One question per day: Methanol and purification technology forum version, 20180814
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Brief summary: The role of carbon dioxide in the methanol synthesis reaction: There are three reactions in the methanol synthesis process: 1. Hydrogenation of carbon monoxide to produce methanol, 2. Hydrogenation of carbon dioxide to produce methanol, 3. Conversion of carbon monoxide into carbon dioxide. Of these three reactions, the first one is the main reaction. But this is only valid under normal methanol synthesis conditions, when the CO2 concentration reaches a certain level. In low-pressure methanol plants, in addition to the hydrogenation of carbon monoxide to produce methanol, other hydrogenation reactions occur to yield C1–C4 alcohols. Therefore, in the low-pressure methanol synthesis process, CO2 is particularly important; its presence inhibits the formation of other alcohols. This also suppresses other side reactions that may occur in the methanol synthesis reaction. The main by-product of the side reaction is C2—ethanol. The drawback of the presence of carbon dioxide is that, compared to hydrogenation with carbon monoxide, it requires one more atom of hydrogen and produces one more molecule of water; an excessive amount of this can increase the energy consumption required for distillation. However, the presence of carbon dioxide reduces the formation of by-products such as dimethyl ether and ethanol, improves product quality, lowers the reaction heat, effectively prevents an increase in synthesis temperature, and extends the lifespan of the catalyst. The presence of carbon dioxide can, to some extent, prevent carbon monoxide from being converted into carbon dioxide, a reaction that occurs in the presence of water vapor. Methanol synthesis is a gas-solid phase catalytic reaction, with the active centers of the catalyst located at the reduced Cu-CuO interface; therefore, the addition of Cr2O3 or Al2O3 to the catalyst helps prevent its reduction and aging. Maintaining a certain amount of oxygen-containing polar molecules in the gas phase can also help prevent the catalyst from being reduced and aging.
There are 3 reactions in the methanol synthesis process: 1. Hydrogenation of carbon monoxide to produce methanol, 2. Hydrogenation of carbon dioxide to produce methanol, 3. Conversion of carbon monoxide into carbon dioxide. Of these three reactions, the first one is the main reaction. But this is only valid under normal methanol synthesis conditions, when the CO2 concentration reaches a certain level. In low-pressure methanol plants, in addition to the hydrogenation of carbon monoxide to produce methanol, other hydrogenation reactions occur to yield C1–C4 alcohols. Therefore, in the low-pressure methanol synthesis process, CO2 is particularly important; its presence inhibits the formation of other alcohols. This also suppresses other side reactions that may occur in the methanol synthesis reaction. The main by-product of the side reaction is C2—ethanol. The drawback of the presence of carbon dioxide is that, compared to hydrogenation with carbon monoxide, it requires one more atom of hydrogen and produces one more molecule of water; an excessive amount of this can increase the energy consumption required for distillation. However, the presence of carbon dioxide reduces the formation of by-products such as dimethyl ether and ethanol, improves product quality, lowers the reaction heat, effectively prevents an increase in synthesis temperature, and extends the lifespan of the catalyst. The presence of carbon dioxide can, to some extent, prevent carbon monoxide from being converted into carbon dioxide, a reaction that occurs in the presence of water vapor. Methanol synthesis is a gas-solid phase catalytic reaction, with the active centers of the catalyst located at the reduced Cu-CuO interface; therefore, the addition of Cr2O3 or Al2O3 to the catalyst helps prevent its reduction and aging. Maintaining a certain amount of oxygen-containing polar molecules in the gas phase can also help prevent the catalyst from being reduced and aging.