CO2 PARTICIPATION IN CROSS-LINKING REACTIONS AND CHAR FORMATION DURING BIO-OIL PYROLYSIS.

摘要

The integration of new CO2 capture and storage technologies into energy generation processes has led to the development and study of the oxy-fuel combustion, in which the nitrogen in the air is replaced by recirculated CO2 that facilitates its capture and storage to reduce polluting emissions. Currently, the integration of oxy-fuel technologies with the use of new fuels such as bio-oil obtained from the pyrolysis of biomass is a topic of interest. In this case, the CO2 content surrounding the bio-oil droplets modifies the pyrolysis mechanism due to barriers in the diffusion of light volatiles at low temperatures (less than 200°C) and formation of char as a result of the cross-linking reactions [1] explained by the hydrolysis of the heavy fraction of bio-oil is restricted in this atmosphere. The thermal decomposition of bio-oil in the atmosphere of N2 and C02 presents significant differences. At temperatures between 400°C and 700°C in a CO2 atmosphere, there is evidence of the carbonization because of the cross-linking reactions. Char samples were obtained before (400 °C) and after (700 °C) of the cross-linking reactions and their chemical characteristics were analyzed using FTIR, Reactivity Analysis and Elemental Analysis[2], which permitted to elucidate the role of CO2 in carbonization. It was found that the destruction of functional groups corresponding to the oligomers of lignin present in the bio-oil are strongly influenced when the process is carried out in N2[3], while in CO2 atmospheres the functional groups remained in char after carbonization processes. This could be explained because the diffusive phenomena of the volatile fractions and the exit water generated during the hydrolysis processes is restricted by CO2 presence. Then, CO2 carbonization will improve chemical characteristics of char obtained both in quality and quantity respect to the N2 carbonization.