Page 115 - Principles of Catalyst Development
P. 115

CATALYST  PREPARATION                                            103
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                                      WA TER  CONTENT.  %
                      Figure 6.7.  Pore volume loss  on drying  of a  silica  hydrogel. (!5RI
           develop and the  structure collapses, with  loss  of pore volume  and surface
           area. High temperature gradients in the sample must be avoided. The effect
           of temperature is  shown  in  Fig.  6.8.  Lower temperatures give  less  surface
           loss,  since  evaporation  rates  are  lower. (159)  Vacuum  drying  at  lower tem-
           peratures  is  a  satisfactory  laboratory  procedure.  In  fact,  one  of the  best
           devices is  a  rotary, lamp-heated evaporator.
               Control of evaporation rates is much easier with large-scale equipment.
           Continuous operations such as belts, rotary kilns, fluidized, and spray driers

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                             25          50          75          100
                                       WATER  CONTENT.  %
                            Figure 6.8.  Temperature effects  in  drying.' "HI
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