Regioselectivity of phenol alkylation using metal impregnated aluminium pillared bentonite

Abstract

Aluminium-pillared clays such as aluminium-pillared bentonite (Al-PLB), aluminium-pillared taeniolite (Al-PLT) were synthesized by intercalation of AlCl₃ into clay interlayers and calcined at 500℃ for 1 h. The impregnation with metal chlorides (InCl₃, LaCl₃, CeCl₃, NdCl₃, and GdCl₃) was carried out with calcination at 450℃. The synthesized clays and raw clays were characterized using powder X-ray diffraction, N₂ adsorption-desorption, temperature programmed desorption of ammonia and inductively coupled plasma optical emission spectrometry techniques. These synthesized catalysts were used for acid-catalyzed phenols alkylation. The catalytic activity of synthesized clays was compared with raw clays (bentonite and taeniolite), different metal chlorides on Al-PLB and calcination temperatures and with Al-PLT. InCl₃/Al-PLB provided significantly the highest yield for O-alkylation, while Al-PLT calcined at 450℃ was selective for mono-substitution of C-alkylated product. The optimized conditions for acid-catalyzed reaction were disclosed. Those reactions could smoothly be proceeded in the presence of synthesized clays to furnish the corresponding products in good to excellent yield with excellent selectivity for O-alkylation under mild conditions.