Monitoring of the ester production by near-near infrared thermal lens spectroscopy

• Published in: Fuel (Guildford) 2019-10, Vol.253, p.1090-1096
• Main Authors: Deus, W.B., Ventura, M., Silva, J.R., Andrade, L.H.C., Catunda, T., Lima, S.M.
• Format: Article
• Language: English
• Subjects: Absorption; Absorptivity; Alcohols; Biodiesel; Biodiesel fuels; Biofuels; Chemical reactions; Correlation analysis; Diesel; Infrared spectroscopy; Near infrared radiation; Near-near infrared absorption; Optical properties; Optimization; Organic chemistry; Reaction time; Refractivity; Spectroscopy; Spectrum analysis; Thermal diffusivity; Thermal Lens Spectroscopy; Thermal lensing; Time dependence; Transesterification; Transesterification reaction; Viscosity
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2019.05.097

[Display omitted] •Thermal lens spectroscopy to monitor transesterification reaction during biodiesel production.•Overtones of O-H and C-H vibrations for monitoring biodiesel production.•Thermo-optical properties for information on the biodiesel production time and quality. Near-near infrared (N-NIR) Thermal Lens Spectroscopy (TLS) was used to monitor the transesterification reaction during biodiesel production. Fifteen aliquots were extracted from the reaction during 20 min and their thermo-optical properties were measured as a function of the reaction time. A spectroscopic investigation was performed between 855 and 990 nm to identify overtone absorptions bands (markers) to monitor the chemical reaction. The results show that the OH absorption overtone (∼970 nm) from alcohol, which is used in the reaction, is the most appropriated marker to monitor the biodiesel production. The time dependence of the thermo-optical parameter A(dn/dQ), which is the product between the absorption coefficient (A) and the refractive index dependence with the sample deposited heat (dn/dQ), exhibits a very good correlation with the ester production measured by chromatography. Besides, the measured thermal diffusivity values as function of reaction time indicates a strong dependence with the viscosity of the aliquots. It is possible to conclude that the used TLS in the N-NIR region contributes to the optimization of biodiesel production process by indicating the best time to stop the reaction.