Selective Formation of Para-Xylene by Methanol Aromatization over Phosphorous Modified ZSM-5 Zeolites

Xianjun Niu,Mei Dong,Yang Bai,Yi-en Du,Kai Wang,Yongqiang Chen,Weibin Fan

doi:10.3390/catal10050484

Abstract

Phosphorous modified ZSM-5 zeolites were synthesized by incipient wetness impregnation. Their performances for the methanol to aromatics conversion (MTA) were subsequently evaluated and the relationship between the catalyst structure and performance was focused on. The obtained results indicated that the introduction of phosphorous resulted in the modification of the catalyst structure characteristics and acidic properties, i.e., the reduction in the external surface area and micropore volume, the narrowing of the pore size, and the decrease in the quantity and strength of acid sites. As a result, the P/HZSM-5 catalyst exhibited the enhanced selectivity for the para-xylene (PX) in xylene isomers and xylene in aromatics, and their increase degrees were intensified with the increasing P content. The selectivity of PX in X increased from 23.8% to nearly 90% when P content was 5 wt.%. Meanwhile, the selectivity of xylene in aromatics was enhanced from 41.3% to 60.2%.

Highlights

Para-xylene (PX) is of great value since it is useful in manufacturing terephthalic acid, which is an intermediate in the manufacture of synthetic fibers
The results indicated that the introduction of P did not destroy the structure of ZSM-5 framework severely and P was highly dispersed in ZSM-5 zeolite
The results indicated that the introduction of P could reduce micropore volume and external surface area, narrow the pore size and decrease the amount and strength of strong acid sites

Summary

Introduction

Para-xylene (PX) is of great value since it is useful in manufacturing terephthalic acid, which is an intermediate in the manufacture of synthetic fibers. The catalytic process for producing PX has been paid much attention and become a quite competitive subject in the petrochemical industry [1,2]. The reactions of toluene disproportionation [3,4], transalkylation of benzene with trimethylbenzene [5,6]. Toluene methylation [7,8,9] were used to produce PX. The conversion of methanol to hydrocarbons over acidic zeolite catalysts is considered an important and feasible non-petroleum route to obtain valuable chemicals [10,11,12,13,14,15,16,17,18]. It is a significative work to design a shape selectivity catalyst for high

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Results

Conclusion