Abstract
Biodiesel properties are in general attributed to the composition and properties of the oil feedstock used, overlooking the possible impacts of the catalyst preparation details. In light of that, the impacts of different catalyst preparation techniques alongside those of different support materials on the yield, composition, and fuel properties of biodiesels produced from the same oil feedstock were investigated. More specifically, tri-metallic (Fe-Co-Ni) catalyst was synthesized through two different techniques (green synthesis and wet impregnation) using MgO or ZnO as support material. The generated catalyst pairs, i.e., Fe-Co-Ni/MgO and Fe-Co-Ni/ZnO prepared by wet impregnation and Fe-Co-Ni-MgO and Fe-Co-Ni-ZnO prepared by green synthesis (using leaf extracts) were used in the transesterification process of Jatropha curcas oil. Detailed morphological properties, composition, thermal stability, crystalline nature, and functional groups characterization of the catalysts were also carried out. Using Box-Behnken Design response surface methodology, it was found that the green-synthesized Fe-Co-Ni-MgO catalyst resulted in the highest biodiesel yield of 97.9%. More importantly, the fatty acid methyl ester (FAME) profiles of the biodiesels produced using the four catalysts as well as their respective fuel properties were different in spite of using the same oil feedstock.
Highlights
There have been several literature reports on the influences that biodiesel chemical structure such as its degree of unsaturation could have on engine performance, combustion, and emissions characteristics (Lapuerta et al, 2009; Benjumea et al, 2010; Sokoto et al, 2011; Altun, 2014; Yang et al, 2016; Hellier et al, 2017; Folayan et al, 2019)
Irrespective of the method of synthesis, the crystalline phases revealed by the X-ray powder diffraction (XRD) and the Fourier-transform infrared spectroscopy (FTIR) spectra of the catalysts were dependent on the catalyst support material (MgO or ZnO)
The findings obtained revealed that catalyst type could determine fatty acid methyl ester (FAME) profile of the biodiesel produced from the same oil feedstock
Summary
There have been several literature reports on the influences that biodiesel chemical structure such as its degree of unsaturation could have on engine performance, combustion, and emissions characteristics (Lapuerta et al, 2009; Benjumea et al, 2010; Sokoto et al, 2011; Altun, 2014; Yang et al, 2016; Hellier et al, 2017; Folayan et al, 2019). Extensive studies on various oils have considered the use of different catalysts to obtain biodiesels of specific fatty acid methyl ester (FAME) profiles and qualities (Omotoso et al, 2011; Sharmila et al, 2016; Gupta and Agarwal, 2016; Cruz-Ortiz and Ríos-González, 2017). These studies conclude that the oils used are responsible for the chemical structures and properties of the produced biodiesel. The findings could pave the way for more rational design of heterogeneous catalysts using any of the several available optimization frameworks to obtain catalysts with features of interest
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