Effect of Glycerol on Coke Characteristics in the Aromatization of Aqueous Glycerol Solution

The characteristics of coke formed in the aromatization of aqueous glycerol solution over H-ZSM-5 has been investigated by various characterization techniques such as TGA for coke amount, BET and TEM–EDS for coke location, NH₃-TPD and chemisorbed FT-IR for acid sites of coked samples, and TPO, XPS and UV-Raman for coke species. Coke formed in methanol aromatization was characterized for comparison. All results indicate that glycerol contributes to the formation of heavy and oxygenated coke, unlike methanol, that was grown from internal Brönsted acid sites of H-ZSM-5 and rapidly spread all over the particles. This is due to the three OH groups of glycerol that can be condensed via intramolecular and intermolecular dehydration reactions in various manners, which explains the fact that glycerol is transformed into multi-ring aromatics like naphthalenes via oxygen-containing intermediates including alcohol, aldehyde, ester and ketone molecules. This is the effect of glycerol on coke formed in glycerol aromatization.