The impact of carbon dioxide in methanol production

The addition of CO2 is mainly to maintain a reasonable hydrogen-to-carbon ratio, so that the fresh gas composition is more conducive to the needs of synthesis, thereby increasing the crude toluene production.

The addition of carbon dioxide is mainly to participate in the reaction of synthesizing methanol. For copper-based catalysts, the role of carbon dioxide is relatively complex. It has both a kinetic role and a possible role as a chemical additive. To sum up, its advantages are as follows:: 1. Containing a certain amount of CO2 can promote the increase of methanol yield ； 2. Improve the selectivity of the catalyst and reduce the occurrence of side reactions such as ethers ； 3. It can be more conducive to adjusting the temperature, preventing over-temperature and extending the life of the catalyst. ； 4. Prevent carbon deposition on the catalyst. Chemical reactions have their advantages and disadvantages, including the following:: 1. Compared with the synthesis of methanol from CO, 0.7m3 more H2 is consumed for every 1kg of methanol produced. ； 2. Increase the water content in crude alcohol and reduce the methanol concentration. In summary, the pros and cons of CO2 should be weighed when choosing operating conditions. Usually, in the early stage of use, when the catalyst activity is good, the concentration of CO2 in the feed gas should be appropriately increased so that the reaction of synthesizing methanol will not be too violent, so as to facilitate the control of bed temperature. ； In the later period of use, the concentration of CO2 in the raw gas should be appropriately reduced to promote the methanol synthesis reaction and control and stabilize the bed temperature. According to the experience of several methanol plants and catalyst manufacturers, when using copper-based catalysts, the CO2 content in the feed gas is usually around 6% (volume), and the maximum allowable CO2 content is 12% to 15%.

Can play a role in protecting the catalyst. Because it releases less heat when participating in the reaction, it can reduce the occurrence of side reactions. However, if there is too much CO2, it will increase the output and increase the consumption of distillation.

The role of carbon dioxide in synthesis is explained very clearly on the third floor, so I won’t repeat it here. Supplementing carbon dioxide will undoubtedly increase the number of carbon atoms, and will undoubtedly increase methanol production while ensuring the hydrogen-to-carbon ratio. In the conversion section, carbon dioxide and methane have a reforming reaction, which plays a role similar to water vapor. At the same time, there is also a transformation reaction of CO+H2O=CO2+H2. As the reformer outlet temperature increases, the CO2 transformation becomes more complete.