PTQ Q1 2026 Issue

role in ensuring successful operation, particularly through selective hydrogenation, which helps control sediment formation. Beyond this, cata- lysts provide several additional benefits via various catalytic reactions. These include: •Hydrodesulphurisation (HDS) for sulphur removal, enabling the production of ultra-low sulphur fuels. • Hydrodemetallation (HDM)

Asphaltene in oil

Resid conversion

Asphaltene separation

Asph

Resins

Asph

Figure 2 How composition of oil impacts sediment formation during cracking

species by terminating free radical propagation and com- bination reactions. This step minimises sediment and gas formation, and delays the onset of coking associated with increased conversion. Effective sediment control is vital to the successful oper- ation of EBRHC. To begin to understand this, it is useful to consider the types of molecules found in resid. Resid can be classified into four categories based on their solubility: saturates, aromatics, resins, and asphaltenes. The saturates and aromatic fractions contain no metals, and compared to resins and asphaltenes, have a low carbon-forming tendency and a higher hydrogen-to-carbon (H/C) ratio. Asphaltenes contain the highest level of metals, have the highest coke-forming tendency, the lowest H/C ratio, and are responsible for sediment formation. Figure 2 is a schematic representation showing the inter- actions between these groups of molecules and how they can lead to sediment formation during the process of resid conversion. On the left is shown the composition of the resid feedstock oil. Asphaltenes form the core of a colloidal structure surrounded by resins, which are polar compounds high in sulphur, oxygen, and nitrogen heteroatoms. Resins act as dispersants, separating the asphaltenes from the surrounding aromatics and saturates. While asphaltenes are insoluble in saturates alone, they remain suspended in the bulk oil due to the stabilising effects and positioning of both aromatics and resins. The middle picture illustrates how oil composition evolves during resid conversion. As resins and aromatics undergo hydrogenation, their concentrations decrease, resulting in an increase in saturates. Simultaneously, the H/C ratio in asphaltenes declines due to side-chain cracking and the low hydrogenation rate of their aromatic cores. Eventually, the rising saturate content destabilises the colloidal system, making the converted asphaltenes insol- uble. The right schematic shows asphaltenes precipitating from the oil, fragmenting from the colloidal structure, and agglomerating into sediment that can initiate coking reac- tions and fouling. Effective asphaltene management, i.e. keeping them stable in the oil, is crucial for optimising resid hydrocracker performance, with ebullated bed catalyst design being the primary lever for control. Catalyst fundamentals As described, most residue conversion in hydrocracking pro- cesses occurs thermally. However, catalysts play a crucial

for capturing metals such as nickel and vanadium, thereby protecting downstream catalyst systems from deactivation. • Hydrodenitrogenation and Conradson carbon residue removal (HDCCR), which enhance yield and performance in subsequent processing stages. Optimising pore volume and pore size distribution is crit- ical to catalyst performance. To process large, high molec- ular weight compounds effectively, the catalyst must have the right balance of macropores. Pores larger than 25 nm are especially effective in facilitating the diffusion of large asphaltene molecules into the catalyst and promoting demetallation. The intrinsic reaction rate, largely governed by the cata- lyst’s surface area and thus the mesopores, influences key processes such as HDS and HDCCR, as well as the resid conversion characteristics of the catalysts that ensure max- imum asphaltene stability. Catalytic performance is further influenced by the amount, dispersion, and distribution of the active metals, molybdenum and nickel. Additionally, the importance of the alumina support properties cannot be underestimated in terms of the physical properties of the resulting catalysts, impacting mechanical strength and ebullating properties. Catalyst technology platforms Five distinct catalyst technology platforms have been developed by ART, a Grace Company, resulting in the commercialisation of several series of catalysts. EBRHC catalysts are typically designed to balance catalytic activ- ity with metals capacity. In general, an increase in metals capacity comes at the expense of catalytic activity, and vice versa. A brief description of each platform is provided below: • DCS : Offers extremely high metals capacity. Suitable for feeds with very high metal content (Ni + V > 380 ppm). • ECAD : Applicable across a range of feedstocks. Enables lower catalyst consumption and enhances bottoms product stability. • HSLS : A highly versatile catalyst series that provides a strong combination of catalytic activity and effective sed- iment control. • HSLS Plus : Comparable metals-handling capacity to HSLS, but with enhanced HDS and HDCCR activity. • LS : Designed with lower metals tolerance than HSLS, but offers higher catalytic activity. Commonly used as the sec- ond-stage catalyst in dual catalyst configurations.

PTQ Q1 2026