Synthesis, Characterization, and Catalytic Performance of Cr-Incorporated Aluminoborate Octahedral Molecular Sieves

A series of Cr-incorporated PKU-1 molecular sieves (Cr-PKU-1) were synthesized by using boric acid as a flux, and the physicochemical properties were characterized by XRD, ICP, SEM, XPS, UV-vis, and NH3-TPD methods. The morphology of Cr-PKU-1 is a needlelike hexagonal prism with uniform size of about 2 microm in diameter and 20-50 microm in length. XRD and UV-vis provide direct evidence that Cr ions have been successfully incorporated into the framework of PKU-1. NH3-TPD shows a dramatic increase of acidic sites in the Cr-PKU-1 in comparison with PKU-1, indicating that the Cr incorporation can significantly modify the acidity of the compound. In addition, the incorporated Cr ions may act as redox centers, thus catalytic performance of Cr-PKU-1 molecular sieve was investigated by the selective oxidation of styrene under mild reaction conditions.