Researches On Oxidation Of M-xylene Catalyzed By Phosphotungstic Acid Supported On Modified Activated Carbon

Isophthalic acid (IPA) is an important intermedia in chemical industry. Co-Mn-Br is applied as the catalyst system to the synthese of IPA in the traditional process. Because of the equpments corroded and the environment populated seriously, the free-Br process is taken more and more seriously.HPW12supported on modified activated carbon is substituted for bromide as the catalyst. The effect of different reagents and modification conditions on the activity of the catalyst is investigated.First, the effect of activated carbon modified by KOH, NaOH, Fe(NO3)3, NaS2O8and HNO3on the catalyst activity is investigated. It’s showed that:(a) KOH, NaOH and Fe(NO3)3modifying activated carbon decreases the catalyst activity;(b) NaS2O8and HNO3modifying activated carbon increases the catalyst activity;(c) the effect of activated carbon modified by NaS2O8on the catalyst activity isn’t distinct, but that of activated carbon modified by HNO3is marked.According to the results, we found that HNO3modifying activated carbon improves the catalyst activity most markedly. So HNO3is chosen as the reagent to modify activated carbon.Then, the effect of the concentration of HNO3, impregnation time, impregnation temperature, activation temperature and activation time is inspected. It’s found that:(a) When the HNO3concentration is lower than50%(vol), with the increase of the concentration of HNO3, the catalyst activity is improved firstly, then dropped secondly and improved at last. The optimal HNO3concentration is10%(vol);(b) As the impregnation time is extended, the catalyst activity improved firstly and then droped. The optimal impregnation time is8hours;(c) With the rise of the impregnation temperature, the cataly activity is improved firstly, then dropp secondly and improved at last. The optimal impregnation temperature is45℃;(d) The optimal activation temperature and activation time is700℃and4hours, respectively;(e) The catalyst activity can be improved with the enhancement of the modified activated carbon’s polarity and hydrophily;(f) The catalyst activity can be improved with the increase of activated carbon’s specific area.