14. Gasoline

Question 1

■ Reid Vapor Pressure (RVP)?

Answer 1

■
The measure of volatility is vapor pressure.
Vapor pressure is a measure of the surface pressure it takes to keep a liquid from vaporizing.
Measured at 100ºF.

Question 2

■ Gasoline blending components?

Answer 2

■ 
▪ iC4
▪ nC4
▪ Reformate (Isoparaffins, Naphtenes, Aromatics)
▪ Alkylate (Isoheptane, Isooctane)
▪ SR Gasoline
▪ SR Naphta
▪ CAT-Cracked Gasoline
▪ Coker Gasoline

Question 3

■ How Gasoline burns?

Answer 3

■ Gasoline like other hydrocarbons does not burn in its liquid state, it has to be vaporized and mixed with oxygen to ignite.

Question 4

■ Cold starts, warmed up starts, restarted when it is hot comparisons.

Answer 4

■
▪ On cold starts — enough gasoline must vaporize (RVP 12 or more)
▪ On warm engine — the gasoline must not expand so much that it will replalce air. (less than 5 or 6)
▪ there is direct correlation between RVP and ability to meet different conditions.

Question 5

■ Why would refiners use normal butane instead of isobutane to pressure gasoline?

Answer 5

■
▪ The RVP of nC4 is less than iC4. More nC4 can be blended in than iC4.
▪ nC4 is more and plentiful in nature
▪ often refineries do not have enough iC4 to satisfy the appetite of the alky plant

Question 6

■ Octane number?

Answer 6

■
▪ The octane number of any gasoline blend or blending component equals the percent of isooctane/nheptane C8H18/C10H22 blend that knocks at the same compression ratio as the gasoline or component being evaluated.

▪ The smallest compression where a gasoline starts to knock is measured against an arbitrary scale called octane numbers.

Question 7

■ How to measure octane number?

Answer 7

■
▪ Two blends of iC8 and nC7, one that the tester guesses will knock at a higher compression ratio and one at a lower ratio.
▪ The octane number of these blends are known by definition - the percent iC8.
▪ Increasing compression ratio at some point knocking will occur.
▪ Compression ratio Noted.
▪ Considering 2 results on a graph(compression/octane number) we perform a calibration.
▪ next knocking of tested gasoline will reveal us compression ratio. Considering precious results of tested blends will help us to examine iC8 number for our tested fuel

Question 8

■ Type of octane numbers?

Answer 8

■
▪ RON (Research Octane Number)
▪ MON (Motor Octane Number)

Question 9

■ Leaded Gasoline?

Answer 9

■ Until 1970s refineries added lead to gasoline to increase the octance number.
▪ Tetraethyl lead (TEL) proibited

Question 10

■ How do refiners blend gasoline now to mitigate environmental harm?

Answer 10

■ TOX, NOx, VOCs, SOx
▪ Toxic Compounds
▪ Nitrogen Oxids
▪ Volatile Organic Compounds
▪ Sulphur Oxides
■ Butane evaporates or leak out of the gas tanks
■ Benzene identified as a carcinogenic threat
■ Other Aromatic compunds could result in unburned emissions incl. benzene
■ NOx and VOCs react with sunlight and create smog.