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What is the latest progress in FCC catalysis to boost bottoms upgrading?

Mar-2022

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Tom Ventham, G. W. Aru, LLC and Unicat Catalyst Technologies, tom.ventham@gwaru.com

Refiners with FCC units consistently aim to maximise margins at high crude oil prices, and this has led to a renewed interest in bottoms upgrading. The catalytic technology to achieve this improvement is, however, basic and traditional. Bottoms upgrading additives are simple, high-matrix additives that crack long-chain paraffinic intermediates, that would otherwise become part of the slurry product yield, to boost yields of move valuable products. UMCB is much like other additives marketed for bottoms upgrading and also contains components to reduce the effects of dilution when UMCB is used in high proportions in the FCC unit. It is being tested by major refining companies and is supported by the best-in-class technical team of FCC additives experts at G. W. Aru, LLC & Unicat. It is this ability to support a refiner around the use of this dynamically functioning FCC additive that is typically the differentiator to gaining the full improvements possible when deploying a bottoms upgrading strategy of this type. We encourage all refiners interested in this type of operation to explore all of these opportunities open to them.

Firstly, we must address how some refiners are looking to implement bottom upgrading additives to enhance margins. One benefit of improved margins is the ability to invest OPEX to further stretch profitability of the FCC. Some refiners have begun using, or increased their use of, ZSM-5 type additives (such as Ultra C3Booster or Ultra C4Booster from G. W. Aru, LLC & Unicat) to boost yields of valuable LPG olefins or economic drivers to enhance octane value of gasoline. Physical limitations moderating ZSM-5 use include wet gas compressor or gas plant hydraulic constraints. An economic pivot-point exists that can be modelled in LP software, steady-state simulation models, or simple yield calculations, which recommends a reduction in riser outlet temperature to decrease volume load to the gas concentration system to increase ZSM-5 use to produce a higher proportion of the most valuable molecules (propylene and butylene) more efficiently, and therefore more profitably, to fill that vacated space.

Downsides of a severity reduction include two areas of concern. The first most obvious is that main fractionator bottoms (also known as, slurry, DCO, CLO) yield will increase with a decrease in severity. The additive approach discussed in this question is the use of dynamic and flexible additions of bottoms upgrading additives (such as Ultra MCBuster “UMCB” from G. W. Aru, LLC & Unicat) to breakup supplementary bottoms production into more valuable products to maintain optimal product yields. The second concern that can be encountered is a reduction in riser-side severity leads to mirrored fall in regenerator temperature (at constant delta coke). At lower regenerator temperatures, kinetics of CO oxidation will be impacted and further promotion activity, in the form of a platinum or palladium containing CO promoter, will be needed to maintain control of unit afterburn as defined by the delta between dilute phase temperature and dense bed temperature. In FCC units limited by NOx emissions it may not be possible to increase use of CO promoter (particularly if the unit is operating at high rates meaning CO promoter additions are already forced higher). Furthermore, current high metal costs of platinum and palladium mean there is also a cost implication to any increase in CO promoter use.

For refiners in this difficult situation, or indeed any refiners interested in unit optimisation, the patented (US Patent number 11,224,864) Great FCC Promoter (“GFP”) range of CO promoters from G. W. Aru, LLC & Unicat gives the option to switch to a lower precious metal content CO promoter that is proven to operate equally or more effectively compared to conventional CO promoters with much higher precious metals content. As a result of this lower precious metal loading, GFP is both lower cost and produces less NOx to give a more efficient and cost-effective afterburn control within NOx constraints when targeting operational modes such as this.

Mar-2022
Steven van Vegten, Albemarle, Steven.vanVegten@Albemarle.com

Bottoms upgrading capabilities are mainly determined by the catalyst’s accessibility, matrix activity level, and low coke selectivity. Two technological advances by Albemarle, Denali and RiFT, help refiners either minimise fuel oil production or seek additional bottoms upgrading capabilities, as we recognise feedstocks are becoming more difficult and grow in diversity.

Accessibility measures the ease of diffusion of high molecular weight feedstock to diffuse into the catalyst particle, reach active sites, and subsequently be cracked to more valuable products. Albemarle’s high accessibility catalyst technology delivers unhindered access to active sites, of which the active matrix plays a crucial role in bottoms upgrading. Albemarle’s latest RiFT matrix delivers enriched PoSD and supplementary acid sites, increasing total catalyst acidity by up to 20%, presenting favourable implications for bottoms cracking and hydrogen transfer.

Our next-generation USY zeolite technology, ZT-600, is a cutting-edge zeolite technology that provides multiple benefits and is employed in our Denali catalysts. One benefit is higher intrinsic zeolitic stability and retention, which provides a tool for extricating and controlling activity versus hydrogen transfer. In addition, acid sites have been optimised with less non-framework alumina for fewer undesired reactions, particularly lower coke and gas. Lastly, more mesoporosity has been incorporated to increase zeolitic contact with reactants and result in fewer secondary reactions owing to faster disengagement. Overall, Denali catalysts deliver improved yields, especially improved coke selectivity and more selective cracking of larger molecules to assist in bottoms cracking.

Mar-2022
Corbett Senter, BASF Refining Catalysts, james.senter@basf.com

Refiners are constantly challenged to maximise refining margin by converting heavier feed to lighter value-added molecules. FCC catalysts need to enable the FCC to have additional flexibility to further upgrade bottoms and overcome process constraints. This means a coke selective bottoms upgrading catalyst that maximises transportation fuels, especially for the resid market.

BASF is very active in developing new products that maximise bottoms upgrading in FCC units. We have seen multiple FCC trials of newer catalyst products, such as Boroflex, Fourte, and Luminate, which have improved bottoms upgrading compared to incumbent catalysts. BASF’s latest FCC catalyst product for maximum bottoms upgrading, Altrium, is designed to maximise the destruction of bottoms to more valuable FCC products. The product incorporates our Advanced Innovative Matrix (AIM) and the proven Improved Zeolite-Y (IZY) technology. The key features include higher meso-macro porosity for larger molecule diffusivity, deeper conversion, and improved metal passivation while having good attrition resistance to increase retention and reduce stack opacity and slurry fines.

Commercial trials of Altrium have confirmed its ability to deliver better economic performance through coke selectivity and deeper resid bottoms conversion. By improving the gasoline and distillate yields, we help refiners increase profitability. With FCC catalyst, there is no ‘one size fits all’ approach to improving bottoms upgrading. Refiners need to talk with their catalyst provider to determine which product best fits their objectives and constraints.

Mar-2022
Rainer Rakoczy, Clariant Catalysts, Rainer.Rakoczy@clariant.com

Today’s cocktail of catalysts is composed to react to the requirements driven by the feed to the FCC unit. The product mix leaving the unit has reached capabilities to provide outstanding flexibility. Until today, the produced middle distillate fraction, namely light cycle oil (LCO), can reach density levels that are sometimes hard to process in distillate hydrotreater towards ULSD specifications, especially if FCC operation and catalyst selection is selected to produce predominantly olefins-rich off-gas, with naphtha fractions providing high knock resistance. With the current need for co-processing of biogenic triglycerides from used cooking oil, fats from sewage, or vegetable oils, there is an option to expand the capability of handling high-density LCO. In addition, with more and more focus on fuel to chemicals FCC unit and the right catalyst selection helps to optimise light olefins yield in combination with naphtha, which can be utilised in a steam cracker after appropriate hydroprocessing. Clariant and its partners offer tailored catalytic solutions for optimised product recovery and hydrogen management to follow these new challenges.

Mar-2022
Heather Blair, Johnson Matthey, heather.blair@matthey.com

There are multiple catalytic options available for improving FCC bottoms upgrading, but one of the most effective methods of improving bottoms upgrading is using a separate particle additive. This gives the refiner ultimate flexibility to quickly change bottoms upgrading based on changing economics, feed, and/or unit constraints.

Johnson Matthey’s BCA-105 is a very effective bottoms cracking additive. The additive is made from highly selective matrix that provides the first cracking sites for larger FCC feed molecules. By doing this, the larger hydrocarbons (C20-C40) are cracked into smaller, more easily crackable hydrocarbons that can be further cracked on the Y-Zeolite of the FCC catalyst. This function allows lower Z/M base catalysts to continue cracking towards LCO, and higher Z/M base catalysts to convert towards gasoline and LPG. The additive can also be combined with ZSM-5 additives to increase LPG yield. Bottoms reduction of up to 25-30% is achievable using the additive.

The separate particle approach is more effective than simply adding extra matrix to the base catalyst. In FCC catalyst, zeolite coking is initially much faster than matrix. The coke precursors formed in Y-Zeolite migrate onto the matrix, therefore prematurely deactivating matrix cracking activity. In BCA-105 particles, the rate of matrix coking is much slower, resulting in higher matrix activity and more bottoms cracking. Also, metal dehydrogenation reactions occur relatively quickly, but the metals must first be reduced in the riser. BCA-105 enables cracking reactions to occur before metals being reduced, having a neutral and, in some cases, decrease in dry gas yield. Generally, when adding matrix to the base catalyst, it tends to make more hydrogen and coke due to the nickel and vanadium laydown on the base catalyst caused by the quick cracking reactions of the base catalyst Y-Zeolite. These metals then migrate to the base catalyst matrix. BCA-105 does not have the same effect as it does not contain any Y-Zeolite.

BCA-105 is an effective bottoms cracking additive that allows refiners flexibility without increasing coke or dry gas and impacting fluidisation. It is compatible with all FCC unit designs and base catalyst technologies.

Mar-2022