Sodium titanate material, characterization

A program to characterize the sodium titanate material has verified that the chemical and physical properties are reproducible from batch to batch for any of the preparation methods. 

To optimize the use of the amorphous sodium titanate powders as catalyst substrates, it is important to fully characterize the ion-exchange properties of the material. Further, the solution properties of the active metal to be loaded onto the support will be an important parameter in the control of the adsorption process. For example, exposure of sodium titanate to a nickel salt solution does not guarantee that nickel will be loaded onto the sodium titanate, or that the nickel, if loaded, will be dispersed on an atomic level. Sodium titanate only behaves as a cation exchange material under certain pH conditions. The solution pH also influences the hydrolysis and speciation of dissolved nickel ions (3), which can form large polymeric clusters or colloidal particles which are not adsorbed by the sodium titanate via a simple ion-exchange process. 

This paper describes some of our initial studies of the solution properties of sodium titanate powders in order to understand and control the metal-loading process in the preparation of a heterogeneous catalyst from the materials. The purposes of this study are 1) to define the pH and concentration regimes in which nickel is loaded onto sodium titanate as monomeric ions via ion exchange, as polymeric clusters via hydrolysis, or as discrete particles of colloidal nickel hydroxide, and 2) to characterize the catalysts with respect to the dispersion of the active metal under reaction conditions by measuring the activity and selectivity of the catalysts for a known "structure-sensitive" reaction, the hydrogenolysis of n-butane. 

Another synthesis route consists on a step requiring extreme conditions to solubilize Ti02-anatase in concentrated soda. The hydrothermal synthesis conditions allow to obtain a hydrogenated sodium titanate of formula Naj,H2 yTi 02 i-xH20. After an exchange of Na ions by protons and dehydration of the total material, Ti02-B is obtained in the form of nanotubes or nanowires. The difficulty of characterization of the product and the conditions required for the hydrothermal synthesis route can be a hindrance for the application. 

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