Page 63 - Principles of Catalyst Development
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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,
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