Study On The Acetylation Of Anisole Catalyzed By Hβ Zeolite

Friedel-Crafts acylation is one of the most important synthetic reactions for the preparation of aromatic ketones, which are widely used as intermediates in fine chemicals and pharmaceutical industries. Up to now, the methods for preparing aromatic ketones still involve homogeneous metal chlorides or protonic acid used as catalysts in batch reactors via Friedel-Crafts acylation in industry. However, complexity, high dosage and non-regeneration of catalysts and the large three wastes are the disadvantages of the conventional methods. It is very important for the clean and green Friedel-Crafts acylation methods be explored in which the catalysts can be regenerative.The acylation of aromatic ethers are most actively pursued in Friedel-Crafts acylation. In order for the theoretical foundation in the industrialization of the acylation of aromatic ethers, in the paper, the liquid acylation of anisole with acetic anhydride was studied with a normal atmosphere or high pressure without addition of any solvent used zeolite Hβas catalyst in a fixed bed reactor.Considering the mechanism is Lewis acid catalysis in the Friedel-Crafts acylation catalyzed by metal chlorides, the effects of activation temperature on anisole conversion was studied through varying the activation temperature of Hβzeolite in order to determine whether Lewis acid play roles in acylation catalyzed by zeolites. The zeolites were characterized. The results showed that the above acylation was catalyzed by Br?nsted acid and not Lewis acid. The calcination and activation temperature before reaction was by preference the temperature at which the templates were removed.The acylation of anisole with acetic anhydride was catalyzed by Hβzeolites modificated with several acids at 90℃. Best results were achieved in the modification with citric acid, tartaric acid, and hydrochloric acid with a suitable concentration considering activity and stability altogether. The corresponding zeolites were characterized. The results showed that the main factor affecting the activity was the strength of Br?nsted acid sites and the stability was related to the distribution of the Br?nsted acid site on the surface of the zeolites.The acylation of anisole with acetic anhydride catalyzed by Hβzeolites was studied at higher reaction temperature (150℃). The results showed that the activity of Hβzeolites in the acylation was related to the total Br?nsted acid amount. The result was different from which the reaction conducted at lower temperatures because of the roles of acid sites played fully at elevated temperatures.The technological conditions were optimized via unifactor experiment using Hβzeolites as the catalyst in the acylation of anisole with acetic anhydride. The catalysts before and after reaction were characterized and the regeneration tests were performed. The results showed that in order for the catalysts to be more active and at the same time more stable (lifetime), the acylation should be conducted at suitable temperatures where the roles of active sites played fully but not at higher temperatures where fast deposition of carbonaceous substances occurred and the ratio of anisole to acetic anhydride should be controled to make the framework dealumination (irreversible deactivation) by the product acetic acid reduced to minimum, whereas carbonaceous substances deposited (reversible deactivation) can be removed by calcination during the regeneration of the catalysts.