Thermal Decomposition of Triazine Herbicides II. 6-Chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine (atrazine) and its metabolites

Thermal degradation of atrazine and its metabolites has been investigated using a thermogravimetric technique(TG) with the application of three types of crucibles: opened, Knudsen type and labyrinthtype, and non-isothermal DSC method, using hermetically closed and opened alumina sample pans. The great influence of decomposition conditions (the crucible type) on thermal degradation was observed. TG analysis showed that the degradation process of atrazine took place in three stages. The increase of amino groups in triazine ring increases the amount of non-volatile thermal degradation products by association. The presence of chlorine substituent facilitates the forming of products with low volatility. Hydroxyatrazine decomposes only in one stage process. The dealkylation process observed in hermetical sample pans (DSC) was two-stage and in open sample pans one-stage process. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal behaviour of NH4ReO4 supported on inorganic gels

Results of TG and DTA studies as well as an analysis of the liberated gas products have led us to recognize differences in the mechanisms of transformations taking place in the systems NH₄ReO₄/Al₂O₃-SiO₂ (25 wt% SiO₂ and NH₄ReO₄/Al₂O₃ containing 1.1, 3.3 and 3.3, 9.9, 17.8 wt% NH₄ReO₄. Thermal decomposition of NH₄ReO₄ on the supports used begins with release of ammonia, which is strongly bound with the surface in the system of 3.3 wt% NH₄ReO₄/Al₂O₃, and undergoes oxidation to nitrogen oxides in the air atmosphere. In the other systems studied, the process of ammonia release starts already at 473 K and ammonia does not get oxidized. Moreover, it has been established that ammonia perrhenate supported on the surface of Al₂O₃-SiO₂ in the amount of 1.1 or 3.3 wt% undergoes partial thermal decomposition to ReO₂ which is further oxidized in the air atmosphere. As follows from the thermal studies as well as the measurements of activity in a reaction of 1-hexene metathesis, the active centres of the reaction of olefin metathesis are formed on the surface of the studied systems after their calcination at 473 K.     

Thermal decomposition of PTFE in the presence of silicon,calcium silicide,ferrosilicon and iron

Simultaneous TG/DTA has been used to study the thermal decomposition of binary compositions containing polytetrafluoroethene (PTFE) with silicon (Si), calcium silicide (CaSi₂), ferrosilicon (FeSi) or iron (Fe) powders. In nitrogen and under dynamic heating program the thermal decomposition of Si/PTFE and CaSi₂/PTFE is an exothermic process. The other two compositions decompose endothermically. In each case the decomposition reactions show first-order kinetics but only iron does not change considerably the kinetics of PTFE depolymerization. The constants of the decomposition rate at 850 K for silicon containing reducers are about four times higher than those of PTFE and Fe/PTFE. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decompositions of some transition metal polyacrylates

Polyacrylales of Fe, Cr, Ni, Co and Mn were synthesized by the reaction of poly(sodium)acrylatc with metal halides. The salts obtained were investigated by thermal analysis. During heating in argon or air, all the salts behaved in a similar way. The initial decomposition temperature of the investigated salts increased in the following sequence: Fe<Cr<Ni<Co<Mn. The solid residues of the decompositions of the salts were also analysed.

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Zusammenfassung Polyacrylate von Fe, Cr, Ni, Co und Mn wurden durch Reaktion von Natriumpolyacrylat mit den entsprechenden Metallhaliden synthetisiert. Die erhaltenen Salze wurden thermoanalytisch untersucht. Beim Aufheizen in Argon und Luft verhalten sich alle Salze ähnlich. Die Temperatur, bei der die Zersetzung einsetzt, steigt in folgender Reihenfolge an: Fe < Cr < Ni < Co < Mn. Die festen Rückstände der Zersetzung der Salze wurden ebenfalls analysiert.

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, , , . , , . Fe<Cr<Ni<Co<Mn. .