Key Takeaways & Executive Findings
- •• • MoVTeNbOx mixed oxides achieve >80% selectivity to ethylene in ethane ODH at ~400°C, but conversion remains <30%, underscoring the conversion–selectivity trade-off that limits industrial viability. • • Silver-based catalysts for propylene epoxidation, such as Ag-MoO3/ZrO2, exhibit propylene oxide selectivity up to 50–60% at low conversion (<5%), with chloride modification enhancing selectivity but posing corrosion risks. • • Copper-based catalysts, including Cu2O nanocrystals with controlled {100} facets, achieve propylene oxide selectivity >60% at ~200°C, but require precise facet engineering to suppress combustion. • • In situ UV-vis studies reveal that electrophilic oxygen species (O2−, O−) favor epoxidation, while nucleophilic O2− leads to combustion; controlling their dynamic evolution is critical for selectivity.
Abstract
Catalytic oxidation is a pivotal technology for the valorization of light hydrocarbons, with oxidative dehydrogenation (ODH) and epoxidation using molecular oxygen attracting significant interest due to high atom economy and environmental friendliness. This review systematically summarizes recent advances in the oxidative dehydrogenation of light alkanes (ethane, propane) and aerobic epoxidation of light olefins (ethylene, propylene). For rational catalyst design, it elaborates on performance regulation strategies for metal oxide catalysts such as MoVNbTeOx mixed oxides, NiO-based, and V-based systems, as well as carbon/boron-based non-metal catalysts in alkane ODH, and silver- and copper-based catalysts in alkene epoxidation. Strategies include regulating the oxidation state of active sites, exploiting strong metal-support interactions, engineering particle size and crystal facets, and promoter modification. At the mechanistic level, combining density functional theory calculations with in situ characterization, the review examines C–H bond activation and alkene desorption pathways in ODH, and oxygen insertion routes and competing side reactions in epoxidation. Special attention is given to the dynamic evolution of electrophilic and nucleophilic oxygen species and their decisive role in selectivity. Persistent challenges include suppressing over-oxidation and overcoming the conversion–selectivity trade-off. Future directions propose precise design of active centers, development of inherently safer processes, and in-depth analysis of complex reaction networks, supporting the green transition of the chemical industry.
1. Introduction
Light olefins (C2–C4) are essential feedstocks for producing high-value chemicals such as ethylene oxide, propylene oxide, and acrylonitrile. Conventional production via naphtha steam cracking or fluidized catalytic cracking suffers from broad product distributions, leading to high energy consumption and separation costs. Direct dehydrogenation of alkanes is industrialized but requires high temperatures and suffers from thermodynamic limitations. Heterogeneous aerobic oxidation offers a promising alternative, enabling selective C–H activation and oxygen insertion under milder conditions, but achieving high selectivity remains a bottleneck due to over-oxidation and the trade-off between conversion and selectivity.
This review addresses these challenges by systematically analyzing catalyst design strategies for oxidative dehydrogenation and epoxidation. It focuses on tuning active site oxidation states, exploiting metal-support interactions, and engineering crystal facets to control oxygen species. Mechanistic insights from DFT and in situ characterization reveal how electrophilic oxygen species promote selective oxidation, guiding the rational design of catalysts with improved performance. The review also highlights persistent challenges and future directions, aiming to support the green transition of the chemical industry.
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ZENG Zhuang, LI Bin, XIA Changjiu, ZHANG Xiaoxin (2026). Research Progress on Catalyst Design and Reaction Mechanisms for Heterogeneous Oxygen Oxidation of Light Hydrocarbons. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60660-3
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Frequently Asked Questions
What are the primary deactivation mechanisms for MoVNbTeOx catalysts under industrial ODH conditions?
MoVNbTeOx catalysts can undergo phase segregation and volatilization of tellurium at temperatures above 400°C, leading to loss of active M1 phase and reduced selectivity. Additionally, coke deposition on acid sites can block active centers, requiring periodic regeneration.
How does the addition of chloride promoters to Ag catalysts affect propylene epoxidation selectivity and long-term stability?
Chloride promoters, such as in Ag-MoO3/ZrO2, enhance propylene oxide selectivity by modifying the electronic state of silver and suppressing combustion. However, chloride can migrate and cause corrosion, leading to gradual deactivation. Stability depends on maintaining optimal Cl coverage, which requires careful process control.
What is the industrial feasibility of using Cu2O nanocrystals for propylene epoxidation, considering scalability and cost?
Cu2O nanocrystals with controlled facets show high selectivity (>60%) but require complex synthesis and are prone to sintering under exothermic conditions. Scalability is limited by the need for precise facet control and the cost of nanocrystal production. Current performance does not yet meet industrial requirements for conversion and stability.
How do electrophilic and nucleophilic oxygen species influence selectivity in ODH and epoxidation, and how can they be controlled?
Electrophilic oxygen species (O2−, O−) are associated with selective oxidation, while nucleophilic O2− leads to total oxidation. Their formation is influenced by metal–oxygen bond strength and support acidity. Strategies include doping with promoters to modify electron density and using supports that stabilize electrophilic species, as evidenced by in situ UV-vis studies.
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