Dehydration of tetrahydrofuran by pervaporation using a composite membrane

Tetrahydrofuran (THF) is a strong aprotic solvent, commonly used in the pharmaceuticals industry due to its broad solvency for both polar and non-polar compounds. THF and water form a homogeneous azeotrope at 5.3 wt.% water thus simple distillation is not feasible to dehydrate THF below this concentration. Pervaporation offers a Solution since it is not governed by vapour-liquid equilibria. However many polymer-based pervaporation membranes are cast utilizing THF as the casting solvent and so these membranes have a tendency to swell excessively in its presence. This results in poor separation performance and poor long-term stability and thus renders these membranes unsuitable for THF dehydration. In this study, a new membrane available from CM Celfa, CMC-VP-31 has been tested for the dehydration of THE The membrane shows excellent performance when dehydrating THF with a flux of over 4 kg m(-2) h(-1) when dehydrating THF containing 10wt.% water at 55 degrees C dropping to 0.12 kg m(-2) h(-1) at a water content of 0.3 wt.%. The permeances of water and THF in the membrane were calculated to be 11.76 x 10(-6) and 7.36 x 10(-8) mol m(-2) S-1 Pa-1, respectively, at 25 degrees C and found to decrease in the membrane with increasing temperature to values of 6.71 x 10(-6) and 1.63 x 10(-8) Mol m(-2) S-1 Pat at 55 degrees C. The flux and separation factor were both found to increase with an increase in temperature thus favouring the operation of CMC-VP-31 at high temperatures to optimize separation performance. (c) 2005 Elsevier B.V. All rights reserved.