Sulphated zirconia catalyzed acylation of phenols, alcohols and amines under solvent free conditions

Sulphated zirconia prepared by the treatment of a high surface area zirconia (320 m2 g−1) with 1 N H2SO4 shows a strong acidity after calcination at 893 K. It is comparable to that of zeolites, with an enthalpy of adsorption of NH3 close to 130 kJ mol−1. The isotherm of N2 adsorption at 77 K on the sulphated zirconia shows characteristic of mesoporous solid having surface area about 125 m2 g−1, and pores of 4 nm as determined applying the BJH method. The sulphated zirconia obtained by sulphation has 14.5 wt.% S just after oven drying and 1.8 wt.% S after calcination at 893 K. The X-ray diffraction pattern of the calcined sample shows the presence of an intensive peak at 2θ = 30 characteristic of the tetragonal structure. This solid acid has been applied to the acylation of a variety of phenols, alcohols and amines with acetic anhydride as an acylating agent under solvent free conditions. The yields reach about 95% in 10 min, and the catalyst can be recycled several times, so that this process could find useful applications.

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