Hydrogen Production by Catalytic Decomposition of Methane

Abstract

Traditionally, hydrogen is produced by reforming or partial oxidation of methane to produce synthesis gas, followed by the water-gas shift reaction to convert CO to CO 2 and produce more hydrogen, followed in turn by a purification or separation procedure. This paper presents results for the catalytic decomposition of undiluted methane into hydrogen and carbon using nanoscale, binary, Fe-M (M ) Pd, Mo, or Ni) catalysts supported on alumina. All of the supported Fe-M binary catalysts reduced methane decomposition temperature by 400-500 °C relative to noncatalytic thermal decomposition and exhibited significantly higher activity than Fe or any of the secondary metals (Pd, Mo, and Ni) supported on alumina alone. At reaction temperatures of approximately 700-800 °C and space velocities of 600 mL g -1 h -1 , the product stream was comprised of over 80 volume % of hydrogen, with the balance being unconverted methane. No CO, CO 2 , or C 2 and higher hydrocarbons were observed in the product gas. High-resolution SEM and TEM characterization indicated that almost all carbon produced in the temperature range of 700-800 °C is in the form of potentially useful multiwalled nanotubes. At higher temperatures (>900 °C), hydrogen production decreases and carbon is deposited on the catalyst in the form of amorphous carbon, carbon flakes, and carbon fibers. In the noncatalytic thermal decomposition mode, at temperatures above 900 °C, graphitic carbon film is deposited everywhere in the reactor. Thus, the morphology of the carbon produced may be the controlling parameter in catalytic decomposition of methane. The efficient removal of the carbon from the catalyst surface in the form of nanotubes may be the key factor influencing catalyst performance.

Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for single-walled carbon nanotube growth

“…chemical poisoning or coating with carbon), thermal sintering (e.g. caused by highly exothermic reactions on the clusters surface 13,14,24 with insufficient heat transfer 25,26 ) and solid-state reactions (nucleation of inactive phases in the cluster 22,23,25 ).Metal alloy catalysts, such as Fe:Co, Co:Mo and Fe:Mo, improve the growth of CNTs 4,10,20,27,28,29,30,31 , because the presence of more than one metal species can significantly enhance the activity of a catalyst 20,32,33,34 , and can prevent catalyst particle aggregation 20,31,32,33 . In the case of Fe:Mo nanoparticles supported on Al 2 O 3 substrates, the enhanced catalyst activity has been shown to be larger than the linear combination of the individual Fe/Al 2 O 3 and Mo/Al 2 O 3 activities 20,27,28 .…”

“…In the case of Fe:Mo nanoparticles supported on Al 2 O 3 substrates, the enhanced catalyst activity has been shown to be larger than the linear combination of the individual Fe/Al 2 O 3 and Mo/Al 2 O 3 activities 20,27,28 . This is explained in terms of substantial inter-metallic interaction between Mo, Fe and C 20,35,36 which is congruent with previously observed solid-state reactions between these elements.…”

Ethane- and hydrogen-bearing carbonic fluid inclusions in a high-grade metamorphic rock

“…Such occurrence of carbon film have been found sometimes in methane -rich diagenetic fluid inclusions and more scarcely in H 2 O -CH 4 -CO 2 fluid inclusions associated with graphitic -bearing rocks but never in CO 2 -rich fluid inclusions. Experimentally, nanocarbon are produced by thermal decomposition of CH 4 into H 2 in presence of catalysts (see Shah et al, 2001;Homayonifar et al, 2008, and references therein), but this explanation is not relevant to this case study. The small amount of carbon precipitated along the inclusion wall suggests that the fluid oversaturation with respect to "graphite" was small during its precipitation, contrary to the re -equilibration experiments carried out by Pasteris and Chou (1998).…”

Direct Preparation of Hydrogen and Carbon Nanotubes by Microwave Plasma Decomposition of Methane over Fe/Si Activated by Biased Hydrogen Plasma

“…This temperature is higher than that of general chemical engineering processes. Therefore Ni [2][3][4][5][6][7], Fe [8,9] and Co [10] based catalyst has been used to decompose methane at lower temperature. Venugopal et al obtained the methane conversion of 32%, decomposing methane at 600˚C under 30 wt% Ni/SiO 2 [4].…”

“…Suelves et al obtained the methane conversion of 67% and hydrogen concentration of 80% at 700˚C under Ni-based catalyst [6]. Shah et al obtained the hydrogen yield of 80 -90 vol%, decomposing methane at 700˚C -800˚C under Fe-M (M = Pd, Mo and Ni) catalyst supported on alumina [10]. In these studies, although the hydrogen concentration is high (80% -90%), the methane conversion is not so high.…”