Sage Journals: Discover world-class research

Abstract

During catalytic cracking of methane reaction, different carbon nanostructures can be formed. This paper shows the results of a characteristic nanostructured carbon deposit obtained during cracking of methane reaction over nanocrystalline iron catalysts with or without cobalt addition. The properties of the carbon deposit were determined by X-ray diffraction, scanning electron microscope with energy dispersive spectrometer equipment, thermogravimetry-differential thermal analysis coupled with mass spectrometry, time-of-flight secondary ion mass spectrometry analysis and surface area analysis (Brunauer-Emmett-Teller isotherm [BET]). Significant differences in the morphology and properties of the obtained carbon were found. The mechanism of the formation of carbon nanostructures for both iron catalysts is proposed.

Keywords

Carbon deposit carbon nanofibres catalysis cracking of methane iron catalysts

Introduction

The formation of carbon is well known and takes place in every process where hydrocarbons undergo thermal decomposition (Ahmeda et al., 2009; Kim et al., 2015; Leroi et al., 2005; Shih et al., 2004; Solovyev et al., 2009; Vieira et al., 2004; Wang et al., 2005).

In the case of catalytic processes, carbon deposit may confine the activity of the catalyst in different ways, for example, by strong adsorption on the active phase surface, by physically blocking the reactor or by clogging the pores (Amin et al., 2011). Carbon adhering to the surface of the catalyst can produce different forms, for example, filamentous, graphite or amorphous carbon. Dultsev et al., (2014) investigated the properties of amorphous carbon obtained in the supersonic gas jet. Podder et al., (2005) also investigated the properties of amorphous carbon but doped with boron and obtained by the plasma-enhanced chemical vapour deposition method. In both works, methane was the source of carbon. Land et al., (1992) investigated the growth and nature of a graphite layer during decomposition of ethylene. However, it seems that carbon filaments (nanotubes and nanofibres) (Anoshkin et al., 2014; Mizutani et al., 2012; Takenaka et al., 2004a; Teng et al., 2014; Willems et al., 2000; Zhang and Zhang, 2013; Zou et al., 2006) are the most often described and investigated group. The formation of carbon nanotubes/nanofibres on the catalyst’s surface is a desirable form. Due to their exceptional properties, they have many potential applications in technology, for example, as polymer reinforcements (Fan et al., 2013; Opelt et al., 2015), composites (Tofighy and Mohammadi, 2015; Wang et al., 2015), materials for hydrogen storage (Lin et al., 2009; Muthu et al., 2016), electronics (Peng et al., 2014) and catalysis (Ali et al., 2015; Serp et al., 2003; Shanahan et al., 2011).

The method which is most frequently used for the production of carbon nanotubes/nanofibres is catalytic chemical vapour deposition. The catalysts traditionally used in this process are Fe, Co or Ni (Colomer et al., 2000; Gulino et al., 2005; Kathyayini et al., 2004; Louis et al., 2005; Prasek et al., 2011; Tran et al., 2007). The diameter of the fibres depends on the dimensions of the metal nanoparticle used as a catalyst, while the shape, symmetry, dimensions, growth rate and crystallinity of the materials are influenced by the selection of the catalyst, carbon source, temperature and time of the reaction.

The aim of our work was to examine the forms of carbon deposit obtained in the cracking of methane reaction with the use of nanocrystalline iron catalysts with or without cobalt addition. We tested a typical nanocrystalline iron catalyst commonly used in ammonia synthesis (Arabczyk and Narkiewicz, 2002; Kowalczyk et al., 1997; Lendzion-Bieluń and Arabczyk, 2013). Our intention was the create iron nanoparticles coated with a carbon layer that consists of nanotubes or nanofibres. The magnetic properties of these encapsulated nanoparticles give an opportunity to apply them in different branches of technology such as catalysis and photocatalysis, gas sensors and biosensors, recovery and treatment of waste water and others (Gu et al., 2013; Jong-Min et al., 2010; Sancan et al., 2016; Sunny et al., 2010; Yao et al., 2016). The important application target of these structures is medicine where nanoparticles of ferromagnetic metals encapsulated by neutral materials can facilitate drug delivery (Harutyunyan et al., 2002; Masotti and Caporali, 2013; Wang et al., 2014). Therefore, it is extremely important to extend and share the knowledge of this topic.

Many efforts have been made to obtain this kind of materials with a simple synthetic procedure and easy processing for subsequent application. In our work, we decided to use iron-fused catalysts for the decomposition of methane to receive iron core nanoparticles with a protecting carbon shell. Iron-fused catalysts are commonly used in ammonia synthesis. This type of catalysts is rather rarely used for the decomposition of methane. Thus, using a catalyst for ammonia synthesis gives opportunities for their new applications. However, in literature, there are examples of investigations of the methane decomposition over iron-fused catalysts (Arabczyk et al., 2004).

This publication is the continuation of our previous work (Maj et al., 2015), where we described the way of direct methane decomposition with fused iron catalysts to receive hydrogen and the catalysts characteristics. We tested the process of methane decomposition in the temperature range of 200–700℃. Higher temperatures cause strong sintering of the catalyst and its deactivation. The best activity was achieved at 700℃; therefore, we use this temperature in our investigations.

Iron catalysts were a proper choice to be considered in the cracking of methane reaction. They have significant resistance to high temperatures and they are relatively inexpensive. However, they show rather low activity. In order to improve their activity, metals or metal oxides are used as various additives. Cobalt has intermediate properties (high activity in the cracking of methane reaction and considerable resistance to high temperatures), so it seems a good addition, improving the iron catalyst’s activity in this type of reaction (Abbas et al., 2010; Li et al., 2011).

The properties of the carbon deposit were determined by different physicochemical methods (X-ray diffraction, XRD; scanning electron microscope with energy dispersive spectrometer, SEM/EDS; thermogravimetry-differential thermal analysis coupled with mass spectrometry, TG-DTA-MS; time-of-flight secondary ion mass spectrometry analysis, ToF-SIMS and BET).

Experimental

Catalysts

Designation of samples:

S1 - nanocrystalline iron catalysts without cobalt addition;

S2 - nanocrystalline iron catalysts with cobalt addition;

SC1 - nanocrystalline iron catalysts without cobalt addition and with carbon deposit;

SC2 - nanocrystalline iron catalysts with cobalt addition and carbon deposit.

The nanocrystalline iron catalysts were obtained by the method which includes a fusion of magnetite or wustite with small amounts of aluminum, calcium, potassium and/or cobalt oxides. These oxides were precursors for the catalyst. The process of melting was carried out in a laboratory plant, which consists of a feed block, a basin and water-cooled steel electrodes. The basin and steel electrodes created a kind of an electric furnace. The process of fusion was based on the conduction of electrical current with high current intensity through the bed of catalyst precursors. The lava after the fusion was cooled to room temperature, crushed and sieved. The grains between 0.2 and 0.6 mm were taken for further investigations. The detailed description of the catalyst preparation is presented in the works (Arabczyk et al., 1996, 2004). The presence of aluminum and calcium oxides prevents the sintering of the catalyst at high temperatures (Ahmeda et al., 2009; Leroi et al., 2005). Using the inductively coupled plasma, optical emission spectrometry method, the composition of the catalysts was determined.

The S1 catalyst contains iron as wustite as well as the following oxides:

3.88 %mas. Al₂O₃;

1.96 %mas. CaO;

0,41 %mas. K₂O;

whereas the S2 catalyst contains iron as magnetite and also the following oxides:

3.35 %mas. Al₂O₃;

1.10 %mas. CaO;

0.10 %mas. K₂O;

21.24 %mas. Co₃O₄.

Cracking of methane reaction

Cracking of methane reaction was carried out in a quartz reactor with a diameter ϕ = 6 mm, filled with 0.20 g of a catalyst, using a flow rate of pure CH₄ (Air Products, 99.99% purity) of 20 ml/min⁻¹ at a reaction temperature of 700℃. The activity of catalysts in the process of methane decomposition was tested in the temperature range of 200–700℃. The catalysts achieved the best activity at 700℃, and therefore, we decided to choose this temperature in our investigation. The reactor was situated in an electric furnace controlled by a temperature controller. Prior to the cracking of methane reaction, all catalysts were subjected to a reduction pre-treatment with a flow rate of pure hydrogen of 20 ml/min⁻¹ for 10 h at 500℃ as recommended in the literature (Arabczyk et al., 2004).

The process of methane decomposition was conducted as long as the presence of hydrogen was detectable behind the reactor. The carbon species and hydrogen in the gas phase were formed according to the following reaction:

{CH}_{4} \to C + 2 H_{2}

Due to the methane decomposition over the Fe-based catalyst, carbon nanocomposites species were formed on the surface of catalysts which were labelled as SC1 and SC2, respectively.

Characterization methods of carbon deposit

X-ray diffraction

X-ray diffraction patterns were collected using a PANalytical X’Pert Pro MPD diffractometer in Bragg-Brentano reflecting geometry. Copper CuK_α radiation from a sealed tube was utilized. The generator was operated at 40 kV and 30 mA. Data were collected in the range 3–80° 2θ with a step 0.0167° and exposition per one step of 19, 6 s. A nickel filter on the receiving side was used to eliminate CuK_β radiation. Soller slits, both primary and secondary, reduced the asymmetry of the peaks at low diffraction angles.

Scanning electron microscope with EDS equipment

The morphological appearance of the deposited carbon was studied with a SEM Hitachi S-4700 (Japan) equipped with an EDS device Thermo Noran (USA). The SEM images were obtained with the use of a high vacuum mode and accelerating voltage of 25 keV.

Thermogravimetry-differential thermal analysis coupled with mass spectrometry

Thermal analysis data (SETSYS 16/18, Setaram (France) and mass spectrometer ThermoStar, Balzers (Germany)) were used for temperature-programmed oxidation of the carbon deposit and SC1 and SC2 catalysts in the air atmosphere. The measurements were taken from room temperature to 900℃ in the flowing air, applying a sample weight of about 50 mg in a linear heating rate of 10℃/min⁻¹.

Surface areas analysis (BET)

The specific surface area and porosity of the catalysts and their supports were determined with surface area and porosity analyzer micrometrics Accelerated Surface Area and Porosimetry (ASAP) 2020. Samples were prepared at 350℃, followed by low temperature nitrogen adsorption–desorption measurements carried out with the use of BET and liquid N₂ method.

Time-of-flight secondary ion mass spectrometry analysis

ToF-SIMS mass spectra of ions were obtained on the secondary ion mass spectrometer TOF-SIMS IV (ION-TOF GmbH, Münster, Germany) equipped with a high mass resolution ToF analyzer of a reflectron type. ${Bi}_{3}^{+}$ primary ion gun was used during the analysis. Primary ions mass spectra were recorded from 100 × 100 µm for the tablet area of the sample surface. During the measurement, the analysed area was irradiated with the pulses of 25 keV ${Bi}_{3}^{+}$ ions at 10 kHz repetition rate and an average ion current 0.5 pA.

Results and discussion

Thermogravimetry-differential thermal analysis

The resistance of carbon deposit to thermal oxidation was investigated by TG analysis. The results are given in Figures 1 and 2. From these figures, it is found that in both cases, the carbon deposit is resistant to thermal oxidation up to at least 450℃. At this temperature, a characteristic weight loss due to the carbon oxidation is observed. As shown in the TG curve, only a single clear step was observed for both samples, whereas the DTG curve (derivative of TG results) showed that the process consisted of at least four steps. The first shows a negative peak (decrease in the mass of the sample) at 80℃, which corresponds to the removal of moisture from samples; the second around 400℃ shows a positive peak and it is probably connected with the oxidation of cobalt or/and iron. It is worth noticing, that in the case of SC2 sample (Figure 2), this peak is clearly higher. These results show that both catalysts are probably not completely encapsulated by carbon. The third negative broad peak is observed at 600℃ and arises as a result of carbon oxidation. These peaks arise at 450℃. It means that oxidation of carbon deposit started just at that temperature. In the case of SC1 samples, four negative peaks can be observed at 700℃. This peak probably arises as a consequence of irons carbide oxidation. These compounds can be formed during the methane decomposition over the iron catalyst (Arabczyk et al., 2004). To summarize, the results obtained in this work reveal that the deposited carbon materials are fully oxidized in the temperature range of 450 to 700℃ for the SC1 sample and the range from 450 to 610℃ for the SC2 sample. The summary mass loss of the SC1 sample was 89.8%, whereas the SC2 sample lost only 65.1% of its mass. The obtained results also show that both catalysts are probably not completely encapsulated by carbon. Nevertheless, it should be stressed that over the both samples, carbon deposit is rather stable for thermal treatment in air up to the temperature of 450℃ (Crumpton et al., 1996).

Figure 1.

Thermal analysis of carbon deposit over nanocrystalline iron catalyst without cobalt addition (SC1).

Figure 2.

Thermal analysis of carbon deposit over nanocrystalline iron catalyst with cobalt addition (SC2).

X-ray diffraction

The XRD tests were carried out for both catalyst samples of carbon deposit. Figure 3 shows a small pattern derived from graphite in the SC1 sample and a very high pattern in the SC2 sample. This indicates that the presence of cobalt initiates the formation of the graphite structure. For all the XRD patterns shown in Figure 3, the diffraction lines were found only from the graphite structure and metals from the catalysts. It indicates the absence of amorphous carbon in the samples. Also, the main graphitic carbon phase at 2θ = 26° in the SC2 sample is dominant compared to the other peaks that are attributed to the metallic phases. A similar effect is obtained in works (Awadallah et al., 2014), where the reflections at ca. 2θ = 26° and 44° are attributed to the graphitic carbon that appears in all used Co-based catalysts. The authors believe that this proves acquisition of carbon nanotubes.

Figure 3.

XRD-patterns of carbon deposit over nancrystalline iron catalyst without cobalt (SC1) and with cobalt addition (SC2). XRD: X-ray diffraction.

The average size of crystalline (Table 1) was calculated from the Scherrer’s equation (1):

d_{hkl} = \frac{k \cdot λ}{(B - b) \cdot \cos θ}

(1)

where:

d_hkl - average crystallite size in (nm),

k - constant dependent on the shape of crystallite,

λ - wavelength of X-rays dependent on the type of lamp (nm),

B - extension reflex two theta scale (deg)

b - instrument amendment given on a scale of two theta (deg),

θ - the location of reflex theta scale (deg).

Table 1.

The overage size of crystallite for S1, S2, SC1 and SC2 samples.

Sample	Particle size d (nm)
Sample	Carbon	Metals
S1	–	37
S2	–	28
SC1	13	39
SC2	12	36

Surface areas analysis (BET)

The specific textural properties of the carbon deposit obtained over the iron catalyst are shown in Table 2. The specific surface area as well as pore volume for the SC2 sample is almost twice as big as for SC1, which results from the presence of carbon nanofibres in the SC2 sample.

Table 2.

Textural properties of carbon deposit obtained over an iron catalyst without the addition of cobalt (SC1) and with cobalt (SC2).

Sample	Specific surface area (m²/g⁻¹)	The average size of pores (nm)
SC1	25.3	6.04
SC2	44.6	5.84

Ermakova et al., (2001a) tested textural and structural characteristics of filament carbons synthesized using different carrier iron catalysts and obtained similar results of the specific surface area (20–79 m²/g⁻¹) and the pore volume (0.13–0.27 cm³/g⁻¹) but 2–10 times larger size of pores.

The BET isotherms of SC1 and SC2 samples are shown in Figure 4. The shapes of isotherms suggest a type III adsorption isotherm according to the IUPAC classification (Sing et al., 1985). This type of isotherm is present in macroporus adsorbents with weak adsorbate–adsorbent interactions. It is worth noticing that no clear hysteresis is observed. The hysteresis of adsorption/desorption isotherms indicates the presence of macropores in the structure of obtained nanocarbon composites.

Figure 4.

Isotherm of N2 adsorption/desorption for SC1 (a) sample and SC2 (b).

Time-of-flight secondary ion mass spectrometry analysis

Figure 5 shows the graphs of intensity of selected ions received by the ToF-SIMS method for samples of iron–carbon composites (SC1, SC2) and fresh catalysts as a pattern (S1, S2). Almost in every case, a clear difference between intensities of ions in a fresh sample and iron–carbon composite samples is observed. It indicates that the particles of the iron catalyst are totally covered by carbon. This is called the phenomenon of encapsulation of metal particles by carbon, which leads to the creation of iron–carbon composites. The fact that the quantities of basic ions are bigger in the SC2 than SC1 sample is worth noting. This, on the other hand, indicates the basicity of the sample’s surface.

Figure 5.

Graphs of intensity (counts) of selected ions received from the ToF-SIMS method for S1, S2, SC1, SC2 samples. ToF-SIMS: time-of-flight secondary ion mass spectrometry analysis.

Scanning electron microscope with EDS equipment

Both catalyst samples after cracking of methane reaction coated with carbon deposit were examined with SEM/EDS.

The carbon deposit for the S1 catalyst takes the form of spherical carbon nanostructures (Figure 6(a)). The situation is different in the case of the S2 catalyst (Figure 6(b)). The images show that the surface is completely covered with carbon but it is formed in carbon nanofibres.

Figure 6.

Representative SEM/EDS images of carbon deposited after cracking of methane reaction using a nanocrystalline iron catalyst without cobalt (a) and with cobalt (b). SEM/EDS: scanning electron microscope with energy dispersive spectrometer.

Both the type of catalyst and reaction conditions influence the morphology of the obtained nanofibres (Li and Li, 2011). The effect of temperature on the morphology of the carbon nanofibres was investigated by Snoeck et al., (1997). Based on their work, it can be concluded that at a low temperature full structures of carbon nanofibres are formed and at a high temperature the formation of hollow structures is dominant (Li and Li, 2011; Snoeck et al., 1997). Also, Takenaka et al., (2004b) described the process of obtaining hollow carbon nanofibres with the use of a cobalt catalyst at 600–700℃. The application of a higher temperature causes the production of spiral and bamboo-shaped carbon nanofibres.

Carbon nanotubes/nanofibres were first observed by Baker et al., (1972, 1973) in the 1970s. Two types of growth mechanism, tip- or base-growth model, were proposed in 1989 by Beker (1989). Both cases depend on the interaction between the metal and substrate materials. In the tip-growth model, where the interactions are weak, the metal particle is pushed at the top by carbon that diffuses down. The carbon nanotube/nanofibre is grown as long as the metal is free for hydrocarbon decomposition. The growth is stopped when the metal particle present at the top of the nanotube/nanofibre is completely covered by carbon. In the base-growth model, carbon forms a hemispherical dome on the surface of the metal particle. The catalyst–substrate interaction is too strong to push the metal particle at the top, so it extends up in the form of a graphic cylinder.

During the SEM/EDS tests, in several places of nanofibre (including at its tip), the spectrum of metal was formed. We did not observe more metal at the tip of the nanofibre. This allowed us to conclude that we are dealing with the base-growth model.

In the following part of this paper, we propose the mechanisms of nanofibres growth to explain the differences in the morphology of the obtained forms of carbon deposit.

Figures 7 and 8 show the mechanisms of carbon deposit formation during methane decomposition over an iron catalyst without cobalt addition (Figure 7) and with cobalt addition (Figure 8).

Figure 7.

Schema of carbon deposit formation for catalyst without cobalt addition.

Figure 8.

Schema of carbon deposit formation for catalyst with cobalt addition.

Both iron and cobalt form carbide phases. Iron forms five different carbide phases, which have all been widely examined, while CoxC has only two stable phases, Co₃C and Co₂C (Harris et al., 2010; Huba, 2014). Sówka et al., (2008) published that cobalt and iron with an acrylamide complex exhibit a different structure in the pyrolysis process at 600℃, which was confirmed by the X-ray phase analysis, Mössbauer spectroscopy and TEM observations. The sample polymer with cobalt matched the lines of metallic cobalt and the broad spectra suggested a nanocrystalline structure. A different situation was observed for the sample with iron and polymer where iron carbide was found. The TEM studies for the pyrolysed cobalt with polymer showed individual particles having the size of 12 nm but iron carbides were agglomerated and their sizes ranged from 10 up to 80 nm.

According to the literature (Ermakova et al., 2001b), Fe₃C acts as an active phase in the formation of carbon nanotubes/nanofibres. Emmenegger et al. (2003) described that the graphite layers could also encapsulate the Fe₃C particles before they reach the critical dimension and they are inactivated as possible active sites. We know too that iron creates carbides more easily and at a lower temperature (Sówka et al., 2008).

The nature/properties of the catalyst have a very big impact on the methane decomposition process. With absence of any catalyst, hydrogen and soot may be obtained from methane by pyrolysis in the temperature range 1000–1200℃. Consequently, several studies have been conducted in order to avoid such high temperatures, soot in the reactor and to improve efficiency of the reaction. The introduction of a selected catalyst to the processes causes the formation of various carbonaceous species (Fau et al., 2014).

Due to the above literature data and our observations, we suggested the following mechanism of carbon formation on S1 and S2 catalysts.

In our case, we do not observe forms of carbon nanotubes/nanofibres on the surface of an iron catalyst without cobalt addition. Spherical carbon nanostructure forms are observed on the surface of the catalyst as a result of encapsulation of the Fe₃C particles. A similar situation can also be observed on the iron catalyst with cobalt addition. However, in this case, cobalt nanoparticle crystallites are present on the catalyst’s surface. They form active sites for the carbon nanotubes/nanofibres formation and enable their growth, which is shown in Figure 8.

Conclusion

We have presented the chemical and physical properties of the carbon nanofibres formed by the nanocrystalline iron catalyst with or without cobalt addition by XRD, SEM/EDS, BET, ToF-SIMS and TG-DTA-MS methods. The mechanisms of nanofibres growth explain the differences in the morphology of the obtained forms of the carbon deposit.

The structural characterization shows that carbon forms have various structures with a different specific surface area and a similar size of pores.

The results show that particle sizes are similar but the pore size is clearly larger for SC2 samples. Moreover, SEM pictures show that forms of carbon deposited on each catalyst have different structures. The carbon deposit for the S1 catalyst takes only spherical carbon nanostructure forms. On the S2 catalyst, carbon forms nanofibres which probably together with a larger pore size are responsible for a bigger surface area of the SC2 sample.

The ToF-SIMS made it possible to observe the fact that the quantities of basic ions are larger in the SC2 than the SC1 sample. This indicates the basicity of the surface of the carbon deposit sample with cobalt addition.

The SEM images clearly indicated the existence of nanostructured filaments in the SC2 sample and spherical nanostructured carbon particles on the SC1 sample. Also, both carbon deposit forms have a crystalline structure, which is confirmed by TG-DTA-MS and XRD methods. No amorphous carbon was observed.

Footnotes

Acknowledgements

Special acknowledgement to Prof. W. Arabczyk (ZUT Szczecin, Poland) for the preparation of catalysts.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Research funded by the Young Scientists Fund at the Faculty of Chemistry, Lodz University of Technology, Grant W-3/FMN/9G/2015.

References

Abbas

Wan Daud

WMA

(2010) Hydrogen production by methane decomposition: A review. International Journal of Hydrogen Energy 35: 1160–1190.

Ahmeda

Aitani

Rahman

et al. (2009) Review: Decomposition of hydrocarbons to hydrogen and carbon. Applied Catalysis A 359: 1–24.

Ali

Ahmed

Sohail

et al. (2015) Co@Pt core–shell nanoparticles supported on carbon nanotubes as promising catalyst for methanol electro-oxidation. Journal of Industrial and Engineering Chemistry 28: 344–350.

Amin

Croiset

Epling

(2011) Review of methane catalytic cracking for hydrogen production. International Journal of Hydrogen Energy 36: 2904–2935.

Anoshkin

Nasibulin

Tian

et al. (2014) Hybrid carbon source for single-walled carbon nanotube synthesis by aerosol CVD method. Carbon 78: 130–136.

Arabczyk

Narkiewicz

(2002) A new method for in situ determination of number of active sites in iron catalysts for ammonia synthesis and decomposition. Applied Surface Science 196: 423–428.

Arabczyk

Koniecki

Narkiewicz

et al. (2004) Kinetics of the iron carbide formation in the reaction of methane with nanocrystalline iron catalyst. Applied Catalysis A: General 266: 135–145.

Arabczyk W, Ziebro J, Kałucki K, et al. (1996) Laboratory scale plant for continuous fusing of iron catalysts. Chemik 1: 3–7.

Awadallah

Aboul-Enein

Aboul-Gheit

(2014) Impact of group VI metals addition to Co/MgO catalyst for non-oxidative decomposition of methane into COx-free hydrogen and carbon nanotubes. Fuel 129: 27–36.

10.

Baker

RTK

(1989) Catalytic growth of carbon filaments. Carbon 27(3): 315–323.

11.

Baker

RTK

Barber

Harris

et al. (1972) Nucleation and growth of carbon deposits from the nickel catalyzed decomposition of acetylene. Journal of Catalysis 26: 51–62.

12.

Baker

RTK

Harris

Thomas

et al. (1973) Formation of filamentous carbon from cobalt and chromium catalyzed decomposition of acetylene. Journal of Catalysis 30: 86–95.

13.

Colomer

Stephanb

Lefrant

et al. (2000) Large-scale synthesis of single-wall carbon nanotubes by catalytic chemical vapor deposition (CCVD) method. Chemical Physics Letters 317: 83–89.

14.

Crumpton

Laitinen

Smieja

et al. (1996) Thermal analysis of carbon allotropes: An experiment for advanced undergraduates. Journal of Chemical Education 73: 590–591.

15.

Dultsev

Kolosovsky

Nastaushev

et al. (2014) Investigation of the properties of amorphous carbon films obtained in a supersonic gas jet. Surface Coated Technology 246: 46–51.

16.

Emmeneggera

Bonardb

Maurona

et al. (2003) Synthesis of carbon nanotubes over Fe catalyst on aluminium and suggested growth mechanism. Carbon 41: 539–547.

17.

Ermakova

Ermakov

Chuvilin

et al. (2001) Decomposition of methane over iron catalysts at the range of moderate temperatures: The influence of structure of the catalytic systems and the reaction conditions on the yield of carbon and morphology of carbon filaments. Journal of Catalysis 201: 183–197.

18.

Fan

Wang

Shi

et al. (2013) Kevlar nanofiber-functionalized multiwalled carbon nanotubes for polymer reinforcement. Materials Chemistry and Physics 141: 861–868.

19.

Fau G, Gascoin N and Steelant J (2014) Hydrocarbon pyrolysis with a methane focus: A review on the catalytic e_ect and the coke production. Journal of Analytical and Applied Pyrolysis Elsevier: 2014.

20.

Ding

Sameer

et al. (2013) Microwave assisted formation of magnetic core-shell carbon nanostructure. ECS Solid State Letters 2(12): 2162–8742.

21.

Gulino

Vieira

Amadou

et al. (2005) C₂H₆ as an active carbon source for a large scale synthesis of carbon nanotubes by chemical vapour deposition. Applied Catalysis A 279: 89–97.

22.

Harris

Chen

Yang

et al. (2010) High coercivity cobalt carbide nanoparticles processed via polyol reaction: a new permanent magnet material. Journal of Physics D-Applied Physics 43: 7.

23.

Harutyunyan

Pradhan

Sumanasekera

et al. (2002) Carbon nanotubes for medical application. European Cells and Materials 3(2): 84–87.

24.

Huba

(2014) Synthesis and Characterization of Cobalt Carbide Based Nanomaterials. PhD Thesis, Virginia Commonwealth University, USA.

25.

Jong-Min

Sang_Beom

Jy-Yeon

et al. (2010) TiO₂@carbon core–shell nanostructure supports for platinum and their use for methanol electrooxidation. Carbon 48(8): 2290–2296.

26.

Kathyayini

Nagaraju

Fonseca

et al. (2004) Catalytic activity of Fe, Co and Fe/Co supported on Ca and Mg oxides, hydroxides and carbonates in the synthesis of carbon nanotubes. Journal Molecular Catalysis A 223: 129–136.

27.

Kim

Hyeon

et al. (2015) Development of PIBSI type dispersants for carbon deposit from thermal oxidative decomposition of Jet A-1. Fuel 158: 91–97.

28.

Kowalczyk

Sentek

Jodzis

et al. (1997) Effect of potassium on the kinetics of ammonia synthesis and decomposition over fused iron catalyst at atmospheric pressure. Journal of Catalysis 169(15): 407–414.

29.

Land

Michely

Behm

et al. (1992) STM investigation of single layer graphite structures produced on Pt(111) by hydrocarbon decomposition. Surface Science 264: 261–270.

30.

Lendzion-Bieluń

Arabczyk

(2013) Fused Fe-Co catalysts for hydrogen production by means of the ammonia decomposition reaction. Catalysis Today 212: 215–219.

31.

Leroi

Cadete Santos Aires

Goislard de Monsabert

et al. (2005) Nickel antigorite synthesis and carbon tubular nanostructures formation on antigorite based nickel particles by acetylene decomposition. Applied Catalysis A 294: 131–140.

32.

Wang

(2011) Methane decomposition to COx-free hydrogen and nano-carbon material on group 8–10 base metal catalysts: A review. Catalysis Today 162: 1–48.

33.

Lin

Chang

Chen

et al. (2009) Effects of heat treatment on materials characteristics and hydrogen storage capability of multi-wall carbon nanotubes. Diamond Related Materials 18: 553–556.

34.

Louis

Gulino

Vieira

et al. (2005) High yield synthesis of multi-walled carbon nanotubes by catalytic decomposition of ethane over iron supported on alumina catalyst. Catalysis Today 102: 23–28.

35.

Maj

Kocemba

Lendzion-Bieluń

et al. (2015) The effect of cobalt addition on the activity of nanocrystalline ferric catalysts in the cracking of methane reaction. Adsorption, Science and Technology 33: 559–566.

36.

Masotti

Caporali

(2013) Preparation of magnetic carbon nanotubes (Mag-CNTs) for biomedical and biotechnological applications. International Journal of Molecular Science 14(12): 24619–24642.

37.

Mizutani

Fukuoka

Naritsuka

et al. (2012) Single-walled carbon nanotube synthesis on SiO₂/Si substrates at very low pressures by the alcohol gas source method using a Pt catalyst. Diamond Related Materials 26: 78–82.

38.

Muthu

Rajashabala

Kannan

(2016) Hexagonal boron nitride (h-BN) nanoparticles decorated multi-walled carbon nanotubes (MWCNT) for hydrogen storage. Renewable Energy 85: 387–394.

39.

Opelt

Becker

Lepienski

et al. (2015) Reinforcement and toughening mechanisms in polymer nanocomposites - carbon nanotubes and aluminum oxide. Composites B 75: 119–126.

40.

Peng

Zhang

Wang

(2014) Carbon nanotube electronics: recent advances. Materials Today 17(9): 433–442.

41.

Podder

Rusop

Soga

et al. (2005) Boron doped amorphous carbon thin films grown by r.f. PECVD under different partial pressure. Diamond Related Materials 14: 1799–1804.

42.

Prasek

Drbohlavova

Chomoucka

et al. (2011) Methods for carbon nanotubes synthesis—review. Journal of Materials Chemistry 21: 15872–15884.

43.

Sancan

Ying-Chih

Lingxia

et al. (2016) Uniform carbon-coated CdS core–shell nanostructures: synthesis, ultrafast charge carrier dynamics, and photoelectrochemical water splitting. Journal of Materials Chemistry A 4: 1078–1086.

44.

Serp

Corrias

Kalck

(2003) Review. Carbon nanotubes and nanofibers in catalysis. Applied Catalysis A 253: 337–358.

45.

Shanahan

Sullivan

McNamara

et al. (2011) Preparation and characterization of a composite of gold nanoparticles and single-walled carbon nanotubes and its potential for heterogeneous catalysis. New Carbon Materials 26(5): 347–355.

46.

Shih

Lin

Shih

(2004) Decomposition of benzene in the RF plasma environment Part I. Formation of gaseous products and carbon depositions. Journal of Hazardous Material 116: 239–248.

47.

Sing

Everett

Haul

et al. (1985) Reporting physisorption data for gas/solid system with special reference to the determination of surface area and porosity. Applied Chemistry 57: 603–619.

48.

Snoeck

Froment

Fowles

(1997) Filamentous carbon formation and gasification: thermodynamics, driving force, nucleation, and steady-state growth. Journal of Catalysis 169: 240–249.

49.

Solovyev

Kuyshinov

Ermacov

et al. (2009) Production of hydrogen and nanofibrous carbon by selective catalytic decomposition of propane. International Journal of Hydrogen Energy 34: 1310–1323.

50.

Sówka

Leonowicz

Pomogailo

JAD

et al. (2008) Structure and properties of magnetic nanoparticles processed by pyrolysis of polymer containing Co and Fe. Reviews on advanced materials science 18: 649–652.

51.

Sunny

Kumar

Yoshida

et al. (2010) Synthesis and properties of highly stable nickel/carbon core/shell nanostructures. Carbon 48(8): 1643–1651.

52.

Takenaka

Ishida

Serizawa

et al. (2004) Formation of carbon nanofibers and carbon nanotubes through methane decomposition over supported cobalt catalysts. Journal of Physical Chemistry B 108: 11464–11472.

53.

Takenaka

Serizawa

Otsuka

(2004) Formation of filamentous carbons over supported Fe catalysts through methane decomposition. Journal Catalysis 222: 520–531.

54.

Teng

Huang

Hsu

et al. (2014) On the use of new oxidized Co–Cr–Pt–O catalysts for vertically-aligned few-walled carbon nanotube forest synthesis in electron cyclotron resonance chemical vapor deposition. Carbon 80: 808–822.

55.

Tofighy

Mohammadi

(2015) Copper ions removal from water using functionalized carbon nanotubes–mullite composite as adsorbent. Materials Research Bulletin 68: 54–59.

56.

Tran

Heinrichs

Colomer

et al. (2007) Carbon nanotubes synthesis by the ethylene chemical catalytic vapour deposition (CCVD) process on Fe, Co, and Fe–Co/Al2O3 sol–gel catalysts. Applied Catalysis A 318: 63–69.

57.

Vieira

Ledoux

Phama-Huua

(2004) Synthesis and characterisation of carbon nanofibres with macroscopic shaping formed by catalytic decomposition of C₂H₆/H₂ over nickel catalyst. Applied Catalysis A 274: 1–8.

58.

Wang

Sun

Pan

et al. (2015) Adsorption of sulfamethoxazole and 17-beta-estradiol by carbon nanotubes/CoFe₂O₄ composites. Chemical Engineering Journal 274: 17–29.

59.

Wang

Zhu

Liao

et al. (2014) Review Article: Carbon nanotubes reinforced composites for biomedical applications. BioMed Research International 2014: 1–14.

60.

Wang

Shah

Huffman

(2005) Simultaneous production of hydrogen and carbon nanostructures by decomposition of propane and cyclohexane over alumina supported binary catalysts. Catalysis Today 99: 359–364.

61.

Willems

Konya

Colomer

et al. (2000) Control of the outer diameter of thin carbon nanotubes synthesized by catalytic decomposition of hydrocarbons. Chemical Physics Letters 317: 71–76.

62.

Yao

Basnet

Sessions

et al. (2016) Fe₂O₃–TiO₂ core–shell nanorod arrays for visible light photocatalytic applications. Catalysis Today 270: 51–58.

63.

Zhang

(2013) Synthesis of carbon nanofibers and nanotubes by chemical vapor deposition using a calcium carbonate catalyst. Materials Letters 92: 342–345.

64.

Zou

Zhang

Dong

et al. (2006) Carbon nanofibers: Synthesis, characterization, and electrochemical properties. Carbon 44: 828–832.

Nanostructured forms of carbon deposit obtained during cracking of methane reaction over nanocrystalline iron catalysts

Abstract

Keywords

Introduction

Experimental

Catalysts

Cracking of methane reaction

Characterization methods of carbon deposit

X-ray diffraction

Scanning electron microscope with EDS equipment

Thermogravimetry-differential thermal analysis coupled with mass spectrometry

Surface areas analysis (BET)

Time-of-flight secondary ion mass spectrometry analysis

Results and discussion

Thermogravimetry-differential thermal analysis

X-ray diffraction

Surface areas analysis (BET)

Time-of-flight secondary ion mass spectrometry analysis

Scanning electron microscope with EDS equipment

Conclusion

Footnotes

Acknowledgements

Declaration of Conflicting Interests

Funding

References