Nickel oxide reduction with methane

Figure 9. Enthalpy, entropy diagram of nickel oxide reduction with methane.

Li et reported a novel method of obtaining nickel oxide particles with controlled crystalline size and fibrous shape, highly dispersed on in situ produced carbon, inhibiting further growth of Ni particles. On the other hand, Ni/CFC (filamentous carbon) catalysts were shown to have sufficient efficiency in low-temperature methane decomposition. Thus, the use of CFG, whose textural properties can be modified by their activation with Hg or COg, opens up the possibility of its application as a support in heterogeneous catalysis. Methane decomposition over Ni-loaded activated carbon (AC) was also investigated. XRD results showed absence of NiO with only Ni metal crystallites formed in the catalyst even if calcined in Ar, which eliminates the inevitable reduction step with other supports. However, the formation of NisC during the process leads to deactivation of the catalysts. Filamentous carbon formation is... 

The difference to the copper process is, that the reduction of nickel oxide with methane is an endothermic process, thus a heat engine could be employed. Figures 9 and 10 show the enthalpy, entropy diagrams of the reactions outlined in equations (8) and (9). (A metallurgist will not favor the reoxidation of nickel since it is very difficult, but equilibrium thernodynamic considerations do allow it.)... 

Nano-grained Ni/ZrOj and Ni/ZrOj-Sm Oj catalysts were prepared from amorphous Ni-Zr and Ni-Zr-Sm alloys by oxidation-reduction treatment. Their catalytic activity for methanation of carbon dioxide was examined as a function of precursor alloy composition and temperature. The addition of samarium is effective in enhancing the activity of the nickel-rich catalysts, but not effective for the zirconium-rich catalysts. The surface area and hydrogen uptake of the nickel-rich catalysts are increased by the samarium addition. In addition, tetragonal zirconia, the formation of which is beneficial to the catalytic activity, is stabilized and formed predominantly by the addition of samarium to the nickel-rich catalysts, although monoclinic zirconia is also formed in the zirconium-rich catalysts. As a consequence, the higher conversion of carbon dioxide is obtained on the Ni-Zr-Sm catalysts with relatively high nickel contents. 

Catalytic activity in the partial oxidation (CPO) of methane of some catalysts containing Ni or Rh/Ni active metals obtained by the calcination and reduction of hydrotalcite-like compounds was investigated. In particular, two hydrotalcite-like compounds subjected to the microwave-hydrothermal method (MWHT) were studied in order to evaluate the role of the synthesis method of the precursors on the catalytic activity and catalyst stability as compared to catalysts prepared by the convention method. The tests carried out at 750°C do not evidence any difference among catalysts. However, when the temperature is reduced to 500°C a better catalytic performance is observed for the microwave-assited catalysts containing nickel, whereas for the bimetallic catalyst the best activity is achieved with the conventional method. 

Akers and Camp(1955) studied the reaction between steam and natural gas within the temperature range of 340-640°C at 1 atmosphere using 3mm diameter pellets of nickel produced by the reduction of nickel oxide supported on kieselguhr. There was little reaction at temperatures less than 600°C and they found first order dependence of the rate of disappearance of methane upon the partial pressure of methane at 640 C. They reported that there was no significant variation of catalyst activity with time. 

The use of finely divided metallic molybdenum, tungsten and other members of this group as catalysts in the reduction of both oxides of carbon at temperatures of 800° to 850° C. has been patented by Schwartz-kopf.81 This process involves the use of an electric furnace lined with platinum, nickel, or platinum-nickel foil. The claim is made that 10 per cent of the reaction gases is transformed into methane in a single passage through the catalyst furnace. The advantage which tire above metals are claimed to possess over others applicable to the reaction is their ability to resist the action of various poisons and particularly suitor compounds. 

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