Golub N.P., Golub E.O., Kozma A.A., Hlebena H.F., Mikhalchuk H.M., Kuznietsova A.O. SYNTHESIS AND RESEARCH OF A COMPLEX MANGANESE-NICKELPHOSPHATE CATALYTIC SYSTEM

Abstract

Individual Mn2P2O7 and Ni3(PO4)2 phosphate catalysts were synthesized. A new synthesis technique was developed and a new complex catalytic system хMn2P2O7×yNi3(PO4)2 was obtained based on them (К-1 – К-7), which has the predicted physicochemical properties. The composition of these phosphates in the structure of the catalyst was varied in the range of 0,5 – 99,5 wt.%. It was established that the conditions of synthesis of catalysts significantly influence the process of forming the composition, structure, and corresponding physicochemical parameters of the synthesized catalysts. On the thermogram of the differential thermal analysis of an individual manganese-phosphate catalyst, three endo-effects at 148°С, 220°С and 353°С and one exo-effect at 460°С are observed. The thermogram of individual Ni3(PO4)2 shows two endo-effects at 210°С and 372°С and one exo-effect at 803°С. The synthesized double manganese-containing systems are characterized by a significant difference in DTA curves for samples K-1 - K-7. All obtained air-dry samples are crystal hydras with different numbers of water molecules. The structure of the obtained series of complex manganese-nickel phosphate catalysts contains various forms of water. The process of dehydration contributes to its separation from the structure of the samples and leads to the occurrence of characteristic endothermic effects. On all synthesized complex samples, the transition of manganese (II) orthophosphate to its pyrophosphate is observed when the final heat treatment temperature is reached. Firing samples of synthesized catalysts above 700oC leads to their complete dehydration with the formation of anhydrous salts. DTA results for all synthesized manganese-nickel phosphate samples are in good agreement with their X-ray diffraction, IR spectroscopy, and surface acidity results. They confirmed the correct choice of the modifying ion to improve the structure and physicochemical parameters of the manganese (II) phosphate catalyst. It can be predicted that the synthesized new complex oxide catalysts will show improved catalytic properties (activity and selectivity) in the processes of partial oxidation of n-alkanes into valuable products. The synthesized double manganese-containing systems are characterized by a significant difference in DTA curves for samples K-1 - K-7. All obtained air-dry samples are crystal hydras with different numbers of water molecules. The structure of the obtained series of complex manganese-nickel phosphate catalysts contains various forms of water. The process of dehydration contributes to its separation from the structure of the samples and leads to the occurrence of characteristic endothermic effects. On all synthesized complex samples, the transition of manganese (II) orthophosphate to its pyrophosphate is observed when the final heat treatment temperature is reached. Firing samples of synthesized catalysts above 700oC leads to their complete dehydration with the formation of anhydrous salts. DTA results for all synthesized manganese-nickel phosphate samples are in good agreement with their X-ray diffraction, IR spectroscopy, and surface acidity results. They confirmed the correct choice of the modifying ion to improve the structure and physicochemical parameters of the manganese (II) phosphate catalyst. It can be predicted that the synthesized new complex oxide catalysts will show improved catalytic properties (activity and selectivity) in the processes of partial oxidation of n-alkanes into valuable products.
 Keywords: catalysis; catalyst; catalytic systems; complex oxides; heterogeneous catalysis; phosphates; oxidation; n-alkanes; hydrocarbons; ethane; ethylene; differential thermal analysis.