Applied Catalysis B: Environmental 201 (2017) 278–289 Contents lists available at ScienceDirect Applied Catalysis B: Environmental j ourna l h omepa ge: www.elsevier.com/locate/apcatb Olefin Upgrading over Ir/ZSM-5 catalysts under methane environment Yang Lou, Peng He, Lulu Zhao, Wei Cheng, Hua Song ∗ Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Dr NW, Calgary, Alberta T2N 1N4, Canada a r t i c l e i n f o Article history: Received 12 March 2016 Received in revised form 17 August 2016 Accepted 19 August 2016 Available online 21 August 2016 Keywords: Methane activation Bifunctional catalysts Ir/ZSM-5 Olefin upgrading Hydrogen donor a b s t r a c t Upgrading olefin in the synthetic oil to alkane is highly desired due to its high volatility and thermal unstability as well as low energy density. Unlike conventional hydrotreating, methane (CH 4 ) was used in this study as the novel hydrogen donor for olefin saturation. The significant increase of H/C atomic ratio of product oil from 1.69 ± 0.02 (over pure ZSM-5) to 2.04 ± 0.02 (over Ir/ZSM-5 (10.0)) and the alkane content up to 83.8 ± 2.1% in the upgraded oil indicated that methane could exhibit comparable catalytic performance to what hydrogen (H 2 ) did for olefin (1-Decene) upgrading over the developed bifunctional catalysts with low Ir loadings. The HRTEM and XPS data revealed that the highly dispersed metallic Ir particles with average size of 1.32 nm was coexisting with IrO 2 species. The synergic effects of Ir/IrO 2 obviously promoted the activation of methane, which supplied sufficient hydrogen for the saturation and stabilization of olefin. The results from BET indicated that the pore size and volume of the ZSM-5 support were increased upon Ir introduction, which provided more active sites for cracking olefin (1-decene). NH 3 -TPD results suggested that the presence of highly dispersed Ir increased the amount of surface acidity, which enhanced the formation and stabilization of carbenium ion intermediates. As a result, the produced alkanes were mainly composed of cyclopentane-derived compounds, like propylcyclopentane, 3-methylbutyl-cyclopentane and 1,2,4-trimethyl-cyclopentane, which has great application potential as immersion fluid and additive in the field of optics and petroleum. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Olefins including light and long-chain unsaturated compounds are abundant byproducts of catalytic cracking [1] and Fisher- Tropsch synthesis [2] but are underutilized as energy carriers because of their high volatility and low energy density [3]. In addi- tion, the presence of olefin could not only cause the formation of polymeric deposit due to its thermal instability during long-term storage and long distance transportation but also lead to gaso- line insufficient combustion, generating negative environmental impact. Therefore, upgrading olefin to alkane is critical not only for the enhancement of product stability but also for the protection of our environment. Generally, hydrotreating is widely employed to saturate olefins for the improvement of gasoline quality [4,5]. How- ever, the involvement of hydrogen (H 2 ) obviously increases the cost of this upgrading step since H 2 is not naturally available. Current steam reforming of natural gas (mainly composed of CH 4 ) accounts for almost 50% of the world feedstock for hydrogen (H 2 ) produc- tion but is operated in a high temperature range of 973–1173 K ∗ Corresponding author. E-mail address: sonh@ucalgary.ca (H. Song). [6,7], which not only increases the operation cost but also leads to huge emission of CO 2 . Hence, if methane could be directly used as the novel hydrogen donor and act as an alternative to expensive hydrogen gas for olefin upgrading, not only the operation costs but also greenhouse gas emission could be significantly reduced. Although direct activation of CH 4 is uneasy due to its symmet- rically geometric and stable electronic structure [8,9], the previous research reveals that the methane could be efficiently activated over bifunctional catalysts [10–14] (M/zeolites, M: metal species) in the presence of alkene and higher alkane at near atmospheric pres- sure and mild temperature (400–600 ◦ C). For instance, the presence of n-butene could efficiently facilitate CH 4 conversion up to 45.0% at 600 ◦ C and 1 atm, which produces not only high value prod- ucts of aromatics and H 2 but also exhibits high selectivity toward aromatics (up to 92.0%) formation [10]. From the aspect of ther- modynamics, the reaction barrier could be significantly reduced to zero or even negative when methane reacts with alkenes or higher alkanes under appropriate conditions; for example, the pos- itive Gibbs free energy change (Gr) value of direct formation of benzene from methane could become −4.1 kcal/mol at 500 ◦ C and −10.6 kcal/mol at 600 ◦ C when the ratio of n-butene/methane was 1.0 [10]. Moreover, Har [4] and Song et al. [15–18] reported that methane could act as comparable or even better hydrogen donors http://dx.doi.org/10.1016/j.apcatb.2016.08.047 0926-3373/© 2016 Elsevier B.V. All rights reserved.