Bio-oil production: A comparative analysis of catalytic pyrolysis with cobalt catalyst versus direct pyrolysis of Azolla and Ulva biomasses

Bio-oil is a key alternative to fossil fuels, and its commercialization requires assessing production quality and quantity. Catalysts play a crucial role in the bio-oil production process. This study evaluates the impact of cobalt-based zeolite (Co/HZSM-5) catalysts on the pyrolysis of Azolla and Ulva biomasses, focusing on bio-oil production and comparing it with direct pyrolysis. It demonstrated that catalytic pyrolysis improved the high heat value (HHV) and energy yield of the bio-oil compared with direct pyrolysis.Specifically, for Azolla, the bio-oil yield decreased from 30.64% in direct pyrolysis to 23.5% with the catalyst, while HHV increased from 28.6 MJ/kg to 33.2 MJ/kg. For Ulva, bio-oil yield fell from 34.43% to 26.1%, with HHV rising from 30.7 MJ/kg to 32.26 MJ/kg. Catalytic pyrolysis also enhanced energy recovery, achieving 48.37% for Azolla and 69.02% for Ulva. The process altered the distribution of pyrolysis products: biogas yield dropped from 37% to 27.14% for Azolla and from 30.5% to 16.57% for Ulva, while biochar yield increased from 39.5% to 42.21% for Azolla and from 43.4% to 49% for Ulva. These results suggest that catalytic pyrolysis is effective in producing higher quality bio-oil and improves overall energy efficiency.