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THE ROLE AND EFFICIENCY OF COPPER-BASED CATALYSTS IN ETHYLENE
OXYCHLORINATION
Hikmatova Hilola Ilkhom kizi
Nurmamatova Rukhshona Mardi kizi
Khudoyberdiyeva Farzona Ilkhom kizi
Rayimova Zarina Alisher kizi
Students of the Chemistry department of the Kattakurgan
branch of Samarkand State University
hikmatvahilola00@gmail.com
Annotation
: This article explores the role and efficiency of copper-based catalysts in the
ethylene oxychlorination process, a crucial industrial reaction for producing vinyl chloride
monomer. The catalytic properties of copper compounds significantly influence reaction rates,
selectivity, and product yield. Recent advancements in catalyst design and mechanistic
understanding are reviewed to highlight improvements in performance and environmental
sustainability.
Keywords
: Copper-based catalysts, ethylene oxychlorination, vinyl chloride monomer, catalytic
activity, selectivity, catalyst efficiency
Introduction
Ethylene oxychlorination is a pivotal process in the production of vinyl chloride monomer
(VCM), which serves as a fundamental precursor for polyvinyl chloride (PVC) manufacturing.
The process involves the catalytic reaction of ethylene with hydrogen chloride and oxygen to
produce VCM. Copper-based catalysts, particularly copper chloride supported on various
substrates, have been extensively employed due to their excellent catalytic activity and
selectivity. Understanding the role of copper in catalyzing the oxychlorination reaction is
essential for optimizing industrial production, improving catalyst lifetime, and reducing harmful
byproducts.
Copper-based catalysts function by facilitating the adsorption and activation of reactant
molecules on their surface, enabling the controlled transformation of ethylene, HCl, and oxygen
into vinyl chloride. The redox cycling between Cu(I) and Cu(II) species on the catalyst surface is
central to the catalytic mechanism. Cu(I) species activate oxygen molecules, generating reactive
oxygen species that facilitate the oxidation of HCl and ethylene.
Advances in catalyst support materials, such as alumina, silica, and zeolites, have enhanced the
dispersion and stability of copper species, directly impacting catalytic efficiency. Recent studies
reveal that modifying catalyst preparation methods, including impregnation techniques and
calcination temperatures, can fine-tune the oxidation state distribution and improve catalyst
performance.
Kinetic studies demonstrate that copper catalysts exhibit high selectivity towards vinyl chloride,
minimizing the formation of byproducts such as CO and CO2. This selectivity is critical to
achieving high yield and reducing environmental impact. Furthermore, catalyst regeneration
techniques have been developed to prolong catalyst life and maintain activity during prolonged
industrial operation. Copper-based catalysts are the cornerstone of the ethylene oxychlorination
process due to their unique ability to mediate the oxidation and chlorination reactions
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simultaneously under moderate industrial conditions. The active catalytic species are primarily
copper chloride complexes, where copper cycles between Cu(I) and Cu(II) oxidation states. This
redox cycling is essential for the catalytic mechanism: Cu(I) facilitates the adsorption and
activation of oxygen molecules, while Cu(II) participates in the chlorination of ethylene. Copper-
based catalysts play a pivotal role in the ethylene oxychlorination process, which is essential for
producing vinyl chloride monomer (VCM), the precursor for polyvinyl chloride (PVC). The
catalytic system relies on copper chloride species dispersed on high-surface-area supports such
as γ-alumina, which provide the necessary active sites for the simultaneous oxidation and
chlorination reactions.
The fundamental mechanism involves copper cycling between Cu(I) and Cu(II) oxidation states.
Copper(I) chloride (CuCl) activates molecular oxygen by adsorbing and dissociating it, forming
reactive oxygen species. These species then react with hydrogen chloride (HCl) adsorbed on the
catalyst surface, generating chlorine radicals or chloride ions that subsequently chlorinate
adsorbed ethylene molecules. This redox cycle of copper is crucial for maintaining continuous
catalytic activity and high selectivity toward VCM.
Copper chloride species are usually prepared by impregnating the support with copper salts
followed by calcination and reduction steps. Calcination conditions affect the dispersion and
oxidation states of copper, with higher temperatures potentially causing sintering and loss of
active surface area. Maintaining an optimal copper loading is critical; excess copper can lead to
particle agglomeration and reduced catalyst efficiency, while insufficient copper decreases the
number of active sites.
Kinetic studies reveal that the rate-determining step in ethylene oxychlorination is the surface
reaction between adsorbed ethylene and activated chlorine species, controlled by copper’s redox
properties. Optimizing reaction temperature (typically between 200-280 °C), gas composition,
and flow rates enhances catalyst performance by balancing ethylene conversion and minimizing
byproduct formation such as CO, CO₂, and polychlorinated hydrocarbons.
To improve catalytic stability and resistance to deactivation, various promoters are introduced.
Alkali metals like potassium and rare earth elements such as lanthanum modify the acid-base
properties of the support and enhance oxygen mobility on the surface. These modifications
reduce coke formation, a major cause of catalyst deactivation, and prolong operational lifespan.
Recent advances include nano-engineering copper particle sizes to maximize active surface area
and prevent sintering under harsh reaction conditions.
Modern catalyst characterization techniques provide critical insights into the catalyst structure
and reaction intermediates. X-ray photoelectron spectroscopy (XPS) is used to monitor copper
oxidation states in situ, confirming the dynamic equilibrium between Cu(I) and Cu(II) during
operation. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) detects
surface-adsorbed species, elucidating reaction pathways and intermediate formation.
Additionally, computational modeling and density functional theory (DFT) calculations have
supported experimental findings by predicting the adsorption energies and activation barriers of
reactants on copper surfaces. These studies guide the rational design of improved catalysts with
enhanced activity, selectivity, and durability.
The ethylene oxychlorination reaction proceeds via the following simplified steps: ethylene
adsorbs onto the catalyst surface, hydrogen chloride dissociates into reactive chloride ions, and
oxygen molecules are activated by the copper centers. The surface reaction between activated
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oxygen, chloride ions, and adsorbed ethylene leads to the formation of vinyl chloride monomer
(VCM) and water as a byproduct.
Catalyst supports such as γ-alumina provide high surface area and thermal stability, which help
disperse the copper chloride evenly, preventing agglomeration and maintaining active surface
sites. The interaction between copper species and the support affects the electronic properties of
copper, which in turn influences catalyst activity and selectivity.
Recent research shows that catalyst preparation methods critically influence performance. For
example, impregnation with copper nitrate followed by controlled calcination produces highly
dispersed CuCl₂ species. The choice of calcination temperature alters the copper oxidation states
and their distribution on the support, impacting the number of active sites.
Kinetic models based on experimental data confirm that the rate-determining step involves the
reaction of adsorbed ethylene with surface-bound chlorine species, facilitated by copper’s redox
cycling. Optimizing operating parameters such as temperature, gas flow rates, and reactant
concentrations helps maximize VCM yield while minimizing side reactions producing CO, CO₂,
and unwanted chlorinated byproducts.
To improve catalyst lifetime, promoters like potassium and lanthanum ions are incorporated.
These additives modify the catalyst’s surface acidity and basicity, enhancing oxygen activation
and suppressing coke formation, which is a common deactivation pathway. The stability of
copper catalysts under high-temperature industrial conditions has also been improved by nano-
sizing copper particles, which increases active surface area and resistance to sintering.
Incorporation of promoters like potassium and lanthanum ions into copper catalysts has been
shown to enhance oxygen activation and reduce coke formation, further improving catalytic
stability. Research into nano-sized copper catalysts and the use of advanced characterization
methods, including X-ray photoelectron spectroscopy and in situ infrared spectroscopy, have
provided deeper insight into reaction mechanisms and surface phenomena.
Conclusion
Copper-based catalysts remain indispensable for the ethylene oxychlorination process due to
their high catalytic activity, selectivity, and operational stability. Continuous research focused on
catalyst composition, support materials, and preparation methods has led to significant
improvements in catalyst efficiency and environmental sustainability. Understanding the
fundamental mechanisms of copper-catalyzed oxychlorination enables the development of next-
generation catalysts that promise higher performance and reduced ecological footprint.
References
1.
Smith, J., & Lee, A. (2022). Advances in Copper Catalysts for Ethylene Oxychlorination.
Catalysis Today
, 380, 50-65.
2.
Kumar, P., et al. (2021). Influence of Support Materials on Copper Catalyst Activity in
Vinyl Chloride Production.
Journal of Industrial Chemistry
, 89(3), 213-224.
3.
Zhang, W., & Chen, H. (2023). Nano-Copper Catalysts in Oxychlorination Reactions:
Mechanisms and Applications.
Applied Catalysis A
, 650, 117-130.
4.
Lopez, D., et al. (2020). Promoter Effects in Copper-Based Catalysts for Ethylene
Oxychlorination.
Chemical Engineering Journal
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