The interactions between heavy metals (vanadium and nickel) and kaolin had been investigated by X-ray diffraction and MAT test. In the process of phase transformation of kaolin containing 1–5% vanadium, vanadium-mullite phase emerged surprisingly at 660–700 ◦C. The unit cell size of the mullite was found to increase with increment of vanadium content. As compared with hydro-kaolin, acid-modified kaolin(AMK) and caustic-modified kaolin (CMK) reacted with vanadium to form much more mullite; CMK could even be reacted with nickel to form a rather stable NiAl10O16 compound, and this compound protected zeolite in fluid catalytic cracking catalyst effectively. The catalyst containing AMK had greaterMAT activity retention than that of the contrastive catalyst with hydro-kaolin in the identical level of heavy metal contamination.

★★★☆☆ Keywords: Kaolin; Nickel; FCC catalyst; Vanadium; Mullite; Eutectic; Unit cell size

★★★☆☆ Conghua Liu, Youquan Deng, Yuanqing Pan, Shygin Zheng, Xionghou Gao. Applied Catalysis A: General 257 (2004) 145–150.

Cracking of FCC naphtha has been investigated on the model catalysts containing ZSM-5 (Si/Al2 = 50, 500), Zn-ZSM-5 (Si/Al2 = 50) and USY. The presence of ZSM-5 and USY causes a tremendous decrease in olefins of gasoline fraction, leading to an enrichment of the aromatics in liquid product. It is evidently that aromatics are generated from lower olefins. The property of lower silica-to-alumina ratio of ZSM-5 and Zn modification enhance the aromatization process for higher cracking reactivity and dehydrogenation. The result of evaluation in confined fluid bed apparatus (CFBA) with the mixture of VGO and VTB as feed further confirms the aromatics generation in cracking reaction stimulated by ZSM-5 additive over base catalysts with different hydrogen transfer activity. Based on these results, relations between scission and aromatization in FCC catalyst containing ZSM-5 zeolite could be proposed. The suggested reaction path could better explain the reasons that effectiveness of ZSM-5 additive to lighter olefins is more profound in base catalyst of low hydrogen transfer activity and why so many researchers had not observed the aromatics generation motivated by ZSM-5 additive in catalytic cracking reaction.

★★★☆☆ Keywords: ZSM-5; Aromatics generation; Hydrogen transfer activity; Lighter olefins; FCC catalyst

★★★☆☆ C. Liu et al. / Journal of Molecular Catalysis A: Chemical 215 (2004) 195–199.

After modifications of rare earth and phosphorus, the acidity density and the strength in the pores of zeolite Y (PREUSY) are improved effectively; the surface acidity is suitably reduced and weakened owing to the interaction of rare earth cation and phosphate anion. NH3-TPD analysis showed that the acid distribution of the modified zeolite is more concentrated on the range of intermediate and strong acidity. This kind of modification can direct more hydrocarbons to enter into the pores to be converted and remarkably reduces the possibility of naphtha olefins forming through a surface cracking reaction. In addition, because naphtha olefin reduction does not completely depend on olefin saturation through secondary hydrogen transfer reaction, this kind of reaction mode can decrease the excessive cracking of mediate distillate and can improve the diesel oil yield (LCO) effectively. Some reaction pathways were proposed.

★★★☆☆ Keywords: Zeolite Y; Rare earth; Phosphorus; Catalytic cracking reaction; Surface modification; Reducing olefin formation; Diesel oil yield; Hydrogen transfer activity

★★★☆☆ C. Liu et al. / Applied Catalysis A: General 264 (2004) 225–228.