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

Transcription

1 Institute of Energy Process Engineering and Chemical Engineering Diesel selective hydrocracking of Fischer-Tropsch wax Experimental investigations M. Endisch, M. Olschar, Th. Kuchling, Th. Dimmig TU Bergakademie Freiberg I Institute of Energy Process Engineering and Chemical Engineering Reiche Zeche I 9596 Freiberg I Tel. +49()3731/ I Fax +49()3731/ evt@iec.tu-freiberg.de I Web

2 Background Increasing demand in transportation fuels worldwide Decreasing availability of fossil Fuels Greenhouse gas emissions Substitution by biomass (XTL) derived fuel in middle-term 2

3 Background - XTL via Fischer-Tropsch(FT) Synthesis Biomass Synthesis gas production Coal Natural Gas Fischer-Tropsch synthesis Hydrocracking for product upgrading High quality transportation fuels 3

4 Fischer-Tropsch products Distribution of products from the Fischer-Tropsch synthesis 1 (Anderson-Schultz-Flory distribution).9 w n = n (1-α) 2 α (n-1).8 w n [% wt] Methane Ethane Flüssiggas LPG Benzin Naphtha Diesel Wachse Wax Industrial application probability of chain growth α 4

5 Hydrocracking Catalytic conversion of high-boiling hydrocarbons into branched and lower-boiling products in the presence of hydrogen Catalyst Bifunctional catalyst Acid support - amorphous oxides, crystalline zeolite, alumina - cracking and isomerisation function Metal component - noble metals (Pd, Pt) or base metal sulphides (Mo, W, Co, Ni) - hydrogenation and dehydrogenation function Aim: production of high quality middle-distillates (diesel) from wax 5

6 Experimental equipment Test facility for hydrocracking/hydrotreating at the Institute for energy process engineering and chemical engineering, TU BA Freiberg 6

7 Experimental equipment Reactor Trickle-bed Length: 1,2 mm Inside diameter: mm Isothermal operation by 5 independent heating circuits 5 thermocouples along the centre of the reactor in a thermolance Catalyst Extrudates with specific length Diluted with fine-grained, inert SiC Minimisation of wall effects, plug flow Controlling exothermal reactions Feedstock Directly transferable to the industrial process Inert layer Catalyst bed Inert layer Product Thermolance Thermocouple 7

8 Feedstock Paraffin A: - From dewaxing of lubricating oil - Predominantly n-paraffins with a chain length of 2 35 carbon atoms - Melting point: 52 6 C FT 96: - High-boiling fraction of the FT synthesis - n-paraffins with a chain length of 3 7 carbon atoms - Melting point: 96 1 C Paraffin A FT % wt Boiling temperature [ C] 8

9 Product characterisation Characterisation of the liquid products Classification by their boiling ranges: Product Cutpoints / C Light naphtha (LN) 2 8 Heavy naphtha (HN) 8-18 Middle distillates (Diesel) Unconverted product (UC) > 35 Cold flow properties (CFPP) Octane and cetane number Boiling behaviour (Simulated distillation, ASTM distillation ) Characterisation of the gaseous products Composition (GC) 9

10 Previous Experiments / Review Commercial naphtha selective catalyst Results - Very low diesel yields - Poor naphtha quality - No significant feed influence - Influence of the operating conditions on conversion, less on diesel yields Products Paraffin A % wt 4 2 Naphtha 18 C Diesel 35 C Unconverted Boiling temperature 1

11 Experimental investigations - Overview Commercial Hydrocracking catalyst - Base metals with amorphous support - Catalyst activation by reduction with H 2 Parameters - Temperature (WABT): C - Space velocity (WHSV): h -1 - Pressure: bar - Feed: FT 96, Paraffin A 11

12 Experimental results - pseudocomponents Pseudo-component distribution of liquid products of Paraffin A (WHSV = 1 h-1; p = 6 bar) Paraffin A Paraffin A Products Products C 355 C 365 C 373 C 38 C Naphtha 18 C Diesel 35 C Unconverted % wt Boiling temperature 12

13 Experimental results temperature influence Effect of Temperature (WHSV = 1 h -1 ; p = 6 bar; Feed Paraffin A) Gas LN HN Diesel UC 9 8 Diesel selectivity 5 7 Yields [% wt] % wt Conversion (35 C) Naphtha selectivity WABT [ C] WABT [ C] - Increasing temperature leads to a shift to lighter Products - With increasing conversion decreasing Diesel selectivity 13

14 Experimental results conversion influence Diesel yield and selectivity over conversion for all operating points Diesel selectivity Yield; Selectivity [% wt] Diesel yield Conversion [%] - Diesel yield and selectivity depend mainly on conversion - Increasing selectivity with decreasing conversion 14

15 Experimental results feed influence Products of Paraffin A and FT 96 from equal process parameters (WABT = 373 C; WHSV = 1 h -1 ; p = 6 bar) Paraffin A Products FT Product Paraffin A Product Paraffin A % wt Naphtha Product FT 96 Diesel 18 C 35 C Product FT 96 Unconverted 2 Boiling temperature - Poor influence of feed chain length 15

16 Fuel properties - comparison Comparison HC-Diesel (FT 96; 8 % Conversion) vs. DIN Diesel fuel Properties FT-HC- Diesel DIN EN 59 Relevance Cetane number combustion, emission Density (15 C) g/l consumption, emission PAH content % wt - 11 environment, emission Sulphur content mg/kg < 2 1 corrosion, emission CFPP C < -24 / -1 / -2 Fuel conveyance Distillation vaporised up to 25 C vaporised up to 35 C 95 % vol vaporised % vol % vol C < deposit, emission 16

17 Fuel properties - conversion influence Conversion influence on Diesel CFPP and Cetanenumber 1 CFPP [ C] Better cold flow properties with increasing conversion Conversion [%] - DCN (Derived Cetane Number) (Measurement in combustion chamber) - Decreasing Cetane number with increasing conversion DCN Conversion [%] 17

18 Conclusions Diesel obtained from hydrocracking of Fischer-Tropsch wax has excellent fuel 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 the production of low quality naphtha) - Recycling of the unconverted wax 18

19 Thank you for your attention The Authors would like to thank the Albemarle Catalyst Company for providing the catalyst and the German Federal Ministry of Consumer Protection, Food and Agriculture for the financial support. 19

20 Experimental results Pseudocomponents (FT96) 2

21 Experimental results WHSV influence Effect of space velocity (WABT = 365 C; p=6 bar; Paraffin A) Gas LN HN MD UC 9 Conversion 35 C 8 7 MD-Selectivity Yields [wt.%] 4 3 wt.% Naphta-Selectivity,7,8 1, 1,3 WHSV [h -1 ],7,9 1,1 1,3 WHSV [h -1 ] - Higher LHSV leads to an increasing of diesel-selectivity associated with decreasing conversion 21

22 Experimental results pressure influence Effect of pressure (WABT=365 C; LHSV=1 h -1 ; Feed Paraffin A) Gas LN HN MD UC 9 8 Conversion 35 C Yields [wt.%] wt.% MD-Selectivity Naphta-Selectivity Pressure [ C] pressure [bar] - No significant influence of pressure in the examined range 22

23 Fuel properties - CFPP Cold flow properties of HC-Diesels (DIN EN 116) Feed: Paraffin A Feed: FT 96 WABT [ C] (WHSV=1 h -1 ; p=6 bar) CFPP [ C] <-25 WHSV [h -1 ] (WABT=365 C; p=6 bar) CFPP [ C] ,3 +6 WABT [ C] (WHSV=1 h -1 ; p=6 bar) CFPP [ C] < < CFPP [ C] Conversion [%] 23

24 Fuel properties - Cetanenumber Cetanenumber of HC-Diesel WABT [ C] Feed LHSV [h-1] Cetanenumber (DIN 51773) DCN (EN 15195) BASF-Motor Brennkammer 373 FT Paraffin A , DCN Conversion [%] 24

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 25