Methanol Weekly Topic: How to control the hydrogen-to-carbon ratio of methanol? 2015.0...

1. How to control the hydrogen-to-carbon ratio in methanol? For methanol feed gas, the hydrogen-to-carbon ratio is required to be maintained at H2-CO2/CO+CO2=2.05～2.15; this ratio can be adjusted by controlling the contents of CO and CO2 in the feed gas as well as the amount of off-gas released. 2. What is the role of carbon dioxide? 1) Carbon dioxide itself is a raw material for methanol synthesis. 2) The presence of carbon dioxide inhibits the formation of dimethyl ether to some extent. 3) It prevents the conversion of carbon monoxide into carbon dioxide, a reaction that occurs in the presence of water vapor. 4) It facilitates temperature regulation and prevents overheating; since the heat of reaction for carbon dioxide is 42.9 KJ/mol lower than that for carbon monoxide, the involvement of carbon dioxide in the reaction helps to prevent an increase in the synthesis temperature, thereby maintaining the catalyst’s activity and extending its service life. 3. What is the optimal level of control? The optimal content of carbon dioxide in the synthetic feed gas should be adjusted according to the type of methanol synthesis catalyst and the operating temperature. In high-pressure methanol plants using zinc and chromium catalysts, the CO2 content should be below 5%, whereas with copper-based catalysts, the CO2 content in the feed gas can be increased to a certain extent. The medium and low-pressure methanol plants designed by Luchi Company for production using natural gas as raw material have a CO content of 15.1% in the synthesis feed gas, with a CO2 content of around 7.0%. M.M. Kanalarvayev believes that the concentration of carbon dioxide in the feed gas is determined by technical and economic considerations; the maximum allowable concentration is 12%-14%, while it is usually 4.5-5.5%. This allows for the maximum amount of methanol to be produced per unit volume of catalyst.

1. It is generally between 2.05 and 2.15; when the catalyst has high initial activity, the hydrogen-to-carbon ratio can be higher, around 2.3； The catalyst level should be relatively lower later on, controlled at around 2.2. 1 mole of CO2 reacts with 3 moles of H2 to produce methanol, whereas CO requires 2 moles of H2. Therefore, for H2 to react completely with 2CO + 3CO2, we have H2 – CO2 = 2CO + 2CO2’. Simplifying further gives H2 – CO2/(CO + CO2) = 2/1. Of course, in general, more H2 is needed, slightly exceeding this ratio. 2, 1) First is the raw material. 2) It reacts with hydrogen to produce methanol + water; the formation of water helps to control the catalyst temperature and prevent it from rising too high. 3) Experience has shown that ensuring a certain amount of carbon dioxide is present can prevent further reactions that lead to the formation of ethers due to excessively high methanol concentrations. 4) Although the presence of carbon dioxide is beneficial for the operation, its level should not be too high, as more hydrogen is required for the reaction. 3. It is generally kept at 3-5%