Silica-alumina catalyst surface group density

However, unmodified Cr/alumina catalysts generally display only poor activity for ethylene polymerization. Alumina has only weakly acidic Al-OH groups, and it often exhibits a higher surface OH group population than silica. Both of these properties can potentially influence the electron density or ligand field of the chromium. 

To more precisely control the acid-base interaction of the silica-alumina-supported tertiary amine catalyst for organic synthesis, we examined the control of the density of surface Si-OH groups [15]. According to the above-mentioned immobilization mechanism, if the Si-OH density decreases, the acid-base interaction should be decease because of the far amine-immobilization positions from strong acid sites, resulting in lower acid-base interaction and higher catalytic performance. 

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