Nanoporous ZSM-5 Crystals Coated with Silicalite-1 for Enhanced p-Xylene Separation

Abstract

The growth of a silicalite-1 coating on ZSM-5 zeolite crystals is one of the surface modification methods allowing to improve its catalytic p-xylene selectivity. Aiming to understand this increase in p-xylene selectivity, the effect of silicalite-1 coating on the adsorptive properties of ZSM-5 was investigated. Pulse chromatographic experiments revealed the silicalite-1 coating improved the separation factors of p-xylene over o-xylene and m-xylene, resulting in a better chromatographic separation of p-xylene over m-xylene on silicalite/ZSM-5 compared to that on parent ZSM-5. Additionally, slower adsorption kinetics of mxylene on silicalite/ZSM-5 compared to ZSM-5 was also confirmed by gravimetric adsorption measurements. It is concluded that the enhanced p-xylene selectivity is achieved by steric effects leading to a more pronounced exclusion of m-xylene in the outer silicalite-1 layer and a reduction in number of surface adsorption sites.

Optimizing the Acid Properties of the HZSM-5 Catalyst for Increasing the p-Xylene Yield in 1-Hexene Aromatization

“…But the proportions of the content of A9 and A10+ showed the opposite trend. Considering that the pore size of HZSM-5 (0.53 × 0.56 and 0.51 × 0.55 nm) was similar to the kinetic diameter of A8 (around 0.58 nm), , it was speculated that increasing the L/B could better utilize the pore selectivity of HZSM-5 without seriously affecting the catalyst pore size. However, when the loading content of Zn was too high (above 3 wt %), the pore size was reduced and the pore channel was blocked.…”

Cooperative External Acidity and Surface Barriers of HZSM-5 in the Coupling Reaction of CH3Cl and CO to Aromatics

“…The improvement in BTX selectivity demonstrated that the secondary reaction of products was inhibited due to the surface modification of ZSM-5, which was consistent with the previous studies. 32 Furthermore, the catalyst stability of the modified samples was studied, as shown in Figure 5b. Not all the modified samples have improved the catalyst stability, following ZSM-5-M1 > ZSM-5-P > ZSM-5-M2 > ZSM-5-M3, which was inconsistent with the previous studies on the external acidity.…”

Hierarchical Nanospherical ZSM-5 Nanosheets with Uniform Al Distribution for Alkylation of Benzene with Ethanol

“…In addition, the zeolite framework can be decorated by various elements with the valency ranging from I to V including B, K, Sn, and Ga, as well as transition metals such as Ce, Fe, Mn, Co, Zn, and Cu. , Therefore, these materials can be synthesized with favorable properties, for instance, desirable porous structures, the appropriate Si/Al ratio, and a suitable cation type. Because of the advantageous characteristics of zeolites, including less toxicity, large surface area, molecular shape selectivity and adsorption capacity for guest molecules, and good thermal and chemical stabilities, they have been utilized in many potential applications, for example, ion-exchange, adsorption, separation, , and especially catalysis. , …”

“…1,2 Therefore, these materials can be synthesized with favorable properties, for instance, desirable porous structures, the appropriate Si/Al ratio, and a suitable cation type. Because of the advantageous characteristics of zeolites, including less toxicity, large surface area, molecular shape selectivity and adsorption capacity for guest molecules, and good thermal and chemical stabilities, 3 they have been utilized in many potential applications, for example, ion-exchange, 4 adsorption, 5 separation, 6,7 and especially catalysis. 8,9 To date, zeolites have been extensively used as heterogeneous catalysts in the refinery and petrochemical processes because of their superior properties involving the shapeselective properties and the suitable acidity.…”