THE X-RAY DIFFRACTION ANALYSIS OF A COMPLEX OXIDE CATALYST OF 50%Cu3(PO4)2•50%Ni3(PO4)2

Abstract

Preparation of initial orthophosphates of Copper (II) and Nickel (II) and a complex catalytic system based on them 50 % Cu3(PO4)2∙50 % Ni3(PO4)2 was carried out according to the methods developed at the Department of Physical and Colloid Chemistry, of Uzhhorod National University. The synthesized system was investigated by X-ray phase analysis. Experimental diffraction patterns show that air-dry samples of the initial components and the intermediate sample of 50%Cu3(PO4)2∙3H2O•50%Ni3(PO4)2∙8H2O are very different from each other. This gives grounds to assume that the air-dry phosphate of the catalytic system 50%Cu3(PO4)2∙3H2O•50%Ni3(PO4)2∙8H2O can be characterized as a new phase. Annealing of the obtained air-dry complex sample in the temperature range 120-700ºС leads to the corresponding physicochemical transformations. Experimental data show that the structure of the formed intermediate air-dry sample after heat treatment undergoes significant changes. At the same time, heat treatment leads to gradual partial or complete dehydration of a complex catalytic system. When 600ºC is reached, the dry X-ray amorphous catalyst begins to crystallize. This is due to the gradual dehydration of the catalyst at lower temperatures with the loss of much of the chemically bound water and the transition to the amorphous state. The process of forming the crystal structure of the dehydrated complex sample is significantly intensified when reaching 700ºC. Thus, the calcination of the synthesized phosphate phase in the specified temperature range allows not only to carry out its complete dehydration, but also, to a large extent, promotes the gradual crystallization of the dehydrated phase. In turn, this causes the formation on the surface of the synthesized complex copper-nickel phosphate catalyst system of 50%Cu3(PO4)2∙3H2O•50%Ni3(PO4)2∙8H2O acid active centers of appropriate strength. It was also found that if necessary to obtain a fully dehydrated and crystallized copper-nickel-phosphate sample, the duration of calcination at a final temperature of 700ºC should be carried out more than 1 hour.
 Keywords: X-Ray Diffraction (XRD) analysis; catalysts; сopper (II) orthophosphate; nickel (II) orthophosphate; catalytic 50 % Cu3(PO4)2∙50 % Ni3(PO4)2 system.