Decrement of coke from phenol hydroxylation on iron on zeolite beta by employing dealuminated support

Abstract

An attempt to decrease coke formation from phenol hydroxylation on iron catalyst supported on zeolite beta (Fe/HBEA) was investigated. HBEA was dealuminated by refluxing in nitric acid. The dealumination removed all framework aluminum atoms and presumably generated hydroxyl nests of the tetrahedral vacant sites which were strongly acidic. An iron catalyst supported on dealuminated zeolite beta (Fe/D-BEA) was prepared by stirring the dealuminated HBEA in a solution of Fe(NO3)2. The obtained catalyst had an Fe loading 2.60 wt%. The Fe had an oxidation state +3 and tetrahedral coordination. After loading, the zeolite structure was slightly contracted by the insertion of Fe ions into the vacant sites and calcination. The strong acid sites on D-BEA were suppressed. When Fe/D-BEA was tested in phenol hydroxylation, a steady conversion around 56 % was reached in 6 min. Catechol and hydroquinone were the major products with the mole ratio 2:1. However, cokes were still observed. The type of cokes from Fe/D-BEA was similar to those from Fe/HBEA but the amount from Fe/D-BEA was lower. Thus, the product yields from Fe/D-BEA were higher.