Research On Waste Acid Of P-tert-butyl Toluene Processes

P-tert-butyl toluene is used as raw material of p-tert-butylbenzoic. Sulfuric acid is used as catalyst in p-tert-butyl toluene processes. Sulfuric acid reacts with toluene easily to yield by-products which contain o-toluene sulfonic acid, m-toluene sulfonic acid, p-toluene sulfonic acid. The by-products are completely dissolved by sulfonic acid and compounds of waste acid occur. In order to solve the problem of recycling waste acid. The separation of toluene sulfonic acid from the sulfonic acid and that of toluene sulfonic acid isomers are studied. The mass fraction of free sulfonic acid is detected in p-toluene sulfonic acid. The structure of toluene sulfonic acid is analyzed. The residuum of the waste acid is used to prepare solid acid catalyst, the performance of which is detected. The catalysis is reflected in esterification reaction.Water dilution method, toluene-ethanol method, dichloroethane-ethanol method were used for separation of p-toluene sulfonic acid. The result indicated that preferred conditions of water dilution method are that the volume of water accounds for20%that of waste acid, recrystallization time is24h. The extraction ratio of p-toluene sulfonic acid is up to57.34%when the volume of sample of p-toluene sulfonic acid is250mL. The preferred conditions of toluene-ethanol method are that the temperature is20℃, the stiring time is15min, the ratio of toluene and ethanol is1.6:1, the amount of toluene and ethanol is15mL. The minimum mass fraction of free acid is4.63%in product acquired. The preferred conditions of dichloroethane-ethanol method are that crystallization temperature is10℃, the ratio of ethylene dichloride and ethanol is15:1, dosage of dichloroethane is120mL. The minimum mass fraction of free acid is0.039%in product acquired. The structure of p-toluenesulfonic acid is analyzed by IR spectra.Water dilution method was used for separation of o-toluene sulfonic acid. The result indicated that preferred conditions of water dilution method are that the weight of water accounds for24%that of sample, the crystallization temperature is4℃. The melting point of product obtained is62-64℃. The structure of o-toluene sulfonic acid was analyzed by IR spectra.The residuum of the waste acid was used to prepare solid acid catalyst, which used active carbon as carrier. The acid value was detected by titration. The apperance was detected by SEM. The result indicated that the preferred conditions are that the activation time is2h, the temperature of adsorption is25℃, the stiring time is6h, the weight of active carbon accounds for20%that of waste acid. The structure of solid acid catalyst was analyzed by IR spectra. Thermogravimetric analysis determined that the maximum service temperature of solid acid catalyst was210℃Solid acid catalyst obtained was used as catalyst in esterification reaction of benzoic acid and methanol. The result indicated that preferred conditions of esterification reaction are that the reaction time is5h, the ratio of acid and alcohol is1:6(mole), the weight of catalyst accounds for6%that of benzoic acid, reaction temperature is75℃. The highest esterification rate is83.24%. Solid acid catalyst is reused for5times, the average esterification rate is82.83%.