Era Kohei, Sato Katsutoshi, Miyahara Shin-Ichiro, Naito Takahiro, De Silva Kanishka, Akrami Saeid, Yamada Hiroshi, Toriyama Takaaki, Yamamoto Tomokazu, Murakami Yasukazu, Aika Ken-Ichi, Inazu Koji, Nagaoka Katsutoshi
Department of Chemical Systems Engineering, Graduate school of Engineering, Nagoya University Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan.
Institute for Advanced Research, Nagoya University Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan.
ChemSusChem. 2023 Nov 22;16(22):e202300942. doi: 10.1002/cssc.202300942. Epub 2023 Nov 14.
An important part of realizing a carbon-neutral society using ammonia will be the development of an inexpensive yet efficient catalyst for ammonia synthesis under mild reaction conditions (<400 °C, <10 MPa). Here, we report Fe/K(3)/MgO, fabricated via an impregnation method, as a highly active catalyst for ammonia synthesis under mild reaction conditions (350 °C, 1.0 MPa). At the mentioned conditions, the activity of Fe/K(3)/MgO (17.5 mmol h g ) was greater than that of a commercial fused iron catalyst (8.6 mmol h g ) currently used in the Haber-Bosch process. K doping was found to increase the ratio of Fe on the surface and turnover frequency of Fe in our Fe/K(3)/MgO catalyst. In addition, increasing the pressure to 3.0 MPa at the same temperature led to a significant improvement of the ammonia synthesis rate to 29.6 mmol h g , which was higher than that of two more expensive, benchmark Ru-based catalysts, which are also potential alternative catalysts. A kinetics analysis revealed that the addition of K enhanced the ammonia synthesis activity at ≥300 °C by changing the main adsorbed species from NH to N which can accelerate dissociative adsorption of nitrogen as the rate limiting step in ammonia synthesis.
利用氨实现碳中和社会的一个重要部分将是开发一种在温和反应条件（<400°C，<10 MPa）下廉价且高效的氨合成催化剂。在此，我们报告通过浸渍法制备的Fe/K(3)/MgO，作为在温和反应条件（350°C，1.0 MPa）下氨合成的高活性催化剂。在上述条件下，Fe/K(3)/MgO的活性（17.5 mmol h g ）高于目前哈伯-博施法中使用的商业熔铁催化剂（8.6 mmol h g ）。发现在我们的Fe/K(3)/MgO催化剂中，K掺杂增加了表面Fe的比例和Fe的周转频率。此外，在相同温度下将压力提高到3.0 MPa导致氨合成速率显著提高到29.6 mmol h g ，这高于另外两种更昂贵的基准Ru基催化剂，它们也是潜在的替代催化剂。动力学分析表明，添加K通过将主要吸附物种从NH变为N来增强≥300°C时的氨合成活性，这可以加速氮的解离吸附，而氮解离吸附是氨合成中的速率限制步骤。
