Patent ID: 8900417

Claim:
A method for purifying 2,3,3,3-tetrafluoropropene, (1) the purification method comprising the step of subjecting a mixture comprising 2,3,3,3-tetrafluoropropene and hydrogen fluoride to extractive distillation in a distillation column A using an extractant, thereby obtaining a fraction I that contains 2,3,3,3-tetrafluoropropene and has a lower ratio of hydrogen fluoride to 2,3,3,3-tetrafluoropropene than the mixture, while obtaining a fraction II that contains hydrogen fluoride and has a lower ratio of 2,3,3,3-tetrafluoropropene to hydrogen fluoride than the mixture; (2) the extractant comprising at least one member selected from the group consisting of: (i) alcohols represented by ROH, wherein R is a C 1-5 alkyl group, (ii) ethers represented by ROR′, wherein R and R′ are the same or different, and each is a C 1-4 alkyl group, (iii) fluorinated alcohols represented by RfOH, wherein Rf is a C 1-3 fluoroalkyl group, (iv) ketones represented by RCOR′, wherein R and R′ are the same or different, and each is a C 1-4 alkyl group, (v) esters represented by RCOOR′, wherein R and R′ are the same or different, and each is a C 1-4 alkyl group, (vi) polyols represented by R(OH) n , wherein R is a C 1-4 alkyl group, and n is an integer of 2 to 3, and (vii) ethylene glycols represented by R 1 O(CH 2 CH 2 O) n R 2 , wherein R 1 and R 2 are the same or different, and each is hydrogen or a C 1-4 alkyl group, and n is an integer of 1 to 3.