Catalysis 2023 Issue

catalysis q&a

More answers to these questions can be found at www.digitalrefining.com/qanda

Q Maximising cycle duration of hydroprocessing units has always been important to refiners, but what other step-out gains can we see from catalyst developments in terms of volume swell, PNA saturation, and HDN activity while achieving high HDS performance? A Brian Watkins, Global Technology Manager, Advanced Refining Technologies LLC (ART), brian.watkins@grace. com ART’s DX catalyst series has been used in ULSD applica- tions for over 16 years, while ART’s 425DX catalyst contin- ues to be used worldwide for middle distillates. The recent addition of 430DX to this line of catalysts allows refiners to process tougher feeds, meet tighter specifications, improve product quality, and expand capacity with no additional capital costs. The 430DX catalyst is built on recent advancements in alumina technologies. Innovations in surface chemistry and new pore structures significantly boost HDS, HDN, and HDA activity, with improvements exceeding 15% in some applications. 430DX exhibits an optimised bimodal pore size distribution for high activity and sustained performance. 430DX offers improvement opportunities to every diesel hydrotreating unit. Its benefits have been demonstrated on both straight-run and cracked stocks and at low and high operating pressures. Figure 1 compares 430DX to its predecessor 425DX in an ULSD protocol using a feed con- taining 15% cracked stocks. 430DX shows a clear activity gain in the low-pressure ULSD test and further extends its advantage in the higher-pressure test. This increased activ- ity enables the refiner to exploit the additional activity by processing more opportunity feedstocks as well as increas- ing the relative cycle length of the hydrotreater. Researchers have previously identified surface acidity as a key property for improved catalytic performance. It is gen- erally accepted that there is a strong relationship between the role of increased surface acidity, increased pore volume and surface area to improve the reaction rate for reactions controlled through ring saturation, such as nitrogen and hard sulphur removal.

200

HDS HDN

175

150

125

100

AT405 CDXi

420DX

425DX

ICR316

430DX

Figure 2 ULSD catalysts from ART Hydroprocessing

Changes in surface acidity have also been shown to affect the interaction of active metals with the alumina surface during impregnation. This phenomenon has been exploited in the design of 430DX, as seen by the significant increase in HDN activity and by utilising the ART hydrocracker pretreat support tailored to ULSD service. This catalyst improves upon the legacy impregnation technology lever- aged in 425DX, whereby a chelate is used to bind to the cobalt ions in the impregnation solution and reduce inter- actions with the alumina support. The chelate/ion complex stays intact on the catalyst, which allows the molybdenum to sulphide at a lower temperature, promoting the forma- tion of Type II active sites. 430DX features an optimised loading of cobalt and tuned chelation to further enhance activity compared to 425DX. Combining a modified alumina carrier with improved surface acidity and a larger pore diameter gives a catalyst

Conditions: 1.0 LHSV, 600 PsiH & 2000 SCFB H/oil Feed: 30% FCCLCO with 28.7 API and 1.78 wt% sulphur

Conditions: 525psi, 1.05 LHSV, 2,000 SCFB Feed: 31.9 API, 1.41 wt% S, 440 wppm N

HDN

430DX 425DX

HDS

All CoMo

All NiMo

SmART systems

Temperature improvement, ˚F

Figure 1 Comparison of 430DX to its predecessor 425DX

Figure 3 Catalyst selection and placement can be tailored

Catalysis 2023