Fei Wang,Xin Wang,Zhixing Li,Jinghong Ma,Weijiong Dai,Jiajun Zheng,Ruifeng Li
A novel zeolite-modified alumina-bead catalyst (ZSM-5/Al 2 O 3 -b) was prepared via calcining zeolite-coated alumina-bead material (Al 2 O 3 -b@ZSM-5) to graft zeolitic acid sites on the alumina-bead surface. The acid catalyst proved high activity and more 8 times catalytic efficiency than the corresponding ZSM-5(5 %) + Al 2 O 3 mechanically mixed catalyst for cracking of 1, 3, 5-triisopropylbenzene (TIPB) in the FCC simulation reactor with short contact time. The characterization results showed that the surface property of the alumina-beads has been modified and the interface connection of Si-O-Al bonds between zeolitic nanoparticles and alumina resulted in stable zeolite particles on the alumina surface and the structural stability in hot water. The excellent catalytic performances are ascribed to the decrease of diffusion limitation of reactants and intermediates and the increase of Brønsted acid sites on the ZSM-5/Al 2 O 3 -b catalyst. The grafted/modified alumina-bead catalyst can be directly used in practical catalytic cracking of large molecules without forming. This strategy can be extended to the preparation of other types of zeolite-containing catalysts and industrial applications.
Jia-Min Lyu,Shen Yu,Zhao Peng,Jian Zhou,Zhan Liu,Xiao-Yun Li,Yu-Li,Li-Hua Chen,Bao-Lian Su
Bifunctional catalysts are widely applied for many important reactions as the synergetic effect of two types of active sites remarkably improves catalysis performance. However, their bifunctionality has not been fully exploited since the proximity of bifunctional catalysts is hard to control. Herein, we demonstrate a bifunctional ZSM-5@Al 2 O 3 catalyst with a core-shell structure and a nano-scale proximity by in-situ growth of γ-Al 2 O 3 nanosheets on the surface of ZSM-5 crystals for methanol conversion. The nano-scale proximity endows the catalyst with higher reaction activity and C 2 –C 3 olefins yield (53 %) in comparison to the catalysts with micro-scale proximity (20 %) and millimeter-scale proximity (27 %), which can be attributed to the fluent transport of the reaction intermediates between two types of active sites. This strategy for constructing bifunctional catalysts with nano-scale proximity is conducive to understanding the relationship between proximity and catalytic performance in methanol conversion.
Upcycling plastic waste into valuable resources without solvents, precious metals, or additional H 2 under mild conditions is a formidable challenge that requires new innovations. Herein, we document a catalyst based on Al 2 O 3 beads and zeolite ZSM-5 (ZSM-5#Al 2 O 3 (2 h)). It cracked polyethylene (PE) into gasoline-range C 4 − C 12 hydrocarbons with a selectivity of 98% and a yield of >71% within 1.5 h at 260 °C. Characterization of the catalysts revealed a mesoporous structure and suitable Brønsted acid sites, which promoted the diffusion and catalytic activation of PE. Adjusting the dosage of zeolite supported on Al 2 O 3 beads enables regulation of both the number and strength of acidic sites. Theoretical calculations confirmed that the interfacial interaction between zeolite ZSM-5 and Al 2 O 3 reduces the acid strength of the composite. This is beneficial for the formation of higher hydrocarbons. Remarkably, the process was performed in a 1 L CSTR unit. These results provide instructive guidance for the design of high-performance catalytic materials used in PE waste recycling. The alternative text for this image may have been generated using AI.
危险品化学品经营许可证（带存储）