Activation energy of thermal decomposition of SmC2O4Cl to SmOCl, CO and CO2

Abstract

An activation energy of Ea = 213.73 kJ tool d has been determined for the thermal decomposition of SmC204C1 to SmOCI, CO and CO2. The result is predictable on the basis of the Kahwa-Mulokozi expression + for the activation energy and its extended interpretation.The basis for our mechanistic interpretation of the thermal decomposition kinetics of oxalate is the Kahwa-Mulokozi expression for the activation energy

Influence of sample particle size and heating rate on the thermal decomposition of K2C2O4

“…These calculations confirm our mechanism for the thermal decomposition of the oxalate, which, by means of (ii), links the activation energy to the interaction between the metal and oxalate ions [2,3,7].…”

“…Our mechanistic interpretation of the thermal decomposition of the oxalate is based on the expression [2,3,7] Ea = 127 + 1.4853.10-6(I~" -9800) 2 where the ionization potential term IT = ~(Y-d) V2 is defined by Pauling's covalent radius re, the ionic radius ri in hexacoordination and ~/, the sum of the ionization potentials of the metal atom. On the basis of (ii), theactivation energy of (1) is theoretically predictable.…”

“…The C-O and M-O stretching frequencies are observed in the infrared spectrum at 1320 and 494 cm -1, respectively, for neodymium oxalate [7], giving Putting this value in (iii) and the value of E~,=2Ev(C-O)= = 31.33 kJ tool -1 from the stretching frequency of C-O at 1310 cm -1, we obtain ER = 299.9 kJ tool -1, in good agreement with the previously derived value. The value is also in excellent agreement with Pauling's estimate of the resonance energy V2ER = 150.6 kJ tool -1 for a single carboxylate ion [10].…”

“…We previously proposed a mechanism for oxalate thermal decomposition, in which breaking of the C-O bond is considered to be the rate-determining step [3,7]. Since the multiplicity of the C-O bond decreases with increasing interaction between the metal and oxalate ions, the activation energy will decrease with increasing interaction, to a minimum at 1~" = 9800.…”

“…For Nd2(C204)3, the activation energy is Ea = 127 kJ tool -1 (I~" ~ 9800) [3,7], and hence (I) was proposed as mechanism:…”