Upload
theodora-young
View
214
Download
0
Tags:
Embed Size (px)
Citation preview
Basic Chemistry of Ethanol Production
presented at
CCURI Biofuels WorkshopMuskegon Community College
Muskegon, MIOctober, 17 – 20, 2013
by
Chuck CrabtreeDirector – Iowa BioDevelopmentIndian Hills Community College
Ottumwa, IA
Topics
1. What are carbohydrates?
2. What is glucose?
3. Why is glucose important?
4. What is starch?
5. What is cellulose?
6. How are the structures of starch and cellulose similar and how are they different?
7. How is starch used to make ethanol?
8. How is cellulose used to make ethanol?
9. What are some of the more common feedstocks used for ethanol production?
Carbohydrates – Starch and Cellulose
What is a carbohydrate?• Organic compounds that contain only carbon,
hydrogen, and oxygen
What do carbohydrates do?• Store energy (food) – starch (corn, potatoes)• Structural – cellulose (plant stems, wood)
Basic component of both starch and cellulose?• Glucose
= Oxygen
= Carbon
Glucose Basic Structure
= Hydrogen
Glucose Basic Structure
= Oxygen
= Carbon
= Oxygen
= Carbon
Glucose Basic Structure
1
2
4
3
6
5
Glucose Basic Structure
Glucose – Important Facts
• Also called “fermentable sugar,” “dextrose,” “corn sugar” or “sugar”
• Used by biological systems as food
• It is a “monomer” – Mono means “one” or “single.”
• Starch is a “polymer” – Poly means “many.”
What is a monomer?• One unit of a string of units
Monomers
What is a monomer?• One unit of a string of units
• Example: Pearl necklace• If a monomer is 1 unit of a
string of units, then what is the monomer of a pearl necklace?
Monomers
What is a monomer?• One unit of a string of units
• Example: Pearl necklace• If a monomer is 1 unit of a
string of units, then what is the monomer of a pearl necklace?
• A pearl!
Monomers
What is a polymer?• A string of similar units
Polymers
What is a polymer?• A string of similar units
• Example: Pearl necklace• If a polymer is a string of
similar units, then what is the polymer of a pearl?
Polymers
What is a polymer?• A string of similar units
• Example: Pearl necklace• If a polymer is a string of
similar units, then what is the polymer of a pearl?
• A pearl necklace!
Polymers
• The pearl is a monomer– When connected with
other pearls they make a polymer called a pearl necklace
• Same principle applies to chemicals– Glucose is a monomer– When connected with
other glucose molecules they make a polymer called starch or cellulose
Monomers and Polymers
Starch is a polymer• > 500 glucose units • Two types of starch
Starch is a polymer• > 500 glucose units • Two types of starch
• Amylose – straight chains
Starch is a polymer• > 500 glucose units • Two types of starch
• Amylose – straight chains• Amylopectin – branched chains
Starch vs. Cellulose Structure
Starch Structure
1
3 2
4
5
6
1
3 2
4
5
6
1
3 2
4
5
6
1
3 2
4
5
6
Cellulose Structure
1
3 2
4
5
6
1
3 2
4
5
6
1
3 2
4
5
6
1
3 2
4
5
6
Cellulosic Structure
Cellulose Structure
GlucoseMolecule
Cellulosic Structure
Cellulose Structure
GlucoseMolecule
IndividualCelluloseMolecules
Cellulosic Structure
Cellulose Structure
IndividualCelluloseMolecules
GlucoseMolecule
Cellulosic Structure
Cellulose StructureCelluloseMicrofibril
IndividualCelluloseMolecules
GlucoseMolecule
Lignin
Cellulosic Structure
Cellulose Structure
IndividualCelluloseMolecules
GlucoseMolecule
CelluloseMicrofibrils
CelluloseFiber
Non-cellulosePolysaccarides
Lignin
Lignin Structure
• Very complex structure
• Second most common molecule on earth.
• Lacks a defined structure
• Fills the spaces between cellulose
Hemicellulose Structure
• Enzymes are proteins that speed up chemical reactions, but are not altered themselves (catalysts)
Enzymes
• Enzymes are proteins that speed up chemical reactions, but are not altered themselves (catalysts)
Enzymes
• Enzymes are proteins that speed up chemical reactions, but are not altered themselves (catalysts)
Enzymes
• Enzymes are proteins that speed up chemical reactions, but are not altered themselves (catalysts)
Enzymes
Reaction can go either way
Glucose Linkages and Enzyme Active Sites
Glucose Linkages and Enzyme Active Sites
Glucose Linkages and Enzyme Active Sites
Glucose Linkages and Enzyme Active Sites
1
23
4
5
6
Named for the way two glucose molecules are attached to each other.
Glucose Linkages and Enzyme Active Sites
1
23
4
5
6
1,6 linkage1,4 linkage
Amylopectin – Branched Starch Molecule
Amylopectin – Branched Starch MoleculeIntroducing the enzyme α-amylase.
Amylopectin – Branched Starch MoleculeIntroducing the enzyme α-amylase.
α-amylase breaks down starch into shorter glucose chains called “dextrins.”
Breaks 1,4 linkages that are not terminal.
Dextrins
Dextrins
Dextrins
Amylopectin – Branched Starch MoleculeIntroducing the enzyme α-amylase.
α-amylase breaks down starch into shorter glucose chains called “dextrins.”
Breaks 1,4 linkages that are not terminal.
Dextrins
Dextrins
Dextrins
Introducing the enzyme glucoamylase.
Glucoamylase breaks down dextrins into individual glucose molecules.
Acts on 1,4 and 1,6 terminal linkages.
Introducing the enzyme glucoamylase.
What about Cellulose
Since starch and cellulose are glucose polymers, why is cellulose so much harder to break down into glucose?
So how do we get through the other stuff to get to the cellulose?
Once we get to the cellulose, will the same enzymes work?
Cellulose Pretreatment Options
Physical Breakdown (heat/pressure, grinding, chopping, sonication)
Weak Caustic (NaOH, Ammonia)
Weak Acid (Sulfuric, HCL)
Heat with caustic and acid
Pressure and heat with caustic and acid
Enzymatic cocktails (cellulases, zylases, gluconases, ligases, hemicellulases, etc). Usually used after at least one of the above.
Time can vary on all of these.
Cellulose as Other Forms of Fuel
Straight Combustion – Most common
Pyrolysis (bio-oil)– Usually high temps and pressures. Some low temp technologies.
Syngas – Gasification of organic material at high temps (without combustion) with oxygen and steam to produce CO, H, and CO2
Ethanol Feedstocks
Feedstocks
Three Types of Feedstocks• Starch-rich feedstocks• Sugar-rich feedstocks• Cellulosic feedstocks
Sugar Cane
Cellulose Corn
Starch-Rich Feedstocks
Two Types of Starch-rich Feedstocks
• Tubers• Cassava• Potato
• Cereal grains• Corn• Wheat• Barley• Rye• Grain Sorghum• Triticale
Potato
Barley
Triticale
Cassava
Sorghum
WheatCorn
Starch-Rich Feedstocks
Tubers• Cassava• Potato
PotatoCassava
Starch-Rich Feedstocks
Cereal Grains• Wheat• Barley
Barley
Wheat
Starch-Rich Feedstocks
Cereal Grains• Rye• Grain Sorghum• Triticale
Rye
Grain Sorghum
Triticale
Sugar-Rich Feedstocks
Three Primary Sources• Sugar Cane• Sugar Beets• Sweet Sorghum
Sugar Cane
Sugar BeetsSweet Sorghum
Sugar-Rich Feedstocks
Different process than for starch-rich feedstocks.
Sugar Feedstock Process
• Washing• Breaking• Milling• Straining• Clarification• Evaporation• Mash Preparation• Fermentation• Distillation/Dehydration
Starch Feedstock Process
• -• -• Milling• -• -• -• Mashing/Cooking/Liquifaction• Fermentation• Distillation/Dehydration
Sugar juice/syruppreparation
Sugar-Rich Feedstocks
Sugar Cane
Sugar-Rich Feedstocks
Sugar BeetsSweet Sorghum
Sweet Sorghum
Sugar Beets
Cellulosic Feedstocks
Cellulose• What is it?
• General term – Biomass• Straight chain polymer of
glucose molecules• Used by plants in cell walls
Wood Chips
Hay
Cellulosic Feedstocks
Cellulose
• Where does it come from?• Plant material• Wood• Grasses (e.g.,
switchgrass)• Crop residue (e.g., corn
stover)
Cellulosic Feedstocks
Cellulose
• Where does it come from?• Plant material• Wood• Grasses (e.g.,
switchgrass)• Crop residue (e.g., corn
stover)
• Advantages• No food vs. fuel issues• Worldwide distribution• High glucose density
Cellulosic Feedstocks
Cellulose
• Where does it come from?• Plant material• Wood• Grasses (e.g.,
switchgrass)• Crop residue (e.g., corn
stover)
• Advantages• No food vs. fuel issues• Worldwide distribution• High glucose density
• Disadvantages• Difficult to breakdown• Bulky
Sources of Information
The Alcohol Textbook, Fifth Edition, W.M Ingledew, D. R. Kelsall, G. D. Austin and C Kluhspies, eds. Nottingham University Press, Nottingham, UK, 2009.
Portaria Nº 143, de 27 de Junho de 2007 (in Portuguese). Ministério da Agricultura, Pecuária e Abastecimento. Retrieved 2008-10-05. This decree fixed the mandatory blend at 25% starting July 1st, 2007
Luiz A. Horta Nogueira (2004-03-22). "Perspectivas de un Programa de Biocombustibles en América Central: Proyecto Uso Sustentable de Hidrocarburos" (in Spanish) (PDF). Comisión Económica para América Latina y el Caribe (CEPAL). Retrieved 2008-05-09.
UNICA: venda de veículos flex no Brasil cresce 13,9% em 2009 e frota ultrapassa 9 milhões de unidades (in Portuguese). UNICA. 2010-01-11. Retrieved 2010-02-09.