Synthesis and characterisation of high silica zeolites with MOR and MFI framework type from South African coal fly ash.
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Date
2019
Authors
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Journal ISSN
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Publisher
University of the Western Cape
Abstract
High-silica zeolites are porous, aluminosilicate materials known for high thermal stability;
making these materials favourable for application in various industrial processes involving
elevated temperatures. The synthesis of zeolites from alternative feedstock such as coal fly
ash has been investigated previously. Coal fly ash is a waste by-product of the coal
combustion process, which is main source utilised for energy generation in South Africa.
Coal fly ash is an ideal alternative feedstock for zeolites due to the large annual production as
well as the rich mineral content (high in silicon and aluminium). Coal fly ash also contains a
range of other elements which is known to result in environmental problems such as
excessive land-use as well as air, soil, surface water and ground water pollution; including
inorganic cations that may influence the zeolite crystallisation process. However, coal fly ash
has successfully been utilised for the synthesis of a range of low-silica zeolites. High-silica
zeolite synthesis from alternative feedstock has usually focused on the synthesis of zeolite
ZSM-5. Furthermore, these synthesis routes commonly utilised additional silicon sources
and/or a purification step by reflux treatment with a chelating agent to enhance the feedstock
Si/Al ratio prior to crystallisation. This adds complexity to the conversion of coal fly ash to
zeolite process, in terms of cost, energy and time.
Description
Philosophiae Doctor - PhD
Keywords
Zeolites, Waste utilization, Coal fly ash, Geometric simulation, Alkaline activation