Hydrocarbon Processing - December 2022 - 26

Catalysts
desired conversion. Reducing fresh feed
intake and increasing UCO recycling
reduced the heat of reaction in the first
reactor. Additionally, simultaneously
changing to low-sulfur North Sea crudes
further reduced the heat generation. A
smooth transfer between the different
modes of operation requires an in-depth
understanding of the SSREC CLG design
and ART catalysts system to transfer
smoothly between the different modes
of operation and respond to the reduced
market demand.
Besides changes in the inlet temperature
of Reactor 1 posted by reduced
fresh feed and high UCO recycling, high
conversion leads to the risk of HPNA
accumulation and undesired secondary
cracking. Only catalysts with excellent
hydrogenation activity can meet this
type of challenge. One of the key features
of the proprietary catalystsa
is the
uniformly dispersed cracking and hydrogenation
metals components. The linear
relationship of middle distillate yield
vs. hydrocracking conversion in FIG. 8 is
another piece of evidence. No signs of
overcracking and HPNA accumulation
are observed in the conversion range
from 50% to > 90%.
Takeaway. CLG's SSREC design in combination
with ART's designed catalyst
system has shown to be extremely flexible
to adapt to continuously changing market
circumstances by allowing the unit to be
run in different modes of operation over
the two cycles. Pre-pandemic, Preemraff
maximized fresh feed intake, running
high conversion mode while maximizing
mid-distillate yield. During the pandemic,
Preemraff minimized fresh feed intake to
the minimum. The company ran at the
highest conversion to convert maximum
UCO into mid-distillates while running
spot market low-sulfur North Sea crudes.
Using the SSREC design combined with
the catalyst system while running the lowsulfur
North Sea crudes, Preemraff met
the IMO bunker fuel specifications to run
most profitably during the pandemic.
During the transition between the
different modes of operations, the more
mid-distillate selective catalyst system
showed no sign of HPNA accumulation
while increasing conversion level. The
key to a successful change in the mode of
operation was continuous two-way communication
and collaboration between
Preemraff's operational team and the authors'
companies' technical service. Unit
design flexibility and access to the companies'
technical services enabled Preemraff
to optimize unit performance within
design limits and ensure the unit always
runs safely within design limits.
ACKNOWLEDGEMENT
The authors would like to express their sincere
gratitude for the close cooperation and support provided
by the Preemraff team in the process of writing this
article. Special thanks to Mats Hörnfelt and Magnus
Hernelind for their time and efforts.
NOTES
a Chevron Lummus Global's ISOCRACKING®
b
Chevron Lummus Global's ISOFINISHING®
LITERATURE CITED
1
Zhan, B.-Z., L. Jiao, H. Ryu, W. Shiflett and T.
Maesen, " Shepherding hydrocracking profitability, "
Hydrocarbon Engineering, March 2020.
2
Mukherjee, U., A. J. Dahlberg, J. Mayer and A.
Kemoun, " Maximizing hydrocracker performance
using ISOFLEX technology, " NPRA Annual
Meeting, March 2005.
3
Papon, J. M., J. Parekh, H. A. Yoon and A. J. Dahlberg,
" Premcor heavy oil upgrade project, " NPRA Annual
Meeting, March 2002.
4
Zhan, B.-Z., T. Maesen, J. Parekh and D. Torchia,
" Don't be medieval, make more diesel, " Hydrocarbon
Engineering, November 2013.
BI-ZENG ZHAN is an ART/CLG
Hydrocracking R&D Manager
working in the Chevron
Technology Center office in
Richmond, California. He joined
ART/CLG in 2018. Dr. Zhan has
more than 15 yr of experience in
refining industry R&D and has held several roles
at the Chevron Research Center. He earned his
PhD in chemistry from the Hong Kong University
of Science and Technology, and has more than
40 publications in peer-reviewed journals and
has been granted more than 20 U.S. patents.
JACOB FRITZ is a Process
Engineer at Chevron with 24 yr of
experience in the oil refining, oil
production, petrochemical and
wastewater treatment industries.
His experience includes process
unit design, supporting refinery
unit operations, creating simulations, performing
feasibility and revamp studies, personnel
supervision and development, oversight of dayto-day
process engineering tasks and conducting
performance tests. Fritz has additional experience
with a number of process technologies, including
gasoil hydrocracking, slurry hydrocracking,
chemical enhanced oil recovery, naphtha, jet,
diesel, gasoil, renewables, residue hydrotreating,
HF alkylation, crude oil distillation, vacuum
distillation, delayed coking, fuel gas treating, penex
isomerization, hydrogen production, and naphtha/
jet merox. Fritz earned a BS degree in chemical
engineering from the University of California,
Irvine, and works in the Chevron Technology
Center in Richmond, California.
DICK SOMERS is an ART/CLG
Manager of Sales and Services
EMEA/Senior Technical Service
Engineer working in a hybrid role
out of the Chevron office in the
Netherlands, and is responsible
for several hydrocrackers and
FIG. 8. Summary of middle distillate selectivity vs. conversion on fresh feed of all cases.
26 DECEMBER 2022 | HydrocarbonProcessing.com
hydrotreaters in the EMEA region. He joined ART
in 2012 and he has more than 20 yr of experience in
the refining industry. Somers earned an MS degree
in chemical engineering at the Eindhoven University
of Technology in The Netherlands.

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