Catalytic upgrading of Kraft lignin derived bio-oil in supercritical ethanol over different crystal size hierarchical nano-HZSM5

In this study, different crystal size hierarchical nano-HZSM5 single crystals were hydrothermally synthesized by using a mixture with the molar composition of 3TPAOH:0.5Na(2)O:0.5Al(2)O(3):25SiO(2):xH(2)O. Based upon the value of x, the synthesized nano-HZSM5 were designated as HZSM5-375, HZSM5-450 and HZSM5-750. These were characterized by XRD, TEM, EDS, NH3-TPD, and N-2 adsorption/desorption isotherms. The synthesized zeolites exhibited large total surface area and mesopore volume than commercial HZSM5-P38. These zeolites were employed for upgrading of Kraft lignin derived liquefaction bio-oil in a batch reactor at 300 degrees C in supercritical ethanol. The chemical compositions of the upgraded bio-oil samples were determined by GC-MS and CHNS elemental analysis. Among all the zeolites used in this research, HZSM5-375 was found to be the best catalyst for bio-oil upgrading due to its small crystal size and significantly large very-strong acid site content. Upon bio-oil upgrading, the HHV value of the stock bio-oil increased from 27.03 MJ/Kg to 30.85 MJ/Kg over HZSM5-375 zeolite. Lastly, the spent catalysts were rejuvenated and characterized by solid-state Al-27/Si-29 MAS-NMR and XRD techniques. The catalytic performance of rejuvenated HZSM5-375 zeolite was found to decrease due to the loss of Al atoms from the zeolite framework.