Abstract
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.
Highlights
With the discovery of zeolite H-ZSM-5 as an acid catalyst, more and more of its applications have been found in the field of catalytic conversion of hydrocarbons [1]
Since the oxygenated feeds differed in the wt.-% of carbon, all catalytic results were presented as carbon yield, which gives the yield normalized to the amount of hydrocarbon CnHm in the oxygenate feed after initial deoxygenation
For all oxygenates, after deoxygenation, an initial olefin distribution forms, which is typical for the respective carbon chain length and type of functional group
Summary
With the discovery of zeolite H-ZSM-5 as an acid catalyst, more and more of its applications have been found in the field of catalytic conversion of hydrocarbons [1]. Powder X‐ray diffraction; analysis of reflexes at 21–26° 2θ according to ASTM D5758‐01, sample with the highest value set tToh1e00d%iff.e3reAnTceR‐inFTth‐IeRA; alncaolnytseinstovfatrhiaetrioantiowoafs acbosnofirrbmaendcebayt I4C5P0-OcmES−1 aanndd TPAD. With respect to thermogravimetry analysis, all samples show similar behavior, with slightly. With respect to thermogravimetry analysis, all samples show similar behavior, with slightly higher hydrophilic behavior in the Al‐rich samples (Appendix B, Figure A2). As a result of the experiments and accompanying analyses, synthesis of H‐ZSM‐5 zeolite samples with comparable textural properties was successful (specific surface area: 395–435 m2/g, pore volume: 0.17–0.19 cm3/g). The dominant size fractions of all samples are very similar, i.e., morphology changes with Al content are not major reasons for changes in catalytic properties, which are the focus of the current work. Al‐rich samples (Z‐35) shift in main particle fraction towards smaller sizes, visible within D50
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