Catalytic conversion of CO2 and biomass-derived phenols to high-value chemicals

The UK has become the first major economy in the world proposing to bring all greenhouse gas emissions to net-zero by 2050. This research project will be dedicated to utilise CO2, the most ubiquitous and potent greenhouse gas in the production of chemical intermediaries for pharmaceuticals and fine chemicals as well as the growing bioplastic industry. A new promising route to produce high value chemicals such as aromatic carboxylic acids (ACAs) via catalytic coupling of biomass derived phenols will be explored. If successful, this project will be a win-win for sustainable development and for the global efforts to mitigate climate change and global warming.
In brief, there are well-established protocols for the preparation of carboxylic acids, however, the most straight forward method for accessing carboxylic acids is through direct carboxylation [1]. The only well-known carboxylation reaction is the Kolbe-Schmitt reaction and it has its own set-backs due to high temperature and pressure requirements [2]. Sadamitsu et al. (2019) managed to achieve the Kolbe-Schmitt reaction at ambient conditions using resorcinol (a phenolic compound) with the addition of an organic base to synthesis the corresponding salicylic acid. However, this type of reaction requires very long residence time and is limited to one specific phenolic compound which restricts the use of biomass derived phenolic compounds. Moreover, the addition of an organic base requires an additional separation stage which can be costly and inefficient at a larger scale. Even though one and a half centuries have passed since the original report, no method has been reported for an efficient carboxylation of phenols. Efforts have only been made for improvement and modification of the original report since 1957 [2].
What makes this research project unique is that it does not focus only on catalytic conversion of CO2, but to further reduce carbon footprint through exploring the options of obtaining phenolic compounds from biomass. The routes that will be explored are, (1) isolation of phenols from biomass pyrolysis oils and (2) production of phenols from hydrothermal liquefaction (HTL) of lignin. The only stumbling block in the use of bio-oils is their separation due to very wide product distributions [4]. Therefore, developing selective catalyst plays an important role in narrowing production distribution, consequently, enables higher yield separation of phenols from biomass. An efficient in-house production process of value-added chemicals through reducing CO2 and the use of green feedstock in production of bio-oil will ultimately allow commercialisation.
This research project aims to revolutionise the growth of the 19th century finding by introducing an optimised alternative production system to the conventional batch process. While continuous processing has the ability to produce safer and more sustainable processes, most manufacturers still rely on batch production. Experimental results from this project will be used to simulate and design a continuous rig. Dessimoz et al. (2012) carried out continuous reaction of the Kolbe-Schmitt reaction under high pressure and temperature using a micro-plant - emphasising on the suitability for efficient control of process parameters due to high mass and heat transfer performance. Micro-capillaries have the limitations of large-scale productions, hence continuous technologies that decouple mixing from the fluid velocities and pressures are required. These will be explored in detail in this project.
References
[1] X. Wu et al.,Top Curr. Chemis, pp. 1-60, 2018.
[2] J. Luo, et al., Chem. - A Eur. J., vol. 22, no. 20, pp. 6798-6802, 2016.
[3] Y. Sadamitsu et. al, Chem. Commun., vol. 55, no. 66, pp. 9837-9840, 2019.
[4] Y. Elkasabi, SN Appl. et.al Sci., vol. 2, no. 3, pp. 1-9, 2020.