Surface area of alumina

Nienow (1983a) observed a delay in the start of particle growth when binder was added to a bed of porous particles and stable fluidization under conditions which produced quenching with non-porous particles. Nitrogen adsorption measurements showed that the pore surface area of alumina decreased as spraying proceeded, indicafing that an effective reduction in pore volume was taking place. 

Typical procedure used was to take 1.0 g of alumina (as an example) powder and add 10 mL of solution of detergent with varying concentration. The mixture was shaken, and the concentration of detergent was estimated by a suitable method. It was found that equilibrium was obtained after 2-4 h. The detergent such as dodecylammonium chloride was found to adsorb 0.433 mM/g of alumina with a surface area of 55 m2/g. The surface area of alumina, as determined from stearic acid adsorption (and using the area/molecule of 21 A2 from monolayer), gave this value of 55 m2/g. These data can be analyzed in more detail ... 

It appears that this method may lead to high-surface-area gels. It was reported that the surface areas of alumina made via this route after calcination at 923 K were 370-400 mVg and those of silica were up to 850 mVg [71]. A disadvantage of this route is that chloride is formed during the process, which is environmentally unfnendly. 

The Chromia was loaded at different levels on Alumina. The Surface Area of alumina reduces as the chromia content increases. The results are given in Table No.3. 

K. In commercial operation, during the catalyst regeneration the specific surface area of alumina has an irreversible decrease. This produces a decrease in the acid function because, as quoted before,... 

Indirect determination of the specific surface area of alumina... 

Therefore, two different chemical methods allow to calculate selectively the surface area of alumina-supported cerium species. 

Figure 2 The surface area of aluminas calcined at lOOCPC for 2h. The samples contained aluminium sulphate produced from gibbsite. The abscissae shows the fractional conversion of the gibbsite.

Table 1 Surface Areas of Alumina Samples before and after Thermal Treatment...

Seidi and Kriska and Drozhalina and Bulgakova also observed that the adsorption of phenol from aqueous solutions was reversible and could be used to determine the surface area of activated carbons. Brand and coworkers used the adsorption of phenol as a measure of surface area of alumina, but the adsorption in this case was determined from solutions of phenol in heptane. Jankowska et al. °Gruszek et al. Koltesev et al. and Badnar and Nagi found that the adsorption of phenol from aqueous solutions was determined by the pore-size distribution of the activated carbon. The carbons with finer micropores had a better adsorption capacity, which could be as much as 34% by weight at an initial phenol concentration of 1 g/L. 

The Ni fraction removed from solution after 1.5 h impregnation at pH 7.2 is shown in Figure 2 as a function of the specific surface area of alumina. The initial Ni(II) concentration was 5. 10 M and the impregnations were performed at 298K. As expected, the yield of Ni(ll) deposition is hi er when the specific surfoce area of alumina is enhanced. 

Fig. 2 shows the BET surface areas of alumina, calcined at various temperatures and washcoated aluminas derived from SOL-IA. It appears that the Sbbt values of washcoated aluminas are not substantially different from those of sol-derived bulk alumina. 

Figure 2. The BET surface area of alumina derived from SOL-IA as a function of calcination temperature. alumina. washcoated aluminas.

P. H. Emmett and E. Teller - hence the usual name b.e.t. method (/. Amer. Chem. Soc., 60, 309,1938). ASTM C1069 measures the specific surface area of alumina or quartz by nitrogen adsorption. 

The detergent molecule, such as dodecyl ammoniumchloride, was found to adsorb 0.433 mM per gram of alumina with a surface area of 55 mVg. The surface area of alumina as determined from stearic acid adsorption (and nsing the aiea/molecule of 21 A from monolayer) gave the value of 55 mVg. 

Besides crystal structure change, heating temperature for gibbsite dehydration also affects the specific surface area of alumina. The BET surface area of alumina samples was tested with a ASAP 2020 V3.01 H analyzer. The BET surface area of alumina is proportional to LOI, as shown in Figure 1.8.5. The specific surface area of alumina works on the dissolution process by affecting the contact area between the alumina particle and molten cryolite. 

Surface areas of aluminas obtained by calcination of alumina hydrates at 550— 1100 K are usually 100— 300 m g The surface area of 7- and r -alumina is and that of ct-alumina a few m g ... 

Fig. 3. Effect of hydrothermal treatment time and temperature on surface area of alumina extrudates.

---