THERMAL ANALYS IS OF PYR ID INE-TREATED SEP IOL ITE AND PALYGORSKITE

A B S T R A C T: The thermal behaviour of sepiolite and palygorskite treated with pyridine (Py) was investigated byDTA, TG, DTG and EGA (by MS) under a flow of air and inert gases (N 2 or Ar). The thermal analysis showed that the organic base was adsorbed by the clays, penetrating into the clay pores and replacing zeolitic and bound water. Its presence in the pores shifted the dehydroxylation peak to temperatures higher than the corresponding peak in the untreated clays. Under N2 and Ar, thermal desorption ofPy from sepiolite was observed at 260 and 650 ~ whereas for palygorskite only traces of Py were detected in the evolved gases. In addition to desorption, reactions of pyrolysis and condensation to coke were detected by the evolution of ammonia, methane and hydrogen, respectively. In air, oxidation of the organic matter led to the appearance of exothermic peaks. The profile of the DTA curve and the temperatures of the most intense exothermic peaks were determined by the rate of the carbon oxidation. In a previous publication (Shuali etal., 1990) we described the thermal behaviour, under air or N2 flow, of the porous clays sepiolite and palygorskite treated with n-butylamine (BA). Under N 2 flow, in addition to thermal desorption of the aliphatic base, reactions of pyrolysis and condensation to coke were detected. In air, oxidation of the sorbed organic matter le