3 Oxidation mechanisms of fuels

Question 1

Characteristics of Alkanes (Paraffins)

Answer 1

• C(m)H(2m+2)

- single-bond

Question 2

What’s the smallest alkane?

Answer 2

CH4, methane

Question 3

Which is the major component of natural gas?

Answer 3

Methane

Question 4

Which fuels have C(m)H(2m)?

Answer 4

• Cycloalkanes

- Alkanes (Olefins)

Question 5

Characteristics of Cycloalkanes

Answer 5

• C(m)H(2m)
• single-bond
• ring structured

Question 6

Characteristics of Alkenes

Answer 6

• C(m)H(2m)

- 1 double bond, rest single bond

Question 7

Characteristics of Polyolefins

Answer 7

• C(m)H(2m-2(n-1))

- more than one double bond

Question 8

Characteristics of Alkynes (Acetylenes)

Answer 8

• C(m)H(2m-2)

- 1 triple bond

Question 9

Characteristics of Aromatics

Answer 9

• ring-structured

- ring contains 6 carbon atoms

Question 10

Name some aromatics

Answer 10

• Benzene (C6H6)
• Naphtalene (C10H8)
• Biphenyl (C12H10)

Question 11

Do Alcohols (R-OH) or Hydrocarbons (R-H) have higher heats of comubtions?

Answer 11

Alcohols have lower heats of combustion

Question 12

Name other important fuels

Answer 12

• Ammonium perchlorate

- Hydrazine

Question 13

Which initiation reactions are possible for a H2-O2 system?

Answer 13

1. Dissociation of H2 (at high T)
2. Dissociation of O2
3. Reaction between H2 and O2

Question 14

Which are the major species in a H2-O2 system?

Answer 14

H2
O2
H2O

Question 15

Which are the minor species in a H2-O2 system?

Answer 15

H
O
OH
OH2
H2O2

Question 16

Why is it difficult to sustain a dry CO-O2 flame?

Answer 16

Beause the reaction between CO and O2 has

a high actigation energy and is a very slow process

even at high temperatures.

Question 17

Why isn’t it possible to sustain CO/O2 flames in the laboratory?

Answer 17

The oxidation of CO is a high activation energy reaction with

low heat release that

cannot sustain its forward progress.

Question 18

Which are the two most important reactions in a comubstion process of hydrocarbon oxidation?

Answer 18

H + O2 -> O + OH

CO OH -> CO2 + H

Question 19

What’s the main chain-branching reaction?

Answer 19

H + O2 -> O + OH

This reaction has a large activation energy.

Question 20

Features of chain branching reactions

Answer 20

• endothermic
• large activation energy
• sensitive to pressure