ARTICLE IN PRESS JID: JTICE [m5G;June 8, 2017;15:24] Journal of the Taiwan Institute of Chemical Engineers 000 (2017) 1–9 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice Bifunctional Pt/Fe-ZSM-5 catalyst for xylene isomerization Milad Rasouli a , Hossein Atashi a,∗ , Davod Mohebbi-Kalhori a , Nakisa Yaghobi b a Department of Chemical Engineering, Faculty of Engineering, University of Sistan and Baluchestan, Zahedan, Iran b Department of Petrochemical, Iran Polymer and Petrochemical Institute, Tehran, Iran a r t i c l e i n f o Article history: Received 6 April 2017 Revised 17 May 2017 Accepted 17 May 2017 Available online xxx Keywords: ZSM-5 zeolite Xylene isomerization EB conversion Xylene loss Pt impregnation a b s t r a c t The addition of iron to the synthesis of ZSM-5 catalysts (Si/Al = 21) was studied in xylene isomerization reactions. Pt impregnation was conducted by partial vacuum impregnation on both the parent and Fe- ZSM-5. XRD, FE-SEM, ICP, BET, XPS, FT-IR, NH 3 -TPD, and TG analysis have been used to characterize the catalysts. Fe incorporation strongly decreased the weak acid sites and slightly reduced the strong acid sites. Reducing weak acidity led to lower coke formation and more catalytic stability in Fe-containing ZSM-5 catalysts. The presence of Pt on the Fe-supported ZSM-5 illustrated simultaneous high PX yield and high catalyst stability. (0.1 wt%)Pt/(0.4 wt%)Fe-ZSM-5 as an efficient and stable catalyst for xylene isomerization reactions demonstrated high PX yield (25.4 wt%), high EB conversion (61%) and low xylene loss (1.8%). © 2017 Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers. 1. Introduction Mixed xylenes are produced through catalytic reforming of naphtha, from which the C8 aromatics includes the thermody- namic equilibrium distribution of 24% para-xylene (PX), 46% meta- xylene (MX), 20% ortho-xylene (OX) and 10% ethylbenzene (EB). Xylenes can also achieve from the pyrolysis gasoline stream in a naphtha steam cracker and through toluene disproportionation process. PX as a most desirable product is applied in the production of polyethylene terephthalate (PET), which is used as a polyester fiber, film and resin for a several applications [1]. In order to meet downstream demand, PX production has seen several year-to-year enhancements in the range of 6–8% per year. Separation of PX from C8 aromatics can be carried out through the crystallization or by the adsorption over zeolite adsorbents, the remaining mixture be- ing processed into an isomerization unit in order to achieve more PX as a valuable product [2–6]. Xylene isomerization is a commendable reaction of acid catal- ysis that is generally used as a model reaction for acidity adjust- ment [7–10] and bifunctional catalysts have to be applied to se- lective transformation of EB to valuable products [11–13]. Zeolites are well known for xylene isomerization reactions due to their large surface area, pore volume, acidity and appropriate hydrother- mal and chemical stabilities [14]. Xylene isomerization is currently ∗ Corresponding author. E-mail addresses: h.ateshy@hamoon.usb.ac.ir, usb.hossein.atashi@gmail.com (H. Atashi). accompanied by side reactions such as dealkylation and dispropor- tionation reactions which lower the catalyst selectivity and lead to creating C 6 , C 7 , C 9 and C 10 aromatics. Therefore reducing these un- desirable reactions will affect the final production rate and eco- nomics of the plant [15]. Wichterlova et al. [16] synthesized bimetallic HZSM-5 cata- lyst (Si/Al = 13.6) ion-exchanged with various Ni salts such as: Ni (CH 3 COO) 2 , NiCl 2 , NiSO 4 and NiO. Ion-exchange of ZSM-5 with NiCl 2 led to decrease of strong acid skeletal OH groups and uni- form dispersion of metallic Ni (0.102 mmol Ni/g zeolite) into the zeolite cationic sites which is active for xylene isomerization re- action. Isomerization and dealkylation activity of NiCl 2 exchanged ZSM-5 catalyst was obtained to be considerable to that of the par- ent ZSM-5 zeolite. Rane and coworkers [17] found that addition of 10% HZSM-5 to ZSM-35 catalyst increases EB conversion more than 20% and showed much more catalytic stability and PX selectivity than the pure ZSM-35. Isomerization of xylene over MgO and CaO modified ZSM-5 zeolite was studied by Li and Jun [18]. The molar ratio of MgO and CaO to framework aluminum was equal to 1:1. Results illustrated the strong dependency of MX and OX conver- sion on zeolite acidity, whereas isomerization of PX can occur in both strong and weak acid sites. Guisnet et al. [19] reported that xylene isomerization reaction can accomplish through intramolec- ular and/or intermolecular mechanisms which involve methyl shift in benzenium-ion intermediates as well as disproportionation and transalkylation of trimethylbenzenes and xylene molecules, respec- tively. Bauer et al. [20] modified ZSM-5 catalyst by coking and silica deposition to inactivate the external surface of the zeo- lite which led to improving PX yield. Akpolat and Gunduz [21] http://dx.doi.org/10.1016/j.jtice.2017.05.018 1876-1070/© 2017 Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers. Please cite this article as: M. Rasouli et al., Bifunctional Pt/Fe-ZSM-5 catalyst for xylene isomerization, Journal of the Taiwan Institute of Chemical Engineers (2017), http://dx.doi.org/10.1016/j.jtice.2017.05.018