Microactivity Test Unit Research Articles

Catalytic Cracking of VGOs Derived from Hydroprocessing (Part 2). Decline of FCC Conversion with Aging of Pretreatment Catalyst.

FCC feedstock pretreatment was carried out in a bench-scale hydroprocessing unit at two seventies, reflecting hydrotreating (HT) and mild hydrocracking (MHC), with Ni-Mo/Al2O3 catalyst, followed by FCC experiments conducted in a microactivity test (MAT) unit. The severity of the treatment had a significant effect on long-term stability of catalytic cracking. The FCC conversion in the MHC operation declined faster than desulfurization or denitrogenation, due to the combined effect of deactivation in the polyaromatics-hydrogenation and in the denitrogenation functions. The change of FCC conversion was well expressed by the equation containing nitrogen and polyaromatics plus resin in the FCC feedstock.The combination of HT and FCC (HT-FCC) operation demonstrated an advantage of maximizing production of gasoline over MHC-FCC operation. In contrast, MHC-FCC operation showed an advantage of maximizing yield of middle distillate during the initial period, but this advantage became less gradually.

Microactivity test (MAT) study of the ZSM-5 addition effects on FCC product yields and gasoline composition

A commercial ZSM-5 containing additive was tested at a MAT unit and the derived results concerning product distribution as well as gasoline composition shifts have been interpreted by means of changes in the rates of certain secondary reactions occurring during catalytic cracking. The most important resulte of the ZSM-5 addition are gasoline yield decrease, LPG alkenes increase and RON gain. The gasoline composition changes include a significant decrease of the C 6-C 9 alkanes yield, lighter gasoline formation through increase of the C 5 hydrocarbons yields, increased branching in the light alkenes and a small decrease in the naphthenes and aromatics yields. Most of the above effects have been interpreted by taking into account the enhanced alkenes reactivity on ZSM-5. A comparison of the present results with those from pilot plants and commercial units reveal that the shifts imposed by ZSM-5 either to the product yield distribution or to gasoline composition are in very good agreement, despite the significant differences of the absolute yields.