Simultaneous chiral separation using a combinatorial molecular imprinting phase

Molecular imprinting chiral stationary phase against Cbz-L-Serine (Cbz-L-Ser) and Cbz-L-Alaine (Cbz-L-Ala) were prepared utilizing acrylamide + 2-vinylpyridine as combined basic functional monomers. Cross-selectivity was used to obtain simultaneous chiral separations of Cbz-DL-Ser and Cbz-DL-Ala by connecting two columns packed with Cbz-L-Ser and Cbz-L-Ala imprinted chiral stationary phase, respectively.

Experimental velocity measurements and effect of flow maldistribution on predicted permeator performances

The shell-side flow distribution of a parallel flow hollow-fiber gas permeator was characterized using a thermo-anemograph. The permeator has an internal diameter of 103 mm and contains 21000 fibers. The overall fiber packing fraction is 40.1%. Experimental results revealed that shell-side flow maldistributions exist in the operating conditions studied. The gas-flow velocity is the highest at the permeator center, but lowest near the shell wall. The effects of shell-side flow maldistribution on predicted permeator performances are discussed with a simple model. Model calculation results show that flow maldistributions can have considerable effect on permeation systems with relatively high separation factors and stage cuts. (C) 1998 Elsevier Science B.V.

Synthesis of zeolite NaA membranes with high permeance under microwave radiation on mesoporous-layer-modified macroporous substrates for gas separation

This article reported the NaA zeolite membranes with high permeance synthesized with microwave heating method under different conditions: (1) on a macroporous substrate in gel, (11) on a mesoporous/macroporous (top-mesoporous-layer-modified macroporous) substrate in gel, and (111) on a mesoporous/macroporous substrate in sol. In general, the H-2 permeance of the NaA membranes by microwave heating in gel was usually at the level of 10(-6) mol s(-1) m(-2) Pa-1, much higher than that by the conventional hydrothermal synthesis. At similar H-2/C3H8 permselectivity. On the substrate modified mesoporous top layer, the H-2 permeance of the NaA membranes by microwave heating in gel or sol was further enhanced, while maintaining comparable H-2/C3H8 permselectivity, due to the prevention of penetration of the reagent into the pores of the macroporous substrate. Meanwhile, the synthesis took less time in sol than in gel on the mesoporous/macroporous substrate. The NaA membranes synthesized in sol had larger permeance than those in gel and underwent transformation in shorter time. The permeation of C3H8 suggested that there existed unwanted intercrystalline pores or defects in the membranes. © 2005 Elsevier B.V. All rights reserved.