2022-08-02 バッファロー大学(UB)
しかし、乾式改質が実用化されるためには、新しい触媒や改良された触媒が必要である。
バッファロー大学が主導して6月に発表した2つの研究では、ニッケルベースの触媒を製造するための新しい方法が報告されており、長年の課題を克服する可能性があることが示されています。。
既存のニッケル系触媒は、触媒活性粒子が炭素で覆われたり（コーキング）、結合してより大きな活性の低い粒子になったり（シンタリング）して機能しなくなるため、メタンの乾式改質は商業的に成立しないとスィハート教授は説明する。また、最も有望な触媒は、複雑な製造工程を必要とする。
そこで研究チームは、低コストで高性能な触媒を製造するためのワンステップエアロゾルプロセスを開発した。このプロセスは、スウィハート教授の研究室で開発された独自の火炎反応器をベースにしている。
研究チームは、この反応器を用いて、コーキングやシンタリングに強いナノシェルと呼ばれる球状の微粒子を作製することに成功した。
この触媒は500時間以上にわたって効果を維持し、メタンの98%を合成ガスに変換した。合成ガスは水素と一酸化炭素の混合物で、その後さまざまな化学製品の製造に使用することができる。
さらに、このリアクターを使って、1グラムあたり1,000平方メートルを超える表面積を持つ新しいメソポーラスシリカを作製した。さらに、ニッケルなどのナノ粒子をメソポーラスシリカの中に蒸着する方法（in-situ deposition）も開発した。
このメソポーラスシリカ触媒は、200時間以上にわたってメタンを97%変換した。
＜関連情報＞
- https://www.buffalo.edu/news/releases/2022/08/002.html
- https://www.sciencedirect.com/science/article/abs/pii/S2667109322002470
- https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202206870
メタンの乾式改質用超安定Ni-ZrO2ナノシェル触媒の火炎合成とNi溶出による作製 Producing ultrastable Ni-ZrO2 nanoshell catalysts for dry reforming of methane by flame synthesis and Ni exsolution
Shuo Liu,Chaochao Dun,Mihir Shah,Junjie Chen,Satyarit Rao,Jilun Wei,Eleni A.Kyriakidou,Jeffrey J.Urban,Mark T.Swihart
Chem Catalysis Published: June 1, 2022
DOI:https://doi.org/10.1016/j.checat.2022.05.013
Highlights
- •Incorporation of NiO and ZrO2 into a single phase by rapid flame synthesis
- •Exsolution of active Ni nanoparticles leads to stable catalyst formation
- •High sintering and coking resistance of Ni-ZrO2 nanoshell catalyst
- •Maintains 98% CH4 conversion over more than 500 h for dry reforming of methane
The bigger picture
Dry reforming of methane, which converts two greenhouse gases to useful chemical feedstocks, has been regarded as a promising strategy to address global climate change and sustainable energy development. Design of effective nonnoble metal catalysts is key to achieving its industrial implementation. However, conventional Ni-based catalysts often suffer from deactivation by carbon coking and metal sintering, while complex catalyst synthesis approaches inevitably lead to high cost. This work presents a continuous, one-step, vapor-phase synthesis route to produce a highly stable Ni/ZrO2 nanoshell catalyst with excellent resistance to both coking and sintering. The methods proposed in this work are expected to expand routes to heterogeneous catalyst synthesis with impact on both scientific and industrial communities.
Summary
Commercial dry reforming of methane (DRM) is limited by catalyst deactivation through metal sintering and coking. New catalyst synthesis methods are needed to overcome such challenges. Here, we report a unique flame aerosol synthesis and exsolution method for producing hollow Ni-Zr oxide nanoshells as a highly stable and efficient DRM catalyst. This process incorporates immiscible elements into single-phase hollow nanoshells by rapid particle formation and quenching. Ni nanoparticles are then uniformly exsolved from the metastable solid solution to provide strong metal-support interactions that limit metal sintering. Rapid synthesis under reducing conditions produces oxygen vacancies in ZrO2 that favor carbon removal during the DRM reaction. As a result, our catalyst maintained 98% CH4 conversion for more than 500 h, without sintering or coking, dramatically outperforming conventional catalysts. This method of metastable solid solution nanoshell formation followed by active site exsolution could provide durable catalysts for many high-temperature reactions.
メソポーラスシリカの火炎エアロゾル合成とその場での機能化に関する一般的なルート A General Route to Flame Aerosol Synthesis and In Situ Functionalization of Mesoporous Silica
Shuo Liu,Dr. Chaochao Dun,Dr. Junjie Chen,Satyarit Rao,Mihir Shah,Jilun Wei,Kaiwen Chen,Zhengxi Xuan,Prof. Eleni A. Kyriakidou,Dr. Jeffrey J. Urban,Prof. Mark T. Swihart
Angewandte Chemie Published: 30 June 2022
DOI:https://doi.org/10.1002/anie.202206870
Abstract
A continuous flame aerosol route to synthesize hollow structured mesoporous silica nanoparticles is presented, and a general in situ functionalization mechanism for loading highly dispersed catalytically active sites is proposed. Multiple applications are addressed in this class of material, including heterogeneous catalysis, dye adsorption, drug delivery, and thermal insulation.
Mesoporous silica is a versatile material for energy, environmental, and medical applications. Here, for the first time, we report a flame aerosol synthesis method for a class of mesoporous silica with hollow structure and specific surface area exceeding 1000 m2 g−1. We show its superior performance in water purification, as a drug carrier, and in thermal insulation. Moreover, we propose a general route to produce mesoporous nanoshell-supported nanocatalysts by in situ decoration with active nanoclusters, including noble metal (Pt/SiO2), transition metal (Ni/SiO2), metal oxide (CrO3/SiO2), and alumina support (Co/Al2O3). As a prototypical application, we perform dry reforming of methane using Ni/SiO2, achieving constant 97 % CH4 and CO2 conversions for more than 200 hours, dramatically outperforming an MCM-41 supported Ni catalyst. This work provides a scalable strategy to produce mesoporous nanoshells and proposes an in situ functionalization mechanism to design and produce flexible catalysts for many reactions.
