DTA analysis of the system CuCl2-KCl

Abstract

Mixtures of CuCI 2 and KC1 in molar ratios of Cu to K of from 0.5 to 1.0 were heated at 473 K in an air atmosphere, and then subjected to DTA analysis in the temperature range 293-773 K. A number of endothermic processes were observed, the extents of these depending on the molar ratio of Cu to K in the mixture.In the presence of potassium chloride, CuCI 2 forms complex compounds K2CuCI,, and KCuCI3 [1,2]. Phase diagrams of CuC12~uCI for specified contents of KC1 have been reported [3]. Similar data on the system CuCI2-KCI where copper(I) chloride is absent are not available. In the system CuC12-KC1, the transition of K2CuCI~ into KCuCI3 [4, 5] has been found to be possible within the temperature range 365-390 K.The present work involved thermogravimetric investigations of the system CuCI2-KCI in which the molar ratio of CuCI 2 to KCI was varied from 0.5 to 1.0 within the temperature range 293-773 K. Thermogravimetric investigations were supplemented by X-ray analysis. ExperimentalTo obtain the system CuCI2-KCI, dihydrous copper(II) chloride and potassium chloride (POCh Gliwice) were used. Weighed quantities of the two salts, in appropriate proportions, were dissolved in 100 cm 3 of distilled water and the solution was next evaporated to dryness at 343 K. The dry residue was crushed and ground. Powdered samples were roasted at 473 K for 2 h in an air atmosphere. After cooling down to room temperature, the samples were subjected to thermogravimetric and X-ray analyses.Mixtures with molar ratios of CuC12 to KC1 of 0.5, 0.614, 0.692, 0.768, 0.845, 0.922 and 1.0 were prepared as described above. Thermogravimetric analyses were made with a derivatograph (MOM, Budapest, Hungary) within the temperature John Wiley & Sons, Limited, Chichester Akad~miai Kiad6, Budapest

DTA analysis of the system carrier-CuCl2, KCl. part I

“…Too high a dilution of the active phase of the catalysts with the carrier did not permit recording of the probable mass loss from the active phase. In the DTA curves of the catalysts and the mixtures of CuC12 and KC1 [2], three well outlined endothermic effects are observed in the temperature range 473-773 K. The minimum of the first endothermic effect is at 498-518 K for the catalysts, and at 533-543 K for CuClz and KC1. As far as the catalysts are concerned, this may be attributed to the triple phase transition of K2CuCh-KC1-KCuC13 (498 K) or the double transition of K2CuCI3-KC1 (518 K) [1], whereas a triple transition of K2CuC14-KC1-KCuC13 (540 K) [1] can occur at 533-543 K. It may be presumed that, due to the presence of the carrier, the compound K2CuCh is formed inside the active phase of the catalyst, in which the copper is present as Cu(I).…”

“…The thermal curves of the carrier used for the preparation of the catalysts is presented in [17]. Figurd 1 shows the thermal curves of catalyst no.…”

“…The continuous mass loss observed in the TG curves is caused primarily by the loss of water from the carrier [17]. Too high a dilution of the active phase of the catalysts with the carrier did not permit recording of the probable mass loss from the active phase.…”

“…Optimal constant impregnation conditions were applied to all catalysts, which differed in total content of CuC12 and KC1 at a constant molar ratio CuC12:KC1 of 0.768, or which differed in the molar ratio CuClz:KCI at a fixed total salt content of 22.10%o The temperature of impregnation was 378 K, and the dropping rate of the aqueous solution of the mixture of CuC12 and KCI was 2.75 cm3/min, the volume of the dropped solution being 200 em 3 per 100 cm 3 of the carrier. Full characteristics of the carrier are given in [17]. The set of catalysts after impregnation are given in Table 1.…”

“…Neither is the structure of these mixtures known in phase areas through which they have to pass until the reaction temperature is reached [1,2]. Investigation of the structure of the active phase of the ethene oxychlorination catalyst of the type carrier-CuCl2, KC1 is complicated, due to the presence of the carrier.…”