Patent ID: 8246858

Claim:
A process for inhibiting polymerization of an aromatic vinyl compound which comprises adding (A) at least one nitrogenous aromatic compound selected from the group consisting of phenazine, 3-amino-7-hydroxyl-2-methylphenazine, tetrabenzo [a,c,h,j] phenazine, quinoxaline and 2-methyl-quinoxaline, in combination with (B) a sulfonic acid compound selected from the group consisting of dodecylbenzene sulfonic acid, pentadecylbenzenesulfonic acid, xylenesulfonic acid, cumenesulfonic acid, p-toluenesulfonic acid and methanesulfonic acid, during the stage of producing, purifying, storing or transporting of the aromatic vinyl compound, wherein the nitrogenous aromatic compound is added in an amount of from 10-190 ppm and the sulfonic acid compound is added in an amount of from 10-200 ppm, based on the aromatic vinyl compound.