ITQ-12: A zeolite having temperature dependent adsorption selectivity and potential for propene separation

A study of the adsorption properties of the new, 8-ring, pure silica zeolite ITQ-12 at several temperatures reveals that it has unique, temperature dependent adsorption selectivity and high potential for the separation of propene from propene/propane mixtures. At 30 degreesC, propene is adsorbed more than 100 times faster than propane, forming the basis for a kinetic based separation. Unexpectedly, at 80 degreesC, little or no propane adsorption is observed whereas there is no evidence for any unusual decrease in propene adsorption, a property adding to the potential of this zeolite for propene separation. A small, temperature induced decrease in the minimum dimension of the ITQ-12's slit shaped cages is proposed as the reason for the loss of sorption capacity for the slightly larger propane molecules. ITQ-12's unique, temperature-dependent property gives rise to a sorption selectivity that is thermodynamically driven rather than the result of diffusion barriers. Preliminary PSA simulations indicate 99.5% purity propene can be achieved with productivity significantly larger than that reported for the aluminophosphate based zeolite, AlPO-14.