CO _x ‐free catalytic decomposition of methane over solution combustion synthesis derived catalyst: Synthesis of hydrogen and carbon nanofibers

Abstract

Summary The catalyst for decomposition of methane to carbon nanofibers and hydrogen was prepared using the solution combustion technique. Dynamics of change of temperature of solution (gel) during the passing of redox reaction of synthesis of catalyst was found experimentally. Testing of catalyst was carried out in a flow through installation. Catalyst with high content of active component 90Ni‐10Al2O3 (wt%) was tested in a reaction of methane decomposition in a temperature range 535°С to 675°С and pressures 1 to 5 atm. The samples of carbon nanofibers were investigated by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and X‐ray diffraction. The optimal parameters of catalytic reaction (550°С, 3 atm) providing the high specific yield of hydrogen (287.7 mol/g) were established. The increase of pressure above 1 atm led to prolonged operation of the catalyst. The negative role of temperature rise on the yield of CNFs was found.

Production of Hydrogen and Solid Carbon by Methane Decomposition under Pressurized Conditions Using a Rotary Reactor and Purification of Yielded Hydrogen by Hydrogen Separation Membrane

“…When the ratio of (catalyst weight)/pressure was kept constant (▲), the crystallite size was slightly larger than that when the catalyst weight was kept constant at 15 g (●): the higher the pressure, the larger the crystallite size of α-Fe was. In the case of Ni, also, it has been reported that the metallic crystallite size tends to increase under pressure, although the correlation is weak …”

“…In the case of Ni, also, it has been reported that the metallic crystallite size tends to increase under pressure, although the correlation is weak. 6 The sizes of α-Fe crystallite after 42 h of reaction with catalyst weight = 15 g, CH 4 flow rate = 300 mL/min, and pressure = 1 atm and after 14 h of reaction with 45 g of catalyst weight, 900 mL/min CH 4 flow rate, and 3 atm pressure are also shown in Figure 8. The size of α-Fe crystallite was found to decrease with time, which is also consistent with Wang's report.…”

“…It is well known that nickel- and cobalt-based catalysts are highly effective for the methane decomposition reaction. − These catalysts show high activity even at low temperatures, but the methane conversion is governed by equilibrium; therefore, methane conversion is inevitably low at low temperatures.…”

“…There are several reported cases of methane decomposition reactions under pressurized conditions. Bannov reported the reaction using the Ni–Al 2 O 3 catalyst at conditions of 535–675 °C and 1–5 atm . Platte reported reactions with an iron ore and 950 °C and 9 bar .…”

“…Bannov reported the reaction using the Ni−Al 2 O 3 catalyst at conditions of 535−675 °C and 1−5 atm. 6 Platte reported reactions with an iron ore 26 and 950 °C and 9 bar. 46 Zhou reported the reactions using an iron ore as a catalyst at 850 °C and 5 bar.…”