Preparation and characterization of new Ni-aluminosilicate catalysts and their performance in the epoxidation of (Z)-cyclooctene

This work reports the preparation of two series of Ni-aluminosilicates by the sol–gel and the co-precipitation methods. The main difference between the two processes of synthesis is the pH of the initial mixture, 2 for the sol–gel and 11 for the co-precipitation method, respectively. The obtained solids are heat-treated at various temperatures in the range of room temperature to 1000 °C, and the resulting materials are characterized by X-ray diffraction, thermogravimetric and differential thermal analysis, ultraviolet–visible spectroscopy, nitrogen adsorption, and transmission electron microscopy. Various nickel compounds crystallize under the sol–gel reaction conditions, as well as, amorphous silica and crystalline 2NaAlO2·3H2O. Ni–Al hydrotalcite, takovite, and amorphous silica are obtained when the samples from the co-precipitation method are analysed. A maximum of 302 m2/g of specific surface area shows the co-precipitation samples series, with only 32 m2/g in the case of the sol–gel samples series. The catalytic performance in the epoxidation of (Z)-cyclooctene at room temperature and atmospheric pressure is evaluated using aqueous hydrogen peroxide as oxidant.

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