Production of Xylenes from Toluene and 1,2,4‐Trimethylbenzene over ZSM‐5 and Mordenite Catalysts in a Fluidized‐Bed Reactor

Abstract

The production of various xylenes from toluene, heavy aromatics such as 1,2,4-trimethylbenzene (1,2,4-TMB) and their mixture was investigated over H-ZSM-5 (H-Z), H-mordenite (H-M) and a dual zeolitic catalyst comprising ZSM-5 and mordenite (H-ZM). The experiments were conducted in a riser-simulator reactor under different operating conditions to study the effect of temperature, reaction time and feed composition on conversion and product yields. At 400°C, the conversion of toluene over the three catalysts yielded mainly benzene and xylenes with maximum conversion at 25 % and a xylene yield of 12.5 wt % over the H-M catalyst. The transformation of 1,2,4-TMB doubled the conversion level and xylene yield and suppressed benzene formation. However, a considerable portion of the 1,2,4-TMB feed was isomerized into 1,2,3-TMB and 1,3,5-TMB accompanied by the formation of tetramethylbenzenes (TeMBs). The conversion of an equimolar mixture of toluene and 1,2,4-TMB over the three catalysts resulted in higher toluene conversion and double xylene yield in comparison with 1,2,4-TMB alone. The advantage of using a dual zeolitic catalyst was observed at an equimolar feed of toluene and 1,2,4-TMB, exhibiting maximum toluene conversion, higher xylene yield and the formation of lower levels of undesirable products.

Diffusion of Trimethylbenzenes, Toluene, and Xylenes in UWY Zeolite as a Catalyst for Transalkylation of Trimethylbenzenes with Toluene

“…The production of xylenes through disproportionation of toluene as well as transalkylation of heavy reformates (containing >80% C9 aromatics), with or without toluene or benzene, allows refineries to increase the value of the heavy reformate 1 after the clean air act banned its use as additive to gasoline because of environmental regulations. The main applications of xylenes are in the production of synthetic fibers and plasticizers, as solvents, and for gasoline blending.…”

Effect of hydrogenative regeneration on the activity of beta and Pt-Beta zeolites during the transalkylation of toluene with 1,2,4-trimethylbenzene

“…Xylenes (p-, mand o-) have the greatest market demand with an increasing annual rate of 5-6% [1]. The availability of surplus toluene and low value of C 9 aromatics makes the transalkylation process an attractive method of making higher value aromatic compounds, principally xylenes [2][3][4]. Large-pore threedimensional zeolites were shown to be an active catalyst for the transalkylation process [5].…”

Transalkylation of Toluene with 1,2,4-Trimethylbenzene over Large Pore Zeolites

“…6 A number of commercial transalkylation processes have been developed such as the Xylene-Plus process developed by ARCO-IFP, 7 the Tatoray process developed by UOP, 8 and the TransPlus process developed by Mobil-CPC 9 with key operating parameters listed in Table 1. Research on transalkylation has been carried out using various types of zeolites, including both medium pore zeolites, such as ZSM-5, 10 NU-87, 11 and MCM-22, 12 and large pore zeolites, such as zeolite Y, 13 Beta, 14 mordenite, 15 SAPO-5, 16 and ZSM-12. 17 This research demonstrated that zeolite based catalysts have unique properties promoting their use in aromatic transformations.…”