The combination of 1-octyl-3-methylimidazolium tetrafluorborate with TBAB or THF on CO2 hydrate formation and CH4 separation from biogas

摘要

[C8min] BF4 was used in this work to combine with TBAB or THF for the investigation about thermodynamic and kinetic additives on CO2 and CH4/CO2 hydrates. The results show that [C8min] BF4 has the inhibition effect on the equilibrium of hydrate formation. About the kinetic study, [C8 min] BF4 could improve the rate of CO2 hydrate formation and increase the gas uptake in hydrate phase. At the same time, the combination of TBAB and [C8 min] BF4 could increase the mole friction of CH4 in residual gas comparing with the data in THF solution. CH4 separation efficiency was strongly enhanced. Since that the size of CO2 and CH4 molecules are similar, CH4 and CO2 could form the similar hydrate, so the recovery of CH4 from biogas decreases lightly. The CH4 content in biogas can purified from 67 mol％ to 77 mol％ after one-stage hydrate formation. In addition, the combination of THF and[C8 min] BF4 do not have obvious promoting effect on CH4 separation comparing with the gas separation results in pure THF solution.