Banca de DEFESA: LUANA DE OLIVEIRA SANTOS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : LUANA DE OLIVEIRA SANTOS
DATA : 29/10/2019
HORA: 13:00
LOCAL: Pavilhão da Química, Sala 50
TÍTULO:

New approach for the determination of free glycerol in biodiesel based on periodate oxidation

PALAVRAS-CHAVES:

biofuel. molybdate. periodate. ANP Resolution 45/2014. titrimetry.

PÁGINAS: 61
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Analítica
ESPECIALIDADE: Titimetria
RESUMO:

The quality standards for biodiesel commercialized in Brazil are set by the National Agency of Petroleum, Natural Gas and Biofuel (ANP), through Brazilian Resolution N^o. 45 of 2014 (RANP 45/2014). RANP 45/2014 sets the maximum free glycerol content in biodiesel added to diesel oil at 0.02% w/w. The higher concentrations of free glycerol could to lead problems in fuel storage tanks, formation of deposits and clogging in the engine injection system and emission of toxic aldehydes. In this work, a new approach to determine free glycerol in biodiesel from  soybean, palm, macauba (pulp) and used frying oils was developed employing the glycerol oxidation by the periodate and, after, masking of the excess periodate by the molybdate. This provided a decrease in the analysis time probably due to excess periodate employed and the determination of iodate formed. The iodate was quantified by the addition of iodide, forming the tri-iodide anion. The iodometric determination was performed in three days with two distinct methods based on the spectrophotometric and titrimetric techniques. In the spectrophotometric method, the glycerol was extracted by partition in ethanol-water/n-heptane and the tri-iodide was determined in the presence of starch (λ = 582 nm). Two analytical curves were constructed after analysis of glycerol standards in a dual and single beam spectrophotometer. The latter had lower precision in the measurements, and its analytical curve presented low limits of detection (1.9 mg L^-1) and quantification (5.7 mg L^-1), and good coefficient of determination (R² = 0.9972). The repeatability of spectrophotometric method was satisfactory (CV < 12%), however the intermediate precision was unfavorable (CV < 39%). The analysis of glycerol standards in water by titrimetric method presented excellent accuracy, with relative errors below 3.0%. Detection and quantification limits were 1.2 mg L^-1 and 3.5 mg L^-1, respectively. Biodiesels were analyzed by titrimetric method after glycerol extraction by partition in water/n-heptane and, subsequent, determination of tri-iodide by the titration with Na₂S₂O₃ standard solution, in the presence of starch. The precision of this method was good in repeatability (CV < 14%) and intermediate precision (CV < 8%). The accuracy of the titrimetric method was evaluated by recovery tests at three fortification levels: 250, 500 and 1000 mg L^-1, reaching 91% to 105% of recovery. The similarity between the glycerol contents obtained in each method, between days were evaluated by ANOVA. The average global levels of free glycerol levels in the biodiesels obtained by both methods did not differ significantly at the 95% confidence level. The overall mean glycerol levels obtained by both methods were similar in the analysis of the biodiesels used in this study, according to the Student's t-test. However, the titrimetric method presented smaller variations between days, lower cost and greater simplicity compared to the spectrophotometric method. In addition, the assay was fast (10 min) when compared to the other analysis techniques described in the literature and of high detection capacity compared to other titrimetric methods.

MEMBROS DA BANCA:
Presidente - 2626414 - JOSE GERALDO ROCHA JUNIOR
Externo ao Programa - 387373 - OTAVIO RAYMUNDO LA
Externo ao Programa - 2630672 - FLAVIO COUTO CORDEIRO
Externo à Instituição - VIVIANE GOMES TEIXEIRA - UFRJ
Externo à Instituição - CARLOS EDUARDO RODRIGUES DE PAULA - UFRJ