FE6 VCE Unit 3 Comparing biodiesel and petrodiesel

Summary

This video compares petrodiesel and biodiesel, focusing on their chemical reactivity, physical properties, and environmental impacts. Petrodiesel is derived from crude oil through fractional distillation, containing various compounds including aromatic rings. Biodiesel, on the other hand, is a fatty acid ester formed from fats and oils, involving a base-catalyzed reaction. The video highlights differences in polarity, viscosity, and cloud points, as well as their respective environmental impacts, emphasizing biodiesel's theoretical carbon neutrality despite additional CO2 emissions from refining and transport.

Takeaways

• 🔍 Petrodiesel is derived from crude oil through fractional distillation, containing multiple compounds, mainly C10 to C15 hydrocarbons and aromatic compounds.
• 🌿 Biodiesel is a fatty acid ester obtained from fats and oils, usually a methyl or ethyl ester, created by combining a small alcohol with a large fatty acid.
• ⚛️ Biodiesel formation involves the base-catalyzed hydrolysis of triglycerides, producing three biodiesel molecules and one glycerol molecule.
• 🧲 Petrodiesel is non-polar and relies solely on dispersion forces for molecular interactions, while biodiesel has a polar ester functional group enabling dipole-dipole interactions.
• 💧 Biodiesel is hygroscopic, meaning it can absorb moisture from the environment due to its polar ester group, potentially reducing its energy density.
• 💧 Biodiesel has a higher viscosity than petrodiesel due to stronger intermolecular forces, which affects its flow properties, particularly in colder temperatures.
• ❄️ Biodiesel has a higher cloud point compared to petrodiesel, which affects its usability in colder climates as it starts to solidify at higher temperatures.
• 🔋 Biodiesel has slightly lower energy content and energy density than petrodiesel, providing less energy per liter or per kilogram of fuel.
• 🌍 While the CO2 emissions from burning biodiesel and petrodiesel are similar, biodiesel is considered more environmentally friendly due to the potential reabsorption of CO2 by plants during its production.
• 🌱 Biodiesel is not entirely carbon neutral due to the energy used in refining and transport, but it is still a more sustainable alternative compared to fossil fuels.

Q & A

What is the primary difference between petrodiesel and biodiesel in terms of their origin?

Petrodiesel originates from crude oil and is separated through fractional distillation, while biodiesel is a fatty acid ester derived from fats and oils, typically produced through a transesterification process involving methanol.

Why are aromatic compounds in petrodiesel important to understand?

Aromatic compounds in petrodiesel, which contain benzene rings, are important because they contribute to the chemical composition and properties of the fuel, even though they do not necessarily have a strong aroma.

What is the typical carbon chain length found in the fraction used to obtain petrodiesel?

The typical carbon chain length in the fraction used for petrodiesel is around 75 percent C10 to C15.

How is biodiesel produced from fats and oils?

Biodiesel is produced from fats and oils through a reaction involving a triglyceride (glycerol backbone with hydrophobic tails) and methanol, in the presence of a strong base, to form methyl esters and glycerol.

What is the significance of the ester group in biodiesel molecules?

The ester group in biodiesel molecules is significant because it introduces polarity to the molecule, allowing for dipole-dipole interactions and hydrogen bonding with water, which affects properties such as hydroscopicity and viscosity.

Why is the hydroscopic nature of biodiesel a concern?

The hydroscopic nature of biodiesel is a concern because it can absorb moisture from the environment, which can lead to reduced energy density and potential issues in cold weather operation due to the presence of water in the fuel.

How does the viscosity of biodiesel compare to that of petrodiesel?

The viscosity of biodiesel is almost twice that of petrodiesel, which is due to stronger intermolecular forces, including dipole-dipole interactions and dispersion forces.

What is the cloud point of biodiesel, and how does it affect its usability?

The cloud point of biodiesel ranges from -3 to 12 degrees Celsius, which is higher than that of petrodiesel. This can affect its usability in cold climates or temperatures below zero, as it may start to solidify and lose its ability to flow.

How does the energy content and energy density of biodiesel compare to petrodiesel?

The energy content and energy density of biodiesel are slightly lower than those of petrodiesel, meaning that less energy is obtained per liter or gram of fuel.

What is the environmental impact of carbon dioxide emissions from both petrodiesel and biodiesel?

The carbon dioxide emissions from both petrodiesel and biodiesel combustion are about the same, but the advantage of biodiesel is that the CO2 released is theoretically reabsorbed by plants during photosynthesis, contributing to a more sustainable cycle, despite not being entirely carbon neutral due to energy expended in refining and transport.

Outlines

00:00

🔬 Introduction to Petrodiesel vs. Biodiesel

This section introduces the topic of comparing petrodiesel and biodiesel. It covers the chemical reactivity, physical properties, sourcing, and environmental impacts of both fuels. Petrodiesel, a product of crude oil separated through fractional distillation, contains various compounds, including aromatic compounds like benzene. Biodiesel, in contrast, is a fatty acid ester created by reacting fats or oils with alcohol, typically forming methyl or ethyl esters. Key differences between saturated and unsaturated carbon bonds in biodiesel are highlighted.

05:01

🧪 The Chemistry Behind Biodiesel Production

This paragraph delves into the chemical process of producing biodiesel, emphasizing the breakdown of triglycerides using a base catalyst and methanol. The reaction produces three biodiesel molecules and one glycerol molecule. The biodiesel has a polar ester group that creates dipole-dipole interactions and can form hydrogen bonds with water. This polar group makes biodiesel hydroscopic, allowing it to absorb water from the environment, which can reduce its energy density. The section also discusses the higher viscosity and cloud point of biodiesel compared to petrodiesel, affecting its performance in colder temperatures.

10:02

🌍 Environmental Impact and Final Comparisons

This section focuses on the physical properties, energy content, and environmental impact of petrodiesel and biodiesel. Biodiesel is denser and more viscous than petrodiesel, with a higher cloud point, which limits its usability in colder climates. Biodiesel's energy content and energy density are slightly lower than petrodiesel's. Despite biodiesel's similar CO2 emissions to petrodiesel, it offers an environmental advantage because the CO2 released during combustion is theoretically reabsorbed by plants used in biodiesel production, although transport and refining negate full carbon neutrality.

Keywords

💡Petrodiesel

Petrodiesel, also known as petroleum gas, is a part of crude oil that is separated through fractional distillation. It is not a pure substance but a mixture of compounds, typically around 75 percent C10 to C15, and includes aromatic compounds. In the context of the video, petrodiesel represents a fossil fuel and is compared with biodiesel in terms of chemical reactivity, physical properties, sourcing, and environmental impact. The script explains that petrodiesel contains multiple compounds and is non-polar, which affects its properties such as viscosity and energy density.

💡Biodiesel

Biodiesel is a fatty acid ester derived from fats or oils, typically turned into a methyl or ethyl ester. It is distinct from petrodiesel as it is not obtained from crude oil. The script describes biodiesel as having a polar functional group due to the ester, which gives it different properties such as higher viscosity and hydroscopicity compared to petrodiesel. The production of biodiesel involves the reaction of triglycerides with methanol in the presence of a base catalyst, resulting in biodiesel and glycerol.

💡Fractional Distillation

Fractional distillation is a process mentioned in the script that separates the components of crude oil based on their boiling points. The petrodiesel fraction, which is the focus of the script, comes off the column at a certain temperature range and contains multiple compounds. This process is crucial for obtaining petrodiesel from crude oil and is fundamental to understanding the sourcing of fossil fuels.

💡Aromatic Compounds

Aromatic compounds, as discussed in the script, are organic compounds that contain benzene rings. These are not related to aroma but to their chemical structure. Examples given in the script include benzene, toluene, xylenes, and naphthalene. Aromatic compounds are part of the fraction from which petrodiesel is obtained, contributing to its chemical composition.

💡Triglyceride

A triglyceride is a type of lipid with a glycerol backbone and three fatty acid chains attached. In the script, triglycerides are the starting materials for biodiesel production. They are found in fats and oils and are broken down in a reaction vessel with methanol to produce biodiesel and glycerol, illustrating the transformation from a natural fat source to a fuel.

💡Polarity

Polarity in the script refers to the property of molecules that have an uneven distribution of electron density, leading to regions of positive and negative charge. Biodiesel has a polar functional group due to the ester, which allows it to form dipole-dipole interactions and hydrogen bonds with water, making it hydroscopic. This is in contrast to petrodiesel, which is non-polar and only has dispersion forces between its molecules.

💡Hydroscopy

Hydroscopy, as mentioned in the script, is the ability of a substance to absorb moisture from the environment. Biodiesel exhibits hydroscopy due to the polar nature of its ester group, which can attract and form hydrogen bonds with water molecules. This property can lead to water being trapped in the fuel, potentially reducing its energy density and posing challenges in cold temperatures.

💡Viscosity

Viscosity is the measure of a fluid's resistance to flow, and in the script, it is used to compare the flow properties of petrodiesel and biodiesel. Biodiesel has a higher viscosity than petrodiesel, which is attributed to its stronger intermolecular forces, including dipole-dipole interactions, and the larger size of some biodiesel molecules. This higher viscosity affects the fuel's performance and handling.

💡Cloud Point

The cloud point is the temperature at which solid crystals start to form in a substance as it cools down. In the script, it is mentioned that biodiesel has a higher cloud point than petrodiesel, ranging from negative 3 to 12 degrees Celsius. This means that biodiesel can start to solidify at higher temperatures, which is a consideration for its use in cold climates.

💡Environmental Impact

The environmental impact discussed in the script includes the comparison of carbon dioxide emissions between petrodiesel and biodiesel. While both release similar amounts of CO2 upon combustion, biodiesel is considered more environmentally friendly because the CO2 released is theoretically reabsorbed by plants during photosynthesis. However, the script also notes that the actual carbon neutrality is affected by energy used in refining and transporting biodiesel.

Highlights

Introduction to comparing petrodiesel and biodiesel, focusing on chemical reactivity, physical properties, sourcing, and environmental impact.

Petrodiesel is derived from crude oil through fractional distillation and contains a mix of compounds, including 75% C10 to C15 hydrocarbons and aromatic compounds.

Aromatic compounds in petrodiesel contain benzene rings, which can include substances like toluene and naphthalene.

Biodiesel is a fatty acid ester made from fats and oils, typically using methanol to create methyl esters.

Saturated and unsaturated bonds in biodiesel refer specifically to carbon-carbon bonds within the fatty acid chains.

Biodiesel is produced by reacting a triglyceride (fats/oils) with methanol in the presence of a strong base, resulting in biodiesel and glycerol.

Petrodiesel is non-polar with only dispersion forces acting between molecules, while biodiesel has a polar ester group allowing dipole-dipole interactions.

Biodiesel is hygroscopic, meaning it can absorb moisture from the environment due to its polar ester group.

Higher viscosity of biodiesel compared to petrodiesel is due to stronger intermolecular forces, including dipole-dipole interactions.

Biodiesel has a higher cloud point, meaning it begins to form solid crystals at higher temperatures than petrodiesel.

Comparison of physical properties: biodiesel is denser, more viscous, and has a higher cloud point than petrodiesel.

Both petrodiesel and biodiesel have similar carbon dioxide emissions during combustion, though biodiesel is closer to carbon neutrality due to plant absorption during production.

Diesel engines produce 10-20% less CO2 than petrol engines, but biodiesel's CO2 emissions are comparable to petrodiesel.

Biodiesel is not entirely carbon neutral due to the CO2 emissions from refining and transport processes.

The discussion concluded with an emphasis on understanding bonding in fuels and the upcoming topic of combustion and thermochemical equations.

Transcripts

so hi and welcome back today we're going

to

start moving away from the sources and

things like that and get into

the details of comparing petrodiesel

versus biodiesel

okay so this is one of our fossil fuel

biofuel comparisons that we need to know

in detail um in regards to their

chemical reactivity

their physical properties sourcing and

environmental impact so let's get

started

so petrodiesel as we mentioned sometimes

referred to as petroleum gas

those kinds of things petrodiesel

specifically

is part of crude oil that can be

separated from

fractional distillation okay it is not

however a pure substance the fraction

that comes off

in the column remember with fractional

distillation

we're talking about heating the column

and the fractions

being different sizes as they come up

the fraction that comes off

contains multiple compounds okay

usually it's around 75 percent c10 to

c15

and it contains some aromatic compounds

when we talk about

aromatic compounds we're not talking

about them having a strong aroma or

being

smelly they are containing

benzene rings okay they contain an

aromatic ring

so something like benzene which this one

is here

so um when we see this in another group

we refer to this as a phenyl group

and we can see here benzene substituted

benzene with a ch3 which is toluene

xylenes naphthalene and these kinds of

things you do not need to be able to

name

these but you do need to know that there

are other aromatic compounds

within the fraction from which we obtain

petrodiesel

biodiesel however is not obtained from

crude oil

it is a fatty acid ester

okay so this is a carboxylic acid

derived from a fat

turned into an ester typically a methyl

ester

sometimes it can be an ethyl ester

okay but they it's a small

alcohol that is added to the

large fatty acid in order to

create biodiesel okay so the long chains

can be saturated carbon-carbon bonds or

unsaturated carbon-carbon bonds and

you'll notice when we talk about the

saturated or unsaturated

we specify that we are talking about the

carbon-carbon bond within the chain

okay and that's critical when you're

talking about these if you just say

the carbon bonds or things like that or

the bonds

you're going to be marked incorrect you

do want to specify when you're talking

about it that all carbon carbon bonds

are single and then if we're talking

unsaturated that there is at least one

carbon double bonded to another carbon

so this is formed by the reaction of a

triglyceride

okay which you remember from the other

video is our

glycerol backbone with our long

hydrophobic tails attached and they are

what we get from all fats and oils

have this structure okay

so all fats and oils have this structure

um and we'll look at it a bit more in

detail in the next few slides

so this is what biodiesel looks like

here we can have a

large hydrophobic region

okay which is non-polar this part of the

molecule is

non-polar and then we have the polar

ester group

okay and this is made by the this came

from the methanol

and the fatty acid to make our ester

so here we see the triglycerides so this

is what we

obtain from fats and oils remembering

fats

are more saturated oils

tend to be unsaturated

okay so when we extract

oils and fats we get a triglyceride

which

is the three strands attached to the

glycerol backbone

okay what happens is we place this into

a reaction vessel

and in the presence of a strong base

okay because the hydrolysis of the ester

is base catalyzed

which is the breaking of that ester

is base catalyzed and

there's usually a catalyst so this is

our base catalyst for breaking apart

the triglyceride

we have three equivalents of methanol

also

in the flask so this is allowed to react

with heat and what we will end up

producing

is the three lots of biodiesel

which is a methyl ester we've added the

methyl group onto here

so this is broken apart and create the

carboxylic acid

and then we get condensation of the

alcohol onto the carboxylic acid group

the other thing it will produce is it

will produce one molar equivalent

of glycerol so we have one triglyceride

is to three methanol which produces

three biodiesel and one glycerol

the structure for glycerol and your

fatty acids are given in your data

booklet

so let's talk about polarity and you may

recognize this diagram here

petra diesel is non-polar it's a

non-polar

hydrocarbon the only forces therefore

the act between petrodiso molecules are

dispersion forces

biodiesel has a polar functional group

the whole molecule isn't necessarily

highly polar

it does have a large non-polar chain

but where the ester functionality is

we can see that there is this delta

minus delta plus

dipole going on so we have a

polar functional group in this region

that means that where the ester

functional group is

it is able to create dipole dipole

dipole-dipole bonds between

neighboring biodiesel molecules

okay so this changes its properties

one of the properties that changes is

its hydroscopy and you may remember

this word from when we talked about

sodium hydroxide we talked about

hydroscopy or

deliquescence so hydroscopy in this case

is it's able to absorb moisture from

the environment and this is because it

interacts with water molecules

because of the polar nature of the ester

group it's able to attract water

molecules

to it okay and in this case

they will form hydrogen bonds this is

because the water

okay is a hydrogen bondo and the ester

group is a hydrogen bond acceptor

with no water around there will be

no hydrogen bonding between the

molecules

in an exam if you're afraid of mixing

this up you could refer to it as a

dipole-dipole interaction

and still be okay but water

the water is forming the hydrogen

bonds okay

to the ester when

it is just an ester ester ester it's

going to be dipole dipole only okay

so ester molecules cannot form hydrogen

bonds with themselves they

only form hydrogen bonds with water

so because of this polar group it means

that it can absorb water molecules so

that makes it hydroscopic we get water

trapped into the fuel and as you can

imagine this can reduce its energy

density when it's burnt

biodiesel will also have a higher

viscosity we've talked about this as

being resistance to flow

so high viscosity fluids is something

like honey that is

thick okay and will

thin down when we heat it and that's

because we'll

lessen the effect of the intermolecular

forces with heating

so it has a higher viscosity than

petrodiesel

because of the stronger intermolecular

bonding the dipole dipole forces as well

as the dispersion forces

and as a number of you have noted a lot

of biodiesel molecules are actually

bigger than some of the molecules that

we see within petrodiesel so that

increased dispersion forces as well

and the biodiesel has a higher cloud

point cloud point is a measure of the

temperature where solid crystals start

to form so as it starts to cool down

we'll start to see solid crystals

forming in it

as you can imagine if we make biodiesel

from saturated fats

then this point is actually at a higher

temperature

and this can change the temperatures of

which biodiesel is able to be used at

so it has a higher cloud point where

cloud

point is the temperature where the solid

crystals begin

to form and our biodiesel will start to

lose its ability to flow

it starts to solidify

so if we compare these we can see that

the different density viscosity cloud

point

energy content and energy density are

able to be compared between the two in

terms of

density in terms of mass per volume

petrodiesel

and biodiesel are similar but biodiesel

is a little bit more dense

okay so it'll be a bit it will weigh a

bit more for the same volume

the viscosity of biodiesel is actually

almost twice

that of petrodiesel the cloud point of

biodiesel is from negative 3

to 12 degrees whereas petrodiesel is

negative 15 to 5.

so this is much greater problems to

people wanting to use biodiesel

in equipment or cars that will be

operating at temperatures

under zero degrees or sitting around in

temperatures under zero degrees in

places like canada

the energy content for biodiesel is a

little bit smaller

and the energy density so this is energy

per kilogram

but the energy density per liquid of

fuel

is a bit lower as well so we get less

energy

per liter or per gram of fuel

so we've looked at the cloud point

we've looked at energy we've looked at

the physical properties and viscosity

so now we want to look at the

environmental impact

as we've been talking about a lot of

these are going to refer to carbon

neutrality

sustainability all those things when

we're comparing fossil fuels to some

other more popular

or more currently used biofuel options

the carbon dioxide emission from both

petrodiesel and biodiesel are about the

same

okay which is about the same as petrol

this means

that the carbon released on combustion

okay is the same roughly for both of

them

the diesel bridge vehicles produce 10 to

20

less than co2 than petrol engines okay

so pure

diesel engines produce less co2

and biodiesel produces much the same as

petroleum

okay the good thing about biodiesel

though is that the co2 release during

combustion

is theoretically reabsorbed by the

plants during photosynthesis

for its production okay we've talked

about this

we know that that is not necessarily

taking into consideration transport or

manufacture

but purely for the sourcing of the oil

okay it's never entirely carbon neutral

as there is energy expended in refining

and transport that releases

more co2 okay so

that covers our environmental impact

this question here is in your question

packet i'd like you to have a go at

doing it and we're going to go through

it

in class to look at it because there's a

number of things that we'll talk about

in regards to bonding

with this question but other than that

that's it from me for this video i'll

see you in class

and we will wrap up all the information

that we have done

regarding fuels ready to move on and

talk about

combustion and thermochem equations i'll

see you in class