Soot dispersity is one of the main functions of the detergent.It was investigated the influence of the three kinds of calcium salt detergents on the dispersity of the biofuel soot (BS) in liquid paraffin (LP

simulant of base stock) by means of viscosity

spot experiment

sedimentation and particle size distribution simulation method. The calcium salt detergent included higher total base number synthesis calcium sulfonate T106

alkyl calcium salicylate T109 and higher total base number sulfuration calcium alkylphenol T115B. The disperse mechanisms of calcium salt detergent to BS were investigated by means of X-ray photoelectron spectroscopy and Fourier transform infrared spectrometer. The results showed that the dispersed systems with high concentration of BS presented obvious phenomenon of shear thinning

which was similar to that of non-Newtonian fluid. Adding T109 to the LP contaminated with BS

the disperse system showed the minimal dynamic viscosity

the maximum sludge dispersion threshold

the largest drop ratio of supernatant liquid height

the minimum aggregate particle size range and the average particle size in n-heptane. T109 was the excellent additive to disperse BS in LP. The mechanisms analysis showed that the O-containing polar groups (such as carboxyl or hydroxyl) on the surface of BS were liable to adsorb calcium salt detergent through hydrogen bond or acid-base function. At the same time

the lipophilicity of non-polar chain alkane group of calcium salt detergent formed steric hindrance in the oil and impeded BS particle aggregation. Consequently

the calcium salt detergent can disperse the BS particle in the oil.