Direct Conversion of Syngas into Light Olefins over Zirconium‐Doped Indium(III) Oxide and SAPO‐34 Bifunctional Catalysts: Design of Oxide Component and Construction of Reaction Network

• Published in: ChemCatChem 2018-04, Vol.10 (7), p.1536-1541
• Main Authors: Su, Junjie, Wang, Dong, Wang, Yangdong, Zhou, Haibo, Liu, Chang, Liu, Su, Wang, Chuanming, Yang, Weimin, Xie, Zaiku, He, Mingyuan
• Format: Article
• Language: English
• Subjects: Activation; Alkenes; bifunctional catalysts; binary oxides; Carbon dioxide; Catalysts; Catalytic converters; Direct conversion; heterogeneous catalysis; Hydrogenation; Indium oxides; Pricing policies; Supply & demand; Synthesis gas; Zeolites; Zirconium oxides
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201702054

The direct synthesis of light olefins from syngas over a bifunctional catalyst containing an oxide and zeolite has been proven to be a promising strategy. Nevertheless, an unclear reaction network hinders any further enhancement in catalytic performance, such as increasing the conversion of CO. We herein report a novel bifunctional catalyst composed of a InZr binary oxide and SAPO‐34 zeolite displaying superior CO conversion (27.7 %) with selectivity to light olefins (73.6 %) at 400 °C, 2.0 MPa. We demonstrate that the Zr‐doped body‐centered cubic In2O3 phase, exhibiting higher stability than pure In2O3 under a reducing atmosphere, is the active oxide component for the initial activation of CO. A complete reaction network is proposed by DFT calculations and model reactions, revealing that CO activation over Zr‐In2O3 follows a quasi‐CO2 hydrogenation pathway and methanol is the key intermediate to be transformed into light olefins in zeolites. Moreover, inhibiting excessive hydrogenation is an effective strategy to achieve higher performance. Keen on alkenes: A high selectivity to light olefins (73.6 %) at a superior CO conversion (27.7 %) is achieved over a Cr‐free bifunctional catalyst composed of an InZr binary oxide and SAPO‐34 zeolite. Zr‐doped body‐centered cubic In2O3 is the active composition for initial activation of CO. The mechanism of CO activation over In‐based oxides is a quasi‐CO2 hydrogenation pathway.