XRD studies of evolution of catalytic nickel nanoparticles during synthesis of filamentous carbon from methane

Citation
Ma. Ermakova et al., XRD studies of evolution of catalytic nickel nanoparticles during synthesis of filamentous carbon from methane, CATAL LETT, 62(2-4), 1999, pp. 93-97
Citations number
30
Categorie Soggetti
Physical Chemistry/Chemical Physics","Chemical Engineering
Journal title
CATALYSIS LETTERS
ISSN journal
1011372X → ACNP
Volume
62
Issue
2-4
Year of publication
1999
Pages
93 - 97
Database
ISI
SICI code
1011-372X(1999)62:2-4<93:XSOEOC>2.0.ZU;2-P
Abstract
The XDR technique was used for studying a series of high-loaded (90%) nicke l catalysts with silica as a textural promoter. These were catalysts for di rect cracking of methane at 550(degrees)C. A relation between the initial a verage size of active catalyst particles, carbon yield and average methane conversion was demonstrated. Genesis of these catalysts was studied includi ng oxide precursors, reduced catalysts prior to the reaction, as well as ca talysts upon their contacting the reaction medium for various periods of ti me from 15 min to 2 h. The active catalyst particles were shown to merge or disperse at the outset of the reaction depending on their initial size. An yway, close average sizes ranging from 30 to 40 nm were observed by the end of the first reaction hour for all the catalytic systems providing the car bon yield of 300-385 g/g Ni. The catalytic system was shown to self-organiz e in the course of direct methane cracking, i.e., the catalyst particles tr ansform in response to the reaction conditions. If the size of nickel parti cles cannot vary, these catalysts are inefficient for the given process.