Structure sensitivity of ammonia synthesis over promoted ruthenium catalysts supported on graphitised carbon

Raróg‐Pilecka, Wioletta; Miśkiewicz, Elżbieta; Szmigiel, Dariusz; Kowalczyk, Z.

doi:10.1016/j.jcat.2004.12.005

Cited by 167 publications

(92 citation statements)

References 54 publications

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“…The average size of Ru over HSAG was found to be among the range of 1.0-3.0 nm, which are the suitable sizes for the formation of so-called B 5 site. It is generally accepted that ammonia synthesis is a structure-sensitive reaction [27,28] and B 5 site is the most efficient Ru structure for ammonia synthesis [28,29]. Larger Ru particle sizes were observed over activated carbon supported catalyst.…”

Section: Dispersion Of Ru Catalystmentioning

confidence: 98%

Preparation of efficient ruthenium catalysts for ammonia synthesis via high surface area graphite dispersion

Han

Yan

Tang

et al. 2014

Reac Kinet Mech Cat

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High surface area graphite (HSAG) was tested as a support of ruthenium catalyst for ammonia synthesis. As it is in the form of fine powder, it can be dispersed in the ruthenium precursor solution achieving high dispersion of Ru and efficiency. The surface area, porosity, crystalline structure of support, morphology, dispersion of Ru, desorption of H 2 and N 2 and methanation of the catalyst were investigated by N 2 physisorption, XRD, SEM, TEM and TPD/TPSR techniques. The results show that higher ammonia synthesis rates of the HASG catalyst compared to activated carbon can be achieved with the assistance of ultrasonic treatment. As expected, the methanation rate over HSAG is much lower than that of activated carbon over the whole temperature range studied.

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Section: Dispersion Of Ru Catalystmentioning

confidence: 98%

Preparation of efficient ruthenium catalysts for ammonia synthesis via high surface area graphite dispersion

Han

Yan

Tang

et al. 2014

Reac Kinet Mech Cat

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“…Compared with the other recently reported metal particle/graphene composites, the Ru/graphene composites prepared in the present work also showed much smaller and more uniform metallic particles [7,8], indicating the formation of high-quality Ru/graphene composites. Due to the structure-sensitive feature of ammonia decomposition on Ru [31,32], the Ru/graphene prepared from the CS system simultaneously allowed good control of the Ru particle size and shape on graphene nanosheets even at extremely high levels of Ru loading (>50 wt %), which was favorable for highly enhanced catalytic activity for ammonia decomposition. Carbon nanotubes (CNTs) were thought to provide very efficient support for ammonia decomposition [35][36][37][38] because of their high surface area and excellent electronic conductive properties.…”

Section: Preparation Of Ru/graphene Nanocompositesmentioning

confidence: 99%

“…On the other hand, CS-40, CS-60, and CS-80 Ru/graphene nanocomposites showed almost the same catalytic performance, although the variation in Ru loading in the nanocomposites occurred over a wide range, the Ru particle size and shape were the same. However, with comparable, or even much lower, levels of Ru loading, the Ru/graphene nanocomposites prepared in a CS system showed much better catalytic performance than those prepared in a SS system, which was attributed mainly to the improved Ru dispersions as well as to the optimal Ru microstructures, since the ammonia decomposition on Ru is structure-sensitive [31,32]. Figure 7 shows the catalytic performance of CS-60 Ru/graphene at 450 °C under different GHSVs.…”

Section: Preparation Of Ru/graphene Nanocompositesmentioning

confidence: 99%

“…Although research effort focused on the catalysis of ammonia decomposition has increased rapidly in recent years [21][22][23][24][25][26][27][28][29][30], and the catalytic activity of current catalysts still requires significant improvement because the current level of ammonia conversion remains much lower than the equilibrium, particularly at reaction temperatures lower than 400 • C. Research progress has identified that Ru is currently the most active component for ammonia decomposition. The control of Ru particles with optimal size and morphology is very important in ammonia decomposition since ammonia decomposition with Ru is structure-sensitive due to the variation of highly active B 5 -type sites [31,32]. These sites arrange three Ru atoms in one layer with two more in the layer directly above, which amounts to a monoatomic step on a Ru (0001) terrace for different structures [33,34].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Catalytic Ammonia Decomposition over High-Performance Ru/Graphene Nanocomposites for Efficient COx-Free Hydrogen Production

Kanezashi

Tsuru

2017

Catalysts

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Highly-dispersed Ru nanoparticles were grown on graphene nanosheets by simultaneously reducing graphene oxide and Ru ions using ethylene glycol (EG), and the resultant Ru/graphene nanocomposites were applied as a catalyst to ammonia decomposition for CO x -free hydrogen production. Tuning the microstructures of Ru/graphene nanocomposites was easily accomplished in terms of Ru particle size, morphology, and loading by adjusting the preparation conditions. This was the key to excellent catalytic activity, because ammonia decomposition over Ru catalysts is structure-sensitive. Our results demonstrated that Ru/graphene prepared using water as a co-solvent greatly enhanced the catalytic performance for ammonia decomposition, due to the significantly improved nano architectures of the composites. The long-term stability of Ru/graphene catalysts was evaluated for CO x -free hydrogen production from ammonia at high temperatures, and the structural evolution of the catalysts was investigated during the catalytic reactions. Although there were no obvious changes in the catalytic activities at 450 • C over a duration of 80 h, an aggregation of the Ru nanoparticles was still observed in the nanocomposites, which was ascribed mainly to a sintering effect. However, the performance of the Ru/graphene catalyst was decreased gradually at 500 • C within 20 h, which was ascribed mainly to both the effect of the methanation of the graphene nanosheet under a H 2 atmosphere and to enhanced sintering under high temperatures.

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“…Rising the temperature of a solid will result in the increase of the thermal vibrations of atoms and with this the atomic magnetic moments are free to rotate. Due to this phenomenon, the atoms tend to randomize the directions of any moments that may be aligned [6]. With increasing temperature, the saturation magnetization diminishes gradually and abruptly drops to zero at the Curie temperature (T).…”

Section: Magnetization Versus Temperaturementioning

confidence: 99%

Ammonia Synthesis Using Magnetically Induced Reaction

Yahya

Puspitasari

Noordin

2013

DDF

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Abstract. Ammonia production is a high energy and capital intensive industry as it requires high temperature (400-500 o C) and high pressure (150-300 bar) for its daily operations. By introducing nano-catalyst with the new concept of micro-reactor with applied magnetic field induction, the catalytic activity can be induced and the output can be enhanced. Magneto-dynamics will be introduced in the ammonia production process in order to replace the concept of thermodynamics in the Haber Bosch process. The nanocatalysts (Y 3 Fe 5 O 12 , Fe 2 O 3 , MnO, Mn 0.8 Zn 0.2 Fe 2 O 4 ) have been reduced by using the temperature reduction method (TPR). The Y 3 Fe 5 O 12 (YIG) catalyst with magnetic induction produced242.56µmol/h.g-cat output of ammonia which is 2% much higher than ammonia synthesis without magnetic induction (237.52 µmol/g.h).The ammonia output based on the magnetic induction method at a temperature of 0°C is 242.56µmole/h.g-cat which is 0.90% higher than the synthesis at 25°C temperature (240.4 µmol/g.h). The ammonia output at 0.2Tesla is 249.04 µmole/h.g-cat which is higher 2.6% than the output at 0.1Tesla which is 242.56µmol/g.h. It is proven that the higher the applied magnetic field is, the more effective the catalytic activity will be as a better alignment of the electron spin of the catalyst occurs and enhances the adsorption and desorption process. Y 3 Fe 5 O 12 (YIG) shows the best catalytic reaction followed by Fe 2 O 3 (hematite) and MnO (manganese oxide). By this new route, synthesis of ammonia at low temperature is realized and offers ammonia producers an economic advantage compared to the classical routes.

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Structure sensitivity of ammonia synthesis over promoted ruthenium catalysts supported on graphitised carbon

Cited by 167 publications

References 54 publications

Preparation of efficient ruthenium catalysts for ammonia synthesis via high surface area graphite dispersion

Preparation of efficient ruthenium catalysts for ammonia synthesis via high surface area graphite dispersion

Catalytic Ammonia Decomposition over High-Performance Ru/Graphene Nanocomposites for Efficient COx-Free Hydrogen Production

Ammonia Synthesis Using Magnetically Induced Reaction

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