Lignin-Based Wax Inhibitors

This article tested a novel concept for synthesizing green wax inhibitors. Four technical lignins were reacted with stearoyl chloride to produce esterified C18 esterified lignin. The effect of the reaction on the lignin molecular weight, characteristic FTIR spectra, and thermal degradation was surveyed. In addition, wax inhibition testing was performed by rheology on model waxy oils. The grafting reactions increased the mass-average molecular weight of the lignin and in some cases also the polydispersity index. FTIR analysis confirmed the success of esterification reactions as the O-H stretching band decreased, whereas the C-H and C & boxH;O stretching bands significantly increased. The thermal degradation was further found to occur at temperatures above 170 degrees C, indicating that the lignin wax inhibitors were thermally stable enough for crude oil production. The effect on waxy gelation was varied, showing that the low molecular weight waxes benefited more than the high molecular ones. A gelation point reduction of up to 6 degrees C was found after lignin addition. After the wax type, wax concentration, lignin concentration, and lignin type were varied, it was found that C18 esterified Kraft lignin exhibited the most beneficial effect. The results from viscometry agreed with the observations from the rheometric gelation point. Cross-polarized microscopy was used to map the effect on the wax crystal morphology. A difference was found only in the case of one esterified Kraft lignin, which yielded smaller and more finely dispersed wax crystals. In conclusion, a new wax inhibitor was synthesized by reacting technical lignin with stearoyl chloride. This lignin showed wax inhibitor activity in some of the tested cases. At this point, the length of the pendant alkyl chains (C18) is likely a limiting factor. However, this study attributes the potential for a new concept to synthesize green wax inhibitors.