Transesterification of Pequi (Caryocar brasiliensis Camb.) bio-oil via heterogeneous acid catalysis: Catalyst preparation, process optimization and kinetics

Abstract

The transesterification of Pequi (Caryocar brasiliensis Camb.) bio-oil was conduct with a heterogeneous acid catalyst prepared with the fruit’s carbonized rinds. The newly-developed catalyst was characterized by TGA/DSC, XRD diffraction, and FTIR analysis. Experiments for process optimization of biodiesel production and catalyst reusability were carried out, also investigating the kinetics involved in bio-oil mass conversion. Crude FAME content was analyzed with GC-FID gas chromatographer and its fuel properties compared to worldwide standards. Main finds were a crude FAME majorly composed by methyl esters of palmitic acid, linoleic acid, and stearic acid, representing about 49.93, 13.24, and 10.16 wt.%, respectively. Optimized conditions for maximum FAME synthesis from Pequi bio-oil (99.4 ± 0.33%) were 18:1 M ratio of methanol to bio-oil, 60 °C of temperature, 100 min of reaction, catalyst load of 2.5 wt.%, and stirring speed of 600 rpm. Kinetics of the bio-oil mass conversion through transesterification presented reaction rates varying from 0.016 to 0.091 min−1, 63.07 kJ kg−1 of activation energy (Ea), and pre-exponential value (A) of 11.4E105. Catalyst efficiency decreased to 34.9% after 10 reuse cycles. Fuel properties of the crude FAME met worldwide standards of biodiesel quality, thus indicate that Pequi bio-oil is a viable, sustainable, and widely available feedstock option in Brazil.