Lecture 23 thursday 4 1 08 ocnb explosion noble prize 2007 catalytic steps
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Lecture 23 Thursday 4/1/08 OCNB Explosion Noble Prize 2007 Catalytic Steps. 400. Temperature o C. Cooling Restored. Q r = 0. Isothermal Operation. 200. 175. 9:55 t = 0. 10:40 10:50. midnight 12:18. Temperature-time trajectory. fuse. Catalysts and Catalysis.

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Lecture 23 thursday 4 1 08 ocnb explosion noble prize 2007 catalytic steps
Lecture 23 Thursday 4/1/08OCNB ExplosionNoble Prize 2007Catalytic Steps


Temperature time trajectory

400

Temperature oC

Cooling Restored

Qr = 0

Isothermal

Operation

200

175

9:55

t = 0

10:40 10:50

midnight 12:18

Temperature-time trajectory

fuse


Catalysts and catalysis
Catalysts and Catalysis

A Catalyst is a substance that affects the rate of chemical reaction but emerges from the process unchanged.

Catalysis is the occurrence, study, and use of catalysts and catalytic processes.

Approximately 1/3 of the GNP of materials produced in the U.S. involves a catalytic process.


Catalysts affect both selectivity and yeild
Catalysts affect both Selectivity and Yeild



Active site
Active Site

  • Reactions are not catalyzed over the entire surface but only at certain active sites or centers that result from unsaturated atoms in the surface.

  • An active site is a point on the surface that can form strong chemical bonds with an adsorbed atom or molecule.




The rate limiting step which step has the largest resistance
The Rate Limiting Step:Which Step Has the Largest Resistance?


Octane numbers
Octane Numbers

Catalytic Reforming

Normal Pentane Octane Number = 62

Iso-Pentane Octane Number = 95


  • Intro to Catalysis

  • Reforming catalyst –

  • Algorithm

  • Postulate a mechanism

  • Postulate a rate-limiting step

  • Express Ci·s in terms of partial pressures

  • Site balance (Total number of sites constant)

  • Derive rate law

  • Evaluate parameters

Pt (sputtered on)

Al2O5 (scaffold)


CV=concentration of vacant sites

Postulate a mechanism: (single site)

In 75% of heterogeneous catalysis, surface reaction is the slow step


Site Balance:

Is this consistent with the data?

Linear when PNi0 is low

Low slope when PNi0 is large

rNi0

PNi0

Consistent!!


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