that is custom tailored for demanding service at low and medium pressures. While the acid sites give 430DX better performance for both HDS and HDN activity, they are not strong enough to initiate any cracking reactions under typi- cal hydrotreating conditions. Figure 2 compares the line of ULSD catalysts from ART Hydroprocessing. 430DX can be coupled with the new 550DX (NiMo) cata- lyst within the proprietary SmART Catalyst System. This method fully utilises existing assets within a refinery’s indi - vidual constraints. Figure 3 shows how catalyst selection and placement can be tailored to provide the optimum bal- ance of maximum HDS and hydrogen consumption. A Steve DeLude, Becht Advisor, sdelude@becht. com, Jeff Johns, Becht Advisor, jjohns@becht.com, Jeff Kaufman, Becht Advisor, jkaufman@becht.com Catalyst activity improvements over the years have allowed operators to pursue various options to improve profitability and operating flexibility. While increasing cycle length and reducing the annualised shutdown cost can be significant, most refiners find that increasing throughput (debottle - necking), processing more difficult feedstocks, changing feed fraction cutpoints (yield optimisation), modifying operation to improve blending flexibility (improved product quality through higher hydrogenation), and/or higher vol- ume yields offer better overall value than simply pursuing a long cycle length strategy. Catalyst vendors have pursued multi-catalyst systems and new modelling techniques to tailor catalyst loads to specific refinery objectives. This situation makes it very important for the refiner to discuss in detail with potential catalyst suppliers their preferred operating strategy, feed options, and product quality improvement opportunities when considering their next reactor catalyst load. A Andrew Layton, Principal Consultant, KBC, andrew. layton@kbc.global CoMo catalyst was the typical distillate catalyst with high HDS but has improved in terms of available active sites and better surface areas contacting through Type II and equiva- lent catalyst active area changes. In many cases, these catalyst types also minimise H 2 consumption. To process feeds high in N 2 and boost cetane and cloud point, different catalysts became more important. NiMo catalysts improve Arosat (aromatics saturation) and HDN (most important in high N 2 ), cracked and heavier feeds with additional Type II metals/base interaction. NiMo HDS/ HDN reactions occur more through ring saturation than CoMo catalysts. Sometimes NiCoMo catalysts are a better fit. Improvements in catalyst ex-situ regeneration have enabled better catalyst re-use without sacrificing activity, even for Type II catalysts. While massive metal catalysts for high Arosat and HDS have a higher cost and higher H 2 consumption, these catalysts deliver a large increase in potential activity and aromatic saturation capability. This type of catalyst can be considered when a sufficiently high partial pressure of hydrogen is available and for some lubes operations.
Providing the reactor design is flexible enough to con - trol bed temperatures adequately, isomerisation catalysts are now used in the bottoms beds to improve cold flow properties. The cloud reduction/isomerisation catalysts are also improving to reduce yield loss resulting from cracking reactions. Most vendors offer tailored solutions, though massive metal catalysts currently have limited suppliers. Each round of development affects the relative catalyst ranking. Thus, the catalyst selection should not be based on one vendor for too long without comparing catalysts from multiple vendors. Note that maximising cycle length may now conflict with minimising energy use and carbon emissions as longer run length can mean more fouling, require high-pressure operations, and increase compression costs. Thus, opti- mum cycle length should be re-evaluated for both new and existing units. A Peter Andreas Nymann, Senior Solution Specialist, Topsoe, PAN@topsoe.com Higher activity catalysts like HyBRIM and HySWELL not only improve HDS activity but also improve the removal of nitrogen-containing hydrocarbons and the saturation of aro- matic components.* The higher HDN and HDA activity leads to lower product density (higher API), which leads to better cetane index and greater volume yields. The higher degree of aromatic saturation also provides additional end-point reduction, enabling the processing of higher boiling material in diesel hydrotreaters while still meeting the T95 specifi - cations. Higher activity may also facilitate the upgrading of lower-value streams like LCO and CGO in hydrotreaters to produce high-quality diesel. Higher saturation of aromatics and removal of nitrogen in FCC feed pretreaters improve FCC yields and product quality or alternatively enable co- feeding of lower quality feeds in the FCC. *Note: HyBRIM and HySWELL are marks of Topsoe. Q Besides improved catalyst systems, what advances in reactor internals are improving efficiency and throughput while also mitigating the effect of fouling and catalyst poisons? A Dinesh-Kumar Khosla, Global Market Manager Heavy Ends, HDC, Axens, dinesh-Kumar.khosla@axens.net Finding the right combination of catalyst and reactor inter- nals is essential for reliable and profitable reactor operation. In units featuring fixed-bed reactors, along with optimum catalyst design, overall reactor/catalyst performance can be enhanced by using high-efficiency reactor internals. Axens’ proprietary EquiFlow reactor internals ensure a uniform gas/liquid distribution and optimum mixing in the reactor, thereby minimising channelling and hot spots to ensure optimal use of the entire catalyst inventory in the reactor. This enhances catalyst activity, selectivity, and stability, and minimises catalyst changeout frequency while ensuring safe and reliable operation. EquiFlow distributor trays employ a dispersive system
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Catalysis 2023
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