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Direct and simultaneous determination of metal impurities in catalysts based on platinum group elements

100%

Abusenaina A., Vojteková V., Flórián K., Poperníková Z., Mičková V., Hámborská M., Ružičková S.

issue 6

678-686

Production of new catalysts requires effective analytical quality control. The study of trace element composition of heterogeneous catalysts, based on C+PdO, using atomic emission spectrometry (AES) was carried out. A new method for the direct solid-state analysis by means of AES with direct current arc discharge was developed. On the basis of the qualitative analysis of elements, Al, Fe, Ni, Si and Ti have been identified, and for these elements, the quantitative method of determination has been developed. Optimization of excitation parameters and validation of the analytical method are presented. Calibration samples of the following composition were prepared: graphite powder (as a matrix), 3% of PdO and increasing contents of determined element oxides (spectrally pure). Calibrations were calculated by means of the least squares method. Working range for element impurities was from 1% to 0.0003%, and the limits of quantification - LOQ, (10-σ criterion) varied in the range from 0.002% (Ti) to 0.0038% (Si). For the control of active component, palladium was calibrated (working range - 0.01%–10.00%; LOQ −0.027%). The developed method can be used, also, for the elemental determinations of the other carbon based catalysts with the different active components (of platinum group elements).

Effect of silver on the catalytic hydrodechlorination of tetrachloromethane over silica-supported palladium-silver catalysts

75%

Bonarowska M., Kaszkur Z., Karpiński Z.

Recyclable Catalysis

2015

vol. 2

issue 1

Two silica-supported palladium based catalysts characterized by overall metal loadings 10 wt.%, and atomic Pd : Ag ratios of 100 : 0 and 70 : 30, were prepared by incipient wetness impregnation, subjected to reduction in hydrogen and characterized by XRD. It was found that incipient wetness co-impregnation of silica resulted in the formation of a catalyst characterized by relatively small metal crystallites (~11 nm) and significant extent of Pd-Ag alloying. The catalytic performance was investigated in the hydrodechlorination of tetrachloromethane in the gas phase. Silver addition to palladium in the co-impregnated catalysts had very pronounced effect, vastly decreasing the overall activity (conversion) and also the selectivity towards hydrocarbons, propensity characteristic for the monometallic palladium catalysts working in CCl4 hydrodechlorination carried out in the gas phase. Instead, large amounts of C2HxCly dimeric products were formed. These dimers are considered as possible coke precursors. Post-reaction samples of both catalysts contained large amount of carbon which entered the Pd and Pd-Ag phases. This carbon can be easily removed by treatment with hydrogen at 450ºC.

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1 Karpiński Z.

1 Kaszkur Z.

1 Mičková V.

1 Poperníková Z.

1 Ružičková S.

1 Vojteková V.

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Direct and simultaneous determination of metal impurities in catalysts based on platinum group elements

Effect of silver on the catalytic hydrodechlorination of tetrachloromethane over silica-supported palladium-silver catalysts