Diesel selective hydrocracking of Fischer-Tropsch wax ...
Transcript of 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 [email protected] 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
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Background
Increasing demand in transportation fuels
worldwide Greenhouse gas emissions
Decreasing availability of fossil
Fuels
Substitution by biomass (XTL) derived fuel in middle-term
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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
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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
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►
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
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Experimental equipment
Test facility for hydrocracking/hydrotreating at the Institute for energy process engineering and chemical engineering, TU BA Freiberg
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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
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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
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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)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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Experimental results – Pseudocomponents (FT96)
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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
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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
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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]
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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
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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