Use of Fourier Transformation Infrared (FTIR) Spectroscopy for Analysis of Functional Groups in Peanut Oil Biodiesel and Its Blends

Aims: The paper studied how fourier transformation infra-red (FTIR) spectroscopy can be used to monitor homogenous alkali catalyzed alcoholysis of peanut oil and methanol to produce biodiesel. The spectrum generated was used to identify the functional groups in the fuel sample for qualitative analysis and associated type of vibrations. Analyses on biodiesel blends with fossil diesel were also carried out with FTIR spectroscopy.

Place and Duration of Study: Department of Mechanical Engineering, Federal University of Technology, Akure, Ondo State, Nigeria, between December 2014 and March 2015.

Methodology: Biodiesel was produced by transesterifying peanut oil with methanol in the presence of sodium hydroxide as catalyst. Molar ratio of 6:1 (methanol to oil) was followed to shift the reaction to product side for more yield of fatty acid methyl esters (FAME) and the use of catalyst enabled the reaction to proceed faster. The oil and biodiesel were characterized following ASTM standards. The biodiesel obtained was separated from glycerol, washed with distilled water and dried. Biodiesel blends with fossil diesel from 10% v/v to 90% v/v in a step of 10% were produced. Samples of biodiesel and biodiesel blends were scan within mid-infrared region of 4000 cm-1 – 400 cm-1 with fourier transform infrared spectrometer by agilent technologies. The spectra obtained were interpreted and analyzed with the aid of structure correlation chart. A visual basic computer program was developed based on the data analyzed and experience gained.

Results: The results revealed that the biodiesel contained fatty acid methyl esters (FAME). The FTIR spectrum for the biodiesel revealed the functional groups with characteristics bands, C=O, -(CH2)n-, C-O, C=C and C-H in the spectrum. The absorbance intensity (peak), at a region where strong absorption of FAME occurred in each blend spectrum increases with biodiesel concentration when verified with Beer’s law and the R2 value of 0.992 was obtained to show good fitting. Changes of transmittance with concentration and absorbance of blend spectra explored showed that transmittance decreases with both concentrations and absorbance and the R2 values of 0.991 and 0.997 were obtained respectively.

Conclusion: Catalyzed complete transesterification was performed on the peanut oil and methanol. The biodiesel produced contained an ester functional group and showed that it can be used as a substitute for fossil diesel in diesel engines. The biodiesel is miscible with fossil diesel and blending of any biodiesel concentration can be obtained. The computer program developed can help to identify the functional groups of similar fuels and associated type of vibrations at a given wavenumber within mid-infrared region.