Selective direct oxidation of 1‐butanol into acetal using hydrogen peroxide and Cs5MPW11(H2O)O39 (M=Fe, Co, Cu) catalysts

Catalytic oxidation of 1-butanol over lacunary POM salts modified by transition metals in the presence of H₂O₂ as oxidizing agent enables selective production of the acetal 1,1-dibutoxybutane with yield approaching 92 % for the catalyst Cs₅CuPW₁₁(H₂O)O₃₉, such activity is related to a bifunctional behavior of the catalyst as superacid and redox operating system. This one-step process avoids the formation of unstable by-products.

Abstract

Direct catalytic oxidation of alcohols to acetals in one step process is very attractive, because the two steps process leads firstly to aldehydes, which are unstable species serving as reactive intermediates to generate several by-products reducing process efficiency and selectivity. In this work, a new selective catalytic acetalization of 1-butanol into 1-1-dibutoxybutane acetal using H₂O₂ in one step process is investigated using Keggin-type polyoxometalates catalysts. The materials developed consisted of new lacunary phophotungstate salts Cs₅MPW₁₁(H₂O)O₃₉ (M=Fe, Co and Cu) which were prepared by inorganic solution condensation method and characterized using XRD, IR, SEM and EDX analysis to verify their structure, surface morphology and chemical composition. Cs₅CuPW₁₁(H₂O)O₃₉ catalyst allowed the highest performance for the oxidation of 1-butanol at 60 °C using H₂O₂ excess with a yield approaching 92 % and a turnover number of 784. Such activity is related to a bifunctional behavior of the catalyst as superacid and redox operating system and the synergistic effect created between the [PW₁₁O₃₉]⁷⁻ Keggin framework, Cs⁺ and Cu²⁺.

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