The removal of carbon dioxide at production wells from natural gas containing 27 vol% CO2

at 25 °C and 6.5 atm total pressure is to be accomplished by solvent absorption using a 3.6 M

(~30 wt%) solution of piperidine (C5H11N), a heterocyclic secondary amine. Assume that the

natural gas is a binary mixture of carbon dioxide and methane (CH4).

(a). Estimate the diffusivity (cm2/s) of CO2 in the CO2 – CH4 gas mixture at these conditions

using the method of Chapman and Enskog.

(b). Estimate the diffusivity (cm2/s) of CO2 in the piperidine solution at these conditions

using the Wilke-Chang correlation, assuming a molar volume of 34.0 cm3/mol for the

dissolved CO2, and a viscosity μ = 3.1 centipoise and association parameter f = 2.4 for

the solvent.