Hydrocarbon Processing - December 2022 - 27

Special Focus Catalysts
C. SENTER, BASF, Ludwigshafen, Germany;
M. CLOUGH-MASTRY, BASF, Iselin, New Jersey;
L. TAN, BASF, Singapore; and B. EREN, BASF, Houston, Texas
Flexibility in catalyst technology
for improved bottoms upgrading
Bottoms product from fluidized catalytic
cracking (FCC) is typically one of
the least valuable products from a refinery.
As a result, strong bottoms cracking
in the FCC process is needed by refiners.
While maximization of bottoms upgrading
might be desired, FCC feed, unit constraints,
operation decisions and catalyst
selection all determine the ability of an
FCC unit (FCCU) to upgrade bottoms
into more valuable products. Due to the
wide variability in these factors, there is
not a one-size-fits-all catalyst
solution
to improve bottoms upgrading in every
FCCU. This work details three separate
case studies of back-to-back catalyst trials
in FCCUs around the world. In each case,
the specific characteristics of the FCCU
were considered to select a catalyst technology
that improved bottoms upgrading.
The first study describes how a catalyst
technology and zeolite-to-matrix
surface area (Z/M) were optimized to
improve bottoms destruction in a North
American FCCU. In this case, the lowest
Z/M option was not optimal, and a more
moderate Z/M provided the best upgrading
route for the FCCU. In contrast,
the second case study details how a low
Z/M catalyst provided the best bottoms
upgrading in a European FCCU. The
third case study occurred at a heavy resid
unit in Asia. The bottoms upgrading optimization
was realized using a high Z/M
catalyst that improved coke selectivity.
From these three cases, it can clearly be
seen that the optimum FCC catalyst for
upgrading bottoms will vary depending
on the FCCU's specific requirements,
operations and constraints.
Case Study 1. The first example is from
a North American FCCU. This example
shows that changing catalyst technology
and tuning Z/M to an optimum level
can result in improved bottoms upgrading
in an FCCU. This FCCU processed
vacuum gasoil with mild-to-moderate
metals levels and used BASF Catalyst
A, a high Z/M [equilibrium catalyst
(Ecat) Z/M = 2] proprietary catalysta
to achieve high conversion. The objectives
of the FCCU shifted to incentivize
further bottoms destruction. As a
result, two new catalysts were trialed
in the FCCU to meet the objective of
improving bottoms upgrading without
sacrificing conversion. One catalyst was
not from the authors' company and contained
a much lower Z/M level (Ecat
Z/M = 0.8) vs. Catalyst A. The new catalyst
aimed to use higher matrix content
to achieve bottoms destruction. The
authors' company proposed a different
FCC catalystb
(Catalyst B) with a more
uses the
moderate Z/M (Ecat Z/M = 1.4). The
new BASF FCC Catalyst Bb
authors' company's improved zeolite-Y
technology and was chosen due to its
superior mesoporosity, which allows for
better bottoms upgrading without sacrificing
conversion to liquid products.
Incumbent
Catalyst Aa
Ecat Z/M
Ecat, nickel (Ni) + vanadium (V)
Conversion
Dry gas
Gasoline + LPG
LCO
BOT
2
3,617
73.5
2.8
66.7
16.8
9.7
TABLE 1 provides a summary of key
yields at constant conversion during
the trials. There are several notable outcomes.
First, BASF Catalyst B resulted
in lower bottoms and higher light cycle
oil (LCO) yields than either of the other
two catalysts, despite experiencing
elevated contaminant metals levels during
the trial. The LPG + gasoline yields
also increased vs. the other catalysts.
Similarly, the dry gas yield was lower
than the other catalysts despite having
> 500 ppm more contaminant metals
on the Ecat-an indication of more selective
cracking.
However, examining the yield shifts
at constant conversion only told part of
the story, as a key goal of the new BASF
Catalyst B was to improve bottoms upgrading
without sacrificing conversion.
FIG. 1 shows the bottoms vs. conversion
and LCO vs. conversion results from
the trial of the three different catalysts.
The low Z/M, non-BASF catalyst had
lower activity than the incumbent BASF
Catalyst A, and this can be seen in the
consistently lower conversion
levels.
Any potential benefit of improved or
increased matrix amount could not be
TABLE 1. Summary of yields from each trial period
Non-BASF
catalyst
0.8
3,645
73.5
3
66.1
16.7
9.8
New
Catalyst Bb
1.4
4,185
73.5
2.9
66.3
17.2
9.3
Hydrocarbon Processing | DECEMBER 2022 27
Hydrocarbon Processing - December 2022

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