/CO_(2) molar ratio of 3/1.Further research indicates that the high selectivity of p-xylene is due to the pore structure of hollow tubular HZSM-5 zeolite,which is conducive to the formation of p-xylene.Moreover,the passivation of the acid site located on the outer surface of zeolite effectively prevents the isomerization of p-xylene.The reaction mechanism of CO_(2) hydrogenation over the tandem catalyst was investigated using in-situ diffuse reflectance Fourier transform infrared spectroscopy and density functional theory.The results showed that the CO_(2) to p-xylene followed a methanol-mediated route over ZnZrO_(x)/hollow tubular HZSM-5 tandem catalysts.In addition,the catalyst showed no significant deactivation in the 100 h stability test.This present study provides an effective strategy for the design of catalysts aimed at selectively preparing aromatics through CO_(2)hydrogenation.展开更多
A mild and efficient synthesis of spiroquinoxalinones via tandem condensation of chlorooxoindoline 1 with benzene-1,2-diamines 2 is described.And a plausible mechanism for the reaction is proposed.
A centrifugal compressor usually operates with low isentropic efficiency and a terrible stable operating range, resulting from the complex impeller flow structure companied with the intense interaction among the impel...A centrifugal compressor usually operates with low isentropic efficiency and a terrible stable operating range, resulting from the complex impeller flow structure companied with the intense interaction among the impeller and the diffuser downstream. In many studies, the potential of centrifugal compressor tandem-impeller configurations for improving the compressor has been demonstrated. Whereas, compared with the convincing results on the tandem-designed axial compressors, the results on tandem impellers are limited and contradictory. Very little insight has been provided into the flow mechanisms inside tandem impellers, which is considered to be the primary reason for the confusion in tandem impeller design and application. Tandem impellers are expected to exhibit a totally different behavior due to the intense aerodynamic interaction between the inducer and the exducer, which substantially contributes to the flow structure and the compressor performance change. In the present study, a numerical study of a highly-loaded centrifugal compressor with various tandem designs was conducted to explore the inducer/exducer matching characteristics and the underlying flow mechanism inside tandem impellers. Two tandem impeller design parameters, namely, the inducer/exducer clocking fraction and the axial gap(overlap), were considered in the tandem impeller design process. The tandem impeller was also compared to the existing conventional impeller which the tandem impeller was redesigned for. The results demonstrated that the tandem-designed impeller can improve the centrifugal compressor stage performance and intense inducer/exducer interaction can be observed with changes in the clocking fraction and the axial gap(overlap). The tandem impeller performance is sensitive to changes in axial gap(overlap) when the suction side of the exducer blade is circumferentially close to the inducer blade. The fundamental reason for the performance variation in the inducer and the exducer lies in the inducer pressure change in the blade 展开更多
Based on the physiological structure of the intestine, a Caco-2/EAhy926 tandem compound model was constructed in order to simulate the intestinal-vascular barrier. This model was applied in the study of transcytosis o...Based on the physiological structure of the intestine, a Caco-2/EAhy926 tandem compound model was constructed in order to simulate the intestinal-vascular barrier. This model was applied in the study of transcytosis of nanoparticles, and it was compared with the traditional intestinal cell model in the whole study. Briefly, Fe3O4 nanoparticles with a size about 30 nm were used as model nanoparticles, which remained steady during transcytosis. The nanoparticles hardly had cytotoxicity to Caco-2 cells and EAhy926 cells within the incubation concentrations. The cell tandem model was established by connecting upper Caco-2 monolayer and lower EAhy926 monolayer. Based on the FD4 permeability or TEER, all cell models remained integrity within certain period of culture time. The expression of Claudin-4 or VE Cadherin demonstrated the presence of tight junctions. The intact morphology of microfilament F-actin indicated the favorable intracellular connection. It was found that the two-layer cell tandem model created a bigger barrier for the transcytosis of FD4 than Caco-2 and EAhy926 monolayer models, and the translocation of Fe3O4 nanoparticles showed a similar pattern. Interestingly, we found that the main barrier of tandem model for nanoparticles was caused by the upper Caco-2 cell monolayer, while the lower layer of EAhy926 monolayer remained high permeability. Generally, the cell tandem compound model established here enabled us to evaluate the impact of both intestinal epithelial and endothelial layer on transcytosis, and it might provide a novel approach to study bio-nano interaction in the intestine.展开更多
基金financially supported by the National Natural Science Foundation of China(22268039)the Natural Science Foundation for Distinguished Young Scholars of Gansu Province(23JRRA682)。
文摘The conversion of CO_(2) into specific aromatics by modulating the morphology of zeolites is a promising strategy.HZSM-5 zeolite with hollow tubular morphology is reported.The morphology of zeolite was precisely controlled,and the acid sites on its outer surface were passivated by steam-assisted crystallization method,so that the zeolite exhibits higher aromatic selectivity than sheet HZSM-5 zeolite and greater p-xylene selectivity than chain HZSM-5 zeolite.The tandem catalyst was formed by combining hollow tubular HZSM-5 zeolites with ZnZrO_(x)metal oxides.The para-selectivity of p-xylene reached 76.2%at reaction temperature of 320℃,pressure of 3.0 MPa,and a flow rate of 2400 mL g^(-1)h^(-1)with an H_(2)/CO_(2) molar ratio of 3/1.Further research indicates that the high selectivity of p-xylene is due to the pore structure of hollow tubular HZSM-5 zeolite,which is conducive to the formation of p-xylene.Moreover,the passivation of the acid site located on the outer surface of zeolite effectively prevents the isomerization of p-xylene.The reaction mechanism of CO_(2) hydrogenation over the tandem catalyst was investigated using in-situ diffuse reflectance Fourier transform infrared spectroscopy and density functional theory.The results showed that the CO_(2) to p-xylene followed a methanol-mediated route over ZnZrO_(x)/hollow tubular HZSM-5 tandem catalysts.In addition,the catalyst showed no significant deactivation in the 100 h stability test.This present study provides an effective strategy for the design of catalysts aimed at selectively preparing aromatics through CO_(2)hydrogenation.
文摘A mild and efficient synthesis of spiroquinoxalinones via tandem condensation of chlorooxoindoline 1 with benzene-1,2-diamines 2 is described.And a plausible mechanism for the reaction is proposed.
基金financial support from the National Natural Science Foundation of China(Project No.51876022,No.51836008)is greatly appreciated。
文摘A centrifugal compressor usually operates with low isentropic efficiency and a terrible stable operating range, resulting from the complex impeller flow structure companied with the intense interaction among the impeller and the diffuser downstream. In many studies, the potential of centrifugal compressor tandem-impeller configurations for improving the compressor has been demonstrated. Whereas, compared with the convincing results on the tandem-designed axial compressors, the results on tandem impellers are limited and contradictory. Very little insight has been provided into the flow mechanisms inside tandem impellers, which is considered to be the primary reason for the confusion in tandem impeller design and application. Tandem impellers are expected to exhibit a totally different behavior due to the intense aerodynamic interaction between the inducer and the exducer, which substantially contributes to the flow structure and the compressor performance change. In the present study, a numerical study of a highly-loaded centrifugal compressor with various tandem designs was conducted to explore the inducer/exducer matching characteristics and the underlying flow mechanism inside tandem impellers. Two tandem impeller design parameters, namely, the inducer/exducer clocking fraction and the axial gap(overlap), were considered in the tandem impeller design process. The tandem impeller was also compared to the existing conventional impeller which the tandem impeller was redesigned for. The results demonstrated that the tandem-designed impeller can improve the centrifugal compressor stage performance and intense inducer/exducer interaction can be observed with changes in the clocking fraction and the axial gap(overlap). The tandem impeller performance is sensitive to changes in axial gap(overlap) when the suction side of the exducer blade is circumferentially close to the inducer blade. The fundamental reason for the performance variation in the inducer and the exducer lies in the inducer pressure change in the blade
基金The National Basic Research Program of China(973 program,Grant No.2015CB932100)the National Basic Research Program of China(Grant No.2015CB932100)+1 种基金National Natural Science Foundation of China(Grant No.81690264)the Innovation Team of the Ministry of Education(Grant No.BMU20110263)
文摘Based on the physiological structure of the intestine, a Caco-2/EAhy926 tandem compound model was constructed in order to simulate the intestinal-vascular barrier. This model was applied in the study of transcytosis of nanoparticles, and it was compared with the traditional intestinal cell model in the whole study. Briefly, Fe3O4 nanoparticles with a size about 30 nm were used as model nanoparticles, which remained steady during transcytosis. The nanoparticles hardly had cytotoxicity to Caco-2 cells and EAhy926 cells within the incubation concentrations. The cell tandem model was established by connecting upper Caco-2 monolayer and lower EAhy926 monolayer. Based on the FD4 permeability or TEER, all cell models remained integrity within certain period of culture time. The expression of Claudin-4 or VE Cadherin demonstrated the presence of tight junctions. The intact morphology of microfilament F-actin indicated the favorable intracellular connection. It was found that the two-layer cell tandem model created a bigger barrier for the transcytosis of FD4 than Caco-2 and EAhy926 monolayer models, and the translocation of Fe3O4 nanoparticles showed a similar pattern. Interestingly, we found that the main barrier of tandem model for nanoparticles was caused by the upper Caco-2 cell monolayer, while the lower layer of EAhy926 monolayer remained high permeability. Generally, the cell tandem compound model established here enabled us to evaluate the impact of both intestinal epithelial and endothelial layer on transcytosis, and it might provide a novel approach to study bio-nano interaction in the intestine.
