Monolithic metal-fiber@HZSM-5 core-shell catalysts for methanol-to-propylene

Monolithic metal-fiber@HZSM-5 core-shell catalysts have been developed by direct growth of zeolite crystals on a macroscopic 3D network of sinter-locked metal microfibers. This approach provides a combination of excellent thermal conductivity, hierarchical porous structure from micro- to macro-size, and unique form factor. The metal-fiber@HZSM-5 catalysts, with high HZSM-5 loadings (e.g., 27-30 wt%) and excellent core-shell robustness, deliver dramatic selectivity and life-time improvement in the methanol-to-olefin process. Such unprecedented performance is due to propagation of the olefin methylation/cracking cycle over the aromatic-based cycle in the methanol-to-hydrocarbon catalysis. Using a feed of 30 vol% methanol in N₂, for example, at 480 °C high propylene selectivity of ∼46% can be obtainable with a total C₂-C₄ olefin selectivity of ∼70%, being much higher than that (∼37%, C₂-C₄ olefin selectivity of ∼64%) for the corresponding zeolite powder. The core-shell catalyst is stable at least for 210 h, almost 3-fold longer than the life-time of 60 h for the powdered HZSM-5 catalysts, because the coking rate is obviously suppressed in association with the propagated olefin-based cycle.