PhD Defence Balaji Sridharan: Catalytic conversion of lignocellulosic biomass to biofuels and bio-based chemicals using molten salts

Promotors: Prof. dr. ir. H.J. (Hero Jan) Heeres, Dr. R. Venderbosch

Abstract: The challenge of reducing the use of fossil resources while satisfying the increasing global demand for energy and reducing its environmental impact is one of the sternest issues facing the world today. In this context, lignocellulosic biomass is envisioned to play a crucial role in the transition away from existing petroleum-based industry as a source of sustainable carbon for the production of both chemicals and fuels. Various thermochemical process routes to convert biomass and particularly technical lignins to biofuels and biobased platform chemicals have been demonstrated at low TRL levels in the past few years. However, the scale up of such processes is often hindered by techno-economic hurdles, which currently limit their large-scale implementation. Low final product yields and the use of expensive catalysts in combination with its deactivation make these processes less competitive when compared to conventional fossil-based process routes. To overcome these challenges, a multi-step ABC-process was developed in this thesis. The ABC-salt approach utilizes relatively inexpensive alkali based molten salt mixtures to depolymerize biomass to liquids which is then upgraded to biofuels via catalytic hydrotreatment. Within this thesis, two different biomasses: pinewood and kraft lignin, were successfully converted to hydrotreated biofuels using both batch and continuous experimental setups. Process metrics such as overall liquid yields and carbon yields calculated helped benchmark the ABC-salt process to comparable processes reported in literature. The development of the concept over the course of this thesis culminated in a 100-hour demonstration of the process to continuously convert kraft lignin to biofuels with an overall liquid yield of 70 wt% (88 % carbon yield). The promising results reported here demonstrate an efficient and scalable process that will help the valorisation of biomass towards sustainable biofuels and chemicals.

Dissertation