1994 Fiscal Year Final Research Report Summary
"Study on Structure and Physico-chemical Properties of Hydrotalcite-like Compounds Containing Zinc Cations"
| Project/Area Number |
05455003
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
広領域
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| Research Institution | AKITA UNIVERSITY |
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Principal Investigator |
FUDA Kiyoshi Akita University, Mining College, Assistant Professor, 鉱山学部, 助教授 (80181428)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUNAGA Toshiaki Akita University, Mining College, Professor, 鉱山学部, 教授 (40006309)
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| Project Period (FY) |
1993 – 1994
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| Keywords | HYDROTALCITE-LIKECOMPOUND / CRYSTAL STRUCTURE / INFRA-RED SPECTRUM / THERMAL DECOMPOSITION / RIETVELD REFINEMENT / ZINC / GALLIUM / CROMIUM |
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| Research Abstract |
From investigation of structure and physico-chemical properties of hydrotalcite-like compounds containing zinc cation (Zn/Al-, Zn/Ga- and Zn/Cr-HTlcs) , following findings were obatined.
Rietiveld refinement of the X-ray diffraction pattern of Zn/Al-HTlc revealed that its structure is very similar to that of natural hydrotalcite (Mg/Al-HT) even in the internal positions of the atoms in the unit cell. On the other hand, FT-IR study showed that the M-O bonds are rather strong but O-H bonds are rather weak than those in Mg/Al-HT,suggesting partial contribution of covalency in Zn-O bonds.
It was found that the thermal decomposition behavior of Zn/Al-HTlc is different from that of Mg/Al-HT.In this compound, half of hydroxils in the brucite-like layrs decompose even below 200ﾟC,on the other hand, CO_3^<2-> ions decompose over 500ﾟC,which shows apparent double peaked CO_2 evolution at 580ﾟC and 780ﾟC in case of the samples with x (=Al/ (Al+Zn)) close to 1/3. Such unique behavior seems to be rel
… More
ated with some degree of tendency to formation of covalent bond in Zn-O as well as rather high degree of 2 : 1-type ordering in cation distribution in the brucite-like layrs.
Well crystallized Zn/Ga-HTlc powder sample can be obtained by conventional coprecipitation method. Its structure and thermal decomposition behavior are very similar to those of Zn/Al-HTlc. The decomposition of hydroxils and CO_3^<2-> ions also occurs separately in this compound.
In comparison with above two compound, Zn/Cr-HTlc showed somewhat different properties. The crystallinity is lower and the decomposition of CO_3^<2-> occurs at temperatures below 500ﾟC.In addition, it was found that the thermal decomposition of CO_3^<2-> ions associated with formation of CrO_4^<2-> ions in the solid phase. This oxidation of CrCr^<3+> to _<6+> was enhanced by existence of oxygen molecules in the atmosphere and CO_3^<2-> ions in the interlayr space of the starting hydroxide, suggesting catalytic effects on this oxidation of some intermediates produced from CO_3^<2-> ions during thermal decomposition process. Less
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