Synthesis Process and Structure of Al I Mg Modified Silica-gel Particle

摘要

The study on synthesis process andstructure of silica-gel particles modified Al I Mg hasbeen achieved. The modified silica gel has beenexpected for functional materials and catalysts. Anatomizer is used for particle production of silica gel.But, many hollow particles which were easily destroyedby handling were produced in the atomizer process. Thenumber of those weak particles decreased withincreasing the viscosity of silica-sol which could becontrolled by treated in relatively unstable statesuch as pH = 2 and 40degC , 50h. Small silica particlesin silica sol was thought to bind each other duringthe treatment and form apparently larger molecularweight silica-sol chain. In subsequently dryingprocess, Al and Mg nitrates which had been mixed withsilica sol changed partly to the oxides such asMgAl_2O_4 and MgO and partly to the elements whichconstructed the modified silica-gel. The chemical andphysical structure of the calcinated modified silicagel were stable in the region from 450degC to 700degCHalf of Al and quarter of Mg were in modified silicagel structure, where (Si-O)_n-Alcentre dot Mg~(2+),MgAl_2O_4, and MgO were observed by thermal analyses(TO; DTA) and NMR. The chemical structure as well asphysical structure was unstable at more than 700degC .Pore volume rapidly decreased and the coordinationnumber of Al fluctuated between fourto six from700degC to l,000degC. The synthesis process and thestructure of Al/Mg modified silica gel were partly clarified.