Continuous Biodiesel Production

Transcription

1 NW/CW Project Nr Continuous Biodiesel Production Reactive Distillation Makes It Happen Tony KISS, A.C. Dimian, G. Rothenberg, F. mota UNIVERSITY F AMSTERDAM van t Hoff Institute for Molecular Sciences Nieuwe Achtergracht 166, 1018 WV Amsterdam Tel , A.A.Kiss@uva.nl Web: staff.science.uva.nl/~ktony

2 Acknowledgement Jurriaan Beckers Marjo C. Mittelmeijer-Hazeleger STW Dutch Technology Foundation NW/CW Project Nr Entrainer-Based Reactive Distillation for Synthesis of Fatty Acids Esters Cognis, leon, Sulzer and Uniquema Thank you! 2/24

3 Biodiesel = green energy Emission type B20 = 20% biodiesel B20 B100 Biodiesel = mono-alkyl esters of fatty acids Total unburned hydrocarbons 20% 67% Safe, renewable, non-toxic, biodegradable Carbon monoxide (C) 12% 48% Carbon dioxide (C 2 ) 16% 79% C 2 Light Raw materials: vegetable oils, fat, recycled grease Particulate matter 12% 47% C 2 Positive life cycle energy balance Nitrogen oxides (N x ) +2% +10% Positive social impact Sulphur oxides (S x ) 20% 100% Polycyclic Aromatic Hydrocarbons (PAH) 13% 80% Less emissions than regular petroleum diesel Nitrated PAH's (npah) 50% 90% Biomass Biodiesel A.A.Kiss@uva.nl 3/24

4 Project goals Development of an active and selective solid acid catalyst for fatty acids esterification. Continuous biodiesel production process based on catalytic reactive distillation. Catalyst requirements Water-tolerant Long life Inexpensive Active, selective, stable Easy to use Available on industrial scale 4/24

5 Applications Cosmetics Food Pharmaceuticals Why fatty esters? Food industry Pharmaceuticals Cosmetics Plasticizers Bio-detergents Bio-diesel Bio-stuff 5/24

6 Industrial key players STEARINERIE-DUBIS 6/24

7 Process comparison Current process Batch esterification High alcohol / acid ratios Homogeneous catalysis Difficult separation Corrosive & toxic Novel process Continuous esterification Reactive distillation Heterogeneous catalysis Easy separation Environmentally friendly Reduced investment costs Reduced energy consumption Increased process controllability Enhanced overall rates Make up Fatty acid Alcohol Steam Water Fatty ester The key to success is an active & selective solid acid catalyst. A.A.Kiss@uva.nl 7/24

8 Fatty acids & alcohols Saturated fatty acids: -(CH 2 ) n -CH Lauric acid (n=10) Myristic acid (n=12) Palmitic acid (n=14) Stearic acid (n=16) Arachidic acid (n=18) Unsaturated fatty acids Aliphatic alcohols: Methanol Ethanol Propanol 2-Ethyl hexanol Palmitoleic acid: (CH 2 ) 5 CH=CH(CH 2 ) 7 CH leic acid: (CH 2 ) 7 CH=CH(CH 2 ) 7 CH A.A.Kiss@uva.nl 8/24

9 Reaction pathways REACTANTS Fatty Acid Alcohol esterification etherification dehydration Fatty Ester Ether Water Alkene Main product Secondary products Excess of alcohol Water removal by distillation 9/24

10 Reaction mechanism C R H H + C R H Catalyst H + H + R' H R C H H C R H H + R' RCH + R H RCR + H 2 Secondary reactions: 2 Alcohol Ether + H 2 Alcohol Alkene + H 2 2 Acid Anhydride + H 2 Catalyst H H H + C C R H + H 2 H + R H C R' 2 R R' R' R H + C R' R C H + R' Similar mechanism for hetero- and homogeneous catalysis. A.A.Kiss@uva.nl 10/24

11 Surface hydrophobicity Water tolerant. Not enough acid sites. C H + H hydrophobic surface with isolated acid site C H + H C H + H C H + H Proper trade-off hydrophobicity-acidity. Good catalytic activity. hydrophobic surface with adjacent acid site Water sensitive. Easy deactivation. H 2 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H + H + H + H H + H H + H + H 2 hydrophilic surface/ numerous acid sites Influence of surface hydrophobicity on catalytic activity. A.A.Kiss@uva.nl 11/24

12 Solid acid catalysts Zeolites and clays Beta, Y, MR, ZSM-5 HeteropolyAcids xides, sulphates Composite materials Amberlyst Nafion -(CH 2 ) 10 -CH + C 8 H 15 H Dodecanoic acid -(CH 2 ) 10 -CC 8 H 15 + H 2 2 Ethyl hexyl dodecanoate 2 Ethyl hexanol Acid catalyst Carbon-based catalysts Polysulfonated aromatics = Not tested yet A.A.Kiss@uva.nl 12/24

13 Catalyst screening Reaction profiles for esterification of dodecanoic acid with 2-ethylhexanol 100 H 2 S 4 1%wt 100 Amberlyst 80 Amberlyst 5%wt 80 SZ Conversion / [%] Zeolites Non-catalyzed Alcohol:Acid = 1:1 Conversion / [%] Nafion Non-catalyzed Alcohol:Acid = 1:1 0 T=130 C 0 T=150 C, 3%wt catalyst Time / [min] Time / [min] rganic resins are not thermo-stable. Zeolites have low activity. A.A.Kiss@uva.nl 13/24

14 Zeolites structure *BEA Beta, tetragonal MFI ZSM-5, orthorhombic Diffusion limitations?! MR Mordenite, orthorhombic 2-ethylhexyl dodecanoate 3.06 Å Å 7.78 Å 4.86 Å 14/24

15 Sulphated zirconia Reaction profiles for esterification of dodecanoic acid with 2-ethylhexanol Conversion / [%] Alcohol:Acid = 1:1 2%wt SZ Catalyst SZ 2%w 180 C 160 C Time / [min] Non-catalyzed 180 C 160 C Initial rate 7.3% min % min % min % min -1 Conversion / [%] Conversion / [%] Amberlyst Non-Catalyzed Nafion SZ Non-Catalyzed Nafion SZ Amberlyst 20 min 60 min 0% 1% 2% 3% SZ T=150 C T=160 C T=170 C Similar activity for esterification with 1-propanol and methanol. A.A.Kiss@uva.nl 15/24

16 Experiments + Simulations Integration of experimental results with simulations of the reactive distillation (RD) setup, in AspenTech AspenPlus Distillate Reflux RD column sections Fatty acid a a. Rectifying section (water) b b. Recovery of alcohol Feeds Alcohol c d e Recycle c. Reaction zone d. Recovery of fatty acid e. Stripping section (ester) Biodiesel A.A.Kiss@uva.nl 16/24

17 Thermodynamic analysis Water T b =100 ºC 2-Ethylhexanol T b =186 ºC n-propanol T b =97 ºC Methanol T b =65 ºC Dodecanoic acid T b =298 ºC 2-Ethylhexyl dodecanoate T b =334 ºC n-propyl dodecanoate T b =302 ºC Methyl dodecanoate T b =267 ºC A.A.Kiss@uva.nl 17/24

18 CPE analysis ne liquid phase low conversion alcohol excess T < 100ºC T < 100ºC reactants molar ratio=1 LLE Chemical reaction and phase equilibrium VLE T > 100ºC open system water removal T > 100ºC closed system P > 1 bar VLLE A.A.Kiss@uva.nl 18/24

19 RD process methanol Ester, 267ºC Acid, 298ºC 1 Feasible RD process. High purity products. X 2 (acid+ester) Alcohol, 65ºC Water, 100ºC X 1 (water+acid) RDC Distillation column Dodecanoic acid Water 99.9 % Feed ratio 1:1 Methanol Evaporator Ester 99.9 % A.A.Kiss@uva.nl 19/24

20 Effect of reflux ratio Fatty acid Partial alcohol conversion Highest reaction rate Fatty acid Total alcohol conversion Highest reaction rate Alcohol Total acid conversion Alcohol Total acid conversion Maximum reaction rate is located in the centre of RD column for an optimum reflux ratio 20/24

21 Entrainer-based RD flowsheet Feasible process. High purity products >99.9% 100 With entrainer Entrainer Make up Acid conversion, % 99 No entrainer Fatty acid Decanter Stripper Catalyst loading, kg/m 3 Steam Alcohol Evaporator Water Reactive distillation column Biodiesel Enhanced mass transfer and reduced catalyst loading when entrainer is used. A.A.Kiss@uva.nl 21/24

22 RDC profiles Liquid composition and temperature profiles 1 Separation zone Reaction zone Separation Reaction 500 Liquid mole fraction Propanol n-propyl acetate Water n-propyl laurate Lauric acid Temperature, K Stage Stage A.A.Kiss@uva.nl 22/24

23 Reactive distillation advantages No external recycles Reduced investment costs Reduced energy consumption Increased process controllability Reaction Separation Equilibrium shifted to products Enhanced overall rates Improved selectivity Break azeotropes Handle difficult separations 23/24

24 Conclusions Surface hydrophobicity and acid sites density determines catalyst's activity & selectivity. Catalysts with small pores (e.g. zeolites) are not suitable. Resins are active but not thermally-stable. Sulphated zirconia is active, selective and stable. Biodiesel production by reactive distillation is feasible. GREEN ENERGY Biodiesel 24/24