Zero and low rare earth FCC catalysts
Blends of rare earth-free and rare earth-based catalysts for resid feed FCC applications have maintained and even improved performance
Colin Baillie and Rosann Schiller, Grace Davison
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Catalysts are generally a refinery’s second highest raw material cost after crude oil. It is therefore not surprising that, due to the skyrocketing cost of rare earth metals (a key component of FCC catalysts), refiners are increasingly asking catalyst suppliers to relieve their cost pressures while maintaining or even improving product performance. Grace Davison Refining Technologies responded to the issues of rare earth price and availability by developing the REpLaCeR family of zero and low rare earth FCC catalysts. This new series includes eight new catalysts for both hydrotreated and resid feed processing with zero and low rare earth content, and their successful commercialisation will be duly discussed.
Increasing price and decreasing availability of rare earths
The problem of increasing price and decreasing availability of rare earths is not only limited to the refining industry. These highly sought after metals are also key raw materials for many strategic industries, with applications ranging from military devices to electronic components. In addition, they are essential constituents in newly evolving green technologies, such as hybrid cars and wind turbines. Their decreasing availability is primarily due to the fact that the world’s supply only comes from a few sources, with China alone currently accounting for 95% of the world’s rare earth metal output. During the last decade, exports of rare earth from China have decreased significantly from approximately 57 000 MT/year in 2006 to less than 25 000 MT/year in 2010.1 This year, the export quotas for rare earths are similar to 2010 levels; however, more materials fall under the quota system, therefore the total amount of rare earth exported will be less than in prior years. This reduction in export quotas has caused the price of rare earth to rise rapidly.
The key index for FCC catalysts is the cost of 99% lanthanum oxide FOB from China, which has increased dramatically from $2300/t in January 2007 to more than $100 000/t in August 2011 according to the Asian Metals Index. Rare earth prices show no signs of decreasing to historical levels, highlighting the huge importance of zero and low rare earth FCC catalysts that are capable of providing, or even increasing, the performance of their rare earth counterparts.
Role of rare earths in FCC catalysts
Lanthanum and cerium are the two main rare earths used in FCC catalysts. These metals limit the extent to which zeolite dealumination occurs (thus stabilising the structure) under the conditions of the FCC unit. The aluminium atoms within the zeolite structure are the primary catalytic sites in FCC catalysts and therefore play an important role in providing activity and selectivity. For example, a higher amount of aluminium atoms will increase the amount of hydrogen transfer reactions that occur. Such reactions compete with cracking reactions and are important for preserving molecules in the gasoline range. Therefore, by restricting the loss of aluminium atoms in the zeolite, rare earth increases the activity and gasoline yield of FCC catalysts. Rare earth also plays an important role in preventing metals deactivation as it is a very effective vanadium trap. So, for resid processing, in particular, these rare earths play an important role in maintaining stability and activity.
Grace Davison’s prior development of FCC catalysts includes the addition of rare earth metals to stabilise the zeolite Y component of the FCC catalyst, a key development for catalytic cracking.1 Grace also has a history of developing rare earth-free FCC catalysts, including catalysts and zeolite components that enhanced gasoline octane in the 1980s and 1990s, delivering activity and stability without the use of rare earth. These rare earth-free zeolites were used in over 85% of catalysts supplied by the company in North America at the time. Later in the 1990s, Grace developed Z-21, a rare earth-free stabilised zeolite Y. Based on this technology, the Nexus catalyst family was commercialised in 1997, as a rare earth-free catalyst family for low-metal feed applications. Nexus has since been used in 10 applications. Grace Davison has now developed the REpLaCeR family of zero and low rare earth FCC catalysts, which are based on existing Z-21 zeolite technology, as well as the new Z-22 zeolite technology developed in 2010. Advanced methods are used to stabilise the rare earth-free Z-21 and Z-22 zeolites, involving proprietary stabilising compounds and manufacturing processes. FCC catalysts incorporating these new zeolites provide similar and even improved performance compared to rare earth-containing catalysts.
REpLaCeR zero rare earth FCC catalysts for hydrotreated and VGO applications include REsolution and Rebel based on the existing Z-21 zeolite, as well as REactoR and REplaceR based on the Z-22 zeolite. The development of rare earth-free catalysts for the resid feed sector is much more challenging due to the additional demands placed on zeolite stability. However, significant advancements have been made by applying processing technology involving metals resistance functionality to catalyst systems containing the Z-21 and Z-22 zeolites. This has resulted in the rare earth-free REduceR catalyst, which can be blended with rare earth-based resid FCC catalysts at levels up to 50%. This catalyst enables performance to be maintained or even improved in resid processing applications while significantly reducing the overall rare earth requirement and cost.
Commercial experience of zero rare earthcatalysts
Rare earth-free REsolution catalysts are based on the Z-21 zeolite and are intended for hydrotreated and VGO applications. Within the first six months of commercialisation, this catalyst has been successfully used in various refineries in the EMEA region. One such application is at a refinery in Central Europe. In February 2011, the refinery switched from a catalyst with 3.1 wt% rare earth to the rare earth-free catalyst. Figure 1 shows ACE pilot plant E-Cat testing to evaluate the performance of the catalyst at a 30% change-out. As can be seen, conversion, dry gas yield and bottoms upgrading were similar for the REsolution catalyst, while coke yield was lower. Table 2 shows a comparison of the product selectivities in more detail, where the increased LPG yields (at the expense of gasoline) can be attributed to the fact that more ZSM-5 additive was used during the period when the rare earth-free catalyst was used. The catalyst change-out has since reached over 75%, meaning the RE2O3 content of the E-Cat has been reduced from 3.1 wt% to 0.7 wt%, and the refinery is observing that performance is not only maintained using the rare earth-free catalyst, it is actually improved. To summarise, the refinery has observed similar bottoms upgrading and dry gas yield, as well as lower delta coke.
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