Humidity as a method for controlling CO2 adsorption with step-shaped adsorbents

A method for removing CO2 from an effluent gas stream, the method comprising:

• (a) contacting the effluent gas stream with an adsorption material located within an adsorption system to reversibly adsorb CO2 from said effluent gas stream thereby generating an adsorption material with improved CO2 capacity;
• wherein said adsorption material is an amine-functionalized solid sorbent comprising an amine-appended metal-organic framework composed of a plurality of
• (i) amine-containing ligands;
• (ii) polytopic organic linkers;
• and
• (iii) metal ions;
• wherein said amine-functionalized solid sorbent is present in the form of a packed bed of solids selected from particles, granules, agglomerates thereof, and combinations thereof;
• wherein said improved CO2 capacity is achieved by means of pre-saturating said adsorption material using water vapor prior to contact with said effluent gas stream;
• (b) removing a major portion of the CO2 from said effluent gas stream to generate a treated effluent gas stream exiting said adsorption system;
• and
• (c) retaining said major portion of said CO2 on said amine-functionalized solid sorbent prior to a regeneration process to renew said adsorption material;
• wherein said means of pre-saturating said adsorption material is achieved by means of a humidification unit that functions to control the amount of water present within said adsorption material, and
• wherein the method further comprises measuring a relative humidity level of the treated effluent gas stream exiting the adsorption system to obtain a measured relative humidity of the treated effluent gas stream;
• and
• based on the measured relative humidity of the treated effluent gas stream, changing the temperature of the incoming effluent gas stream, changing the velocity of said incoming effluent gas stream, or changing the temperature of the adsorption material to maintain a humidity level within said adsorption material at an optimum level during usage, and
• wherein the optimum level in the adsorption material is a relative humidity with respect to water present on said amine-functionalized solid sorbent, and the optimum level corresponds to between 1.5 and 3.5 mole percent H2O.