Role of Cr on Cu-Cr catalyst via direct ethanol dehydrogenation to ethyl acetate

This study aims to convert ethanol to ethyl acetate and acetaldehyde using the catalytic ethanol dehydrogenation. The Cu-Cr catalysts were prepared via co-precipitation method using chromium (III) nitrate and copper nitrate precursors having different CuO weights between 50 and 80 wt% balancing with Cr2O3. The fresh catalyst was reduced by mixed gas of H2:N2 (10:90%) at 250ºC for 1 and 2 h (the non-reduced sample was also tested for comparative results). The structural properties of Cu-Cr catalysts were investigated by N2 physisorption, XRD, SEM-EDX, H2-TPR, XPS, NH3-TPD, and CO2-TPD. The ethanol dehydrogenation was carried out in a borosilicate glass fixed-bed continuous flow reactor at the specific condition [300 °C, atmospheric pressure, and WHSV = 3 (gethanol gcatalyst−1) h−1]. Based on the results, the ethyl acetate selectivity on 50 Cu-Cr catalyst (Low atomic Cu/Cr ratio) apparently increased by 1.6 times with increasing reduction time to 2 h having the highest ethyl acetate selectivity. Interestingly, the results from ethanol dehydrogenation indicated that the chromium promoter combining with CuxO in the 50 Cu-Cr catalyst increased the dispersion of copper species, facilitated the reduction, and increased the amount of Lewis acid sites. Moreover, the suitable reduction times can alter the distribution of CuCr2O4, Cu+, and Cu0, which resulted in increased ethyl acetate selectivity. The 50 Cu-Cr catalyst also exhibited good stability.