Low-Zeolite HY–Al2O3 Catalysts with Tailored Alumina Matrix Properties for Cracking of Heavy Fuel Oil

The effect of the composition and structure of shaped low-zeolite Al2O3-based catalysts on the catalytic cracking of M–100 heavy fuel oil was investigated. A series of γ-Al2O3-based catalysts was prepared, including an HY-containing catalyst and materials additionally modified with η-Al2O3, CaO, and Ni- and Cu-containing components. The physicochemical properties of the samples were characterized by X-ray diffraction, Fourier-transform IR spectroscopy, and low-temperature nitrogen adsorption. The pore volume and the mechanical strength of the catalyst granules were additionally measured. Catalytic cracking tests were carried out in a flow reactor at 450–550 °C. It was shown that the incorporation of 5 wt.% HY into γ-Al2O3 increased the combined yield of gasoline and light gas oil fractions at 450 °C from 16.3 to 38.3 wt.%. Modification of the alumina matrix further affected the catalyst selectivity: the γ+η–Al–HY catalyst provided the highest yield of light products (42.8 wt.%) and the lowest coke yield, whereas Ca–Al–HY exhibited the highest gasoline yield (23.7 wt.%) together with the lowest heavy residue yield. The effect of matrix composition became particularly pronounced at 500–550 °C, which can be attributed to changes in both pore structure and surface acid-base properties enhanced by modification. Product composition analysis showed that the incorporation of HY increased the content of light olefins, whereas modification of the matrix substantially altered the ratio of normal to branched paraffinic components in the gasoline fraction. The Ca–Al–HY sample exhibited the smallest changes in textural properties after catalytic testing and a more stable product distribution during consecutive reaction–regeneration cycles. These results demonstrate that, at a low HY content, the alumina matrix acts as an independent factor governing selectivity and stability of the catalyst in heavy residual feedstocks conversion.