Promotion effect of La on oxygen vacancy formation over Zn-Cr based catalyst for isobutanol synthesis from syngas

A series of catalysts were designed and synthesized via doping lanthanum into ZnCr oxide to realize efficient synthesis of isobutanol from syngas. By applying a combination of characterizations (XRD, TEM, EPR, XPS and in situ FT-IR) and DFT calculations, the effects of lanthanum promoter on catalyst structure and catalytic performance were investigated. With the doping of lanthanum, ZnCrLax composite oxides with a novel catalyst structure were constructed, in which Zn atom at tetrahedron site was partly substituted by doping La atom. The presence of this structure enhanced the formation of more oxygen vacancy sites and further benefitted the CO activation. In addition, formate intermediate was easier to generate and exhibited superior stability over ZnCrLax surface thus leaded to remarkably promoted catalytic activity. The ZnCrLa0.05 catalyst achieved optimum total alcohols selectivity of 61%, and the fraction of isobutanol reached as high as 24.6% under CO conversion of 23%.