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TU2 - Refining and Gas Processes > Automotive Fuels > Flashcards

Automotive Fuels Flashcards

(57 cards)

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1
Q

What are the four main properties important for a gasoline

A
  • Combustion : high resistance to auto-ignition
  • Volatility
  • Pollution / Corrosivity (sulfur and benzene content)
  • Stability
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2
Q

Which particular property is adjusted for each country, even in Europe ?

A

Specs related to volatility are adjusted depending on the climate of each country

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3
Q

What is one major problem that we want to avoid during combustion of automotive fuels ?

A

We want to avoid knocking effect due to auto-ignition

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4
Q

What is Knocking ?

A

Knocking occurs when we have uncontrolled auto-inflammation of the fuel/air mixture in different zones of the combustion chamber. It leads to overheating of the engine

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5
Q

What conditions favor knocking in the cylinder ?

A

High pressure and/or temperatures, but also poor homogeneity of the air/fuel mixture favor knocking

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6
Q

How can we detect knocking ?

A

Knocking can be detected by a characteristic metallic noise

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7
Q

What is the parameter measured to control auto-ignition of a gasoline blend ?

A

We use the octane number

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8
Q

What is the name of the engine that enables the calculation of the octane number ?

A

The octane number is measured on the CFR engine

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9
Q

Which molecules are the two references for the measure of the octane number ?

A

The two references are isoOctane (2,2,4-triméthylpentane) and n-heptane

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10
Q

What do RON and MON stand for

A

Research Octane Number and Motor Octane Number

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11
Q

What is the difference between RON and MON

A

The RON measures the octane number simulating the conditions of a cold engine while the MON measure the octane number for an engine that has been running for a while

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12
Q

What is the European specification for RON/MON of the two Unleaded Super and LPG fuel ?

A
  • Unleaded Super 98 : RON 98 / MON 87
  • Unleaded Super 95 : RON 95 / MON 85
  • LPG Fuel : RON - / MON 89
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13
Q

Why do LPGs have such a high MON ?

A

From the PIANO table we would expect bad performance but actually, LPG are made of very small paraffins which are very stable and therefore are good to resist auto-ignition

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14
Q

How are US specs regarding octane number different from European ones ?

A

In Europe RON and MON have different specs while in the US, there is only one spec on the arithmetic mean of the two values

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15
Q

Why are the two main families of components of gasoline good ?

A

We want to avoid auto-ignition :

  • aromatics are very stable
  • isoparaffins are stable thanks to tertiary and quaternary carbons
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16
Q

How good is the RON for the main families of components ?

A
  • nP : very low
  • iP : high
  • A : very high
  • N : medium
  • O : medium
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17
Q

How good is the MON for the main families of components ?

A
  • nP : very low
  • iP : very high
  • A : high
  • N : medium
  • O : medium
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18
Q

What is the RON and MON for FCC gasoline ?

A

RON ok but low MON because of high content of olefins

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19
Q

Why is the MON of FCC gasoline low ?

A

Because of the high olefin content

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20
Q

How is the RON and MON of butane ?

A

It’s a short molecule so very stable -> good RON and MON

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21
Q

How is the RON and MON of reformate ?

A

The RON is excellent and MON ok because of high aromatic content

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22
Q

How is the RON and MON of alkylates ?

A

The RON is good and the MON is excellent because of the high isoparaffinic content

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23
Q

Why are alkylates very interesting nowadays for RON and MON ?

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A

Alkylates are interesting because they enable high octane number without aromatics

24
Q

What does LVN stand for ?

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A

Light Virgin Naphtha

25
Where do LVN and IVN come from ?
LVN and IVN come from straight run gasoline
26
What should LVN contain ?
LVN should contain C5 and C6
27
Where is LVN sent ?
LVN is usually sent to isomerization units to produce paraffins
28
What should IVN contain ?
IVN should contqin C7+ molecules (to avoid benzene)
29
Where is IVN usually sent ?
IVN is usually sent to reforming unit
30
What are LCN and HCN ?
LCN is Light Cat Naphtha and HCN is Heavy Cat Naphtha
31
Where do LCN and HCN come from ?
They come from FCC gasoline
32
Why are LCN and HCN separated ?
LCN is olefin rich but not too aromatic while HCN is aromatic rich with a moderate amount of olefins
33
Why do we have ASTM specifications ?
ASTM enables us to check that the gasoline is homogeneous and that we will get a smooth combustion
34
What are the specs related to ASTM ?
We check IBP, EBP and % of gasoline distillated at 70, 100 and 150°C
35
Why do we check the volatility of the gasoline ?
We have a minimum spec because we need a minimum amount of vapor to start ignition and a max to avoid losses of volatile components
36
How is VP adjusted ?
We use butane to adjust the VP
37
What does DVPE stand for ?
Dry Vapor Pressure Equivalent
38
Why do refiners prefer to be close to the max VP spec ?
- Gasoline must remain on spec until the filling station | - Economically interesting to sell butane at the price of gasoline
39
What is the maximum benzene content in gasoline ?
Max 1% benzene in Europe
40
What are the VP specs depending on the season ?
- Summer : 45 kPa < VP < 60 kPa - Interseason : 60 kPa < VP < 90 kPa + VLI < 1150 - Winter : 60 kPa < VP < 90 kPa
41
Why do we check VLI in interseason ?
To check that we have a high VP and a large fraction distilled at 70°C
42
What are the two possible routes for ethanol in France ?
- Ethanol incorporated in a fuel | - Ether synthesized from alcohol and olefinic HC from FCC
43
What is the maximum qty of ether that can be added in a gasoline ?
Maximum 15%
44
What are the regulated pollutants at the exhaust of a gasolien engine ?
CO, NOx and unburnt HC
45
What is the current sulfur spec for gasoline ?
Max 10 ppm
46
Why do we have to redue the sulfur content in the gasoline ?
- To protect the catalyc converter that enables to reduce the emissions of CO, Nox and unburnt HC - Because of its corrosivity - It forms sulfur oxides which are pollutants
47
Why do we want to add oxygenated components in the gasoline ?
- Favorable effect on CO and unburnt HC | - Allows the reduction of the benzene content
48
What is the problem that we create by adding oxygenated compound in gasoline ?
We now form aldehydes (toxic)
49
What is the maximum mercaptans content in gasoline ?
RSH content : max 15 mg/kg = 15 ppm
50
What is the problem with cracked gasolines ?
They are chemically unstable (olefins) and can form gums
51
What are gums ?
Gums are sticky polymers with a high tendency to plug filters and injectors They also produce unburnt HC
52
What are the two tools to monitor gums and gasoline stability ?
We measure both current/existing gums and potential gums
53
What is the specification for current gums in gasoline ?
Max 5 mg/100 mL
54
What is the specification of potentialgums in gasoline ?
Oxidation resistance of minimum 6h (at 100°C under O2 pressure)
55
What kind of additives can we add to help with the chemical stability ?
We can use antioxidants
56
What are the main gasoline bases ?
- Isopentane (from LVN) - Isomerate (from LVN) - Reformate (from IVN) - Cracked gasoline (FCC, HCK or steam cracker) - Alkylates - Butane - Oxygenated compounds (MTBE/ETBE)
57
Which is the highest value product from the possible gasoline bases ?
Alkylates is the highest value

TU2 - Refining and Gas Processes (14 decks)

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