diesel selective hydrocracking of fischer-tropsch wax

TU Bergakademie Freiberg I Institute of Energy Process Engineering and Chemical EngineeringReiche Zeche I 09596 Freiberg I Tel. +49(0)3731/39 4511 I Fax +49(0)3731/39 4555

Email evt@iec.tu-freiberg.de I Web www.iec.tu-freiberg.de

Institute of Energy Process Engineering andChemical Engineering

Diesel selective hydrocracking of Fischer-Tropsch wax – Experimental investigations –

M. Endisch, M. Olschar, Th. Kuchling, Th. Dimmig

2

Background

Increasing demand in transportation fuels

worldwide Greenhouse gas emissions

Decreasing availability of fossil

Fuels

Substitution by biomass (XTL) derived fuel in middle-term

3

Background - XTL via Fischer-Tropsch(FT) Synthesis

Biomass

Coal

Natural Gas

Synthesis gas production

Fischer-Tropsch synthesis

Hydrocracking for product upgrading

High quality transportation fuels

4

Fischer-Tropsch products

► Distribution of products from the Fischer-Tropsch synthesis(Anderson-Schultz-Flory distribution)

wn = n (1-α)2 α(n-1)

Methan

Ethan Flüssiggas

Benzin

Diesel

Wachse

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1probability of chain growth α

wn

[% w

t]

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

LPG

Methane

Ethane

Naphtha

Wax

Indu

stria

l app

licat

ion

5

►

Catalytic conversion of high-boiling hydrocarbons into branched andlower-boiling products in the presence of hydrogen

Hydrocracking

Acid support -

amorphous oxides, crystallinezeolite, alumina

-

cracking and isomerisationfunction

Metal component-

noble metals (Pd, Pt) or basemetal sulphides (Mo, W, Co, Ni)

-

hydrogenation anddehydrogenation function

Bifunctional catalyst

Aim: production of high quality middle-distillates (diesel) from wax

Catalyst

6

Experimental equipment

Test facility for hydrocracking/hydrotreating at the Institute for energy process engineering and chemical engineering, TU BA Freiberg

7

Experimental equipment

►

Reactor–

Trickle-bed

–

Length: 1,200 mm–

Inside diameter: 18.85 mm

–

Isothermal operation by 5 independentheating circuits

–

5 thermocouples along the centre of thereactor in a thermolance

►

Catalyst–

Extrudates

with specific length

–

Diluted with fine-grained, inert SiC

Minimisation of wall effects, plug flowControlling exothermal reactions

Directly transferable to the industrial process

Feedstock

Inert layer

Catalyst bed

Inert layer

ProductThermolance

Thermocouple

8

Feedstock

► Paraffin A:

-

From dewaxing of lubricating oil-

Predominantly n-paraffins with a chain length of 20 – 35carbon atoms

- Melting point: 52 – 60 °C

► FT 96: -

High-boiling fraction of the FT synthesis-

n-Paraffins with a chain length of 30 – 70 carbon atoms

- Melting point:

96 – 100 °C

0

2

4

6

8

10

12

14

% w

t

20-3

0

50-6

0

80-9

0

110-

120

140-

150

170-

180

200-

210

230-

240

260-

270

290-

300

320-

330

350-

360

380-

390

410-

420

440-

450

470-

480

500-

510

530-

540

560-

570

590-

600

620-

630

650-

660

680-

690

710-

720

740-

750

Boiling temperature [°C]

Paraffin A

FT 96

9

Product characterisation

►

Characterisation of the liquid products– Classification by their boiling ranges:

–

Cold flow properties (CFPP)–

Octane and cetane

number

– Boiling behaviour (Simulated distillation, ASTM distillation )

Product Cutpoints / °C

Light naphtha (LN) 20 – 80

Heavy naphtha (HN) 80 - 180

Middle distillates (Diesel) 180 - 350

Unconverted product (UC) > 350

►

Characterisation of the gaseous products– Composition (GC)

10

Previous Experiments / Review

► Commercial naphtha selective catalyst

-

Very low diesel yields

-

Poor naphtha quality

-

No significant feed influence

- Influence of the operating conditions on conversion, less on diesel yields

► Results

Naphtha UnconvertedDiesel180 °C 350 °C02468101214

% w

t

Paraffin AProducts

Boiling temperature

11

Experimental investigations - Overview

-

Temperature (WABT): 355-380 °C-

Space velocity (WHSV): 0.7-1.3 h-1

-

Pressure: 55-65 bar- Feed: FT 96, Paraffin A

► Commercial Hydrocracking catalyst

► Parameters

-

Base metals with amorphous support- Catalyst activation by reduction with H2

12

Experimental results - pseudocomponents

►Pseudo-component distribution of liquid products of Paraffin A(WHSV = 1 h-1; p = 60 bar)

Naphtha UnconvertedDiesel180 °C 350 °C

Paraffin A

Products

Boiling temperature

0

2

4

6

8

10

12

14

% w

t

380 °C373 °C

365 °C355 °C

350 °C

Paraffin A

Products

13

Experimental results – temperature influence

0

10

20

30

40

50

60

70

350 355 365 373 380

WABT [°C]

Yiel

ds [%

wt]

Gas LN HN Diesel UC

Conversion (350°C)

Naphtha selectivity

Diesel selectivity

0

10

20

30

40

50

60

70

80

90

100

350 355 360 365 370 375 380

WABT [°C]

% w

t

► Effect of Temperature (WHSV = 1 h-1; p = 60 bar; Feed Paraffin A)

-

Increasing temperature leads to a shift to lighter Products

- With increasing conversion decreasing Diesel selectivity

14

Experimental results – conversion influence

- Diesel yield

and selectivity

depend

mainly on conversion

- Increasing selectivity with decreasing conversion

► Diesel yield and selectivity over conversion for all operating points

0

10

20

30

40

50

60

70

80

90

20 30 40 50 60 70 80 90 100

Conversion [%]

Yiel

d; S

elec

tivity

[% w

t]

Diesel yield

Diesel selectivity

15

Experimental results – feed influence

- Poor influence of feed chain length

► Products of Paraffin A and FT 96 from equal process parameters

(WABT = 373 °C; WHSV = 1 h-1; p = 60 bar)

Product Paraffin A

Product FT 96

Naphtha UnconvertedDiesel180 °C 350 °C

Boiling temperature

0

2

4

6

8

10

12

14

% w

t

FT 96

Paraffin A

Products

Product Paraffin A

Product

FT 96

16

Fuel properties - comparison

Properties FT-HC- Diesel DIN EN 590 Relevance

Cetane number 67 ≥ 51 combustion, emission

Density (15 °C) g/l 0.77 0.82 – 0.845 consumption, emission

PAH content % wt - ≤ 11 environment, emission

Sulphur content mg/kg < 2 ≤ 10 corrosion, emissionCFPP °C < -24 0 / -10 / -20 Fuel conveyance

Distillationvaporised up to 250 °Cvaporised up to 350 °C95 % vol vaporised

% vol% vol

°C

3990371

< 65≥ 85≤ 360

deposit,emission

► Comparison HC-Diesel (FT 96; 80 % Conversion) vs. DIN Diesel fuel

17

Fuel properties - conversion influence

-30

-25

-20

-15

-10

-5

0

5

10

35 45 55 65 75 85 95Conversion [%]

CFP

P [°

C]

65

67

69

71

73

7577

79

81

83

85

65 70 75 80 85 90 95 100

Conversion [%]

DC

N

► Conversion influence on Diesel CFPP and Cetanenumber

- DCN (Derived Cetane Number)(Measurement in combustionchamber)

- Better cold flow properties withincreasing conversion

- Decreasing Cetane number withincreasing conversion

18

Conclusions

►

Diesel obtained from hydrocracking of Fischer-Tropsch wax has excellentfuel properties

► The product composition is influenced by:-

Choice of catalyst-

Reactor temperature WABT

- Space velocity WHSV

► Optimised process conditions for the production of high quality diesel:-

Low conversion high diesel selectivity (to minimise theproduction of low quality naphtha)

- Recycling of the unconverted wax

19

Thank you for your attention

The Authors would like to thank the Albemarle Catalyst Company for providing the catalystand

the German Federal Ministry of Consumer Protection, Food and Agriculture for the financial support.

20

Experimental results – Pseudocomponents (FT96)

21

Experimental results – WHSV influence

►

Effect of space

velocity

(WABT = 365°C; p=60 bar; Paraffin A)

0

10

20

30

40

50

60

70

0,7 0,8 1,0 1,3

WHSV [h-1]

Yiel

ds [w

t.%]

Gas LN HN MD UC Conversion350°C

Naphta-Selectivity

MD-Selectivity

0

10

20

30

40

50

60

70

80

90

100

0,7 0,9 1,1 1,3

WHSV [h-1]

wt.%

- Higher LHSV leads

to an increasing

of diesel-selectivity

associated

with

decreasing

conversion

22

Experimental results – pressure influence

►

Effect of pressure

(WABT=365 °C; LHSV=1 h-1; Feed Paraffin A)

0

10

20

30

40

50

60

70

55 60 65

Pressure [°C]

Yiel

ds [w

t.%]

Gas LN HN MD UC

Conversion350°C

Naphta-Selectivity

MD-Selectivity

0

10

20

30

40

50

60

70

80

90

100

55 57 59 61 63 65

pressure [bar]

wt.%

-

No significant

influence

of pressure

in the

examined

range

23

Fuel properties - CFPP

WABT [°C](WHSV=1 h-1;

p=60 bar)

CFPP [°C]

355 +8365 -6373 -18380 <-25

WHSV [h-1](WABT=365 °C;

p=60 bar)

CFPP [°C]

0.8 -251 -6

1,3 +6

►

Cold flow

properties

of HC-Diesels (DIN EN 116)

WABT [°C](WHSV=1 h-1;

p=60 bar)

CFPP [°C]

365 -13373 <-24380 <-27

Feed: Paraffin A Feed: FT 96

-30

-25

-20

-15

-10

-5

0

5

10

35 45 55 65 75 85 95Conversion [%]

CFP

P [°

C]

24

Fuel properties - Cetanenumber

►

Cetanenumber of HC-Diesel

65

67

69

71

73

75

77

79

81

83

85

65 70 75 80 85 90 95 100Conversion [%]

DC

NWABT [°C] Feed LHSV [h-1] Cetanenumber

(DIN 51773)BASF-Motor

DCN (EN 15195)

Brennkammer373 FT 96

166.7 -

380 - 69.5365

Paraffin A- 80.5

373 67 77.2365 0,8 - 70.6

25

Influencing parameters

►

Operating variables conversion, product distribution–

Temperature WABT

–

Weight hourly space velocity WHSV–

Hydrogen Partial Pressure

►

Feedstock operating conditions, product distrib.

►

Catalyst design operating conditions, product distribution, quality