Multi SO3H supported on carbon nanotubes: a practical, reusable, and regioselective catalysts for the tert-butylation of p-cresol under solvent-free conditions

The present study describes the synthesis, characterization, and catalytic activity of sulfonated multi-walled carbon nanotubes and sulfonated single-walled carbon nanotubes in the tert-butylation of p-cresol. The catalysts were prepared using a chemical and simple process and it characterized by scanning electron microscopy, Fourier transform infrared, and Raman spectroscopy, thermogravimetric analysis, and acid-base titration. The sulfonated multi-walled carbon nanotubes and sulfonated single-walled carbon nanotubes have been used as practical heterogeneous catalytic systems in the tert-butylation of p-cresol under solvent-free conditions. Sulfonated multi-walled carbon nanotubes with the highest total density of SO3H groups possessed high activity for p-cresol conversion and high selectivity than the sulfonated single-walled carbon nanotubes. This methodology offers some advantages of high selectivity, and high yields, easy work-up, solvent-free conditions, and reusable catalyst. Moreover, the catalytic system was used in scale-up under similar optimized reaction conditions.