Alternative technologies for the selective conversion of bio-based feedstocks to specialty chemicals
Dr François JEROME
Institut de Chimie des Milieux et Matériaux de Poitiers
With the growing concerns of our society about climate change, a strong political impulsion has been given to the defossilization of our industry. In this context, the production of chemicals from biomass waste has become of particular interest. Biomass waste is mainly composed of sugars. In the context of chemicals manufacturing, the activation and conversion of sugars at low temperatures is mandatory. Indeed, at temperatures higher than 100°C, sugars are readily degraded in an uncontrolled way, thus lowering the selectivity and reactor productivity but also rapidly deactivating catalysts. Being able to convert (selectively) concentrated feed of biomass to a targeted chemical is a challenging and difficult scientific task that will be partly addressed in this lecture.
First, we will focus on the synthesis of relevant renewable aromatics from bio-based furfural derivatives and cheap alkenes, through a Diels-Alder/aromatization sequence. The prediction and the control of the ortho: meta selectivity in the Diels-Alder step was achieved through a combined experimental-theoretical approach. In particular, we will show that the ortho: meta selectivity at the reaction equilibrium stems from a subtle interplay between charge interactions, favoring the ortho products, and steric interactions, favoring the meta isomers.
In a second part, we will show that the massive electrification of our society now opens new rooms for the development of alternatives technologies, in particular to access biobased chemicals that are hardly obtainable with traditional routes. We will illustrate it through the synthesis of biosurfactants directly from recalcitrant cellulosic biomass. The proposed process, named mechanocatalysis and firstly introduced by Blair and Rinaldi, is based on a synergistic effect between an acid catalyst and mechanical forces. The impact of water and minerals present in biomass on the mechanocatalytic process efficiency will be discussed as well as a life cycle assessment to shed light on the contribution of this technology as compared to the current industrial process. Turning now to reactions in water, an essential solvent for biomass, we will highlight the contribution of ultrasound for the catalyst free biomass processing. We will show that high frequency ultrasound is capable of generating •OH radicals (homolytic dissociation of water inside cavitation bubbles), and thus to initiate chemical reactions at a nearly room temperature with sugars. Transposition of this technology for the activation and conversion of NH3 (future H2 carrier) will be also discussed, particularly for the metal free hydrogenation of biobased alkenes in water.