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Title: CO disproportionation on silica-supported nickel and nickel-copper catalysts

Abstract

The carbon formation/gasification equilibrium on silica-supported nickel and nickel-copper catalysts in CO + CO[sub 2] gas mixtures and the steady state kinetics of carbon formation from CO on the same catalysts were studied in a thermogravimetric flow system. The equilibrium gas composition was found to be the same for the nickel and the nickel-copper catalysts except at the highest copper concentrations ([ge]25 at.%), where larger deviations from graphite equilibrium were found at the lowest temperature (673 K). The deviations at equilibrium of the free energy, [delta]G[sub c], from the value calculated for graphite equilibrium were larger than found previously for carbon formation in CH[sub 4] + H[sub 2] gas mixtures. The steady-state kinetic results have been modelled by using a simple Langmuir model with one type of site. In contrast to some previous studies of carbon formation from CO, the present kinetic results are well described by a model in which the surface reaction of two CO molecules to form carbon and CO[sub 2] is the rate-limiting step at temperatures below about 680 K and CO pressures in the range 15-50 kPa. At higher temperatures and pressures, the experimental rates fall below the model rates, probably due to diffusion limitationsmore » and to the partial coverage of the active surface by graphitic carbon. The conflict whereby a model with CO dissociation as the rate-limiting step gives a better description of the results of some previous kinetic studies of carbon formation from CO is suggested to be resolved by assuming that the latter model is valid when the CO pressure is low or when the gas contains CO[sub 2]. 31 refs., 9 figs., 7 tabs.« less

Authors:
;  [1]; ;  [2]
  1. Universidade do Minho, Braga (Portugal)
  2. Haldor Topsoe Research Labs., Lyngby (Denmark)
Publication Date:
OSTI Identifier:
7275848
Resource Type:
Journal Article
Journal Name:
Journal of Catalysis; (United States)
Additional Journal Information:
Journal Volume: 147:2; Journal ID: ISSN 0021-9517
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 01 COAL, LIGNITE, AND PEAT; 33 ADVANCED PROPULSION SYSTEMS; CARBON; CHEMICAL REACTION YIELD; CARBON DIOXIDE; CARBON MONOXIDE; OXIDATION; REDUCTION; COPPER ALLOYS; CATALYTIC EFFECTS; NICKEL; NICKEL ALLOYS; SILICA; CATALYST SUPPORTS; CHEMICAL REACTION KINETICS; LOW PRESSURE; MATHEMATICAL MODELS; PRESSURE DEPENDENCE; THERMAL GRAVIMETRIC ANALYSIS; ALLOYS; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; CHEMICAL ANALYSIS; CHEMICAL REACTIONS; ELEMENTS; GRAVIMETRIC ANALYSIS; KINETICS; METALS; MINERALS; NONMETALS; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; QUANTITATIVE CHEMICAL ANALYSIS; REACTION KINETICS; SILICON COMPOUNDS; SILICON OXIDES; THERMAL ANALYSIS; TRANSITION ELEMENTS; YIELDS; 400201* - Chemical & Physicochemical Properties; 010408 - Coal, Lignite, & Peat- C1 Processes- (1987-); 330702 - Emission Control- Carbon Monoxide

Citation Formats

Tavares, M T, Bernardo, C A, Alstrup, I, and Rostrup-Nielsen, J R. CO disproportionation on silica-supported nickel and nickel-copper catalysts. United States: N. p., 1994. Web. doi:10.1006/jcat.1994.1169.
Tavares, M T, Bernardo, C A, Alstrup, I, & Rostrup-Nielsen, J R. CO disproportionation on silica-supported nickel and nickel-copper catalysts. United States. https://doi.org/10.1006/jcat.1994.1169
Tavares, M T, Bernardo, C A, Alstrup, I, and Rostrup-Nielsen, J R. 1994. "CO disproportionation on silica-supported nickel and nickel-copper catalysts". United States. https://doi.org/10.1006/jcat.1994.1169.
@article{osti_7275848,
title = {CO disproportionation on silica-supported nickel and nickel-copper catalysts},
author = {Tavares, M T and Bernardo, C A and Alstrup, I and Rostrup-Nielsen, J R},
abstractNote = {The carbon formation/gasification equilibrium on silica-supported nickel and nickel-copper catalysts in CO + CO[sub 2] gas mixtures and the steady state kinetics of carbon formation from CO on the same catalysts were studied in a thermogravimetric flow system. The equilibrium gas composition was found to be the same for the nickel and the nickel-copper catalysts except at the highest copper concentrations ([ge]25 at.%), where larger deviations from graphite equilibrium were found at the lowest temperature (673 K). The deviations at equilibrium of the free energy, [delta]G[sub c], from the value calculated for graphite equilibrium were larger than found previously for carbon formation in CH[sub 4] + H[sub 2] gas mixtures. The steady-state kinetic results have been modelled by using a simple Langmuir model with one type of site. In contrast to some previous studies of carbon formation from CO, the present kinetic results are well described by a model in which the surface reaction of two CO molecules to form carbon and CO[sub 2] is the rate-limiting step at temperatures below about 680 K and CO pressures in the range 15-50 kPa. At higher temperatures and pressures, the experimental rates fall below the model rates, probably due to diffusion limitations and to the partial coverage of the active surface by graphitic carbon. The conflict whereby a model with CO dissociation as the rate-limiting step gives a better description of the results of some previous kinetic studies of carbon formation from CO is suggested to be resolved by assuming that the latter model is valid when the CO pressure is low or when the gas contains CO[sub 2]. 31 refs., 9 figs., 7 tabs.},
doi = {10.1006/jcat.1994.1169},
url = {https://www.osti.gov/biblio/7275848}, journal = {Journal of Catalysis; (United States)},
issn = {0021-9517},
number = ,
volume = 147:2,
place = {United States},
year = {Wed Jun 01 00:00:00 EDT 1994},
month = {Wed Jun 01 00:00:00 EDT 1994}
}