Controllable fabrication of uniform core-shell structured zeolite@SBA-15 composites

Mesoporous core-shell composites with large-pore silica shells are highly desired for a broad spectrum of applications. We report an ultra-dilute liquid-phase coating strategy in an acidic medium for controllable synthesis of uniform micro/mesoporous core-shell composites zeolite@SBA-15 comprising zeolite cores and mesoporous silica SBA-15 shells using triblock compolymer Plunoric P123 as a template. Structural characterizations show that the core-shell composites possess tunable specific surface areas (115-228 m(2) g(-1)), large pores (similar to 7.0 nm in diameter) with plenty of mesotunnels (similar to 3.0 nm) from silica shells, original crystalline zeolite frameworks, and opened junctions between micropores and mesopores. The silica shells have ordered 2-D hexagonal mesopore channels, most of which are annularly parallel (fingerprint-like arrangement) to the anisotropic zeolite faces. The shell-thickness is crystal face-dependent, which could be facilely tuned in the range of 30-45 and 40-120 nm on a pinacoids/dome faces and b pinacoids of a zeolite single-crystal, respectively. Moreover, the synthesis parameters such as MgSO4 additive, stirring rate, acidity, temperature and reaction time show great influences on the formation of uniform core-shell composites. Post-hydrothermal treatment at 100 degrees C has been for the first time adopted to improve mesostructural regularity of the core-shell composites. A scheme regarding surface-induced micellization and hydrothermal rearrangement of mesostructured silica shells in the coating process is proposed to illustrate the formation of core-shell composites. The core-shell composite HZSM-5@SBA-15 (HZ@S15) was employed as a catalyst for methanol to propylene (MTP) conversion, and shows excellent catalytic performance with high methanol conversion (similar to 98%) and propylene to ethylene (P/E) ratio (similar to 10.7) as well as propylene selectivity (similar to 39%).