Efficient CO2 Capture from a Simulated Shale Gas using Tetra-n-butylphosphonium Bromide Semiclathrate Hydrate

Abstract

In this work, tetra-n-butylphosphonium bromide (TBPB) semiclathrate hydrate was employed to capture CO2 from a simulated shale gas (40 mol% CO2/CH4) for the first time. New liquid-hydrate-vapor phase equilibrium data at 5, 10, and 20 wt% TBPB were experimentally determined and reported. Hydrate formation kinetics and CO2 separation efficiency at different TBPB concentrations were studied at a fixed initial pressure of 2.8MPa with the temperature varying from 278.1K to 283.4K. The results indicated that 20 wt% TBPB solution was more favorable for CO2 separation compared to 5 and 10 wt% TBPB solutions as the largest separation factor (29.3) was obtained. The preferential enclathration of CO2 into the TBPB semiclathrate hydrate indicates that the hydrate-based CO2 capture from the CO2/CH4 gas mixture is more efficient in the presence of TBPB as compared to that in the presence of tetrahydrofuran (THF).