Carbon Molecular Sieve Membranes for nitrogen separation from natural gas

  • Shaihroz Khan

Student thesis: Master's Thesis

Abstract

Carbon Molecular Sieve Membrane (CMSM) is derived from the pyrolysis of polymeric precursors. It possesses good mechanical strength, inert surface chemistry, and above all, high permeability and selectivity. It is one of the ideal candidates for the purification of natural gas (NG). This project aims at the removal of N2 out of NG stream by using membrane technology. It compares favorably to the traditional method of cryogenic distillation at about -180 °C, which is energy intensive and costly. This project conducted such tasks as: synthesizing CMSM from selected polymeric precursors under different pyrolytic conditions (3 membrane samples), membrane characterization, setting up & calibrating the permeation rig, as well as the gas permeation experiments. It was found that increasing the upstream permeation pressure increases the flux of all the gases permeating through the membrane because of the increase of the chemical potential gradient, but reduces the selectivity. For N2/CH4 gas pair, CMSM 700 at 20 °C showed a good perm-selectivity of ~ 40.35 with N2 permeability of 5.75 Barrer and CH4 permeability of 0.145 Barrer at 250 KPa. The membrane is working more on sieving mechanism than surface diffusion mechanism. This qualifies CMSM 700 for N2 permeable/selective membrane [1]. For CO2/CH4 gas pairs, CMSM 600 showed very good selectivity of 321.30 (which decreases with pressure) and CO2 and CH4 permeability of 830.76 and 2.65 Barrer, respectively at the permeation temperature of 20 °C. CMSM 700, on the other hand, demonstrated a selectivity of 1326.31, with a CO2 permeability of 187.71 Barrer and CH 4 permeability of 0.14 Barrer. In summary, CMSM demonstrated superior separation performance for the purification of impurities such as N2 and CO2, in natural gas as studied in this work with good separation performance for both species.
Date of Award2016
Original languageAmerican English
SupervisorKean Wang (Supervisor)

Keywords

  • Applied sciences
  • Carbon dioxide
  • Cmsm
  • Gas separation
  • Methane
  • Nitrogen
  • Chemical engineering
  • 0542:Chemical engineering

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