The Catalyst Review July 2020 - 10

SPECIAL FEATURE
The advanced catalyst can handle a wide variety of refinery olefinic
(C2=-C5=) products. As illustrated in Figure 8, the K-SAAT process uses three
fixed-bed reactors. Two reactors operate under the alkylation cycle, and
the third reactor undergoes regeneration with hydrogen. This catalyst
system is designed to provide 24-hour cycle times. Contaminants and coke
are removed during regeneration, thus restoring catalyst activity for the
next cycle. The ExSact catalyst has an estimated five-year service life. The
K-SAAT operating costs are comparable to other liquid acid (HF and SA)
alkylation technologies. ROI on the K-SAAT unit is faster, as the process
provides flexible feedstock options, no byproduct formation and higher
alkylate yield and octane product. The solid-acid catalyst system enables
using carbon steel for process equipment, thus reducing capital and
maintenance costs. Replacing the strong liquid-acid catalyst eliminates
acid-neutralization equipment, product-washing vessels and storage tanks
for fresh and spent acid. Unlike SA alkylation, no refrigeration is needed;
the K-SAAT process operates above ambient temperature (110°F-170°F).
Heat of reaction is removed by air or water cooling.

Figure 8. Flow diagram of K-SAAT solid-acid process.

Source: KBR.

The ExSact catalyst is intrinsically safe and environmentally benign. This process is a possible retrofit to existing alkylation units. The
major change is replacing the present reactor with three fixed-bed reactors. The feed preparation and separation train can be reused.
Retrofitting an existing HF or SA alkylation unit is 60% of a grassroots K-SAAT unit and is a cost-effective option.
Projects. The first grassroots K-SAAT unit was commissioned for Haike Ruilin Chemical Co. Ltd., at its Shandong, China, facility in
2018. In addition, three K-SAAT licenses have been awarded. Luoyang Aiyou Chemical Co. signed a license for a grassroots unit at its
Henan, China, facility. At present, this project is on hold. CVR Refining licensed K-SAAT to retrofit the existing HF alkylation unit at its
Wynnewood, Oklahoma, refinery. Start-up is planned in 2021. A California-based refinery licensed the K-SAAT to revamp an existing
SA alkylation unit; start-up is planned for 2021.20
Ionic-Liquid Catalyst Developments
Likewise, ionic liquids (ILs) are possible replacements for strong liquid-acid alkylation catalysts. Key considerations with new alkylation
solutions are maintaining octane (RON) levels in the gasoline pool and providing flexibility to use cost-advantage feedstocks. In
some cases, the processing flexibility would be redirecting some refinery products, such as reformate (Figure 2), to higher-value
petrochemical applications.6 From R&D efforts, certain ILs are more efficient in alkylating olefins. Several IL alkylation technologies are
now commercialized:
Honeywell UOP-Chevron-ISOALKY
The ISOALKY process uses an advanced nonvolatile chloroaluminate-based IL catalyst that was developed by Chevron Corp.6,21 In
2016, Chevron entered into an exclusive agreement with Honeywell UOP to license the technology and supply the catalyst. The
advanced IL catalyst system is a possible alternative to established strong liquid-acid processes.
The IL catalysts can be characterized as an ammonium or phosphonium cation and negatively charged ions, such as AlCl4- or Al2Cl7-.
The ions were selected for activity and selectivity in the alkylation process and long-term stability. A trace amount of anhydrous
hydrochloric acid is needed to maintain alkylation reactivity for longer unit uptime. The IL catalyst is regenerated in situ by organic
chloride promoter addition.6
The alkylation reaction occurs at the interface of the IL catalyst droplets and hydrocarbon phase. The reactor is a biphasic reaction
and has a higher activity compared to conventional acid-based technologies. Favored reactions occur at lower temperatures
(30°F-120°F) and depend on desired octane (RON) levels of alkylate product.
The process can manage a wide range of olefin feedstocks and yield a 95-99 RON alkylate product using a mixed FCC-C4 feed.
Selective hydroisomerization of C4 olefins, which converts 1-butene to 2-butene, is necessary to achieve high-octane alkylate
product. This process can handle an ethylene feed. Methane and light gas (H2 and N2) must be removed. A 50-50 mix of ethane/
ethylene feed from the FCC unit can be alkylated to 2,3-dimethyl butane selectively. Figure 9 is the flow diagram of ISOALKY.6

The Catalyst Review

July 2020

The Catalyst Review July 2020

Table of Contents for the Digital Edition of The Catalyst Review July 2020