Continuous low-temperature methanol synthesis from syngas containing CO2 on various Cu/ZnO catalysts was investigated by using a semibatch autoclave reactor. Methanol was easily produced at a temperature as low as 443 K and with a pressure of 50 bar with the aid of 2-butanol, which showed a very high efficiency with a one-pass yield of 47.0% and a selectivity of 98.9%. Methanol itself used as alcohol promoter exhibited a higher activity than other 1-alcohols because it has the lowest spatial effect. 2-Alcohols, however, exhibited the highest conversion among the same carbon number because of its well-balanced effects produced by their of electronic and spatial factors. The one-pass conversion was improved by increasing the catalyst weight because no thermodynamic limitations existed at low temperatures. The continuous low-temperature methanol synthesis is a very promising process because completely purified syngas is not necessary.