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Apr-2021

What are the benefits of bulk metal catalyst in hydrotreating?

Responses to a question in the Catalysis 2021 Q&A feature

Various from Advanced Refining Technologies, Chevron Lummus Global, Catalyst Intelligence, Haldor Topsoe, Honeywell UOP & MERYT Catalysts & Innovation.

Viewed : 224


Article Summary

Bi-Zeng Zhan, Hydrocracking R&D Manager, Advanced Refining Technologies (ART) - bize@chevron.com; Theo Maesen, Director R&D, Chevron Lummus Global - TMaesen@chevron.com.

Self-supported catalysts, sometimes branded as ‘bulk catalysts’, pack high hydrogenation activity into a small reactor volume. The superior hydrogenation activity of self-supported catalysts (as compared to alumina-supported catalysts) can enhance refinery margins by increasing a refinery’s flexibility to process recalcitrant (for instance, resid-derived) feedstocks and extend run length.

In the past decades, applications of self-supported hydroprocessing catalysts started in diesel hydrotreating to increase diesel volume swell. More recently, self-supported catalysts have expanded into hydrocracking applications to make more or better chemicals, fuels, and lubes. In addition, the superior hydrogenation activity of self-supported catalysts enables better and flexible integration of varying refinery processes, resulting in improved capital efficiency.

As with supported catalysts, there are many different self-supported catalysts, each with their unique chemical compositions, acid site densities, and pore size distributions. Through its enhanced hydrogenation ability and its carefully tuned pore structure, ART’s self-supported ICR 1000 catalyst platform has debottlenecked refineries and hydrocrackers by enabling higher conversion of vacuum gasoils (lower bleed rates), by enabling conversion of opportunity or synthetic gasoils, and by enabling extension of hydrocracker run lengths. In addition, through its tailored acidity, ART’s self-supported ICR 1000 catalyst family has debottlenecked hydrotreaters by improving the quality and value of base oil, improving the quality of steam cracker feedstocks, enabling the simplification of white oil production, and increasing diesel production volumes.

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Carl van der Grift, Director, Catalyst Intelligence - vandergrift@catalyst-intelligence.com
Bulk metal catalysts (BMC) have a very high hydrogenation volume activity and their use under optimised operating conditions can result in unique unit performance not attainable with alumina-supported catalysts. The high hydrogenation activity is explained by the larger number of active sites as well as the higher intrinsic activity of these catalytic sites. This high hydrogenation activity is best deployed in the bottom of the reactor to remove the most difficult nitrogen and sulphur species and for deep saturation of aromatics. BMCs are used to alleviate conversion constraints in existing hydrotreating or hydrocracking units to avoid the installation of extra reactor volume (capex). The extra hydrogenation activity in the unit can be used to process a higher intake of distressed feedstocks or to extend the cycle length at constant throughput and feed quality. In hydrocracking units, the BMC can be used to achieve high HDN and HDA in the pretreater and thus improve the performance (selectivity, cycle length) of the hydrocracking catalyst. The capability to process distressed feedstock into high value products usually provides a good incentive for the use of BMC. Some disadvantages of bulk metal catalysts may be: (i) the relatively high purchase price, (ii) the long lead time for fresh catalysts, (iii) the single-cycle use as they cannot be regenerated/reactivated, and (iv) the loss of metal value as recovery of the metals is complicated when bulk metal catalysts are not kept separate from supported catalysts during unloading, such as during gravity unloading of a stacked bed. The loading diagram needs to be designed by the catalyst supplier. The catalyst supplier knows which operating conditions in the reactor are necessary for the BMC to show its high activity over the cycle. The increased bulk density of the catalysts versus supported catalysts also requires a calculation by the unit licensor to check whether the reactor support can handle the increased weight of the catalyst load.

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Meritxell Vila, General Manager, MERYT Catalysts & Innovation - mvila@meryt-chemical.com

The great benefit of a bulk metal catalyst is that the support part of the catalyst, which is not catalytically active, is not present, therefore the volumetric activity is extraordinarily higher compared with a supported catalyst.

This higher activity allows one to process more difficult feeds, to increase the flow rate of the unit, or to extend the cycle length.

The question is that the unit must be carefully studied and adapted to work with this kind of catalyst which has a very high density and will require high hydrogen consumption. As a consequence, compressors must be modified accordingly. Also, the temperature reactor profile will change due to the high exothermicity of the reactions, and hydrogen quenches should also be adapted. These effects can be minimised by installing only one bed or two of bulk metal combined with beds of traditional supported catalysts.

But it seems that the tendency for hydrotreating catalyst next generations will be to become bulk metal catalysts, in order to maximise their activity as much as possible.

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Steven Zink, Principal R&D Engineer/Scientist, Honeywell UOP - Steven.Zink@honeywell.com
The benefits of bulk metal catalysts in hydrotreating are determined by their degree of success to achieve certain, economics-driven objectives. Bulk metal catalysts, known for their superior hydrogenation activity, have enabled some refiners to produce ULSD with assets that would otherwise have been unable to produce ULSD, avoiding the capital expense of reactor addition or the requirement for an extra turnaround or reload. They have allowed some refiners to process a wider array of price-advantaged feedstocks, also without requiring an extra turnaround or reload. Where hydrogen is relatively cheap, refiners make use of bulk metal catalysts with price-advantaged, hydrogen-deficient feedstocks (for instance, light cycle oil) to maximise volume swell and cetane, toward greater ULSD volume production and for improved yields of light and heavy distillates from hydrocracking conducted downstream. Bulk metal catalysts may likewise be applied to improve hydrocracking yields of relatively high viscosity index base oils, due to the superior aromatics hydrogenation activity.

On the other hand, bulk metal catalysts may not be particularly advantageous from the perspective of a refiner with no access or otherwise very limited access to hydrogen-deficient, price-advantaged feeds and with hydrotreating capacity and capability to achieve near-maximum volume swell with conventional, supported catalysts in any typical cycle.

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Per Zeuthen, Senior Director Europe, Haldor Topsoe - pz@topsoe.com
In the past, some bulk hydroprocessing catalysts were well known for their high activities. However, the bulk catalysts are very expensive – and they are known for being non-regenerable.

Haldor Topsoe has recently developed a supported catalyst with very high activity which outperforms the unsupported catalysts. This new catalyst, TK-6001 HySwell, has an improved performance stability and is equally or even more active and regenerable than unsupported catalysts. In other words, there are really no benefits of using bulk metal catalysts in hydrotreating.


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