Effects of the properties of SO4/ZrO2 solid catalysts on the products of transformation and reaction mechanism of R-(+)-limonene diepoxides

✍ Scribed by O.V. Salomatina; T.G. Kuznetsova; D.V. Korchagina; E.A. Paukshtis; E.M. Moroz; K.P. Volcho; V.A. Barkhash; N.F. Salakhutdinov

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 466 KB
• Volume: 269
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/j.molcata.2007.01.005

✦ Synopsis

Transformations of limonene diepoxides on solid SO 4 /ZrO 2 catalysts in dried methylene chloride at room temperature were investigated by varying the amounts of supported sulfate ions and zirconia polymorphs. A method for estimating acid centers from DRIFTS spectra of adsorbed pyridine on the solid catalyst in a dried methylene chloride solution has been developed. It is shown that the mechanism of diepoxide transformations is changed by varying the type and amount of acid centers. At a 0.9-3% level of sulfation, Lewis centers are mainly responsible for the initial cleavage of the 8,9-epoxy group of limonene diepoxides (route B). At higher contents of sulfate ions (up to 30 wt.% SO 4 ), the key transformations proceed with cleavage of the 1,2-epoxy group (route A) and involve the Brønsted centers. The type of support affects the structural features of the sulfate ions, which govern the rearrangement of limonene diepoxides by route A or B. Transformation of limonene diepoxides on the Lewis centers formed on sulfated alumina follows mainly route A. The type of acid centers also affects the stereochemical composition of the product mixture.