Enhanced coke resistance in methanol to olefins reaction via surplus mesoporosity of fibrous silica-wrapped SAPO-34

Growing concerns regarding the depletion of petroleum reserves and energy demand necessitate the exploration of alternative methods, such as methanol-to-olefin (MTO), to generate light olefins from non-crude oil sources. However, the industrial application of this method is limited due to the rapid deactivation of the catalyst, which is caused by the microporosity of the commercial catalyst. Here, we synthesized the fibrous silica-wrapped silico-alumino-phosphate (FSAPO-34) using a microemulsion technique with a seed-assisted synthesis method and applied it for the first time in the MTO reaction. The physicochemical properties of the fresh and spent catalysts were characterized by X-ray diffractometer, Fourier transform infrared spectroscopy-potassium bromide, N ₂ physisorption, field emission scanning electron microscopy, transmission electron microscopy, NH ₃ temperature-programmed desorption, thermal gravimetric analysis, O ₂ temperature-programmed oxidation, and Raman spectroscopy. The findings indicated that the formation of fibrous silica on the surface of SAPO-34 exhibited a unique spherical morphology with dendrimeric silica fiber, significantly enhancing the mesoporosity from 0.098 to 1.749 cm³/g compared to commercial microporous SAPO-34. FSAPO-34 demonstrates a significant improvement in catalytic lifetime, with a 54% increase, from 19.2 hours to 29.5 hours, compared to commercial SAPO-34. This enhanced stability is attributed to the introduction of mesoporosity in FSAPO-34, which, in turn, provides high accessibility and reduced diffusion resistance of products and ultimately retarded the formation of coke.