Epoxidation of olefins with hydrogen peroxide catalyzed by a reusable lacunary-type phosphotungstate catalyst

Abstract

Olefins and allylic alcohols have been epoxidized with commercially available hydrogen peroxide (30% H 2 O 2 ) using a phase transfer catalyst, composed of cetyltrimethylammonium cations and a lacunary-type phosphotungstate anion [PW 11 O 39 ] 7 or the complete Keggin-type heteropolyanion [PW 12 O 40 ] 3 , under two-phase conditions using ethyl acetate as the solvent. It was found that the lacunary-type catalyst showed higher activity and better recyclability than the complete Keggin-type catalyst under the same reaction conditions. 31 P NMR spectroscopy and solubility measurements for the two catalysts revealed that the [PW 11 O 39 ] 7 anion had a much faster degradation rate than the [PW 12 O 40 ] 3 anion in an excess of H 2 O 2 , which resulted in the formation of more catalytically active species. As a result, the lacunary-type phosphotungstate anion-based catalyst gave a better catalytic performance than the complete Keggin-type anion in ethyl acetate.heteropolyphosphotungstate, lacunary, epoxidation, degradation rate

Immobilization of polyoxometalate-based ionic liquid on carboxymethyl cellulose for epoxidation of olefins

“…In our previous work, we have demonstrated that lacunary-type phosphotungstate could be degraded to {PO 4 [WO(O 2 ) 2 ] 4 } 3À by aqueous hydrogen peroxide in the epoxidation reaction and could recover the original structure after the reaction in the presence of excess substrate. 26 In this work, the degraded species might be stabilized by the functionalized cation in the presence of a slight excess of H 2 O 2 .…”

“…The lacunary-type phosphotungstate anion [PW 11 O 39 ] 7À was proved to be an efficient catalyst precursor for the epoxidation of olefins in our previous work. 26 Herein, the coupling of [PW 11 O 39 ] 7À anion with PEG-functionalized ammonium cation resulted in a functionalized IL (PEG-PW 11 ), which was shown to have excellent catalytic activity in the epoxidation reaction even at a molar ratio of the substrate to catalyst of nearly 500 : 1 (Fig. 3).…”

Preparation of α-MoO3 from H3PMo12O40 precursor: synthesis of 1,2-cyclohexanediol from cyclohexene over α-MoO3-TiO2 catalyst

“…Indeed, in the 350 °C-450 °C range, the HPMo is gradually transformed but it still exists. Like all heteropolyanions, HPMo is a superacid with a very strong oxidizing power [40,41]. So the presence of HPMo leads to further oxidation, i.e.…”

Kinetic Studies and Reaction Network in the Epoxidation of Styrene Catalyzed by the Temperature-Controlled Phase-Transfer Catalyst [(C18H37)2(CH3)2N]7[PW11O39]

“…The reusability of the catalyst could be realized by decreasing the temperature after the reaction, making the recovery of the catalyst easier. Hua et al studied a reusable phosphotungstate catalyst composed of cetyltrimethylammonium cations and [PW 11 O 39 ] 7– ; 51.8% H 2 O 2 conversion and 73% product selectivity could be achieved, and they found that benzaldehyde was the main byproduct. Similarly, Zhao et al developed a phase-transfer catalyst for the epoxidation of olefins.…”