Study On The Interaction Mechanism Of Adjuvant In Residue Slurry-bed Hydrocracking Reaction

In order to inhibit coke formation during atmospheric residue slurry-bed hydrocraking reaction, the effect of some adjuvant on coke formation was investigated in a magnetic-stirred autoclave. The result indicated that the adjuvant could not depress the coke formation when the catalysts were absent, except increase the suspension of coke in the oil-phase. Catalysts exhibited high activity and capability for inhibiting coke formation. The amount of coke was more reduced, and the size of coke in the oil-phase was decreased when catalyst and adjuvant were both added. Each adjuvant's effect was different, the effect of SA1 and SA2 was very well.The interaction mechanism of adjuvant was elucidated in two aspects: one is the effect of it on colloid character of the reaction system and the other is the effect of it in the process of catalyst dispersion and sulfuration.It was found that colloid stability of the reaction system was enhanced when adjuvant had been added. During slurry-bed hydrocraking, the reaction system could keep stability even if at high reactive temperature with the presence of adjuvant. However, when the temperature reached 400℃, the adjuvants decomposed and they could not change the stability of residue any longer. The results of FT-IR analysis indicated that the characteristic IR absorption peaks of the adjuvant were gained in the spectrum of LHAR asphaltene, so the adjuvant would be adsorbed on the surface of asphaltene. The results of UV absorption spectrum indicated that the conjugated aromatic rings in the unit sheet which was adsorbed by SA1 were generally one or two rings, and it could be dissolved by heptane because of the adsorption of SA1.The analysis results of catalyst dispersion and sulfuration indicated that the interfacial tension of oil-water system was reduced obviously and the size of droplet dispersed in the residual was reduced with the addition of adjuvant. The adsorption of adjuvant on catalyst had been studied, and the results indicated that SA1 molecules were adsorbed to the surface of catalyst particles through hydrogen-bonding. The character of catalyst surface was changed gradually from water-wet surface to oil-wet one, so the dispersity of catalyst in residual was enhanced. Results of XRD analysis indicated that, the crystal dispersion of metallic sulfides (NiS₂ and Fe_x-1S_x) was enhanced when the adjuvant had been added, and some lattices of Fe_x-1S_x were substituted by nickel atom, so a mixed and more dispersive crystal (FeNiS₂) was formed.