Catalysis 2023 Issue

reactor internals will, in this connection, contribute rela- tively more to the combined reactor performance. In recent years, some focus areas have targeted renewable feeds fouling and coking potential as well as dealt with the high exotherms. It was necessary to rethink some of the other- wise very successful features used in the ULSD wave and fossil feed processing in general. Q What hydrocracking reactor catalysts are demon- strating optimal mid-distillate selectivity, better yield structures, and more efficient use of hydrogen? In combi - nation, which of these catalyst systems seems to be the most flexible in adjusting to feed quality variations and heavy feeds such as DAO and HVGO molecules? A David T. Dang, Senior Proposal Engineer, ART Hydroprocessing, David.dang@chevron.com Generally, hydrocracking catalysts with low zeolite con- tent are selected for maximum mid-distillate selectiv- ity. However, an integrated catalyst system with both hydrotreating and hydrocracking catalyst is required to achieve optimum catalyst activity and product selectiv- ity in a hydrocracking unit. The catalyst system should be customised for each customer unit to achieve the desired product yields and properties. Considerations for the optimum catalyst system include: • Hydrotreating catalyst is used to remove most feed con- taminants, such as metals, sulphur and nitrogen, and to condition the feed (pretreating) for hydrocracking • A layered hydrocracking catalyst system (such as hydro- cracking catalysts with different zeolite contents) can be used to optimise reaction zones for maximising mid-distil- late yield, minimising naphtha yield and LPG make • The amount of hydrotreating and hydrocracking catalysts needed depends on several factors such as feed properties, conversion target, product yields, and product properties. In addition, hydrocracking catalyst selection depends on the configuration of the hydrocracking unit, such as single stage once through (SSOT), single stage recycle (SSREC), two stage recycle (TSREC), as well as the unit operating pressure. • For feed quality variations, specifically with heavy feeds such as DAO and HVGO, the hydrotreating catalyst should be carefully selected to address additional feed contami- nants and increased feed conditioning. Moreover, increased hydrocracking catalyst activity and stability should be con- sidered to address higher cracking severity and fouling tendency of heavy feeds to ensure cycle run length target. An integrated catalyst system with hydrotreating and hydrocracking catalyst is required to achieve optimum catalyst activity and product selectivity in a hydrocracking unit

We have developed and continue to expand a hydrotreat- ing and hydrocracking catalyst portfolio to cover a wide spectrum of feedstocks and targeted products from maxi- mum distillate to maximum naphtha for different hydro- cracking unit configurations at different operating pressures. This is important when successfully selecting the optimum integrated catalyst system for many middle distillates selec- tive hydrocracking units. Furthermore, leveraging advances in research and development (R&D) in residuum hydropro- cessing leads to production of excellent demetallisation catalysts, which have been incorporated into hydrocracking units to allow for processing feeds with significantly high metals such as DAO. A Steve DeLude, Becht Advisor, sdelude@becht.com, Jeff Kaufman, Becht Advisor, jkaufman@becht.com Becht’s SMEs are aware that many catalyst suppliers are developing catalysts focused on reduced gas make, higher selectivity to middle distillates, improved final product properties (such as cold flow and cetane), and/or improved hydrogen use efficiency. Catalyst optimisation becomes a greater challenge when also combined with processing more difficult heavier feedstocks such as DAOs and HVGO streams. With these heavy streams, the ability to maintain high catalyst activity for HDS, cold flow improvement, and/ or cetane boost may be compromised by catalyst poisoning, coke deposit formation, and pore mouth plugging. The refiner must work closely with the catalyst supplier to identify the best catalyst option (including multi-catalyst systems) for their unit and specific objectives while recog - nising feed variations and/or quality constraints. A Andrew Layton, Principal Consultant, KBC, Andrew. layton@kbc.global Typically, hydrocracking catalyst systems are a combination of catalyst types based on feed type, feed contamination, selectivity, conversion, and unit design. The unit designs vary, depending on the combination of 1-3 stages with or without bottom product recycling. The hydrocracking cata- lyst selection can target different products such as naphtha, distillate, lubes, or some level of aromatic saturation. Stage 1 reactors generally use varying levels of metal contaminant removal catalyst based on feed metal concen- tration levels. If necessary, they also use antifoulant grading catalyst/inerts that have high metal adsorption potentials, different grading sizes, and high surface areas. The next catalyst bed typically consists of varying amounts of NiMo or NiCoMo catalyst. The NiMo catalyst is designed to sufficiently remove N2 to avoid impacting the performance of hydrocracking cata- lysts downstream. NiMo also improves aromatic saturation with HDS following more the ring saturation route. Units which require /prefer higher aromatic saturation sometimes used NiW but now also have a choice to use varying quan- tities of massive metal catalysts, which some vendors carry. These catalysts also require a minimum concentration of H 2 pp to be effective and consume more H 2 . Stage 2 reactors, or downstream beds, contain most of the cracking catalyst. The number of stages is determined

Catalysis 2023