Unmanned Aerial Vehicle(UAV)-aided communication holds great potential to enhance the transmission performance.However,the information security remains a fundamental requirement due to the high possibilities of line-o...Unmanned Aerial Vehicle(UAV)-aided communication holds great potential to enhance the transmission performance.However,the information security remains a fundamental requirement due to the high possibilities of line-of-sight links and the broadcast nature.展开更多
Small-pore zeolites with 8-rings are pivotal catalytic materials to produce light olefins from non-petroleum resources employing methanol-to-olefins or syngas-to-olefins processes.The constraints of cage openings on t...Small-pore zeolites with 8-rings are pivotal catalytic materials to produce light olefins from non-petroleum resources employing methanol-to-olefins or syngas-to-olefins processes.The constraints of cage openings on the diffusion of light olefins play a crucial role in tailoring catalytic performance.However,the relation between the elegant structures of zeolites and the underlying diffusion kinetics is not well understood yet.In this work,the diffusion of ethene in seven cage-structured 8-ring zeolites(LEV,CHA,AEI,ERI,AFX,SFW and RHO)was systematically investigated using molecular dynamic simulations at different ethene loadings and temperatures.The self-diffusion coefficient highly relates to the zeolite framework structures and increases with both ethene loading and temperature.Ethene diffuses the fastest in RHO and the slowest in ERI and LEV.The self-diffusion of ethene from one cage to the other follows the Arrhenius plot.The activation energy is irrelevant to the loading and decreases as ERI>LEV>SFW∼AFX>CHA>AEI>RHO.The pre-exponential factor linearly increases with the loading except in ERI and LEV,with smaller openings,and increases as ERI∼LEV<CHA∼AEI∼AFX∼SFW<RHO under similar loading with respect to the number of Si atoms.The activation energy and the pre-exponential factor of ethene diffusion are revealed to correlate well with two simple structure descriptors,i.e.,the opening size of 8-rings and the accessible volume of each Si atom,respectively.This theoretical work thus unravels the intrinsic structure characteristics quantifying the individual diffusion kinetic parameters,and may offer some facile implications to tailor the diffusion behavior of light hydrocarbons in cage-structured 8-ring zeolites.展开更多
文摘Unmanned Aerial Vehicle(UAV)-aided communication holds great potential to enhance the transmission performance.However,the information security remains a fundamental requirement due to the high possibilities of line-of-sight links and the broadcast nature.
基金the financial support from the National Natural Science Foundation of China(92045303,21673295)the National Key Research and Development Program of China(2017YFB0702800,2016YFB0701100)The computational resources from Sinopec Geophysical Research Institute are acknowledged.
文摘Small-pore zeolites with 8-rings are pivotal catalytic materials to produce light olefins from non-petroleum resources employing methanol-to-olefins or syngas-to-olefins processes.The constraints of cage openings on the diffusion of light olefins play a crucial role in tailoring catalytic performance.However,the relation between the elegant structures of zeolites and the underlying diffusion kinetics is not well understood yet.In this work,the diffusion of ethene in seven cage-structured 8-ring zeolites(LEV,CHA,AEI,ERI,AFX,SFW and RHO)was systematically investigated using molecular dynamic simulations at different ethene loadings and temperatures.The self-diffusion coefficient highly relates to the zeolite framework structures and increases with both ethene loading and temperature.Ethene diffuses the fastest in RHO and the slowest in ERI and LEV.The self-diffusion of ethene from one cage to the other follows the Arrhenius plot.The activation energy is irrelevant to the loading and decreases as ERI>LEV>SFW∼AFX>CHA>AEI>RHO.The pre-exponential factor linearly increases with the loading except in ERI and LEV,with smaller openings,and increases as ERI∼LEV<CHA∼AEI∼AFX∼SFW<RHO under similar loading with respect to the number of Si atoms.The activation energy and the pre-exponential factor of ethene diffusion are revealed to correlate well with two simple structure descriptors,i.e.,the opening size of 8-rings and the accessible volume of each Si atom,respectively.This theoretical work thus unravels the intrinsic structure characteristics quantifying the individual diffusion kinetic parameters,and may offer some facile implications to tailor the diffusion behavior of light hydrocarbons in cage-structured 8-ring zeolites.
