Model microporous AlPO catalysts for establishing structure-performance relations in C4 isomerization

Abstract

This work is a fundamental study of metal doped aluminophosphates (MAlPOs). These materials have a diverse range of dopant and structural combinations that can significantly impact catalytic character. Butane isomerisation has been used as a test reaction for zeolites, to investigate acidic and structural effects, and to correlate the impact of catalyst design choices on this behaviour. This work seeks to extend this methodology to MAlPOs and establish acidic and structural characteristics that can be applied to target reactions.
By using butane isomerisation in this manner, this work has demonstrated how a number of key catalytic structural characteristics influence reactivity in an AlPO-5 system. By using Cu²⁺, Ni²⁺, Co²⁺, and Mg²⁺ dopants, it was shown how acid site strength can be tuned. It was also demonstrated that dopant concentration has a crucial factor in determining catalytic efficiency, with too few, or too many active sites being equally detrimental.
This understanding was extended to studying the influence of topology, which was found to have a dramatic influence on catalyst behaviour. By studying Co²⁺ substituted AlPO-5, AlPO-18 and AlPO-11 with butane isomerisation, the effect of the quantity of acid sites as well as the confinement effect of the topologies was rationalised. It was found that the influence of acid site quantity is topology specific. Additional techniques were developed for studying the confinement effect, with analysis of the pentane fraction and the n-butane/isobutane equilibria being established as metrics.
These findings were then validated using a second test reaction, ethanol dehydration. It was found that the behaviour observed for butane isomerisation was also influential on ethylene formation, with catalytic trends ratifying observations from butane isomerisation.

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Identifiers

ORCID for Joshua John Mark Le Brocq: orcid.org/0000-0001-5534-8053

ORCID for Robert Raja: orcid.org/0000-0002-4161-7053

ORCID for Marina Carravetta: orcid.org/0000-0002-6296-2104

ORCID for Mark Light: orcid.org/0000-0002-0585-0843

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