fuels Flashcards
ecatalysts for esterification
KOH
NaOH
transesterification
chemical reaction where one ester is turned into another
transesterification
chemical reaction where one ester is turned into another
transesterification products
ester + glycerol
for fuels with a mixture of hydrocarbons, why can’t the heat content be expressed in kJ/mol
bc mixture of hydrocarbons, the molar mass of the fuel is unknown tf mol thus kj/mol cannot be determined
for fuels with a mixture of hydrocarbons, why can’t the heat content be expressed in kJ/mol
bc mixture of hydrocarbons, the molar mass of the fuel is unknown tf mol thus kj/mol cannot be determined
why must the water produced in the production of biodiesel be removed?
it will make the fuel less efficient
why is ethanol miscible in both water and petrol
bc polar hydroxyl group (-OH) can form hydrogen bonds with water
bc non-polar -CH2CH3 form attraction to petrol through dispersion forces
what type of molecule is biodiesel made of
long chain hydrocarbons (C8-C20)
why is
petrodiesel’s boiling point higher than ethanol’s
While H bonds bw ethanol’s molecules due to polar hydroxyl group is stronger vs dispersion forces, the length of chain and overall intermolecular dispersion forces bw petrodiesel are greater vs H bonds
why is methane from biogas less environmentally damaging vs leaving animal waste to decompose in fields
animal waste breakdown releases methane.
Collecting this animal waste and converting the methane released into biogas used for combustion reduces the release of methane. Althogh the combustion of biogas does release CO2 into the atmosphere, the impact this is on the environment is less than methane’s impact on the atmosphere.
why is methane considered a non-renewable source
bc methane can be sourced from fossil fuels formed from animal and plant material decomposing over millions of years thus cannot be replenished at the rate of consumption
how can methane be classified as a renewable resource
if it is sourced from resources that can regenerate quicker then the rate of consumption eg methanogenic microbes or plant waste
advantages of fuel cells vs combustion engine
- less intermediary steps tf more efficient energy conversion
- fuel cells are quieter
- fuel cells produce less total greenhouse gases
(- sometimes fuel in fuel cell has higher energy content than fuel in engine)
disadvantages of fuel cells vs combustion engine
- expensive to set up
if using hydrogen: - difficult to access and store hydrogen
- risk leaking H2 reacting explosively
what is a fuel
a substance that burns oxygen to release a usable amount of energy
safety implications for fuels
- fuels = low BP, FP and high flammability
- thus, they can easily combust and release large amounts of energy
- tf must be stored away from naked flames and be used in well ventilated areas (avoid suffocation)
when explaining differences in properties of fuels, focus on….
- size of molecules
- type of intermolecular bonds
flashpoint
the minimum temperature at which a particular organic compound gives off sufficient vapour to ignite in air
renewable fuels def
can be replensihed at a rate similar to which they are being consumed
- plants can be grown in a relatively short space of time tf converted into desired product for use in fuel
examples of renewable energy sources
- solar energy
- hydro-electricity
- wind turbine energy
- biofuels
non-renewable energy sources
- fossil fuels
- nuclear energy sources
energy transformations in a gas-fired powerplant with turbine
chemical -> thermal -> kinetic (steam) -> kinetic (turbine) -> electrocal
how are coal fired plants different from gas fired plants
coal contains carbon and sulfur -> dangerous w/a gas plants produce less pollution and lower sulfur levels
biofuel
fuel sourced from organic matter
biogas
gaseous fuel produced by the anaerobic breakdown of organic matter by bacteria
bioethanol
fuel produced by the fermentation of glucose in organic matter by yeast
pros of bioethanol
- renewable resource
- can be made from waste
- CO2 absorbed during photosynthesis offsets CO2 released during combustion
- fewer particulates produced than petrol
cons of bioethanol
- limited supply of raw materials from which to produce it
- lower energy content than petrol
- may require use of farmland otherwise used for food production
biodiesel
fuel produced by the esterification of fats and oils orginating from animal products or crops
otherwise known as methyl ester
reaction to form biodiesel
(w trigylceride)
alcohol + triglyceride -(KOH)-> biodiesel + glycerol
transesterification reaction
more ideal than from FA bc FA produces water which must be removed to enable biodiesel to be a fuel
pros of coal
- large reserves
- relatively high energy content
.
cons of coal
- non-renewable
- high levels of CO2 emissions
- less easily transported than liquid or gaseous fuels
pros of natural gas
- easy to transport through pipes
- relatively high energy content
- more efficient than coal for energy production
cons of natural gas
- non-renewable
- limited reserves
- polluting (but less than coal and petrol)
pros of biogas
- renewable
- CO2 adsorbed during photosynthesis offsets some CO2 released during combustion
- low running costs
cons of biogas
- low energy content
- supply of waste raw materials limited
pros of petrol
- high energy content
- ease of tansport
cons of petrol
- non-renewable
- polluting (less than coal)
- limited reserves
pros of LPG
- low cost
- easily separated from natural gas
- relatively high energy content
liquified petrolium gas
cons of LPG
- non-renewable
- polluting (less than coal)
advantages of biodiesel
- lower net CO2 emissions
- no sulfur tf zero SO2 emissions
- burns more completely bc of oxygen present (prescene of C=O makes it easier to oxidise thus combust)
disadvantages of biodiesel
- hygroscopic due to presence of ester link -> H2O can be suspended in mixture
- temp at which crystals form is higher -> poor fuel flow due to increased viscosity at lower temps
- cloud point is higher -> fuel flow and combustion is poor at lower temps
- presence of C=O means fuel is more susceptible to oxidation -> lower amount of nrg released during combustion
why must water be removed when producing biodiesel
it makes the fuel less efficient
in alkanes, as the C:H ratio increases
energy density decreases
viscosity
viscosity defines a fluid’s resistance to flow. The higher the viscosity of a liquid, the thicker it is and the greater the resistance to flow
as flashpoint increases, viscosity …
increases
how can hydogen be generated on water
electrolysis of water using energy from solar energy to power the electrolytic reaction
coal seam gas
- mostly methane
- found naturally in commerical quantities near coal deposits
