Cu/ZnO/Al2O3 catalyst with the addition of tri-promoters (Mn/Nb/Zr) was investigated with respect to their catalytic activity and stability in a prolonged reaction duration in methanol synthesis. Spent catalysts were characterized using N2 adsorption-desorption, FESEM/EDX, TEM, N2O chemisorption, and XPS for their physicochemical properties. The catalyst longevity study was evaluated at two days, seven days, and 14 days at 300 °C, 31.25 bar, 2160 mL/g.hr GHSV, and H2:CO2 at 10:1. The CO2 conversion and methanol yield decreased by about 5.7 and 7.7, respectively, when the reaction duration was prolonged to 14 days. A slight reduction in catalytic activity under prolonged reaction duration was found due to thermal degradation. © 2023 by the authors.