WHITE OILS
Antioxidants for white oils; food grade and industrial applications
Dr. Mustafa Akin, Head of R&D and Imren Meydan, Strategic Planning Platform Leader, Petroyag
White mineral oil, also known as paraffin oil or liquid paraffin, is a transparent, colourless, tasteless, and non-fluorescent hydrocarbon mixture composed of saturated hydrocarbons. These hydrocarbons are obtained through the purification of light fractions produced during the refining of crude oil. White mineral oils play a crucial role in various industries, including cosmetics, pharmaceuticals, food, and plastics. They are also widely used as lubricants, making up over 80% of the lubricating fluid market [1], and serve as electrical insulation [2].
White mineral oils are prone to oxidation under conditions such as exposure to heat, light, humidity, and metals like copper and iron. Oxidative degradation leads to the formation of unwanted products such as acids, aldehydes, esters, ketones, peroxides, and alcohols. These compounds increase the oil’s acidity and viscosity, contributing to sludge and deposit formation, ultimately harming the oil’s performance, lifespan, and operating costs [3-5,2]. To avoid these issues and meet quality standards, white mineral oils need to exhibit strong oxidation stability [6,3,5].
Antioxidants can effectively enhance the oxidation stability of oils by preventing oxidative degradation. They are categorised as primary or secondary, depending on their role in the oxidation process. Primary antioxidants interrupt the oxidation chain by reacting with peroxy radicals, while secondary antioxidants prevent the formation of peroxy radicals by reacting with hydroperoxide (ROOH) molecules. Primary antioxidants are most commonly used because they offer substantial protection against oxidative degradation
[4,5]. Antioxidant agents are often added to oils in concentrations up to 0.5% since higher amounts do not provide further oxidation protection [1,3,2].
This study aims to investigate the impact of commercially available antioxidants on the oxidation stability of white mineral oils. Heat, and oxygen were applied to accelerate oxidation. The total acid number, viscosity, and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of the oils were measured to evaluate oxidation and the effectiveness of antioxidants in slowing down this process. The findings provide valuable insights into the behaviour of white mineral oils in real-world conditions and reveal how antioxidants influence their thermal oxidative degradation, helping extend the oils’ lifespan.
Material and methods White mineral oils are categorised into pharmaceutical (pharma) and technical quality based on their chemical properties (Table 1).
Table 1: Properties of the white mineral oils used in the study. *C&B: clear and bright
Continued on page 14 LUBE MAGAZINE NO.184 DECEMBER 2024 13
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