The Catalyst Review July 2020 - 9

SPECIAL FEATURE
Future in Alkylation Processes
Older alkylation technologies relied on strong liquid acids as catalysts (Table 3). For over 30 years, ongoing R&D efforts have
investigated other catalyst programs that can produce high-quality, high-octane (RON) alkylate and replace strong liquid-acid
systems. Key process variables that affect liquid-acid alkylation processes are:18
Reaction temperature. Lower temperature operations favor processing high-octane (high RON) products. Higher operating
temperatures increase acid consumption and byproduct (ASO) production.
Acid strength. High acid strength favors higher alkylate (RON) quality. However, operating at a lower spent-acid strength reduces acid
consumption, which is a major cost factor.
iC4 concentration. A higher ratio of iC4-to-olefin in the reaction section reduce ASO formation and acid consumption. The amount of
iC4 recycled increases and incurs higher operating costs. Larger-sized iC4 recovery/separation equipment is required.
New catalytic technologies, such as solid acid and ionic liquids, resolve many process safety and environmental issues attributed to
strong liquid-acid catalysts. In particular, these innovative catalysts mitigate the problems associated with HF and SA releases. Process
safety improves by eliminating the transport and storage of strong liquid acids.
Solid-Acid Alkylation Catalyst Developments
New solid-acid catalysts reduce ASO byproduct formation and disposal problems; both are associated with SA systems. Eliminating
strong liquid-acid catalysts enables using less expensive construction (carbon steel) materials for alkylation equipment. This change
lowers original capital costs and reduces maintenance expenses. More communities are petitioning against the usage of toxic
chemicals by refining and petrochemical companies.14,16 In particular, HF is one of the chemicals that is under great scrutiny by
regulatory agencies and environmental groups. Promising solid-acid alkylation developments are:
Albemarle/McDermott-AlkyClean

The AlkyClean solid-acid alkylation catalyst was developed by
Akzo Nobel Catalysts (now Albemarle), ABB Lummus Global
(now McDermott) and Fortum Oil and Gas (now Neste).
The first demonstration of the AlkyClean technology was
at Neste's Porvoo, Finland, refinery in the early 2000s.7 The
process uses multiple fixed-bed reactors and Albemarle's
AlkyStar catalyst, which is a proven and robust zeolite system
with a noble metal function.12 The catalyst uses optimized
particle sites and porosity to overcome diffusion limitations
and heavy species formation. It is tolerant of feedstock
changes and process upsets (water spikes, butadiene, sulfur
compounds and oxygenates). Multiple fixed-bed reactors
enable continuous alkylate processing (Figure 7).

Figure 7. Flow diagram of AlkyClean solid-acid process.

Source: McDermott Technology and Albemarle.

The first AlkyClean commercial unit has been operating for nearly five years and was constructed for the Shandong Wonfull
Petrochemical Group in Zibo, China. The 2.7 Mbpd unit safely started up in August 2015 and has met all performance requirements.
The AlkyClean technology is a revamp solution for existing HF units. This process enables reusing the existing fractionation
equipment. Process safety and environmental risks are substantially lower by replacing the HF catalyst with AlkyStar. AlkyClean
has received many awards, including the 2016 Presidential Green Chemistry Challenge Award presented by the U.S. Environmental
Protection Agency.12
KBR and Exelus Inc.-K-SAAT

A recent solid-acid alkylation technology is the KBR Solid Acid Alkylation Technology (K-SAAT). This process uses a proprietary zeolitebased solid-acid catalyst, ExSact, developed by Exelus Inc. KBR holds the license for ExSact as part of K-SAAT.
ExSact is an engineered, non-precious metal solid catalyst and has 500% more active sites than a typical solid catalyst.19,20 The
catalyst pore structure promotes the formation of high-octane TMPs and reduces deactivation by coke formation. ExSact has a robust
resistance to typical poisons, such as mercaptans, dienes and oxygenates, which are removed during regeneration.
The Catalyst Review

July 2020

The Catalyst Review July 2020

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