Érica Signori Romagnoli

Apparent activation energy and relative protection factor of natural antioxidants in mixture with biodiesel

ABSTRACT In Brazil, biodiesel mainly consists of unsaturated fatty acid esters, which gives low oxidative stability. Therefore, natural antioxidants present themselves as an alternative to prevent oxidative deterioration due to the presence of phenolic compounds in their structure, capable of inhibiting free radicals by donating hydrogen atoms. Extracts of pepper, bacupari leaves, coffee leaves and sage were added to biodiesel B100 to verify the efficiency of antioxidant on the oxidation reaction of biodiesel, using as a parameter the comparative relative protection factor (RPF). Linearity deviations were observed in the graph of the logarithm of the rate constant as a function of the inverse of temperature, indicating that the activation energy varies at the different temperatures 110, 115, 120 and 125°C of the accelerated Rancimat test. The RPF analyzed by the simplex-centroid design proved to be a suitable parameter to verify the efficiency of natural antioxidants in the protection of the oxidation reaction, indicating an optimized mixture of 25% pepper, 60% coffee leaves and 15% sage.

Mathematical modeling of multicomponent NaCl and KCl diffusion process during the salting of pre-cooked champignon mushrooms

Wet salting is an old preservation method however the NaCl has been frequently associated to high blood pressure issues. The KCl has been used as partial replacement without affecting the acceptability of the final product. In this study, the simultaneous diffusion of NaCl and KCl in champignon mushrooms in static brine and brine under agitation was modeled based on the generalization of Ficks second diffusion law and simulated using the finite element method. Main and crossed diffusion coefficients, as well as the Biot number, were determined using the super modified simplex optimization method by means of percentage error minimization. Deviations between the simulated and experimental data were 5.78% for NaCl and 4.78% for KCl in static brine and 4.95% for NaCl and 4.35% for KCl in brine with agitation and, the main diffusion coefficients 2.692 × 10-10 m2s-1 for sodium and 2.953 × 10-10 m2s-1 for potassium were obtained.

Influence of Copper and Metallic Alloys on the Oxidation Reaction of Commercial Biodiesel in Mixture with Natural Antioxidant

The purpose of this research was to evaluate the influence of metallic alloys and copper in the degradation of biodiesel in mixture with blackberry extract. Biodiesel is formed by unsaturated esters highly susceptible to the oxidation reaction. The initial induction period (IP) of the control sample was 9.53 h and, after 208 days, the IP reduced to 5.74 h. However, with the addition of the antioxidant, the final IP was 6.27 h. The assays involving carbon steel, stainless steel, silver steel and copper showed final IP of 3.78, 4.43, 1.59 and 0.09 h, respectively. This behavior indicates that the reaction was catalyzed in the presence of metal. The addition of the blackberries extract favored the increase of the induction period and the decrease of the reaction rate constant values, aside from the carbon steel that presented a final IP of 1.22 h. The highest rate constant was 7.41 h obtained for biodiesel in contact with copper, as well as the highest IP. The acid number ranged from 0.34 to 0.60 mgKOH g. It was possible to observe in the oxidation reactions the presence of the linearity deviation proposed by Arrhenius.

Influence of the extracts of senna leaves, blackberries and hibiscus flowers in the oxidation reaction of commercial biodiesel

ABSTRACT Biodiesel is being increasingly used as an alternative energy source to reduce the dependence on derived petroleum fuels. However, sources of raw material for its production may contain substances susceptible to oxidation that are incorporated into biodiesel. As an alternative to minimize and even inhibit the oxidation reaction, antioxidant extracts from senna leaves, blackberries and hibiscus flowers were added to biodiesel, which present in their composition (structures) phenolic compounds capable of inhibiting the formation of free radicals in the reaction medium. The efficiency of the extracts was evaluated by the induction period determined using the Rancimat® method at temperatures of 110, 115, 120 and 125°C. The best results were obtained in the tests with large proportions of hibiscus flower extract. The mixture design provides predictive equations for all temperatures. Furthermore, in all the assays the values of the induction period were higher than in the control sample, thus demonstrating that the extracts of leaves of senna, blackberries and hibiscus flowers were efficient in protecting the biodiesel against the oxidation reaction. The multiresponse optimization proposed an optimal mixture containing 80% hibiscus flower and 20% senna leaves extract.

Application Self-organizing Map Type in a Study of the Profile of Gasoline C Commercialized in the Eastern and Northern Parana Regions

Artificial neural networks self-organizing map type (SOM) was used to classify samples of automotive gasoline C marketed in the eastern and northern regions of the state of Parana, Brazil. The input order of parameters in the network were the values of temperature of the first drop, the 10, 50 and 90% distilled bulk, the final boiling point, density, residue content and alcohol content. A network with a topology of 25x25 and 5000 training epochs was used. The weight maps of input parameters for the trained network identified that the most important parameters for classifying samples were the temperature of the first drop and the temperature of the 10% and 50% of the distilled fuel. DOI: http://dx.doi.org/10.17807/orbital.v7i2.732