Effectiveness and Efficiency of Fuels

In Lesson 6, we tested the effectiveness of fuels and measured the efficiency of fuels by combusting some fuels. The following chemicals and apparatus were used:

Methanol

Cyclohexane

Biodiesel made in the previous lesson

Cotton wool

Tweezers

Bunsen burner

Stopwatch

Metal Tongs

2 x Thermometers

2 x Evaporating dish

2 x Wire mesh

2 x 10ml measuring cylinder

1 x 100ml measuring cylinder

250ml beaker

Mass balance

Scientific Concepts/ Processes behind the efficiency of fuels

In this experiment, we aimed to test the efficiency of methanol, cyclohexane and various groups' homemade (or labmade) biodiesels. We ignited the flammable fuels and allowed it to heat up a fixed small volume of water (10ml) for a fixed amount of time (2 minutes). The initial and final temperature of the water was taken down in order to calculate the enthalpy change of the combustion reaction.

Fuel efficiency is using the least amount of fuel to travel the greatest distance. This is important as it reduces our dependency on oil/ fossil fuels. At the same time, a more efficient fuel translates to less combustion of fuels and hence less carbon dioxide released during the combustion reaction. It also saves money and increases energy sustainability, which is to use the fuel which can produce the most energy.

However, contrary to what we may think, our common fossil fuel engines are not very efficient! In fact, only 15% of energy from fuel moves the vehicles or runs accessories such as the radio in the car. The rest of the energy is lost to heat and exhaust. Hence, it is even more important that we aim to use the most efficient fuel such that precious energy is not wasted.

Results obtained and Calculations of Enthalpy Change

Type of fuel	Methanol	Cyclohexane	Biodiesel 1 (corn oil)	Biodiesel 2 (corn oil)	Biodiesel 3 (corn oil)	Biodiesel 4 (corn oil)	Biodiesel 5 (vegetable oil)
Initial temperature of water/oC	31.0	31.0	All the biodiesels made by us failed to combust as there was too much water content in the biodiesel – thus, we should have carried out more separation using the separation funnel to ensure the fuel is pure.
Final temperature of water/oC	100.0	75.0

In order to calculate enthalpy change, the following steps were necessary:

1. Calculate heat absorbed by the water using mcΔT (m= mass, c= specific heat capacity of water, ΔT= change in temperature).

2. Calculate the moles of the fuel burnt using mass/Mr.

3. Calculate enthalpy change using heat energy/moles.

Cyclohexane

Heat absorbed by water (Q) = (779 x 10 x 10^-6)(4.181)(75.0 – 31.0) = 1.4331 kJ (5sf)

Moles of cyclohexane burnt = 0.010 ÷ (12.0 x 6 + 1.0 x 12) = 0.00011905 mol (5sf)

Enthalpy change = 1.4331 ÷ 0.00011905 = 12000 kJ mol^-1 (3sf)

Methanol

Heat absorbed by water (Q) = (791.30 x 10 x 10^-6)(4.181)(100.0 – 31.0) = 2.2828 kJ (5sf)

Moles of methanol burnt = 0.010 ÷ (12.0 + 1.0 x 4 + 16.0) = 0.0003125 mol

Enthalpy change = 2.2828 ÷ 0.0003125 = 7300 kJ mol^-1 (3sf)

From the above, we can conclude that cyclohexane is the more efficient fuel as it produced the most amount of energy for every mole of the fuel. Hence, it would be better for us to use cyclohexane in order to reduce our carbon footprint as well as save money! :D

However, there were some limitations to this experiment. It was hard to control the ignited flame from the fuel. Hence, in order to minimize error, we made sure that the tip of the flame touched the beaker of water for every ignited fuel. There is also heat loss to the surroundings (thermometer, air etc) during the heating of the beaker of water, so we are unable to account for this loss of heat energy.

Pictures!

The failed ignition of the biodiesel we made :(

Lighting the cyclohexane fuel!

Lighting the methanol fuel!

Extracting Limonene from Orange Peel

In Lesson 4, we extracted Limonene from Orange Peels using the following ingredients:

Distillation apparatus
Blender
Separating funnel
Stirring rod
3 x 100ml beaker
1 x 100ml conical flask
Hot plate

Scientific Concepts/ Processes behind the extraction of D-Limonene
As background knowledge, limonene is an essential oil with anti-carcinogenic properties and is used in numerous cleansing products. Limonene has a boiling point of 176 degree celsius, and appears as a colourless liquid at room temperature. In this experiment, we extract D-Limonene, which is an isomer of Limonene that smells like citrus. 

Steam distillation is used to extract the d-limonene as it does not denature the structure of the essential oil molecules. The hot steam opens the pockets in which the oils are kept and releases the aromatic molecules from the orange peel. These essential oil molecules, which are volatile, then escape from the orange peel and vapourise before condensing and being collected.

This is something we should note: both the fruit flesh and fruit peel can be used as sources of fuel (limonene as biodiesel), however extracting limonene from the fruit peel would mean a higher yield of limonene. To further increase the yield of limonene, the orange peel's cellulose should be broken down into glucose to ferment and produce more limonene.

Why Limonene?
Limonene is a useful product which is extracted from fruit peels which would otherwise be discarded. Limonene is also combustible and hence can be used as a fuel. It can also be used in medicine and to promote weight loss, prevent cancer, treat cancer and treat bronchitis. In foods, beverages and chewing gum, it is also used as a flavouring. In pharmaceuticals, limonene is added to help medicinal ointments and creams penetrate the skin. In manufacturing, limonene is used as a fragrance, cleaner (solvent), and as an ingredient in water-free hand cleansers.

A more specific example to D-Limonene would be that of cancer treatment. D-Limonene seems to build up in cancer tumors, when it is taken by mouth in 21-day cycles. The high levels of limonene in the tumors may slow down the progress of the cancer, however, its effect on the person's survival is still uncertain.

Limonene is also safe in food amounts, and appears to be safe for most people in medicinal amounts when taken by mouth for up to one year.

As can be seen above, limonene is a very useful product in our lives.

Amount of Limonene extracted in our lab experiment
In our lab experiment, the results turned out quite positive:

Amount of orange peels used/g	Amount of D-limonene extracted/g	Percentage yield
54.06g	0.44g	0.814%

When we researched online, we found out that the expected percentage yield was about 1%. However, we suspect that due to that fact that not all of the blended orange peel could be added to the conical flask, there was a loss of mass even before steam distillation began. Hence, the size of the conical flask was a limitation for this experiment since we could not add more blended orange peel to the conical flask.

Pictures of Process and Final Product

Cutting the orange flesh off as we only need the orange peel! (product will be of higher yield)

Tada! We have finished cutting the orange flesh off the orange peel!

Weighing the orange peels for 
calculations of percentage yield later on!

Putting all the orange peel into the blender!

Blending the orange peel (some water was added)!

Blending is finally done!

Adding the blended orange peel to the conical flask to prepare for steam distillation!

Steam distillation set-up (hot plate used, so
heating was too slow!)

So we improvised and changed to a bunsen burner! :D

Monitoring the temperature rise........

YAY the droplets of limonene are cominggg!

FINAL PRODUCT - D-LIMONENE

 Video of the D-Limonene being collected!!

Resources
http://www.webmd.com/vitamins-supplements/ingredientmono-1105-LIMONENE.aspx?activeIngredientId=1105&activeIngredientName=LIMONENE

Bioplastics

In Lesson 2, we made bioplastic in class that required the following ingredients:

Corn starch/ Potato starch/ Milk
Ethanoic Acid
Distilled water
Food colouring
Corn oil
Ziplock bag
Microwave oven

Scientific Concepts/ Processes behind the making of bioplastic from starch
As background knowledge, there are two general types of starch that exist: amylose and amylopectin. They both differ in structure and functional properties, where amylose is linear, with 200-2000 polymer units and forms a firm gel formation, whereas amylopectin is branched, with up to 2 million polymer units and forms a non-gelling to soft gel formation.

In this experiment, corn starch and potato starch are mostly made of amylopectin (about 80%, if not completely).

Bioplastics are made by converting sugar present in plants (starch) into plastic. There are two types of bioplastic - polyactide acid (PLA) and polyhydroxyal-kanoate (PHA). In this experiment, PLA is made.

Starch is dried from an aqueous solution (after adding corn oil and water) to form a film due to hydrogen bonding between the chains of polymers. However, amylopectin inhibits the formation of film. Thus, a strong acid is needed to break down amylopectin for the film formation.

Starch undergoes hydrolysis to form glucose, which then undergoes fermentation to form lactic acid. However, lactic acid cannot be polymerized directly to form PLA as the formation of water molecules in the process will prevent the growing chain of lactic acid molecules from staying together. Hence, lactic acid first undergoes dehydration to remove water molecules and from polyactic acid oligomers, then thermal cracking to form lactide. Lactide can then be polymerized to form a chain of lactic acid molecules also known as PLA.

Why bioplastics?
Many people around the world have created bioplastic in order to tackle the disadvantages and problems with our conventional plastic, namely:

1. The complex entanglements of polymer chains make it hard to decompose and hence non-biodegradable.
2. It relies heavily on petrochemicals (which are obtained from fossil fuels - nonrenewable resource!)
3. The recycling process is energy-consuming and costly.
4. The production of conventional plastic releases toxic chemicals.

Hence, using one of the 12 principles of Green Chemistry to use renewable feedstocks, a raw material/ feedstock should be renewable rather than depleting whenever technically and economically practicable. The materials used in this experiment, namely corn starch/potato starch and corn oil, are renewable since they can be obtained from plants.

Another one of the 12 principles of Green Chemistry used here is to have less hazardous chemical syntheses. Whenever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment. This making of bioplastic reduces or eliminates Greenhouse Gases during the production, requires less/ no petrochemicals and with the slow release of carbon dioxide gas, it allows sufficient time for plants to absorb this carbon dioxide gas production.

The last principle of Green Chemistry involved is that of design for degradation. Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment. As compared to the non-biodegradable conventional plastic, bioplastic is biodegradable and hence reduces the amount of waste on earth that persist in the environment.

Pictures of final product

Green Bioplastic (colour from food colouring)

Yellow Bioplastic (colour from food colouring)

Resources
http://www.beyondbenign.org/greenchemistry/12principles.html