Conversion of Glycerol to Alkyl-aromatics over Zeolites

Catalytic conversion of glycerol to gasoline-range alkyl-aromatics has been investigated on a series of zeolites (HZSM-5, HY, Mordenite, and HZSM-22) at 300-400 degrees C and atmospheric pressure or 2 MPa. Although propenal (aerolein) is the major primary glycerol dehydration product over all zeolites, the pore structure of the zeolite plays a significant role on the final product distribution. The major products over one-dimensional zeolites Mordenite and HZSM-22 are oxygenates (propenal, acetol, and heavy oxygenates) without aromatic formation. HZSM-22 is suitable for the production of acrolein with 86% yield at 100% glycerol conversion. However, it is found that glycerol can be converted to high yields of alkyl-aromatics, mainly C-8-C-10 over three-dimensional HY and HZSM-5. A longer contact time, higher temperatures, and higher pressures favor the formation of aromatics, with a maximum yield of 60% over HZSM-5. A two-bed configuration with a deoxygenation/hydrogenation catalyst (Pd/ZnO) as the first bed and HZSM-5 as the second bed can further increase the alkyl-aromatic yield. The mono-functional oxygenates produced by the first bed were oligomerized and aromatized into gasoline-range alkyl-aromatics over the second bed.