Variation Trends of CO Hydrogenation Performance of (al)–o–(zn) Supported Cobalt Nanocomposites: Effects of Gradual Doping with Zn–O Lewis Base

Literature about Lewis base doped spinel-type cobalt CO hydrogenation catalysts is sparse. A series of undoped Co/γ-Al2O3 as well as Zn–O Lewis base doped Co0/(Al)–O–(Zn) nanocomposites were prepared via coprecipitation or impregnation followed by calcinations and single-step reduction. The overall concentration of zinc by weight ranges from 0 to 68.23 %. These materials were examined by XRD, nitrogen sorption, CO2-TPD, FESEM and HRTEM. The nanocomposite with atomic Zn/(Al + Zn) ratio of 1/5 exhibits the smallest average size of Co0 crystallites of 7.6 nm as well as the largest BET surface area of 151.1 m2/g. The CO hydrogenation performance of nanocomposites were tested at a pressure of 2.0 MPa and a space velocity of 700 mL g cat−1 h−1. Variation trends of CO hydrogenation performance due to gradual doping with Zn–O Lewis base were described in details. The CO2-TPD data suggest that doping with zinc may generally enhance the surface basicity of nanocomposites. Appropriate doping the alumina support with Zn–O Lewis base may effectively lower down the production of methane by up to ca. 23 %, suppress the production of C5+ hydrocarbons, facilitate the production of C2–C4 hydrocarbons, and significantly enhance the C2–C4 olefin/paraffin ratio, which are favored by the Fischer–Tropsch to olefins (FTO) process.