This paper reports on the scaling-up of a one-step methanol production process from the laboratory scale to the pilot scale. This lays the foundation for the industrialization of a one-step process for preparing DMM from methanol. After a long period of operation in the circulating fluidized bed, the Fe-Mo/HZSM-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 addition, in-situ DRIFTS was used to explore the effects of reaction time, the Mo-Fe ratio and carrier Si-Al ratio on the reaction and product distribution. It was found that the synergistic effect of oxidation centers and acid centers was the fundamental reason for the excellent catalytic performance of the Fe-Mo/HZSM-5 catalyst. And proposed the reaction mechanisms in the one-step synthesis of methylal via methanol oxidation.

In the one-step preparation of methylal from methanol, achieving high methylal yield is a huge challenge. To address this problem, in this study a new Mo:Fe(2)/CAR catalyst was designed, screened and optimised. The results showed that the optimised bifunctional catalyst had superior catalytic performance, and the yield of methylal could reach 81.33%, much higher than other research results of this process. Through the use of XPS, NH3-TPD and PY-FTIR it was found that the appearance of Mo5+ promoted the coordination of the two terminal oxygen with the Mo double bond in the Fe2(MoO4)3 octahedron, and that the increase in the weak acid strength of the catalyst and the coordination of suitable Brønsted acids (B acids) and Lewis acids (L acids) was the root cause of the catalytic activity. The apparent activation energy also further proved that Mo:Fe(2)/ HZSM-5(80-80) was highly suitable for the one-step production of methylal from methanol.

Based on the previous research on the Fe-Mo based bifunctional catalyst, the team explored the effects of reaction temperature, reaction space velocity and the feed ratio of methanol to air on the catalytic effect of the process, and found out the optimal reaction conditions for the process. The results show that too high reaction temperature is not conducive to the formation of the target product DMM, and this phenomenon is verified by thermodynamic analysis. At the same time, it was found from the analysis of the catalyst's microstructure and surface characteristics that an excessively high reaction temperature would not only cause metal oxides to accumulate on the catalyst surface, blocked channels and reduced specific surface area, but also it will destroy the acid active sites on the catalyst surface, weaken the acidity of the catalyst and reduce the catalytic activity.