Comparison of the iso-structural H-SAPO-37 and H-faujasite as catalysts for the isobutane/2-butene alkylation Original Research Article

The alkylation of isobutane with 2-butene has been studied in a slurry reactor on the iso-structural H-SAPO-37 and dealuminated faujasite (FAU) catalysts. It was found that mainly dimerization takes place on H-SAPO-37 by producing C8 olefins. In the small fraction of C8 paraffins, the 3,4-dimethylhexane (3,4 DMH) was the most abundant compound. The dealuminated H-FAU catalyst, on the other hand, produced mainly the desired trimethylpentanes (TMPs). The number and strength of the acid sites in H-SAPO-37 and dealuminated H-FAU were investigated by NH3-TPD and IR spectroscopy, revealing a considerably higher relative concentration of strong acid sites in the dealuminated H-FAU catalyst compared to H-SAPO-37. Using the ratio of pyridine adsorbed at 400°C and 250°C as a measure of the ratio of strong to weak acid sites in the samples, ratios of 0.40 and 0.65 were obtained for the H-SAPO-37 and dealuminated H-FAU, respectively, ranking the dealuminated H-FAU as a much better catalyst than H-SAPO-37 in the isobutane/2-butene alkylation reaction.