We have observed that pretreating Amberlyst-70 with a C9 ketone improves, up to five times, the rate of alkene oligomerization. Physical characterization of Amberlyst-70 reveals minimal changes to the particle dimensions upon exposure to 5-nonanone. Diffuse reflectance infrared spectroscopy indicates an interaction between the ketone and the acid sites within the catalyst. While the total number of acid sites is similar before and after treatment with nonanone, microcalorimetric studies of butene adsorption and temperature programmed desorption studies of butene desorption reveal that both adsorption and desorption of butene occur more rapidly in the catalyst treated with 5-nonanone, indicating that pretreatment of the catalyst with the ketone decreases the barrier for butene transport by 5-6 kJ/mol. The peak temperature for TPD spectra of butene desorption are observed to shift from 360 K for nonanone-treated Amberlyst-70 to 376 K in the case of untreated sample. The catalytic effect of the treatment with nonanone decreases slowly with time-on-stream, but remains after 200 h on stream (with the rate still being a factor of 2 higher than for the untreated sample); however, catalytic activity can be recovered upon additional treatment with ketone.
ASJC Scopus subject areas
- General Chemistry