<p class="Mabstract">An X-ray study of the phase composition of Mo-W-O, Ti-W-O, and Cu-W-O catalysts was carried out. Analysis of X-ray diffraction patterns of the Mo-W-O catalytic system showed that in all samples, mainly the phases of molybdenum and tungsten oxides, namely MoO<sub>3</sub> and WO<sub>3</sub>, are formed. It is shown that, in contrast to Mo-W-O catalysts, in addition to the initial titanium and tungsten oxides, the samples of the Ti-W-O catalytic system also contain phases of chemical compounds. So, in Ti-W-O samples, there are phases of titanium oxide (anatase), titanium oxide (rutile), and tungsten oxide. It has been established that the degree of crystallinity of binary titanium-tungsten oxide samples decreases with increasing titanium content in the catalyst composition from 83.4% to 70.2%. In the case of copper-tungsten oxide catalysts, in addition to the initial oxides of copper and tungsten also contain phases of the chemical compound of copper tungstate, and crystallinity degrees of binary copper-tungsten oxide samples changes in the ranges from 85.7% to 41.3%.<strong></strong></p>