Recent advance in synthesis and application of heteroatom zeolites

Incorporation of heteroatoms into the framewo rk of zeolites has become a significant strategy to improve their performance in catalysis and adsorption,because the obtained heteroatom zeolites exhibit quite different properties from the conventional aluminosilicate zeolites in aspects of surface acidity,pore structures,particle size and so on.In this review,the progress on the heteroatom zeolites including their synthesis and application is highlighted.First,the recent advance on the design and synthesis of different heteroatom zeolites is summarized.Special emphasis is placed on the introduction and comparison of three typical methods,including the direct synthesis,post synthesis and improved direct synthesis,for the traditional heteroatom zeolites(such as TS-1,Sn-MFI,Sn-β) and newly-reported heteroatom zeolites(such as W-MFI,Mo-MFI).According to their intrinsic characteristics,the application of heteroatom zeolites in diverse fields,such as production of fine chemicals,air pollution control and biomass conversion is then discussed.Finally,the challenges and perspective on the future development of heteroatom zeolites in low-cost preparation and practical application are proposed.

Sulfonic acid-functionalized core-shell Fe_(3)O_(4)@carbon microspheres as magnetically recyclable solid acid catalysts

Green and recyclable solid acid catalysts are in urgent demand as a substitute for conventional liquid mineral acids.In this work,a series of novel sulfonic acid-functionalized core-shell Fe_(3)O_(4)@carbon microspheres(Fe_(3)O_(4)@C-SO_(3)H)have been designed and synthesized as an efficient and recyclable heterogeneous acid catalyst.For the synthesis,core-shell Fe_(3)O_(4)@RF(resorcinol-formaldehyde)microspheres with tunable shell thickness were achieved by interfacial polymerization on magnetic Fe_(3)O_(4)microspheres.After high-temperature carbonization,the microspheres were eventually treated by surface sulfonation,re sulting in Fe_(3)O_(4)@C-x-SO_(3)H(x stands for carbonization temperature)microspheres with abundant surface SO_(3)H groups.The obtained microspheres possess uniform core-shell structure,partially-graphitized carbon skeletons,superparamagnetic property,high magnetization saturation value of 10.6 emu/g,and rich SO_(3)H groups.The surface acid amounts can be adju sted in the range of 0.59-1.04 mmol/g via sulfonation treatment of carbon shells with different graphitization degrees.The magnetic Fe_(3)O_(4)@C-x-SO_(3)H microspheres were utilized as a solid acid catalyst for the acetalization reaction between benzaldehyde and ethylene glycol,demonstrating high selectivity(97%)to benzaldehyde ethylene glycol acetal.More importantly,by applying an external magnetic field,the catalysts can be easily separated from the heterogeneous reaction solutions,which later show well preserved catalytic activity even after 9 cycles,revealing good recyclability and high stability.