• Energy Research

In recent years, the urgency to replace fossil-based resources by renewable biomass for obtaining chemical building blocks has only increased. Carbohydrate-derived furanic compounds are regarded as promising platforms for a renewable value chain. The high reactivity of such biobased intermediates requires the development of novel catalytic chemistry to enhance product yield. The protection of reactive functional groups provides a way to improve the product selectivity. Such protection strategies are common practice in the synthesis of fine chemicals and pharmaceuticals but are not fully explored for the conversion of furanic compounds. In this perspective, several examples of protection strategies focusing on the selective passivation of 5-HMF are discussed. Formation and removal of these protection groups are highlighted as well as the application of the neutralized 5-HMF in further processing. A guide for selecting the appropriate protection strategy depending on the targeted chemistry and operating conditions is provided.

Aromatization of furan and substituted furans over zeolite catalysts is a promising reaction to convert cellulose-derived compounds into valuable aromatic hydrocarbons and light olefins. A lack of understanding of the reaction mechanism however hinders further development of this process. Here, we propose the reaction mechanism, underlying the chemistry of furan and methanol co-aromatization over HZSM-5 zeolite catalyst. Applying 13C isotope labeling in a combination with NMR spectroscopy and high temporal resolution gas chromatography-mass spectrometry analysis, we demonstrate that aromatization of furan and methanol are not mechanistically separated and can be described within the dual-cycle hydrocarbon pool mechanism. Cofeeding furan with methanol leads to a significant enhancement of light aromatics selectivity and increased catalyst lifetime.

The development of novel technologies to convert renewable biomass feedstocks to fuels and chemicals is of increasing interest for making our chemical industry more sustainable. Plant biomass or its biomass-derived platform molecules are typically over-functionalized, requiring substantial modification to produce the chemicals currently demanded by industry. Furanic compounds are intermediates in the catalytic fast pyrolysis of lignocellulosic biomass or sugar dehydration and can in principle be further converted to aromatics. While upgrading of furanics by zeolite-catalysed aromatization typically results in a large loss of carbon due to coke deposition, carbon laydown can be mitigated by the addition of ethylene and by the modification of the zeolite with Lewis acid Ga sites. Here, we investigate the influence of the Ga loading on the physicochemical properties of Ga-modified HZSM-5 zeolite and its performance in the gas-phase aromatization of 2,5-dimethylfuran with ethylene. Characterization of the morphological, textural and acidic properties were carried out to understand the role of Brønsted and Lewis acid sites on the catalytic reaction. We demonstrate a crucial role of the dispersion of Ga-species and the resulting Lewis acidity of the Ga/ZSM-5 catalysts; and show means how to control both parameters by adjusting the synthesis method.