A Mesoporous Ce 0.5 Zr 0.5 O 2 Solid Solution Catalyst for CO Hydrogenation to iso-C 4 Hydrocarbons
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A Mesoporous Ce0.5Zr0.5O2 Solid Solution Catalyst for CO Hydrogenation to iso-C4 Hydrocarbons Shaohui Ge Æ Dehua He Æ Zhanping Li
Received: 21 April 2008 / Accepted: 29 July 2008 / Published online: 3 September 2008 Ó Springer Science+Business Media, LLC 2008
Abstract Mesoporous Ce0.5Zr0.5O2 solid solution catalyst was synthesized by a sol-gel process using block copolymer Pluronic P123 as the template. The as-prepared catalyst was characterized by X-ray diffraction, H2-Temperature-programed reduction, BET, and X-ray photoelectron spectra techniques. The catalytic properties of the catalyst were evaluated by the synthesis of iso-C4 hydrocarbons via CO hydrogenation. The mesoporous catalyst showed much better catalytic selectivity and yield of isobutene and isobutane (i-C4) from CO hydrogenation at 673–723 K, 5.0 MPa, and 720 h-1, than the solid Ce0.5Zr0.5O2 catalyst prepared by coprecipitation. This was due to the higher BET surface area, pore volume and the reducibility of the mesoporous Ce0.5Zr0.5O2 catalyst. Keywords Ce0.5Zr0.5O2 Mesoporous Isosynthesis Hydrogenation Catalyst
1 Introduction Isosynthesis, referred as the reaction that selectively converts coal or natural gas-derive syn-gas (CO ? H2) to i-C4 hydrocarbons (isobutene and isobutane), has attracted much attention in recent years because of a world-wide shortage of isobutene and isobutane which are extracted from a limited C4 stream of a petroleum cracking process at the present time [1]. It has been pointed that zirconia
(ZrO2) was the most selective catalyst for isosynthesis [2, 3]. Another oxide catalyst, ceria (CeO2), was also selective to isobutene in C4 hydrocarbons [4]. Then, the ZrO2 catalyst doped by CeO2 for promoting i-C4 selectivity in the isosynthesis via CO hydrogenation was prepared by coprecipitation [5, 6]. It was found that the incorporation of CeO2 with ZrO2 (Ce/Zr = 1, molar ratio) changed the redox and acid-base properties of ZrO2-based catalysts and subsequently affected the catalytic performance [5]. The CeO2–ZrO2 sample above was composed of spherical solid nanoparticles. Recently, CeO2–ZrO2 oxides in an ordered mesoporous structure are expected to provide enhanced catalytic performance due to their large surface area and a certain degree of size and shape selective. For example, the mesoporous Ce1-xZrxO2 (0 \ x \ 1) solid solutions with cubic structure were used to prepare the corresponding Pd/Ce1-xZrxO2 (0 \ x \ 1) for CO conversion [7]. For the isosynthesis of i-C4 hydrocarbons, the Ce0.5Zr0.5O2 showed the highest selectivity and yield among various Ce1-xZrxO2 (0 \ x \ 1) solid solutions catalysts prepared by coprecipitation [5, 7–10]. In this paper, a mesoporous Ce0.5Zr0.5O2 was synthesized by a solgel process using block copolymer Pluronic P123 as the template according to [11]. For comparison, the solid Ce0.5Zr0.5O2 catalyst prepared by coprecipitation was also prepared. The as-prepared catalysts were evaluated by the synthesis of iso-C4 hydrocarbons via CO hydrogenation.
2 Experimental S. Ge D. He (&) Z. Li
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