Showing papers by "Weizhong Qian published in 2015"

Increasing para-Xylene Selectivity in Making Aromatics from Methanol with a Surface-Modified Zn/P/ZSM-5 Catalyst

Abstract: We report a ZSM-5 based catalyst with surface modification of SiO2 to increase the selectivity of para-xylene (PX) in xylene (X) in the methanol-to-aromatics process. The effect of acid strength and acid amount in HZSM-5, Zn/P/ZSM-5, and Zn/P/Si/ZSM-5 on the catalytic performance, including methanol conversion, aromatic yield, and PX selectivity, were studied. The total acid strength and acid amount of the catalyst were crucial for high methanol conversion (around 100%) and high yield of aromatics (>60%), whereas weak external acid sites present in a small amount played an important role in increasing the PX selectivity (in the X isomers) from the usual 23–24% to 89.6%. The results validated the use of a catalyst having a core with strong acid sites in a large amount and an external shell with weak acid sites in a small amount. The contribution of the external surface reaction, including alkylation, isomerization, and dealkylation, to the PX selectivity was evaluated by using PX or ortho-X separately as f...

Ion-Responsive Channels of Zwitterion-Carbon Nanotube Membrane for Rapid Water Permeation and Ultrahigh Mono-/Multivalent Ion Selectivity

Abstract: The rational combination of polymer matrix and nanostructured building blocks leads to the formation of composite membranes with unexpected capability of selectivity of monovalent electrolytes and water, which affords the feasibility to effeciently remove harmful ions and neutral molecules from the environment of concentrated salines. However, the multivalent ion rejection in salined water of routine nanocomposite membranes was less than 98% when ion strength is high, resulting in a poor ion selectivity far below the acceptable value. In this contribution, the ion-responsive membrane with zwitterion-carbon nanotube (ZCNT) entrances at the surface and nanochannels inside membrane has been proposed to obtain ultrahigh multivalent ion rejection. The mean effective pore diameter of ZCNT membrane was dedicated tuned from 1.24 to 0.54 nm with the rise in Na2SO4 concentration from 0 to 70 mol m(-3) as contrary to the conventional rejection drop in carbon nanotube (CNT) membrane. The ultrahigh selective permeabilities of monovalent anions against divalent anions of 93 and against glucose of 5.5 were obtained on ZCNT membrane, while such selectivities were only 20 and 1.6 for the pristine CNT membrane, respectively. The ZCNT membranes have potential applications in treatment of salined water with general NaCl concentration from 100 to 600 mol m(-3), which are widely applicable in desalination, food, and biological separation processes.

Enhancing 5 V capacitor performance by adding single walled carbon nanotubes into an ionic liquid electrolyte

Abstract: A nanofluid electrolyte of single walled carbon nanotubes and ionic liquids can enhance the energy density, power density and cycling stability of nanotube electrodes with a surface area of 600 m2 g−1 at 5 V, by decreasing internal resistance from the bulk phase of ILs to the electrolyte/electrode interface.