Low Energy Penalty Solvents

Target: Among the carbon capture technologies closest to implementation, post combustion capture (PCC) and industrial source capture based on CO2 absorption into reactive liquids is the most mature, but still shows a large improvement potential. The main challenges are energy requirement and possible emissions. A break-through on these issues requires deep molecular structure-property based understanding of the most promising current solvent system combined with transposition of this knowledge into novel chemistry. This project aims at understanding the underlying chemistry of the exceptional performance of the empirical developed DEEA/MAPA solvent blend. In spite of intense improvement focus, the DEEA/MAPA performance has so far not been surpassed. Project scope: Once the underlying chemistry of the DEEA/MAPA solvent blend is understood we will use this understanding to develop even better solvents e.g. having the combined properties of low heat of reaction (60-65 kJ/mol CO2), high temperature sensitivity allowing stripping at elevated pressure (10-20 Bar) or low temperature (60-90 oC) and good cyclic capacity. For this purpose we will use NMR (1H, 13C, 15N, etc) spectroscopic solvent analysis combined with selected solvent characterization methods (performance screening, VLE, kinetics). The challenge is to understand and predict performance-structure properties of amines and amine blends. Although a wealth of empirical work is reported, systematic studies on physical chemical understanding are scarce. Impact: If we succeed, we will achieve a real break-through in solvent technology. Project results: Literature review (DEEA, MAPA as reference baseline) identified an initial systematic experimental series of tertiary amines and amine promoters (structure, pKa values) for CO2 screening work (loading 40 °C, stripping 80 °C) at various amine ratios and concentrations. CO2 absorption capacity, cycling capacity, pKa data in addition to NMR solvent speciation information were acquired. The role of the tertiary amines in the MAPA blend including the optimum tertiary amine - MAPA pKa-range was identified. The amine reactions in the blend influence each other both for CO2 loading and stripping. Preliminary screening tests of alternative MAPA promotors in the DEEA blend in combination with NMR speciation analyses identified an initial tertiary amine structure-property relationship. Furthermore, solvent studies at various CO2 loading, pH, in combination with NMR derived speciation and determination of heat of CO2 absorption (dH) gave insight into the different reactions going on in the solvent, while explaining the observed pH and dH values on a fundamental level.

Tidlig i prosjektet oppdaget vi at lett tilgjengelig amin syrekonstanten Ka kunne brukes som amin strukturindikator. NMR basert molkylær solvent analyse identifiserte molkylær lav temperatur solvent mekanisme. Amin syrekonstanter i kombinasjon med NMR analyse førte oss frem til delmål a.: "molekylstrukturstruktur-egenskaps relasjon for lav temperatur CO2 fangstsolventer". I tillegg fikk vi god reaksjonsmekanistisk innsikt i DEEA/MAPA system. På basis av denne innsikten identifiserte vi tre nye MAPA baserte lavtemperatur solventer. Alle viste like lovende egenskaper som DEEA/MAPA. Delmål b. "å identifisere og karakterisere et lav kvalitets varme drevet CO2 fangstsolvent system" ble dermed nådd. Vi erfarte at det er vanskelig å overgå DEEA/MAPA solvent, men innsikten generert i prosjektet viser en retning for videre arbeid. Et eksempel av dette er pKa relasjon av aminene brukt i blandingen.

Among the carbon capture technologies closest to implementation, post combustion capture (PCC) and industrial source capture based on CO2 absorption in liquids is the most mature, but still shows a large improvement potential. The main challenges for PCC are energy requirement and possible emissions. A break-through on these issues requires deep molecular structure-property based understanding of the most promising current solvent system combined with transposition of this knowledge into novel chemistry. This project aims at understanding the mechanisms behind the special DEEA/MAPA performance. Our hypothesis is that the promising properties of this de-mixing solvent system could be due to formation of an ionic liquid (or ionic liquid-like) phase influencing CO2 reactivity through the specific solvent structure. Once we have understood the de-mixing solvent systems, we will use this understanding to develop even better solvents e.g. having the combined properties of low heat of reaction (60-65 kJ/mol CO2), high temperature sensitivity allowing stripping at elevated pressure (10-20 Bar) or low temperature (60-90C) and good cyclic capacity. For this purpose we will use NMR (1H, 13C, 15N, etc) spectroscopic solvent analysis combined with targeted characterization of the solvents (performance screening, VLE, kinetics). If we succeed, this will imply a real break-through in solvent technology.