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

Letícia Chendynski,Dionisio Borsato,Leonardo Marques,Marissa Kimura,Érica Romagnoli,Ana Carolina Mantovani

doi:10.21577/0103-5053.20180157

Abstract

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-1. It was possible to observe in the oxidation reactions the presence of the linearity deviation proposed by Arrhenius.

Highlights

Among the renewable energies of interest are the biofuels
The degradation of biodiesel during storage is caused by oxidation
Among the metallic alloys used, the sample of silver steel is the one that caused the fastest degradation of biodiesel

Summary

Introduction

Among the renewable energies of interest are the biofuels. These materials are fuels derived from renewable raw materials. Biodiesel obtained from vegetable oils and animal fats are less stable compared with petrodiesel.[2,3] This biofuel has lower stability to oxidation because it has higher levels of unsaturated esters, especially polyunsaturated carbon chains,[4,5,6,7] and there is the formation of different organic compounds such as organic acids, aldehydes, esters, ketones, alcohols and peroxides, increasing the acidity as the degradation progresses.[8,9] The degradation of biodiesel during storage is caused by oxidation. The oxidation process can occur in contact with air, ultraviolet radiation, thermal decomposition, by hydrolysis in contact with water

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