Fig.6. Schematic of the reaction mechanism of methanol over the surface of Fe-Mo/ZSM-5 catalysts.
4. Conclusion
In conclusion, the pilot experiment of the circulating fluidized bed scaled-up reactor was successful, with the Fe-Mo/ZSM-5 catalyst enabling the production of the valuable product DMM with a sustainable high yield. The influence of the change of reaction conditions on the product distribution was explored. After a long period of operation in the circulating fluidized bed, the Fe-Mo/ZSM-5 catalyst was shown to have high stability and carbon deposition resistance, and the regeneration effect of the circulating regeneration fluidized bed was better. In situ infrared spectroscopy was used to explore the effect of the reaction time on the reaction of methanol and the product distribution. It was found that methanol was first oxidized to form FA and a small amount of DME on the Fe-Mo/ZSM-5 catalyst, following which FA further oxidized to form formic acid. Then, FA and methanol underwent polycondensation to form DMM, and formic acid and methanol underwent polycondensation to form MF. In situ infrared spectroscopy was also used to explore the influence of changes in the ratio of Mo to Fe and the ratio of Si to Al in the carrier on the reaction and product distribution. It was found that the synergistic effect of oxidation centers and acid centers was the basic reason for the excellent catalytic performance of the Fe-Mo/ZSM-5 catalyst. Finally, through in-situ online exploration, the reaction mechanism of the one-step process of preparing DMM from methanol was proposed. These studies have laid the foundation for the in-depth development, promotion and application of new technology.