Lesson 5: Bioethanol and Biodiesel

PART 1: Bioethanol and Biodiesel

About bioethanol:

  • produced from fermentation of glucose
  • glucose is found in the fruit flesh and hence, the glucose found in the flesh can be used to make bioethanol
  • the fruit peel contains cellulose which can also be fermented to ethanol because both cellulose and glucose are made up of glucose monomers, the only difference is in the way they are linked.

Fermentation:

fer

Conditions:

  • presence of yeast
  • anaerobic surroundings
  • room temperature

Fractional Distillation can then be done to separate ethanol (b.p: 78 degree Celsius) and water (b.p: 100 degree Celsius).

From Vegetable Oil to Biodiesel

  • vegetable oil molecules are three times as large as biodiesel molecules
  • as such, there is a need to break up the large molecules into 3 smaller molecules because large molecules are inefficient as fuels. Amount of energy yield from large fuels is low due to high mass.
  • vegetable oils are esters with 3 fatty acids bonded to glycerol ie. vegetable oils are triglycerides
  • fatty acids are carboxylic acids with a long carbon chain (to be specific, fatty acids have a carbon chain 18 carbons long)

triglyc

  • When the triglyceride is broken up, the ester linkages are broken, and 3 fatty acids and 1 glycerol molecule will be formed as the product
  • vegetable oils undergo transesterification (transforming one ester into another) to form biodiesel
  • concentrated sulfuric acid is needed for transesterification

Procedure

  1. Determine the mass of a clean, dry 250mL conical flask. Measure 100.0mL of vegetable oil using a measuring cylinder and add it to the flask. Record the exact mass of vegetable oil.
  2. Add the stirrer bar to the mixture and place the flask on the hot plate. Start heating the mixture to about 55-go degree Celsius while stirring.  1384344_739485129401748_245898195_n
  3. In a separate flask, add 20.0mL of methanol and the appropriate amount of NaOH catalyst. Carefully swirl or stir the flask until the NaOH has dissolved. Important ratios: Methanol : Oil : Catalyst is 2: 10: 1. 994608_739485196068408_2076620942_n
  4. Add the methanol/NaOH mixture to the warm oil in 8 5 minute intervals until the mixture has reacted for 45 mins. Make sure the temperature does not rise too much.
  5. At the end of the reaction, separate the mixture in a separating funnel. 1377049_739485252735069_2046887304_n
  6. Add 10mL of 0.1 M acetic acid to the biodiesel in the separating funnel. Stopper tightly and invert gently 5 times. Then, allow the two layers to separate again (biodiesel is the least dense solution out of all the other solutions and hence will float on top) and collect the top yellowish layer in a beaker.
  7. Repeat the extraction step using 10mL of distilled water
  8. Pour the washed biodiesel through the top of the separating funnel into a dry, pre-weighed 100mL beaker. Place the sample in a water bath for 10-15mins to evaporate residual water as residual water will inhibit the igniting of the biodiesel later.                                                                       1395840_739485296068398_754340378_n
  9. Obtain the mass of the dry biodiesel.                     1384392_739485329401728_345364280_n

Concept behind experiment

  • when heated at high temperatures in the presence of water from food, the triglycerides in vegetable oil begin to break down by a chemical reaction called hydrolysis, producing fatty acids and glycerol
  • Base catalyst NaOH catalyzes reaction between fatty acid and methanol to form esters
  • Fatty acids will react with methanol to form methyl esters (Note: transforming the triglyceride (triester) into a methyl ester. Hence TRANSesterification).
  • Methyl esters are thus, the main components of Biodiesel and are the compounds burnt to produce energy

biodieselproduction1

Importance of washing the biodiesel

  • if the biodiesel is not washed properly, the contaminating ethanol could create a fire hazard and other contaminants will negatively affect combustion and engine performance
  • If water is not remove properly, the water will later react with the vegetable oil in the reaction and make soap which then complicates the steps after the transesterication reaction that are needed to separate the biodiesel from leftover methanol, the NaOH or KOH catalyst, and the glycerol byproduct.

Advantages of Biodiesel

  • non-toxic
  • renewable
  • less greenhouse gases produced
  • less expensive compared to other forms of liquid fuel

Disadvantages

  • accelerate rate of deforestation as forests are cleared to grow plants for biodiesel
  • usage of food crops to make the fuel

PART 2: Testing the Efficiency of Fuels

Fuel efficiency: using the least amount of fuel to travel the greatest distance

Importance of Fuel Efficiency

  • saves money
  • reduces climate change
  • reduces dependency on oil/fossil fuels
  • increases energy sustainability

Factors affecting fuel efficiency

  • weight/mass of a vehicle
  • engine design
  • vehicle design
  • vehicle maintenance

Today’s vehicles

  • only 15% of energy from fossil fuel move the vehicle or run accessories. The rest if lost to heat and exhaust

Calculating fuel efficiency

  • units: miles per gallon
  • Amount of heat released when fuel is burnt is equal to the amount of heat used to change the temperature of water. Amount of heat can be found by the following equation: Thermal energy (Q) = mass of water (m) x specific heat capacity of water (c) x change in temperature of water (ΔΘ)
  • using the calculated thermal energy, we can divide this by the number of moles of fuel that was combusted

Procedure

  1. Place a small wad of cotton in a crucible.
  2. Measure 10mL of cyclohexane using a measuring cylinder. Pour the cyclohexane onto the cotton wool in the evaporating dish. Determine the mass of cyclohexane used.
  3. Measure 10mL of water into a 25mL beaker and record the initial temperature of the water. Use a retort stand to hold the beaker in place directly above the crucible.
  4. Using a lighted splint, set fire to the cyclohexane.
  5. Immediately start the stopwatch and note the final temperature at the end of 2 minutes.                                                                 1391534_739484916068436_1248353283_n
  6. Repeat the above steps for methanol

Calculations

Fuel used

Temperature of water/ oC

Density of Fuel (g/ml)

Mass of fuel used/g

(density x 10ml)

Duration/mins

Initial

Final

Cyclohexane

31.0

75.0

0.7781

7.781

2

Methanol

31.0

100

0.7918

7.918

<2

B46276D1-EA79-4353-BE30-F83B1613D244 (1)

Note that Q is calculated by the following formula: Thermal energy (Q) = mass of water (m) x specific heat capacity of water (c) x change in temperature of water (ΔΘ)

From the above calculations, we can conclude that cyclohexane is a more efficient fuel than methanol, as it releases 19.9J of energy per mole burnt while methanol only releases 11.7J. Such results reinforce the fact that alkanes are better fuels than alcohols, as the combustion of alkanes is more exothermic, thereby releasing more energy than alcohols when burnt.

Assumptions

  • heat transfer is to water ONLY
  • 1mL of all aqueous solutions equal to 1g

Source:

Campbell Biology 9th edition Chapter 5 Page 119

http://www.goshen.edu/chemistry/biodiesel/chemistry-of/

Lesson 4: Bio Fuels and D-Limonene

About D-Limonene

  • unsaturated hydrocarbon with 2 carbon-carbon double bonds
  • chemical formula C10H16
  • has anti carcinogenic properties
  • used in numerous cleansing products
  • can be used as fuel
  • has aromatic properties

About Steam Distillation

  • oldest form of essential oil extraction
  • process does not denature structure of essential oil molecules
  • hot steam opens pockets in which the oils are kept and release the aromatic molecules from the fruit peels
  • molecules of these volatile oils then escape from the fruit peels and vaporise before condensing

Procedure

  1. Using a grater, grind only the coloured part of the peel of 4 medium-sized oranges into a beaker. Record the total mass of the grated orange rind. Image
  2. Add about between 50 and 150 mL of distilled water to the orange rind and transfer the mixture to a 250mL round-bottom flask.
  3. Set up the distillation apparatus as shown below. Image
  4. When the thermometer reads 50 degree Celsius, turn on the condenser water. The distillate containing D-Limonene will be collected in the conical flask
  5. Collect about 40mL of distillate before switching off the hot plate
  6. Transfer the distillate to a boiling tube and place it in the water bath for about 5 minutesImage
  7. When the boiling tube is removed from the water bath, 2 layers of liquid can be seen. The top layer is the product, limonene. There will also be a very strong smell of orange that can be smelt.

Note: A solution contaning D-limonene will decolourise bromine water because it is an alkene! 

Image

Concept behind Experiment

  • When water is added, D-limonene dissolves in it
  • During distillation, the water evaporates/boils, thus carrying the D-limonene molecules along with it
  • The water condenses and so does the D-limonene, which is collected in the distillate, giving rise to the aroma
  • D-limonene is less dense and hydrophobic, hence, it floats above the layer of water
  • To obtain greater purity, one should add less water and heat the solution slower

Calculations:

Mass of orange peels: 75.72 g

Amount of distillate obtained: 39.7 g

%yield=(75.72/39.7) x 100% = 52.4%

Unable to calculate purity because we did not take volume of essential oil we extracted. However, since purity and yield are inversely proportionate to each other, considering that we obtained such a high yield compared to the other groups, plus the fact that the aromatic scent our extracted D-limonene gave off was not as strong, we concluded that we did not obtain a high percentage purity of D-limonene.

Interesting Fact!

Limonene is a chiral molecule with two optical isomers (enantiomers). The major biological form d-limonene, the (R)-enantiomer, is used in food manufacture and medicines. It is also used as a fragrance in cleaning products, a botanical insecticide, and due to its flammability, a potential biofuel.
The (S)-enantiomer, l-limonene, is also used as a fragrance but has a piney, turpentine odour.

Sources:

http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/000/770/cfns%20experiment%2011%20-%20extracting%20limonene%20from%20oranges%20by%20steam%20distillation.pdf

Photo taken from:

http://www.reading.ac.uk/web/FILES/chemistry/Limonene.pdf

Lesson 3: Making Biopaper

Procedure:

  1. Place shredded paper into beaker
  2. Add 2x mass of water into beaker. Mix them thoroughly Image
  3. Place the mixture into a blenderImage
  4. Place the pulp into a water trough
  5. Add 6x mass of water to the pulp. Mix them thoroughly
  6. Use the mold to scoop up the pulp and allow water to drain offImage
  7. Place a cloth under the mould and allow it to dry for 24 hours Image

Concept behind the Making of Biopaper

After the papers are blended, placed in water and scooped out by the mold, the water is drained so that a mat of randomly interwoven cellulose fibers is laid down. As the water evaporates, the interwoven fibers become stronger and hydrogen bonds, permanent dipole-permanent dipole and instantaneous dipole-induced dipole attractions between fibers also hold the fibers together, thereby creating biopaper.

Advantages of Biopaper:

  • save more trees and forests, which are important to us (the air we breathe) and animals who live there
  • sustainable
  • reduce greenhouse gas emissions
  • keeps landfill space free for other materials that cannot be recycled

Limitations:

  • Paper recycling has its limits. Every time paper is recycled, the fiber becomes shorter, weaker and more brittle. In general, paper can be recycled up to seven times before it must be discarded.

Sources:

http://en.wikipedia.org/wiki/Papermaking

http://environment.about.com/od/recycling/a/The-Benefits-Of-Paper-Recycling-Why-Recycle-Paper.htm

Lesson 2: Green Plastics and 12 Principles of Green Chemistry

12 Principles of Green Chemistry:

1. It is better to prevent waste than to treat or clean up waste after it is formed

2. Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product

3. Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment

4. Chemical products should be designed to preserve efficacy of function while reducing toxicity

5. The use of auxiliary substances should be made unnecessary whenever possible and innocuous when used

6. Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure

7. A raw material or feedstock should be renewable rather than depleting wherever technically and economically practicable

8. Reduce derivatives – Minimize or avoid unnecessary derivatization if possible, which required additional reagents and generates waste

9. Catalytic reagents are superior to stiochiometric reagents

10. Chemical products should be designed so at the end of their function they do not persist in the environment and break down into innocuous degradation products

11. Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances

12. Substances and the form of a substance used in a chemical process should be chosen to minimize potential for chemical accidents, including releases, explosions and fires

Formation of Plastics:

– By either addition polymerisation or condensation polymerisation

Pros and Cons of Bioplastic

Pros:

  • reduces or eliminates Greenhouse Gases in production
  • requires less or no petrochemicals
  • biodegradable
  • can be utilized as fuel
  • slow release of Carbon Dioxide allows sufficient time for plants to absorb Carbon Dioxide

Cons:

  • cost
  • use of fertilizer and pesticides for crops
  • release ethane gas

Problems with Conventional Plastic

  • complex entanglements of polymer chains make it hard to decompose
  • rely heavily on petrochemicals
  • needs processing
  • recycling is energy-consuming and costly
  • releases toxic chemicals
  • non-biodegradable

Production of Bioplastic from Milk and Vinegar

Procedure:

  1. Mix 100 ml of milk and 20 ml of vinegar in a beaker
  2. Heat up the mixture until 50-60 degree Celsius   15067_732022160148045_2085284890_n
  3. Pour the milk through a filter funnel lined with filter paper 1231562_732022190148042_1082352354_n
  4. Residue on the filter paper can be molded into any shape and will harden when driedphoto (1)

Concept behind experiment:

Milk contains many molecules of a protein called casein. Casein is negatively charged so casein molecules repel each other and don’t stick together. When hot milk and vinegar are added together, the casein molecules unfold and reorganize into a long chain. Vinegar is an acid which means it contains many positively charged H+ ions which will neutralise the negative charges and lower the pH such that the casein molecules attract one another and become curdles. This allows the protein particles to come together and form a big sticky network. The casein in milk does not mix with the acid and so it forms the white precipitate (curds) seen in the residue. Each casein molecule is a monomer and the polymer made is made up of many of those casein monomers hooked together in a repeating pattern.

Sources:

http://www.sciencebob.com/experiments/plasticmilk.php

http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p101.shtml#background

Lesson 1: Sustainability and Making Bioplastics

Key Concept: Sustainability

What is sustainability?

– items that can be recycled/reused

– items that have minimal impact on the environment (i.e. compostable)

– at the same time can benefit as many people as possible

– seeks to reduce and prevent pollution at its source

– minimize use and generation of hazardous substances

eg. biofuels

Practical: Making Bioplastics from Cornstach

Materials:

– constarch/starch/potato starch

– ethanoic acid

– distilled water

– food colouring

– corn oil

– zip lock bag

– microwave oven

Procedure:

1. place the constarch in the plastic bag. Add corn oil and water

2. seal the bag, then mix the ingredients by rubbing outside the bag with fingers

3. Add food colouring

4. Open zip seal a bit and put place bag in a microwave oven

5. Microwave on high 25 seconds

Concept behind manufacturing of bioplastic:

Explanation 1: Heating up the cornstarch makes lactic acid. Lactic acid molecules the combine into long chains of polylactic acid, or PLA. Polymers, with their long interwoven chains, give all plastics, including PLA, their special properties.

Explanation 2: After starch is dried from an aqueous solution, it forms a film due to hydrogen bonding between the chains of polymers. Amylopectin inhibits the formation of film but the addition of strong acid breaks down amylopectin and allows the chains to be formed.

Advantages:

PLA is easier to compost. Under the right conditions it will break down into regular lactic acid in a matter of weeks. That could take pressure off the nation’s mounting landfills, since plastics already take up 25 percent of dumps by volume. Moreover, corn-based plastics are starting to be the cheaper alternative, seeing that oil prices are rising.

Disadvantages:

PLA has a melting point of 46 degrees Celsius, so it melts easily. It is also made from corn; a foodsource which can potentially feed many starving people.

Sources:

http://www.scienceoffcenter.org/science/310-corn-starch-plastic

http://www.smithsonianmag.com/science-nature/plastic.html

Image