Effect of temperature and the content of Na2CO3 as a catalyst on the characteristics of bio-oil obtained from the pyrolysis of microalgae

Catalytic pyrolysis of the microalga Chlorella vulgaris with a catalyst of Na2CO3 was investigated in terms of chemical composition and thermal behavior of bio-oil. The effects of the low catalyst amounts and pyrolysis temperatures were studied. In the presence of Na2CO3 and high temperature the content of aromatics and nitrogenated compounds increased and the content of carboxylic acids significantly decreased but the thermal behavior of bio-oil slightly changed. The alkane and alkene production were also enhanced with increased catalyst contents. Compared with non-catalytic runs in term of relative decrease/increase values, the bio-oil from pyrolysis with 20 wt.% Na2CO3 carried higher heating value (19.4%), lower oxygen content (47.1%), lower content of acids (83.2%) and higher content of nitrogenated compounds (51.2%). However, the low catalyst contents (< 20 wt.%) could not satisfy the bio-oil enhancement in term of calorific value, oxygen content and acidity but they did not give significant difference in term of aromatic hydrocarbons compared with that of 20 wt.% catalyst.