Preparation of mesoporous MCM-41 from natural sepiolite and its catalytic activity of cracking waste polystyrene plastics

Mesoporous MCM-41 was prepared by leaching of sepiolite and sequent hydrothermal synthesis in NaOH solution with hexadecyltrimethylammonium bromide as template. Small-angle X-ray diffraction patterns, Scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller were performed to characterize the resulting compounds. The results showed that the crystallinity and pore size of MCM-41 increased with increase of crystallization time, ratios of surfactant to SiO2 and decrease of Mg content. The experimental results of catalytic cracking of polystyrene waste showed that the MCM-41 with MgO from natural sepiolite had high catalytic activity and good selectivity to monomer styrene for the catalytic cracking of polystyrene when the ratio of waste plastics to MCM-41 was 200. The side reactions yielded ethylbenzene, isopropylbenzene, isopropenylbenzene and secondary cross-linking were suppressed by basic species MgO in MCM-41.

The fibrous sepiolite was extracted Mg2 + ions to give rise to short silica fibers through ion-exchange with H+ and then rearranged to form mesostructural MCM-41 through liquid crystal templating mechanism. MCM-41 from sepiolite has high activity and good selectivity to styrene for catalytic cracking of waste polystyrene plastics with the plastics/catalyst ratio of 200.Figure optionsDownload as PowerPoint slideHighlights
► The process of hydrothermal synthesis of MCM-41 from natural sepiolite was studied.
► The rearrangement mechanism of fibrous silica was established to form MCM-41.
► The effects of MgO on catalytic performance of MCM-41 were investigated.
► Catalyst from sepiolite has high performance for cracking of waste PS plastics.