Ethylene Dimerization on Pd-Ca-X Zeolite: Gas Chromatographic and Electron Spin Resonance Studies

Article abstract of DOI:10.1021/j100266a028

The conversion of ethylene over Pd-Ca-X zeolite was investigated in the temperature range 280-403 K.The observed reversed temperature dependence of the rate of this reaction is accounted for by the migration of Pd²⁺ cations to inaccessible sites in the β-cages at higher temperatures.The influence of various cocations, such as Ca²⁺, Mg²⁺, Na⁺, and K⁺, on the activity of palladium X zeolite also has been studied.It is found that the presence of divalent cocations promotes dimerization of C2H4 over Pd-X at low concentrations of Pd²⁺ (2Pd(2+) per unit cell) at relatively low temperatures.Under the same conditions palladium X zeolites with monovalent cocations are completely inactive for ethylene dimerization.Divalent palladium cations are proposed as the catalytically active metal species on the basis of combined gas chromatographic and electron spin resonance results.