Page 137 - Principles of Catalyst Development
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CATALYST  PREPARATION                                            125
                Each  step in  the  recipe  must  be translated  into  large-scale  operation.
           First,  each  must  be  technically  feasible,  that  is,  engineering  counterparts
           must  exist  for  laboratory  procedures.  Equipment  is  usually  no
           problem,  (35,160)  but maintaining the controlling conditions may be, Second,
           scale-up  must  be  economical.  The  most  important  factor  here  is  capital
           investment  to  acquire  facilities  for  what  may  be  large  quantities.  Purity
           levels of reagents is another issue which requires attention. Large quantities
           of very  pure feedstocks  may be expensive or even  unattainable.
                Equipment is  usually  available or adaptable for  most steps. Table 6.4
           list  common  unit  operations  found  in  catalyst  manufacturing.  Many  are
           material treating methods used by the solid or mineral processing industries.
           Relative  difficulties  in  scale-up  have  already  been  touched  upon;  for
           example, drying is  usually easier,  precipitation harder.


           6.7.2.  Continuous Unit  Operations
               As  in  all  chemical  processing,  continuous  operation  is  much  more
           satisfactory  for  large  throughputs.  Operating  costs  are  lless  and  product
           quality  control  better.  Whenever  possible,  the  catalyst  manufacturer
           attempts  to  modify  preparational  procedures to  accommodate  continuous
           operations.  This  is  fairly  straightforward  for  filtering,  drying,  calcination,

                      TABLE 6.4.  Unit Operations  in  Catalyst  Manufacwring

                     Preparation step         Unit equipment

                       Precipitation     Tanks,  batch and semi batch
                                         Mixing tanks
                                         Jets
                       Filtering         Leaf
                                         Rotary
                                         Centrifugal
                       Drying            Trays
                                         Forced air
                                         Moving belts
                                         Rotary  kilns
                                         Fluidized beds
                                         Spray driers
                       Calcination       Forced air furnace
                                         Rotary  kiln
                                         Fluidized beds
                       Formulation       Pelleting
                                         Extrusion
                                         Spheroidization
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