Developing Fuels - Pollutants

Question 1

What primary pollutants can be produced by incomplete combustion in engines?

Answer 1

NO_x

SO₂

Unburned hydrocarbons (C_xH_y)

CO

C particulates

Question 2

Which pollutants does diesel produce more of?

Answer 2

Carbon particulates and unburned hydrocarbons as bigger hydrocarbons are used in diesel

Question 3

What are the effects of CO if it is inhaled?

Answer 3

It binds to the haemoglobin in the blood causing a lack of oxygen for respiration. Can be fatal.

Question 4

How is NO produced in an engine?

Answer 4

When the engine heats up, it causes the N and O in the air to react to form NO

Question 5

What are the effects of NO?

Answer 5

Reacts with water in clouds to produce nitric acid which causes acid rain

This can damage statues, buildings and kill wildlife

It also causes respiratory issues when inhaled and is a greenhouse gas

Question 6

How is photochemical smog produced?

Answer 6

When a mixture of pollutants are released in a condensed area

Question 7

What are the effects of photochemical smog?

Answer 7

Blocks sunlight

Produces secondary pollutants

Question 8

What are secondary pollutants?

Answer 8

Pollutants formed by primary pollutants eg ozone

Question 9

How is ozone formed as a pollutant?

Answer 9

produced in photochemical smog

Question 10

How is sulpher dioxide formed as a pollutant?

Answer 10

sulpher present in crude oil reacts with the oxygen in the air when hot enough

Question 11

What are the effects of SO₂?

Answer 11

same as NO:

acid rain

greenhouse gas

toxic

Question 12

How can sulpher dioxide polluting be prevented?

Answer 12

By using low-sulpher fuels

Mainly an issue with diesel and coal

Question 13

What is the purpose of catalyctic converters in engines?

Answer 13

It converts NO and CO into CO₂ and N₂

Question 14

What catalyst is used in catalyctic converters?

Answer 14

Pt/Rh alloy - known as ‘honeycomb’

Question 15

What is the reaction for the conversion in catalytic converters?

Answer 15

NO + CO -> CO₂ + 0.5N₂

Question 16

What are the issues with catalytic converters?

Answer 16

must be hot -> most NO and CO is produced before the engine is hot enough for the converter

finite lifetime as it is poisoned by unburnt carbon

Question 17

What are some alternative fuels for petrol and diesel?

Answer 17

Hydrogen

Biofuels

Biodiesel

Electric

Question 18

What are biofuels?

Answer 18

Usually ethanol from the fermentation of sugars

Question 19

What are the benefits of biofuels?

Answer 19

higher energy density than hydrogen

near;y carbon neutral

Question 20

What are the drawbacks of biofuels?

Answer 20

uses land that could be used for feeding people

absorbs moisture which leads to corrosion

lower energy density than biodiesel, petrol and diesel

Question 21

How is hydrogen used to fuel engines?

Answer 21

2H₂ + O₂ -> 2H₂O

reacts with oxygen to produce water

Question 22

What are the benefits of hydrogen as a fuel?

Answer 22

doesn’t produce pollutants other than NO

doesn’t release any carbon back into the atmosphere

Question 23

What are the drawbacks of using hydrogen as a fuel?

Answer 23

low energy density

issues with distribution and refueling - rare to find refuel stations

explosive

still get NO

extracted from natural gas (still releasing pollutants) or from electrolyisis (needs electricity)

Question 24

What is can biodiesel be made from?

Answer 24

waste that would otherwise go to landfill