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TU2 - Refining and Gas Processes > Automotive Fuels > Flashcards

Automotive Fuels Flashcards

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 ?

A

Alkylates are interesting because they enable high octane number without aromatics

24
Q

What does LVN stand for ?

A

Light Virgin Naphtha

25
Q

Where do LVN and IVN come from ?

A

LVN and IVN come from straight run gasoline

26
Q

What should LVN contain ?

A

LVN should contain C5 and C6

27
Q

Where is LVN sent ?

A

LVN is usually sent to isomerization units to produce paraffins

28
Q

What should IVN contain ?

A

IVN should contqin C7+ molecules (to avoid benzene)

29
Q

Where is IVN usually sent ?

A

IVN is usually sent to reforming unit

30
Q

What are LCN and HCN ?

A

LCN is Light Cat Naphtha and HCN is Heavy Cat Naphtha

31
Q

Where do LCN and HCN come from ?

A

They come from FCC gasoline

32
Q

Why are LCN and HCN separated ?

A

LCN is olefin rich but not too aromatic while HCN is aromatic rich with a moderate amount of olefins

33
Q

Why do we have ASTM specifications ?

A

ASTM enables us to check that the gasoline is homogeneous and that we will get a smooth combustion

34
Q

What are the specs related to ASTM ?

A

We check IBP, EBP and % of gasoline distillated at 70, 100 and 150°C

35
Q

Why do we check the volatility of the gasoline ?

A

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
Q

How is VP adjusted ?

A

We use butane to adjust the VP

37
Q

What does DVPE stand for ?

A

Dry Vapor Pressure Equivalent

38
Q

Why do refiners prefer to be close to the max VP spec ?

A
  • Gasoline must remain on spec until the filling station

- Economically interesting to sell butane at the price of gasoline

39
Q

What is the maximum benzene content in gasoline ?

A

Max 1% benzene in Europe

40
Q

What are the VP specs depending on the season ?

A
  • Summer : 45 kPa < VP < 60 kPa
  • Interseason : 60 kPa < VP < 90 kPa + VLI < 1150
  • Winter : 60 kPa < VP < 90 kPa
41
Q

Why do we check VLI in interseason ?

A

To check that we have a high VP and a large fraction distilled at 70°C

42
Q

What are the two possible routes for ethanol in France ?

A
  • Ethanol incorporated in a fuel

- Ether synthesized from alcohol and olefinic HC from FCC

43
Q

What is the maximum qty of ether that can be added in a gasoline ?

A

Maximum 15%

44
Q

What are the regulated pollutants at the exhaust of a gasolien engine ?

A

CO, NOx and unburnt HC

45
Q

What is the current sulfur spec for gasoline ?

A

Max 10 ppm

46
Q

Why do we have to redue the sulfur content in the gasoline ?

A
  • 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
Q

Why do we want to add oxygenated components in the gasoline ?

A
  • Favorable effect on CO and unburnt HC

- Allows the reduction of the benzene content

48
Q

What is the problem that we create by adding oxygenated compound in gasoline ?

A

We now form aldehydes (toxic)

49
Q

What is the maximum mercaptans content in gasoline ?

A

RSH content : max 15 mg/kg = 15 ppm

50
Q

What is the problem with cracked gasolines ?

A

They are chemically unstable (olefins) and can form gums

51
Q

What are gums ?

A

Gums are sticky polymers with a high tendency to plug filters and injectors
They also produce unburnt HC

52
Q

What are the two tools to monitor gums and gasoline stability ?

A

We measure both current/existing gums and potential gums

53
Q

What is the specification for current gums in gasoline ?

A

Max 5 mg/100 mL

54
Q

What is the specification of potentialgums in gasoline ?

A

Oxidation resistance of minimum 6h (at 100°C under O2 pressure)

55
Q

What kind of additives can we add to help with the chemical stability ?

A

We can use antioxidants

56
Q

What are the main gasoline bases ?

A
  • Isopentane (from LVN)
  • Isomerate (from LVN)
  • Reformate (from IVN)
  • Cracked gasoline (FCC, HCK or steam cracker)
  • Alkylates
  • Butane
  • Oxygenated compounds (MTBE/ETBE)
57
Q

Which is the highest value product from the possible gasoline bases ?

A

Alkylates is the highest value

TU2 - Refining and Gas Processes (14 decks)

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