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Chemistry (Production of Materials) > 1. Fossil Fuels and Ethylene > Flashcards

1. Fossil Fuels and Ethylene Flashcards

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1
Q

Describe the composition of Petroleum (Crude oil).

A

A mixture of hydrocarbons, consisting mainly of alkanes and cycloalkanes.

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2
Q

Define fractional distillation

A

Process to separate a mixture such as petroleum into its compounds according to their boiling points

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3
Q

Difference of boiling points in fractional distillation?

A

50 degrees celsius.

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4
Q

Why must crude oil be refined?

A

Crude oil must be refined by fractional distillation to obtain raw materials to make plastics, polymers and fuels.

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5
Q

What are light crudes?

A

High concentration of gasoline and kerosene

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6
Q

What are heavy crudes?

A

High proportions of higher BP compounds.

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7
Q

What is the sequence in fractional distillation? From top to bottom.

A
  • Light gases
  • Gasoline
  • Naptha
  • Kerosene
  • Gas Oil
  • Lubricating Oil
  • Residue
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8
Q

IUPAC name for Ethylene

A

Ethene

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9
Q

Main sources of Ethene?

A

Australia and USA: Piped natural gas directly, and cracked into ethane, propane to obtain ethylene.

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10
Q

Define cracking.

A

Cracking is a process in which molecules of carbon compounds are broken down into smaller molecules with lots of heat/ catalyst.

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11
Q

Define catalytic cracking.

A

High molecular weight (BP) fractions converted into lower molecular weight (BP) using a catalyst

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12
Q

Why is catalytic cracking carried out?

A

To increase the output of high demand products.

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13
Q

Define cat cracker.

A

Column which catalytic cracking occurs.

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14
Q

What is an alkane broken into during cat cracking?

A

Alkanes are broken into two smaller molecules- alkAne and alkEne.

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15
Q

What is a catalyst used in catalytic cracking?

A

Zeolite

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16
Q

What is the composition of Zeolite?

A

Crystalline aluminosillicates (Al + Si +O2 + metal ions)

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17
Q

What is the structure of Zeolite which makes it such an effective catalyst?

A

It has tunnels and cavities through and in molecules. This gives it large surface area per unit mass.

18
Q

What happens during Cat cracking?

A

Starts on the inner surface of molecule. Catalyst absorbs reactants in zeolite pores, weakening their bonds and reducing activation energy. High internal surface area.

19
Q

At what conditions does Cat cracking occur?

A
  • 500 degrees celsius
  • Above atmospheric pressure
  • No air.
20
Q

Define steam cracking.

A

A non-catalytic process. A form of thermal cracking in which a mixture of alkanes is fed through:
- A hot metal pipe with steam to decompose.
Into small alkanes such as ethene, propene and butene.

21
Q

Define Thermal cracking

A
  • Heating the fraction to very high temperatures in the ABSENCE OF AIR
  • Expensive: energy required to maintain high temperatures.
  • Difficult to control and produce: bond breaking could occur anywhere.
22
Q

Describe features of furnaces.

A
  • Produces yields of C2H4
  • 100 pyrolysis coils/ 80 m in length
  • Feedstocks are heated (750- 900 degree celsius)
23
Q

Describe Intitiation

A

Free radicals are produced when hyrdrocarbons are split into fragments. Reactive due to presence of unpaired electron.

24
Q

Describe Propagation

A

Free radicals propagate to produce smaller free radicals and release small alkenes such as C2H4

25
Q

Describe Termination

A

Hydrocarbon molecules can reform when free radicals react with each other.

26
Q

Why are alkanes relatively unreactive?

A
  • Saturated Compounds
27
Q

What are the two important reactions of alkanes?

A

Combustion and Reactions with Halogens

28
Q

What does combustion of alkanes produce?

A

Carbon dioxide and water

29
Q

What is required for alkanes to react with halogens?

A

UV light

30
Q

Describe alkane + halogen reactions?

A

This is a substitution reaction as hydrogen atom from an alkane is replaced by a halogen atom.
Excess halogen can replace remaining hydrogen atoms.

31
Q

Why are alkEnes very reactive?

A

Presence of double bond.

32
Q

How is alkene undergo addition reactions?

A

Double bond opens up to provide two single bonds where now new substances can add on.

33
Q

What reacts with alkene?

A
  • Halogens
  • Hydrogen Halides
  • Water
  • Hydrogen
34
Q

How many products are formed in addition reaction?

A

One

35
Q

Ethene + Bromine

A

1,2- dibromoethane

36
Q

What is HOBR

A

HOBR is hydrobromine acid which forms when bromine reacts with water molecules.

Br (aq) is when Br is dilluted with water.

37
Q

C3H6 +HBr

A

2- bromo propane

38
Q

Describe the test you would use to distinguish alkane and alkene.

A
  • Bromine water added (red-brown colour, and see if it reacts)
  • Alkene: Undergo addition reaction, and bromine will change from red-brown to colourless very quickly.
  • Alkane: Undergo substitution reaction very slowly in the presence of UV light.
39
Q

Safety precaution when handling bromine

A

Bromine is corrosive.

  • Use fume cupboard
  • Use very small quantities of chemicals
  • Wearing labcoats
  • Warft the smell using hands instead of inhaling directly.
40
Q

During hydration reaction with Alkenes (Alkene + Water), what is the catalyst?

A

SO4

Chemistry (Production of Materials) (3 decks)

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