Short Communication A novel silicalite-1 zeolite shell encapsulated iron-based catalyst for controlling synthesis of light alkenes from syngas Nan Jiang a , Guohui Yang a,c , Xiongfu Zhang a, ⁎, Lei Wang b, ⁎⁎, Chunyan Shi b , Noritatsu Tsubaki c a State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China b State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China c Department of Applied Chemistry, School of Engineering, University of Toyama, Toyama 930–8555, Japan abstract article info Article history: Received 24 October 2010 Received in revised form 18 February 2011 Accepted 22 February 2011 Available online 2 March 2011 Keywords: Zeolite capsule catalyst Silicalite-1 shell FTS Iron-based catalyst Light alkenes A well-designed zeolite capsule catalyst with a Core (Fe/SiO 2 )-Shell (Silicalite-1) structure was successfully prepared by zeolite seeding and then zeolite shell growing via secondary hydrothermal method. The characterization on this zeolite capsule catalyst indicated that it had a compact, defect-free zeolite shell enwrapping core catalyst tightly. The application of this zeolite capsule catalyst was the direct synthesis of light alkenes from syngas via Fischer–Tropsch synthesis (FTS) reaction. This zeolite capsule catalyst exhibited excellent abilities compared with the traditional FTS catalyst, both on the controlled synthesis of the desirable light alkenes and the suppressing formation of the undesired long-chain hydrocarbons. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Light alkenes (ethylene, propylene, etc.) are very important organic chemical materials and produced mainly by steam cracking of naphtha from petroleum, here the naphtha is derived from petroleum. With the soaring price of crude oil and dwindling resources, it is necessary to develop a non-petroleum way for light alkenes production [1,2]. Fischer–Tropsch synthesis (FTS) reaction is one of the promising processes for hydrocarbons synthesis [3], and the syngas (CO + H 2 ) used for FTS reaction is widely derived from biomass, natural gas, or coal [4]. Hydrocarbons produced by FTS reaction are sulfur-free, nitrogen-free, and aromatics-free, which makes the FTS products inexpensive and environment-friendly. But the light alkenes selectivity of FTS reaction is very low as the main products are normal paraffin [5]. In order to improve the conventional FTS products composition, that is, increase the light alkenes selectivity, some metals (potassium, manganese, zinc and so on) are usually adopted as the promoters of conventional FTS catalysts to improve their activity and/or alkenes selectivity [6–8]. In addition, some metals directly supported on zeolite as catalysts, also exhibit good selectivity in light alkenes via FTS reaction, but they usually show bad activity [9,10]. Unfortunately, former researchers only focused on the catalyst's composition rather than its structure. As we know, a heterogeneous catalyst will show the good performance only when it has a well-designed structure [11]. Recently, the core-shell concept for the combination of two different types of materials has aroused a great interest because of its promising applications in catalysis, electronics, sensors and semiconductors [12–16]. In this report, different from traditional catalysts, a novel catalyst with a well-designed Core (Fe/SiO 2 )-Shell (Silicalite-1 membrane) structure is successfully prepared via secondary growth method. The zeolite shell enwrapping core catalyst tightly, as shown in Fig. 1, provides a tailor-made confined reaction environment, and results in the spatially confined effect and shape selectivity function in FTS reaction, which helps light alkenes generation and suppressing the formation of undesired long-chain hydrocarbons. 2. Experimental 2.1. Preparation of Conventional FTS Catalyst Fe/SiO 2 Silica pellets (CARIACT Q-10, Fuji Silysia Chemical Ltd., pellet size: 1.81–2.36 mm, surface area: 282 m 2 g -1 ) were used as supports for 20 wt.% Fe/SiO 2 catalyst preparation by incipient wetness impregnation from a ferric nitrate solution (i.e., (Fe(NO 3 ) 3 ·9H 2 O, 98.5%, Kermel). Catalyst precursors were firstly dried at 378 K for 2 h, and then calcined in air at 823 K for 6 h. The final samples were iron-based 20 wt.% Fe/SiO 2 catalysts. Catalysis Communications 12 (2011) 951–954 ⁎ Corresponding author. Tel./fax: + 86 411 84986155. ⁎⁎ Corresponding author. Tel./fax: + 86 10 82627080. E-mail addresses: xfzhang@dlut.edu.cn (X. Zhang), lwang@home.ipe.ac.cn (L. Wang). 1566-7367/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.catcom.2011.02.021 Contents lists available at ScienceDirect Catalysis Communications journal homepage: www.elsevier.com/locate/catcom