Evaluation of ethylic and methylic esterification reactions to reduce acidity of crude bio‐oil

Abstract

Bio‐oil produced from triglycerides thermal cracking is a complex mixture of hydrocarbons and oxygenated compounds and is a potentially renewable source for fuel and chemical production. The presence of carboxylic acids results in a high acid index making it difficult to refine and use it as a fossil fuel substitute. This high acidity causes corrosion and may interfere on the final applications. In this work, soybean oil was thermally cracked, and the bio‐oil was characterized and submitted to esterification reactions in order to evaluate the effect of temperature and reactants mass ratio. Before esterification, crude bio‐oil showed 8.61% of carboxylic acids in GC–MS characterization and an acid index of 133.33 mg KOH/g. The reactions were conducted for 90 min, from 50 to 65°C for methanol and from 60 to 75°C for ethanol, and the bio‐oil‐alcohol mass ratio from 10:1 to 1:1. Methylic and ethylic esterification at 1:1 mass ratio of bio oil to alcohol at 65°C and 75°C showed decrease of 97.5 and 90.4% in the acid index, reaching values of 3.35 and 12.65 mg KOH/g, respectively. These results demonstrate the potential of using esterification in bio‐oil to reduce its acidity and improve its quality.

Acidity Reduction of Bio-Oil by Methylic Esterification Reactions

“…The crude bio--oil produced by Ramos et al [46] showed an average acidity index of 129 mg KOH g --1 . This bio--oil was subjected to methyl esterification reaction catalyzed by sulfuric acid.…”

“…The bio--oil used in this work was produced by Ramos et al [46] from the thermal cracking of commercial soybean oil at 525 ºC, with a feed rate of 353.4 g/h and a residence time of approximately 4.44 s. This process took place in a bench scale auger reactor built in stainless steel with 920 mm in length and 25 mm in internal diameter, under isothermal conditions, steady state and continuous operation regime, as describe by details of the reactor can be found in Botton et al [8] .…”

Acidity Reduction of Bio-Oil by Methylic Esterification Reactions

“…Li et al [44] and Yu et al [47] . In the work of Ramos et al [46] and in this work, the methanol evaporation was not performed after the esterification reactions. Therefore, it must be considered that the acidity of bio--oil it will slightly increase after alcohol removal.…”

Potential of poultry residual fat biofuels from thermo-catalytic cracking

“…Índice de Iodo (g I2/g) Índice de Acidez (mg KOH/mg) (Chiarello et al, 2020;Ramos et al, 2020;Wienhage et al, 2021).…”