New Methods for Modifying Zeolites to Create Mesoporosity

Abstract

Zeolites, as microporous, aluminosilicate minerals are widely used as catalysts and absorbents in industrials. In some applications (e.g., petroleum industries), the pristine micropores of zeolites limit the diffusions of bulk molecules from accessing the intracrystalline activate sites giving a low effective utilisation. The creation of hierarchical zeolites by introducing mesoporosity into microporous zeolite framework is one of the most practical ways to reduce such limitations. The microwave-assisted chelation (MWAC) dealumination, and ultrasound irradiation desilication are both effective and efficient method for mesoporosity creation in synthetic zeolites, especially ones with low silicon to aluminium ratios (SAR) such as FAU Y. In this PhD project, development of process intensification for post-synthetic hierarchical zeolites was systematically investigated. Here, the work was carried out by: (i) demonstrating the introduction of secondary mesoporosity into microporous zeolites improves catalytic activity in heterogeneous reactions; (ii) developing the effect of ultrasound-assisted desilication for dealuminated zeolites to create mesopores; (iii) proving MWAC methods are effective in fabricating hierarchical zeolites and the degree of dealumination is related to the number coordination centres in the acidic chelating agent; and (iv) developing an insight into the mechanism of the MWAC dealumination process and understanding the interactions between the chelating agent/mineral acid (i.e., H4EDTA and HCl) and the zeolite framework under microwave irradiation. The relevant research findings from the project on the process intensification of post-modification for hierarchical zeolites provides the guidance for the design of porous catalysts with desired properties and demonstrate the potential of applying such approaches for fabricating secondary mesoporosity into various topology zeolite frameworks, and even of applying in practical industrial utilisations.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Stuart Holmes (Supervisor) & Xiaolei Fan (Supervisor)