The product distributions in slurry phase hydrocracking of a kind of heavy oil (AR from Venezuela, VAR) with four kinds of surfactants (cetyltrimethylammonium bromide (CTAB), sodium dodecyl benzenesulfonate (SDBS), 12 alkyl two methyl betaine (TATMB), and OP-10 (OP)) were studied to select the best surfactant restraining the coke on the surface of the reactor (cokeS). In order to understand the action mechanism of surfactant, the asphaltene surface functional groups were analyzed, and the catalyst’s average diameter, system’s colloidal stability parameter (CSP), and asphaltene’s adsorption performance on the metal surface were measured also. Results indicated that CTAB could reduce cokeS from 1.6 to 0.4 wt %, while SDBS increased cokeS, and TATMB and OP almost do not affect cokeS. Only the change regulation of asphaltene’s adsorption performance and cokeS was consistent with different surfactants, which implied the asphaltene’s adsorptivity on the metal surface should be the critical factor controlling cokeS. The study showed the asphaltene of VAR was acidic, so CTAB with the weak basic amino group could react with VAR asphaltene, thereby restraining the adsorptivity of asphaltene on the surface of the reactor, which caused the decrease of cokeS. The mechanism of surfactant decreasing cokeS was proposed that the surfactant with the opposite functional group compared with the acidity or basicity of asphaltene can react with asphaltene through acid–base action to restrain the adsorptivity of asphaltene on the surface of the reactor resulting in the reduction of cokeS.

The effect of sodium dodecyl benzenesulfonate (SDBS) on the coke formation during slurry-bed hydrocracking of an atmospheric residue from Karamay (KAR) was studied, and three other kinds of surfactants, dodecyl trimethylammonium bromide (DTAB), oleic acid (OA), and coconut amine (CA), were used to compare to SDBS to deduce the reason for SDBS restraining the coke formation. The functional groups on the asphaltene surface and the effects of surfactants on the mean particle diameter of the catalyst, colloidal stability of the reaction system, and adsorptivity of asphaltene were investigated to find the reason for surfactant restraining the coke formation. The results showed that the order of reducing the total coke yield was CA > SDBS > OA ≈ none > DTAB and the order of reducing the coke on the reactor surface (cokesur) was SDBS > OA ≈ none > CA > DTAB. SDBS was the best surfactant to restrain coke formation during slurry-bed hydrocracking of KAR. The effects of surfactants on the colloidal stability of the reaction system were in accordance with the effects of surfactants on the total coke yield, and the effects of surfactants on the adsorptivity of asphaltene were in accordance with the effects of surfactants on cokesur, which meant that SDBS strengthening the colloidal stability of the system and lengthening the induction period of coking were important factors to reduce the total coke yield and restraining the adsorption of asphaltene on the reactor surface is the key factor to reduce cokesur. The analysis of X-ray photoelectron spectroscopy (XPS) data shows that KAR asphaltene is basic and SDBS has an acidic functional group and a suitable straight alkane chain length, making SDBS react with the basic KAR asphaltene particle to realize the effects on the colloidal stability of the reaction system and the adsorptivity of KAR asphaltene.