Investigation of Structural-Phase Conversion of an Iron-Containing Catalyst by Mössbauer Spectroscopy (Part 2)

The active form of an iron-containing catalyst, an Fe(II, III) mixed oxide, was studied by Mössbauer spectroscopy in order to identify the mechanism of formation of catalysts used for upgrading of heavy oil from Ashalchinsk field. The iron-oxide phase participates in the formation process by breaking carbon–heteroatom bonds in high-molecular-mass components (resins and asphaltenes) of heavy oil and reduces their molecular mass. Thus, the disperse iron oxides are enriched in a sulfur-containing phase. Mathematical processing of Mössbauer spectra obtained during the experiment was used to study the quantitative composition of the products of thermocatalytic action at 300°C. Magnetite (Fe 3 O 4 ), greigite (Fe 3 S 4 ), pyrite (FeS 2 ), and pyrrhotite (Fe 1–x S) were mainly detected in the isolated catalysts. The magnetite content decreased toward formation of iron sulfides (pyrite and pyrrhotite). Hydrogen sulfide and hydrocarbons were formed as a result of cracking, hydrolysis, and hydrogenolysis reactions at 300°C.