Hydrocarbon Processing - June 2022 - 25

Process Optimization
and with high energy savings
and reduced GHG emissions,
is often very attractive to PX
producers who are endeavoring
to minimize their costs and
reduce their environmental
footprints. However, there are
occasional concerns associated
with increased EB traffic in the
xylene loop and potentially
associated capacity reduction
for the PX adsorption process.
Experience shows that complexes
using the latest molecular sieve
technologies have more PX
recovery capacity than they can
utilize, and that PX capacity
limit is a non-issue when adding
an LPI unit. The slight increase
in EB traffic does not affect the
overall PX production capacity,
even with the oldest adsorption
processes now in operation.
* LPI effluent circulation around
the recovery unit and associated
additional savings: When an LPI
unit is added to an existing xylene
loop, part of the LPI effluent can
be routed directly to the inlet of
the PX separation unit (bypassing
the xylene column and generating
additional energy credits), so
long as feed specifications to the
separation process are met.
* EB-dealkylation VPI process
retrofit with an EB-reforming
VPI process: Since EBdealkylation
VPI processes operate
at a substantially higher weight
hourly space velocity (WHSV)
than EB-reforming VPI processes,
it is unusual to retrofit the former
process into an EB-reforming
VPI unit. While other process
parameters (such as temperature
and pressure) would generally
be compatible, loading an EBdealkylation
VPI reactor with an
EB-reforming VPI catalyst would
decrease the overall isomerization
capacity of the xylene loop under
consideration. This is because
there would not be enough room
in the EB-dealkylation VPI reactor
to fit the required EB-reforming
VPI catalyst quantity. However,
if such a retrofit is carried out in
conjunction with the addition
of an LPI process, then the
xylene loop can be shifted from
converting EB to benzene to
converting EB to xylene (and,
further, to PX) without incurring
feed processing capacity loss and
with substantial energy credits
gain. Similarly, VPI units that were
initially designed to operate an
EB-reforming process and that
were later debottlenecked via
conversion to EB dealkylation,
can be converted back to EB
reforming at no feed processing
capacity loss with the addition of
an LPI process to the xylene loop.
Xylene loop for the lowest PX production
cost and the lowest GHG
emissions. Since feedstock price is by
far the most important operating cost
parameter in aromatics complex economics,12
EB-reforming
VPI-which
converts EB to PX-offers significant
advantages to sites predominantly targeting
PX product. Adding an LPI process
further decreases feed consumption by
reducing product losses, while substantially
reducing energy consumption and
associated GHG emissions. For petrochemical
facilities maximizing PX output,
a xylene loop combining two specific
petrochemical processesa,b
is the most
efficient and environmentally friendly
solution for PX production.
NOTES
a Axens' Oparis® process
b
ExxonMobil's Liquid Phase Isomerization process
LITERATURE CITED
1
Albahar, M. Z., " Selective toluene disproportionation
over ZSM-5 zeolite, " doctorial thesis, University
of Manchester, UK, 2018, online: https://www.
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FULL_TEXT.PDF
2
Zhu, F., J. A. Johnson, D. W. Ablin and G. A. Ernst,
Efficient Petrochemical Processes: Technology, Design
and Operation, Wiley, New York City, New York,
October 2019.
3
Gonçalves, J. C. and A. E. Rodrigues, " Simulated
moving bed reactor for p-xylene production: Dualbed
column, " Chemical Engineering and Processing,
June 2016.
4
Mhatre, S., V. Warke, A. Choi, M. Molinier and A.
Saple, " A new liquid-phase isomerization process
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5
Statista, " Price of p-xylene worldwide from 2017-
2021, " online: https://www.statista.com/statistics/1259883/price-p-xylene-globally/
6
Argus,
" Viewpoint: Asian ethylene sector braces for
new supply, " January 5, 2021, online: https://www.
argusmedia.com/en/news/2174016-viewpointasian-ethylene-sector-braces-for-new-supply
7
Volkova, M., " LG Chem to start up new steam crackFANBING
YE is a Technology Manager, specializing
in aromatics and derivatives in Axens' Gasoline and
Petrochemicals business line in Rueil-Malmaison,
France. He is particularly involved in simulated
moving-bed PX separation technology. He joined
Axens in 2015 and has nearly 7 yr of experience in the
development of gasoline and aromatics technologies.
Mr. Ye earned an MS degree in general engineering
from École Centrale de Lyon (France); an MS degree
in automation from Beihang University (China);
and an MS degree in refining, gas and engineering
from the IFP School of Rueil-Malmaison (France).
ARNAUD COTTE leads the aromatics and
derivatives technology group in Axens' Gasoline
and Petrochemicals business line in RueilMalmaison,
France. He has more than 15 yr of
experience in the oil and gas industry. Mr. Cotte
earned an MS degree in process and chemical
engineering from the École Nationale Supérieure
des Industries Chimiques of Nancy (France), and
an MS degree in refining, gas and engineering from
the IFP School of Rueil-Malmaison (France).
MICHEL MOLINIER is a Consultant with Axens North
America for aromatics technologies and other
petrochemical processes. He has more than 20 yr of
experience in the petrochemical industry and 30 yr of
experience in heterogeneous catalysis. Dr. Molinier has
co-authored two book chapters and 30 peer-reviewed
articles and has 25 U.S. patents. He earned an MS
degree in physical chemistry from the Université de
Bordeaux (France) and a PhD in solid-state chemistry
from Philipps-Universität Marburg (Germany).
Hydrocarbon Processing | JUNE 2022 25
er in Yeosu, " MRC, June 7, 2021, online: https://
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8
Stratas
Advisors, " North America: Upcoming
cracker projects and capacity outlook, " April
11, 2019, online: https://stratasadvisors.com/
Insights/2019/041119-Downstream-NorthAmerica-Upcoming-Cracker-Projects-and-CapacityOutlook
9
OregonCoast.com,
" Polystyrene ban, " April 13,
2020, online: https://www.oregoncoast.org/industry/news/polystyrene-ban/
10
Waste360.com,
" Washington state bans polystyrene
foam, limits single-use plastic at restaurants, " May 18,
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11
Mo,
C., " Bisphenol A (BPA) regulations in the
European Union: An overview, " August 25, 2020,
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12
Omran,
H. R., S. M. El-Marsafy, F. H. Ashour and
E. F. Abadir, " Economic evaluation of aromatics
production, a case study for financial model application
in petrochemical projects, " Egyptian Journal of
Petroleum, 2017.
ANAÏS DORSEY is a Technologist specializing in
aromatics and derivatives in Axens' Gasoline and
Petrochemicals business line in Rueil-Malmaison,
France. She is deeply involved in liquid-liquid
extraction and selective reformate hydrogenation
applications. She joined Axens in 2014 and
has 7 yr of experience in the development of
gasoline and aromatics technologies. Ms. Dorsey
earned an MS degree in process and chemical
engineering from the École Nationale Supérieure
des Industries Chimiques (National School of
Chemical Industries) of Nancy, France.

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Hydrocarbon Processing - June 2022

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