THE DIFFERENTIAL THERMAL ANALYSIS OF COMPLEX CATALYTIC SYSTEM OF TYPE xFePO4•yNi3(PO4)2

Abstract

By means of a method of the differential thermal analysis (DTA), the behavior of a series of catalysts to К-1–К-7 which are implemented in the xFePO4•yNi3(PO4)2 system is investigated temperature. The corresponding series of catalysts to К-1–К-7 was synthesized according to the technique developed at Department of Physical and Colloidal Chemistry of the Uzhhorod National University. Relying on these results us transformations which happen when heating intermediate samples of catalytic xFePO4•yNi3(PO4)2 system are described. The K-1 catalyst (original composition 99,5 mass % FePO4 ‒ 0,5 mass % Ni3(PO4)2) on the structure the next to initial iron (III) orthophosphate crystalline hydrate (FePO4•2H2O) also has the most difficult enrollment of effects. The first of them and the only endothermic is observed at 139ºС. This effect corresponds to the beginning of loss of crystallizational water and destruction of structure of basic hydrate. All subsequent effects which are observed on the thermogram belong to exothermic. At a temperature 302ºС the most intensive is fixed among them which answer the beginnings of crystallization of the dehydrated amorphous phase. Catalysts K-2 (99,0 mass % FePO4 ‒ 1,0 mass % Ni3(PO4)2) and K-3 are also characterized by one considerable by the size endoeffect at 145ºС. At increase in a share of nickel upon transition from sample К-2 to К-3, the areas exoeffect significantly decrease. It demonstrates about reduction of impact of iron containing structural modifications by the general physical and chemical characteristic of these catalysts. Further increase in nickel in sample К-4 (50,0 mass % FePO4 ‒ 50,0 mass % Ni3(PO4)2) lowers temperature uniform to an a little endoeffect to 119ºС. Also it is fixed exoeffect at 735ºС which is already shown on the catalyst to К-3. Possibly, at this temperature there is a formation of a quantity of nickel (II) pyrophosphate. The thermograms of catalysts К-5–К-7 (where К-5: 25,0 mass % FePO4 ‒ 75,0 mass % Ni3(PO4)2; К-6: 1,0 mass % FePO4 ‒ 99,0 mass % Ni3(PO4)2; К-7: 0,5 mass % FePO4 ‒ 99,5 mass % Ni3(PO4)2) have considerable similarity. On all presented samples it is observed one endoeffect at 123ºС.