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Effects of Sorption Enhancement and Isobutene Formation on Etherification of Glycerol with tert-Butyl Alcohol in a Flow Reactor

Ozbay, Nalan
Doğu, Timur
In the presented work, liquid phase etherification reaction of glycerol (G) with tert-butyl alcohol (TBA) was investigated in a continuous flow reactor using Amberlyst-15 (A-15) as the catalyst. Some experiments were also repeated in a batch reactor at autogenous pressure. Effects of feed composition, reaction temperature (70-110 degrees C), and reaction pressure (1-5 bar) on the product distribution were investigated. When flow reactor pressure was reduced from S to 1 bar, enhanced glycerol conversion and isobutene formation were observed. Conversion of glycerol reached 66% at 110 degrees C, at a space time of 18 s . g . cm(-3). However, batch reactor results indicated glycerol conversion values over 90% with diether selectivity of about 36% at much longer reaction times, over 400 min. Results indicated significance of equilibrium limitations, which initiated the idea of performing sorption enhanced reaction experiments in the flow reactor using Zeolite 4A and SA as water adsorbents. Results of these sorption enhanced reactor experiments proved significant enhancement of glycerol conversion and diether yield by in situ removal of produced water during the etherification reaction. Among these two adsorbents, performance of Zeolite 4A was better. Diether selectivity increased from about 0.20 to values over 0.33 in the sorption enhanced reactor experiments performed with a zeolite/catalyst ratio of 4/1 at 90 degrees C.