Capture of carbon dioxide using solid carbonaceous and non-carbonaceous adsorbents: a review

Abstract

Petroleum products have assisted human advancement, yet massive carbon dioxide (CO2) emissions are inducing global warming, thus calling for advanced techniques of CO2 separation and capture. Here we review carbonaceous and non-carbonaceous solid adsorbents, owing to their lower cost, higher energy efficiency and easier regenerability versus solvent-based adsorbents. We present thermal and chemical activation methods. Carbonaceous adsorbents such as activated carbon and carbon nanotubes have tunable surface properties, low moisture sensitivity and high thermal stability. Adsorption on solid adsorbents is mainly explained by thermodynamic, molecular sieving and kinetic mechanisms. Optimum adsorption is done below 70 °C for all adsorbents. Non-carbonaceous adsorbents such as zeolites and metal–organic frameworks have high CO2 uptake capacity, yet they are costly and highly moisture sensitive. This uptake capacity is explained by the suitable channel diameter of zeolites (0.3 - 1.0 nm) for effective capture of the CO2 molecule (0.33 nm). Metal–organic frameworks are a new class of efficient adsorbents but have drawbacks such as complex synthesis, high cost and higher sensitivity towards moisture and temperature. Metal oxide-based solid adsorbents have higher adsorption capacity owing to their high porosity, favourable porous structure, high stability and specific surface area. Solid adsorbents can be modified by reagents such as amines, potassium hydroxide and urea or by thermal treatment. In particular, the impregnation of polyethylenimine on solid adsorbents is more stable.