Abstract
An aqueous sol-gel method for the synthesis of γ-Al2O3 supports has been developed for the use in tar reforming applications. It was determined the influences of two different aluminum precursors (aluminum sec-butoxide (Al[OCH(CH3)CH2CH3]3) and aluminum nitrate (Al(NO3)3)) on the textural and crystallographic properties of Al2O3 supports. Only the formation of γ-Al2O3 is aimed in order to use these alumina materials as catalytic supports, because it presents high specific surface area and pore volume values. Additionally, the synthesis of γ-Al2O3 was realized with the use of a functionalized silicon precursor, [3-(2-aminoethylamino)propyl]trimethoxysilane, called EDAS. By the presence of an ethylenediamine group in this molecule, it is possible to chelate metallic ions and to highly increase their dispersion at a molecular level during the synthesis of metallic catalysts supported on alumina, which is an asset for catalytic applications. So it was developed a synthesis sol-gel procedure for the cogelation between the functionalized silicon alkoxide EDAS and alumina precursor. The alumina supports synthesized with Al(NO3)3 as precursor presented higher porous values than the ones obtained with aluminium sec-butoxide precursor. Since nitrate salts are much easier to handle than alkoxides, these observations allowed validating Al(NO3)3 as aluminum source for the future synthesis procedures for metallic catalysts supported on alumina.
Highlights
IntroductionA sol is a colloidal suspension of solid particles (1 - 1000 nm) in a liquid, in which the dispersed phase is present in a low amount, and a gel is obtained by the cross-linking of the sol colloid and results in a solid network with a high liquid amount in its pores
The samples synthesized with Al(NO3)3 present very similar pH-curves typical for aqueous alumina synthesis with a base and are characterized by three distinct fields [25]: 1) for volumes < 15 mL, i.e. pH < 4, the titration curves are almost horizontal, which indicates that the polymerization rate of the very small Al aggregates is fast and continuous
An easy experimental procedure for the synthesis of pure γ-Al2O3 supports is established by using aqueous sol-gel process
Summary
A sol is a colloidal suspension of solid particles (1 - 1000 nm) in a liquid, in which the dispersed phase is present in a low amount, and a gel is obtained by the cross-linking of the sol colloid and results in a solid network with a high liquid amount in its pores. In this way, a sol-gel process can be summarized as an inorganic polymerization realized in solution media [1]. They should be soluble in the reaction medium and reactive enough to participate in the gel forming process
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