The Synergistic Effect of Acidic Properties and Channel Systems of Zeolites on the Synthesis of Polyoxymethylene Dimethyl Ethers from Dimethoxymethane and Trioxymethylene

Abstract

A series of zeolites with different topology structures, including SAPO-34, SUZ-4, ZSM-5, USY, MOR, and beta, were used to synthesize polyoxymethylene dimethyl ethers (PODEn) from dimethoxymethane (DMM) and trioxymethylene (TOM). The influence of acidic properties and channel systems were studied by activity evaluation, characterization, and theoretical calculation. The results confirmed that pore mouth diameter larger than a TOM molecule was an essential prerequisite for the synthesis of PODEn over zeolites, and the synergistic effect between medium-strong Brønsted acid sites (Brønsted MAS) and the maximal space of zeolites available determined the catalytic performance of all studied zeolites. DMM and TOM were firstly decomposed into methoxymethoxy groups (MMZ) and monomer CH2O over Brønsted MAS. Subsequently, the steric constraint of the maximum included sphere, with an appropriate size in zeolite channels, can promote the combination of CH2O and MMZ to form transition species ZO(CH2O)nCH3, which reacted with the methyl-end group to form PODEn over Brønsted MAS. Moreover, the reaction temperature showed different effects on the product selectivity and distribution, which also mainly depends on the size of the maximum space available in zeolite channels.

Continuous Synthesis of Oxymethylene Ether Fuels from Dimethyl Ether in a Heterogeneously Catalyzed Liquid Phase Process

“…In a study of Wu et al, SAPO-34 has been unsuccessfully employed for OME synthesis from DMM and TRI. This has been attributed to a molecular size of more than 4 Å for TRI, impeding access to the pore channels due to steric hindrance [43]. In the case of ZSM-22 and ZSM-23, small pore diameters of about 4.5 Å might be the reason for the lack of catalytic activity.…”

“…Previous work indicated activity of such catalysts in the context of OME formation from OME 1 and TRI as well as paraformaldehyde and alcohols [39,40]. Additionally, various zeolites have been tested for OME synthesis from OME 1 and TRI [41][42][43][44]. Since zeolites are very versatile materials in terms of adjustable acidity as well as morphologic properties while also being very stable and recyclable, they represent a promising and costefficient class of catalysts for the production of synthetic fuels [41,45].…”

Irreversible Bildung von Nebenprodukten bei der Synthese von Poly(oxymethylen)dimethylethern

“…Dies kann einem autokatalytischen Effekt zugeschrieben werden, da zunehmende Mengen an Ameisensäure als Katalysator für die Bildungsreaktion wirken 31. Dies stimmt mit der Literatur überein, da stark saure Katalysatoren eine verstärkte Methylformiatbildung zeigten 18–21. Allerdings ist der Effekt auf nur zwei der vorliegenden Experimente begrenzt, weshalb eine zuverlässige Modellierung der Autokatalyse nicht möglich ist.…”

“…In der Literatur ist die Bildung von Nebenprodukten bei der OME‐Synthese mit verschiedenen Ausgangsstoffen und Katalysatoren umfangreich beschrieben 8, 12, 13, 18–21. Darin werden vor allem die Stoffe Methylformiat, Ameisensäure, Dimethylether und Trioxan genannt.…”

Advances in Heterocatalysis by Nanomaterials

“…Wu et al [22] investigated a series of zeolites with different topology structures, including SAPO-34, SUZ-4, ZSM-5, USY, MOR, and beta, as catalysts for the synthesis of polyoxymethylene dimethyl ethers (PODEn) from dimethoxymethane (DMM) and trioxymethylene (TOM). Both experimental and theoretical studies were employed to evaluate the influence of acidic properties and textural/morphological characteristics of the zeolites on their activity.…”