III International Conference

PP-I-39increases with increase of the amount of NH 2 -groups. The strength (PA value) of (A) sitesattains to the level of 861 kJ/mol like that of initial amine used for modification of silica.pH titration method (strong acid (HCl) as probe molecule) allowed to determine theamount and strength (K H + protonate constant) of base sites on the surface of amino-containingsilica. Two type base sites were determined on the surface of samples (I) –(III) by thismethod. It was demonstrated that the amount and strength of the base sites increases with theincrease the amount of NH 2 -groups. K H + value depends on both the amount of NH 2 -groupsand the interaction’ nature of neighbor groups with NH 2 -groups of (I) – (III) and changes asfollows:4.0⋅10 6 (I) < 7.9⋅10 7 (II) < 2.7⋅10 9 (III).Reference1. M.Folman, D.J.C.Yates, Trans.Faraday Soc., 57(1961)20002. U.V.Holin, V.N.Zaicev, S.A.Mernii, N.D.Donskaja, L.N.Chistiakova, Ukr.Chem.Jorn. 59(9)(1993) 910.3. E.A.Paukshtis, N.S.Kotsarenko, L.G.Karakchiev, React.Kinet.Catal.Lett. 12(3) (1979) 315.79