Title
Zeolite-encapsulated Co(II)[H4]salen and [H2]salen complexes: pulp bleaching catalysts with enhanced bleachability
Authors
XUE-FEI ZHOU and KAI TANG

Received September 23, 2014
Published Volume 50 Issue 9-10 October-December
Keywords tetrahydro-salen complex, encapsulation, pulp delignification, heterogeneous catalysts, bleachability

Abstract
Salen complexes are an important class of coordination compounds, which have been used to catalyze a wide variety of reactions with exceptional selectivity. Considerable efforts have been made by our research group focusing on additional developments, including the heterogenization of catalytic systems and hydrogenation for application in catalytic delignification of pulp. [H2] and [H4]salen type complexes of cobalt encapsulated in zeolite cages were synthesized and characterized by spectroscopic techniques. Their catalytic properties were then evaluated in the catalytic delignification of pulp using peracetic acid (CH3COOOH) as an oxidant. The encapsulation and hydrogenation of the complexes yielding increased spatial separation, which strongly enhanced the activity of complexes, were found to play a key role in the selective delignification of pulp. With encapsulated and hydrogenated complexes as catalysts, pulp was selectively delignified to a high brightness. The catalysts that were developed could suitably be used in green bleaching for the pulp industry.