The worldwide interest on renewable energies, arising mainly from the environmental constraint, is greatly increased in the last decade. Among different proposed alternatives, attention was addressed toward the employment of third generation biofuels derived from lignocellulosic and algal materials. The use of lignocellulosic biomasses are widely studied due to the low cost and high yield in products such as gas and bio-oil, but if compared to the terrestrial biomass, algal biomasses are considered a cheaper feedstock for production of chemicals and bio-fuels (bio-oil and bio-char). Pyrolysis is considered to be more economical for conversion of algal biomass into bio-fuels than thermal-acid or organic solvent extraction and transesterification methods, since it shows higher efficiency than other processes. Moreover, bio-oils can be upgraded by in-situ catalytic cracking to reduce its high acidity and oxygen content and increase the low heating value. Ni based catalyst have been often utilized in pyrolysis processes mainly due to its low cost rather than noble metals. Also the zeolites as HZSM-5 were found as one of effective catalysts for bio-oil upgrading process. These catalysts were effective to convert highly oxygenated compounds to hydrocarbons, thus Ni doping improves its hydrothermal stability and increases the yield of hydrocarbons. Furthermore, it was found that redox properties of ceria in Ni catalysts could promote both biomass/biofuel (i.e. biogas) conversion and deoxygenation reactions such as dehydration, decarboxylation and decarbonylation. Although, many papers are present in literature on catalytic biomass pyrolysis for bio-oil production, researches on effect of catalysts on pyrolysis process apply to sea plants are really scarce. Hence, main objective of this work was to investigate about the feasibility to produce high quality bio-oil from Mediterranean sea plant by pyrolysis process. Therefore, experiments using Posidonia Oceanica at 500 °C were explored with respect to biomass conversion and bio-products (bio-char, bio-oil and syngas) yields. Moreover bio-oil was studied in terms of oxygen and organic compounds content. Effect of different “home-made” Ni, Ce, HZSM-5 based catalysts on pyrolysis process was analyzed mainly in terms of bio-oil yield and bio-oil oxygen content. The highest bio oil yield (51.15 wt. %) and effect on deoxygenation (6.87 wt.%) was obtained at 500°C with CeO2 catalyst but the best composition was showed in presence of Ni/HZSM-5 catalyst. Lower content of acids and oxygen in the bio-oil, higher hydrocarbons, combined with HHV show promise for production of high-quality bio-oil from Posidonia Oceanica via catalytic pyrolysis.
|Titolo:||PHYSICAL AND CHEMICAL CHARACTERIZATION OF BIO-FUELS PRODUCED BY PYROLYSIS OF POSIDONIA OCEANICA SEA PLANT|
|Data di pubblicazione:||15-feb-2017|
|Appare nelle tipologie:||Tesi di dottorato|