Catalysis 2023 Issue

this, the complete characterisation of feeds and products in a hydrotreating process, including aromatics content, is very important. Most importantly, aromatics content is an indirect indicator of cetane number and product density, the most prevalent constraints when processing LCO. Figure 7 shows a comparison of the trends of the total aromatics content measured on the liquid product for the different feeds and catalysts evaluated in the test. In gen- eral, the total aromatics content in the product increased with the amount of LCO blended into the feed and decreased when operating at higher conversions/higher hydrogen consumption. In the same way, the 100% NiMo scheme produced the highest conversion level of aromatics (higher hydrogena- tion activity), yielding the highest degree of cetane number uplift at the expense of higher hydrogen consumption. In contrast, the 100% CoMo extreme produced the lowest aromatics saturation, hence the lowest cetane number improvement. In general, LCO hydrotreating is a less efficient way of improving cetane number compared with LCO hydro- cracking for the same amount of hydrogen consumed. As such, the degree of aromatic saturation should be bal- anced and optimised by the principle of catalyst rationing and stacking, as earlier explained, with careful consider- ation of the maximum LCO blending ratio. The maximum practical blending ratio of 30% is a practical upper limit for conventional diesel hydrotreating, with typically a 2-10 cetane number improvement to meet modern road diesel standards. As suggested, the LCO blending percentage should be limited to approximately 30% for this hydrotreater to ensure the aromatics content is not greater than 35%, which corresponds to a minimum cetane index of 46 (with a potential 5 cetane number upgrading by using cetane improver. 1 ) When the NiMo/CoMo scheme was evaluated for this LCO blending ratio, the total aromatics was 33%. Although the aromatic content of CoMo/NiMo/CoMo is not presented here (see Figure 8 ), it should be lower than that of the NiMo/CoMo scheme (33 wt%), with only a 5% increase in hydrogen consumption. Using CoMo alone would not comply with this aromatics limit, while a 100% NiMo scheme could result in excessive hydrogen consumption (almost a 30% increase compared with NiMo/CoMo and CoMo/NiMo/CoMo). From a product density perspective, the LCO blend- ing limit becomes even more stringent to comply with the maximum density allowed by the EU directive: 0.845 g/ml. 4 According to Figure 7, the LCO blending limit is approxi- mately 15% for every catalyst loading scheme involved in this experiment. It must be noted that around 20% LCO blending percentage can also be achieved in terms of prod- uct density by extrapolation but limits the viable options to NiMo, NiMo/CoMo, and NiMo/CoMo/NiMo. These results again suggest the need to optimise the CoMo/NiMo ratio and positioning for optimum perfor- mance of hydrogen-constrained hydrotreaters, as sug- gested by catalyst suppliers. For a hydrogen-constrained hydrotreater, the use of CoMo/NiMo/CoMo scheme is

highly recommended as a reconciliation between hydro- gen consumption, catalyst activity, and product qualities by employing the right catalyst for the right objective at the right location in the hydrotreating reactor. If the refiner is looking to process a higher blending ratio, LCO hydrocracking is optimally recommended to efficiently boost the cetane number by naphthene ring opening. All the results presented in Figure 5 (hydrogen consumption), Figure 7 (aromatics content), and Figure 8 (product den- sity) are consistent and aligned with expected trends. This complete set of results confirms the quality of the data pro - duced during the test and the high accuracy of the experi- mental setup used. Key takeaway Refiners should carefully evaluate the options for LCO upgrading to ensure a good balance of cycle length, hydro- gen consumption, and product qualities. Independent cata- lyst testing is proven to be an effective tool for providing refiners with confidence in selecting the final solution, as demonstrated in this study.

Flowrence is a mark from Avantium.

Acknowledgements Theo Groen and Driss Boublali – Operations; Thomas Oosterhoff and Nicholas Roffrey – Catalyst loading and lab testing; Imko Juffermans and Daniel Banen – Analytics. References 1 Sharafutdinov, I., Stratiev, D., Shishkova, I., Dinkov, R., Pavlova, A., Petkov, P., Rudnev, N., Dependence of Cetane Index on Aromatic Con- tent in Diesel Fuels, Oil Gas European Magazine, 38(3), Sept 2012, 148-152. 2 Ortega C., D. O.-J. Can. J. of Chem. Eng., 99, 2021, 1288-1306. 3 Meneses-Ruiz, E., Escobar, J., Juventino Mora, R., Ascención Mon- toya, J., Barrera, M. C., Solís-Casados, D., Escobar-Alarcón, L., Del Ángel, P., Laredo, G., Nitrogen compounds removal from oil-derived middle distillates by MIL-101(Cr) and its impact on ULSD production by hydrotreating, Oil & Gas Science and Technology - Revue de l IFP, 76(1), Jan 2021, 56. 4 EU: Fuels: Diesel and Gasoline, TransportPolicy.net, www.transport- policy.net/standard/eu-fuels-diesel-and-gasoline Tiago Vilela is Director Refinery Catalyst Testing at Avantium, ac - countable for the overall performance of the business line. He has more than 20 years’ experience in engineering, project management, management consultancy, and business development. He holds an MSc degree in chemical engineering from the University of Aveiro, Portugal, and a Professional Doctorate in engineering from Delft Uni- versity of Technology, The Netherlands. Email: Tiago.Vilela@avantium.com Nattapong Pongboot is a Project Manager in the Refinery Catalyst Testing group at Avantium, delivering high-quality catalyst testing services for customers worldwide. He has hands-on experience in re- fining and petrochemical technologies as both a licensor and refiner. He holds an M.Eng. degree in chemical engineering from Kasetsart University. Email: Nattapong.Pongboot@avantium.com

Catalysis 2023