Silicalite-1 Shell Synthesized onto Cylinder-Shaped ZSM-5 Extrudate for Disproportionation of Toluene into Para-Xylene

Abstract

The cylinder-shaped ZSM-5 extrudate with a diameter 2 mm and a length 4-5 mm was coated with a silicalite-1 shell at its external surface by a hydrothermal synthesis with TEOS (tetraethylorthosilicate) as a silica source and TPAOH (tetrapropylammonium hydroxide) as a structure-directing agent. Catalytic performance of the obtained core/shell zeolite composite was measured in disproportionation of toluene using a pressured fixed-bed reactor. Ratios of H 2 O/SiO 2 and TPAOH/SiO 2 , crystallization time and temperature, and synthesis cycles were adjusted to get optimal synthesis conditions, at which the selectivity to para-xylene is enhanced from the thermodynamic equilibrium value 24% to nearly 80%. SEM and XRD results further confirm the formation of the ZSM-5/ silicalite-1 core/shell structure, which is responsible for the evident shape-selective production of para-xylene.

Hierarchy concepts: classification and preparation strategies for zeolite containing materials with hierarchical porosity

“…189 Such an effect for instance was found for a silicalite-1/ZSM-5 core-shell material catalysing the selective synthesis of p-xylene from toluene. 190,191 Various combinations of zeolite structures were reported to form such zeolite-core/ zeolite-shell materials, such as beta/ZSM-5, 192,193 …”

“…189 Such an effect for instance was found for a silicalite-1/ZSM-5 core-shell material catalysing the selective synthesis of p-xylene from toluene. 190,191 Various combinations of zeolite structures were reported to form such zeolite-core/ zeolite-shell materials, such as beta/ZSM-5, 192,193 beta/Y, 194 ZSM-5/silicalite-1, 191,193 Zeolites are industrially important materials in various adsorption, separation and catalytic processes. However, conventional zeolite materials face some limitations, e.g.…”

Controllable fabrication of uniform core–shell structured zeolite@SBA-15 composites

“…[7][8][9][11][12][13][14] On the other hand, among these hierarchical pores, crystalline zeolites with different pore arrangements on the cores and shells have also been of increasing concern for their benefits in catalysis and separation. 10,[15][16][17] For examples, core-shell composites b-zeolite@Silicalite-1 and ZSM-5@Silicalite-1 were synthesized and showed remarkable applications in separation, storage, controlled release and catalysis. 10,16,17 Furthermore, Yoon and co-workers first synthesized Silicalite-1@mesoporous silica with core-shell structure by using octadecyltrimethoxysilane (C 18 -TMS) as a template and partial silica source.…”

“…10,[15][16][17] For examples, core-shell composites b-zeolite@Silicalite-1 and ZSM-5@Silicalite-1 were synthesized and showed remarkable applications in separation, storage, controlled release and catalysis. 10,16,17 Furthermore, Yoon and co-workers first synthesized Silicalite-1@mesoporous silica with core-shell structure by using octadecyltrimethoxysilane (C 18 -TMS) as a template and partial silica source. 15 However, the mesopores were not uniform, showing disordered wormlike Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials and Laboratory of Advanced Materials, Fudan University, Shanghai, 200433, P. R. China.…”

Creating and mastering nano-objects to design advanced catalytic materials

“…The fast conversion of methanol also reduces side reactions of dehydration to alkane or alkene. The concept of core/shell zeolite composite to improve the catalytic performance have been further applied by various other authors recently, for example to prepare improved catalysts for toluene disproportionation by making a silicalite shell over ZSM-5 extrudate [121] or for n-octane catalytic cracking by preparing core-shell Y/Beta composite [122].…”