Catalyst

Catalyst

A substance that affects the rate of a reaction but
emerges from the process unchanged

Catalyst can affect both the
yield and productivity(create different pathway with a
lower energy barrier)

Catalyst speed up reaction accelerate or slow the formation of a particular product species

Change only the rate of reaction (not affect the equilibrium)

catalysis

The study and use of catalyst and catalytic processes

Homogeneous

A cataltic process in which a catalyst is in solution with atleast one of thw reactants

Example : Industrial Oxo processfor manufacturing normal isobutylaldehyde.

Heterogeneous

A process involves more than one phase (usually the catalyst is a solid)

Example : Production of benzenefrom the hydrogenation of cyclohexane (obtained from distillation of crude petroleum) using platinum-on-alumina as the catalyst.

More common type used in industrial

Occurs at or very near the fluid-solid interface

Reaction between gasses and liquids are usually mass transfer limited

Solid interface

a large interfacial area

provide by inner porous structure

Typical silica

Poisoned catalyst

treatment with oxygen at low oxygen partial pressure

treatment with steam at 700-800 degree celcius

Coked catalyst

gasification with O2, H2O, CO2 and H2

Redispersion of sintered

High-temperature treatment oxychlorination

Porous

A catalyst has a large area resulting from porous.

The porescan control the residence time of various molecules

Molecular Sieves

A catalyst that admit small moleculesbut prevent
the large molecules from entering it

Monolithic

A catalyst that can be either porous or non-porous which is normally encountered in processes where pressure dropand heat removalare major consideration.

The active materialis a pure metalor metal alloy.

Require a high surface area supportto disperse the primary catalyst.

Supported

A catalyst consists of minute particles of an active
material dispersed over a less active substance

The active materialis a pure metalor metal alloy.

Require a high surface area supportto disperse the primary
catalyst

Unsupported

A catalyst distinguishes from supported catalyst.

Usually very active catalyst that do not require high surface
area

used for high temp

power station

oil rige

industrial gas

the lost of catalytic
activitydue to loss of active site surface resulting from the
prolonged exposure to high gas-phase temperature

This mechanism common for the rxn involve the hyrocarbons.

It results from a carbonaceous (coke)material being deposited
on the surface of catalyst.btopic

the poisoning molecules become irreversibly chemisorbed to active sites, thereby reducing the no of sites availablefor the main rxn