Effect of modifying alumina desiccants with sulfuric acid on their physicochemical properties

Characteristics optimization of activated alumina desiccants based on product of a centrifugal thermal activation of gibbsite

“…Just this circumstance leads to an increase in the sorption capacity for water of the desiccants modifi ed with sulfate ions. In contrast to [7], the absence of a positive effect of LASs on the adsorption may be due to the fact that no BACs are formed when water is adsorbed on the LASs of the activated alumina under study. Therefore, the adsorption of water on the weaker LASs of this kind is presumably restricted only by the monolayer, i.e., the centers do not favor a polylayer adsorption.…”

“…Introduction of sodium or potassium hydroxide in the stage in which a moldable mass is formed from a bayerite-containing aluminum hydroxide produced by the CTA method (AM-1 series) results in that, compared with the acid modifi cation [6,7], the average pore diameter and mesopore volume become larger, with the micropore volume and specifi c surface area both decreasing. The observed texture changes do not favor an increase in the SC of the desiccants.…”

“…Measurements were made in an adsorber with diameter of 30 mm and height of 400 mm under the following conditions: (1) at low moisture content in the gas at the adsorber inlet: 0.86 g H 2 O/m 3 (dew point -18.7°C); rate of the vapor-air mixture, 3.4 L min -1 ; gas temperature 22°C; adsorbent charge 100 cm 3 ; (2) at high moisture content of the gas at the adsorber inlet: 15.6-16.6 g H 2 O/m 3 (dew point 18. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].5°C) fl ow rate of the vapor-air mixture, 4.1 L min -1 ; atmospheric pressure; gas temperature 22°C; adsorbent charge 120 cm 3 .…”

“…The modifi cation of the surface of desiccants with sulfate ions (via introduction of sulfuric acid solutions of various concentrations in the stage in which a plastic paste is prepared from pseudoboehmite-or bayeritecontaining hydroxides produced by the CTA method) makes it possible to raise the dynamic capacity of γ-Al 2 O 3 desiccants to the level of the η-Al 2 O 3 -based drying agent by both diminishing the average pore diameter and making higher the surface acidity [7]. 344 DANILEVICH et al…”

“…In addition, according to [3], the alkaline modifi cation may not only lead to an increase in the number of basic centers, but, in certain concentrations, also raise the number of acid centers. As shown in [7], a convenient way to modify desiccants is by introduction of additive in the stage in which moldable pastes are prepared.…”