FE6 VCE Unit 3 Comparing biodiesel and petrodiesel
Summary
TLDRThis 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
🔬 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.
🧪 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.
🌍 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.
Mindmap
Keywords
💡Petrodiesel
💡Biodiesel
💡Fractional Distillation
💡Aromatic Compounds
💡Triglyceride
💡Polarity
💡Hydroscopy
💡Viscosity
💡Cloud Point
💡Environmental Impact
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
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