Khairullina, I. A.

Kryuchkova, T. A.

Serov, Y. M.

Sheshko, T. F.

BSU Digital Library

 50 
Catalytic properties features of perovskite-type ferrites in dry 
 (carbon dioxide) methane reforming 
T. A. Kryuchkova1, I. A. Khairullina1, T. F. Sheshko1, Y. M. Serov1,  
I. V. Chislova2, I. A. Zvereva2 
1 Peoples Friendship University of Russia, Moscow, Russia 
2 Saint-Petersburg State University, Saint-Petersburg, Russia 
e-mail: tatyanakruychkova@mail.ru 
The perovskite-type ferrites GdSrFeO4, Gd2SrFe2O7, GdFeO3 and solid solutions 
Gd2‒хSr1+хFe2O7 (x = 0.1‒0.6) were synthesized by the high temperature solid-state reactions and 
by sol-gel technology. 
The complex physico-chemical investigations showed that synthesized catalysts are well-
crystalline homogenous perovskite-type ferrites with different number of perovskite layers 
GdSrFeO4 (n  =  1), Gd2SrFe2O7 (n  = 2), GdFeO3 (n = ∞) and solid solutions Gd2‒хSr1+хFe2O7. Sam-
ples obtained by ceramic technology are in microcrystalline state and the iron atoms are found in 
Fe3+ state, which is magnetically ordered; oxides prepared by sol-gel technology are in nanocrys-
talline state and iron atoms are in a heterovalent state (Fe3+ coexists with Fe+4) in three different 
symmetry fields.  
The maximum conversion (αСН4 = 37 %, αCO2 = 57 %) and products formation rate (WH2 = 
0.07 mol/(h∙g), WCO = 0.16 mol/(h∙g)) were achieved by performing the reaction at an equimolar 
ratio of СН4 and СО2. In spite of high temperatures the catalytic activity did not decrease during 
40 hours. The catalyst demonstrated the high resistance to coke formation.  
Among the reaction products the water was detected in almost all investigated ferrites, the 
quantity of generated carbon monoxide was 2‒4 times greater than the quantity of hydrogen and 
carbon dioxide conversion was almost two times higher than methane conversion. Activation 
energies of CO formation and the corresponding values of lnk0 were less than the similar values 
of Еа and lnk0 for hydrogen. On the base of these data it was suggested that the DRM reaction 
was complicated by the reverse steam reforming of CO. 
It was shown that an increase in the number of perovskite layers (n) in the complex oxides 
structure led to an increase in the catalytic activity. A partial substitution or complete replace-
ment of Gd3+ ions by Sr2+ ions led to some reduction of activity. Among the systems of variable 
composition Gd2‒xSr1+xFe2O7 obtained by the sol-gel technology samples had the highest activity 
at x = 0.3. The increase in strontium content led to lowering the symmetry of the surroundings of 
Fe+3 atoms and to occurrence of heterovalent state of iron atoms (Fe3+, Fe4+) with oxygen vacan-
cies. It influenced an increase in the total surface acidity and catalytic activity in terms of CO2 
conversion. The catalytic activity increased in the row SrFeO3‒x (n = ∞) ≈ GdSrFeO4 (n = 1) ≈ 
Gd2‒xSr1+xFe2O7  (n = 2) < GdFeO3 (ceramic) (n = ∞) < GdFeO3 (sol-gel) (n = ∞).  Higher cata-
lytic properties of perovskite-type ferrites synthesized by sol-gel technology can be associated 
with their nanocrystalline state, a porous structure, as well as with heterovalent iron state and ox-
ygen vacancies, which probably are favorable for the surface oxidation-reduction reactions and 
the process of CO2 activation. 
 
Acknowledgment. The reported study was supported by the Russian Foundation for Basic 
Research grant 14-03-00940. 
 


Catalytic properties features of perovskite-type ferrites in dry  (carbon dioxide) methane reforming

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Catalytic properties features of perovskite-type ferrites in dry (carbon dioxide) methane reforming

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