Using industrially relevant operating parameters, the transalkylation of 1,2,4-Trimethylbenzene (TMB) with toluene was studied. The effect of acidity and structure, increased reaction pressure and very low levels of Pt impregnation have been investigated over both H-form and Pt-loaded zeolites: Beta, MOR, and Y. A fixed bed reactor was used at WHSV of 5 h-1 , 400 o C and a 50:50 wt. % Toluene:TMB ratio with the order of activity after 50 h TOS of Y > Beta >> MOR at 1 bar. At elevated pressure (10 bar), all catalysts showed better performance with significant improvement in MOR as pore blockage reduced and the order of activity was Beta > MOR > Y. Incorporation of Pt (0.08wt. %) further improved the activity of all catalysts with the highest conversion after 50 h TOS over Beta (62 wt. %) where Beta and MOR yielded similar levels of xylenes (40 wt. %). All catalysts were further optimized for activity whilst maintaining the desired stability and highest xylenes yield.
Catalyst deactivation remains a main challenge in the transalkylation process. To develop a cost-effective and eco-friendly catalyst, improving the regeneration characteristics of Beta/Pt-Beta catalysts was investigated. The regeneration process was carried out using hydrogen and up to four cycles (30 hours on stream per cycle). A Pt-Beta catalyst with enhanced regeneration and activity characteristic relative to the parent materials is presented, and found to be stable, with the activity fully restored by regeneration with hydrogen at 500 o C. The activity of the parent Beta dropped gradually after each cycle suggesting that the hydrogen alone at 500 o C was insufficiently effective in removing coke precursors. The drop in activity was attributed to the disappearance of Brønsted acid sites over the spent Beta catalyst due to the growth of coke molecules trapped in cavities leading to highly polyaromatic molecules blocking those active sites. This limitation can be effectively overcome by platinum addition.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.