PTQ Q1 2026 Issue

Impact of switching from a single to a dual catalyst system

Cat A

Cat B

Configuration VR feed rate

Single cat

Dual cat

Base Base Base Base Base Base Base

Base + 4.5% Base – 6.1% Base + 2.4% Base + 1.2% Base + 1% Base + 2.5°C Base – 18%

CAR

565+ conv.

HDMCR

HDS

Rx temp.

VTB sediment

Table 1

Conventional single catalyst system

ART d ual catalyst system

solubility to prevent sediment formation. Because the first- stage catalyst offers a higher metals tolerance, overall cat- alyst addition rates can be reduced without compromising performance, leading to significant cost savings for refiners. The following case study highlights a scenario where operational performance was constrained using a single catalyst system. The refiner had three primary objectives:  Increase crude flexibility to enable processing of more opportunity crudes with higher feed metal content. v Reduce unit fouling by lowering product sediment, thereby extending run length. w Increase conversion to maximise diesel yields and mini- mise bottoms production. To support the refiner’s objectives, a customised dual catalyst system was proposed, which was subsequently implemented in a trial. Table 1 summarises the key perfor- mance improvements observed when transitioning from a single to a dual catalyst system. The dual catalyst approach delivered a 4.5% increase in feed rate, 6.1% reduction in catalyst consumption, 2.4% increase in conversion, and an 18% reduction in sediment formation. In yet another example of successful application of dual catalyst technology, a refinery was able to significantly reduce its sediment in the product unconverted oil (UCO) stream through switching to the dual catalyst system. Transitioning to a dual catalyst system enabled the refiner to lower its UCO sediment content by ~50% at constant residue conversion (see Figure 4) . Lower product sediment resulted in lower fouling and an increase in cycle length for

Figure 3 ART’s dual catalyst system

Dual catalyst systems ART transformed the use of dual catalyst systems in RHC units, a result of extensive R&D efforts combined with deep operational experience across a range of commercial units. The dual catalyst concept outlined in Figure 3 is built on the understanding that each stage of the EBRHC process has distinct characteristics and requirements. By employing different catalyst functionalities in each stage, the system leverages catalyst synergies to maximise overall unit performance. There are two key feed-related factors that explain the effectiveness of the dual catalyst system:  Feed reactivity : The reactivity of the feed differs between stages. The first stage contains a higher proportion of rela - tively reactive molecules and fewer refractory compounds compared to the second stage. v Asphaltene solubility : Asphaltene solubility also changes between stages. Following hydrocracking in the first stage, asphaltenes remain moderately soluble in the oil. However, solubility decreases significantly after further conversion in the second stage. Accordingly, the first-stage catalyst is engineered for maximum metals removal, targeting contaminants such as nickel and vanadium. The second-stage catalyst is optimised for high activity in HDS, hydrodenitrogenation (HDN), and HDMCR, while also maintaining asphaltene

Single catalyst system

Dual catalyst system

Higher rate of fouling with single catalyst system

Residue conversion

VTB sediment

Cycle A

Cycle B

Cycle C

Fouling signicantly reduced with dual catalyst system

Cycle D

Time on stream

Figure 4 Impact of transition to dual catalyst system on product UCO sediment

Figure 5 Impact of transition to dual catalyst system on vessel fouling

PTQ Q1 2026