Author(s):
Tavares, M. T. 
; Alstrup, I. ; Bernardo, C. A. ; Rostrup-Nielsen, J. R.
Date: 1996
Persistent ID: http://hdl.handle.net/1822/3698
Origin: RepositóriUM - Universidade do Minho
Document details
Carbon formation and CO methanation on silica-supported nickel and nickel–coppe...
Description
The steady-state rates of simultaneous carbon formation and methanation on silica-supported nickel and nickel-copper catalysts in CO + H 2 gas mixtures have been measured in the partial pressure range 10-30 kPa and the temperature range 583-873 K. The steady-state kinetic results for carbon formation can be explained by a model previously used for carbon formation in pure CO gas, but modified to take into account the influence of hydrogen. Comparisons between the results for Ni/SiO 2 , Ni 0.99 Cu 0.01 /SiO 2 , Ni 0.9 Cu 0.1 /SiO 2 , and Ni 0.75 Cu 0.25 /SiO 2 show that the specific rate of carbon formation is increased when 1 at.% of Cu is added to a nickel catalyst, but that the rate decreases when the Cu content is increased to 10 at.%, and that no carbon formation is seen for the Ni 0.75 Cu 0.25 /SiO 2 catalyst. The addition of a small amount of Cu, on the other hand, decreases the methanation rate while at higher Cu contents the rate goes up again and a maximum is observed at about 7 at.% Cu. Thus a simple ensemble model cannot explain the influence of copper on the rate of carbon formation or methanation. Comparison of carbon formation and methanation rates for the Ni/SiO 2 and the Ni 0.99 Cu 0.01 /SiO 2 catalysts indicates that the two reactions have different rate-controlling steps and that the carbon formation influences the methanation rate mainly through poisoning of the catalysts.
The steady-state rates of simultaneous carbon formation and methanation on silica-supported nickel and nickel-copper catalysts in CO + H 2 gas mixtures have been measured in the partial pressure range 10-30 kPa and the temperature range 583-873 K. The steady-state kinetic results for carbon formation can be explained by a model previously used for carbon formation in pure CO gas, but modified to take into account the influence of hydrogen. Comparisons between the results for Ni/SiO 2 , Ni 0.99 Cu 0.01 /SiO 2 , Ni 0.9 Cu 0.1 /SiO 2 , and Ni 0.75 Cu 0.25 /SiO 2 show that the specific rate of carbon formation is increased when 1 at.% of Cu is added to a nickel catalyst, but that the rate decreases when the Cu content is increased to 10 at.%, and that no carbon formation is seen for the Ni 0.75 Cu 0.25 /SiO 2 catalyst. The addition of a small amount of Cu, on the other hand, decreases the methanation rate while at higher Cu contents the rate goes up again and a maximum is observed at about 7 at.% Cu. Thus a simple ensemble model cannot explain the influence of copper on the rate of carbon formation or methanation. Comparison of carbon formation and methanation rates for the Ni/SiO 2 and the Ni 0.99 Cu 0.01 /SiO 2 catalysts indicates that the two reactions have different rate-controlling steps and that the carbon formation influences the methanation rate mainly through poisoning of the catalysts.
Document Type
Article
Language English
Language English
| Financiadores do RCAAP | |||||||
|
|
|
|
|
|
||