The College of Engineering at the University of Baghdad witnessed the public defense of the master’s thesis by Marwah Izz Al-Deen Abbas in the Department of Chemical Engineering. His thesis, titled “Microwave-Assisted Catalytic Pyrolysis of Dedonaea Branches for Enhanced Bio-Oil Yield and Quality” was presented on Monday, 7, September, 2026, in the postgraduate studies discussion hall of the Department of Electrical Engineering, under the supervision of Assist. Prof. Dr. Atheer M. Ghalib and Prof. Dr. Hayder Abdul Kareem Al- Jendeel.
This study investigated the production of bio-oil from Dodonaea viscosa branches using microwave-assisted pyrolysis (MAP). The effects of microwave power (500–800 W), reaction time (5,10, 15, and 20 min), biomass particle size (< 0.5, 0.5-1, and 1-1.5 mm), and biomass loading (10, 15, 20, and 25 g) on the distribution of bio-oil, biochar, and gas were examined. HZSM-5 and TiO₂ were then investigated separately to determine their effects on bio-oil yield and properties at catalyst loadings of 20–50 wt.%.
Among the investigated operating parameters, microwave power had the greatest effect on product distribution. The highest non-catalytic bio-oil yield was approximately 28.6 wt.% and was obtained under the best experimental conditions of 600 W, 20 min, 0.5 mm particle size, and 20 g biomass loading. Increasing microwave power above 600 W decreased bio-oil yield and increased gas formation, which was attributed to further cracking of the pyrolysis vapors. Smaller particle sizes favored bio-oil production, while increasing reaction time from 5 to 20 min increased bio-oil yield within the investigated range.
The non-catalytic bio-oil had a pH of 3.2, viscosity of 7.74 cSt, density of 1131 kg m⁻³, and higher heating value (HHV) of 15.2 MJ kg⁻¹. The addition of catalysts affected both the yield and properties of the produced bio-oil. TiO₂ gave the highest bio-oil yield of 32.42 wt.% at 600 W and 20 min. HZSM-5 resulted in a lower bio-oil yield but produced a greater improvement in bio-oil properties. With HZSM-5, the pH increased to 4.8 and the HHV increased to 25.4 MJ kg⁻¹, while the viscosity and density decreased to 4.38 cSt and 990 kg m⁻³, respectively. For TiO₂, the bio-oil had a pH of 4.2, viscosity of 5.57 cSt, density of 1091 kg m⁻³, and HHV of 21.0 MJ kg⁻¹.
GC–MS analysis showed a reduction in acid compounds and an increase in aromatic compounds with HZSM-5, indicating enhanced deoxygenation and aromatization reactions. TiO₂ showed a more moderate effect on bio-oil composition while producing a higher liquid yield. Based on the experimental results, TiO₂ was more effective in increasing bio-oil yield, whereas HZSM-5 was more effective in improving bio-oil quality. The produced bio-oil can be considered a renewable feedstock for further upgrading and the production of value-added chemicals.
