Pirólise solar catalítica ex situ da microalga Chlamydomonas reinhardtii

Abstract

The continued use of fossil fuels for transportation, electricity and heating purposes has led to a growing search for alternative and renewable sources of energy such as wind, solar and energy from biomass. Studies of conversion processes such as pyrolysis that produce transportable and stockpile energy from biomass have been highlighted in academia. In catalytic pyrolysis (in situ and ex situ), catalysts have been applied to improve the chemical composition of the bio-oil produced. In the ex situ catalytic method, catalyst and biomass are found in different reactors and facilitate the reuse of catalysts, characterizing one of the advantages of this method. Thus, the main objective of this work was to study the ex situ catalytic solar pyrolysis of the microalgae Chlamydomonas reinhardtii using the hydrotalcite catalyst, with the purpose of producing coal, bio-oil and gas. The response surface methodology was used to assess the influence of the variables biomass mass, reaction time and percentage of catalyst on product yield and quality of bio-oil. An optimization study was carried out aiming to obtain maximum liquid yield, and the value reached was 47.59%. The bio-oils obtained in the catalytic pyrolysis showed long-chain hydrocarbons and a lower amount of oxygenated compounds, showing the role of the catalyst in improving the quality of liquid products. The desirability function was used to identify the conditions of the independent variables that simultaneously maximized the liquid yield and its hydrocarbon content. The experimental test performed under the optimum conditions showed that it was possible to obtain a liquid yield of 38.55% with a hydrocarbon content of 32.65%, and the experimental values showed good compliance with the predicted values. The charcoal characterization was performed and the values of superior calorific power (PCS) were consistent with those reported in the literature for coals derived from microalgae pyrolysis. In the evaluation of the reuse of the catalyst, 3 consecutive cycles of solar pyrolysis were performed, which revealed the good structural stability of the hydrotalcite. In addition, their performance has hardly changed over the course of pyrolysis cycles. Thus, this study showed that under certain conditions it is possible to obtain good yields of bio-oil and improve its quality through the process of ex situ catalytic pyrolysis of microalgae using solar energy.