Effect of Reflux Time on the Performance of the Cu/ZrO₂ Catalyst for CO₂ Hydrogenation to Methanol

The hydrogenation of CO 2 into methanol was investigated by means of the Cu/ZrO 2 catalyst to analyze the effect of reflux time on catalytic performance. A series of high-activity Cu/ZrO 2 catalysts were prepared by introducing the support pretreated with ammonia reflux. The effect of reflux time on the structure and performance of all catalysts was systematically studied. Combined with various characterizations such as X-ray diffraction (XRD), N 2 physisorption, temperature-programmed reduction by H 2 (H 2 -TPR), temperature-programmed desorption of H 2 and CO 2, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM), it can be seen that the catalysts after reflux exhibited a stable amorphous structure with more medium and strong basic sites. Moreover, the proportion of defect oxygen and surface Cu + species for Cu/ZrO 2 catalysts increased, and the metal–support interaction was strengthened, which effectively increased active sites and promoted CO 2 activation, and thus, the catalyst with stronger activity and better stability was obtained. The CO 2 conversion dramatically increased by 4–5 times (from 5.4 to 22.1%) after reflux treatment, and the Cu/ZrO 2 -18h catalyst had the highest catalytic activity and a methanol space time yield of 394 g MeOH h –1 kg cat –1 at 260 °C.