What hydrocracking reactor catalysts are demonstrating optimal mid-distillate selectivity, better yield structures, and more efficient use of hydrogen? In combination, 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?Mar-2023
Peter Andreas Nymann, Topsoe, PAN@topsoe.com
Topsoe’s proprietary D-Sel series has been selected as the best catalyst for maximum mid-distillate production based on pilot plant studies carried out by third-party pilot plant test facilities. The performance seen in the tests has been confirmed in several operating hydrocrackers around the world for several cycles.
Middle distillate has lower hydrogen content than lighter fractions and a high selectivity to middle distillates, therefore significantly contributing to more effective use of hydrogen. The ability of hydrocracking catalysts to provide optimal performance can be unlocked by applying the appropriate grading/HDM catalyst selection to help prevent contamination of poisonous components present in heavy fractions such as DAO and HVGO. The high-boiling materials are more refractive than lower-boiling feedstocks. They require high-activity pretreatment catalysts based on the proprietary HyBRIM or HySwell technology, where the HDN and hydrogenation activity has been optimised for heavy molecular hydrogenation.
Andrew Layton, KBC (A Yokogawa Company), Andrew.email@example.com
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 catalyst 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 concentration 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 catalysts 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 quantities of massive metal catalysts, which some vendors carry. These catalysts also require a minimum concentration of H2 pp to be effective and consume more H2.
Stage 2 reactors, or downstream beds, contain most of the cracking catalyst. The number of stages is determined both by feed type and necessary conversion level. High conversions tipping 75% and requiring high N2 feeds are likely to appear in Stage 2, at the very least.
Two types of cracking catalyst exist: amorphous silica alumina and alumina silica crystalline zeolites. Amorphous silica alumina shows lower cracking activity and targets more kero/diesel production. In comparison, alumina silica crystalline zeolites achieve higher activity and target more naphtha production. Thus, amorphous catalyst may predominate diesel maximisation as limited by achieving adequate activity.
The heavier feeds will always favour some type of NiMo catalysts in the lead beds, and a larger percentage of this ‘pretreat’ catalyst will be required as the feed gets heavier and higher in N2. If feeds are heavier than DAO/HVGO, both catalyst particle and pore size may increase, making fixed bed units unsuitable. After the interstage H2S/NH3 removal, a noble metal catalyst may be used for high-conversion naphtha production units during the downstream stage.
Several catalyst vendors offer a tailored combination of catalysts to meet conversion, selectivity, HDS, HDN, and Arosat needs while taking equipment design, H2 availability, and cycle length into account.
To differentiate between vendors and confirm their proposals, comparative data for catalyst systems can be requested. For example, H2 consumption data can vary widely. Alternately, pilot plant data compared to a reference catalyst may also be available if requested early enough.
Steve DeLude, Becht, firstname.lastname@example.org
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 recognising feed variations and/or quality constraints.
David T. Dang, ART Hydroprocessing, David.email@example.com
Generally, hydrocracking catalysts with low zeolite content are selected for maximum mid-distillate selectivity. However, an integrated catalyst system with both hydrotreating and hydrocracking catalyst is required to achieve optimum catalyst activity and product selectivity 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 contaminants, such as metals, sulphur and nitrogen, and to condition the feed (pretreating) for hydrocracking
• A layered hydrocracking catalyst system (such as hydrocracking catalysts with different zeolite contents) can be used to optimise reaction zones for maximising mid-distillate 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 contaminants and increased feed conditioning. Moreover, increased hydrocracking catalyst activity and stability should be considered to address higher cracking severity and fouling tendency of heavy feeds to ensure cycle run length target.
We have developed and continue to expand a hydrotreating and hydrocracking catalyst portfolio to cover a wide spectrum of feedstocks and targeted products from maximum distillate to maximum naphtha for different hydrocracking unit configurations at different operating pressures. This is important when successfully selecting the optimum integrated catalyst system for many middle distillates selective hydrocracking units. Furthermore, leveraging advances in research and development (R&D) in residuum hydroprocessing 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.