Isobutane/2-butene alkylation on faujasite-type zeolites (H EMT and H FAU)

The alkylation of isobutane with 2-butene on hexagonal (protonated form = H EMT, investigated, for the first time on this reaction) and cubic faujasite (protonated form = H FAU) with Si/Al ratios of 3.5 was studied at 80°C and compared with the results obtained for a cerium exchanged Y zeolite (Ce Y). The alkylate composition consisted of 90% and about 80% C₈ paraffins for H EMT and H FAU/Ce Y, respectively. Within the C₈ fractions the three trimethylpentanes (TMP) 2,2,4-, 2,3,3- and 2,3,4-TMP were the dominating product compounds in all tests, whereas a higher content of dimethylhexanes (DMH) was observed for the H FAU and Ce Y. However, among the four trimethylpentanes 2,3,3,-TMP and 2,3,4-TMP were always the main compounds formed. Oligomerization was favoured only by the H FAU and Ce Y, with a strong increase of C₈ olefins after about one third of the observed reaction time. On the contrary, H EMT exhibited much less formation of C₈ olefins (and on a constant level) even after 300 min reaction time. The deactivated samples showed only formation of non-aromatic coke. The differences in the product pattern were attributed to the slightly larger size of the second type of supercage in EMT and to the stronger Bronsted acid sites in the hexagonal faujasite.Dedicated to Professor Dr. Martin Klessinger on the occasion of his 60th birthday.