Determination of palladium content in catalysts based on different carbon supports by inductively coupled plasma — atomic emission spectrometry (ICP-AES)

Abstract

Catalytic processes and technologies are the structure-forming elements of modern chemical, petrochemical and pharmaceutical industries. Prospects of their development are strongly determined by continuous improvement of the existing catalysts and developing the advanced and more efficient ones. Among the available catalysts, an important place belongs to palladium catalysts with carbon supports. Palladium as an active component exhibits unique catalytic properties in various transformations of organic substances: hydrogenation, dehydrogenation, isomerization, dehydrocyclization, carbonylation, oxidation, etc. To control the content of the active component of a catalyst, precise and rapid physicochemical methods are used. ICP-AES shows a good performance in the analytical practice due to the rapidity, sensitivity, high accuracy and selectivity in determining various elements. The aim of the study was to develop a scientifically grounded methodological approach to estimate the palladium content in the catalysts synthesized on different carbon supports made of carbon black and Sibunit, which combines only the acidic decomposition of a sample and analysis by ICP-AES. A series of palladium catalysts synthesized on the carbon supports with different structural and textural characteristics was studied. An urgent goal is to control the content of the active component in the composition of catalysts. This characteristic affects the phase and electronic state of the metal, the structural and textural characteristics and thus determines the activity and selectivity of catalysts during operation. Therefore, quantitative chemical analysis is one of the main methods used to control the quality of catalysts. A method for quantitative determination of palladium concentration, which combines acidic decomposition of a sample and ICP-AES has been developed. The carbon support type was shown to exert no effect on the accuracy and reproducibility of data obtained by the analysis of supported palladium catalysts. The content of palladium in such catalysts can be measured using analytical lines 340.458 and 360.955 nm without lowering the measurement accuracy. The selected conditions of sample preparation make it possible to carry out a quantitative analysis of metal systems based on the carbon support with high accuracy. The relative error in determining the elements did not exceed 4%, the relative standard deviation was no more than 0.04. The results of this work can be used to analyze catalysts of similar chemical composition by ICP-AES.