Gallium-promoted HZSM-5 zeolites as efficient catalysts for the aromatization of biomass-derived furans

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.