Iso-butanol direct synthesis from syngas over the alkali metals modified Cr/ZnO catalysts

Abstract This report demonstrated the iso-butanol direct synthesis from syngas over varied alkali metals modified Cr/ZnO catalyst. The Cr/ZnO catalyst was prepared by a general co-precipitation method and then modified with varied alkali metals: Li, Na, K and Cs. The prepared alkali metals modified catalysts, Cr/ZnO-Li, Cr/ZnO-Na, Cr/ZnO-K and Cr/ZnO-Cs, were evaluated by the reaction of iso-butanal direct synthesis from syngas. Among these catalysts, the K modified catalyst Cr/ZnO-K exhibited excellent catalytic ability on iso-butanol synthesis. The CO conversion obtained on this Cr/ZnO-K catalyst reached up to 27.39%, with the highest iso-butanol selectivity of 15.58%. We also investigated the effect of different Li precursors, Li₂CO₃ and LiOH, on the catalytic performance of Cr/ZnO catalyst, and the reaction results indicated that the LiOH precursor modified catalyst Cr/ZnO-Li-OH had better catalytic performance. All the catalysts were characterized by BET, XRD, H₂-TPR, SEM-EDS and TG-DTA to further disclose the function of alkali metals to Cr/ZnO catalyst in iso-butanol synthesis. We found that the reducibility of the active phase of non-stoichiometric spinel Zn_xCr_2/3(1-x)O, the crucial species for iso-butanol synthesis, was significantly influenced by alkali metals modification, which consequently determined in the diverse catalytic performance of alkali metals modified catalysts for iso-butanol synthesis.