Performance of Equilibrium FCC Catalysts in the Conversion of the SARA Fractions in VGO

Abstract

Two equilibrium FCC catalysts of the octane-barrel (ECAT-D) and resid (ECAT-R) types were used in the cracking of a typical vacuum gasoil (VGO) and its saturated (SF), aromatic (AF), and resin (RF) fractions. The experiments were carried out in a batch, fluidized bed laboratory CREC Riser Simulator reactor. The reaction temperature was 500 °C, the catalyst-to-oil relationship was 1, with 0.2 g of the catalyst being used in each experiment, and the reaction times were 0.7, 1.5, and 3 s. The ranking of the reactivities of the different feedstocks was SF > VGO > AF > RF over both catalysts. While the AF and RF fractions yielded more gasoline than the SF fraction, the latter showed the highest yields of LPG. The coke forming trend followed the order SF < VGO < AF < RF. Even though catalyst ECAT-D, with a higher and stronger acidity, was more active than catalyst ECAT-R, which has less acidity and better textural properties (higher mesoporosity and pore diameter), the latter was less affected by coke deposition, considering the changes in the specific surface area and acidic properties after use. Coke impacted more severely on Bronsted acid sites than on Lewis sites, particularly when the AF and RF fractions were used. The stronger acid sites were more severely affected by coke, particularly in catalyst ECAT-D. The negative effect on strong acidic sites was consistent with the increasing basic character of the feedstocks, following the order SF < VGO < AF < RF.