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

Abstract

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., 27–30wt%) 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 30vol% 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 210h, almost 3-fold longer than the life-time of 60h for the powdered HZSM-5 catalysts, because the coking rate is obviously suppressed in association with the propagated olefin-based cycle.