Performance Studies of Novel Amine Blends in a Catalyst-Aided CO2 Capture Process

Abstract

This study focused on utilizing the combined effect between solvent development and the application of solid catalysis to enhance the reactive absorption-based CO2 capture process. First, the CO2 removal performance of three formulated amine bi-blends were evaluated using a semi-batch screening setup. The performance of each blend in terms of specific parameters such as linear absorption and desorption rates, CO2 equilibrium loading, cyclic capacity and solvent regeneration heat duty were compared with the activity of the standard 4M BEA/AMP blend. The bi-blends developed included 2M HMDA/PEI (1.85M: 0.15M), 2M AMP/PEI (1.7M: 0.3M) and 4M DMAE/AMP (2M: 2M). The screening results showed that by reason of higher reactivity resulting from increased number of amino groups in HMDA and PEI, better absorption performance was observed for 2M HMDA/PEI and 2M AMP/PEI bi-blends. However, from the absorption parameter and desorption parameter criterion, 4M DMAE/AMP was found to be the optimum bi-blend amongst the three blends. In addition, the effects of solid alkaline and acid catalysts on the CO2 absorption and desorption performance of the selected optimum blend were studied. Also, the different characteristics of the catalysts were investigated and related to the corresponding enhancement activity to identify and establish the activity-characteristics relationship. Employing the acid proprietary desorber catalyst (AD-1) increased the linear desorption rate and cyclic capacity of 4M DMAE/AMP by 21% and 8.1% respectively and reduced the solvent regeneration energy requirement by 17.3%. Between the absorber catalysts, an increase of 33.3% and 29% in absorption rates were measured for ACS and AB-1 respectively. Comparing the activity of ACS to AB-1, it was observed that the activity of catalyst depends on both the chemical properties (strength and number of basic sites) and physical properties (surface area and pore volume). Furthermore, a full cycle operation in a bench-scale CO2 capture unit was carried out to validate the performance of 4M DMAE/AMP and 2M HMDA/PEI bi-blends. The performance was evaluated as a function of time-on-stream. From the cyclic runs, higher CO2 absorption and desorption performance parameters were recorded for 4M DMAE/AMP relative to the 2M HMDA/PEI blend. The time-on-stream analysis revealed a general reduction in capture performance and an increase in heat duty for both bi-blends.