Acetal isopropilidênico da xilose como plataforma química para a produção de hidrocarbonetos verdes aplicáveis como combustível utilizando hidroconversão na presença de catalisadores de Paládio e Cobre suportados em zeólitas.

Abstract

Green-hydrocarbon production from second-generation biomass using standard refinery is an approach that can shorten the path to environmental sustainability. However, the properties of biomass are not suitable for refinery conditions. One approach to achieve this goal could be the transformation of sugarcane bagasse, by the combination of acid hydrolysis and acetalization, into a stable bio-crude composed by ketal-sugar derivatives. Herein, we carried out the conversion of a representative compound of this bio-crude, 1,2:3,5-di-O-isopropylidene-α-D-xylofuranose (DX) into typical fixed bed (350 ºC, 50 bar H2) and batch (250 ºC, 40 bar H2) hydroprocessing conditions. In fixed-bed conditions, a 20% DX/n-hexane mixture was converted using palladium supported on different zeolites (HUSY, HY, HBEA and HZSM-5). It was obtained mainly saturated hydrocarbons and their formation was sensitive to the catalyst. Pd/HBEA and Pd/HZSM-5 were less prone to coke formation and a C7+ hydrocarbons yield of 10% was obtained using Pd/HZSM-5. Under batch conditions, a 14,3%DX/n-hexane mixture was converted using Pd/HZSM-5 and the effect of reaction time, catalyst reduction and feed/catalyst ratio were analyzed. From these tests, a reaction time of 24 h, pre-reduction of catalyst and a feed/catalyst ratio of 1/1 showed better results and a C7+ hydrocarbons yield of 41% was obtained. The addition of Cu to the catalyst slightly increased the production of C7+ hydrocarbons, however, that was not observed with increasing Cu content. The support mesoporosity effect was evaluated and a C7+ hydrocarbons yield of 46% was obtained using Pd/mesoporous HZSM-5. Since no oxygenated products were observed and the amount of CO, CO2 and coke formed was low, a drop-in fraction was obtained. Moreover, almost full use of the DX molecule was achieved concerning the formation of light and heavy hydrocarbons. Additionally, the diversity of products (paraffins, naphthenes, aromatics, polyaromatics, among others) showed the potential of DX molecule as a platform chemical for the most diverse applications, especially, as fuel. Lastly, the bio-crude was converted under the same batch conditions as DX and similar products were obtained.