Studies of the hydrogen held by solids: XXI. The interaction between ethylene and hydroxyl groups of a Y-zeolite at elevated temperatures

Abstract

The infrared spectra of the OH groups of a hydrogen-Y-zeolite have been recorded in the presence of C 2H 4 at pressures up to 1 atm and in the temperature range 25 to 150 °C. From these data, the heat of formation of hydrogen-bonded C 2H 4 was estimated to be about 9 kcal mole −1 for interaction with the 3648 cm −1 groups. Isotopic exchange between C 2D 4 and the two principal types of OH groups was studied at temperatures between 200 and 350 °; both exchanged at about the same rate. Equilibration of C 2D 4 and C 2H 4 proceeded via exchange with the surface OH groups. C 2D 4 OH exchange took place 1.2 times faster than C 2H 4 OD exchange over zeolite samples pretreated in equivalent ways. The kinetics deviated slightly from a first order dependence on the distance from equilibrium. The apparent first order rate constants reached an apparent maximum for pretreatment at 290 °C. The apparent activation energy for exchange was 16 kcal mole −1 for samples pretreated at 290 °C and 19 kcal mole −1 for those heated at 475 °C in O 2 and rehydrated at 350 °C. In both instances, the reaction was first order in C 2D 4 pressure.