Mar-2012

Evaluation of a low rare earth resid FCC catalyst

A zero rare earth catalyst blended with a rare earth-based resid catalyst enabled a refinery to reduce its FCC catalyst rare earth requirement by 80%

SABEETH SRIKANTHARAJAH and COLIN BAILLIE, Grace Catalysts Technologies
BERNHARD ZAHNBRECHER and WIELAND WACHE, Bayernoil

Article Summary

Rare earth metals have played an important role in the refining industry since the 1970s, when it was discovered that they could be used to stabilise the zeolite-Y component of FCC catalysts to provide higher activity, as well as being used to influence product selectivity. Rare earth metals play an additional role in resid processing applications, as they have proven to be until now the most effective vanadium trap, helping to maintain stability and activity.

The two main rare earths used in FCC catalysts are lanthanum and cerium, and these metals have historically been readily available for under $5/kg. However, a reduction in Chinese export quotas resulted in rare earth prices rising dramatically in 2010, with the price of lanthanum reaching $140/kg around May 2011. Since then, rare earth prices have subsided somewhat, but remain significantly higher than historical levels.

The rare earth market is incredibly unpredictable and is expected to remain highly volatile. Against this backdrop of uncertainty with respect to availability and pricing, zero and low rare earth catalysts will continue to play an important role in the FCC industry. Grace Catalysts Technologies provides the REpLaCeR series, the first commercially successful zero and low rare earth FCC catalysts.

Zero and low rare earth FCC catalysts
Simply removing rare earth from an FCC catalyst would result in a considerable detrimental effect in most FCC operations due to the lower activity and worsening product yield slate obtained. To develop FCC catalysts containing lower rare earth content, it is necessary for alternative materials and processing techniques to be used that stabilise the zeolite component. Grace has considerable experience developing zero and low rare earth FCC catalysts. During the 1990s, it developed Z-21, a rare earth-free stabilised zeolite-Y, which was the basis for the Nexus catalyst family. This was commercialised in 1997 as a rare earth-free catalyst family for low-metal feed applications, and has since been successfully used in 10 applications.

In 2010, the company developed the REpLaCeR series of zero and low rare earth FCC catalysts, which are based on the existing Z-21 zeolite technology, as well as a new Z-22 zeolite technology. State-of-the-art methods are used to stabilise the rare earth-free Z-21 and Z-22 zeolites, involving proprietary stabilising compounds and unique manufacturing processes. FCC catalysts incorporating these new zeolites provide similar and even improved performance compared to conventional rare earth-containing catalysts. Based on the Z-21 and Z-22 technologies, the REpLaCeR series of zero rare earth catalysts for low-metal hydrotreating and VGO applications includes REsolution and REactoR, which are currently being used in more than 15 applications.

For resid applications, the development of rare earth-free catalysts is much more challenging due to the additional demands placed on zeolite stability. However, significant advances 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, thus reducing the overall rare earth requirement and the costs associated. There are currently 22 refineries using the REduceR catalyst, and typically they are applying a stepwise approach to implement the rare earth-free catalyst. Refiners are starting with a blending level of 30% REduceR catalyst and, upon confirming its performance, many are then moving to a blending level of 50%. Bayernoil is using the REduceR catalyst in both of its two FCC units with blending levels even higher than 50%.

Commercial experience of low rare earth resid catalysts
The Bayernoil Vohburg refinery is located in the Bavarian region of southern Germany and, along with the nearby Bayernoil Neustadt refinery, contributes to a total refining capacity of 10.3 million t/y. The two locations combined contain three crude units, two vacuum towers, two FCC units, one mild hydrocracker and hydrogen plant, one visbreaker, three reformers and one ether plant. The FCC unit at Vohburg is a UOP side-by-side model and was built in 1967. It is a resid unit with a typical throughput of 14 000 b/d, operates in deep partial burn and processes 80-90% atmospheric residue. The feedstock has a Conradson carbon content of 3 wt%, and the e-cat metals levels are approximately 4500 ppm vanadium, 3500 ppm nickel, 6000 ppm Fe and 5000 ppm sodium.

This Vohburg FCC unit was previously using a Nektor catalyst from Grace containing 3.1 wt% rare earth, which performed well. In April 2011, the refinery began to blend 30% of REduceR catalyst with the Nektor catalyst, with the simple objective of reducing rare earth while maintaining high performance. A certain misconception about rare earth-free catalysts is that they require higher catalyst additions, which has not been the case in any application of the REduceR catalyst. Figure 1 shows the catalyst addition rate and e-cat microactivity at Bayernoil Vohburg before and after using the 30% blend. It can be seen that good activity retention was achieved after the switch at a similar or even slightly lower catalyst addition rate, highlighting the high vanadium tolerance of the REduceR catalyst.

Figure 2 shows the e-cat coke and gas factors of Nektor and the 30% REduceR catalyst against nickel equivalents to compare nickel resistance. The 30% REduceR catalyst shows lower gas factors and similar coke factors, further demonstrating its suitability for high metal resid feeds. The FCC unit data provided in Figure 3 show that the REduceR catalyst blend provided improved bottoms conversion compared with the Nektor catalyst. In addition, a lower delta coke was obtained, which reduced the regenerator bed temperature by about 10°C. This allowed the refinery to achieve higher conversion at constant feed atmospheric residue content, or to process an increased amount of atmospheric residue at constant conversion.