This document discusses the blending process for gasoline. It contains the following key points: 1. Gasoline is blended from various components like butane, isomerate, reformate, etc. to achieve the desired vapor pressure and octane number. 2. The vapor pressure and octane number of the blended gasoline is calculated using blending indices that take into account the properties and proportions of the individual components. 3. Octane improvers like MTBE can be added to boost the octane number of the blend if it is below the target value. The amount of MTBE required is calculated based on its octane contribution.

1. Chapter Ten: Blending process
1

2. Blending process
2

3. 3

4. Components of the Gasoline Pool
• Butane
• Isomerate
• LN
• Alkylate
• Reformate
• FCC
• HN
All have different
properties
Lots of
different Grade
4

5.  Gasoline is blended with n-butane to promote high antiknock
quality, ease of starting, and quick warm-up.
 The vapor pressure [expressed as the Reid vapor pressure
(RVP)] of gasoline is a compromise between a high RVP to
improve economics and engine starting characteristics and a
low RVP to prevent vapor lock and reduce evaporation losses.
 RVP of gasoline changes with the season of the year and
varies between 7.2 psi (49.6 kPa) in the summer and 13.5 psi
(93.1 kPa) in the winter.
Gasoline Blending with n-Butane

6. The desired RVP of a gasoline is obtained by blending
gasoline with n-butane. The amount of n-butane
required to give the needed RVP is calculated by:
6

7. 7
RVP of water ~6.60 kPa

8. is mole fraction
8
   




n
i
i
i
RVP
i
x
t
RVP
1
Reid vapor pressure Partial vapor pressure=RVP*xi

9. Vapor pressure blending indices (VPBI) have been compiled as a function of the RVP
of the blending streams
Reid vapor pressure of the blend is closely approximated by the sum of all the
products of the volume fraction (v) times the VPBI for each component.
In the case where the volume of the butane to be blended for a given RVP is desired:
Using Vapor Pressure Blending Indices (VPBI)
9
 




n
i
i
i
VPBI
i
V
VPBI
1

10. Although this differs slightly from the result obtained in Example 1, they agree well
within the limits required for normal refinery operation.
BPD
BPD
10

11.  RON (Research Octane Number) is determined in a single
cylinder variable compression ratio engine that operates at 600
rpm with a 65.6 ºC inlet air temperature.
 MON (Motor Octane Number) is determined at engine speed
of 900 rpm and 148.9 ºC inlet air temperature.
Octane number : Is a measure of a gasoline’s resistance to knock in a cylinder of
a pertol engine.
 The higher octane number, the higher the resistance to knock, the higher is the
efficiency of the fuel to produce work.
Usually RON> MON
RON-MON=sensitivity of the gasoline
Blending Based on Octane Number

14. RON=95.0
MON= 89.4
PON= (95+89.4)/2=92.2

15. 15
93.52
Assume that we need the PON of the above pool to be at least 95.
How can we achieve that?

16. Octane improvers
16
MTBE is the typical octane enhancer
(tertiary amyl methyl ether)
(methyl tertiary butyl ether)
(ethyl tertiary butyl ether)
(
tetra ethyl lead
) 11,500

17. METHYL TERTIARY BUTYL ETHER
• Any hydrocarbon stream containing isobutene can be used for the production
of MTBE.
• Methanol reacts with isobutene to form MTBE.
• The etherification reaction is conducted in the presence of a catalyst that is
cationic resin and strongly acidic. These resins are produced by sulfonation of
a copolymer of polystyrene and divinyl benzene.
• These catalysts are very sensitive to impurities, which could destroy their
acidic function, and high temperatures, which could remove the sulfonic bond.
17

18. METHYL TERTIARY BUTYL ETHER
• A number of secondary reactions can also occur, depending on
the operating conditions and feed impurities, such as:
18

19. Adding MTBE to enhance PON
19
How much MTBE (MW= 88 g/mol, RVP=9 psi) will be required to obtain 95 PON. The MON
and RON of MTBE are 101 and 118, respectively. Is the resulted blend suitable for very hot
weather?
93.52
RVP
(psi)

20.  Blending of viscosities may be calculated conveniently by using viscosity factors. In
equation form:
 The pour point index of the blend is the sum of the products of the volume fraction
times the pour point blending index (PPBI) for each component, or

21. 21
End of Blending