Intensification studies of heterogeneous catalysts: probing and overcoming catalyst deactivation during liquid phase operation
In addition to high levels of catalytic activity and target product selectivity, promising heterogeneous catalysts must also possess sufficient levels of stability for scale up, i.e. intensification, and industrialisation to be realised. However, this third – often determining – keystone is often overlooked, particularly in academic literature. This tutorial review therefore covers several elements related to the study of heterogeneous catalyst stability during liquid phase operation, an increasingly important area of heterogeneous catalysis. Particular emphasis is placed upon how stability data can be obtained and how the various forms of catalyst deactivation can be experimentally identified, and attention is drawn to emerging methods by which such events can be overcome or minimised. Drawing on some of our team's recent research, particular emphasis is placed on the stability studies of Lewis acidic silicates, state-of-the-art catalysts for a range of emerging liquid–solid catalytic processes. Factors related to heterogeneous nanoparticle catalysts are also covered. The purpose of this review is to draw attention to the issue of solid catalyst stability during liquid phase operation, and provide researchers with the information required to begin kinetic and spectroscopic studies of this determining catalytic event.