(225d) Ultrapurification of Isopropyl Alcohol by a Membrane

Silicon wafers are subjected to an extraordinary amount of cleaning during semiconductor manufacturing to remove metallic impurities, nanoparticles, water and organic compounds that are nonvolatile, semivolatile or volatile. Ultrapure isopropyl alcohol (IPA) is needed since it is used to remove various organic contaminants. A vacuum membrane distillation process can be employed using two different types of membranes to produce ultrapure IPA. One type of membrane involved different polymeric nanoporous substrates having fluorinated surface coatings exposed to a mild vacuum. The second type of membrane was a subnanoporous perfluorocopolymer exposed to a substantial vacuum; we report here results using the second type of membrane. The condensed IPA quality was determined by gas chromatography-mass spectrometry (GC-MS) when the hot feed IPA at 40-45^oC had a 2 ppm spike of C7-C30 hydrocarbons. The subnanoporous perfluorocopolymer membrane achieved in the IPA condensate 99.36% purification of the 143809 ppb of C7-C30 impurities injected into the IPA feed; further, there were no C19-C30 present in the permeate/condensate. The basis of the high purification achieved has been discussed and evaluated vis-a-vis other membrane processes such as reverse osmosis.