Ionic ammonium and anilinium based polymolybdate hybrid catalysts for olefin epoxidation

• Published in: Applied catalysis. A, General General, 2018-08, Vol.564, p.13-25
• Main Authors: Bożek, Barbara, Neves, Patrícia, Łasocha, Wiesław, Valente, Anabela A.
• Format: Article
• Language: English
• Subjects: Bio-derived olefins; Catalytic epoxidation; Crystal structure; Hybrids; Polymolybdates
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2018.07.001

[Display omitted] •Ionic organo-polymolybdate hybrids (IPHs) easily synthesised under mild, aqueous phase conditions.•Type of synthetic organic precursor and synthesis conditions influence structural features and performance of IPHs.•The best-performing catalyst possessed one-dimensional structure and selectively converted bio-based olefins to epoxides.•The best-performing catalyst possessed steady activity in consecutive batch runs, with preservation of structural features. Ionic polymolybdate hybrids (IPH) are interesting catalysts for liquid phase olefin epoxidation with tert-butylhydroperoxide; (tbhp), e.g. conversion of terpenic and fatty acid methyl ester (FAME) components of biomass to useful bio-products. IPHs may be easily prepared, under clean, mild, aqueous phase conditions. The type of organic precursor and the synthesis conditions influence the structural features of the IPHs. In this work, IPH epoxidation catalysts possessing one- (1-D) or two-dimensional (2-D) structures were investigated, which included the new materials 1-D methylammonium ammonium trimolybdate [Mo3O10⋅CH3NH3·NH4] (1) and 2-D bis(2,5-dimethylanilinium) pentamolybdate [Mo5O16·2(NH3C6H3(CH3)2)] (4) with solved structures, and 1-D bis(3,5-dimethylanilinium) trimolybdate [Mo3O10·2(NH3C6H3(CH3)2)] (2), bis(4-methylanilinium) trimolybdate [Mo3O10·2(NH3C6H4CH3)] (3), 2-D bis(anilinium) pentamolybdate [Mo5O16·2(NH3C6H5)] (5), bis(4-methylanilinium) pentamolybdate [Mo5O16·2(NH3C6H4CH3)] (6) and bis(4-ethylanilinium) pentamolybdate [Mo5O16·2(NH3C6H4C2H5)] (7). Systematic characterisation and catalytic studies helped gain insights into structure-activity relationships. The best-performing catalyst (2) was effective for the epoxidation of the FAMEs such as, methyl oleate which gave 92% methyl 9,10-epoxyoctadecanoate yield, at 99% conversion, at 70 °C. The reaction conditions (temperature, type of cosolvent and oxidant) influenced the catalytic reaction. Catalytic performance in consecutive batch runs was steady, and the structural features were essentially preserved.