small amount of thiophenes and shows a bromine index of about 10 and acid wash color test of no 4 the bromine index represents the number of milligrams of bromine consumed by 100 g of sample according to astm d1491 the benzene is fed to a purification step 17 using an active material the step 17 is a type of an adsorping column usually packed with active materials shaped in granular forms the operating conditions of such column are such that a temperature is in a range of the room temperature to 120 u00b0 c and any pressure can be applied so long as benzene can be kept in a liquid phase at that temperature but usually the pressure is 5 20 kg cm 2 a liquid hourly space velocity is not critical either but usually is 0 1 to 10 vol vol hour these conditions are appropriately selected depending upon the kind of the active material purified benzene substantially freed from the impurities such as olefins thiophenes etc in the purification step 17 is obtained from 18 the product benzene shows the color solidification point acid wash color etc which each satisfy the atsm standard requirements of pure benzene crude benzene obtained by hydrodealkylation of the by product cracked gasoline from naphtha cracking was freed from other aromatic hydrocarbon fractions such as toluene xylenes etc by distillation the resulting product was a substantially pure benzene and passed through the layer of activated clay nikkanite g 36 made by nippon kasseihakudo co ltd under the following two conditions benzene.