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

摘要

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.