However, traditional thermodynamically selective adsorbents exhibit limited C2H4/C2H6 selectivity due to their similar physiochemical properties, and the performance enhancement is typically at the expense of elevated adsorption heat.  The adsorption heat of C2H4 on ZnAtzPO4 (17.3 to 30.0 kJ mol-1) is substantially lower than many thermodynamically selective adsorbents because its separation capability only partially relies on thermodynamics. 
THERM