Studies on physico-chemical changes in zeolite beta in mononitration of toluene

In the present work, the stability and regenerability of H-Beta zeolite in toluene mononitration is studied. Nitration of toluene is carried out in batch mode under reflux conditions using various molar ratios of toluene and nitric acid. Semi batch experiments under reflux are also conducted where nitric acid is dosed at predetermined rates to the reaction mixture containing toluene and the catalyst. The catalyst used in semi batch experiments is found to exhibit consistent performance upto three cycles. The possible cause of consistent activity of the catalyst with respect to para-selectivity has been explored. The physico-chemical changes, if any, in the catalyst is examined for structural stability and presence of pore blockages using sophisticated analytical tools like XRD, EDX, FTIR and ²⁷Al MAS-NMR. These studies indicate the commercial potential of cleaner option of replacing sulfuric acid with zeolites in toluene nitration.