Complexing in Calcium Acetate and Propanoate Fluids at Elevated Temperatures and Pressures

Abstract

The presence of saturated aliphatic carboxylic acids in low to medium temperature hydrothermal environments has been well documented. Experimental studies have demonstrated that acetic acid exists metastably to temperatures well above 300~ before undergoing decarboxylation (Palmer and Drummond, 1986). Similar expectations exist for propanoic and butanoic acids. Significant concentrations of acetic and propanoic acids have been measured in oil-field brines (Shock, 1994). Of particular interest has been the association of organic material with ore deposits such as the Mississippi Valley type. This has stimulated investigation of stability relations of metalic-organic complexes at elevated temperatures and pressures as such complexes may serve as major agents for the dissolution, transport and precipitation of the metals. Spectroscopic investigations of sodium and calcium acetate and propanoate solutions have been undertaken in order to investigate their relative stabilities and complexing behaviour as a function of temperature and pressure. Using a special hydrothermal pressure vessel fitted with conical diamond windows, Raman spectra of the acetate and propanoate solutions were measured at