Kinetic evidence: the rate-determining step for ammonia synthesis over electride-supported Ru catalysts is no longer the nitrogen dissociation step

2017 ◽  
Vol 7 (1) ◽  
pp. 47-50 ◽  
Author(s):  
Yasukazu Kobayashi ◽  
Masaaki Kitano ◽  
Shigeki Kawamura ◽  
Toshiharu Yokoyama ◽  
Hideo Hosono
Keyword(s):  
Ammonia Synthesis ◽  
Surface Reactions ◽  
Ru Catalysts ◽  
Rate Determining Step ◽  
Dissociation Step

The rate-determining step for ammonia synthesis over Ru catalysts supported by electrides, such as [Ca24Al28O64]4+(e−)4 and Ca2N:e−, is suggested to be the surface reactions of N and H adatoms, in which case the Langmuir–Hinshelwood model should be used to describe the kinetics.

Electron Donation by Low-Crystalline Ba-La-Ce Oxygen-Deficient Composite Oxide Accumulating on Ru Nanoparticles for Ammonia Synthesis under Mild Conditions

2019 ◽  
Author(s):  
Katsutoshi Sato ◽  
Shin-ichiro Miyahara ◽  
Yuta Ogura ◽  
Kotoko Tsujimaru ◽  
Yuichiro Wada ◽  
...  
Keyword(s):  
Ammonia Synthesis ◽  
Bond Cleavage ◽  
Synthesis Process ◽  
Strong Electron ◽  
Mild Conditions ◽  
Ru Nanoparticles ◽  
Rate Determining Step ◽  
Highly Active ◽  
Composite Oxides ◽  
Low Crystalline

<p>To mitigate global problems related to energy and global warming, it is helpful to develop an ammonia synthesis process using catalysts that are highly active under mild conditions. Here we show that the ammonia synthesis activity of Ru/Ba/LaCeO<i><sub>x</sub></i> pre-reduced at 700 °C is the highest reported among oxide-supported Ru catalysts. Our results indicate that low crystalline oxygen-deficient composite oxides, which include Ba<sup>2+</sup>, Ce<sup>3+</sup> and La<sup>3+</sup>, with strong electron-donating ability, accumulate on Ru particles and thus promote N≡N bond cleavage, which is the rate determining step for ammonia synthesis.</p>

Electron Donation by Low-Crystalline Ba-La-Ce Oxygen-Deficient Composite Oxide Accumulating on Ru Nanoparticles for Ammonia Synthesis under Mild Conditions

2019 ◽  
Author(s):  
Katsutoshi Sato ◽  
Shin-ichiro Miyahara ◽  
Yuta Ogura ◽  
Kotoko Tsujimaru ◽  
Yuichiro Wada ◽  
...  
Keyword(s):  
Ammonia Synthesis ◽  
Bond Cleavage ◽  
Synthesis Process ◽  
Strong Electron ◽  
Mild Conditions ◽  
Ru Nanoparticles ◽  
Rate Determining Step ◽  
Highly Active ◽  
Composite Oxides ◽  
Low Crystalline

<p>To mitigate global problems related to energy and global warming, it is helpful to develop an ammonia synthesis process using catalysts that are highly active under mild conditions. Here we show that the ammonia synthesis activity of Ru/Ba/LaCeO<i><sub>x</sub></i> pre-reduced at 700 °C is the highest reported among oxide-supported Ru catalysts. Our results indicate that low crystalline oxygen-deficient composite oxides, which include Ba<sup>2+</sup>, Ce<sup>3+</sup> and La<sup>3+</sup>, with strong electron-donating ability, accumulate on Ru particles and thus promote N≡N bond cleavage, which is the rate determining step for ammonia synthesis.</p>

Improved ammonia synthesis activity of Ce doped barium tantalate supported Ru catalysts

2021 ◽  
Author(s):  
Jia Huang ◽  
Yushi Zhao ◽  
Mingwei Yuan ◽  
Jinjun Li ◽  
Zhixiong You
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ammonia Synthesis ◽  
Ru Catalysts ◽  
Synthesis Activity

Ce doping could increase the specific surface area and reducibility of the barium tantalate carrier, which is beneficial to Ru based ammonia synthesis.

scholarly journals Effect of pore structure of mesoporous carbon on its supported Ru catalysts for ammonia synthesis

2013 ◽  
Vol 34 (7) ◽  
pp. 1395-1401 ◽  
Author(s):  
Yaping ZHOU ◽  
Guojun LAN ◽  
Bin ZHOU ◽  
Wei JIANG ◽  
Wenfeng HAN ◽  
...  
Keyword(s):  
Pore Structure ◽  
Mesoporous Carbon ◽  
Ammonia Synthesis ◽  
Ru Catalysts

scholarly journals Barium Oxide Encapsulating Cobalt Nanoparticles Supported on Magnesium Oxide: Active Non-noble Metal Catalyst for Ammonia Synthesis under Mild Reaction Condition

2021 ◽  
Author(s):  
Katsutoshi Sato ◽  
Shin-ichiro Miyahara ◽  
Kotoko Tsujimaru ◽  
Yuichiro Wada ◽  
Takaaki Toriyama ◽  
...  
Keyword(s):  
Triple Bond ◽  
Density Functional ◽  
Ammonia Synthesis ◽  
Metal Catalyst ◽  
Synthesis Rate ◽  
Rate Determining Step ◽  
Scanning Transmission ◽  
Synthesis Activity ◽  
And Migration ◽  
Co Nanoparticles

<p>To realize a sustainable, carbon-free society, catalysts for the synthesis of ammonia using renewable energy under mild reaction conditions (<400 °C, <10 MPa) are needed. Ru-based catalysts are currently the most promising candidates; however, Ru is expensive and of low abundance. Here, we discovered that encapsulation of Co nanoparticles with BaO enhanced the ammonia synthesis activity of the Co, and that a simple Ba-doped Co/MgO catalyst pre-reduced at an unusually high temperature of 700 °C (Co@BaO/MgO-700red) showed outstanding ammonia synthesis activity. <a>The ammonia synthesis rate (24.6 mmol g<sub>cat</sub></a><sup>−</sup><sup>1</sup> h<sup>−</sup><sup>1</sup>) and turnover frequency (0.255 s<sup>−</sup><sup>1</sup>) of the catalyst at 350 °C and 1.0 MPa were 22 and 64 times higher, respectively, than those of the non-doped parent catalyst. At the same temperature but higher pressure (3.0 MPa), the ammonia synthesis rate was increased to 48.4 mmol g<sub>cat</sub><sup>−</sup><sup>1</sup> h<sup>−</sup><sup>1</sup>, which is higher than that of active Ru-based catalysts. Scanning transmission electron microscopy and energy dispersive X-ray spectrometry investigations revealed that after reduction at 700 °C the Co nanoparticles had become encapsulated by a nano-fraction of BaO. The mechanism underlying the formation of this unique structure was considered to comprise reduction of oxidic Co to metallic Co, decomposition of BaCO<sub>3</sub> to BaO, and migration of BaO to the Co nanoparticle surface. Spectroscopic and density-functional theory investigations revealed that adsorption of N<sub>2</sub> on the Co atoms at the catalyst surface weakened the N<sub>2</sub> triple bond to the strength of a double bond due to electron donation from the Ba atom of BaO <i>via</i> adjacent Co atoms; this weakening accelerated cleavage of the triple bond, which is the rate-determining step for ammonia synthesis.</p>

Carbon covered Mg–Al hydrotalcite supported nanosized Ru catalysts for ammonia synthesis

2016 ◽  
Vol 411 ◽  
pp. 157-166 ◽  
Author(s):  
Katabathini Narasimharao ◽  
Podila Seetharamulu ◽  
K.S. Rama Rao ◽  
Sulaiman N. Basahel
Keyword(s):  
Ammonia Synthesis ◽  
Ru Catalysts

KOH Activation of Thermally Modified Carbon as a Support of Ru Catalysts for Ammonia Synthesis

ChemCatChem ◽  
2013 ◽  
Vol 5 (7) ◽  
pp. 1941-1947 ◽  
Author(s):  
Bingyu Lin ◽  
Kemei Wei ◽  
Jun Ni ◽  
Jianxin Lin
Keyword(s):  
Ammonia Synthesis ◽  
Koh Activation ◽  
Ru Catalysts

Sm-promoted alumina supported Ru catalysts for ammonia synthesis: Effect of the preparation method and Sm promoter

2011 ◽  
Vol 12 (6) ◽  
pp. 553-558 ◽  
Author(s):  
Bingyu Lin ◽  
Rong Wang ◽  
Jianxin Lin ◽  
Jun Ni ◽  
Kemei Wei
Keyword(s):  
Preparation Method ◽  
Ammonia Synthesis ◽  
Ru Catalysts
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