Commercialization of Nitrogen Oxides Removal Technology, a Major Cause of Fine Dust, Gets 'Green Light'

KIST Proposes Vanadate-Based Nitridation Catalyst
Maintains High Efficiency at Ultra-Low Temperatures, Strong Sulfur Durability

[Asia Economy Reporter Kim Bong-su] Domestic researchers have developed a new technology to remove nitrogen oxides (NOX) from exhaust gases. The technology maintains high efficiency even at low temperatures and exhibits strong durability against sulfur (SOX) components, addressing the weaknesses of existing technologies.

The Korea Institute of Science and Technology (KIST) announced on the 15th that the research team led by Dr. Kim Jong-sik and Dr. Ha Heon-pil at the Extreme Materials Research Center proposed a vanadate-based new denitrification catalyst and developed a technology that achieves high denitrification performance and high durability against sulfur even at ultra-low temperatures by modifying the catalyst surface using sulfur.

The denitrification catalyst process is a technology that reduces nitrogen oxides (NOX), a representative cause of ultrafine dust contained in exhaust gases, into nitrogen to improve air quality. Reducing the enormous thermal energy required to activate the denitrification catalyst and securing durability against sulfur (SOX)-based poisons contained in exhaust gases are the biggest challenges in developing denitrification catalysts.

Existing research trends related to denitrification catalysts focused on selecting vanadium, transition metals, and rare earth metal oxides and finding the optimal physical combination conditions (composition, oxidation conditions, combination order, etc.) based on metal oxides.

In contrast, the KIST research team proposed a "metal vanadate-based" denitrification catalyst research that chemically fuses vanadium oxides and metal oxides. The team revealed that compared to conventional metal oxide-based catalysts, vanadate catalysts have superior catalytic surface, atomic, and electronic properties and denitrification activity, improving the decline in catalyst performance caused by vapor, sulfur, and poisons in exhaust gases, as well as enhancing resistance to hydro-thermal aging.

The researchers shifted the perception of sulfur (SOX), known to poison catalysts and reduce durability, by fusing sulfur and oxygen to generate sulfate and sulfite functional groups on the vanadate catalyst surface. They devised a methodology to control these generated functional groups to regulate denitrification reactions and poison decomposition reaction activities. By changing the temperature of the catalyst surface where sulfur and oxygen fuse, they controlled the types, distribution, and surface bonding configurations (monodentate or bidentate bonding) of the functional groups and elucidated the mechanism of poison decomposition reactions.

Vanadate catalysts with abundant monodentate bonding or sulfates provide a denitrification rate 30% higher than commercial catalysts at ultra-low temperatures (210℃) and nearly 100% denitrification rate above 220℃. Vanadate catalysts with abundant bidentate bonding can efficiently decompose poisons at lower thermal energy (lower temperature) compared to commercial catalysts, resulting in at least three times greater durability. For example, when the exhaust gas temperature is set to 240℃, the bidentate-rich vanadate catalyst smoothly decomposes poisons and recovers (regenerates) the denitrification rate, whereas commercial catalysts struggle to decompose poisons and cannot restore the denitrification rate prior to poisoning.

Dr. Kim Jong-sik of KIST explained, “Vanadates can be processed into various crystal phases by controlling the type of metal and the chemical stoichiometric ratio between vanadium and metal. When fused with sulfate and sulfite functional groups, tailored enhancement of denitrification ability, regeneration ability, and durability is possible,” adding, “This is a practical technology that can meet the diverse demands of denitrification processes operating under extreme conditions where temperatures are low or catalysts are easily poisoned.”

The research results were published in the latest issues of the international chemistry journals ‘ACS Catalysis’ and ‘Chemistry of Materials.’

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