HEAT OF ADSORPTION OF CARBON-DIOXIDE AND ETHENE ON ZEOLITES A EXCHANGED WITH LI+, NI(2+) AND CU(2+)

Various contents of Li+, Ni2+ or Cu2+ were introduced in zeolitc NaA by conventional cation exchange. Crystal damages are observed on samples having suffered the lower pH. The heat of adsorption of CO2 and C2H4 was determined by isothermal calorimetry. Very high initial heats (100-120 kJ mol-1) are found in NaA as well as in Li+ exchanged samples. perhaps due to chemisorption on alkaline cations; they vanish when Ni2+ or Cu2+ replaces more than 20% of Na+, in like manner with Co2+ or Zn2+. For the adsorption of C2H4, high initial heats are absent in the case of NaA, but gradually appear when divalent cations are introduced. Apart from these strong initial values, the heats of adsorption present a plateau vs. the adsorbed amount. Abnormal low values at the plateau are indicative of crystal damages.