Oxidative stability performance of new azophenol derivatives as antioxidants in working fluids for high-temperature solar applications

In solar applications, the oxidation stability of heat transfer fluidsreducesthe thermal energy storage cost. In this work, the effect of new two azophenols, namely -2-sec-butyl-4-((3-chlorophenyl) diazenyl) phenol and 2-sec-butyl-4-((3-nitrophenyl) diazenyl)phenol, was studied to produce an oil that has good characteristics and is compatible with metals such asstainless steel, carbon steel, aluminum, and copper, which are generally used to manufacture pipes, heat exchangers, receivers, and storage tanks. The prepared compounds were characterized using spectroscopy analysis. The prepared compounds were added to a heat transfer fluid under operating conditions in the presence of iron and copper as catalysts. At different time intervals, the samples were tested by measuring the total acid number value. The results of this measurement show that compound II performed better than compound I. Additionally, the quantum chemical parameters were calculated. The theoretical calculations were compatible with the experimental results. •Two new azophenols prepared.•These compounds were characterized using spectroscopy analysis.•The prepared compounds were added to a heat transfer fluid under operating conditions.•The performance of antioxidant around 200% compare with base oil.•The quantum chemical parameters were calculated. The theoretical calculations were compatible with the experimental results.