Page 63 - Principles of Catalyst Development
P. 63
50 CHAPTER 4
TABLE 4.1. Types of Catalytic Materials
Type State Examples
I. Metals Dispersed Low: Pt/ AI,O" Ru/Si0 2
High: Ni/ AI,O" Co/kieselguhr,
Porous Raney, Ni, Co. etc.
Fe-AI,O,-K,O
Bulk Pt, Ag gauze
2. Multimetallic
clusters, alloys Dispersed (Pt-Re, Ni-Cu, PtAu)/AI,Oj, etc.
3. Oxides Single AI,O" Cr,O" V,O,
Dual, co-gels SiOrAI,Oj, TiO,-AI 2 0 j
Complex Ba TiO" CuCr,04, Bi,Mo06
Dispersed NiO/ AI,03' MoO,/ AI,O,
Cemented NiO-CaAI 20 4
4. Sulfides Dispersed MoS,/ AI,O" WS2/ AI,O,
5. Acids Dual, co-gels SiOrAI,O,
Crystalline Zeolites
Natural clays Montmorillonite
Promoted acids Super acids SbFs, H F
Supported halides
6. Bases Dispersed CaO, MgO, K2 0, Na20
7. Other compounds Chlorides TiCl,-AICl j
Carbides NiJC
Nitrides Fe2N
Borides Ni,B
Silicides TiSi
Phosphides NiP
8. Other forms Molten salts ZnCI" Na,CO,
Anchored homogeneous
catalysts
Anchored enzymes
4.2. METALS
Over 70% of known catalytic reactions involve some form of metallic
component,144l Industrially, metals are used in catalytic reforming, hydro-
cracking, ammonia and methanol synthesis, indirect coal liquefaction, oxi-
dation, and a vast number of organic hydrogenation and dehydrogenation
processes. Academically, metals are favored for research since they are
easily prepared in pure form and conveniently characterized. In fact, most
of the fundamental information leading to conceptual theories in catalysis
originated with studies on metal systems.
The periodic table for transition metals is shown in Fig. 4.1. The periodic
table is useful since catalytic behavior, like other chemical properties,