Benzene reduction in gasoline by alkylation with propylene over MCM-22 zeolite with a different Brønsted/Lewis acidity ratios
In this work, the liquid phase alkylation of benzene with propylene was carried out over MCM-22 zeolite treated thermally in a flow of air and nitrogen for activation. Such activation procedures led to changes in the Brønsted/Lewis acidity ratio of the samples, but not in textural properties. The alkylation reaction was conducted using as a feed a benzene-enriched sample of reformate heart cut containing ca. 20 wt% benzene. The experimental reaction was performed in a batch reactor at 220 °C adjusting the amount of propylene for a molar ratio of benzene to propylene in the feed of 2. Benzene conversion versus time profiles consisted of three regions wherein (i) the aromatic conversion decreased very slightly, (ii) it diminished drastically, and (iii) it continued dropping with time, but to a lesser extent than in (ii). MCM-22 sample containing a higher Brønsted acidity exhibited a larger resistance to deactivation during benzene alkylation experiments, as severe deactivation starts after 19 h of time on stream. Concerning products distribution, the presence of bulky (poly) alkylated products declined as the MCM-22 became more deactivated.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (185 K)Download as PowerPoint slideHighlights► Two MCM-22 zeolites with different Brønsted/Lewis ratio were prepared. ► The catalysts were tested in the alkylation of the benzene present in a real feed. ► The catalyst with the higher B/L ratio was much more resistant to deactivation. ► The higher stability of the catalyst depended mostly on the Brønsted/Lewis ratio. ► Location of the active sites appears to have an important role in the deactivation.
Journal: Applied Catalysis A: General - Volume 454, 15 March 2013, Pages 37–45