26 February 2016
Valerii Bukhtiyarov, director of Boreskov Institute of Catalysis (Novosibirsk), reported on the prospects of using the renewable vegetable stock in the fuel and petrochemical complex of Tatarstan
Methane is the main component of natural gas and problems of its rational utilization are rather urgent. Many routes of methane conversion have been suggested like,
for example, steam reforming, oxidative and non-oxidative coupling on 3d-metal catalysts. Recently we have established that methane decomposition over 3d
It was shown that Ni and Co catalysts have high activity in CFC accumulation at temperatures 500-550°C. In order to compare the carbon formation efficiency of prepared
catalysts, we use the following parameters of a methane decomposition reaction: methane conversion (x, %), carbon accumulation until complete deactivation of the
catalysts (the so called carbon capacity G, calculated as gram of carbon per gram of catalyst or metal) and lifetime of catalysts
We found that a large amounts of filamentous carbon can be produced using coprecipitated catalysts:
It is known that application of alloys in catalysis opens new interesting opportunities, since the introduction of the second metal in catalytic system can sharply change both activity, and selectivity of the catalyst in comparison with individual metals. Our present work is focused on investigation of alloy catalysts in methane decomposition reaction and physicochemical properties of formed CFC.
a) - Ni (graphite layers stack at a ~ 45° to filament axis),
b) - Ni-Cu (a ~ 90°),
c) - Co (a ~ 15°),
d) - Fe (a ~ 0°),
e) - Fe-Co (a ~ 0°)
The addition of Cu into Ni catalyst changes the crystallographic orientation of the catalyst particles (. 1b) and as a consequence changes microstructural and textural properties of formed CFC. As a result, the thermal stability and carbon capacity (which can reach 700 g/gNi at temperatures ~675°C) of Ni-Cu increase [1,4].
It is also established that Co, Ni additives render activating influence on Fe catalysts, which becomes apparent in decrease of the methane decomposition temperature and the formation of multiwall carbon nanotubes (MWNTs), and carbon capacity can achieve 105 g/gFe .
Table shows the catalytic properties of the investigated catalysts and the CFC textural characteristics The typical global kinetics of the methane decomposition over the catalysts are illustrated.
|catalyst||Decomposition of СН4||Properties of CFC|
|T, °С||Х, %||t, h||G, g/gcat.||SBET, m2/g||Vpore, сm3/g||d002, nm|
2: 85Fe5Ni-Al2O3 (T=625°C),
3: 85Fe5Сo-Al2O3 (T=625°C),
4: 75Co-Al2O3 (T=500°C),
5: 90Ni-Al2O3 (T=550°C).
TEM (a) and HRTEM (b) pictures of the CFC-I.
TEM (a) and HRTEM (b) pictures of the CFC-III.
TEM (a) and HRTEM (b) pictures of the CFC (Fe).
The genesis of catalyst particles and catalytic filomentous carbon are studied by methods: XRD, TEM, SEM, EXAF, Mossbauer, ESDR.