Synthesis of tetraruthenium (IV)-substituted tungstogermanate and catalytic oxidation of n-tetradecane under mild solvent-free conditions

Abstract

The oxidation of alkanes is important in the chemical industry. However, green chemical processes in the oxidation reaction of alkanes have developed slowly. Most oxidation reactions of alkanes still rely on sacrificial oxidants, solvents and additives, as well as high temperature and pressure. Hence, the key to make alkane oxidation occur under the mild condition is to find a catalyst with high activity. Here, we prepared a new heterogeneous catalyst used for n-tetradecane oxidation by loading tetraruthenium (IV)-substituted tungstogermanate polyanion [{Ru4O4(OH)2(H2O)4} (γ-GeW10O36)2]10- (GeW10Ru2) on 3-aminopropyltriethoxysilane (Apts)-modified SBA-15. The characterization of this heterogeneous catalyst consists of XRD, N2-adsorption measurements, Raman and FT-IR spectroscopy. In the process of catalytic oxidation of n-tetradecane, air was used as the oxidant to replace sacrificial oxidant without adding any solvents and additives under normal atmospheric pressure and low temperature. As a green catalyst, this heterogeneous catalyst has high-efficiency, good-stability and re-usability. Ultimately, this system proved to be an efficient and green catalytic process through a series of experiments. The turnover frequency (TOF) for n-tetradecane is over 29,000 h−1 under the optimum experimental conditions.