Włodzimierz Szczepaniak

Enthalpies of phase transition in the lanthanide chlorides LaCl3, CeCl3, PrCl3, NdCl3, GdCl3, DyCl3, ErCl3 and TmCl3

Abstract The enthalpies of phase transition in the lanthanide chlorides have been measured with a differential scanning calorimeter and also with a Calvet-type microcalorimeter to within an experimental error of ±2%. The molar enthalpies of fusion of LaCl 3 , CeCl 3 , PrCl 3 , NdCl 3 , GdCl 3 , DyCl 3 , ErCl 3 and TmCl 3 are 55.7, 55.5, 52.1, 48.1, 40.6, 22.8, 31.1 and 35.6 kJ mol −1 respectively. The existence of a solid-solid phase transition was found in DyCl 3 and ErCl 3 at 611 and 1025 K with a molar enthalpy of transition of 1.4 and 5.3 kJ mol −1 respectively. A significant difference (8.5 kJ mol −1 ) between the absolute values of molar enthalpies of crystallization and fusion was found for LaCl 3 at 1124±3 K; this unusual behaviour was explained by an “after-fusion” effect. The entropies of fusion are discussed in terms of structural types of the lanthanide chlorides.

Heat capacity of LaCl3, CeCl3, PrCl3, NdCl3, GdCl3, DyCl3

Abstract Heat capacities of LaCl3, CeCl3, PrCl3, NdCl3, GdCl3, DyCl3 have been measured by differential scanning calorimetry in the temperature range from 300 K to melting temperatures of the compounds. Heat capacities of liquid PrCl3, NdCl3, GdCl3, DyCl3 have also been registered. These results have been compared with literature data and fitted by a linear temperature dependence. The temperature coefficients have been given.

Calorimetric investigation of NdCl3MCl liquid mixtures (where M is Na, K, Rb, Cs)

Abstract The molar enthalpies of mixing ΔmixHm in the liquid NaClNdCl3, KClNdCl3, RbClNdCl3 and CsClNdCl3 binary systems have been measured over the whole composition range at 1124, 1065, 1122 and 1122 K, respectively, with an accuracy of about 6%. The apparatus used was a Calvet-type high-temperature microcalorimeter and mixing of the two liquid components was obtained by the break-off ampoule technique. In the investigated systems, the enthalpies of mixing are negative with minimum values at about −5.7, −16.6, −20.2 and −23.4 kJ mol−1, respectively, at χNdCl3 = 0.4. These values are almost identical, within the experimental accuracy, to those in other previously investigated MClLnCl3 mixtures. The molar enthalpies of formation ΔfHm(K3NdCl6, 1, 1065)/kJ mol−1, ΔfHm(Rb3NdCl6, 1, 1122)/kJ mol−1 and ΔfHm(Cs3NdCl6, 1, 1122)/kJ mol−1, according to the reaction 3 MCI(1) + LnCl3(1)= M3LnCl6(1), are equal to −55.2, −68.8 and −80.8 kJ mol−1, respectively. The least-squares coefficients A, B, C, D, E of the equation for the interaction parameter λ= A + Bχ + Cχ2 + Dχ3 + Eχ4χ4 (in kJ mol−1) are presented.

Entropies of phase transitions in the M3LnCl6 compounds (MK, Rb, Cs; LnLa, Ce, Pr, Nd) and K2LaCl5

Abstract The molar enthalpies of the solid-solid and solid-liquid phase transitions were determined by differential scanning calorimetry for the compounds K2LaCl5, Rb3LaCl6, Cs3LaCl6, K3CeCl6, Rb3CeCl6, Cs3CeCl6, K3PrCl6, Rb3PrCl6, Cs3PrCl6, K3NdCl6, Rb3NdCl6 and Cs3NdCl6. The K3LnCl6 (LnCe, Pr, Nd) and Rb3LaCl6 compounds, which do not exist at room temperature, are formed at high temperature with a considerable loss of enthalpy (48–55 kJ mol−1) compensated by a high gain in entropy (63–65 J mol−1 K−1). The Cs3LnCl6 (LnLa, Ce, Pr, Nd) compounds are stable at ambient temperature; they undergo a transition in the solid state with a corresponding enthalpy and entropy of 7.4–7.8 kJ mol−1 and 10.9–11.2 J mol−1 K−1. The calorimetric measurements show that Rb3CeCl6, Rb3PrCl6 and Rb3NdCl6 are also probably stable at room temperature. The enthalpies and entropies of fusion are reported for all the compounds mentioned above.

Formation enthalpies of the MBrLaBr3 liquid mixtures (M = Li, Na, K, Rb, Cs)

Abstract Molar enthalpies of mixing of the LiBrLaBr 3 , NaBrLaBr 3 , KBrLaBr 3 , RbBrLaBr 3 and CsBrLaBr 3 systems have been measured with a Calvet-type high-temperature microcalorimeter. The enthalpies decrease gradually from −0.67 kJ mol −1 for the lithium system through −4.32, −10.73 and −14.97 kJ mol −1 for the sodium, potassium, and rubidium systems to −16.81 kJ mol −1 for that of cesium at the composition of the 3 MBr·LaBr 3 compound. The results have been discussed in terms of the conformal solution theory of Davis as well as in terms of relative ionic potentials.

Calorimetric investigation of PrCl3NaCl and PrCl3KCl liquid mixtures

Abstract The present work is part of the thermodynamic research performed on the LnCl 3 MCl systems (where Ln is lanthanide and M is alkali metal). The molar enthalpies of mixing Δ mix H m in the NaClPrCl 3 and KClPrCl 3 liquid binary systems were measured at 1122 K over the whole composition range under argon at atmospheric pressure, with an accuracy of about 6%. The apparatus used was a Calvet-type high-temperature microcalorimeter and mixing of the two liquid components was obtained by the break-off ampoule technique. In the systems, the enthalpies of mixing values are negative, with a minimum value of about −7 and −16 kJ mol −1 for NaClPrCl 3 and KClPrCl 3 , respectively, at χ PrCl 3 ≈Fl 0.4. These values are very similar to those relative to the systems MClLnCl 3 previously investigated. The molar enthalpies of formation Δ f H m (K 3 PrCl 6 , 1, 1122 K)/kJ mol −1 , Δ f H m (Rb 3 PrCl 6 , 1, 1122 K)/kJ mol −1 and Δ f H m (Cs 3 PrCl 6 , 1, 1122 K)/kJ mol −1 , according to the reaction 3MCl(1) + PrCl 3 (1) = M 3 PrCl 6 (1), are equal to −55.9, −66.4, and −80.4 kJ mol −1 respectively, and are almost identical (in the limits of experimental uncertainty) to those of the compounds M 3 LnCl 6 (where M is K, Rb, Cs, and Ln is La, Ce, Nd) previously investigated. The least-squares coefficients A, B, C, D and E of the equation for the interaction parameter λ = A + B χ + C χ 2 + D χ 3 + E χ 4 (in kJ mol −1 are presented.

Recovery of copper from PVC multiwire cable waste by steam gasification

Screened multiwire, PVC insulated tinned copper cable was gasified with steam at high temperature (HTSG) under atmospheric pressure for recovery of cooper. Gases from the process were additionally equilibrated at 850°C on the bed of calcined clay granules and more than 98% of C+H content in the cable was transformed to non-condensing species. Granules prepared from local clay were generally resistant for chlorination, there was also almost no deposition of metals, Cu and Sn, on the catalytic bed. It was found that 28% of chlorine reacted to form CaCl2, 71% was retained in aqueous condensate and only 0.6% was absorbed in alkaline scrubber. More than 99% of calcium existed in the process solid residue as a mixture of calcium chloride and calcium oxide/hydroxide. PVC and other hydrocarbon constituents were completely removed from the cable sample. Copper was preserved in original form and volatilization of copper species appeared insignificant. Tin was alloying with copper and its volatilization was less than 1%. Fractionation and speciation of metals, chlorine and calcium were discussed on the basis of equilibrium model calculated with HSC Chemistry software. High temperature steam gasification prevents direct use of the air and steam/water is in the process simultaneously gaseous carrier and reagent, which may be recycled together with hydrocarbon condensates.

Enthalpies of mixing in PrCl3CaCl2 and NdCl3CaCl2 liquid systems

Abstract The molar enthalpies of mixing Δ mix H m in the PrCl 3 CaCl 2 and NdCl 3 CaCl 2 liquid binary systems were measured at 1073 K over the whole composition range under argon at atmospheric pressure. The apparatus used was a Calvet-type high-temperature micro-calorimeter and mixing of the two liquid components was obtained by the break-off ampoule technique. In both systems the plots of enthalpies of mixing versus composition were “S-shaped” curves. The enthalpy of mixing values are positive for NdCl 3 - and PrCl 3 -rich compositions, and negative for other compositions. These values are very small (from about −200 to about 180 J mol −1 ). In the PrCl 3 CaCl 2 and NdCl 3 CaCl 2 liquid binary systems,Δ mix H m ≈0 at χ PrCl 3 ≈ 0.6 and at χ NdCl 3 ≈ 0.4, respectively. These results are discussed in terms of equilibrium between the LnCl 3 (where Ln is Pr, Nd) polymers and anionic complexes as a function of the composition of the melts.

Internal cation mobility in molten NaClNdCl3

The paper presents results of internal mobility investigations of Na+ and Nd3+ cations in molten binary system NaClNdCl3 at 1023, 1073 and 1123 K. Results of investigations have been compared with literature data for KClNdCl3 system. It has been found that internal mobility of Na+ ions increases with temperature and is higher than mobility of its K+ analogues. It has also been found that for NaClNdCl3 system internal mobility of Nd3+ does not depend on the melt composition in the range of NdCl3 equivalent fractions 0.50 < yNd <-1, whereas for KClNdCl3 system this independence begins at NdCl3 equivalent fraction of 0.80. Moreover, internal mobility of Nd3+ seems almost independent of temperature.

Steam gasification of oat with conversion of tars on clay catalyst and gas cleaning by condensation of steam

Abstract Gasification of oat grains with steam at normal pressure has been performed in a laboratory scale. Experiments were carried out in a vertical quartz reactor, with a steady flow of the steam and immediate tars conversion at 900ºC on the catalytic bed prepared from local clay with simple additives. Condensation of steam excess enabled essential elimination of non-volatile components of the gas stream. Condensates were analyzed with GC-MS. The highest level of organic compounds was detected in experiment with non-catalytic bed of small quartz pieces (90.2 mg/15 g of oat grains) and successful decreased by 86% for original clay without additives (precursors), 94% for clay with magnesium precursor, 97% with iron and more than 99% with calcium one.