abstracts - Институт катализа им. Г.К. Борескова

KS-II-2SUSTAINABLE HETEROGENEOUS ACID CATALYSIS BY HETEROPOLY ACIDSKozhevnikov I.V.Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UKE-mail: kozhev@liverpool.ac.ukThis lecture gives a survey of perspectives of heteropoly acids (HPA) as solid acidcatalysts for clean organic synthesis. The focus is on several approaches that could beeffective in overcoming the deactivation of HPA catalysts to achieve sustainable catalystperformance.Catalysis by heteropoly acids (broader termed polyoxometalates) is a rapidly developingfield interconnected with many disciplines [1-3]. As catalysts, heteropoly acids (HPA) haveseveral advantages, with multifunctionality and structural mobility the most important [1, 2].On one hand, HPA have strong Brønsted acidity; on the other, they are efficient oxidants. Inthe last three decades, HPA have found application as acid and oxidation catalysts in severallarge-scale industrial processes such as hydration of olefins, oxidation of methacrolein tomethacrylic acid and ethylene to acetic acid [1].Solid HPA are of particular interest as heterogeneous acid catalysts for clean organicsynthesis. They are highly efficient in many practically important reactions such as Friedel-Crafts alkylation and acylation, esterification, isomerisation and many others [1-3]. As thesolid acid catalysts, HPA have several important advantages over conventional acid catalystssuch as H 3 PO 4 /SiO 2 , SiO 2 -Al 2 O 3 and zeolites [1-3]: (1) being stronger acids, HPA aregenerally more active than the conventional solid acid catalysts, (2) HPA allow efficientoperating under milder conditions, often providing a higher selectivity, with lower energyconsumption, (3) catalysis by HPA is not complicated by side reactions, such as sulfonation,chlorination and nitration, typical of mineral acids. Hence, the acid catalysis by HPA is astrong option for “greening up” chemical processes.The major problem restricting the use of solid HPA catalysts is their low thermalstability [1]. Similar to other solid acid catalysts, HPA catalysts suffer from deactivation dueto deposition of coke on their surface during operation in organic reactions, causingtemporary or permanent loss of catalytic activity. Burning coke at ca. 550 o C routinelyregenerates the conventional solid acid catalysts, zeolites for instance. However, it is notapplicable to the HPA catalysts due to their low thermal stability. Finding a solution to thisproblem is key to sustainable heterogeneous catalysis by HPA.40