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Abstracto

Smectitic clays as clean and cost effective heterogeneous catalysts

Oscar Kelly

As the World shifts to a greener more sustainable future, processes and reagents the chemical industry have depended upon for years are increasingly under greater scrutiny. One approach to the challenge of finding better ways of producing the same quality is to look to past catalyst technologies that have fallen out of favor in recent years. Clay, more specifically montmorillonite, based catalysts have been used for many years as clean, cost effective solid Lewis or Brønsted acid catalysts. At low moisture contents, the ionising effect of the charged calcium montmorillonite surfaces can generate Hammett acidities of -3. Acid activation can push the Hammett acidities to as low as -8 as well as open up potent Al³⁺ and Fe³⁺ Lewis acid sites. Said acidified montmorillonites have been reported as being excellent catalysts for a range of reactions, including but not limited to: Friedel-Crafts alkylation, esterification, dehydration, siloxane equilibration and Diels-Alder cyclo-addition. In addition to their inherent catalytic properties smectitic clays have the potential to be used as supports for reactive ionic or crystalline metal centres through such preparative techniques as intercalation, pillaring or reductive seeding of metal nano-particles.

In this presentation we will firstly detail the perfromance of FULCAT^® acid activated clay catalysts in Friedel-Crafts nonylation of diphenylamine (DPA), polymerisation of cyclic siloxanes and esterification reactions. These reactions were chosen due to their commercial importance. In the final part of the poster we briefly explore the opportunities for synthetic clays as scaffolds for metal nano-particles.