Solid zirconium sulphates

Smith et al. [62SMI/M1L] used a Bunsen ice calorimeter to measure the high temperature heat content of Zr(S04)2(cr) from 273.15 to 1050 K. They found that the heat content could be described by the equation  

Differentiation of this equation yields an expression for the heat capacity of Zr(S04)2(cr) over the same temperature range  

The selected heat capacity at 298.15 K that has been determined from this 

Solubility studies at different temperature of hydrated solid zirconium sulphates show the solids to be extremely soluble in water [07HAU], [41FAL] and 

Frolova et al. [84FRO/MEL] used a vacuum adiabatic calorimetry technique to measure the low temperature (5.7 to 313.6 K) specific heat of Zr(S04)2 4H20(cr). They 

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Figure A-8 Solubility data of solid zirconium sulphates with differing concentrations of added sulphuric acid.

Falinski studied the solubility of hydrated zirconium sulphates and nitrates with differing concentrations of added sulphuric or nitric acid (see Figure A-2 and Figure A-3 respectively). Solid phases were analysed and show change in the solid phase composition with the concentration of added acid. Experiments were carried out at 25°C and 40°C. 

Experimental equilibrium data for the zirconium(IV)-sulphate system. 187 Selected thermochemical properties of solid zirconium telluride... 

Although the super acidity of sulphated zirconium oxide is widely accepted, Farca iu indicated that traditional acidity measurements, i.e. Hammett type, can not be applied to solid acids. He showed that the exceptional catalytic activity of sulphated zirconia and other sulphated metal oxides (SMO) is not justified by their acid strength and that they are in fact not superacidic at all. He argues that sulphated zirconium exhibits a bifunctional character in which oxidation in the initiation step is combined with acid catalysed reaction of the intermediates formed. Oxidation is normally achieved through the reduction of the sulphate or added redox promotors, which increases the catalytic activity but not the acid strength. 

Hygroscopic solid inorganic proton conductors as membrane fillers increase the number of protonic carriers and thus improve the hydrophilic character of the membranes. Among the inorganic solid proton conductors, °° ° ° zirconium phosphates, heteropolyacids, metal hydrogen sulphate and a few others are of special interest for their potential role in developing high temperature composite membranes for PEMFCs. 

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