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The performance of catalysts prepared from hierarchical Y zeolites has been studied during the conversion of vacuum gas oil (VGO) into higher-value products. Two different catalysts have been studied: CatY.0.00 was obtained from the standard zeolite (Y-0.00-M: without alkaline treatment) and CatY.0.20 was prepared from the desilicated zeolite (Y-0-20-M: treated with 0.20 M NaOH). The cracking tests were carried out in a microactivity test (MAT) unit with a fixed-bed reactor at 550 ◦C in the 20–50 s reaction time range, with a catalyst mass of 3 g and a mass flow rate of VGO of 2.0 g/min. The products obtained were grouped according to their boiling point range in dry gas (DG), liquefied petroleum gas (LPG), naphtha, and coke. The results showed a greater conversion and selectivity to gasoline with the CatY.0.20 catalyst, along with improved quality (RON) of the C5–C12 cut. Conversely, the CatY.0.00 catalyst (obtained from the Y-0.00-M zeolite) showed greater selectivity to gases (DG and LPG), attributable to the electronic confinement effect within the microporous channels of the zeolite. The nature of coke has been studied using different analysis techniques and the impact on the catalysts by comparing the properties of the fresh and deactivated catalysts. The coke deposited on the catalyst surfaces was responsible for the loss of activity; however, the CatY.0.20 catalyst showed greater resistance to deactivation by coke, despite showing the highest selectivity. Given that the reaction occurs in the acid sites of the zeolite and not in the matrix, the increased degree of mesoporosity of the zeolite in the CatY.0.20 catalyst facilitated the outward diffusion of products from the zeolitic channels to the matrix, thereby preserving greater activity [ABSTRACT FROM AUTHOR]

The impact of the composition of the various hydrocarbon fractions in a conventional VGO (saturated SF, aromatic AF and resin RF) and the whole VGO on the coke formed in their catalytic cracking was evaluated over two Y zeolites with different degree of mesoporosity. The parent zeolite was in its protonic form, Si/Al relationship of 30 and the modified sample was desilicated by alkaline treatment. The fractions were separated from the VGO by means of ASTM D2007-11 method. The catalytic conversion experiments were performed in a batch, fluidized bed laboratory Riser Simulator reactor at 500 °C in the 0.7–3.0 s reaction time range, with a zeolite mass of 0.2 g and a zeolite/reactant mass of 1. Independent of zeolite, fraction SF was the easiest to crack. In the case of the AF fraction, the modified zeolite, with the highest intracrystalline mesoporosity, was more active than the parent zeolite. Gasoline was always the main product, with selectivities from 60 to 70%. All the feedstocks produced more coke on the modified zeolite; however, in spite of the higher coke yields, this zeolite suffered a lower loss of total acidity. As expected, a negative change in both acidity and textural properties (specific surface area and pore volume) were observed as a consequence of the formation of coke. The reactivity of VGO over both zeolites differed from that of fraction SF, even though it was the major fraction (68%). This behavior could be the consequence of interactions between the various fractions composing VGO. [ABSTRACT FROM AUTHOR]