Producing the optimum PEI

The key variables regarding optimisation of the composition of PEI for CO2 capture are the molecular mass (MM) and the extent of alkoxylation of the primary amine functionalities.  Previous work identified that a PEI MM of 5000 MM was optimal for avoiding any loss of low MM oligomers during continuous operation whilst not increasing PEI solution viscosity to the extent that large excesses of water were required for silica impregnation (Kim et al., 2019).

Reacting the primary amines has the advantages of reducing the extent of oxidation and the heat of adsorption for CO2, but it does lead to some loss in CO2 uptake.  The challenge is to identify the optimal extent of alkoxylation which will minimize PEI replacement costs and the regeneration energy for CO2 desorption without reducing CO2 adsorption capacity significantly.

The cost-performance relationship for different alkylene oxides as a function of their ratios to the primary amine groups will be established and the findings, together with the performance of an alkoxylated PEI in the pilot-scale studies will feed into the techno-economic analysis to calculate the adsorbent replacement cost.  Having established this relationship from the lab-scale tests, pilot scale quantities of the optimal PEI, will be prepared, and the production process evaluated confirming commercial production.