Cobalt oxide encapsulated hydrophilic hierarchical Silicalite-1 for highly efficient conversion of cyclohexyl hydroperoxide

Abstract CHHP is the main product of the cyclohexane oxidation process, the rational design and preparation of solid catalysts are vital important for the development of an environmental benign CHHP conversion process. Herein, cobalt oxide encapsulated hydrophilic hierarchical Silicalite-1 was developed for CHHP conversion. In the presence of an organosilane, the encapsulation of cobalt oxide, creation of intracrystalline secondary porosity, and introduction of surface silanols were simultaneously achieved via hydrothermal synthesis. The particle size of the encapsulated cobalt oxide was about 4.7–6.3 nm, while the SBET, VT and VME are 527 m2/g, 0.417 cm3/g and 0.3 cm3/g, respectively. Moreover, the SBET further increases to 692 m2/g when the silanization process was intensified by surfactants, and the hydrophilic substrates could more easily be adsorbed by the catalyst for the abundant terminal silanols. Then, the dilute CHHP could selectively be adsorbed and activated by the catalyst, and a CHHP conversion of more than 99% could be achieved in 20min. More importantly, the catalyst exhibits outstanding activity in both the CHHP decomposition reactions and cyclohexane oxidation reaction with CHHP as the oxidant, the oxygen utilization efficiency (60%) and KA oil selectivity (120%) were notably improved. The stability of the catalyst is excellent, the activity retained after recycling for 20 times. This strategy is general, which could further be applied for the development of heterogeneous catalysts for more environmental benign chemical processes.