A resorcinol-formaldehyde precursor was synthesized to fabricate the CO2 selective Carbon Molecular Sieve Membranes (CMSMs) developed in this study. The degree of polymerization (DP) was analyzed via Gel Permeation Chromatography (GPC) and its effect on the CO2/N2 perm-selectivity and CO2 permeance was investigated. The membrane that was polymerized at 80 °C (named R80) was selected as the best performing CMSM after a preliminary test. The post treatment with oxidative atmosphere was performed to increase the CO2 permeance and CO2/N2 perm-selectivity on membrane R80. The gas permeation results and Pore Size Distribution (PSD) measurements via perm-porometry resulted in selecting the membrane with an 80 °C polymerization temperature, 100 min of post treatment in 6 bar pressure and 120 °C with an oxygen concentration of 10% (named R80T100) as the optimum for enhancing the performance of CMSMs. The 3D laser confocal microscopy results confirmed the reduction in the surface roughness in post treatment on CMSMs and the optimum timing of 100 min in the treatment. CMSM R80T100 exhibiting CO2/N2 ideal selectivity of 194 at 100 °C with a CO2 permeability of 4718 barrier was performed higher than Robeson’s upper bound limit for polymeric membranes and also the other CMSMs fabricated in this work.
Membrane technology is considered a high-efficiency separation
and purification technology due to its low carbon footprint and low
energy consumption. In this work, carbon molecular sieve (CMS) membranes
for the selective separation of CO2 from methane and nitrogen
were successfully fabricated. A gas permeation setup was employed
to test CO2/N2, CO2/CH4 perm-selectivities, and CO2 permeances of the CMS membranes.
To study the impact of temperature and pressure, the experiments have
been carried out at a temperature range from 20 to 350 °C and
pressure from 1 to 40 bar. Furthermore, a novel multistage membrane
process design was proposed to test the feasibility of the fabricated
membranes for CO2 separation from different sources of
carbon emission. Three major sweetening processes are considered,
including CO2 capture from coal-fired flue gas, biogas
upgrading (BG), and natural gas (NG). A structural optimization approach
is applied to determine the most efficient membrane strategy from
the point of view of gas separation cost. By varying the membrane
properties and separation targets, the effect of these parameters
on capital expenditure (CAPEX), operating expenditure (OPEX), and
energy consumption was studied. The economic assessment revealed a
superior potential for CO2/N2 separation with
a capture cost of 41.8 €/ton of CO2 and energy consumption
of 1.9 GJ/ton CO2. The use of the optimal two-stage membrane
configuration resulted in a competitive CO2/CH4 separation cost of 4.2 €/ton of sweet NG and 23 €/ton
of BG for natural gas and biogas upgrading, respectively.
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