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ReFuPP > F3 Catalysis > Flashcards

F3 Catalysis Flashcards

1
Q

What is a catalyst?

A

It is a substance that increases the reaction rate of transforming reactants into product, through a repeated cycle of elementary steps where the catalyst always is regenerated at the end of each cycle during the catalysts lifetime.

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2
Q

Different types of catalyst deactivation

A
  • Aging (thermal deactivation, sintering - of active material or of washcoat)
  • Coking (fouling - accumulation of unwanted material on solid surfaces)
  • Poisoning
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3
Q

Arrhenius Law

A
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4
Q

The graphs depicting the temperature dependence of k in Arrhenius Law

A
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5
Q

Is the equilibrium altered when lowering the activation energy Ea?

A

No, the equilibrium Keq = [B]eq/[A]eq is unaltered! Only the rate is changed.

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6
Q

Major applications of catalysts?

A

Chemicals (bulk, fine and specialty)

Emission control

Fuels

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7
Q

Homogenous vs Heterogeneous catalyst

A

Homogeneous catalyst: when the catalyst and the reactants are in the same phase

Heterogeneous phase: when the catalyst and the reactants are in different phases

Different phases can be if components are of different physical states (ex solid or liquid), or if the components are of same physical state but not uniformly mixed (ex water and oil)

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8
Q

Study the ozone depletion in F3, slide 25.

A

Starts with: O2 + uv → 2O*

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9
Q

Advantages of Homogeneous catalysts

A
  • Catalyst in solution (metal is exposed)
  • Active at low temperature (per metal center)
  • High dispersion rates (minimisation of catalyst poisoning)
  • High utilisation
  • High productivity
  • High selectivity (usually one active site)
  • Well defined-possibility to study (modification surface with ligands)
  • Liquid phase (temperature control is easy)
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10
Q

What is Biodiesel? (what oils?)

A

Biodiesel is the collective name for a variety of ester-based fuels (fatty ester), generally defined as the mono-alkyl esters converted from vegetable oils. Biodiesel is as efficient as petroleum diesel in diesel engines.

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11
Q

Different feedstock oil for biodiesel

A
  • Corn
  • Cottonseed
  • Palm
  • Peanut
  • Rapeseed
  • More sustainable ones:
  • Soybean
  • Sunflower
  • Rest frying
  • Jatropha
  • Algea
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12
Q

What is Transesterification?

A

Reaction between alcohol (methanol) and triglyceride → mixture of mono-alkyl esters and glycerol.

(free fatty acids in Jatropha are approx. 14%)

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13
Q

What is the difference between FAME (fatty acid methyl ester) and RME (rapeseed methyl ester)

A

FAME är samlingsnamnet för biodiesel som tagits fram genom förestring (transesterification) av vegetabiliska oljor, och RME tillhör denna grupp men är specifikt för biodiesel som framställts av rapsolja.

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14
Q

Input and output in RME production

A
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15
Q

How is heterogeneous catalysis compared to homogeneous?

A

Heterogeneous can be seen as the work horse compared to the fancy horse being homogeneous.

Heterogeneous:
Easy catalyst separation (easy to seperate the fluid product from the solid catalyst)
Flexibility in catalyst degeneration
Less expensive

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16
Q

What does the catalyst consist of?

A

The catalyst consists of three main components:

Substrate
Washcoat (serves as the carrier of a precious metal catalyst)
Active phase (provides the active site for catalytic reactions, often metals, metal oxides or metal sulphides)

They can all be in different or the same material

17
Q

What is the support material in a catalyst?

A

Support materials are often metal oxides or various carbons. In a catalyst it facilitates the dispersion and stability of the active phase.
The support material may influence the catalytic activity through catalytic phase-support interactions.

18
Q

What is a promoter and what are the two types?

A

A promoter is added to a solid catalyst in small amounts in order to enhance its performance in a chemical reaction.

Textural promoters help maintain high dispersion of active phase on the support (dessa ser alltså till att den aktiva fasen är utspridd på support phase)

Chemical promoters increase activity and/or selectivity

19
Q

What is the lifetime of a catalyst (different ones)

A
20
Q

What does sintering of washcoat mean?

A
21
Q

What does sintering of active material mean?

A
22
Q

What does selective poisoning of active sites mean?

A
23
Q

What does fouling of washcoat mean?

A
24
Q

What are the steps in a Heterogeneous catalytic reaction

A

ReFuPP (12 decks)

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