Abstract
Novel spherical molecularly imprinted polymer (MIP) particles containing amide-decorated nanocavities with CO2 recognition properties in the poly[acrylamide-co-(ethyleneglycol dimethacrylate)] mesoporous matrix were synthesized by suspension polymerization using oxalic acid and acetonitrile/toluene as dummy template and porogen mixture, respectively. The particles had a maximum BET surface area, SBET, of 457m2/g and a total mesopore volume of 0.92cm3/g created by phase separation between the copolymer and porogenic solvents. The total volume of the micropores (d<2nm) was 0.1cm3/g with two sharp peaks at 0.84 and 0.85nm that have not been detected in non-imprinted polymer material. The degradation temperature at 5% weight loss was 240–255°C and the maximum equilibrium CO2 adsorption capacity was 0.56 and 0.62mmol/g at 40 and 25°C, respectively, and 0.15bar CO2 partial pressure. The CO2 adsorption capacity was mainly affected by the density of CO2-philic NH2 groups in the polymer network and the number of nanocavities. Increasing the content of low-polar solvent (toluene) in the organic phase prior to polymerization led to higher CO2 capture capacity due to stronger hydrogen bonds between the template and the monomer during complex formation. Under the same conditions, molecularly imprinted particles showed much higher CO2 capture capacity compared to their non-imprinted counterparts. The volume median diameter (73–211μm) and density (1.3g/cm3) of the produced particles were within the range suitable for CO2 capture in fixed and fluidized bed systems.
Highlights
Excessive concentration of atmospheric CO2, mainly because of extensive utilization of fossil fuels, has significantly contributed to global warming and requires immediate remedies [1,2]
Production and characterization of particles In O/W suspension polymerization, the organic phase, containing the template, the monomer, the cross-linker, and the initiator dissolved in the solvent(s), is dispersed in the aqueous surfactant solution
Novel molecularly imprinted poly(AAm-co-Ethylene glycol dimethacrylate (EGDMA)) spherical particles were synthesized by suspension polymerization in an oil-in-water emulsion and used for CO2 adsorption from a CO2/N2 gas mixture
Summary
Excessive concentration of atmospheric CO2, mainly because of extensive utilization of fossil fuels, has significantly contributed to global warming and requires immediate remedies [1,2]. Metal organic frameworks (MOFs) have gained a lot of interest because of their high specific surface area, ease of structural tuning, narrow pore size distribution, and high CO2 adsorption at elevated pressures [34] They mostly suffer from low CO2 adsorption at low pressures [35,36], low CO2 selectivity, and significant deterioration in the presence of moisture, NOx and SOx [20,37]. In suspension polymerization each monomer droplet acts as a tiny batch reactor, which facilitates heat transfer and the polymerization occurs faster and the final conversion of the monomer can reach higher values [50] Due to their spherical shape, the particles have a lower tendency to break down and their size can be finely tuned by controlling the operating conditions and phase compositions during emulsification [50]. The emulsion formulation and operating conditions were optimized to maximize CO2 adsorption capacity of the particles in realistic post-combustion CO2 capture situations
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