The effect of hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios on its pore structure and catalytic performance

Hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios(Hier-ZSM-5-x,where x=50,100,150 and 200)were synthesized using an ordered mesoporous carbon-silica composite as hard template.Hier-ZSM-5-x exhibits improved mass transport properties,excellent mechanical and hydrothermal stability,and higher catalytic activity than commercial bulk zeolites in the benzyl alcohol self-etherification reaction.Results show that a decrease in the Si/Al ratio in hierarchical single-crystal ZSM-5 zeolites leads to a significant increase in the acidity and the density of micropores,which increases the final catalytic conversion.The effect of porous hierarchy on the diffusion of active sites and the final catalytic activity was also studied by comparing the catalytic conversion after selectively designed poisoned acid sites.These poisoned Hier-ZSM-5-x shows much higher catalytic conversion than the poisoned commercial ZSM-5 zeolite,which indicates that the numerous intracrystalline mesopores significantly reduce the diffusion path of the reactant,leading to the faster diffusion inside the zeolite to contact with the acid sites in the micropores predominating in ZSM-5 zeolites.This study can be extended to develop a series of hierarchical single-crystal zeolites with expected catalytic performance.

Norton-Hoff model for deformation of growing solid shell of thin slab casting in funnel-shape mold

A funnel-type mold is commonly used to provide necessary clearance for the submerged entry nozzle in the thin slab casting(TSC).The partially solidified shell is subjected to the mechanical deformations,which can lead to the defects formation and,as a results,to a breakout.Traditionally,the results of the flow simulation,performed by the finite volume method(FVM),are fed to the external package for the finite element analysis of stress and strain.A coupled model was assembled using“creeping solid”approach by blending the Norton-Hoff viscoplastic stress for the solidifying shell with the Newtonian viscous stress of the liquid melt.The FVM was used to combine both liquid and solid stress models within a single solver.The iterative procedure based on the improved both side diffusion method was introduced to treat the nonlinear relation between the viscoplastic stress and the strain rate.The modeled shell thickness was verified by previously published breakout measurements and the simulation results.Temperature distribution,obtained during the TSC simulation,dominantly corresponds to the viscoplastic range.Developed numerical approach is robust and has direct industrial application.

Effect of levothyroxine replacement therapy on improving diffused left ventricular myocardial lesions in patients with hypothyroidism

Objective To study the effect of levothyroxine replacement therapy on improving diffused left ventricular myocardial lesions and cardiac function in patients with hypothyroidism.Methods Our research included 2groups:Hypothyroidism group,n=20,newly diagnosed patients and Control group,n=17,normal healthy subjects.Diffused left ventricular myocardial lesions