chromite catalysts [110]. A novel environment friendly vapour phase
synthesis of different classes of nitrogen containing heterocyclic
compounds was
developed by
Campanati et al. [330] using non hazardous, commercially available and low cost feeds. 2
Methyl 8 ethylquinoline MEQUI was synthesized from 2 ethylaniline 2 ETAN and ethylene glycol
EG or chloro ethanol CE, operating at high temperature in the presence of acid treated K10
montmorillonite or ZnCl
2
K10 montmorillonite. At lower temperatures and using copper chromite
catalysts, 7 ethylindole 7 ETI or 5 ethylindole 5 ETI were obtained from 2 ETAN or 4 ethylaniline
4 ETAN, respectively, and EG; excess of alkyl aniline was required to avoid the formation of
polyalkylated by products. Mixing SiO
2
with the best copper chromite, made it possible to operate
with higher LHSV values, thus improving the yield in alkylindoles. Finally, N 2 ethylphenyl pyrrole
EPP and N 2 ethylphenyl pyrrolidine EPD were synthesised using a commercial copper
chromite catalyst and feeding 2 ETAN and 2,3 dihydrofuran DHF, EPP being favoured by high
temperatures and absence of water in the feed Fig. 15.
3. Preparation methods of copper chromite catalyst
Catalysts, when prepared via different routes, would demonstrate different properties, even with
the same starting compositions. Crystallinity, surface properties, and specific surface area, three
of the most important parameters determining the catalytic activity of the product are highly
dependent on the synthesizing routes [14]. Several preparation methods have been established to
prepare CuCr
2
O
4
, for instance chromium and copper doubly promoted ceria catalysts have been
prepared by Harrison et al. [331] by three routes: A
coprecipitation from
aqueous solutions
containing ceriumIV, copperII, and chromium III ions, B sequential impregnation of CeO
2
by using an aqueous CrO
3
solution followed by an aqueous solution of copperII nitrate, and C
impregnation of
CuIICeO
2
prepared by
coprecipitation by using an aqueous CrO
3
solution. They found that at low processing temperatures,
copper is present as polymeric CuOH
2
in both the
CuCrCeO
2
cop and
CuCrCeO
2
copimp materials. Chromium is present as adsorbed
Cr
2
O
72
ions in the CuCrCeO
2
impimp and Cu CrCeO
2
copimp materials, but a variety of chromium species in oxidation states +III, +V and
+VI are present in the CuCrCeO
2
cop material. Brief descriptions of synthesis principles,
typical processes, important aspects that influence the characteristics, specific advantages and some
experimental data are presented for the following methods for the preparation of CuCr
2
O
4
catalysts: Co precipitation method
Adkins’ method Complexing coprecipitation method
Co impregnation method Thermal decomposition ACOC
Thermal decomposition
of ammoniacal
copper oxalate chromate ACOC Hydrothermal method
Non Casting method: Template technique Hydrolysis of some soluble salts
Microemulsion method
Copyright © 2011, BCREC, ISSN 1978 2993 Fig. 14. A generalized reaction pathway for the for
mation of pyrazine and other products. Fig. 15. Reaction pathway for the synthesis of
, 2 ethylphenyl
pyrrole EPP
and ,
ethylphenyl pyrrolidine EPD using CuCr
2
O
4
catalysts [331]
Combustion synthesis Self propagating
high temperature synthesis
Solution combustion synthesis Electroless method
Sonochemical method Metal organic chemical vapour deposition
MOCVD Flame Synthesis of Nanostructured
Chemical reduction method Sol gel process
Citric acid CA complexing approach Pechini Method
Non alkoxide sol gel route
3. 1 Co,precipitation method 3.1.1 Adkins′ method
