Effect of calcination temperature on characteristics of sulfated zirconia and its application as catalyst for isosynthesis Nicha Tangchupong a , Watcharapong Khaodee a , Bunjerd Jongsomjit a , Navadol Laosiripojana b , Piyasan Praserthdam a , Suttichai Assabumrungrat a, ⁎ a Center of Excellence in Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand b The Joint Graduate School of Energy and Environment, King Mongkut's University of Technology Thonburi, Bangkok 10140, Thailand abstract article info Article history: Received 11 April 2009 Received in revised form 29 July 2009 Accepted 4 September 2009 Keywords: CO hydrogenation Isobutene Isosynthesis Sulfated zirconia Synthesis gas The effect of catalyst calcination temperature (450 °C, 600 °C, and 750 °C) on catalytic performance of synthesized and commercial grade sulfated zirconia catalysts towards isosynthesis was studied. The characteristics of these catalysts were determined by using various techniques including BET surface area, XRD, NH 3 - and CO 2 -TPD, ESR, and XPS in order to relate the catalytic reactivity with their physical, chemical, and surface properties. It was found that, for both synthesized and commercial sulfated zirconia catalysts, the increase of calcination temperature resulted in the increase of monoclinic phase in sulfated zirconia, and the decrease of acid sites. According to the catalytic reactivity, at high calcination temperature, lower CO conversion, but higher isobutene production selectivity was observed from commercial sulfated zirconia. As for synthesized sulfated zirconia, the isobutene production selectivity slightly decreased with increasing calcination temperature, whereas the CO conversion was maximized at the calcination temperature of 600 °C. We concluded from the study that the difference in the calcination temperatures influenced the catalytic performance, sulfur content, specific surface area, phase composition, the relative intensity of Zr 3+ , and acid–base properties of the catalysts. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Isosynthesis via carbon monoxide hydrogenation is an attractive route for producing isobutene which is an important raw material for the production of important octane enhancers such as methyl tert- butyl ether (MTBE) and ethyl tert-butyl ether (ETBE). Currently, isobutene is extracted from the C 4 stream in petroleum refining process. However, the supply of isobutene from the petroleum products is likely inadequate in the near future. Syngas derived from a renewable resource such as biomass is expected to be an alternative source for the production of isobutene. This route shows potential benefits, for examples, (i) the chosen resource of isobutene production is renewable, (ii) carbon dioxide, a byproduct of fermentation process, is substantially consumed to produce syngas, thus reducing the CO 2 emission to the atmosphere, and (iii) the ratio of carbon monoxide to hydrogen of 1:1 for the syngas from fermentation of biomass is suitable for the isosynthesis reaction. Since the first report by Pichler and Ziesecke in 1950s [1], some research groups have focused on developing suitable catalysts for the isosynthesis. Difficult reducible oxides such as thoria (ThO 2 ) and zirconia (ZrO 2 ) have been reported to be suitable catalysts for isosynthesis reaction rather than other reduced transition metals [2]. Most studies [3–7] have demonstrated that zirconia is a selective catalyst for isosynthesis. Then, various mixed metal oxides such as Sm 2 O 3 –ZrO 2 [8] and CeO 2 –TiO 2 [9] and Ca-promoted zirconia [10] have been tested. In our previous works, micron- and nanoscale zirconia and ceria were tested for the isosynthesis [11,12]. It was reported that the acid–base properties, the crystallite size and crystal phase essentially influence the catalytic performance. At the same crystallite size, ceria shows higher activity than zirconia [11]. The temperature ramping rate during calcination also has an effect on characteristics of nanoscale zirconia and its catalytic performance for isosynthesis [12]. It was shown that both tetragonal phase in zirconia and intensity of Zr 3+ influence the selectivity to isobutene. ZrO 2 –CeO 2 mixed oxide catalysts synthesized by coprecipitation and physical mixing methods with various contents of CeO 2 were also investigated [13]. It was reported that the catalysts prepared by the physical mixing method offer higher catalytic activity than those prepared by the coprecipitation method. The change in the selectivity of isobutene in hydrocarbons of the catalysts was well-correlated with the change in intensity of Zr 3+ . The isosynthesis of sulfated zirconia catalysts with various contents of sulfur (from 0.1 to 0.75 wt.%) were studied [14]. It was observed that the catalytic reactivity and selectivity significantly improved by sulfur loading. This can be related to the acid–base properties, specific surface area and phase composition. Fuel Processing Technology 91 (2010) 121–126 ⁎ Corresponding author. Tel.: +66 2 218 6868: fax: +66 2 218 6877. E-mail address: Suttichai.A@chula.ac.th (S. Assabumrungrat). 0378-3820/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2009.09.003 Contents lists available at ScienceDirect Fuel Processing Technology journal homepage: www.elsevier.com/locate/fuproc