Abstract <p>The oil and gas refining industry in Russia and other countries is faced with the challenge of searching for new highly active catalytic systems and innovative methods for processing various types of petroleum feedstocks, including heavy petroleum feedstocks. One of the main tasks of this industry is to increase the depth of processing of petroleum raw materials to obtain more valuable petrochemical products. The purpose of the work is to study the dependence of the thermal destruction of heavy petroleum feedstock—heavy vacuum gas oil from the AVT-5 unit of PAO Bashneft-Novoil—in the presence of a new metal-complex catalytic system, where the active component is a chlorferrate complex (NaFeCl₄) in an amount of 10%, deposited on a carrier representing a deeply decationized Ymmm zeolite of the acidic form (H-form), when varying process conditions, temperature in the range from 450 to 550°C, and volumetric feed rate of raw materials in the range 1.75–2.50 h^–1. The physicochemical characteristics of the metal complex catalyst—10% NaFeCl₄/HYmmm zeolite—are studied: characteristics of the porous structure, phase composition, and morphology of the surfaces of the catalytic systems. During the experimental studies, it is established that the 10% NaFeCl₄/HYmmm zeolite catalytic system has a highly developed surface with a pore distribution of micro-, meso-, and macropore sizes (total pore volume ~0.64 cm³/g) and preserves the degree of crystallinity of the lattices relative to the original support Ymmm. It is established that the thermocatalytic destruction of heavy vacuum gas oil in the presence of a metal complex catalyst leads to its deep and selective conversion. Data are obtained indicating that in the studied modes of the thermal destruction process, it is possible to achieve the formation of unsaturated olefinic hydrocarbons of the composition C₂–C₄ ~20 wt %, gasoline fraction ~45 wt %, and total light ~68 wt %.</p>