Kinetic Evaluation of Cyclopentane as a Promoter for CO₂ Capture via a Clathrate Process Employing Different Contact Modes

Abstract

In order to mitigate global warming with growing demands on fossil fuels, it is essential to reduce CO2 emissions from the energy sector. Hydrate-based CO2 capture from fuel gas mixture (40% CO2/60% H2) is one of the options to reduce the carbon footprint of power plants. This work employed cyclopentane (CP) as a promoter and investigated the kinetic performance of CP/CO2/H2 hydrate formation with two different contact modes using an unstirred tank reactor (UTR) and a fixed bed reactor (FBR) at 281.2 K and 6.0 MPa. Repeat cycles were conducted to examine the recyclability of reactants. Compared with UTR, FBR showed a higher hydrate formation rate and improved the gas uptake by enhancing the dissolution phase. A distinctive two-stage hydrate growth was observed in UTR. Morphology observations were coupled with kinetic data to present the characteristic growth behavior of CP/CO2/H2 hydrate. Furthermore, the scalability of the hydrate formation process was examined. A FBR approach employing a tray column design (three trays) was developed to scale up the bed size without sacrificing the overall kinetics. Lastly, the effect of vacuum on gas recovery from hydrate dissociation was studied, and a CO2 composition enrichment as high as 97.9% was achieved. Overall, the high gas uptake and high CO2 content enriched show the advantages of employing FBR for CP/CO2/H2 hydrate formation. However, one major challenge to be addressed is to avoid the loss of CP between repeat cycles caused by its volatile nature.