Hydrocarbon Processing - August 2021 - 49

Process
Optimization
A. A. EZZAT, Contributing Editor,
Pharos University, Alexandria, Egypt
Prospects of petrochemical disruptive technology
applications in Egypt Energy Hub Project
One of the most important challenges facing the Egyptian
economy is the growing demand for petrochemicals in different
sectors, particularly plastic materials and composites. The
local market consumes approximately 2.3 MMtpy of plastic
materials, which represents around 28% of market share.
The recent lean natural gas discoveries and reserves-more
-provide good feedstock for the petrochemicals
than 90 Tft3
industry. One of the challenges in the field of heterogeneous
catalysis is the conversion of methane (CH4
) to valuable petrochemical
materials, providing opportunities to improve the
local petrochemical industries in Egypt.
The development of oxidative coupling of methane (OCM)
is one of many disruptive technology applications having a significant
impact on chemical industries.
Compared with steam cracking processes, the OCM process
delivers a significant reduction in carbon emissions over
traditional ethylene production processes.
OCM technology developments of methane feedstocks are
a promising route for the production of light olefins as a petrochemical
feedstock.
Methane-OCM process principles. OCM is defined as a
process for converting methane into higher-value olefin products,
improving carbon efficiency and resulting in the production
of valuable fundamental petrochemicals. In this reaction,
CH4
into ethylene (C2
is first oxidatively converted into ethane (C2
).
H4
The fundamental chemical reaction mechanisms involve
on a metal oxide surface, and a homogeneous
both a heterogeneous catalytic reaction, which includes the activation
of CH4
gas‐phase component, which includes free‐radical chemistry.
The reactions are following Rideal-Redox type rection
mechanisms. Ethane is produced mainly by the coupling of the
surface-generated methyl group radicals in the gas phase.
The yield of C2
H4 and C2
tion of C2
H6 is limited by secondary reactions
of CH3
˙ radicals with the surface and by the further oxidaH4,
both on the catalyst surface and in the gas phase.
Generally, OCM technology is considered as a net-negative
carbon dioxide (CO2
compared with traditional steam cracking processes.
This is a significant improvement in carbon emissions reduction,
while concurrently capturing greater value from the
) producer per ton of olefins produced
H6), and then
emissions.
molecules. In fact, the heat generation for the OCM exotherm
and methane production (partly) from CO2
offset to CO2
is considered an
Historical background. OCM technology has attracted significant
attention for producing olefins from methane. In the
original process, the methane-per-pass-conversion was relatively
low due to the thermodynamic limitations of the OCM
adiabatic-reaction design.
The reaction exotherm improvements have been exploited
by injecting ethane into a second reaction chamber, where the
light alkane is thermally cracked to light olefins. Additionally,
to enhance the overall carbon efficiency of the process, a catalytic
methanation step is included to convert all generated carbon
monoxide (CO) and a portion of the CO2
pling reaction co-product back to methane.
Researchers have developed the original process to improve
per-pass conversion of methane, first by utilizing manganese
oxide catalyst on silica. However, one drawback of this approach
was its high operating temperatures, which has led to
methyl radicals forming higher-carbon number products, and
undesirable products (CO, CO2
and coke).
The discovery of more selective catalysts that operate in the
400°C-600°C (752°F-1,112°F) range has provided promising
yields and selectivity. However, long-term catalyst stability
issues, largely due to the required high-reactor inlet temperatures,
have significantly hampered them.
The introduction of advanced catalysts-based on zeolitezinc
(Zn)/chromium (Cr) metals-have been tested successfully,
providing approximately 20% carbon conversion, with
80% combined C2
selectivity in a single pass in the OCR reactor,
limiting the secondary radical reactions and achieving a
safe methane/oxygen ratio.
Modern OCM process. The modern OCM process technology,
shown in FIG. 1, is based on the integration potential of the
OCM process with the ethane dehydrogenation process to increase
olefin production.
The modified technology is characterized by the lowtemperature
catalytic reaction application, where newly developed
catalysts have been applied, based on zeolite-mixedmetal
oxide-nanowire catalysts. This modified catalyst
Hydrocarbon Processing | AUGUST 2021 49
oxidative cou
Hydrocarbon Processing - August 2021

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