Single-site catalysts and cleaner production processes, the case of TS-1

Abstract

The synthesis of Titanium Silicalite-1 (TS-1) made possible the development of new oxidation processes, environmentally clean and economically convenient. First industrial application, in 1986, was the hydroxylation of phenol to hydroquinone and catechol (10,000 t/a). In 2003, the production of cyclohexanone oxime became operative within an integrated process for the manufacture of ∈-caprolactam by an entirely new technology (60,000 t/a). The overall process is salt-free and with minimal gaseous emissions. In 2006, the construction of a 300,000 t/a plant for propylene oxide started in Belgium and others have been planned in the world. All three processes utilize hydrogen peroxide produced by the conventional anthraquinone process. Parallel to this, however, an intense research is in progress on the direct synthesis of the oxidant from the elements, to simplify the process and reduce the H₂O₂ production costs. Other means to achieve the same objectives are process integration, in the short term, andin situ generation, in the longer one. TS-1, on the other hand, will likely remain unrivalled catalyst for many years to come. The metal substituted zeolites, that in last two decades have been prepared in a large number, are catalytically inferior and inadequate to possible industrial applications.

Riassunto

Catalizzatori con siti attivi isolati per processi di ossidazione puliti, il caso della TS-1. La scoperta della Titanio Silicolite-1 (TS-1) ha reso possibile lo sviluppo e la realizzazione di nuovi processi di ossidazione compatibili con l'ambiente ed economicamente validi: l'idrossilazione del fenolo a idrochinone e cotecolo (1986; 10,0000 t/a), l'ammossimazione del cicloesanone a cicloesanonossima (2003; ca. 60,000 t/a), l'epossidazione del propilene (2006; 300,000 t/a). L'acqua ossigenata utilizzata come ossidante è ottenuta con il processo antrachinone. Iniziative dirette alla riduzione dei costi complessivi si basano sull'integrazione dei processi e l'ottenimento dell'acqua ossigenata per sintesi diretta dagli elementi. Dalle altre zeoliti contenenti un metallo relax in struttura nessuna possiede proprietà catalitiche utili, paragonabili a quelle della TS-1.