Chemical Engineering January 2018 - 23

WINNING ACHIEVEMENT
CB&I and Albemarle:
AlkyClean® alkylation technology
AlkyClean gasoline alkylation technology is an
advanced solid-catalyst alkylation process for
the production of motor fuel alkylate. With AlkyClean
technology, light olefins from typical
petroleum-refinery sources, such as fluid catalytic
cracking (FCC) units react with isoparaffins
to produce alkylate. Of primary interest
is the reaction of butylenes with isobutane to
form high-octane trimethylpentane isomers.
General description. The novelty and success
of the AlkyClean technology is the ability
of petroleum refiners to completely eliminate
the use of liquid acids (H2SO4 or HF) and their
associated hazards and operational complexity.
Solid catalyst is used in multiple fixedbed
reactors, operating in cyclical mode, to
continuously produce high-quality alkylate,
while those off-line are being regenerated.
The chemical engineering challenge was
to create the ability to fully recover catalyst
activity over multiple cycles. Breakthroughs
made with the catalyst formulation and the
regeneration process make this possible.
For decades, scientists have been trying to
replace liquid acid technologies with a safer
and more environmentally friendly solid catalyst
technology. HF, in particular, is extremely
toxic and, upon release, forms clouds that
can be lethal for miles. Prior approaches with
solid catalyst failed because of poor product
selectivity or inability to fully recover catalyst
activity. In some cases, these catalysts also
used leachable corrosive components that
could migrate into the product.
CB&I and Albemarle offer a catalyst/process
combination that eliminates these drawbacks
entirely. Furthermore, neither acid-soluble
oils, nor spent acids, are produced and
there is no need for product post-treatment
of any kind. Without these waste streams
and the need for post-treatment, corrosion
is virtually eliminated in the downstream fractionation
section. With the use of particulate
catalyst, liquid acids are no longer required.
Albemarle's AlkyStar® catalyst has been
designed for exclusive use with the AlkyClean
process. It uses a zeolite that is
well proven in the industry, along with a low
concentration of a noble metal component.
The strength, type and number of the zeolite's
acid sites on the catalyst are optimized
to enhance hydrogen transfer reactions over
multiple alkylation reactions.
The process. The AlkyClean process consists
of four main sections (Figure 1): reaction,
catalyst regeneration, product distillation
and an optional feedstock pretreatment
Hydrogen-rich fuel gas
i-Butane
Make-up
i-Butane
Feed
Olefin feed
pretreatment
Reaction
section
Product
fractionation
section
n-Butane product
Alkylate product
Hydrogen
Catalyst
regeneration
CB&I
section (depending on the quality of the olefin
feed). Olefin feed, together with isobutane
recycle, enters the reaction section. The
reactor operates in liquid phase in the temperature
range of 50 to 90°C and a pressure
of 20-30 barg. These operating conditions
are quite mild and typical of other processing
units within a refinery. In the AlkyClean process,
multiple reactors are used to allow for
continuous alkylate production, as individual
reactors cycle between online alkylation and
low-temperature regeneration.
During regeneration, olefin addition is
stopped and H2 added to achieve a low
concentration of H2 in the reactor, while
maintaining
liquid-phase
alkylation
reaction
conditions. This allows for a seamless
switchover between alkylation and regeneration,
while minimizing energy consumption.
During low-temperature regeneration,
H2 cleans the catalyst, thereby delaying the
buildup of longer-chain hydrocarbons.
Over time, however, there is still a gradual
loss of catalyst activity, which is recovered by
taking the reactor off line for a high-temperature
regeneration step, which fully restores the
catalyst activity. With this innovative continuous
regeneration scheme, the performance is
maintained without any disturbances to plant
operation. The swing reactor, coupled with
long catalyst life, allows the refiner to tailor
turnarounds in line with FCC requirements.
Development and commercialization. The
AlkyClean process and catalyst were developed
at Albemarle's research center in Amsterdam
with more than 60,000 h of operation
on a small bench-scale pilot unit. In addition, a
10-bbl/d demonstration unit was operated in
Porvoo, Finland on an actual refinery butylene
stream for over two years. The data collected
were used by CB&I to finalize the design basis
for the technology and to successfully scale
up to a commercial-sized plant.
The first commercial AlkyClean unit successfully
started up in August, 2015, in Zibo,
China by Shandong Wonfull Petrochemical
Group Co. (Figure 2, and cover image).
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JANUARY 2018
FIGURE 1. The four main sections
of the AlkyClean process
are shown here
CB&I
CB&I
FIGURE 2. The two photos
show the first commercial
plant to use the AlkyClean
process. This 2,700-bbl/d unit
started up in 2015 in Zibo,
China and has now been operating
safely and successfully
for over two years, producing
an alkylate product at a
quality on par with existing
technologies, and meeting or
exceeding all process guarantees.
The RON (octane) value
of the alkylate product is typically
in the 95 to 97 range
23
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Chemical Engineering January 2018

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