DETERMINATION OF THE POINT OF ZERO CHARGE, SURFACE-ACIDITY CONSTANTS, AND RELATIVE CONCENTRATION OF THE CHARGED SURFACE GROUPS OF GAMMA-ALUMINAS USED AS CARRIERS

被引:34
作者
VORDONIS, L [1 ]
KOUTSOUKOS, PG [1 ]
LYCOURGHIOTIS, A [1 ]
机构
[1] UNIV PATRAS,DEPT CHEM,CHEM ENGN & HIGH TEMP PROC RES INST,PATRAS,GREECE
关键词
CATALYSTS - Supported - METALS AND ALLOYS - Surfaces;
D O I
10.1021/la00069a003
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The point of zero charge (PZC), the surface acidity constants pK//1 and pK//2, and the concentration of the charged surface groups AlOH//2** plus and AlO** minus throughout the pH range 3. 0-11. 0 were determined by potentiometric acid-base titrations for a series of gamma -aluminas used in industry as carriers which contain various amounts of sodium and silicon. Moreover, these surface parameters were determined for a modified carrier prepared by deposition of sodium on the gamma -Al//2O//3 surface. It was found that the PZC, pK//1, pK//2, and the concentration of the positively charged groups (AlOH//2** plus ) at very low pH increased with sodium content whereas the concentration of the negative groups (AlO** minus ) decreased. The sodium effect was very pronounced when it was selectively concentrated on the surface of gamma -Al//2O//3 particles. The consequences of the above phenomena are discussed in relation to the use of gamma -aluminas for preparation of supported catalysts by deposition of active ion via adsorption of positive or negative species.
引用
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页码:281 / 283
页数:3
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