Screening Using HTE Techniques

As can be concluded from Fig. 9.16, the conversion values over all catalysts increase upon heating from 80 to 130°C, following a common Arrhenius equation. Above 130 °C the catalysts start to behave differently the conversion over Ge(0.09)ZSM-5(36) increases further (from 92 to 100%) upon increasing the tem- 

The set of catalysts selected for the dehydration of 2-butanol was also tested for the Friedel-Crafts acylation of anisole [69, 70]. The catalytic test was performed in the liquid phase due to the high boiling points of the reactants and products of this reaction. Anisole was reacted with acetic anhydride at 120 °C in the absence of solvent. In principle, acylation can occur on both the ortho and para positions of anisole. The main product ( 99%) over all catalysts in this study was para-methoxyacetophenone, indicating that the reaction predominantly takes place inside the zeolite micropores. The same trend in catalytic activity as in the 2-buta-nol dehydration reaction is observed the conversion of anisole into para-nicihoxy-acetophenone increases upon increasing Ge content of the catalyst (Fig. 9.17) [67]. The main cause of deactivation for this reaction is accumulation of the reaction products inside the micropores of the zeolite. The different behavior of Ge-ZSM-5, compared with ZSM-5, may therefore be due to improved diffusional properties of the former, as the presence of additional meso- and macropores allows for 

The Ge-ZSM-5 catalysts have also been screened in other test reactions [67]. In general, materials with high germanium content appeared to suffer to a much smaller extent from deactivation than samples with lower germanium levels for most of the acid-catalyzed reaction studied. In this way it was shown that the difference in catalytic performance originates from the presence of Ge in these samples and that the improved catalytic stability is similar in several acid-catalyzed test reactions. 

The application of HTE techniques for studying liquid-phase reactions has been demonstrated for several catalytic reactions. Good results are obtained when the design of the catalyst library, typically a small, full-factorial library of 24 catalysts, is coupled to an extensive literature survey that pinpoints the major variables of the reaction system under study. Combining less important parameters into the reduced and optimised catalyst library can be used to further fine-tune the catalyst. 

The exploration of silsesquioxane-based titanium catalysts has resulted in valuable insight into the fundamentals of silsesquioxane formation. Furthermore, an improved synthesis method for the important precursor R7Si7012H3, with R=cyclopentyl, was identified. Finally, new catalytic systems based on R2Si207H4, with R=tert-butyl, were discovered. 

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