Please cite this article in press as: N. Prakash, et al., Role of acid solvent to prepare highly active PtSn/-Al 2 O 3 catalysts in dehydrogenation of propane to propylene, Catal. Today (2017), http://dx.doi.org/10.1016/j.cattod.2017.02.027 ARTICLE IN PRESS G Model CATTOD-10616; No. of Pages 9 Catalysis Today xxx (2017) xxx–xxx Contents lists available at ScienceDirect Catalysis Today journal homepage: www.elsevier.com/locate/cattod Role of acid solvent to prepare highly active PtSn/-Al 2 O 3 catalysts in dehydrogenation of propane to propylene Natarajan Prakash a,c , Mi-Hyun Lee a , Sungho Yoon c , Kwang-Deog Jung a,b,∗ a Clean Energy Research Centre, Korea Institute of Science and Technology, P.O. Box 1311, Cheongryang, Seoul 136-791, Republic of Korea b Clean Energy and Chemical Engineering, University of Science and Technology, 217, Gajeong-ro Yuseong-gu, Daejeon, Republic of Korea c Department of Bio & Nano Chemistry, Kookmin University, 861-1, Jeongneung-dong, Seongbuk-gu, Republic of Korea a r t i c l e i n f o Article history: Received 14 August 2016 Received in revised form 13 February 2017 Accepted 21 February 2017 Available online xxx Keywords: Propane dehydrogenation Influence of solvents Impregnation sequence Metal dispersion PtSn alloy Particle size a b s t r a c t The PtSn bimetallic catalysts with a high Pt metal dispersion were successfully prepared using acid sol- vent. The aqueous mixed acid solution of HCl and HNO 3 was used as solvent to dissolve the Pt and Sn precursors. The (Pt-Sn)A, (Sn-Pt)A and (PtSn)A catalysts (PtSnA catalysts) were prepared by sequential impregnation of Pt and Sn, sequential impregnation of Sn and Pt and co-impregnation, respectively. The metal dispersions of the (Pt-Sn)A, (Sn-Pt)A and (PtSn)A catalysts were 21.6%, 25.9%, 24.4%, respectively. For comparison, the (Pt-Sn)E, (Sn-Pt)E and (PtSn)E catalysts were prepared using ethanol similarly to the PtSnA catalysts. The metal dispersions of (Pt-Sn)E, (Sn-Pt)E and (PtSn)E catalysts (PtSnE catalysts) were 7.1%, 5.4%, and 7.5%, respectively. The metal dispersions of the PtSnA catalysts were three times higher than those of the PtSnE catalysts. The Pt metal particle sizes of the PtSnA catalysts were measured to be 4.4–6.9 nm by chemisorption and 1.9–2.3 nm by Technai STEM images. However, it was observed by a Titan STEM that the aggregates of the metal sub-nanoparticles were dispersed on the PtSnA catalysts. All the metal particles on the PtSnA catalysts existed in the sub-nano sizes. The particle size of 1.9–2.3 nm by the Technai STEM is the size of the aggregates of the metal sub-nanoparticles. Propane dehydrogenation was conducted with the prepared catalysts at 873 K and a GHSV of 22,500 mL g cat −1 h −1 . The initial cat- alytic activity decreased in the order of (Sn-Pt)A > (PtSn)A > (Pt-Sn)A > (PtSn)E » (Pt-Sn)E > (Sn-Pt)E. The PtSnA catalysts showed not only the high activity but also the high selectivity and stability in propane dehydrogenation for 15 h. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Light olefins are important feedstocks for polymer and petrochemical industries [1–6]. The global propylene market is anticipated to exhibit considerable growth in coming years and it is estimated about 165 million tons by 2030 [7]. Conventionally, propylene has been produced by steam cracking (SC), methanol to olefin production (MTO) and fluid catalytic cracking (FCC) of light oil fractions. From recent comprehensive reviews on light alkane dehydrogenation to light olefin using Pt, Cr, V and Mo metals [8–11], it can be deduced that the Pt-based alloy catalysts showed high activity and stability as compared with other metal or metal oxide catalysts. Accordingly, Pt-based catalysts were widely stud- ied for propane dehydrogenation. Recently, structured supports ∗ Corresponding author at: Clean Energy Research Centre, Korea Institute of Sci- ence and Technology, P.O. Box 1311, Cheongryang, Seoul 136-791, Republic of Korea. E-mail addresses: jkdcat@kist.re.kr, jkdyym@hanmail.net (K.-D. Jung). such as zeolites and mesoporous silicas as well as modified alu- mina supports have been newly attempted to improve the catalytic activity for propane dehydrogenation [12–20]. Alumina supported PtSn catalysts are regarded as best candidates for propane dehy- drogenation due to their high selectivity to light olefin. The high thermal stability as well as the low acidity of the alumina sup- ported PtSn catalysts led to the high metal dispersion and the low coke formation, resulting in high activity and stability [21–25]. PtSn alloy formation on the alumina can also prevent the coke formation on active Pt sites, which are explained by geometric and electronic effects [26–28]. Accordingly, Characterizations of PtSn catalysts have been intensively performed to correlate the catalytic activity with the PtSn alloy formation [25,29–31]. The quantity of PtSn metal loadings and the atomic ratios of Sn to Pt were optimized to show the highest propylene yield in propane dehydrogenation [32–34]. The amount of alkali metal doping on the PtSn catalysts was also optimized to increase the selectivity to light olefins [12,20]. http://dx.doi.org/10.1016/j.cattod.2017.02.027 0920-5861/© 2017 Elsevier B.V. All rights reserved.