PTQ Q1 2026 Issue

From residue to revenue with ebullated bed residue hydrocracking

Achieve greater flexibility in processing a wider range of heavy, high-metal, and high-contaminant crudes at higher yields and reliability

Colin Baillie, Darryl Klein, and Sidhartha Mohanty W. R. Grace & Co.

T he story of ebullated bed residue hydrocracking (EBRHC) started in the late 1960s. Fixed-bed hydro- cracking was initially used for residue upgrading, but suffered from catalyst deactivation requiring frequent shutdowns for catalyst replacement. Residue hydrocrack- ing technologies subsequently evolved to an ebullated bed process. Such systems improved upon fixed-bed reactors by allowing continuous catalyst addition and withdrawal, addressing the problem of catalyst deactivation, as well as other issues such as pressure drop build-up. In the present day, EBRHC continues to be attractive to refiners because it offers several key advantages over alternative residue upgrading processes, such as fixed-bed resid (FBR) hydrotreating, visbreaking, and coking. E BRHC converts a significant portion of vacuum residue (VR) into valuable distillates, reducing low-value fuel oil pro- duction, with up to 90% (538+°C) conversion achievable. This is significantly higher than the 30-40% conversion typically achieved with FBR hydrotreating. Another advantage versus FBR hydrotreating is that fresh catalyst can be continuously added and withdrawn, maintaining high activity, extending unit run lengths, and avoiding periodic shutdowns. I n addition, EBRHC allows for greater feedstock flexibility and can process a wider range of heavy, high-metal, and high-contaminant crudes. For example, the maximum feed metals for the EBRHC process are typically 700 ppm, which is significantly higher than the 200 ppm maximum associ - ated with FBR hydrotreating. Whereas coking achieves residue upgrading through a carbon rejection process, EBRHC is fundamentally differ- ent in that it proceeds via hydrogen addition. This results in lower coke and sediment formation, leading to better yield and reliability, while hydrogen incorporation into the cracked products enhances product quality. Figure 1 highlights the steady growth of resid hydroc- racking (RHC) units since the late 1960s. With new EBRHC units set to start up in late 2025/early 2026 and additional units under construction, a total of 23 units are expected to be operational by 2030. Chemistry and importance of sediment control The chemistry in EBRHC resembles that of conventional hydrocracking but is specific to extremely heavy feedstocks

that include asphaltenes and metals. It involves the cleav- age of carbon-carbon (C-C) bonds in large, complex resid molecules (C₄₀+), followed by hydrogen addition to produce lower-boiling products, such as naphtha, diesel, and vac- uum gas oil (VGO), along with an unconverted fraction. Figure 1 Number of resid hydrocracking units operating globally

EBRHC converts a significant portion of vacuum residue into valuable distillates, reducing

C-C bond cleavage primarily occurs via endothermic thermal cracking reactions. Temperature is the main driver of conversion, typically exceeding 400°C. Under these conditions, the thermal energy is sufficient for homolytic bond cleavage, generating free radicals. Highly aromatic radicals tend to recombine into larger aromatic struc- tures, promoting sediment formation and increasing the risk of coking. Hydrogen addition, in contrast, is catalytic and essential to the EBRHC process. It stabilises reactive low-value fuel oil production, with up to 90% (538+°C) conversion achievable

PTQ Q1 2026