STARS and NEBULA - New Generations ofHydroprocessing Catalysts for the Production of Ultra

Low Sulfur Diesel

Sonja Eijsbouts, Frans Plantenga, Bob Leliveld, YoshimasaInoue* and Katsuhisa Fujita*

Akzo Nobel Catalysts B.V., Research Centre Amsterdam,P.O.Box 37650, 1030 BE Amsterdam, The Netherlands

and*Nippon Ketjen Co., Ltd., R&D Center,

17-4, Isoura-cho, Niihama, Ehime, Japan

IntroductionEU, Japan and US have decided to lower sulfur in diesel to

the 10 – 15 ppm level in very near future. This means that thatrefiners have to apply more and more severe hydroprocessing(more reactor volume, higher pressure and temperature), i.e. haveto invest heavily in new hydrodesulfurization (HDS) capacity andstart desulfurizing streams that were not treated before. To do thisin the most efficient and economic way is a major challenge forthe refiners, catalyst and process designers.

Type 2 Active SitesThe last few hundred ppm sulfur leftover after “normal”

hydrotreating is present in much less reactive molecules: alkyl-substituted dibenzothiophenes. These molecules not only reactslower but their reaction mechanism is also different, involvingfirst a hydrogenation of the aromatic part of the moleculefollowed by a desulfurization step (rather than directhydrogenolysis). This hydrogenation pathway has led to thedevelopment of a new generation of catalysts, whereby anothertype of active sites, Type 2, was maximized. Type 2 sites aregenerated by careful tuning of the metal-support interaction andare thought to be more effective for hydrogenation reactions. TwoType 2 catalysts, Ni-Mo KF848-STARS and Co-Mo KF757-STARSare commercially available.

Special Features of Type 2 Catalysts. The lower metal-support interaction leads to a different sulfidation behavior of theType 2 catalysts. The sulfidation is complete at lower temperature(Figures 1 and 2) and proceeds through a different Mointermediate (Mo5+) (Figure 2) in Type 2 catalysts compared toconventional catalysts, containing typically a mixture of Type 1and 2 sites.

Temperature (°C)

UV/TCD (normalized H

2S production/H

2 consumption ->)

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H2S: KF848 Stars catalystH2S: Conventional catalystH2: KF848 Stars catalystH2: Conventional catalyst

↑ H2 consumption

↑ H2S production

Ø H2S consumption

Figure 1. Temperature Programmed Sulfidation (TPS) patterns ofconventional Ni-Mo KF843 and Ni-Mo KF848-STARS catalysts.

Figure 2. X-ray Photoelectron Spectroscopy (XPS) spectra ofconventional Ni-Mo KF843 and Ni-Mo KF848-STARS catalysts.

Performance of Type 2 Catalysts. The incorporation ofType 2 sites leads to a higher activity of Ni-Mo (Figure 3) andCo-Mo catalysts. While traditionally Co-Mo catalysts were usedfor HDS, Ni-Mo catalysts are applied for some process conditions(higher pressure) nowadays. The reason is that the activityranking of a Ni-Mo Type 2 changes compared to a Co-Mo Type 2catalyst as a function of the hydrogen pressure and operatingseverity (Figure 4).

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Accessible Mo

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KF848

KF846

KF843

KF840

KF153

Figure 3. HDN activity (VGO) of conventional Ni-Mo (KF153,KF840, KF843 and KF846) and Ni-Mo KF848-STARS Catalysts.

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ppm S

RV

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Linear (low p)

Linear(medium p)Linear (high p)

Figure 4. Changing activity ranking of Ni-Mo versus Co-Mocatalysts due to changing reaction mechanism in diesel HDS atdifferent reaction pressures. Relative volume activity (RVA) HDSof KF848 is calculated versus the KF757 reference.

Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem. 2003, 48(2), 494

NEBULA CatalystThe opportunities are even bigger with the NEBULA

catalyst1), a joint development of Akzo Nobel with ExxonMobil,which is a totally novel hydroprocessing catalyst not madeaccording to today’s technology of alumina carriers withimpregnated metals. NEBULA is such an improvement in activity,that it enables refiners to produce ultra low sulfur diesel in mosthigh-pressure units that have been designed for the production of500 ppm S (Figure 5).

541

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test condition

pp

m S

KF848

Nebula

Figure 5. HDS performance of NEBULA and KF848 in diesel HDS.

Besides using NEBULA for treating the diesel fractions, NEBULAcan contribute to the production of low S diesel when used inVGO pretreatment, preceding the hydrocracking and FCC units(Figures 6-8). Just like in diesel HDS, KF757 has a goodperformance at higher product S levels. KF848 and especiallyNEBULA outperform KF757 at low product S levels. As really lowproduct S levels can be obtained only at low product N levels(Figure 9), not only the HDS but also the hydrodenitrogenation(HDN) and hydrogenation (HDA) activities are improved.

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DS

RVA HDS Nebula

RVA HDS KF848

Log. (RVA HDSKF848)Power (RVA HDSNebula)

Figure 6. HDS performance of NEBULA and KF848 in VGOhydrotreating. RVA HDS is calculated versus the KF757 reference.

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DN

RVA HDN Nebula

RVA HDN KF848

Log. (RVA HDNKF848)Log. (RVA HDNNebula)

Figure 7. HDN performance of NEBULA and KF848 in VGOhydrotreating. RVA HDN is calculated versus the KF757 reference.

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DA

RVA HDA Nebula

RVA HDA KF848

Log. (RVA HDAKF848)Log. (RVA HDANebula)

Figure 8. HDA performance of NEBULA and KF848 in VGOhydrotreating. RVA HDA is calculated versus the KF757 reference.

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product N

pro

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Figure 9. Product S and N level of hydrotreated VGOcorresponding to Figures 6 – 8.

Summary Catalyst DevelopmentFigure 10 shows the development of the “traditional”

hydroprocessing catalysts and the new catalyst generations,“STARS and NEBULA technology”.

0100200300400500600700800900195019551960196519701975198019851990199520002005YEARRelVol Activity

Figure 10. Development of hydrotreating catalyst in past 50years.

Already with the move to STARS, a new development S-curvewas started. At present, the end point of the graph is NEBULA, acatalyst with breakthrough activity that reaches four times theactivity of the conventional catalysts. Nowadays, NEBULA isfinding its place in the refinery processes. NEBULA catalyst notonly helps to use the existing units to meet the future productspecifications. It also helps to maintain the productspecifications while increasing the cycle length by running theunits at less severe conditions (e.g. lower temperature) or whileincreasing the unit throughput at normal operating conditions.

References1. D. Pappal; NPRA Annual meeting, March 23-25, 2003, AM-03-59.

Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem. 2003, 48(2), 495