The synthesis of heterogeneous 7-amino-1-naphthalene sulfonic acid immobilized silica nano particles and its catalytic activity

7-Amino-1-naphthalene sulfonic acid (ANSA) was immobilized onto silica via a simple sol–gel technique to form strong Brønsted acid site, RHANPSO3H. Spherical nano sized catalyst particles were obtained in this study. The 29Si MAS NMR showed the presence of T3, T2, Q3 and Q4 silicon centers. The 13C MAS NMR analysis showed the presence of three chemical shifts consistent with the three carbon atoms of the propyl group. Chemical shifts in the range 122.2–138.9 ppm indicate the presence of the naphthalene ring. The catalytic performance of RHANPSO3H was tested in the esterification of n-butyl alcohol with different mono and di-acids at 117 °C with 88% conversion of respective alcohols and 100% selectivity towards the ester. The catalyst could be regenerated by washing with ethanol and drying at 180 °C for 24 h.