Skeketal Isomerization Of Butenes Over Mcm-22 Zeolite

The results obtained in the skeletal isomerization of linear butenes over MCM-22 zeolite were presented. Two samples with different silica/alumina ratios (SAR), i.e., 23 and 38, were synthesized, modified, and evaluated at 500°C by feeding a mixture of 1-butene diluted in nitrogen to the reactor. The sample with a SAR of 23 was also modified by ion exchange with sodium, by coke deposition from m-xylene and toluene, and by dealumination. Among the original samples in the protonic form, the highest SAR showed lower activity but a better selectivity. Ion exchanging the sample with the lowest SAR with sodium reduced both the activity and the selectivity due to the preferential deposition of sodium ions on the most selective sites for isobutene formation. The samples on which coke was pre-generated by reaction with m- xylene or toluene showed a significant increase of selectivity, when compared to the original zeolite, but limited stability. On the other hand, the dealuminated sample was very active and selective, and also exhibited a remarkably high stability as compared to other zeolites reported in the literature.357

A study on the Deactivation of Usy Zeolites with Different Rare Earth Contents

The deactivation of USY zeolites with different rare earth contents due to the coke formed from n-heptane at 450oC was studied. The results show that the presence of rare earth elements decreases the cracking and coking activities, increasing catalytic stability. However, reaction selectivity was not significantly influenced. The greater the rare earth content, the lower the coking rates and the coke contents. The TPO/DSC profiles suggested that the catalytic effect of the rare earth elements promoted coke oxidation