Thermal decomposition of potassium persulfate in aqueous solution at 50°C in an inert atmosphere of nitrogen in the presence of acrylonitrile monomer

摘要

AbstractThe rate of thermal decomposition of persulfate in aqueous solution in the presence of acrylonitrile (AN) monomer (M) and of nitrogen, may be written as:documentclass{article}pagestyle{empty}begin{document}$$ {{ - dleft( {{rm S}_2 {rm O}_8^{2 - } } right)} mathord{left/ {vphantom {{ - dleft( {{rm S}_2 {rm O}_8^{2 - } } right)} {dt{rm }alpha }}} right. kern-nulldelimiterspace} {dt{rm }alpha }}left( {{rm S}_2 {rm O}_8^{2 - } } right)^{1.35 pm 0.05} times left( M right)^{1.26 pm 0.069} $$end{document}in the concentration range of persulfate (1.8 to 18.0) ×10‐3, and of monomer (M), 0.30 to 1.20, mol dm‐3.It was observed that the pH of the solution containing persulfate and monomer did not alter during polymerization if the monomer concentrations were close to its solubility under the experimental conditions. Conductance of the aqueous solutions of persulfate and monomer was found to decrease during the reactions. In an unbuffered aqueous solution containing only persulfate, however, the pH was found to decrease continuously at 50°C with time, while the conductance of the solution was found to increase. The monomer (AN) had no effect on the glass electrodes of the pH meter in aqueous solutions, and also on the electrodes of the conductivity cell. It has been suggested that the secondary or induced decompositions of persulfate were due to the following elementary reactions:documentclass{article}pagestyle{empty}begin{document}$$ begin{array}{*{20}c} {left( {rm X} right)} hfill {rm } {rm S}_2 {rm O}_8^{2 - } + M to cdot M hbox{---} {rm O} hbox{---} {rm SO}_3^ - + {rm SO}_4^{ cdot ^ - }, hfill {left( {rm Y} right)} hfill {rm } {rm S}_2 {rm O}_8^{2 - } + M_j^ cdot to M_j hbox{---} {rm O} hbox{---} {rm SO}_3^ - + {rm SO}_4^{ cdot ^ - }, hfill end{array} $$end{document}where (Mj·radicals (j= 1 to 10) are water‐soluble oligomeric or polymeric free radicals.kxandkyat 50°C have been estimated as 1.70 X 10‐5and 5.08 × 103dm3mol‐1s‐1, respectively. By measuring pH of freshly prepared persulfate solutions at 25°C, it is suggested that 0.05–0.30 of persulfate reacts molecularly with water (i.e., hydrolysis), as soon as it (10‐3to 10‐2mol dm‐3) is added to distilled water (pH 7.0). This hydrolysis was found to be stopped in dilute sulfur