Bifunctional catalysts for cracking of light cycle oil into monoaromatics using a hydrogen donor

The presence of aromatics (up to 60-80 wt.%) and Sulphur (up to 4 wt.%) in light cycle oil (LCO) makes LCO a poor diesel blend. Catalytic cracking of LCO and its model compounds was performed over monometallic (Ni) and bimetallic (NiW) catalysts supported over different zeolites. Instead of hydrogen, n-hexadecane was used as the hydrogen donor under FCC conditions, so as to reduce the overall process costs. The catalysts were synthesized by wetness impregnation method and characterized by using different techniques to understand the physico-chemical properties. The activity of the catalysts in terms of BTX yield followed the order: NiW/Beta > NiW/Y > Ni/Beta > NiW/Mordenite > Ni/Y > NiW/Mix > Ni/Mordenite > Ni/Mix (Figure 1(a)). The high LCO conversion and BTX yield over NiW/Beta catalyst is explained by the higher total acidity and the stronger interaction between the H₂W₁₂O₄₀ and Ni²⁺ ions than NiW supported on other zeolites. NiW/Beta catalyst resulted in the maximum BTX yield of 16.9% at 70.6% conversion of LCO in the presence of n-hexadecane, whereas in the absence of n-hexadecane, the corresponding BTX yield was 11.7% at 48.2% conversion of LCO (Figure 1(a)). The amount of coke formation was lower over bimetallic catalysts and in the presence of n-hexadecane (Figure 1(b)). Thus, n-hexadecane serves as an effective hydrogen donor to promote the hydrogen transfer reactions and results in a higher yield of the desired products.

Figure 1. (a) BTX yield and (b) coke yield for various catalysts and feed compositions.