What is the impact of inert gas content on methanol synthesis?

An increase in the content of inert gases in the syngas reduces the partial pressures of hydrogen and carbon monoxide, which is unfavorable for chemical stability and affects the rate of the synthesis reaction. During monohydric alcohol production, the syngas is entirely recycled to produce methanol; methanol synthesis represents the final stage of production. Inert gases accumulate continuously in the recycled gas, and if they are not regularly removed, this will affect the conversion rate and increase the pressure in the synthesis system. Therefore, it is necessary to continuously remove inert gases during monohydric alcohol production. According to available information, in the production process of monohydric alcohols using zinc-based catalysts, approximately 700–900 m³ of inert gas is emitted for every ton of crude methanol produced. Part of the inert gas in the system comes from nitrogen, methane, and other gases carried in the feed gas, while the other part originates from by-products formed during methanol synthesis, mainly methane and other non-condensable organic compounds.

Inert gases do not participate in the synthesis reaction, but they affect the reaction rate. Too high an inert gas content reduces the reaction rate, increasing the energy consumption per unit of output produced ； Maintaining a low inert gas content results in an increased vent volume and greater loss of useful gas. The appropriate level of inert gas content depends on the specific circumstances, and it is also one of the means for adjusting operating conditions. At the beginning of catalyst use, its activity is high, allowing for a higher content of inert gases; later on, a lower level of inert gases is generally maintained ； If high yield is the goal, the inert gas content can be kept low; if low consumption is the goal, a higher inert gas content can be maintained.