O'Brien, Matthew Graham; (2007) Investigations into the formation of nanoporous materials. Doctoral thesis , UCL (University College London).

Preview

Text O'Brien.MG_thesis.Redacted.pdf Download (68MB) | Preview

Abstract

The formation processes of a number of microporous materials have been investigated using a powerful combination of ex situ and in situ experimental techniques together with computational modelling. The materials investigated include both zeolites and their aluminophosphate counterparts, which have been previously synthesised and have shown some potential as industrial catalysts. Using an array of techniques has allowed different stages (such as nucleation or crystal growth) to be monitored as well as different aspects of the gel chemistry, such as the geometry of substituted metal ions and the location and conformation of organics within the framework. For MeAPO-34 and A1PO-5, quantum mechanical calculations have examined the early stages of A1PO formation and shown that, unlike silicates, chain growth seems to be preferred. Raman techniques have then identified metal-organic interactions and changes in organic conformation, key to the formation of a particular A1PO over another. For CoAPO-36, energy dispersive X-ray diffraction has been used to monitor crystal growth using three different organic species, and significant differences in the rate of formation have been identified. By combining these observations with crystallographic measurements and molecular mechanical modelling, it has shown that the rate of formation can be affected by both the size and shape of the organic used to form the crystal structure. Combined small angle/wide angle X-ray diffraction has also been used to follow the formation of zeolite-A throughout the nucleation and growth process and, it has been shown, that the insertion of the substituted metal germanium can alter the precise nature of the aggregation and dissolution processes occurring within this system. Finally, a synthesis project has been initiated to attempt to introduce mesopores into microporous A1PO materials. The synthesis of hierarchical microporous-mesoporous materials is of great interest as they offer advantages over both microporous and mesoporous materials for use in catalytic and other applications. The results from this work are very promising, and both A1PO-5 and MeAlPO-34 have been synthesised with some apparent mesoporosity, using non-ionic surfactants. A mechanistic process for the formation of these materials based on micelle and mesophase formation has also been proposed.

Download activity - last month

Export as JSONCSVXML

Download activity - last 12 months

Export as JSONCSVXML

Downloads by country - last 12 months

Export as JSONXMLCSV

Archive Staff Only

View Item