Spanish Petroleum Co. (CEPSA) has three refineries in Spain
(Tenerife, La Rábida in Huelva and GibraltarSan
Roque) that produce transport fuels and petrochemical feedstock. The La Rábida
refinery started operations in 1967, and the refinery
configuration and port facilities allow the refinery to
produce, store and distribute a wide range of products for
industry and consumers. The fluid catalytic cracking unit
(FCCU) was designed with the goal to enable processing
flexibility for a wide variety of feeds.a
In recent years, the profitability of European refineries has been
negatively affected by a number of large-scale trends. Two
particular trends are the reduced appetite for gasoline imports
from Europe to the East Coast of the US and the movement toward
dieselization. However, adaptable refineries are able to
improve product mix to meet changing societal needs and
maintain profitable margins. In particular, refineries able to
produce high-quality petrochemicals feedstock (like propylene), make the
right amount of gasoline and increase conversion of low-value
feeds, have improved margins.
Around 80% of propylene is generated as a byproduct of
ethylene via steam cracking and gasoline by the FCCU. However,
recent shifts to using lighter feedstocks in steam crackers have
resulted in a decrease in propylene production.1
There is potential to fill this gap with FCCU propylene.
Analysis of FCCU equilibrium catalyst (ECat) data shows
increased propylene make from all regions between 2002 and
2012. This trend is expected to continue.2 At the La
Rábida refinery, making propylene is an
attractive proposition, since the refinery and petrochemical sites are closely
CEPSAs La Rábida refinery has been producing
high propylene yields for almost 25 years. Nonetheless, the
refinery wished to challenge the status quo and investigate if
even better performance was possible. The base case catalyst
was a high propylene yield catalyst.3 To see if the
new catalyst would outperform this, laboratory testing and a
commercial trial were undertaken.
The refinery defined four objectives for the new catalyst.
Increase propylene and isobutylene yields
Maintain similar light cracked naphtha at higher
Increase bottoms upgrading and conversion
Improve the capability and flexibility to process
unconverted oil (UCO) from the hydrocracker and other
nonconventional feeds in the FCC.
Prior to the commercial trial, CEPSA R&D performed a
catalyst evaluation in its laboratory, comparing catalysts from
the incumbent and new catalyst suppliers.b Fresh
catalyst samples from each supplier were steam deactivated to
simulate commercial ECat and then tested in a Davison
circulating riser pilot plant unit. Based on the results of
this evaluation, the new catalyst was selected for a commercial
In general, FCCUs typically produce around 4 wt% to 6 wt%
propylene, depending on feed type, operating conditions and the
FCC catalyst. By optimizing all these factors, propylene
production can be increased up to 12 wt%.2, 4
To generate higher propylene yield, ZSM-5 additive is
typically added on top of the base catalyst, which can result
in dilution of the base catalyst activity. As a rule of thumb,
every 5% of non-FCC cracking material in the unit inventory
reduces the FCC conversion by 1%. This is not a concern at low
ZSM-5 additive levels, but at the high levels required to truly
maximize propylene, it can become an issue. This can require
higher fresh catalyst addition rates to compensate for this
The catalyst under evaluation does not suffer activity
dilution because the ZSM-5 functionality is present in the base
catalyst formulation. The presence of the ZSM-5 zeolite also
allows for maximized liquefied petroleum gas (LPG)
olefins.5, 6 This particular catalyst allows for the
production of highly olefinic naphtha by providing enhanced
diffusion of feed molecules to pre-cracking sites located on
the external, exposed surface of highly dispersed zeolite
crystals. This results in higher bottoms conversion with high
yields of olefinic naphtha. The gasoline range olefins are then
selectively converted to LPG olefins by the ZSM-5
Technical support service
While the catalyst was being tested, technical support
services were provided to the refinery. The package included
site visits and logistical support, process and laboratory
sample analysis and FCCU optimization using a number of
The La Rábida FCCU feed is a mixture of vacuum gasoil
(VGO) and nonconventional feed components, such as UCO from the
hydrocracker, Furfural extract (FE) from lubes processing and
other low-value components. It is desirable to process all the
UCO in the FCCU because recycling this in the hydrocracker
tends to shorten catalyst cycle length.
As the proportion of UCO in FCCU feed is increased, the
proportion of FE must also be increased to improve slurry
viscosity and heat balance in the FCCU. However, FE contains
about 80% hydrocarbons with aromatic rings, and with the
previously supplied catalyst in the base case operation, it was
difficult to convert this material in the FCCU. In addition,
the refractory FE contributed to increased slurry yields.
Historically at La Rábida, the maximum amount of FE that
could be processed in the FCCU was constrained by the maximum
slurry disposal to fuel oil.
The new catalyst delivered improved bottoms cracking
performance, allowing more of the FE aromatic side chains to be
converted. As a result, it was possible to significantly
increase the proportion of FE in feed. The FE limit with the
base catalyst was around 10%, while, with the new catalyst, the
FCCU is now able to operate with up to 20% FE in feed. The
flexibility to increase the proportion of FE in the FCCU feed
enabled all the UCO production from the hydrocracker to be sent
to the FCCU for the first time. Increasing the FE and UCO in
FCCU feed has enabled the refinery to significantly reduce the
amount of VGO sent to the FCCU. VGO is a good quality FCC feed,
but it is also significantly more expensive than FE and UCO.
Further, it is preferred to send VGO to the hydrocracker where
it is more valuable to the refinery. The net results were:
Reduced FCCU feed cost
Expanded FCCU and refinery
The changes in FCCU feed composition are shown in
1. FCCU feed composition.
The new catalyst met the main trial objective by
significantly increasing both propylene and isobutylene yields
for all feed compositions (Fig. 2). At the
same time, the total LPG production (C3s and
C4s) was significantly increased, even at lower
riser outlet temperatures (ROTs), as shown in Fig.
2. Propylene (left) and isobutylene
(right) yields vs. proportion of FE in feed.
3. Total LPG production vs. reactor
Fine-tuning the catalyst formulation enabled the
light-cracked naphtha (LCN) yield to be maintained over a range
of ROTs, consistent with defined objectives (Fig.
4). Increases in propylene and isobutylene yields
(Fig. 2), and total LPG production
(Fig. 3), came from improved bottoms upgrading
(Figs. 5 and 6). Plus, the
CEPSA R&D analysis of the LCN suggests a slight increase in
remaining C6C9 olefins
(Fig. 4) achieved by the new catalyst even
though LPG olefins have increased. This indicates that there is
potential to further increase the propylene yield by optimizing
the ZSM-5 functionality of the catalyst.
4. Light-cracked naphtha (LCN) yield vs.
ROT (left) and
CEPSA R&D LCN olefins wt% for the La
Rábida feed (right).
5. Slurry yield vs. ROT (left) and
proportion of FE in feed (right).
6. Slurry yield vs. coke yield.
Bottoms upgrading (Figs. 5 and
6) and conversion (Fig. 7)
improved. This was achieved despite the significant increase in
the proportions of highly aromatic FE and UCO in the feed.
Since the catalyst under consideration has a unique pore
architecture and optimized porosity for heavy feed molecule
diffusion, the zeolite-based cracking provides the capability
for deep-bottoms conversion with good coke selectivity.
Fig. 5 shows much lower slurry yield over a
range of ROTs. The right side of Fig. 5
illustrates that, even for the new operating window (with a
significantly higher proportion of FE in feed), the slurry
yield is still lower than that achieved by the base case
7. Conversion corrected at 221°C
reactor outlet temperature.
All the objectives set by the refinery for the new catalyst
were met. This resulted in an improvement in FCCU
profitability, as summarized in Table 1.
Based on an ECat benchmark database, 20 to 30 FCCUs
worldwide are targeting maximum propylene production
(Fig. 8). As the figure shows, the catalyst
tested at La Rábida refinery is used by the three units
with the highest propylene yield vs. conversion and highest LPG
olefins yield vs. conversion.
8. Equilibrium catalyst benchmarking.
The new catalyst, combined with technical support service from
the catalyst supplier, enabled the CEPSA La Rábida
refinery to maximize propylene and isobutylene yields, expand
total LPG production, maintain LCN yield, improve bottoms
upgrading and expand the FCCU operating window. These changes
led to an increase in the FCCUs potential to improve
refinery profitability (+2.5 $/bbl of feed). Improved FCCU integration with other parts of the
refinery was also achieved.
Plus, processing all the UCO in the FCCU helps improve
catalyst cycle length at the hydrocracker. The increased
propylene yield supports CEPSAs activity in the petrochemicals area, while the
increased C4 olefins yield minimizes the need for
ethyl tertiary butyl ether unit feed imports. The improved
conversion of low-value components, otherwise destined for fuel
oil production, improves the efficiency and profitability of
the overall refinery.
By challenging the status quo, CEPSA has improved the
refinerys sustainability and economic
a Designed by Exxon Mobil
1 Overview from conference: Maximizing
propylene yields, BASF Conference, Frankfurt, Germany,
June 1920, 2013.
2 Shackleford, A., FCC Benchmarking: Exploring
Industry Trends and Creating Paths Forward, 10th FCC
3 Larraz, L., et al., Maximizing Propylene
Production in an FCC unit, 19th World Petroleum Congress,
4 Knight, J. and R. Mehlberg, Maximizing
propylene from the FCC unit, Hydrocarbon Processing, September
5 McLean, J., et al., Distributed Matrix
Structures: A Technology Platform for Advanced FCC
Catalyst Solutions, NPRA Conference, AM-03-38.
6 Degnan, T. F., J. K. Chitnis and P. H. Schipper,
History of ZSM-5 fluid catalytic cracking additive
development at Mobil, Microporous and Mesoporous
Materials, Vol. 3536, pp. 245252, 2000.
7 Karpov, N. V., et al., Case history:
Optimization of FCC with multivariate statistical
modeling, Hydrocarbon Processing, September
8 McLean, J. and G. M. Smith, Maximizing
Propylene Production in the FCC Unit: Beyond Conventional ZSM-5
Additives, NPRA Conference, AM-05-61.
Manuel Llanes has been the FCC plant manager
at CEPSAs La Rábida refinery since January
2010. He has a BS degree in chemistry and an MS degree
in industrial safety. He joined CEPSA 15 years
Aramburu is a researcher responsible for the
FCC area at the CEPSA Research Center. She studied
chemical engineering at Madrid University and has been
working for CEPSA for more than 10 years.
Arjona has been the FCC plant operations
manager at CEPSAs La Rábida refinery since
November 2011. He has an MS degree in industrial
chemical engineering and a MS degree in industrial
safety. He joined CEPSA seven years ago.
Serrano has been the FCC plant process
engineer at CEPSAs La Rábida refinery
since December 2011. She has an MS degree in industrial
Miranda is BASFs technical sales manager
for CEPSAs La Rábida refinery. He has a BS degree
in engineering. Mr. Miranda has more than 20 years of
experience in unit modeling, optimization,
troubleshooting and operation.
Keeley is BASFs marketing manager for refining catalysts in Europe, the Middle East and
Africa. He earned an MS degree in chemical engineering
and applied chemistry. Mr. Keeley is a professional
engineer (CEng MIChemE). He has 14 years of industry
Komvokis is BASFs technology manager for refining catalysts in
Europe, the Middle East and Africa. He holds BS and MS
degrees in chemistry and a PhD in chemical engineering.
He was a researcher at CPERI Institute of Thessaloniki
and a research professor at the University of South
Stefano Riva is BASFs
technical service manager for refining catalysts in Europe,
the Middle East and Africa. He has over 22 years of
FCCU experience, including
stints with Engelhard, BASF, Tamoil and