Enzyme Catalysis for Biomass Based Diesel Fuels
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Transcript of Enzyme Catalysis for Biomass Based Diesel Fuels
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Enzyme Catalysis for Biomass Based Diesel Fuels
Rachel Burton
February 20, 2014
Department of Chemical Engineering,
North Carolina State University CHE 596-16 Biodiesel Production Technology
February 20, 2014
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“People don’t buy what you do, they buy why you do it.” –Simon Sinek
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Outline
• Why use an enzyma:c approach to biodiesel?
• -‐Benefit over chemical catalysts
• Overview of enzyma:c biodiesel • -‐Enzymes for commercial produc:on
• -‐Transesterifica:on
• -‐Esterifica:on
• Enzyme Reuse
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Quick Definitions TAG = Triglycerides (fat/oil) DAG = Diglycerides FFA = Free fatty acids FAME (or ME) = Fatty Acid Methyl Esters (biodiesel made using methanol) Immobilized vs. Liquid Enzymes CALB = Candida Antarctica Lipase B Novozym 435 = CALB immobilized on a plastic support (.5mm beads) TL = Thermomyces Lanuginosa lipase
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Advantages of Enzymes for Biodiesel
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Sustainability Profile
• National Research Council’s Committee on Water Implications of Biofuels Production: 1 gallon of wastewater: gallon of biodiesel produced. (Oct. 2007)
• 2007, Harding et al, LCA analysis between enzymatic & chemical catalysis for biodiesel
• Flammable and hazardous substance exposure reduction
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Improved performance linked to lower energy requirements for hea:ng in the process Terrestrial ecotoxicity levels are reduced by 40% with the removal of mineral acid from the process
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Hurdles to Enzymes for Biodiesel
• 15 years of research
• Hundreds of articles
• Many different
enzymes, reaction
conditions, etc.
• Overall conclusion in
most cases – too
expense
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Why Now? Chicken or the egg problem:
enzyme development vs. market development.
Confluence of events:
• Biodiesel industry is more mature and more secure
• Drive for lower cost feedstocks, presence of high FFA virgin oils
• Demand for increased fuel quality • Competition for fats/oil from
renewable diesel will push efficiency • Industry recognition of problems
with soaps, low quality glycerin, and difficulty of acid esterification
Causes process development: • Commercial enzyme reuse trials • Lower cost enzyme production
http://www.channelshirt.com/product/13/208/Chicken-Or-Egg-Tshirt.html
Commercial Viability!
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Access to affordable feedstocks
Yellow Grease
Tallow
Soy oil
Feedstock prices rising for the 2nd time; now in accordance to petrol market
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Reusability Enzymes used for biodiesel production lose
activity by:
High heat (>50C or >122F) Excess alcohol
In addition, Immobilized enzymes can lose
activity by:
Any alcohol out of phase Large excess of alcohol in phase (~5% or more)
Glycerol out of phase High shear can cause immobilized enzymes to come
off of the carrier Certain polar contaminants
Mineral acids
Temporary vs. Permanent activity loss
Temporary: physical blocking of active sites Permanent: denaturing due to excess methanol
Reusability of enzymes is the key
to commercial viability!
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A brief history Early Work (1987 - 1995)
• Studied cosolvents like iso-octane, hexane, diesel fuel. • Evaluated aqueous, non aqueous, and solvent-free systems, different types of
alcohols, impact of water • Studied a wide variety of liquid enzymes
• Mike Haas, Tom Foglia, Martin Mittelbach, and many others • No real biodiesel production, so these were interesting but not practical
Resurgence of interest (1999 - 2008)
• Better immobilized enzymes • Solvent free systems, good enzyme reuse
• First large scale plant in China using cosolvents ( tert-butanol )
Current Developments • Novozymes developing enzymes, immobilization techniques, lowering costs
• Piedmont Biofuels • Transbiodiesel in Israel
• Sunho in Taiwan • Blue Sun & Viesel
• Renewed interest from universities and private biodiesel producers for lab and pilot sized reactors
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Summary Articles
• Haas, 2002 (review of early literature)
• Fjerbaek, 2009
• Ranganathan, 2007
• Basic components of reviews • enzyme type
• liquid vs immobilized • support type
• reaction conditions • conversion
• number of reuses • tolerance to water, methanol
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Fjerbaek et al.: Biodiesel Production Using Enzymatic Transesterification.
2009.
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Cosolvents – Li (2006) Tert-butanol as
cosolvent
Advantages • Can use more excess
methanol without deactivation
• Deactivation due to glycerol (clogging) does
not occur • Impressive enzyme reuse
Built full scale plant based on
this process in China
Disadvantages • Large amount of co-solvent required which must be removed at the end via
distillation • Still had high FFA at end of process
• Reaction rate still slow
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Cosolvents – Zheng (2008) • Tert-Amyl Alcohol as cosolvent
Batch Reactions • 1.78g soybean oil
• 2 – 6ml amyl alcohol • 2% Novozym 435 (CALB) • reaction time ~ 15 hours
• Add graph here
Excellent reuse, but same problems as Li
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Watanabe and Shimada (2001, 2005)
No cosolvent Use multi-stage methanol addition
to avoid deactivation Tested batch and continuous
Advantages
• No cosolvents • Minimize methanol use
• Excellent conversion (98%+) • Good enzyme reuse
Disadvantages • Still has long reaction times • Still had high FFA at end of
process • Enzyme reuse still not
commercially viable
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Watanabe and Shimada (2001, 2005)
Packed
Bed
Reactors
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Watanabe and Shimada (2001, 2005)
Esterification – very fast!
Determined maximum methanol allowable before deactivation
• 6.3% by weight methanol
Performed Enzyme Reuse Trials • Excellent conversion (98%+)
• Good enzyme reuse
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Novozymes (2009)
Longevity trials: Esterification
Reaction Conditions • 20% by volume methanol, 2 stage
reaction, 45C, • Majority of reaction finished in 60
minutes • Blended FAME, MeOH, and PFAD to
address the high melting point
Still has deactivation
Relatively large excess methanol use (~2:1)
Still high FFA content (3 – 5%) after
2nd stage
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U.S. Dept. of Energy: Piedmont Biofuels – Commercial Focus
Esterification
Achieving ASTM specifications
Commercial viability (enzyme reuse)
Real World Feedstocks
• Yellow Grease (15% FFA) • Brown Grease (80%+FFA)
• Palm, soy, and others
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Enzymatic approach for Waste-Water Reduction
• Began investigation of enzyme catalysis for biodiesel, 2009
• Focus on esterification first • 2010---Lab working on Pilot scale (35 gal.) • 2011/2--- Pilot moving to Commercial • 2013---on-going Commercial Integration • Validation for multi-feedstock production scheme
• First to demonstrate enzyme biodiesel to meet full ASTM specification. • Economic analysis & Enzyme reuse
CSTR system with alcohol metering, patent pending
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Enzymes For Biodiesel Production
Commercial formulations: Callera series
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Commercial Build
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Feed Tanks
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How can you use this process? • Enzyma:c Esterifica:on: • A. Pretreatment for exis:ng chemical plants • B. Full conversion-‐-‐Esterifica:on for High FFA feedstocks
• C. Enzyma:c Polishing for TRANSESTERIFICATION followed by the enzyma:c esterifica:on PROCESS
• -‐-‐100% enzyme-‐based process in 2 steps
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Replace Sulfuric Acid Pretreatment • Esterification using Callera Ultra/L Immobilized CALB or Liquid CALB
• Replaces traditional sulfuric acid technology
• Incoming Feedstocks: 2-100% FFA • Patent Pending, continuous process
• Low temperature process
• Maintains water balance • 6-12 times less methanol than acid esterification
• No acidic methanol sidestream FAeSTER Process: Fatty Acid esterification
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Feedstock Pretreatment Esterification occurs quickly within 30 minutes
Achieves acid value specification by 90 minutes
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Liquid enzyme transesterification • Heat/Circulate Feedstock (42 gallons, 40ºC) • Initial Batches
– 1%-2% enzyme by feedstock weight – Aqueous Phase of 20% by feedstock weight
• 40% water • 60% glycerol
• Methanol Dosing – 1.7 molar excess of methanol to feedstock – 25% initial – Remainder metered in over 5 hours
• Sampling – 1, 2, 4, 6, 8, 10hr
• FAME Phase: Bound Glycerine & FFA – 24 hr
• Aq. Phase: Glycerol, Methanol, H2O, Enzyme – Determine Aq. Phase Removal & Methanol Dosing – Part II
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Pilot Scale Results
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Commercial scale Results
Reaction complete in 6-8 hours
In-spec Bound Glycerin 0.15% 1.5FFA%
2700 gallon reactor, coil-heated,
SS, cone-bottom, 35-40C/95-104F,
20% water/glycerol, 1.7:1 methanol:FA
Reaction monitored:
1, 2, 4, 6, 8 hrs.
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NOVOZYMES PRESENTATION 2/19/14 32
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Alkaline wash reduce free fatty acids and glycerides and make final biodiesel meet specifications.
The soap stock is acidified and sent back
NOVOZYMES PRESENTATION��� 2/19/14 33
0
0.5
1
1.5
2
2.5
3
Before CW AXer CW
% in FAM
E TG
DG
MG
FFA
BG = 0.17%
BG = 0.10%
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The enzyme works at the oil/water interface
Mixing is important – we need a an emulsion with a large surface area between oil and glycerin/water phases
NOVOZYMES PRESENTATION 2/19/14 34
Oil/FAME
Glycerin/water
Mixing
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NOVOZYMES PRESENTATION 2/19/14 35
Glycerides + MeOH glycerides/glycerin + FAME
Glycerides + H2O glycerides/glycerin + FFA
FFA + MeOH FAME + H2O
Driving process by
increasing Methanol and
decreasing Glycerol and Water
Reaction at interface
Enzyme process works well with any content of free fatty acids
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Affect of Water:
Too much water leads to reac:on with FAME back to FFA.
Too li\le water leads to enzyme inac:vity.
Affect of Methanol: Excess methanol inhibits the enzyme. Too li\le methanol slows reac:on.
Loss of Active Enzyme:
Loss of Enzyme = slower reac:on rate.
Balancing Act
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– 2010: ASTM D6751 achieved using only
immobilized enzymes
2011: ASTM D6751 achieved using Liquid
TL & CALB
2012 + : Commercial Scale
Integration
100% Enzyme-Based Fuel meets ASTM D6751
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Glycerol from Enzymatic Process
• High purity Glycerol 99.6%
• Economic Impact to the producer:
• 40-50 cents/lb. •
Chemical glycerol vs. enzymatic glycerol
Chemical FAME/glycerol vs. FAME/enzymatic glycerol YELLOW GREASE FEEDSTOCK
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2/19/14 39
Tsinghua China – Hunan plant Lipase-mediated industrial scale production of biodiesel (20,000t/y) put into operation Dec 8, 2006. Initially in a process with t-butanol; Now restarting in solvent free process
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NOVOZYMES PRESENTATION 2/19/14 40
Final product
Blue Sun - USA. 3 enzyme reactors of 300 m3 each
Started early 2013
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NOVOZYMES PRESENTATION 2/19/14 41
Viesel Biofuels – Florida USA
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Summary Variables
Methanol use (minimize) Cosolvents (minimize)
Reaction time (minimize) Presence of water (minimize)
Ester conversion per minute (minimize) Final ester conversion (minimum 98% esters)
Final FFA content (maximum 0.25% FFA) Temperature (35 – 50)
System design
PBR CSTR
Continuous Batch
System robustness
multi-feedstock tolerance to impurities
Enzymes as a biodiesel catalyst are extremely well studied
but also very complex.
Still, probably worth the effort...
Type of Enzyme Candida antarctica lipase B
Thermomyces lanuginosa Pseudomonas cepacia
Rhizomucor miehei
Carrier Polypropylene
Polyethylene Activated Carbon
Silica
Form of enzyme Liquid
Immobilized
Lower Energy Use
No Soap Formation
High Quality Glycerin
Non-Toxic Low Methanol Use
Scale Neutral More Complete
Separations Esterify and Transesterify
A more competitive biodiesel industry