Lessons from FCC history: through Covid and post economic recovery
An updated and in-depth look at FCC catalyst history, spanning two decades, reveals trends pre-Covid, during Covid, and post the recent economic recovery.
Jacqueline Pope Bates, Melissa Clough Mastry and Alexis Shackleford
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A previous publication explored 15 years’ worth of fluid catalytic cracking (FCC) history.1 Today, we update this to include two decades worth of history, inclusive of the impacts during the Covid-19 pandemic and, more recently, during the economic recovery of 2022. The data explored span different regions of the world, catalyst suppliers, FCC designs, and types of FCC unit operations.
The current update reviews both catalyst properties and catalyst performance. Furthermore, regional trends within specific areas are explored. The regions are broken into three parts of the globe: The Americas (which includes North and South America), Asia (excluding China), and EMEA (Europe, Middle East, and Africa), which also includes the CIS (Commonwealth of Independent States). The global average in all cases is also presented. To further add context to the data, upper and lower bands are included as a shaded area, representing the 90th and 10th percentiles, respectively.
A significant catalyst parameter in Figure 1 shows how the global average rare earth oxide (REO) content has fluctuated greatly over the past two decades. REO stabilises the Y-zeolite, where high REO gives higher catalyst activity and selectivity to gasoline, and lower REO gives lower catalyst activity and higher light olefins such as propylene and higher gasoline octane. In 2011, there was a massive global shift to lower REO due to the REO crisis, in which the pricing of REO skyrocketed. REO levels slowly rebounded but never to the peak from previous years, largely due to product economics favouring a more moderate level.
Since 2017, we see a global trend towards decreasing REO content. This is due to product economics, suggesting that naphtha (a gasoline precursor) has slightly taken a back seat to other products, including LPG (liquefied petroleum gas). This is especially true in the Americas due to the drive from strong butylene pricing. The low REO trend was further exacerbated by the low gasoline demand during Covid years. Another interesting point this graph demonstrates is that all regions converged in terms of REO levels, rather than the trend over the first 15 years, with the Americas utilising higher REO catalysts than other regions.
Figure 2 gives insights into catalyst surface areas. To offset the activity loss due to lower REO, we see a global trend of higher total surface area (TSA). This trend is consistent over the entire 21-year history, with the most significant shifts happening at the same time REO drops are observed, i.e., during the REO crisis (2011) and since 2017. The higher catalyst surface area partially accommodates the loss in activity from lower REO. Higher surface area is achieved through several ways: higher fresh catalyst surface area, higher catalyst addition rate, and/or improved surface area retention.
An equally compelling trend emerging since our last analysis in 2015 is the zeolite-to-matrix ratio (Z/M) significantly decreased in all regions, favouring lower Z/M values. For such a drastic change, this requires not just one unit but entire regions to change their catalyst appetite. The Americas has seen the steepest curve, meaning its adoption of lower (lowest) Z/M ratio is the most drastic. This is likely due to two factors: matrix activity helps with LPG olefins generation (especially butylenes), and active matrix is very effective at bottoms cracking. The fact that bottoms is typically one of the least valued products from a refinery drives most refineries to minimise this product from the FCC unit. This change is also in favour of more LCO or diesel production, which currently is experiencing record-high prices.
The Ecat activity is a function of both rare earth and TSA (among other variables) and is shown in Figure 3. Ecat activity and all Ecat yields are measured using an ACE2 technology laboratory unit. This unit mimics a commercial FCC unit and is run at constant conditions, so any changes are due solely to the catalyst. Great fluctuations have been observed during the two-decade Ecat activity history. Most recently, a global trend favouring lower activity is observed, particularly during the Covid-19 pandemic (2020 and 2021) and has started to rebound during the economic recovery period (2022). Not only was total demand for refined products lower during the pandemic, but there was a shift in product mix.
With fewer passenger vehicles on the road, demand for gasoline was down, while diesel (needed to transport goods) and chemical precursors (such as propylene for manufacturing medical face masks and other polyolefin plastics as single-use material demand increased for sanitary reasons) were still needed. The low catalyst activity in 2020 and 2021 favours production of light cycle oil (LCO), a diesel precursor. This graph also shows that outside the Americas region, other regions run lower activity overall due to the higher demand for diesel over gasoline. Additionally, the Americas region processes, on average, lower contaminant feed (see Figure 4), which leads to higher activity needed to meet heat balance constraints.
Figure 4 shows common Ecat contaminant metals, a result of contaminants coming in with FCC feed. The two most prevalent contaminant metals include nickel and vanadium. Both have been on the downturn in recent years after reaching a peak in 2016. The global average today hovers around 3,000 ppm Ni+V. This suggests that global access to lower contaminant metal feeds has increased due to cleaner crudes (such as tight oils) and/or increased pretreating hydroprocessing capacity. Also noticeable is the lower 10% shaded area, which shows that the very low metals units have even lower metals today, likely due to more severe hydrotreating to meet increasingly stringent gasoline sulphur specifications.
Catalyst selectivities, which are impacted by contaminant metals, will be reviewed in the following discussion. Hydrogen yield is a function of the metals levels, which catalyse dehydrogenation reactions to produce hydrogen and coke. The hydrogen yield follows the metals (Ni+V) trend, as shown in Figure 5, peaking in 2016 and since has declined. Lower hydrogen levels are also influenced by catalyst metals passivation technologies. Hydrogen yields decrease as catalyst suppliers continue to innovate new and improved metals-tolerant catalysts.
Coke is a product with zero value but is also required to maintain the heat balance in the FCC unit and is impacted by contaminant levels coming from the FCC feed. Coke in the ACE reactor increases with higher activity and higher metals. Over the past 10 years, activity and metals were steady enough not to increase coke selectivity. We originally expected to see coke decline due to improvements in catalyst coke selectivity and metals tolerance technology; however, we found that coke selectivity has stayed relatively consistent. It is believed that the improved catalyst coke selectivity is offset by units needing higher coke selectivity due to processing cleaner feeds, such as tight oils or more severely hydrotreated feeds to meet gasoline sulphur regulations. We have seen more hydrotreating in recent years, especially in the Americas, due to sulphur regulations.
Ecat phosphorous, shown in Figure 6, is a marker for olefins additive, which converts gasoline range olefins into LPG (especially the olefinic products) and boosts gasoline octane. In the years since the last update, olefins additive levels increased significantly, especially in Asia with the highest curve/slope in this graph (Asia’s current level of phosphorous correlates to 5-9 wt% olefins additive in the unit). Despite the drastically different usage levels of additives in all three regions, every region experienced a significant increase.
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