En route to the industrial applications of ionic liquids for metal oxide production and biomass fractionation: A sustainable avenue to advanced materials

In the context of climate change, it is essential to use renewable materials and to reduce the environmental footprint of industrial processes. This work focuses on the feasibility of implementing a low-cost Ionic Liquid (IL) in a large-scale biorefinery for bioethanol production (the ionoSolv process). The selected feedstock was Eucalyptus red grandis, a fast-growing hardwood. The lignocellulosic biomass was fractionated at laboratory scale, using aqueous N,N,N-trimethylammonium hydrogen sulfate (20 wt% water), at different temperatures and reaction times, to maximize glucose recovery (86%). Experiments under CO2 atmospheres (sub and supercritical) revealed that the ionoSolv process is pressure insensitive. A detailed Techno-Economic Analysis (TEA) for a biorefinery using the ionoSolv pretreatment was performed and compared to one using the acid-catalysed steam explosion pretreatment. With the ionoSolv pretreatment, the composition of the cellulose-rich pulps can be tailored and high-purity lignins can be recovered. The economic performance of both pretreatments are similar. From a sustainability perspective there are trade-offs: the ionoSolv process consumes 25% more energy (with potential for optimization) but consumes less chemicals and produces less waste. These results indicate that this process can be a competitive alternative. During the development of this process, and other IL-based processes, the interaction of ILs (neat and aqueous) with metals was investigated to establish suitable materials of construction. It was observed that the corrosion behaviour of metals exposed to ILs is system dependent. Surprisingly, water can act either as a corrosion inhibitor or promoter. A semi-quantitative classification method for the different corrosion behaviours observed was developed. Some metals exposed to aqueous ILs formed particles, resulting in the inadvertent development of a novel process for metal-based materials at large-scale: Oxidative Ionothermal Synthesis (OIS). A high-level TEA suggests that OIS offers economic and environmentally advantageous production of bulk and advanced metal-based materials, such as zinc oxide.Open Acces