Effect of precipitation temperature on the performance of K-CuLaZrO₂ catalyst for isobutanol synthesis from syngas

The synthesis of isobutanol from syngas is a such complicated process, and the relationship between catalyst properties and isobutanol formation is still not fully understood yet. Coprecipitation is a common preparation method for solid composite oxides synthesis, by which, the catalyst will have high dispersion, strong interaction. However, it also remains many factors affecting the preparation process. In this work, the effect of precipitation temperature on the properties of catalysts at the beginning of precipitation reaction was investigated, and the relationship between the properties of catalysts and the formation of isobutanol was studied by different characterization methods in combination with the catalysts evaluation results, in order to further improve the formation mechanism of isobutanol. The results revealed that at lower precipitation temperature (30 ℃), the CuO was easier to be reduced due to the better Cu dispersion and stronger interaction in CuO and ZrO₂, at the same time as the CuO and ZrO₂ could form better solid solutions at this condition. Meanwhile, hydroxyl groups were formed on the catalyst surface at lower precipitation temperature during the catalyst preparation process, therefore these hydroxyl groups could react with CO to form surface C₁ species, which further promoted the growth of carbon chain and improved the selectivity of isobutanol. With the increase of precipitation temperature, CuO particles were enlarged; CuO-ZrO₂ solid solution was gradually destroyed; the interaction in CuO and ZrO₂ was weakened; and the content of surface hydroxyl was decreased, resulting in a decrease of surface C₁ species and isobutanol selectivity. Among all the catalysts, the highest selectivity of isobutanol (38.7%) was obtained over the CLZ-30 catalyst.