Basic Chemistry of Biodiesel Production p resented at CCURI Biofuels Workshop

Basic Chemistry of Biodiesel Production

presented at

CCURI Biofuels WorkshopMuskegon Community College

Muskegon, MIOctober, 17 – 20, 2013

by

Chuck CrabtreeDirector – Iowa BioDevelopmentIndian Hills Community College

Ottumwa, IA

Topics1. What are the different types of oils?2. What are tryglicerides?3. Fatty acid structure.4. What are fatty acid profiles?5. What is esterification and transesterification?6. How does the fatty acid profile of the feedstock

affect biodiesel performance?7. What are some of the more common feedstocks

used for biodiesel production?

What is oil?

Introduction to Organic Oil Chemistry

• Three basic types: 1. Essential oils – Perfumes from plants

2. Mineral oils – Crude oil from petroleum

3. Organic oils – Animal and vegetable oils, soybean oil

– Are mixtures of hydrocarbons

– Are mixtures of triglycerides• Organic compound • Made up of carbon, hydrogen, and

oxygen

Different Types of Oils – Essential Oil


• A volatile oil (vaporizes at room temperature)

• Has a characteristic odor or flavor

• Generally obtained from a plant

• Used to make perfumes and flavorings

• Essential oils

Different Types of Oils – Petroleum


• Comes from the Earth• Is a mixture of a very large number of

different hydrocarbons• Refined into a variety of hydrocarbons

• Is a liquid by-product of the distillation of petroleum

• Includes lubricating base oils such as motor oil

• Crude oil or petroleum

• No oxygen in structure

• Only carbon and hydrogen

• Mineral oil


Characteristics of an Oil• Not soluble in water

• Soluble in organic substances like methanol

• Liquid at room temperature

• Fat and grease similar but solid at room temperature

Different Types of Oils – Organic


• Organic oils• Canola (Rapeseed)• Coconut• Corn oil• Flaxseed• Jatropha• Palm oil• Soybean oil• Sunflower oil• Waste vegetable oil (WVO)• Animal fats• Tallow – Usually cattle,

sheep, or horse fat• Lard – Usually hog fat

Biodiesel Molecular Structure

C

CC

CC

CC

CC

CC

C

H HH

HHHHHHHHHH H

HHHHHHHHH

H

Parts of Biodiesel Molecule


C

CC

CC

CC

CC

CC

C

H HH

HHHHHHHHHH H

HHHHHHHHH

H

• Methyl group Methyl Group



C

CC

CC

CC

CC

CC

C

H HH

HHHHHHHHHH H

HHHHHHHHH

H

• Methyl group

• Fatty acid

Fatty Acid

Methyl Group



C

CC

CC

CC

CC

CC

C

H HH

HHHHHHHHHH H

HHHHHHHHH

H

Parts of Biodiesel Molecule• Methyl group

• Fatty acid

• Have this structure

• Most naturally occurring organic oils are esters

CB

AFatty Acid

Methyl Group


Esters

FAME: Fatty Acid Methyl Ester


C

CC

CC

CC

CC

CC

C

H HH

HHHHHHHHHH H

HHHHHHHHH

H

Let’s simplify this a bit…


C

CC

CC

CC

CC

CC

C

H HH

HHHHHHHHHH H

HHHHHHHHH

H

• First, let’s replace the methyl group with an Me. Me



CC

CC

CC

CC

CC

CHHHHHHHHHH H

HHHHHHHHH

H

• First, let’s replace the methyl group with an Me.

• The H’s representing the hydrogens can be removed from the diagram since it is assumed they are there.

MeLet’s simplify this a bit…


CC

CC

CC

CC

CC

C



• The C’s representing the carbons can also be removed from the diagram since it is assumed they are there also.

MeLet’s simplify this a bit…




• The C’s representing the carbons can also be removed from the diagram since it is assumed they are there also.

• Make sure you know the methyl group and the fatty acid group.

Me

BiodieselFatty Acid Methyl Ester (FAME)


Fatty Acid StructureHCarbon Chain Length

• 1 carbon at every line intersection

• Highly variable, even from the same plant

Fatty Acid Structure

Carbon Chain Length Carbon #123456789

101112

H

• Remember – 1 carbon at every line intersection


• Usually from 12 – 18 carbons, can go up to 26 carbons

• Usually in even numbers of carbons


Carbon Chain Length Carbon #123456789

10111213141516171819202122

H

• Remember – 1 carbon at every line intersection


• Usually from 12 – 18 carbons, can go up to 26 carbons

• Usually in even numbers of carbons

• Biodiesel properties are determined partially by chain length


Carbon Chain Bonds

C

C

C

C

C

CC

C

C

C

C

COH

OHHHHHHHHHHHH

HH

HH

HH

HH

HH

H

• Single bonds between the carbons• Saturated – No double bonds


Carbon Chain Bonds

C

C

C

C

CC

C

C

C

COH

OHHHH

HHHHHH

HH

HH

HH

HH

H

CC

H

H


• Double bonds between the carbons• Unsaturated – Containing

any double bonds• Monounsaturated – Containing 1

double bond


Carbon Chain Bonds

C

C

CC

C

C

COH

OHHHH

H

HHH

HH

HH

HH

H

CC

H

HC

CC


• Double bonds between the carbons• Unsaturated – Containing

any double bonds• Monounsaturated – Containing 1

double bond• Polyunsaturated – Containing

more than 1 double bond

• Biodiesel properties are determined partially by chain bonds


Carbon Chain Bonds

C

C

CC

C

C

COH

OHHHH

H

HHH

HH

HH

HH

H

CC

H

HC

CC

• Carbon can only make four connections or bonds• No double bonds = two

hydrogens

• Two double bonds = no hydrogens

• One double bond = one hydrogen

Basic Organic Oil Chemistry

The basic units of most naturally occurring organic oils are:

When 3 fatty acids bond with 1 glycerin molecule, you get a:• Triglyceride

• Glycerin• Fatty acids

The basic units of most naturally occurring oils are:

When 2 fatty acids bond with 1 glycerin molecule, you get a:

H


• Triglyceride• Diglyceride



When 1 fatty acids bond with 1 glycerin molecule, you get a:

H H


• Triglyceride• Diglyceride• Monoglyceride



When fatty acids are not bound to anything, you get:

H H H



• Triglyceride• Diglyceride• Monoglyceride• Free fatty acids – FFA

Fatty Acid Structure DesignationsFatty Acid Structure

• General Format: A:B• A is the number of carbons in the fatty acid chain• B is the number of double bonds in the fatty acid

chain

Fatty Acid Structure Designations

16:0(saturated)

Fatty Acid Structure• General Format: A:B• A is the number of carbons in the fatty acid chain• B is the number of double bonds in the fatty acid

chainExample: Fatty acid with 16 carbons and 0 carbon to carbon double bonds (palmitic acid)


16:0(saturated)

18:2


Example: Fatty acid with 18 carbons and 2 double bonds (linoleic acid)



(polyunsaturated)


16:0(saturated)

18:2

16:1 (monounsaturated)


Example: Fatty acid with 16 carbons and 1 double bonds (palmitoleic acid)

Example: Fatty acid with 18 carbons and 2 double bonds (linoleic acid)



(polyunsaturated)

Fatty Acid ProfileFatty Acid Profile

18:2

16:0

18:1

= 75 % unsaturated

• Specific types of vegetable oils contain specific percentages of different fatty acids.

• Important characteristics of the fatty acids:

1) The percentage of fatty acids of different lengths, and:

2) Percent of saturation/unsaturation

Example:• Soybean oil• 11% - 16:0• 4% - 18:0• 24% - 18:1• 54% - 18:2• 7% - 18:3

Fatty Acid ProfileFatty Acid Profile

18:2

16:0

18:1

= 92 % saturated

• Important characteristics of the fatty acids:

1) The percentage of fatty acids of different lengths, and:

2) Percent of saturation/unsaturation

Example:• Coconut Oil• 7% - 8:0• 6% - 10:0• 47% - 12:0• 18% - 14:0• 9% - 16:0• 3% - 18:0• 6% - 18:1• 2% - 18:2

Fatty Acid Composition of Vegetable Oils (percent of total fatty acids)

Fatty Acid Profiles

Vegetable Oil 8:0 10:0 12:0 14:0 16:0 18:0 18:1 18:2 18:3

Canola (rapeseed) Oil

4 2 62 22 10

Coconut Oil 7 6 47 18 9 3 6 2

Corn Oil 11 2 28 58 1

Flaxseed Oil 3 7 21 16 53

Jatropha 15 7 41 37

Palm Oil 1 45 4 40 10

Palm Kernel Oil 3 3 48 16 8 3 15 2

Soybean Oil 11 4 24 54 7

Sunflower Oil 7 5 19 68 1

Fatty Acid Composition of Vegetable Oils (percent of total fatty acids)

Vegetable Oil Saturated Monounsaturated Polyunsaturated

Canola (rapeseed) Oil 6 62 32

Coconut Oil 90 6 2

Corn Oil 13 28 59

Flaxseed Oil 10 21 69

Jatropha 22 41 37

Palm Oil 50 40 10

Palm Kernel Oil 81 15 2

Soybean Oil 15 24 61

Sunflower Oil 12 19 69

Fatty Acid Profiles

Animal Fat Fatty Acid Profile

Animal Fat 8:0 10:0 12:0 14:0 16:0 18:0 18:1 18:2 18:3

Tallow 3 25 20 40 3 1

Lard 2 25 16 42 11 1Poultry 1 23 8 45 17 1

Animal Fat Saturated Monounsaturated Polyunsaturated

Tallow 50 42 4

Lard 42 46 11

Poultry 31 51 18

http://www.iterg.com/IMG/pdf/CompositionAcidesGrasGraissesHuilesAnimales.pdf

http://www.iterg.com/IMG/pdf/CompositionAcidesGrasGraissesHuilesAnimales.pdf

Fatty Acid Profiles

Waste Vegetable Oil (WVO)

Fatty Acid Profiles

• Can make excellent biodiesel

• Challenges• Inconsistent composition

• High level of free fatty acids, especially when heated beyond 300 ºF and/or exposed to water

• Can be semi-solid at room temperature

Transesterification

• Big word, simple principle

• Word breakdown

• The exchange is catalyzed by potassium hydroxide, KOH.

• Again, the specifics of the chemical reactions are beyond the scope of this course, but the principle isn’t.

What is transesterification?

• Trans means “transferred or exchange.”• Ester means exactly that…ester.• Transesterification means to exchange the organic group

on an ester with another organic group.• Here the exchange is the glycerin on the fatty acids with

the methyl group from the alcohol, methanol.

TriglycerideMolecule

MeOHMeOH

Transesterification

MeOH

MethanolMolecules

KOH KOH KOH

MeOH

MeOH

TriglycerideMolecule

MeOHMeOH

Transesterification

MeOH

MethanolMolecules

Glycerin

Biodiesel(FAME)

KOH KOH KOH

MeOH

MeOH

Transesterification

OilMethoxide

Triglyceride

Transesterification

OilMethoxide

MeMeMe

Glycerin

Biodiesel

KOH

Triglyceride

H HH

Transesterification

OilMethoxide

Glycerin

Biodiesel

Me Me Me

Biodiesel

Glycerin

H HH

Summary• Various types of oils can be used.• Some require preprocessing before transesterification.• Most oils are triglycerides which contain glycerin and fatty

acids.

• Contains methanol and potassium hydroxide (KOH).• Methanol provides methyl group.• KOH is a catalyst for the transesterification reaction.

• Trans means “transferred or exchange.”

• Exchanges the glycerin on the fatty acids with the methyl group from the alcohol, methanol.

• Leaves glycerin and fatty acid methyl esters (FAME) or biodiesel.

Transesterification

Feedstock

Methoxide Solution

Feedstock Pretreatment

Pretreatment of Crude Vegetable OilCrude vs. Refined Vegetable Oil

• Crude – Triglycerides, plus:• Free fatty acids• Phospholipids (gums)• Oxidation• Metals• Protein• Carbohydrate residues• Waxes• Moisture• Inorganic matter

• Refined: Nearly pure triglycerides• <0.5% FFA


Pretreatment of Crude Vegetable Oil• Degumming – Removing the phospholipids, waxes, and

neutralizing the FFA)• First step in the vegetable oil refining process

• Water – Causes some of the phospholipids and waxes to become insoluble in oil; separated via centrifuge

• Acid – Used to extract remaining phospholipids and waxes

• Base – Converts free fatty acids to soap and then removed via centrifugation or settling


Pretreatment of Crude Vegetable Oil• Bleaching – Removal of trace metals, phospholipids, soaps,

and other contaminants• Activated clay or silica

• Deodorizing – Removal of trace FFA, pigments and other contaminants• Steam (210º C to 260º C)


Pretreatment of WVO• Removal of solids and water• Solids removed via centrifugation and filtering• Water removed by heating (65º C) under vacuum


Pretreatment of High FFA FeedstocksH• FFA >0.5%

• WVO• Animal fats• Palm oil• Jatropha oil

• Why are free fatty acids in the oil a problem?• They use up the catalyst, so more catalyst is

needed.• They produce soap during transesterification.


Pretreatment of High FFA Feedstocks

Difference Between Esterification and Transesterification

• Esterification: A chemical reaction resulting in the formation of an ester• Converts FFA to FAME before transesterification can

convert the FFA to soap• Catalyst: Acid instead of base (usually sulfuric acid)• Methanol

• Esterification: Converts a non-ester into an ester(e.g. FFA to FAME)

• Transesterification: Converts an ester to a different ester(e.g. Triglyceride to FAME)


MeOHMeOH

MeOH

MethanolMolecules

MeOH

MeOH

Free Fatty Acids

Water

Biodiesel (FAME)

H2SO4

H2SO4

HH

H2SO4

Transesterification

Catalyst Methanol

Oil

Transesterification

KOHor

NaOHAnhydrous

Dried refined or preprocessed oil

Methoxide

FA Structure Effect on Biodiesel Properties

Cetane Number (CN)• Similar to the octane number used for gasoline• Indicator of fuel quality

• Ignition Delay (ID)

• Low ID = High CN

• Fatty Acid Structure Effects

• Time that passes between injection of the fuel into the cylinder and actual ignition of the fuel

• A low ID is desirable.

• High CN is desirable.

• CN increases with carbon chain length.• CN decreases with increasing unsaturation (more double

bonds).


Gross Heat of Combustion (HG)• Measure of the energy produced when combusted

• High HG is desirable.

• Fatty Acid Structure Effects• HG increases with carbon chain length.• HG decreases with increasing unsaturation (more

double bonds).


Cold Flow Properties• Cloud Point (CP)

• A low CP is desirable.

• Fatty Acid Structure Effects

• Temperature at which biodiesel becomes cloudy due to crystal formation

• CP increases with carbon chain length.• CP decreases with increasing unsaturation (more double

bonds).


Oxidative Stability• Measure of the tendency to oxidize, or

break down• Important measurement for fuel storage

• A high oxidative stability is desirable.

• Fatty Acid Structure Effects• Oxidative stability decreases with increasing

unsaturation (more double bonds).


Cetane Number

Heat of Combustion

Cold Flow Properties

Oxidative Stability

Increasing Carbon Chain N/A

Increasing Unsaturation

FA Structure Effect on Biodiesel Properties – SUMMARY

Biodiesel Feedstocks

• Major Oil Sources for Biodiesel Fuel• Soybean oil• Palm oil• Canola oil• Coconut oil• Corn oil• Flaxseed oil• Sunflower oil• Jatropha oil

• Vegetable Oils

• Other Oils• Animal fats• Waste vegetable oil • Algae


• Stability• Stability – “Resistance to chemical

change or to physical disintegration.” (Websters)

• Different feedstocks contain different kinds of fatty acids.

• Some fatty acids are more stabile than others.

• Biodiesel stability is defendant on the feedstock from which it was made.


Cold Flow Properties• Cold Flow Properties – Properties of a

substance that influences its ability to flow at colder temperatures.

• Different feedstocks contain different kinds of fatty acids.

• Some fatty acids have better cold flow properties than others.

• The cold flow properties of biodiesel are dependent on the feedstock from which it was made.


Soybean

• China• United States• Argentina• Brazil• European Union

• Top five producing countries

• Leading source of vegetable oil in the world

• Oil comes from the bean (~18%)

• Biodiesel – Less stabile than some but good cold weather properties

• Major feedstock in the U.S. (90%)


Palm• Top five producing countries

• Second leading source of vegetable oil in the world

• Oil comes from the kernel and the pulp of the fruit (~40%)

• Biodiesel – Highly stabile

• Not a major feedstock in the U.S.

• Indonesia• Malaysia• Thailand• Columbia• Nigeria

• Canola Oil (Rapeseed)


• European Union (mostly in Germany)• China• Canada• India• Japan


• Third leading source of vegetable oil in the world

• Oil comes from the seed (~30%)

• Biodiesel has good cold flow properties

• Most significant feedstock in Europe



Coconut

• Philippines• Indonesia• India• Vietnam• Mexico


• Oil comes from coconut meat (~35%)

• Very different composition than other vegetable oil

• Biodiesel has high stability but poor cold weather properties


Corn



• Oil comes from corn kernel (3% - 8%)

• Biodiesel – Less stabile than soy biodiesel


• United States• China• European Union• Brazil• Argentina


Sunflower• Top five producing countries

• Oil comes from the seed (~40%)

• Biodiesel – Less stabile than some but good cold weather properties


• Russia• European Union• Ukraine• Argentina• Turkey

Flax



• Oil comes from seeds (~35%)

• Biodiesel – Poor stability but good cold flow properties


• Canada• China• India• United States• Ethiopia

Jatropha


• Non-food crop

• Found in almost all tropical and sub-tropical countries

• Drought resistant, grows well on marginal lands

• Oil comes from seeds (~37%)

• Biodiesel – Similar to soy biodiesel


• Animal Fats


• Tallow – Beef fat• Lard – Pork fat• Poultry fat

• Source: Meat processing plants

• Must be preprocessed prior to transesterification – Free fatty acid content as high as 30%

• Biodiesel properties similar to biodiesel from coconut and palm oil – more stabile and poorer cold weather characteristics

• Waste Vegetable Oil (WVO)Biodiesel Feedstocks

• Oil used for cooking

• Source: Restaurants, cafeterias

• Must be preprocessed prior to transesterification – Free fatty acid content generally less than 15%

• FFA % dependent on temperature

• Water content

• Solids

• Biodiesel properties vary

• Algal OilsBiodiesel Feedstocks

Oil Crop Gallons/acre/year

Soybeans 48

Rapeseed 127

Jatropha 435-2,000

Algae 5,000-15,000

• Would require only 2% of the current cropping acres in the USA to supply all U.S. transport needs

• Can be grown in:• Ponds• Microalgae tubes/reactors

• Up to 60% oil

• Production, harvest and oil extraction challenges still exist.

• Major Oil Sources for Biodiesel Fuel


• Soybean oil• Palm oil• Canola oil (Rapeseed)• Coconut oil• Corn oil• Flaxseed oil• Sunflower oil• Jatropha oil

• Vegetable Oils

• Other Oils• Animal fats• Waste vegetable oil • Algae

Sources of InformationHandbook of Biofuels Production, Fifth Edition, R. Luque, J.

Campelo, and J. Clark eds. Woodhead Publishing Limited, Cambridge, UK, 2011.

Dependence of Biodiesel Fuel Properties on the Structure of Fatty Acid Alkyl Esters, G. Knothe, Fuel Processing Technology 86:1059-1070, 2005.

Fat, Oils, Fatty Acids, Triglycerides – Chemical Structure, Antonio Zamora, Scientificpsychic.com, 2004.

Biodiesel Production from Crude Jatropha curcas L. seed oil with a High Content of Free Fatty Acids, H. J. Berchmans and S. Hirata, Bioresources Technology, 99:1716-1721, 2008.

Transesterification of Vegetable Oils: A Review, U. Schuchardt, R. Sercheli, and R. M. Vargas. Journal of the Brazilian Chemical Society, 9:199-210, 1998

Documents

Basic Chemistry of Biodiesel Production p resented at CCURI Biofuels Workshop