Dynamics of structural transformations in the reduction of copper aluminate

Citation
Lm. Plyasova et al., Dynamics of structural transformations in the reduction of copper aluminate, KINET CATAL, 41(3), 2000, pp. 429-436
Citations number
11
Categorie Soggetti
Physical Chemistry/Chemical Physics","Chemical Engineering
Journal title
KINETICS AND CATALYSIS
ISSN journal
00231584 → ACNP
Volume
41
Issue
3
Year of publication
2000
Pages
429 - 436
Database
ISI
SICI code
0023-1584(200005/06)41:3<429:DOSTIT>2.0.ZU;2-O
Abstract
The dynamics of structural transformations during copper aluminate reductio n in the temperature range used for catalyst activation was studied by high -temperature X-ray analysis under controlled conditions (hydrogen, 20-400 d egrees C). The techniques of neutron diffraction analysis, IR spectroscopy, chemical phase analysis, and electron microscopy were also used at particu lar stages. In the course of reduction, copper metal is deposited onto the surface of spinel crystals from the bulk. Spinel becomes cation-deficient w ith respect to copper. An analysis of powder diffraction patterns demonstra ted that copper is reduced and released from tetrahedral positions of the s pinel structure at temperatures below similar to 300 degrees C and from oct ahedral positions only at temperatures above 300 degrees C. In this case, a redistribution of aluminum ions was observed simultaneously. It is likely that the electrical neutrality is attained by the formation of OH groups, t he appearance of which in reduced samples was detected by IR spectroscopy a nd confirmed by neutron diffraction analysis. At a reduction temperature of 400 degrees C, the oxygen framework was partially disintegrated. The struc tures of reduced copper aluminates and chromites were compared.