Friedel-Crafts acylation of anisole with octanoic acid over acid modified zeolites

Friedel-Crafts acylation of anisole using octanoic acid as a green acylating agent was studied over zeolites free of solvent. It was found that a mixed organic acid, composed of tartaric acid and oxalic acid, modified H beta (Mix-H beta) zeolite showed the best catalytic performance among the catalysts studied. The conversion of octanoic acid and the selectivity for p-octanoyl anisole were 72.7% and 82.5%, respectively. Inductively coupled plasma analysis (ICP) and Al-27 MAS NMR indicated dealumination of the parent H beta zeolite due to the treatment of the mixed organic acid, leading to more accessible active sites and accounting for the better catalytic activity of the Mix-H beta zeolite. Furthermore, lower strength of Lewis acid sites and Bronsted acid sites of the Mix-H beta zeolite, as demonstrated by Fourier Transform Infrared Spectrometry after adsorption of pyridine (Py-IR), are advantageous to suppress the demethylation of anisole and the subsequent esterification of thus formed phenol, accounting for its higher selectivity toward p-octanoyl anisole.