Evaluation of Effects of Selected Wax Inhibitors on Wax Appearance and Disappearance Temperatures

In this investigation, a light transmittance method was used to evaluate the wax appearance temperatures (WAT) and wax disappearance temperatures (WDT) of model paraffin compounds (n-C₂₄H₅₀ (C₂₄) and n-C₃₆H₇₄ (C₃₆)) in n-decane (C₁₀) solutions both with and without wax inhibitors. The change in WAT at different paraffin concentrations in the presence of an inhibitor behaves as though there is a constant amount of paraffin removed by the inhibitor. However, the amount of apparent paraffin reduction by an inhibitor (e.g. 160 g of C₂₄ by one gram of an inhibitor) indicates that the inhibition mechanism cannot easily be explained by a simple “sequestering” effect. Wax inhibitors that decrease the WAT tend to also increase the WDT. Most of the wax inhibitors tested at a dosage of 100 ppm did suppress the WAT of lower molecular weight paraffin (C₂₄) solutions, but had little or no effect for higher molecular weight paraffin (C₃₆) solutions. Side-chain length of polymethacrylate wax inhibitors is an important performance parameter. Of the three polymethacrylate wax inhibitors tested, the one with the longest alkyl side-chain (C₁₈) had the most effect on suppressing the WAT and increasing the WDT of the binary mixtures (n-C₁₀-n-C₂₄ solutions).