Catalyst Design

Question 1

What is a black?

Answer 1

A ‘black’ is a metallic powder obtained by the reduction of
a metal salt or condensation of metal vapour

Skeletal metals are produced by leaching out one
component from an alloy, leaving the active species
behind ( e.g. Raney Nikel)

Question 2

Catalyst Example?

Answer 2

Oxidation of Ammonia - Platinum Gauzes

Methyl Alcohol oxidation to formaldehyde - Silver Granules

Hydration of acrylonitirile o acrylamide - Raney Copper

Question 3

Fused Oxide Catalysts

Answer 3

Low Surface Area, used in Ammonia Synthesis
N2 + 3H2 -> 2NH3

Fused Magnetite (Fe3O4)

Question 4

) Semi – conductor Oxides

Answer 4

ZnO, CdO, Fe2O3, V2O5, Ti O2 Ce O2

Question 5

Semi Conductor Oxide Example

Answer 5

TiO2 - used in photocatalysis reactions

Question 6

Acidic Oxides

Answer 6

Used in cracking reacions - e.g. paraffins to alkanes

examples are zeolites SiO2 - Al2O3.

Vanadium Pentoxide (V2O5 - in oxidation of n butane to maleic anhydride)

Question 7

Supported Metals

Answer 7

Fe, Co, Ni, used for Hydrogenation, oxidations

Question 8

Supported Catalysts

Answer 8

Supported Metals/Oxides
Allows: Greater surface area, inhibits sintering of small particles, allows different shapes/particle geometries
, can act as a co catalyst,

Question 9

Catalyst Properties

Answer 9

Physical
Mechanical, strength optimal bulk density, acts as heat source/sink,
diluent for active phase area, optimises catalyst porosity, optimises
metal crystal and particle size.

Chemical
inert to undesired reactions Stable under reaction/regeneration
conditions may interact with catalyst to improve activity/selectivity
stabilises catalyst against sintering reduces catalyst poisoning
effects.

Question 10

Monolith Catalysts

Answer 10

A ceramic block with straight channels
used in automobiles and flue gas cleaning
good because low pressure and anti fouling due to straight channels,

Question 11

Catalyst Support Materials

Answer 11

SiO2, Al203, Zeolite, Activated Carbon,

Question 12

Activated Carbon

Answer 12

Has surface interactions with oxygen containing groups

Advantages are:

Resistant to acidic/basic mixture
Stable at high temperatures up to 1000 K

Pore structure can be tailored by reaction

Porous carbons can be prepared with different physical forms

chemical nature of the surface can be modified

metal can be recovered by burning the support

cheaper than metal/silica

can behave as a molecular sieve

Question 13

Catalyst Preperation Sol Gel Method

Answer 13

Metal Salt Solution adjust the pH

Get a supersaturated solution , undergoes nucleation and growth and you get precipitation

you get a colloidal solution , which is aged and you get agglomeration

Get a hydrogel which you wash and filter and dry, get purification and concentration,

get a xerogel which you formulate and do pelletisaion/extrusion /spherezisation to get particles

Then you calinate these to get the catalyst

Question 14

Catalyst Impregnation

Answer 14

A support must have catalyst incorporated either by impregnation or co-precipitation

Precipitation, adsorption/ion exchange/
impregnation

Question 15

Catalyst Activation

Answer 15

Metal oxide catalyst does not require activation

If metal is required to be active then the catalyst is reduced in hydorgen - dry it, calcined in air , reduced in h2