Apr-2024

Catalyst rejuvenation offers circular solution for hydroprocessing catalysts

Recover the full activity of spent hydrotreating catalyst to ensure their reuse without performance loss.

Jignesh Fifadara and Madeline Green
Evonik

Article Summary

Today’s refiners face the daunting task of transforming an ever-changing crude slate into a wide range of marketable products. With a continuous emphasis on profitability under increasingly stringent environmental regulations, the most advantageous path is not always clear.

Surging energy costs and pressure to reduce environmental footprints have thrust the industry into the limelight, compelling a comprehensive overhaul and revitalisation of its operations to reduce waste, cut pollution, and minimise impact on the environment.

Alongside the transition to greener, more sustainable manufacturing processes, refiners are contending with seemingly relentless cost increases. These external factors have placed further pressure on businesses to find economically efficient and sustainable methods to complete their operations without compromising performance or safety levels. Here lies the million-dollar question – how do you reduce operating costs and carbon emissions without sacrificing performance?

One proposed solution is catalyst regeneration and rejuvenation, which can combine performance and cost savings while potentially supporting circularity and sustainability goals by minimising environmental impact and reducing waste.

Circular approach
Historically, a linear model has been the norm, whereby raw materials are collected, turned into products – hydrotreating catalysts, for example – and then disposed of as waste. However, this approach has its downsides. First, there is the economic cost to the refinery – disposal of a catalyst can be expensive – followed by the additional cost of procuring a fresh catalyst to replace it. Then there is the environmental impact: more landfill waste and further depletion of resources to create new catalysts.

A more ‘circular’ approach offers a clear path towards better profitability, competitiveness, and a reduced environmental footprint. Sustainable catalyst processes such as catalyst rejuvenation, which focuses on reusing a catalyst after its lifecycle, pose a viable solution for those looking to steer operations away from wasteful practices. Benefits include minimised waste, lower greenhouse gas (GHG) emissions, and optimised raw material usage, as well as improved supply security, lower costs, better margins, and a boost to economic growth.

Regenerate and rejuvenate
So that is the ‘why’; now let us look at the ‘how’. Take Evonik’s proprietary Excel rejuvenation technology, which recovers the full activity of spent hydrotreating catalysts, including the highly active Type II, ensuring their reuse in refining hydrotreating applications without the loss of unit performance. The process consists of multiple steps to maximise activity recovery and restore performance. These include:
• Catalyst analysis/qualification, whereby each batch undergoes thorough scrutiny and analysis.
• Regeneration, which requires the optimal temperature to recover activity without causing damage to the catalyst.
• Rejuvenation, a chemical treatment process to recover the original surface area, redisperse metals, and restore active sites for maximum activity.

The technology is relevant to downstream oil refining, particularly in hydrotreating applications including, but not limited to, naphtha, kerosene, gasoline, ultra low-sulphur diesel (ULSD), gasoil, and hydrocracker pretreaters.

When it comes to hydrotreating, catalysts are currently replaced in reactors after an interval of six months to four years or more, depending on feed severity and application type. During a cycle, the catalyst experiences coke and sulphur accumulation, obstructing active sites and serving as the main cause of the catalyst’s deactivation.

Active metals also agglomerate, reducing the availability of active sites and thus impeding catalyst activity. These two deactivation methods are reversible through regeneration and rejuvenation processes, which can restore activity nearly equal to that of fresh catalysts. The third method of deactivation involves contamination by metals in the feed, which can poison the catalyst and lead to an irreversible loss of activity.

A key point to note about catalyst regeneration and rejuvenation technology is that only the highest quality catalysts are eligible for reuse applications. They must meet strict chemical and physical specifications. As mentioned, metal contaminants such as silicon, vanadium, and sodium (among many others) lead to irreversible deactivation. Poisoned catalysts are not well suited for reuse in refining applications.

The chemical make-up is closely analysed on discrete portions of each batch of catalyst to ensure only ’clean’, uncontaminated catalysts are approved to be regenerated and rejuvenated for reuse. The physical specifications are also analysed to ensure the catalyst has not been damaged during the hydrotreating cycle by evaluating parameters such as surface area, pore volume, and crush strength.
Since the catalyst also goes through multiple additional handling steps, length and attrition are closely monitored to eliminate pressure drop concerns when reusing the catalyst in hydrotreating applications. Once the catalyst is verified to be free from contaminants and meets the bespoke physical property specifications, it is ready to undergo the first step of regeneration.

The chemical make-up is closely analysed on discrete portions of each batch of catalyst to ensure only ’clean’, uncontaminated catalysts are approved to be regenerated and rejuvenated for reuse. The physical specifications are also analysed to ensure the catalyst has not been damaged during the hydrotreating cycle by evaluating parameters such as surface area, pore volume, and crush strength.
Since the catalyst also goes through multiple additional handling steps, length and attrition are closely monitored to eliminate pressure drop concerns when reusing the catalyst in hydrotreating applications. Once the catalyst is verified to be free from contaminants and meets the bespoke physical property specifications, it is ready to undergo the first step of regeneration.

The process
The regeneration process is a combustion reaction that removes carbon and sulphur to restore some catalyst activity. Evonik’s technology utilises a moving belt (see Figure 2), a gentle process that minimises attrition, maximises yield, and maintains the physical properties of the catalyst. Additionally, the process integrates precise temperature control to ensure a uniform regeneration without hot spots or overheating of the catalyst. With this process alone, around 65-85% of the original activity can be restored, depending on the original catalyst type.

If further activity recovery is required, the catalyst proceeds to a second step, where Excel rejuvenation is introduced. In this phase, the catalyst undergoes a proprietary chemical treatment process to redisperse the active metals that have agglomerated across the catalyst substrate. This efficient redispersion of metals restores catalyst activity to its original fresh state.