Diatomite-entrapped hydrosulfate catalysts for the efficient nitration of toluene with nitric acid

Abstract

Diatomite-entrapped hydrosulfate catalysts with the enhanced acidity were prepared by impregnation and 20 wt% KHSO4/diatomite was selected as a heterogeneous catalyst for the catalytic nitration of toluene. The characterization of the catalyst by X-ray diffraction, Scanning electron microscopy, Brunauer–Emmett–Teller, Fourier-transform infrared spectroscopy and NH3 temperature-programmed desorption technique presented that potassium sulfate could be properly dispersed on the surface of the diatomite, the analysis with back titration showed that the total acidity of the catalyst was 0.85 mmol/g, indicating an excellent catalytic activity for the nitration of toluene. The catalyst with outside surface processed by alkali improved the para-selectivity for the nitration of toluene besides the undiminished activity, due to the pore shape of the acidified diatomite to improve the para-selectivity of the nitration process. Under optimal conditions, the catalytic nitration of toluene obtains 88.21 % of total yield and 1.87 of para/ortho (p/o) ratio.