Please cite this article in press as: S. Tamiyakul, et al., Conversion of glycerol to aromatic hydrocarbons over Zn-promoted HZSM-5 catalysts, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2014.12.030 ARTICLE IN PRESS G Model CATTOD-9413; No. of Pages 11 Catalysis Today xxx (2015) xxx–xxx Contents lists available at ScienceDirect Catalysis Today j our na l ho me page: www.elsevier.com/locate/cattod Conversion of glycerol to aromatic hydrocarbons over Zn-promoted HZSM-5 catalysts Sikarin Tamiyakul a , Warayut Ubolcharoen a , Duangamol N. Tungasmita b,c , Siriporn Jongpatiwut a,c,∗ a The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand b Materials Chemistry and Catalysis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand c Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok 10330, Thailand a r t i c l e i n f o Article history: Received 23 October 2014 Received in revised form 12 December 2014 Accepted 15 December 2014 Available online xxx Keywords: Glycerol Aromatic Zinc species HZSM-5 a b s t r a c t Catalytic conversion of glycerol to BTX aromatics has been investigated over HZSM-5 and Zn-promoted HZSM-5 catalysts. The reaction pathway of glycerol to aromatics was proposed. Glycerol was first dehy- drated to three main intermediates, propenal, acetaldehyde, and acetol. The combination of oxygenate pool and olefins formed heavy aromatics in the hydrocarbon pool via oligomerization and cyclization. The disproportion and cracking of the hydrocarbon pool generated aromatics and also short alkanes. The effects of zeolite acid properties to the aromatization of glycerol were investigated over HZSM-5 with various SiO 2 /Al 2 O 3 ratios i.e. 23, 30, 50, 80, and 280. In order to improve the aromatics selectivity, the dehydrogenation metal, Zn was promoted on the HZSM-5 zeolites by both aqueous phase ion-exchange (IE) and incipient wetness impregnation (IWI) methods. XPS, EXAFS, H 2 -TPR, NH 3 –TPD and TPD-IPA (tem- perature programmed desorption of isopropylamine) were employed to investigate the active species of Zn in aromatization of glycerol. By using aqueous phase ion-exchange method, the appearance of Zn species was only in the form of bivalent Zn cations at exchange site. Due to the exchange of these species with strong Brönsted acid site, the formation of aromatics tended to increase by suppressing the hydrogen transfer reaction and formation of light paraffins. ZnO species, formed by incipient wetness impregnation method was found to be less active for the reaction. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Aromatics are in widespread used as feedstocks for numer- ous chemical industrial processes. The conventional processes, catalytic reforming of heavy naphtha and aromatization of light paraffins are the traditional routes for these aromatics produc- tion [1]. However, both processes relied on the nonrenewable resources of crude petroleum oil and coal. Due to the shortage of petroleum resources and the rising environmental concern, the use of renewable resources has gained more attention. As one of the biomass-derived oxygenated hydrocarbons, glycerol is obtained approximately 10 wt.% as by-product during the biodiesel produc- tion via transesterification reaction of vegetable oils and animal fats ∗ Corresponding author at: Chulalongkorn University, The Petroleum and Petro- chemical College, 254 Soi Chula 12, Phyathai Rd. Pathumwan, Bangkok 10330, Thailand. Tel.: +66 2 218 4139; fax: +66 2 218 4459. E-mail address: siriporn.j@chula.ac.th (S. Jongpatiwut). [2–4]. The worldwide growth of biodiesel production is leading to a continued increase in the glycerol supply and also decrease in the glycerol price. For these reasons, recent studies have investigated ways to convert glycerol to more valuable chemicals such as 1- hydroxyacetone [5], formaldehyde [6], fuel additives [7], acrolein [8–10], acetol [6], and alkyl aromatics [11]. Several studies have investigated the reaction pathway for transformation of glycerol to olefins and aromatics [11–13]. However, the detailed intermediates have not been published. Herein, we report the one-step transformation of glycerol to aro- matics over various SiO 2 /Al 2 O 3 ratios of HZSM-5 catalysts. Due to its shape selectivity and suitable acid properties, HZSM-5 showed the superior catalytic performance in converting glycerol to aro- matics [11,14,15]. To enhance the activity and selectivity to BTX aromatics, dehydrogenation promoter, Zn, is incorporated to the HZSM-5 zeolites [16]. Broadly speaking, HZSM-5 zeolites modified with Zn are active catalysts for the aromatization of light alkanes [17–20]. The modified Zn promotes the formation of aromatics by decrease the strong Brönsted acid sites, suppressed the paraffins http://dx.doi.org/10.1016/j.cattod.2014.12.030 0920-5861/© 2015 Elsevier B.V. All rights reserved.