Praseodymium oxide chloride

Praseodymium oxide (Pr O ) was obtained from Aldrich and used without further purification. Praseodymium chloride (PrCl3) was prepared from praseodymium chloride hexahydrate (Aldrich 99.9%) by heating at ca. 150 C in air. 

The adsorption of carbon dioxide or oxygen on praseodymium samples was measured by a constant-volume method using a calibrated Pirani vacuum gauge. Praseodymium oxide was heated in oxygen (4 kPa) at 775°C for 1 h, then evacuated at 750°C for 0.5 h just before the measurement. The sample of praseodymium oxychloride was prepared from praseodymium chloride by heating under oxygen flow... 

Methane Conversion. The results for the conversion of methane on praseodymium oxide are shown in Figure 1 and Table I. The major products were carbon monoxide, carbon dioxide, ethylene, and ethane both in the presence and absence of TCM in the feedstream while small amounts of formaldehyde and C3 compounds were detected. Water and hydrogen were also produced. The catalyst produced low methane conversion (ca. 6%) and selectivity to C2+ compounds (ca. 30%) in the absence of TCM in the feedstream. On addition of TCM the conversion of methane after 0.5 h on-stream was increased by almost two-fold (11.9%) and increased still further to 17.2% after 6 h on-stream. The selectivity to C2+ also increased with time on-stream to 43.3% after 6 h on-stream. It is noteworthy that over the 6 h on-stream with TCM present the ratio increased from 1.0 to 2.1. No methyl chloride was... 

Adsorption of carbon dioxide or oxygen on the praseodymium samples was carried out in the pressure range of 1-40 Pa to evaluate the number of chemisorption sites on the samples. Praseodymium oxide irreversibly adsorbed 9.5 x 10" mol g of carbon dioxide. The amount of oxygen irreversibly adsorbed on the sample was 15.2 x 10" mol g Carbon dioxide or oxygen was not adsorbed on the samples containing chlorine, i.e., praseodymium chloride and praseodymium oxychloride prepared from the chloride by heating under oxygen flow at 750°C for 1 h. 

In the case of the praseodymium oxychloride produced from praseodymium oxide by the reaction in the presence of TCM (white-green portion), an O Is peak at 529.3 eV with a shoulder at 531 eV was observed. The peak shifted to 528.9 eV after xenon ion-sputtering for 0.5 min. The peak of Pr 3d was similar to that for praseodymium chloride, that is, the main peak was observed at 932.9 eV with a shoulder at 928 eV which was more clearly defined than that in the spectrum for praseodymium chloride. The peak shifted to 932.5 eV after the sputtering and the shoulder at 928 eV intensified as seen in the spectra for praseodymium chloride. The peak of Cl 2p was present at 198.8 eV and the position of the peak did not change after the sputtering. 

There were two peaks at 528.9 and 531.1 eV in the spectrum for O Is of the praseodymium oxychloride taken from the inlet portion of the reactor after the reaction in the absence of TCM (the sample originated from praseodymium chloride heated at 750°C for 1 h). The peak at 531.1 eV disappeared after xenon-ion sputtering while the main peak was present at 529.1 eV. The spectra for Pr 3d before and after xenon-ion sputtering were similar to those for praseodymium oxychloride which originated from praseodymium oxide. Although the Cl 2p spectra for the... 

No adsorption of carbon dioxide or oxygen was observed on either praseodymium chloride or oxychloride. This finding is consistent with the XPS results. The main peaks at 529 eV in the spectra for praseodymium oxychloride samples are also attributed to the lattice oxygen of the oxychloride while the peaks at 531 eV are assignable to O Is for praseodymium oxide, suggesting that the surfaces of the oxychloride samples are partially oxidized to praseodymium oxide. The 3d binding energy of 933 eV for praseodymium in the chloride and oxychloride implies that the valence of praseodymium is 3+, while the shoulder at 928 eV could be attributed to metallic praseodymium (77). 

Prkpagen 3445. See Ditallow dimonium chloride Prapagen WK. See Distearyidimonium chloride Praseodymium oxide CAS 11113-81-8... 

Figure 2 Conversion and C2+ selectivity for oxidative coupling of methane in the presence and absence of TCM over praseodymium chloride preheated in helium.

Praseodymium, separation of mixtures with lanthanum from monazite, as magnesium nitrate double salt, 2 56, 67 Praseodymium (III) nitrate, analysis of anhydrous, 5 41 Praseodymium (III) oxide, for synthesis of nitrate, 5 39w. Precipitates, apparatus for removing liquid from, 8 16 Purpureochromic chloride, 2 196 6 138... 

In 1885 C. A. von Welsbach isolated two elements as oxides, praseodymium (the word meaning green twin ) and neodymium (meaning new twin ), from a mixture of lanthanide oxides called didymia. The oxides can be transformed to fluorides by reaction with HF at 700°C (1,292°F), or with NH4HF2 at 300°C (572°F). The hydrated fluorides are then dehydrated in vacuo in a current of HF gas. The metals praseodymium and neodymium are obtained via metallothermic reduction with calcium at approximately 1,450°C (2,642°F), or via electrolytic reduction of the melts. The metals can also be obtained from anhydrous chlorides, obtained via reaction of the oxides with ammonium chloride at 350°C (662 °F), which are then reduced with lithium-magnesium at approximately 100°C (212°F). 

The synthesis of lanthanide and actinide compounds is the topic of a book edited by Meyer and Morss (1991). Topics that relate to halides, with the author(s) in brackets, include Lanthanide fluorides [B.G. Muller], Actinide fluorides [N.P. Freestone], Binary lanthanide(III) halides, RX3, X = Cl, Br, and I [G. Meyer], Complex lan-thanide(III) chlorides, bromides and iodides [G. Meyer], Conproportionation routes to reduced lanthanide halides [J.D. Corbett], and Action of alkali metals on lanthanide(III) halides an alternative to the conproportionation route to reduced lanthanide halides [G. Meyer and T. Schleid]. Meyer and Meyer (1992) reviewed lanthanide halides in which the valence of the lanthanide was considered unusual, with unusual being defined as compounds in which the localized valence of an atom differs from its oxidation number. A metallic halide such as Lalj [oxidation number (0)= -1-2 valence (V)= -l-3, since the 5d electron is delocalized in the conduction band] or a semiconducting halide such as PrjBtj (O = -t- 2.5 V = -I- 3) is unusual by this definition, but Tmlj (O = -1-2 V = +2) is not. In this review synthesis, properties, and calculated electronic structures are considered with emphasis on praseodymium halides and hydrogen intercalation into lanthanide dihalides and monohalides . 

An oxide of a rare earth element, it occurs in monazite and bastnasite. It is marketed as the oxide or as other salts, such as oxalate, carbonate or chloride salts. Technical grade products contain more or less amounts of praseodymium and some lanthanum and other rare earths. 

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