kaspar vogt technical manager houston, texasakbal.imp.mx/foros-ref/xvii/cip/cip2.pdf ·...

Crossing Frontiers in the Performance and Economic

Return of ULSD UnitsXVII FORO DE AVANCES DE LA INDUSTRIA DE LA REFINACION

Kaspar VogtTechnical ManagerHouston, Texas

2

Your ULSD Unit is Unique

• Large variation in conditions and feedstocks– Undercut virgin to 100% cracked feedstock– 15 to over 100 bar H2 pressure (250 – 1500 psi)– 0.3 to over 2 hr-1 LHSV

• Optimal performance and economics balances– cycle length, hydrogen consumption, catalyst cost…– against operating conditions and feedstock selection

Generating economic return from ULSD units requires a tailored solution

3

What’s Happening Inside the Reactor?

Dibenzothiophenes

Sulfides, Mercaptans,Thiophenes

Benzonaphthothiophenes

Benzothiophenes

Product (10 ppm S)

Dibenzothiophenes



Benzothiophenes

90%

Dibenzothiophenes



Benzothiophenes

80%

Dibenzothiophenes



Benzothiophenes

70%

Dibenzothiophenes



Benzothiophenes

60%

Dibenzothiophenes



Benzothiophenes

50%

Dibenzothiophenes



Benzothiophenes

40%

Dibenzothiophenes



Benzothiophenes

30%

Dibenzothiophenes



Benzothiophenes

20%

Dibenzothiophenes



Benzothiophenes

10%

Dibenzothiophenes



Benzothiophenes

Feed (1.2 wt% S)

4

Reaction Zones in ULSD

• Zone 1– Remove easy sulfur via

direct route HDS

• Zone 2– Remove more difficult

sulfur via direct route HDS– Remove nitrogen

• Zone 3– Nitrogen free– Remove sterically hindered

sulfur via hydrogenation route HDS

Log S, N

SN

S < 10 ppm

Zone 1

Zone 2

Zone 3

5

• Reaction rate unconstrained• Selectivity most important• Balance hydrogen consumption and stability

• Reaction rate limited by inhibition• Catalyst performance critical• High HDN activity needed• Medium to high pressure: NiMo preferred• Low to medium pressure: CoMo preferred

• Reaction rate limited by direct desulfurization• Moderate activity catalyst acceptable• CoMo or NiMo acceptable

Trans Reactor Catalyst Selection: STAX™

Zone 1

Zone 2

Zone 3

6

Dimensions of Catalyst SelectionOperating Conditions and Feedstock

Outlet ppH2

Feed

Nitr

ogen

Cracked Content

Unstable

Over designed

7

Dimensions of Catalyst SelectionCatalyst Type

Outlet ppH2

Feed

Nitr

ogen

CoMo

NiMo

Cracked Content

8

Dimensions of Catalyst SelectionCatalyst Acidity

Outlet ppH2

Feed

Nitr

ogen

Lower Acidity

Higher Acidity

Cracked Content

9

A Large Catalyst Portfolio Covers the Full Range of ULSD Units

Outlet ppH2

Feed

Nitr

ogen

KF 770

KF 757

STAX™

KF 767KF 771

10

HYD Sites DDS Sites

KF 757

KF 770

HDS Relative Volume Activity

KF 771

New Catalysts for ULSD

• Increased DDS sites for high HDS activity• Increased HYD sites to assist HDS and

maximize HDN for a given pressure• Step out combination of activity and stability

+20%

+30%

11

HDS Reaction Pathways

– HDS proceeds via Hydrogenolysis (DDS) and Hydrogenation (HYD) routes

– DDS route is a single step cleavage of C-S bond to form H2S

– HYD route is a multi-step reaction� Hydrogenation of 1 or more aromatic ring(s)� Cleavage of C-S bond

– HYD route is usually (much) slower than DDS route– Hydrogenation step of HYD route is rate determining– Hydrogenation rate is limited by thermodynamics

12

DDS versus HYD

– DDS• Main pathway for easy sulfur, e.g. DBT• Favored over HYD at lower ppH2 and lower

temperature• Inhibited mainly by H2S, CO and basic N

– HYD• Main pathway for hard sulfur, e.g. 4,6 DMDBT• HYD is favored at high ppH2 and at high temperature

(within equilibrium constraints)• Inhibited by basic and non-basic N and polynuclear

aromatics

13

Kinetics for Desulfurization of 4,6-DMDBT

S S S S

DM-BP DM-CHB DM-BCH

DMDBT TH-DMDBT HH-DMDBT DH-DMDBT

0.001

0.034

2.3

0.8

0.1 0.7 1.35

0.04

X. Li, A. Wang, M. Egorova, R. Prins, J. Catal. 250 (2007) 283

DD

S

HYD

Bi Phenol , Tera Hydrol Di Benzo Di , Cyclo Hexal Hydrol , Di Hexal , Cyclo Hexyl Benzene, Bi Cyclo Hexyl

14

– DDS/HYD selectivity is critical

– High DDS: Enhanced HDS – even on hard sulfur

– High HYD: Sensitivity to thermodynamic instability

Production of ULSD at Low Pressure is Challenging

S

S S

…

15

Thermodynamic Instability

– At low ppH2 aromatic equilibrium shifts from kinetic to thermodynamic regime at relatively low temperature

– HYD reaction pathway slows due to reverse reaction

Outlet ppH2

Tem

pera

ture

S S

S S

HeavenHell Purgatory

16


– DDS/HYD selectivity can change the onset of thermodynamic instability– Increased operating window at low pressure

Outlet ppH2

Tem

pera

ture

S S

S S

Higher DDS Selectivity

17


– Too much HYD selectivity can enhance the onset of thermodynamic instability

– Reduced operating window at low pressure

Outlet ppH2

Tem

pera

ture

S S

S S

18

Keys to Successful Production of ULSD at Low Pressure– Control hard sulfur content – function of unit pressure

• Limit End Point: hard sulfur content increases with EP• Limit Refractory Feeds: LCO has highest hard sulfur content• Limiting LCO End Point has an especially positive effect

– Maximize outlet ppH2

• Maximize hydrogen circulation and availability• Maximize treat gas purity• Remove light tails

– Use a catalyst system designed for low pressure• Right DDS/HYD selectivity• Inter-reactor catalyst selection also important

: KF 770: STAX™

19

Developing a Low Pressure ULSD Catalyst– DDS/HYD selectivity is key design parameter– Kinetics of DDS and HYD pathways can be measured

using model compounds– GCxGC-FID techniques provide quantitative analysis of

HDS intermediates and products• Measure activity and selectivity for reaction pathways

– Experiments performed under realistic conditions in High Throughput test units using Design of Experiment (DoE) techniques

– Inhibition effects mimicked by adding Nitrogen and/or PNAs

20

Po

lari

ty

Boiling Point

GCxGC-FID: Full Range Straight Run Diesel

21

GCxGC-FID: 3 Model Compounds

DBT

4-MDBT4,6-DMDBT

Cyclo-Hexyl-Benzenes (CHB)

Bi-Phenyls (BP)

Bi-Cyclo-Hexyls (BCH)

Po

lari

ty

Boiling Point

22

Design of KF 770

– Design Goals• Activity: ? DDS, ? HYD• Selectivity: ? DDS, ? HYD

– Methodology• High throughput experimentation to develop activity /

composition relationships• Model feed experiments to determine selectivities• GCxGC-FID to monitor reaction chemistry

23

Optimizing DDS/HYD Selectivity

10

12

14

16

18

20

0 5 10 15 20 25 30 35 40

4,6 DM-DBT Conversion (%)

DD

S S

elec

tivi

ty (%

)

KF 757

KF 770 DoE

Model compound study shows ~20% higherDDS selectivity for KF 770 Prototype

KF 770 Prototype

24

Performance Validation on Distillate Feedstock– Model compound results must be validated on real feeds– Pilot plant tests conducted to confirm KF 770

performance benefit– Feedstock

• Sulfur: 0.65 wt%• Nitrogen: 80 ppm• FBP (SimDist): 391°C (736°F)

– Operating Conditions• Inlet ppH2: 20 bar (290 psi)• H2/Oil: 90 Nl/l (540 SCFB)• LHSV: 0.7 1/hr

25

60%

70%

80%

90%

100%

110%

120%

130%

140%

150%

160%

15 20 25 30 35 40 45 50 55 60

Days on Stream

RV

A H

DS

(K

F 7

57=1

00)

325°C 338°C 341°C 345°C

Desulfurization Activity

26

0

5

10

15

20

25

30

35

40

45

50

15 20 25 30 35 40 45 50 55 60

Days on Stream

Su

lfu

r (p

pm

)

KF 770

KF 757

325°C 338°C 341°C 345°C

Diminishing Benefit of Increasing Temperature

Lower deactivation rate for higher DDS selective catalyst

27

Commercial Example of Low Pressure ULSD Unit– Unit Characteristics

• 3 bed reactor with quench • 45 bar (650 psi) inlet pressure• Low H2 purity results in reactor outlet partial

pressure of <35 bar (500 psi)– Feed Characteristics

• 85-90% Straight run / 10-15% Visbreaker distillate• 1.5% S / 400 ppm N• Heavy tail on distillation

28

Unit Objectives and Challenges

– Unit Objectives• ULSD: <10 ppm S• Maximize cracked feed intake

– Operational Challenges• High feed nitrogen inhibits hard sulfur removal• Heavy tail on distillation introduces significant quantity

of hard sulfur (DBTs)• Catalyst system must balance the HYD route

requirements to remove the hard sulfur while avoiding thermodynaminc instability

29

First Cycle

– Catalyst System Design Basis• Hard sulfur removal controls ULSD production• Increase hydrogenation power of catalyst system• Remove nitrogen to improve hydrogenation capability

– Catalyst System• NiMo catalyst in first 2 beds to remove nitrogen• CoMo catalyst with hydrogenation power in the last

bed to remove remaining hard sulfur– Result: 3 Month Cycle

30

First Cycle Performance

320

330

340

350

360

370

380

390

400

0 10 20 30 40 50 60

Days on Stream

Tem

p. f

or

10 p

pm

S (

°C)

0

5

10

15

20

25

30

35

40

Pro

du

ct S

ulf

ur

(pp

m)

Product S

Normalized WABT

31

First Cycle Post Mortem

– Low hydrogen partial pressure did not allow for effective nitrogen removal

– A low nitrogen environment favorable for hard sulfur removal by HYD was not created

– HDS in a high nitrogen environment required high operating temperatures

– High operating temperatures + catalyst with high hydrogenation power caused onset of thermodynamic instability

– Thermodynamic instability resulted in very fast deactivation – as high as 11°C/month (20°F)

32

• Reaction rate unconstrained• Selectivity most important• Balance hydrogen consumption and stability

• Reaction rate limited by inhibition• Catalyst performance critical• High HDN activity needed• Medium to high pressure: NiMo preferred• Low to medium pressure: CoMo preferred

• Reaction rate limited by direct desulfurization• Moderate activity catalyst acceptable• CoMo or NiMo acceptable

Trans Reactor Catalyst Selection: STAX™

Zone 1

Zone 2

Zone 3

33

Second Cycle

– Catalyst System Design Basis• Promote HDN and HYD route HDS in the upper part of the

reactor where hydrogen pressure is highest• Finish the sulfur removal using a catalyst with high DDS/HYD

selectivity since HYD route is hindered by low pressure, high T and high N

– Catalyst System• Top bed: CoMo with high DDS (KF 770)• Middle bed: CoMo with high hydrogenation power (KF 767)• Bottom bed: CoMo with high DDS/HYD selectivity (KF 770)

– Result: 1 Year Cycle

34

Second Cycle Performance

320

330

340

350

360

370

380

390

400

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375

Days on Stream

Tem

p. f

or

10 p

pm

S (

°C)

0

5

10

15

20

25

30

35

40

Pro

du

ct S

ulf

ur

(pp

m)

Product S

Normalized WABT

35

Second Cycle Analysis

– Desulfurization performance under high nitrogen conditions greatly improved

– Onset of thermodynamic instability substantially delayed– One year cycle length achieved

36

Summary

– Production of ULSD at low pressure requires a precise balance ofmany variables• Feedstock type and properties to control hard sulfur intake• Delay onset of thermodynamic instability phase as long as

possible• Control of DDS/HYD selectivity to match conditions in the reactor

– Exceptionally high DDS/HYD selectivity of KF 770 matches the needs of many low pressure ULSD units

– STAX™ technology can further improve low pressure ULSD performance by properly managing inter-reactor chemistry

37

100%

110%

120%

130%

140%

150%

Low Pressure MediumPressure

HighPressure

RV

A H

DS

(K

F 7

57=1

00)

KF 767KF 770KF 771

Activity Benefit is Pressure Dependent

38

A Large Catalyst Portfolio Covers the Full Reactor Fill Cost

Outlet ppH2

Feed

Nitr

ogen

KF 770

STAX™

KF 771$€¥

39

Dimensions of Catalyst SelectionReactor Fill Cost

• With low margins a fill cost criteria to catalyst selection is also important

• Minimize cost without compromising performance– Use trans reactor know-how (STAX™) to place lower

cost catalysts where activity is not limiting– Reduced catalyst density– Effective use of rejuvenated catalysts

40

Lower Fill Cost by Reduced Density

effDk

AV

=ΦIntrinsic reaction rate

Diffusion rate

-1%99100RVA HDS

-7%0.730.78Density (g/cc)

?KF 757-1.3QKF 757-1.5E

Catalyst utilization described by Thiele modulus

41

Effective Use of Rejuvenated Catalyst

• Use of STAX technology to determine where and how much rejuvenated catalyst to place

• Lower fill cost with high performance

30/70*100100100

CatalystLoad (%)

12013095

100

Calc.RVA HDS

+8000

STAX™Benefit

128STAX™130KF 77195KF 757 REACT

100KF 757

ActualRVA HDS

Product

*KF 757 REACT / KF 771

42

Summary of ULSD Catalyst Toolkit

Trans Reactor Catalyst Selection• STAX™

Performance Catalysts• KF 770, KF 771

Value Catalysts• KF 757, KF 767

Reduced Fill Cost• 1.3 mm Quadralobes• REACT Rejuvenated Catalyst

43

Increase Margins by Processing Distressed Feedstocks

• Constraints to increased LCO processing– Low cetane– High hydrogen consumption and reactor exotherm– Increased fouling rate– Higher operating temperature required for sulfur removal

• Catalyst solutions to maximize LCO content– Latest generation catalysts to reduce required operating

temperature– Catalyst system design to balance hydrogen consumption with

hydrogen availability– Catalyst selection to maintain stability in the fouling environment

44

$0.00

$0.20

$0.40

$0.60

$0.80

$1.00

0 5 10 15

Additional LCO (%)

Ad

dit

ion

al M

arg

in (

$/B

BL

)

$2.50/BBL LCO Upgrade Value

$5.00/BBL LCO Upgrade Value

Increased Unit Margins by Processing Additional LCO

Potential Gain with Improved Catalyst System

$2 - 10 MM/Year for a Typical ULSD Unit

45

Summary

• Your ULSD unit is unique: the best economic return will come from a tailored catalyst system

• Cost effective solutions can still give step out performance– Apply step-out activity catalysts where they provide the most

benefit– Apply lower density and rejuvenated catalysts where most

effective

• Extra margin from processing distressed feeds provides far higher returns than a cheaper catalyst fill

• Albemarle’s portfolio of ULSD catalysts and application expertise help maximize economic return

kaspar vogt technical manager houston, texasakbal.imp.mx/foros-ref/xvii/cip/cip2.pdf ·...

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