Microfibrous-Structured SS-fiber@meso-HZSM-5 Catalyst for Methanol-to-Propylene: Steam-Assisted Crystallization Synthesis and Insight into the Stability Enhancement

Free-standing stainless-steel (SS)-fiber@meso-HZSM-5 core-shell catalysts engineered from micro-to macro-scale were highly efficiently synthesized via cost-effective steam-assisted crystallization (SAC) method. Impact of synthesis conditions on their morphology and textural/acidic properties was investigated by means of XRD, SEM, TEM, solid-state NMR, NH3-TPD, Py-IR and N-2 physisorption. 80 Single-run lifetime of such structured catalysts for MTP process was strongly dependent on their preparation conditions but slightly the product distribution. A volcano-like relationship for lifetime was observed against the SAC time, which was correlated well with the crystallization-time-dependent crystallinity, mesoporosity and crystal size. The promising SS-fiber@meso-HZSM-5 was the one obtained after the SAC for 12 h, which delivered a prolonged single-run lifetime of 620 h with a high propylene selectivity of similar to 42% at 450 degrees C using a methanol weight hourly space velocity (WHSV) of 1 h(-1), as the result of high crystallinity, well-developed mesoporosity and small crystal size. Note that well-developed mesoporosity was paramount for the catalyst stability improvement, because of enhanced accommodation capacity of zeolite shell for receiving formed coke.