PTQ Q4 2025 Issue

and catalytic activity, which allows for deeper penetration of phosphorus into the trap’s inner volume. 4 Product yield loss is caused by the unselective removal of oxygen from fatty acids, leading to the formation of CO, CO₂, and CH₄, which subtracts carbon from the diesel pool. Operating conditions that favour the formation of CO, CO₂, and CH₄ include high temperature, low PPH₂, and high par - tial pressure of H₂S (PPH₂S). While these conditions often cannot be avoided during operation, HDO selectivity, and hence diesel yield, can be increased by applying a highly selective HDO catalyst at the reactor top, particularly to avoid the formation of CO, which inhibits the removal of sulphur, especially at low pressure when CoMo catalysts are applied.¹ Higher exotherm and H₂ consumption due to co-process - ing negatively affect the performance of the main HDS/N/A catalyst system as they increase WABT and lower PPH2 in the reactor. To achieve sufficient cycle length, it is essential to properly design the main hydrotreating catalyst system, according to the principles discussed earlier in this article. 1 While NiMo catalysts are in principle preferred because of their higher CO resistance, CoMo catalysts can better toler- ate low PPH2 and are preferred for lower pressure applica - tions, provided a proper HDO catalyst is installed, and CO formation is not too high. An additional challenge of co-processing is that renewa - ble feedstocks produce higher levels of n-paraffins, which raise the pour point and cloud point, worsening the cold flow properties of the product. A solution is undercutting the feed, losing heavy diesel to fluid catalytic cracking (FCC) and visbreaking. Alternatively, kerosene can be blended with the ULSD to meet cold flow specifications, alongside the use of expensive additives. These measures typically reduce profitability. An alternative catalytic solution to improve cold flow properties is to apply a dewaxing catalyst at the bottom of the hydrotreater, operating via cracking or isomerisation. Paraffin cracking has the advantage of requiring a smaller catalyst volume, leaving more room for the main hydro- treating catalyst. It is less sensitive to product nitrogen, providing more flexibility in the feedstock to treat and in the operating conditions. The disadvantage of cracking is that part of the diesel is converted to naphtha. Isomerisation, on the other hand, requires a larger catalyst volume and is more sensitive to nitrogen, but produces significantly less naphtha. In case an isomerisation catalyst is applied, the main catalyst sys- tem must be designed to minimise nitrogen slip to it. The best solution to address potential cold flow property issues depends on the specific operational goals, feedstock qual - ity, and economic considerations of the refinery. Catalyst advancements for co-processing renewables in distillate hydrotreating Ketjen’s 15 years of commercial experience in renewables hydrotreating includes 100% and co-processing applica- tions, treating a wide range of feedstocks.² , ³ , 4 In renewables co-processing specifically, more than 80 commercial cycles have been successfully completed upgrading vegetable oils, animal fats, and UCO.

Guard Traps particulates & poisons Removes Phosphorous & alkaline metals Controls polymerisation reactions Zone 1 Selectively converts Fatty acids to n-parans (HDO) (Traps slipped Phosphorous & alkaline metals) Removes easy S (DDS) Starts converting N & PNAs to Di-/Mono-Aromatics (HYD) Zone 2 (+ Zone 3) Removes N and hard S (HYD) Hydrogenates residual Aromatics (HYD) Dewaxing Improves Cold Flow properties (via Cracking or Isomerisation)

Log S, N

Guard ReNewFine™ 100 series

Zone 1

ReNewFine™ 200 series

Zone 2 (+ Zone 3)

Main hydrotreating catalyst

S < 10 ppm

Dewaxing catalyst

ReNewFine is a catalyst platform dedicated to renewa - bles hydrotreating. ReNewFine catalyst are well-proven drop-in solutions that do not require configuration or equip - ment changes. They are grouped into two catalyst series: ReNewFine 100 and 200. The ReNewFine 100 series includes hydrodemetallisation (HDM) catalysts, which are especially suited for trapping phosphorus and alkaline metals (Mg, K, Na, Ca). They help prevent pressure drop problems and reduce the deactivation of the main catalyst. The ReNewFine 200 series consists of grades with HDO as their main function, allowing for the removal of oxygen from fatty acids with minimal CO formation, thereby increasing cycle length and diesel yield. In a renewable feedstock co-processing hydrotreater, each zone, from the guard to the main catalyst sections, has a specific role and presents its own challenges. ReNewSTAX, a proprietary methodology for optimising catalyst loading design in distillate renewables co-processing, provides optimised stacking of catalysts to achieve maximum activ- ity, selectivity, and stability. Figure 8 illustrates the reactor zones and Ketjen’s catalyst loading strategy following the ReNewSTAX principles. A specialised ReNewFine catalyst system is installed at the reactor top to control pressure drop and maximise HDO activity, increasing renewable feed intake, diesel yield, and cycle length. The remaining loading consists of the main hydrotreating (HDS/N/A) catalyst system, which varies depending on specific feedstock, operating conditions, and cycle targets. The main hydrotreating catalyst system should be designed according to the principles discussed earlier in this article, including Part 1,¹ taking special care to manage potential inhibition by CO and pore blocking by bulky spe- cies in the renewable feed, and to minimise nitrogen slip in case dewaxing is necessary. The latter depends on the type of dewaxing catalyst applied. Table 3 lists the latest catalyst additions to the ReNewFine Figure 8 Reactor zones and catalyst loading strategy for a hydrotreater co-processing renewable feedstock

PTQ Q4 2025