Hydrocarbon Processing - December 2022 - 31

Special Focus Catalysts
Y. SHA, L. HAN and P. WANG, Research Institute of
Petroleum Processing (RIPP), SINOPEC, Beijing, China
Development/industrial application of FCC catalyst
for boosting high-octane gasoline production
Globally, crude oil is trending toward being heavier; the
proportion of heavy crude oil reserve is expected to be 50% of
the entire recoverable oil reserve moving forward from 2020
(FIG. 1). The global oil refining business is facing extreme pressures
not only due to the heavier and inferior raw materials, but
also from the mounting demands for environmentally friendly
refining processes and light, clean petrochemical products. This
makes the transformation of heavy oil the key factor in the productivity
and economic benefits of refineries.
The pro-hydrogenation of raw materials for catalytic cracking
is one of the most well-known techniques to increase operating
efficiency and ameliorate the quality of both raw materials and
petrochemical products. Nevertheless, the proportion of polycyclic
naphthenes and naphthenic aromatics could be enhanced
dramatically (e.g., the amount of cyclic naphthenes could account
for more than 50%). Moreover, it is well-known that both
the increase in heavy oil and the increase of boiling range of distillated
oil cause a pronounced growth of the ratio of polycyclic
naphthenes and naphthenic aromatics in the raw materials.
For these reasons, one of the most consequential problems
in refining techniques is how to make the efficient and rational
transformation of polycyclic naphthenes-including the control
of the hydrogen transfer (HT) reaction and the promotion
of the ring-opening reaction-so that more valuable light petrochemical
products can be obtained.
Unfortunately, conventional fluid catalytic cracking (FCC)
catalysts show great potential in the HT reaction, yet their abilities
in the ring-opening reaction are still relatively low. This accounts
for low yield, low octane number of gasolines and the
elevation of coke. Therefore, it is imperative to find a strategy to
optimize the distribution of catalytic cracking production and
enhance the octane number of gasolines.
This article details a new FCC catalyst to concurrently increase
the yield of gasoline and decrease the formation of coke.
Based on the perceptions of a reaction mechanism, the study
also discusses how the designs of the new catalyst developed to
meet the aforementioned requirements. Additionally, an industrial
application case is introduced.
Strategic design of an efficient catalyst. The most prevalent
FCC catalyst is usually comprised of two major components
(zeolite and matrix), which lead to two different routes to
improve the efficiency of the FCC catalyst: one is to create new
zeolite materials, the other is to develop a new matrix.
One of the most widely used zeolite materials in FCC is Y
zeolite due to its unique pore structure, high stability and proper
acidity. However, the size of polycyclic naphthene molecules
is slightly larger than the pore window size of Y zeolite, which
impedes the diffusion of those molecules into the pores, thus
promoting the secondary reaction. The authors propose that the
rational way to augment its efficiency is to create Y zeolite with
a small crystal size. Compared to the large-sized Y zeolite, the
smaller has a much larger external specific surface area, which
increases active sites on the external surface, thus improving the
catalytic cracking conversion of heavy oil or residue. Meanwhile,
smaller Y zeolite has a better dispersion of acid centers, which
accordingly boosts the availability of acid centers. Moreover, the
reduction of the crystal size truncates the channel, decreasing the
odds of collision between different molecules, which diminishes
the yield of cokes caused by the bimolecular reaction (FIG. 2).
Notwithstanding, the hydrothermal stability of the Y zeolite
could be marred by decreasing its crystal size. Accordingly, for
the development and application of zeolite with small crystal
size, it is crucial to improve its hydrothermal stability. With rigorous
experiments and theoretical guidance, the authors' company
managed to create a new type of Y zeolite. The size of this new Y
zeolite is only ~500 nm, which is about half of the regular NaY. As
shown in FIGS. 3A-3D, the stability of the new Y zeolite (marked
FIG. 1. The increasing trend of heavy oil from 2009-2030.
Hydrocarbon Processing | DECEMBER 2022 31
Hydrocarbon Processing - December 2022

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