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May-2015

GSR the only proven FCC catalysts and additives for gasoline sulphur reduction

Grace GSR® technologies: D-PriSM®, SuRCA®, and GSR® 5, are the result of nearly two decades of innovation. GSR has been used in over 100 FCC units worldwide, with and without hydrotreating hardware, to provide 20%-45% sulphur reduction in FCCU naphtha.

Colin Baillie
Grace Catalysts Technologies

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Article Summary

In-unit reduction of FCC gasoline sulphur with Grace’s patented GSR technologies continues to create a variety of opportunities and options for refiners to drive profitability. Grace GSR technologies create economic advantages around:
•    Improved feedstock flexibility
•    Reduced undercutting of FCC gasoline – increasing volume
•    Gasoline octane preservation – reduced gasoline post-treatment severity
•    Improved hydrotreater economics – lower operating severity
•    Temporary use during hydrotreater outages
•    Avoiding capital expenditure to meet upcoming Tier-3 regulations

There have been numerous case studies and references supporting the robust performance of GSR® technologies:
•    20-40% gasoline sulphur reduction
    •    All feed types
    •    All feed sulphur levels
    •    All based gasoline sulphur levels
•    Usage varying from 10% to 100% of circulating inventory

Sulphur Reduction Mechanism

Nearly all of the sulphur species in gasoline are thiophene-based molecules. The cracking catalyst component catalyses the hydrogen-transfer (HT) reactions between thiophenes and tetrahydrothiophenes (THT). GSR technology works by increasing the cracking of THT (which are Lewis bases) into hydrocarbons and hydrogen sulphide, as shown in the figure below.

Using a wide range of spectroscopic and other scientific techniques, it has been proposed that the mechanism involves both Lewis acid and basic oxygen site pairs. The Lewis acid site selectively adsorbs the Lewis base sulphur of the THT molecule. The basic sites promote the abstraction of protons to catalyse the cracking of THT to butadiene and hydrogen sulphide. The proposed mechanism accounts for high selectivity for THT cracking due to the balance of surface acid-base properties.
 
D-PriSM Additive: Description
The D-PriSM additive is effective for reducing light to intermediate gasoline sulphur species. The additive usually replaces between 8-15% of catalyst addition rate, with no FCCU yield deterioration observed. Sulphur reduction of between 20-35% in the light-to-intermediate gasoline cut is typically achieved commercially. The D-PriSM additive can be used in partial or full-burn operations

D-PriSM Additive: Commercial Experience of Increasing Gasoline Volume
Figure 1 illustrates the performance of the D-PriSM additive in a commercial FCC unit. Gasoline sulphur was reduced by 25%, which allowed gasoline endpoint to be increased, resulting in ca. 5 vol.% gasoline yield increase at constant gasoline sulphur level.
 
SuRCA Catalyst: Description
The SuRCA catalyst family offers a solution to full-range FCC gasoline sulphur reduction. SuRCA catalysts are designed to completely replace the conventional FCC catalyst in the circulating inventory, and are tailored to meet specific FCC unit objectives. SuRCA catalysts contain sulphur-reduction functionality, which typically provides full-range gasoline sulphur reductions of between 25-35% commercially.

SuRCA Catalyst: Commercial Experience of Meeting Gasoline Quality Legislations
Tier 3 regulations in the US require the reduction of average gasoline pool sulphur level to less than 10 ppm with an 80 ppm cap by January 2017, compared to the current limit of less than 30 ppm with an 80 ppm cap. Grace has substantial experience in similarly demanding environments like Japan. In the mid 2000s, Japan committed to lower gasoline sulphur levels. As early adopters of more stringent gasoline quality regulations, Japanese refiners faced similar challenges that US refiners face today in meeting Tier 3. Since 2005, these refiners have successfully utilised Grace GSR products to maintain compliance, observing 35%-40% reduction in the gasoline sulphur/feed sulphur ratios allowing them to meet the 10 ppm gasoline specifications.1 An example of a Japanese refiner meeting 10 ppm gasoline sulphur spec without increasing gasoline post-treater severity can be seen in Figure 2. In this case, as much as 35% gasoline sulphur reduction was achieved with the SuRCA catalyst.

Another example shown in Figure 3 shows a Japanese refiner that was able to maintain compliance with the 10 ppm gasoline sulphur spec while maintaining flexibility to either blend high sulphur coker gasoline into the gasoline pool or extend the VGO hydrotreater catalyst life. Again, SuRCAcatalyst technology was used and the refiner observed approximately 40% reduction in gasoline sulphur.
 
GSR 5 Additive: Description
The GSR 5 additive also offers a solution to full-range FCC gasoline sulphur reduction. The additive typically replaces 25% of fresh catalyst additions, and contains zeolite and matrix formulations to maintain the catalytic cracking performance. The sulphur-reduction functionality used in the GSR 5 additive is based on SuRCA technology, and similar full-range gasoline sulphur reductions of between 25-35% are achieved commercially.

GSR 5 Additive: Commercial Experience of Controlling Sulphur during a Feed Hydrotreater Outage
Refiners have created operating flexibility during hydrotreater outages by utilising Grace’s clean fuels GSR additive technology. Proper management of FCC feed hydrotreater outages becomes increasingly important as more and more refiners rely on hydrotreating to meet their per gallon gasoline sulphur limits. Running at higher severity increases the frequency of turnarounds. Conventional methods of ensuring that the gasoline pool stays below the sulphur limit during the hydrotreater turnaround are purchasing low sulphur feed or reducing FCC throughput. Either approach can significantly reduce refinery profitability. An alternative is to use one of Grace’s gasoline sulphur reducing technologies during the outage to provide operational flexibility while maintaining sulphur compliance and profitability. One such example of a refiner that used Grace GSR 5 sulphur reduction additive during a feed hydrotreater outage is shown in Figure 4. The refiner was able to process higher than typical feed sulphur and maintain gasoline pool sulphur compliance. Use of GSR 5 began two months prior to the 45-day feed hydrotreater outage. During that time, feed sulphur increased by as much as 35%. The three periods represented are typical operation (Base Period), GSR 5 before and during the outage where gasoline sulphur reduction ranged from 20-25%, and finally GSR 5 following the outage. The customer estimated that use of GSR 5 resulted in $1.7 million of savings during the hydrotreater outage. The results were so encouraging that the customer elected to continue using GSR technology, switching to a SuRCA catalyst and operating with post-outage feed sulphur 10-15% higher than the typical operation. This change to their operation grew annual profits by approximately $8 million.2


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