Inhibition effect of biodiesel on the formation of oxidized insoluble matter in diesel: characteristics and mechanism

Abstract

ABSTRACT To address the problem that oxidized insoluble matter in diesel is easily generated in the process of using, we proposed the idea of blending biodiesel into diesel to inhibit the formation of oxidized insoluble matter. We also studied the effect of the biodiesel blending ratio on the generation of oxidized insoluble matter and revealed the mechanism of biodiesel inhibiting the formation of diesel oxidized insoluble matter. According to the results, the color of the blended fuel became darker with the increase in oxidation time for B0–B100 blended fuel. The generation of oxidized insoluble matter during the oxidation of B0–B30 was obvious since the amount increased with the enhancement of biodiesel ratio. The formation phenomenon of oxidizing insoluble matter in diesel disappeared, however,when the addition ratio of biodiesel increased from 0%–30% to 40%–100%. Based on the results from Fourier transform infrared spectroscopy and gas chromatography-mass spectroscopy, the main component of oxidizing insoluble matter was tetralone. At low blending ratios, small molecule compounds such as alcohols, aldehydes, and ketones, were rapidly generated with the oxidation process of biodiesel, which maybe acted as precursors for formation of oxidation insoluble matter, thereby increasing the amount of oxidized insoluble matter. For high blending ratios, oxidized insoluble matter was gradually dissolved in biodiesel, because the polarity between biodiesel and oxidized insoluble matter was similar. The dielectric constant of biodiesel was 3.35, which indicated that biodiesel was a weak polar liquid. Meanwhile the oxidized insoluble matter was a polar substance, and its dielectric constant was 6.28–13.59. The results showed that the blending of biodiesel was expected to slow down the appearance of oxidized insoluble matter in diesel, thereby optimizing the performance of diesel and reducing the carbon emissions of diesel.