R.V. Jasra andS.G.T. Bhat

Key Words Adsorption, surface area, alumina, inhibitor, pore size distribution, basicity. 

Modifeation of alumina surfaee to enhance selective adsorption of particular compounds is an area of rapid development. The activated alumina surface contains a range of surface sites differing in their chemical structure and reactivity. Modification of the surface to contain a greater proportions of surface fuctionalities that enhance the desired separtion or reaction which reducing undesired sites, is a powerful tool in the design of selective adsorption process. In the present study the modification of alumina surface is effected by treatment with acid and base to enhance the adsorption of an antioxidant (tert-butyl catechol) from aromatic hydrocarbon (styrene). 

Chemical Modification of Alumina The commercial grade alumina (AD-101) produced by Indian Petrochemicals Corporation Limited, CATAD Division, Bombay is used as the starting alumina in the present study. This alumina is treated with mild alkali(NaOH) and with mild acid (HCl). About 25 gms of AD-101 is exactlty weighed and taken in a round bottomed flask and to it requisite concentration of NaOH/HCl is added and heated at required temperature for 4-15 hrs. After treatment it is thoroughly washed with double distilled water to remove excess of acid / alkali by monitoring the pH of the extract. A commercial alumina adsorbent available in the market which is specifically used for removal of tert-butyl catechol from styrene is used as a reference. The commercial sample was in the form of a finely divided powder ( 120 mesh size) with a water adsorption capacity of 13% at 60% RH. 

Styrene,purity 99% (Fluka) stabilized with 0.005% of tert-butyl catechol was purified by treating with IN Sodium hydroxide repeatedly and washed with distilled water.Styrene is dried for several hours with MgS04 and finally distilled under reduced pressure(2). Phenolphthalein (CDH India) Bromothymol blue (CDH India), p-Nitroaniline (CDH India), 2,4-Dinitroaniline (CDH India) and 4-Chloro 2-nitroaniline ( Lancaster UK), p-tert-Butyl catechol (National Chemicals India) were used without further purification. 

Physico-chemical Characterization Surface area, pore volume and pore size distribution of alumina samples were determined by adsorption- desorption isotherm of nitrogen at 77K using Sorptomatic 1900 (Carlo Erba Instruments, Italy). The sample was degassed at 200°C for 2-3 hr. under vacuum ( lO mm Hg) prior to N2 adsorption. Surface area was calculated using B.E.T. isotherm. Pore size distribution was determined from nitrogen desorption data at p/p° = 0.03 and above, using the method of Barret, Joyner and Halenda (3). 

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