Synthesis of trioxane from formaldehyde catalyzed by [Ga, Al]-MFI zeolites

Abstract

ZSM-5 could be a good candidate for the catalysis of formaldehyde to trioxane (TOX) because of its appropriate and adjustable acid properties. However, the space-time yield (STY_TOX) and selectivity of the TOX catalyzed by ZSM-5 zeolites are relatively low at present. [Ga, Al]-MFI zeolites containing different Ga/Al atomic ratios were used as catalysts for reaction of synthetic TOX. The structural information of the materials was illustrated by characterization through XRD, ICP-OES, XPS, SEM, BET analysis, and MAS NMR spectroscopy. And the acid properties of the materials were tested by NH₃-TPD and Py-IR. The catalytic performance test showed that the STY_TOX of [Ga, Al]-MFI-50 is about twice that of ZSM-50 or [Ga]-MFI-50. And the selectivity of TOX is also significantly improved compared to that with [Al]-MFI-50 and Ga-MFI-50. This is because the introduction of Ga atoms into ZSM-5 causes the Brønsted acid content to rise, resulting in STY_TOX. It is worth noting that adjusting the Ga/Al atom ratio in the framework affects the B/L value of the zeolite, which leads to the optimization of the selectivity.