Variation of Topographical and Catalytic Properties of Constituent Particles of SO₄^2--Promoted Oxides in the Preparation Process

Abstract

SO₄^2- ions loaded on the surface of TiO₂ or ZrO₂ act as a promoter to enhance the Lewis acidity of the metal cations upto the strength of super solid acid. The SO₄^2- ions act simultaneously as a suppressor of the thermal growth of constituent oxide particles during calcination. The OH groups on the surface without SO₄^2- ions are active to the Olation reaction which is 2OH→-O-+H₂O, and leading to the coagulation and joining of the particles. The replacement of OH group with SO₄^2- ion results in a retarding effect against the decrease of surface area and crystallization along with phase transition. The catalytic activity of super solid acid catalysts such as SO₄^2-/TiO₂ and SO₄^2-/ZrO₂ was found to be controlled by both the number of super solid acid sites and the acid strength.