Biofuels

Part 1: Synthesizing Biofuel

In this practical, we attempted to synthesize biofuel using corn oil. Corn oil is a triglyceride, made of glycerol molecules joined to three fatty acid chains by ester linkages.




Molecular structure of corn oil

The process of creating a biofuel is from corn oil is known as transesterification - transforming corn oil (an ester) into biofuel (another ester).

Method
> Add 100 m1 of corn oil into a 500 ml beaker
> In a separate beaker add 55.0 ml of methanol and 22.5 ml of 0.1 M NaOH solution.
> Place the beaker of corn oil on a hot plate, heat until 60 degrees Celsius
> Add the mixture from step 2 in eight phases, leaving 5 min between each phase. The temperature of the reaction mixture should be kept between 60 and 70 degrees Celsius to prevent it from spurting
> Let the mixture cool and separate over a week
> Place in a separating funnel and discard the lower layer (glycerol)
> Add 10 ml of 0.1 M acetic acid and invert the separating funnel gently 5 times
> Discard the lower layer
> Repeat the extraction step using 10 ml of distilled water
> Pour the the washed biofuel into a 100 ml beaker. Heat at 70-80 degrees Celsius for 10-15 min to evaporate the residual water.

Calculations for percentage yield
% yield = mass of dry biofuel/mass of corn oil x 100
= 69.84/89.26 x 100
= 78.2% (3sf)

NB: the final mass of the dry biofuel is lower than the actual value as spillage occurred during experimentation

Part 2: Determining the efficiency of fuels

In this demonstration, our teacher showed us how the efficiency of fuels can be determined by enthalpy changes.

Method
> Place 2 pieces of cotton wool at into a crucible
> Measure 10 ml of chosen fuel and pour into the crucible
> Measure 10 ml of distilled water into a clean 50 ml beaker
> Fix the beaker above the crucible using a retort stand
> Measure the initial temperature of the distilled water
> Ignite the fuel with a lighted splint and start the stopwatch
> Adjust the height of the beaker such that it is above the tip of the flame
> After 2 minutes, record the temperature of the water
> Extinguish the flame by covering it with a wire gauze with ceramic center

Results

Fuel	Initial temperature/˚C	Final temperature/˚C	Temperature change/˚C
Cyclohexane	31.0	75.0	+44.0
Methanol	31.0	100.0	+69.0

NB: Water reached boiling point in < 2 min when methanol was used as a fuel

Calculations for enthalpy change
We need to find the enthalpy (heat) change of water caused by one mole of fuel to determine its efficiency.

Enthalpy change of water = mass of water (kg) x specific heat capacity of water (kJ/ kg K) x change in temperature (˚C or K)
OR
q = mc∆T

NB: ˚C and K have same unit intervals and are interchangeable with reference to change in temperature
NB: specific heat capacity of water = 4.181 kJ/ kg K

Fuel	q (= mc∆T)
Cyclohexane	0.01 x 4.181 x 44 =1.83964 kJ
Methanol	0.01 x 4.181 x 69 =2.88489 kJ

Since we want to calculate the enthalpy change of water caused per mole of fuel, we need to calculate the amounts of fuel in moles.

Density of cyclohexane = 779.00 kg/m3

Mass of 10 ml of cyclohexane = 779 x 10/1003 x 1000 = 7.79 g
No. of moles of cyclohexane (C₆H₁₂) = 7.79/ (6 x 12.0 + 12 x 1.0) = 0.092738 mol

Density of methanol = 791.30 kg/m3

Mass of 10 ml of methanol = 791.3 x 10/1003 x 1000 = 7.931 g
No. of moles of methanol (CH₃OH) = 7.931/ (12.0 + 4 x 1.0 + 16.0) = 0.24728 mol

Fuel	Enthalpy change per mol (kJ/mol) (3sf)
Cyclohexane	1.83964 ÷ 0.092378 = 19.9
Methanol	2.88489 ÷ 0.24728 = 11.7

Conclusion: Cyclohexane is the more efficient fuel

Sources of error

- Boiling point of water cannot exceed 100˚C and would affect the accuracy of measurement for methanol.

- Heat lost to surroundings

- Incomplete combustion of fuel due to insufficient oxygen

- Flame was extinguished after 2 min, hence not all the fuel was combusted

References
Image of triglyceride. Retrived from http://www.proteinpower.com/drmike/wp-content/uploads/2008/02/triglyceride.jpg
Image of corn oil molecule. Retrieved from https://sci9bestq3bm.wikispaces.com/Corn+Oil-Ensure

Extraction of D-Limonene from orange peel

In this practical, we extracted D-Limonene, an essential oil from orange peel using steam distillation. D-Limonene not only smells great, it can be used as a fuel (it is combustible) and is green because it comes from a waste material, orange peel.

Properties of D-Limonene
- Density: 0.84 g/cm3
- Boiling point: 176 degrees Celsius
- Unsaturated hydrocarbon with chemical formula C₁₀H₁₆

D-Limonene

Method
> Scrape the white pith from the skins of 4 medium oranges
> Blend with distilled water until a fine puree is formed
> Transfer to 250 ml round-bottomed flask
> Attach flask to distillation apparatus. Turn on hotplate to highest setting
> When the thermometer shows 100 degrees Celsius, turn on the tap to run water through the condenser
> The distillate contains D-Limonene and water. D-Limonene should form a layer on top of the water and can be removed using a dropper
> If there is no distinct separation extract using NaCl and dichloromethane
> Confirm presence of D-Limonene by adding extract to aqueous bromine. Bromine should decolourise.

Distillation apparatus

D-Limonene forms a layer above water

Calculating yield

Mass of orange peel/g	50.50
Mass of d-limonene/g	1.20

% yield = mass of limonene/mass of orange peel x 100 

= 1.20/50.50 x 100 = 2.4%

D-Limonene yield is considerably higher than yield lavender essential oil, which is about 0.3% mass-for-mass.

Science behind
An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. The essential oil of orange is made of more than 90% D-Limonene. D-Limonene is secreted from little pockets on the surface of orange peel and gives orange its distinctive smell.

SEM image of citrus peel

When the water and peel puree is heated, water and volatile compounds (including D-Limonene) vapourise and enter the condensor. They are then condensed to form the hydrosol, a mixture of water and orange essence. The D-Limonene, being hydrophobic and less dense than water, forms a layer on top of the water.

D-Limonene is used in perfumes and household cleaners for its fragrance. It is also a safe, effective and environmentally-friendly solvent used in adhesive and stain removers, cleaners and paint strippers.

Orange essential oil is a byproduct of orange juice manufacturing that can be obtained by centrifugation. D-Limonene can then be extracted from the orange oil by steam distillation. Because orange oil, unlike other essential oils, is a byproduct, it is one of the cheapest, making D-Limonene cost-effective.

References

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

http://en.wikipedia.org/wiki/Essential_oil#Distillation

http://www.psmicrographs.co.uk/orange-peel-zest-cells/science-image/p00449a

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

http://www.growing-lavender.com/Lavender%20Oil.htm

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

Paper Recycling

In this lesson, we made recycled paper.

Method
> Fill a fishtank with tap water
> Shred used paper into small pieces
> Blend with tap water until it forms a pulp mixture
> Pour the pulp into the fish tank filled with water
> Repeat until there is enough pulp in the fish tank to form a thin layer of paper pulp when passed through the screen
> Using the paper mould, remove some pulp from the fish tank, letting the water drain
> Place on a towel and let dry overnight
> Remove from the mould. This is recycled paper!

Paper is made of fibers (usually cellulose fibers derived from wood) pressed together.

Scanning electron microscope image of cross section of filter paper

When blended with water, the cellulose fibers are broken apart as water molecules disrupt the hydrogen bonds between them and they are re-suspended. Passing the pulp through the paper screen forms a thin layer of fibers on the screen. When dried, these fibers form hydrogen bonds to form a sheet of paper.

Industrial practice
Paper is mixed with water and chemicals to break it down, then heated and chopped to yield strands of cellulose. The resulting mixture is called a pulp or slurry. It is passed through screens which removes plastic or glue contaminants. The mixture is then cleaned, de-inked, bleached and mixed with water. It can then be made into new paper. The same fibers can be recycled about seven times, but the cellulose fibers get shorter each time, reducing the quality of the paper.

Benefits
Paper production accounts for about 35% of felled trees. Recycling paper saves trees. Recycling 1 ton of copier paper saves approximately 2 tons of wood. Recycling paper also uses less energy than making new paper.

We can also help by reducing our use of paper and re-using paper which reduces the need for recycling and paper manufacturing in the first place :)

References
http://en.wikipedia.org/wiki/Paper_recycling
http://en.wikipedia.org/wiki/Paper
http://www.sciencephoto.com/image/215422/350wm/H1000661-Filter_paper,_SEM-SPL.jpg

Synthesizing Bioplastic Part 2

In this practical, we synthesized a protein-based bioplastic using milk and ethanoic acid (vinegar). The protein extracted is a common milk protein called casein.

>Add 100 ml of milk and an equal amount of vinegar to a beaker
>Heat to 60 degrees Celsius. The milk should be coagulated. If not, continue heating until clumps are visible.
>Cool and filter
>The residue is the casein plastic. It can be moulded.

 The product synthesized was very soft and would disintegrate when water is added. Usually, plasticisers such as glycerine are also added to the protein to make the plastic harder and more durable.

This is also the method to make homemade cheese! See the recipe here.

Acid makes milk curdle - separate into curds (containing milk solids, fats and proteins) and whey (contains mostly water). To understand why this happens, we need to know about the structure of milk.

Milk is an emulsion of fat, water, lactose (sugar) and a mixture of proteins. Fat globules are surrounded by phospholipids and proteins that keep them apart and suspended in the mixture. If we beat milk, the fat globules clump together and separate from the liquid. This is how butter is made!

The water contains soluble proteins that are hydrophobic on one end and hydrophillic on the other. Because of this, they organise themselves into globes called micelles. These proteins are called caseins. There are 4 different types of caseins and they make up 80% of the weight of proteins in milk.

Casein micelle. The submicelle contains a hydrophobic core and is oriented towards the center.

The outer surface of a casein micelle is made of up of a layer of negatively-charged kappa-casein. Since like charges repel, casein micelles repel one another and are kept in solution.

Acids release H+ ions in solution. When acid is added to milk, H+ ions bind to kappa-casein molecules, causing them to lose their negative charge. Therefore, the casein micelles with bind together and become visible as clumps in the milk.

Heat weakens the interaction forces between casein components within the micelles, causing them to dissociate more readily.

If the milk is heated to 85 degrees Celsius before adding the acid, kappa-casein reacts with a whey protein (protein that is dissolved in the water) called b-lactoglobulin to form a complex that makes the casein micelle surface much coarser. So when acid is added, the casein molecules clump into an open spongy gel that soaks up the water. This produces yogurt!

In commercial cheese making, lactic acid bacteria and rennet are added instead of ethanoic acid. Lactic acid bacteria digest the lactose sugar in milk to form lactic acid needed to discharge kappa-casein. This process is called lactic acid fermentation. Rennet contains an enzyme called rennin that facilitates casein micelle dissociation (curdling) by acting on the casein micelles.

The flavours of cheese are affected by many factors - the type of milk (goat or cow for instance), the type of bacteria used to innoculate it, and the conditions in which the cheese is aged. Ageing allows the cheese to develop complex flavours as the microbes act on it.

Swiss cheese. The holes are formed by bubbles of carbon dioxide gas, produced when propionibacteria consume the lactic acid excreted by other bacteria.

Back to the topic of bioplastics. Protein-based plastic is advantageous over petroleum-based plastic because it is biodegradable. Protein is synthesied naturally, making it a renewable resource unlike petroleum which is a finite resource.

The principle of synthesizing bioplastic from proteins is similar to the principle of synthesizing bioplastic from starch. Like starch, protein is a natural polymer. It is made of many amino acids, forming an amino acid chain known as a polypeptide. A polypeptide folds into complex structures due to its make-up.

Polypeptide folding showing primary, secondary, tertiary and quarternary structures.

This is not good for synthesizing bioplastic, as a linearised form of the amino acid is needed to make a strong homogenous structure. Many steps are taken to denature proteins into a linear form. Watch this video for a more detailed explanation.

http://www.youtube.com/watch?v=N3a9gr6SpZU

Proteins' complex structure makes it challenging for viable protein-based bioplastics to be synthesized. Currently, many researchers are working on this issue, waiting for a breakthrough.

Sources

http://wiki.answers.com/Q/Why_does_milk_curdle_when_acid_is_added

http://science.howstuffworks.com/innovation/edible-innovations/food-preservation7.htm

http://www.sciencedirect.com/science/article/pii/S0022030296764901

http://voices.yahoo.com/why-there-so-many-different-cheeses-if-they-are-8229631.html?cat=22

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

Synthesizing Bioplastic

Bioplastics are plastics that are derived from renewable biomass, such as corn. This contrasts with conventional plastics, which are made with petroleum, a non-renewable resource.

Bioplastics are more sustainable because they come from renewable sources. However, using food crops such as corn to produce bioplastics poses a problem - crops require large amounts of water, land, fertiliser and other materials to grow. The production of bioplastics is also energy-intensive. Some bioplastics also produce methane gas when they decompose. Methane gas is a greenhouse gas many times more potent than carbon dioxide.

However, unlike petroleum-based plastics, bioplastics are biodegradable. Although bioplastics may require as much energy to produce as petroleum-based plastics, they will not clog landfills and are more environmentally-friendly in this aspect.

Want to know more about different types of plastics and their pros and cons? Visit the website at this link: http://www.explainthatstuff.com/bioplastics.html


Unlike bioplastics, conventional petroleum-based plastics are non-biodegradable

During this practical, we synthesized bioplastic using corn starch, potato starch and synthesized starch as the biomass material.

Method
> Add one spoon of starch into a ziplock bag. Add corn oil and mix by rubbing the bag. There should be just enough oil to make the flour clump together.
> Add a little water and a few drops of food colouring to colour the plastic. Mix well.
> Microwave the open ziplock bag on high for 25 seconds.
> Remove from microwave and mould with wooden block while still hot.

Before microwaving

After microwaving

The plastic that we synthesized (which was made using potato starch) is soft, bouncy and easily broken apart, very unlike plastic we are used to. The plastic we synthesized also disintegrates when wet, due to its slightly polar nature. Therefore, other additives are needed to give starch-based plastics the desirable properties of plastic. Often, flexibilisers and plasticisers such as sorbitol and glycerine are added. Starch-based plastics are already in the market and are called thermoplastic starch (TPS).

Starch is made of amylose (linear glucose polymer) and amylopectin (highly branched glucose ploymer). The amylose/amylopectin ratio is different for starch from different plant sources.




When heated with water, starch is gelatinised or destructurised: hydrogen bonding sites such as hydroxyl groups bind more water, irreversibly dissolving the starch. Penetration of water increases the randomness of the general starch granule structure and decreases the number and size of crystalline regions. When heated, crystalline regions become diffuse so that the chains begin to separate into an amphorous form.


Crystalline regions are ordered and have characteristic geometry but amorphous regions do not.

During the gelatinisation of starch, 3 main things happen to the starch granule: 1. granule swelling 2. crystal or double helical melting 3. amylose leaching.

Water is first absorbed in the amorphous space of starch, which leads to a swelling phenomenon during heating and then transmitted through connecting molecules to crystalline regions.^[3] Water enters tightly bound amorphous regions of double helical structures to swell amylopectin, thus causing crystalline structures to melt and break free.^[4] Stress caused by this swelling phenomenon eventually interrupts structure organization and allows for leaching of amylose molecules to surrounding water.

The result is a colloidal solution - polymers dispersed in a medium of water - that gels when cooled. This is due to to a process called retrogradation. When cooled, cooked starch molecules will rearrange to form a more ordered crystalline structure and inter-molecular bonding occurs between chains of amylose and amylopectin, with water embedded within the molecule.

Due to strong associations of hydrogen bonding, longer amylose molecules will form a stiff gel.^[6] Amylopectin molecules with longer branched structure, increases the tendency to form strong gels. High amylopectin starches will have a stable gel, but will be softer than high amylose gels.

Molecules that are capable of hydrogen bonding with hydroxyl groups such as water, sorbitol and glycerine act as plasticisers and change the properties of the gel formed.

The corn oil in our practical probably acted similarly to glycerin, making the plastic more pliable by acting as a lubricant at a molecular level. I am not sure about this, because corn oil and glycerin are quite different. But there must be a reason why the plastic was 'bendy'. Classmates that added less oil got a less flexible plastic.

More can be deduced by changing the proportion of reactants and observing the properties of the plastic.

This year, one of the prize-winning projects are the Google Science Fair was about synthesizing bioplastic from banana peels. Check it out here!

Sources:
http://www.sciencehq.com/chemistry/crystalline-and-amorphous-solids.html
http://en.wikipedia.org/wiki/Starch_gelatinization
http://polymerinnovationblog.com/thermoplastic-starch-a-renewable-biodegradable-bioplastic/
http://green-plastics.net/videos/35-howto/52-video-brandon121233

Green Chemistry and Sustainability

Green Chemistry is a philosophy that promotes sustainability. Sustainability is about modifying practices so that they can be maintained long-term. This includes considering impacts on

> the economy: projects should be financially sustainable
> social equity: people involved in production should be treated fairly
> the environment: minimising production of pollutants, increasing yield through optimisation

How does Green Chemistry promote sustainability? By definition,
Green Chemistry encourages the design of products and processes that minimise the use and generation of hazardous substances.

In other words, Green Chemistry encourages us to optimise processes so they generate less waste (including waste harmful to the environment) and more yield.

Companies can use the 12 principles of Green Chemistry as a guide to work towards becoming more sustainable.

Sustainable Companies
Sustainable companies take measures to minimise the impact of their businesses on the environment. One example of a sustainable company is Justin's, a company that sells nut butter.



Justin's modified the design of their jars to use 47% less plastic. This is beneficial to the environment because plastic is non-biodegradable (cannot be broken down by microbes) and comes from petroleum, which is a finite resource.

In addition, Justin's sources their raw materials (like nuts) from as nearby as possible. This saves transport costs and fuel, which reduces carbon emissions. Click on this link to find out more about the nut's journey from soil to jar :)

http://www.justins.com/theDirtOnNuts_CHB.php

Justin's is also working towards a 100% renewable squeeze-pack packaging that can be composted in people's homes. Compostable materials are better than plastic because they can biodegrade.

Justin's sustainable philosophy is inspiring. Do find out more about such companies, and support their sustainable practices! :)