Adsorption, Gas Separation

Abstract

Gas‐phase adsorption is widely employed for the large‐scale purification or bulk separation of air, natural gas, chemicals, and petrochemicals. An adsorbent attracts molecules from the gas, and the molecules become concentrated on the surface of the adsorbent and are removed from the gas phase. Most commercial adsorbents for gas‐phase applications are employed in the form of pellets, beads, or other granular shapes, most commonly packed into fixed beds through which the gaseous feed mixtures are passed. The growth in both variety and scale of gas‐phase adsorption separation processes, particularly since 1970, is due in part to continuing discoveries of new porous, high surface‐area adsorbent materials (particularly molecular sieve zeolites) and to improvements in the design and modification of adsorbents. To permit the recovery of pure products and to extend the adsorbent's useful life, adsorbents should generally be inert and not react with or catalyze reactions of adsorbate molecules. Commercially useful adsorbents can be classified by the nature of their structure (amorphous or crystalline), by the sizes of their pores, by the nature of their surfaces (polar, nonpolar, or intermediate), or by their chemical composition, of which the size of the pores is the most important initial consideration. Adsorption processes are temperature‐swing adsorption (TSA) and pressure‐swing (PSA) as well as purge‐swing cycles and nonregenerative approaches. Most adsorption processes use fixed beds, but some use moving‐ or fluidized‐beds or wheels.

The Enhancement of CO2 and CH4 Capture on Activated Carbon with Different Degrees of Burn-Off and Surface Chemistry

“…The gas adsorption process is extensively utilized in a variety of gas separation [ 1 , 2 ] and purification applications [ 3 ], as well as methane storage [ 4 ] and environmental protection. Global warming caused by greenhouse gases is one of the greatest scientific interests.…”