Encapsulating Pt clusters during the crystallization of MWW zeolite

Directly encapsulation of Pt clusters within MWW zeolite was realized by precisely regulating the synthetic parameters, especially the alkalinity and the Pt content during the hydrothermal synthesis. Simple addition of Pt(NH3)4(NO3)2 to the routine recipe for MWW synthesis resulted in a mixture of MWW to FER zeolites, while appropriately lowering the alkalinity of the initial gel composition favored the formation of pure MWW phase and simultaneously the incorporation of Pt clusters into the micropores of MWW (Pt/Na/Al2O3/H2O/HMI/SiO2 = 0.0015/0.18/0.044/15/0.34/1). At high Pt loading (Pt/SiO2>0.00225), however, the crystallinity decreased considerably and the 3D MWW structure gradually evolved into disordered layers, while Pt particles located on the surface of the disordered layers and were prone to grow into larger ones. In short, addition of Pt(NH3)4(NO3)2 in the initial gel altered the crystallization process of MWW zeolite, and Pt-MWW could be obtained by appropriately lowering the alkalinity and accurately controlling the amount of platinum.