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.