Abstract
Quantification of metal loading in supported catalysts is imperative; however, the analytical methods are usually time-consuming, expensive, and require sophisticated equipment and sample extraction with hazardous and corrosive strong acids. Herein, we report a new method for quantification of metal in supported catalysts using slurry sampling flame atomic absorption spectrometry. The slurry sampling method was used for determination of gold and the results were similar to those obtained with the traditional extraction method using aqua regia; however, it overcomes the main drawbacks associated with sample digestion by avoiding the use of concentrated toxic reagents, minimizing sample manipulation, and consequently, reducing the risks of contamination and the sample preparation time. Ultrasound radiation optimization associated with the solvent, mass of sample, concentration, and matrix effect in the slurry analysis allowed direct analysis by using the calibration in aqueous medium. The slurry sampling procedure could be applied to other catalysts with different supports and in bimetallic systems.
Highlights
Among many different transition metals used as catalysts, gold was conventionally considered inert until the pioneer work accomplished by Haruta et al.[1,2] Since many studies have been devoted to gold catalysis in a wide variety of reactions under comparatively mild conditions, including oxidation, hydrogenation, and many others
The stability of the suspension is one of the difficulties associated with this method. Other parameters, such as particle size, solvent, and calibration influence the quality of the analytical results. Taking these parameters into consideration, this paper describes the development of a method for direct determination of gold in catalysts by slurry sampling flame atomic absorption spectrometry (SLS-F Atomic absorption spectrometry (AAS))
Slurry sampling (SLS) analysis has been proposed as a way to overcome problems associated with sample decomposition.[21]
Summary
Among many different transition metals used as catalysts, gold was conventionally considered inert until the pioneer work accomplished by Haruta et al.[1,2] Since many studies have been devoted to gold catalysis in a wide variety of reactions under comparatively mild conditions, including oxidation, hydrogenation, and many others. Other parameters, such as particle size, solvent, and calibration influence the quality of the analytical results Taking these parameters into consideration, this paper describes the development of a method for direct determination of gold in catalysts by slurry sampling flame atomic absorption spectrometry (SLS-F AAS). The gold-supported catalysts were prepared using a modification of the sol-immobilization method described elsewhere.[19] In this procedure, 1.80 mL of an aqueous solution of 2.0 wt.% polyvinyl alcohol (PVA, 36 mg) was added under intense magnetic stirring to an aqueous. The system was stirred for 30 additional minutes, after which 1.5 g of the oxide support (TiO2 or CeO2) was added to the sol and stirred for three hours at room temperature After this time, the solid was separated by centrifugation (10 min at 7000 rpm) and dried at 100 oC for 20 h. Before analysis by F AAS, the solution was centrifuged for 10 min at 7000 rpm
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