One-step synthesis of methylal via methanol oxidation by Mo:Fe(x)/HZSM-5 bifunctional catalyst

Abstract

The traditional one-step process for preparing methylal bifunctional catalyst has multiple limitations, including high cost, high acidity and low yield. In order to overcome these limitations, the author designed and studied a series of Mo:Fe(x)/HZSM-5 function catalyst with different ferromolybdenum ratios. The one-step process for preparing methyl acetal is realized in a fluidized bed reactor. The effect of different ferromolybdenum ratios on its catalytic performance was investigated and the optimum ferromolybdenum ratio catalyst was found. The results show that this new process and catalyst can overcome the disadvantages of traditional bifunctional catalysts and achieve a relatively high DMM yield. For instance, the methanol conversion ratio and DMM selectivity of the Mo:Fe(2)/HZSM-5 bifunctional catalyst reached 87.44% and 93%, respectively. Moreover, the recorded DMM yield was 81.32%, which was much higher than that of other research results. At the same time, the XPS catalyst activity and activation energy results show that increased molybdenum loading catalytic effect. However, when Mo/Fe > 2, the mutual promotion effect would be larger and part of the formaldehyde obtained by oxidative dehydrogenation of methanol would be further oxidized to obtain the by-product formic acid, further producing more methyl formate. In addition, the self-made Mo:Fe(2)/HZSM-5 dual-functional catalyst exhibits high stability and carbon deposition resistance under severe operating conditions, compared to other bifunctional catalysts of this process.