Ethanol to Aromatics on Modified H‐ZSM‐5 Part I: Interdependent Dealumination Actions

Influence of ZSM-5 Crystal Size on Methanol-to-Olefin (MTO) vs. Ethanol-to-Aromatics (ETA) Conversion

Crystal size is a key parameter of zeolites applied as catalysts. Herein, ZSM-5 crystals with similar physicochemical and acid properties, few defects, and aluminum exclusively in tetrahedral coordination are synthesized and the influence of the crystal size on the MTO and ETA conversion is investigated. Short olefins are the main products of the MTO conversion, whereas larger olefins and aromatics dominate the products after ETA conversion. In the case of both feeds, an increased crystal size decreases the catalyst's lifetime. The MTO conversion over larger ZSM-5 altered the product distribution, which was not the case for the ETA conversion. The reason is that the instantly available aromatics during ETA conversion lead to fast coking and zeolite crystals only active in the outer layers. Thus, the different reactivity of different-sized ZSM-5 is direct proof of a different conversion mechanism for both alcohols.

Relationship between ZSM-5 pore modifications and gallium proximity and liquid hydrocarbon number distribution from ethanol oligomerization

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Conversion of Oxygenates on H-ZSM-5 Zeolites—Effects of Feed Structure and Si/Al Ratio on the Product Quality

The conversion of different biogenic feedstocks to hydrocarbons is a major challenge when ensuring hydrocarbon and fuel supply in spite of the heterogeneity of this feed. Flexible adaptation to changing compositions is mandatory for the respective processes. In this study, different oxygenate model feeds, such as alcohols, aldehydes, carboxylic acids and esters, were converted at 500 °C and 5 barg H2 using H-ZSM-5 zeolite catalysts with various Si/Al ratios to identify the relationship between the feed structure and the final product distribution. As the main outcome, the product distribution becomes increasingly independent of the feed structure for Al-rich H-ZSM-5 catalyst samples at low Time on Stream (ToS). Some minor exceptions are the increased formation of aromatics during ToS for carbonyl oxygenates compared to primary alcohols and the dominance of initial deoxygenation products for Si-rich H-ZSM-5 samples. This is interpreted by a multi-stage reaction sequence, which involves the initial deoxygenation of the feed and the subsequent integration of the olefin intermediates into a reaction network. The results pave the way towards the achievement of a desired product distribution in the conversion of different oxygenates simply by the adaption of the Al content of H-ZSM-5.