排ガスからアンモニア資源を製造、社会実装に向けた活動を加速－有害な窒素酸化物（NOx）からアンモニア（NH3）資源を回収する技術、ベンチスケールの実証試験に成功－

2026-10-07 産業技術総合研究所

産業技術総合研究所（産総研）は、火力発電所やごみ焼却場などの排ガスに含まれる窒素酸化物（NOx）を、無害な窒素に戻すのではなく、有価資源であるアンモニア（NH₃）へ変換する「吸蔵NTA反応」のベンチスケール実証に成功した。NOxを触媒で捕捉した後、水素を含む還元ガスに切り替えてNH₃へ変換する仕組みで、排ガス浄化と資源回収を同時に実現する。独自のBaO/Pt@mAl₂O₃ナノ複合触媒をハニカム・ペレット化し、ラボスケールの約100倍となる反応器で検証。ペレット触媒ではNH₃化率約60％、ガス流量を下げ接触時間を確保した条件では約90％を達成した。今後はパイロット規模への大型化、実排ガスへの適用、LCA評価を進め、窒素資源循環と環境負荷低減への実装を目指す。

※原論文の図を引用・改変したものを使用しています。

＜関連情報＞

BaO/Pt/γ- Al₂O₃を用いたガス切り替え型NOx貯蔵還元プロセスにおけるNH₃合成のためのPt触媒のサイズ依存性特性 Size-dependent properties of Pt catalysts for the synthesis of NH3 during a gas-switching NOx storage and reduction process using BaO/Pt/γ-Al2O3

Atsuko Tomita;Ryutaro Wakabayashi;Tatsuo Kimura
Catalysis Science & Technology Published:16 September 2025
DOI:https://doi.org/10.1039/d5cy00778j

Nitrogen oxides (NO_x), though harmful, serve as an effective nitrogen source owing to their higher reactivity compared to atmospheric nitrogen (N₂). For example, an alternate gas-switching process has been proposed in which NO_x is stored and then reduced by hydrogen (H₂) at a constant temperature below 300 °C, enabling the selective synthesis of valuable ammonia (NH₃). In this study, we demonstrated the size-dependent properties of a platinum (Pt) catalyst for further understanding the activation of H₂ and subsequent hydrogenation of stored NO_x in the reduction process using systematically designed BaO/Pt/γ-Al₂O₃ type nanocomposite catalysts. The hydrogenation rate over γ-Al₂O₃ was governed almost completely by the size of the resulting Pt nanoparticles (NPs), which could be tuned solely by adjusting the reaction temperature; the catalytic properties in activation of H₂ followed the same trend. The formation of N₂ progressed preferentially with the rapid hydrogenation of stored NO_x by highly active (smaller) Pt NPs, which is not contradictory to the fact that sufficient but slow hydrogenation of stored NO_x was helpful for the synthesis of NH₃ by activity-controlled (larger) Pt NPs. Consequently, in the presence of sufficient H₂, more than 90% of stored NO_x can be recovered as NH₃ above 200 °C by using BaO/Pt/γ-Al₂O₃ containing large Pt NPs. This knowledge has potential for the design of high-performance nanocomposite catalysts to produce starting NH₃ for value-added chemicals and CO₂-free fuels as strategic chemicals in the future society.

窒素循環経済における反応性窒素化合物の利用 Utilization of Reactive Nitrogen Compounds for Nitrogen Circular Economy

Dr. Tatsuo Kimura
The Chemical Record Published: 02 August 2024
DOI:https://doi.org/10.1002/tcr.202400094

Abstract

Nitrogen oxides (NO_x) should be purified according to environmental regulations, being restricted increasingly year by year. A wide variety of denitration technologies, such as selective catalytic reduction (SCR) of NO_x to nitrogen (N₂) and NO_x storage reduction (NSR) to N₂ by injecting reducing agents like ammonia (NH₃), has so far been developed practically. Sophisticated catalytic approaches are perhaps mandatory for the sustainability in energy including complete purification of NO_x. As one of the solutions to overcome problems for environment and resource simultaneously, this concept article focuses on the utilization of reactive nitrogen (N_r) compounds, mainly NO_x, for encouraging an opening to consider nitrogen circular economy. For the recycling of NO_x via NH₃, a challenging but rational catalytic technology can be proposed by an alternate switching the inlet gas between NO_x containing oxidative gas and H₂ containing reductive one without an operation to change the reaction temperature. Considering the reactivity of NO_x higher than that of N₂, this kind of NO_x to NH₃ (NTA) process is promising for synthesizing NH₃, being valuable not only as fertilizer but also as fuel in near future.

固体硝酸塩を介したアンモニアへの触媒変換：窒素酸化物の新たな利用法の提案 Catalytic conversion to ammonia through solid-state nitrate as a proposal for the emerging usage of nitrogen oxides

Atsuko Tomita;Ryutaro Wakabayashi;Tatsuo Kimura
Catalysis Science & Technology Published:27 February 2023
DOI:https://doi.org/10.1039/d3cy00169e

Nitrogen oxides, NOx, that arise anthropogenically from combustion at high temperature using air are serious byproducts that cause air pollution. Here, we propose a catalytic conversion system by alternate switching of inlet gas from NOx containing O₂-rich combustion gas (e.g., 1000 ppm NO + 10% O₂) to NO/O₂-free reduction one (e.g., 1% H₂). According to this gas-switching operation, solid-state nitrate, stored with alkali earth metal species, was converted to gaseous NH₃ under ambient pressure, which would possibly be useful for solving the nitrogen crisis as well as constructing a new industrial structure of a circular nitrogen economy. Large Pt nanoparticles inside mesoporous alumina particles, created by an aerosol-assisted one-pot synthesis with Pt sources followed by calcination at high temperature (e.g., 850 °C), were helpful for shifting the efficient-working temperature to a higher region. A Ba/Pt@mAl₂O₃(γ) type nanocomposite catalyst worked very well at 250 °C and higher. Selectivity for NH₃ reached 90%, and was also achieved using Ca/Pt@mAl₂O₃(γ), without a high-energy process like the cleavage of N₂.