Abstract:

A series of supported ammonium molybdophosphat catalysts(AMPA/SiO2) with different loading was prepared from tetraethyl orthosilicate, ammonium molybdate and ammonium dihydrogen phosphate by sol-gel method. The samples were characterized by X-ray diffraction(XRD) and IR spectrometry. The catalytic activities of these catalysts were evaluated for the liquid phase nitration of benzene in 65% nitric acid without solvent at 70 ℃. Results indicate that supported catalyst still maintained the Keggin structure of ammonium molybdophosphate catalyst and exhibited high nitration reaction catalytic activity and high selectivity of mononitrobenzene. Among these catalysts, the catalyst with 10% loading showed maximum activity(96%), with 100% selectivity towards mononitrobenzene. The reusability of the catalysts was also studied, and it was found that there was no obvious change for catalyst phase and structure after being reused four times, although the active component had somewhat been lost in the reaction process.