PTQ Q4 2023 Issue

For inorganic contaminants, such as Si and P, guard bed catalysts are applied to break down the organic matrix and accommodate the inorganic component. In these materials, the balance between reactivity and accessibility is essential to minimise the slip of the components to downstream cat- alyst beds, achieve maximum uptake capacity, and protect the downstream catalysts along the cycle. For HDO, optimal selectivity is critical to minimise the for- mation of CO/CO 2 /CH 4 , which results in maximum hydro- carbon yields and a minimum inhibition effect on the HDS and HDN reactions. For organic contaminants, such as amides and unsaponi- fiables, the key is to apply catalysts with sufficient hydroge - nation activity while at the same time preventing undesired side reactions. Finally, the activity of the main hydroprocessing catalyst is important since a superior activity allows you to accom- plish the same activity within a smaller volume. In specific cases, by applying a bulk metal catalyst, reactor space can be created for a larger guard bed volume, allowing for the acceptance of a higher concentration of contaminants. A Gitte Nygaard, Senior Solution Specialist for Renewable Fuels, GTIN@topsoe.com and Federico Francisco Cristófoli, Sales Director, FFCR@topsoe.com, Topsoe A/S Renewable feedstocks are bringing a new set of contami- nants into the hydroprocessing units when co-processing. Although at first glance they look familiar, the renewable contaminants are placed in other chemical complexes and, therefore, require a different guard technology. Specialised renewable guard and grading catalysts for the pick-up of contaminants from renewable feedstocks have been developed over the last decade We need to distinguish between raw and pretreated feedstocks. Most raw renewable feedstocks come with vast amounts of contaminants. Therefore, these feeds need to undergo pretreatment to get the contaminants down to acceptable levels before hydroprocessing. Often, the renewable feedstocks will be a minor part of the feed blend, so it is more economically feasible for the refiner to buy already pretreated renewable feedstocks instead of investing in their own pretreatment facilities. Raw renewable feedstocks may also be unstable, so pretreat- ment outside the hydroprocessing unit and proper storage need to be ensured to prevent operational issues while processing. A comprehensive catalyst grading system is needed to handle these contaminants, as well as the well-known con- taminants in the fossil feedstocks. Specialised renewable

guard and grading catalysts for the pick-up of contami- nants from renewable feedstocks have been developed over the last decade. There are two major strategies for making the grading system in the industry as today. The first one is to try to pick up all contaminants with the same type of grading cata- lyst as in fossil service. This is beneficial for units with very little flexibility since this will require the smallest volume for grading, which is considered suitable when co-pro- cessing relatively small amounts of renewable feedstocks. The drawback is that these types of grading systems only provide a very limited opportunity for the refiner in terms of quantity of renewable feedstocks and feed flexibility. Furthermore, skimming during the cycle may be required to achieve the desired cycle length for the bulk catalyst. The second grading strategy is to apply a more complex grading system comprising of several specialised guards and grading catalysts. This system provides much larger feed flexibility for the refiner and can allow more renew - able feedstocks to be co-processed. This type of grading system will, however, require slightly more space in the reactor, where typically 20-50% more volume for grading is needed, depending on the desired feed flexibility and quantity of renewable feedstocks. This will, however, often eliminate the drawback of having to do a skimming during the cycle. One of the most challenging contaminants for conven- tional hydroprocessing catalysts is phosphorus, which is found in phospholipids in vegetable oils. Phospholipids react quickly at the top of the reactor, forming a crust that causes pressure drop and frequent shutdowns. Topsoe has developed a new series of catalysts specially designed to handle complex renewable molecules, such as phospholipids. One example is TK-3000 PhosTrap, a novel catalyst technology that can trap phosphorus deep inside the catalyst pellet, preventing crust formation and pressure drop. This catalyst can extend the cycle length and improve the performance of the hydroprocessing unit. Using selec- tive grading catalysts like TK-3000 PhosTrap is a simple and effective way to remove contaminants from renew- able feedstocks when co-processing them in conventional refineries. Q Where do you see refinery reactor and catalyst tech - nology advancing in tandem towards processing a wider variety of crude feedstocks and intermediates? A Scott Sayles, Becht Advisor, Becht, ssayles@becht. com Processing renewable feeds using hydroprocessing tech- nology requires the removal of contaminants using a PTU (see Question 4 ) and then further removal using a guard bed reactor. The guard bed reactor typically contains a bed (or beds) of catalyst to remove the remaining contaminates and then deoxygenation reactions to create the alkanes for further processing. The catalyst in each bed is specific to the functionality required to complete the reactions. Figure 1 shows the renewable feed processing steps. Of interest are the processing and treating steps in the process.

PTQ Q4 2023