Page 115 - Principles of Catalyst Development
P. 115
CATALYST PREPARATION 103
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25 50 75 100
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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w 600
II:
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w
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300
25 50 75 100
WATER CONTENT. %
Figure 6.8. Temperature effects in drying.' "HI