Hydrocarbon Processing - April 2021 - 40

Clean Fuels
TABLE 4. Typical utility requirements

Recycle isobutane
Propane
Depropanizer

Oleﬁn feed +
makeup iC4

Proprietary
process
reactors

Deisobutanizer
CW
Butane product

Alkylate product

FIG. 4. Proprietary solid-acid alkylation process unit diagram.

Utility
consumption,
standard oil basis
and EO/t alkylate

Solid acid

HF acid

92.3

92.5

Sulfuric acid Ionic liquid
103.1

133.81

Liquid-acid alkylation and spent-acid recovery units generally incur high maintenance costs due to the presence of corrosive acid. In numerous refineries, the turnaround and inspection intervals of the alkylation unit are determined by the
well-documented challenges associated with acid corrosion. A
solid-acid catalyst eliminates these challenges and allows the
turnaround interval to be extended to come in line with the upstream FCCU. The maintenance and inspection activities during operation and turnaround periods are also simplified without the presence of liquid acids, thus increasing productivity.
The proprietary solid-acid catalyst outperforms liquid catalyst processes in both alkylate yield and octane, thereby boosting alkylate margins from the available olefin feedstock. Alkylate octane using the proprietary catalyst is typically at least
one point higher than any other technology. Alkylate yields are
around 5% higher than liquid acid processes.
Performance of a commercial solid-acid alkylation
unit. A commercial solid-acid alkylationb unit has been in

FIG. 5. View of a commercial solid-acid alkylationb unit.

process offers significantly higher return on investment vs. liquid catalyzed alkylation units.
The capital cost savings result from multiple sources. First
is the elimination of corrosive acid from the process. Removing the liquid acid eliminates the acid neutralization equipment, product washing vessels and storage tanks for fresh and
spent acid. Second is the change in process conditions. The
solid-acid catalyst operates optimally at around 50°C (122°F).
Sulfuric acid and ionic liquid alkylation units require refrigeration to generate reasonable alkylate octane, operating around
5°C (41°F), which requires expensive compressors and refrigeration loops. Eliminating refrigeration also leads to a considerable reduction in power costs. A summary of the utility
requirements is provided in TABLE 4.
Differences in catalyst regeneration procedures also lead to
considerable savings, which may be considered either capital
or operating costs. The solid-acid catalyst is regenerated in the
reactor with hydrogen, generating only a small purge of hydrogen and light hydrocarbons. Sulfuric acid requires a large
regeneration plant that is either operated onsite (large capital
cost) or by another party (large operating cost).
40

APRIL 2021 | HydrocarbonProcessing.com

operation in Shandong Province, China, for more than 2 yr,
meeting and exceeding predicted product quality parameters.
The unit has demonstrated consistent performance and alkylate quality through more than 300 regeneration cycles per reactor, proving the robustness of the proprietary catalyst. FIG. 5
shows a view of the plant.
Two additional proprietary solid-acid alkylation projects
are underway in North America. The first project is related to
the revamp of an HF acid alkylation unit, and the second is to
revamp a sulfuric acid alkylation unit.
NOTES
Exelus' Solid-Acid Catalyst (ExSact) technology
b
KBR's K-SAATTM technology
a

LITERATURE CITED
Chung, W., R. Zhang, X. Zhang and D. Song, " Safe and sustainable alkylation:
Performance and update on composite ionic liquid alkylation technology, "
Hydrocarbon Processing, April 2020.
EDWARD GRIFFITHS is a Technology Manager for K-SAAT™
alkylation technology at KBR. He has 13 yr of refining and
petrochemicals experience in process engineering, plant
operations and technology licensing. Mr. Griffiths earned an
MEng degree in chemical and process engineering from
Newcastle University, UK.

MITRAJIT MUKHERJEE is the President and Founder of
Exelus. His research on engineered zeolites led to the
development of the breakthrough solid-acid alkylation
catalyst ExSact, which is being licensed as the K-SAAT™
process by KBR. He recently developed a novel mixed-metal
oxide catalyst (ExOlt) to produce propylene from propane,
which is being licensed as the K-Pro process by KBR.
Prior to starting Exelus, he held positions at Catalytica and Lummus.
He earned a BS degree in chemical engineering from the India Institute of
Technology and an MS degree from Southern Illinois University.

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