Direct conversion of syngas to aromatics has great potential to decrease fossil fuel dependence. Here, a unique structured hybrid catalyst composed of Fe 3 O 4 nanoparticles intimately dispersed inside an acidic zeolite is developed. 1 to 4 nm sized Fe 3 O 4 nanoparticles end up evenly dispersed in an acidic and slightly mesoporous Al-ZSM-5 based on Fe 3 O 4 restructuring during co-hydrothermal synthesis using organosilane modification. A very high aromatic productivity of 214 mmol aromatics h −1 g Fe −1 can be obtained with a remarkable 62% aromatic selectivity in hydrocarbons. This catalyst has excellent sintering resistance ability and maintains stable aromatics production over 570 h. The synthetic insights that postulate a mechanism for the metastable oxide-zeolite reorganization during hydrothermal synthesis could serve as a generic route to sinter-resistant oxide-zeolite composite materials with uniform, well-dispersed oxide nanoparticles in close intimacy with - and partially confined in - a zeolite matrix.
Xuyang Zou,Jiangzhang Wang,Guojun Lv,Tao Wang,Chaoyi Zhou,Yan Chen,Jialing Shen,Shihao Su,Zhongmin Liu
Impregnation handlement can load highly dispersed CuO nanoparticles on the Fe-MFI zeolite and effectively enhances its catalytic activity in the tetracycline degradation reactions, but encounters serious re-usability problems. In this work, Fe-MFI zeolite-encapsulated copper oxide CuO@Fe-MFI was prepared via one-step hydrothermal synthesis and utilized as heterogeneous catalyst for the removal of tetracycline. The obtained 2CuO@1Fe-MFI zeolite presented a external surface area of 270 m 2 /g, which was almost 5.5 folds of 2CuO/1Fe-MFI zeolite obtained by impregnation handlement. In addition, there may be a near-neighbor effect between encapsulated CuO and framework iron evidenced by the shifts of UV–Vis absorption bands as well as binding energies for Fe 2p and Cu 2p. At pH = 7.0, 2CuO@1Fe-MFI zeolite attained the largest tetracycline removal rate of 99.6% within 20 min at experimental conditions: [TCE] = 50 mg/L, [Catalyst] = 0.5 g/L, [PMS] = 1.0 g/L, 323 K, and the biggest degradation rate constant of 2.42 min −1 , which was almost 11.1 folds of that for 2CuO/1Fe-MFI zeolite. The large external surface area and near-neighbor effect together gave rise to the excellent tetracycline degradation performance for 2CuO@1Fe-MFI zeolite. On the same time, the obtained 2CuO@1Fe-MFI zeolite can be reused for more than five times. Quenching experiments and EPR characterizations demonstrated the reactive species for tetracycline removal over 2CuO@1Fe-MFI zeolite were •OH, SO 4 • − , •O 2 − and 1 O 2 species, and moreover 1 O 2 served as the major active species. Furthermore, possible tetracycline degradation pathways over 2CuO@1Fe-MFI zeolite were proposed.
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