A hierarchical beta zeolite synthesized by quasi-solid phase conversion method was characterized by BET, scanning electron microscope （SEM）, transmission electron microscope （TEM）, X-ray diffraction （XRD）, tempe...A hierarchical beta zeolite synthesized by quasi-solid phase conversion method was characterized by BET, scanning electron microscope （SEM）, transmission electron microscope （TEM）, X-ray diffraction （XRD）, temperature-programmed desorption of ammonia （NH3-TPD）, 27A1 and 295i magic angle spinning nuclear magnetic resonance （27A1 and 29Si MAS NMR）, and its catalytic performance was compared with that of conventional microporous beta zeolite for liquid phase transalkylation of multi-secbutylbenzenes （MSBBs） with benzene. The results indicate that the hierarchical beta zeolite consists of nanosized crystals with a meso/ microporous structure and has stronger acid strength than the microporous beta zeolite. The higher conversion oftri-secbutylbenzene （TSBB） and selectivity ofsec-butylbenzene （SBB） are achieved on hierarchical beta zeolite than microporous beta zeolite, while the conversion of di-secbutylbenzene （DSBB） is slightly higher. The improvement of catalytic performance over hierarchical beta zeolite can be ascribed to the presence of mesopores, nanosized crystals and stronger acidity.展开更多
In this study, to investigate whether the variation of wind direction in the upper tropospheric monsoon over the central and eastern tropical Pacific shows similar characteristics to the classical monsoon region, the ...In this study, to investigate whether the variation of wind direction in the upper tropospheric monsoon over the central and eastern tropical Pacific shows similar characteristics to the classical monsoon region, the authors introduced a wind vector angle methodology that describes the size of the angle of the wind direction variation, as well as the directed rotary angle, which includes not only the size of the angle but also how the wind vector rotates. On this basis, the authors utilized and improved the directed rotary angle methodology to investigate the evolution of wind direction in detail, and the study confirmed the presence of the same four rotation features in the upper tropospheric monsoon region. Furthermore, the authors also identified the precise variation of wind direction in pentads with seasonal evolution, and found the onset time of the upper tropospheric monsoon may be earlier than the classical monsoon while the termination time may be later. The results further support and supplement the theory of global monsoons, which unifies the low-level and upper tropospheric monsoon as one monsoon system.展开更多
文摘A hierarchical beta zeolite synthesized by quasi-solid phase conversion method was characterized by BET, scanning electron microscope （SEM）, transmission electron microscope （TEM）, X-ray diffraction （XRD）, temperature-programmed desorption of ammonia （NH3-TPD）, 27A1 and 295i magic angle spinning nuclear magnetic resonance （27A1 and 29Si MAS NMR）, and its catalytic performance was compared with that of conventional microporous beta zeolite for liquid phase transalkylation of multi-secbutylbenzenes （MSBBs） with benzene. The results indicate that the hierarchical beta zeolite consists of nanosized crystals with a meso/ microporous structure and has stronger acid strength than the microporous beta zeolite. The higher conversion oftri-secbutylbenzene （TSBB） and selectivity ofsec-butylbenzene （SBB） are achieved on hierarchical beta zeolite than microporous beta zeolite, while the conversion of di-secbutylbenzene （DSBB） is slightly higher. The improvement of catalytic performance over hierarchical beta zeolite can be ascribed to the presence of mesopores, nanosized crystals and stronger acidity.
基金supported by the National Natural Science Foundation of China Projects(41530424)SOA Program on Global Change and Air-Sea Interactions(GASI-IPOVAI-03)
文摘In this study, to investigate whether the variation of wind direction in the upper tropospheric monsoon over the central and eastern tropical Pacific shows similar characteristics to the classical monsoon region, the authors introduced a wind vector angle methodology that describes the size of the angle of the wind direction variation, as well as the directed rotary angle, which includes not only the size of the angle but also how the wind vector rotates. On this basis, the authors utilized and improved the directed rotary angle methodology to investigate the evolution of wind direction in detail, and the study confirmed the presence of the same four rotation features in the upper tropospheric monsoon region. Furthermore, the authors also identified the precise variation of wind direction in pentads with seasonal evolution, and found the onset time of the upper tropospheric monsoon may be earlier than the classical monsoon while the termination time may be later. The results further support and supplement the theory of global monsoons, which unifies the low-level and upper tropospheric monsoon as one monsoon system.
