Destruction of carbon tetrachloride in the presence of hydrogen-suppling compounds with ionisation and catalytic oxidation. Part 2: methane as hydrogen font

The performance of methane (CH4) as hydrogen donor molecule for the deep and clean oxidation of tetracloromethane (CCl4) has been experimented. The oxidation of CCl4-CH4 admixtures were performed by catalytic combustion with and without pre-catalytic actions (i.e. ionisation/ozonisation) over manganese oxide based catalyst. The extent of CCl4 and CH4 combustion was controlled by quantitative determinations of both CO2 and HCl formed and of CCl4 and CH4 converted. Experiments were performed in the 100-500°C reaction interval in a continuous reaction line at laboratory scale. Fixed CCl4 concentration (2000ppmv) with/without CH4 addition to air constituted the feed. Methane was added to the feedstream in variable concentration (1000-3000ppmv), the obtained organic mixtures had H/Cl atomic ratios (RH/Cl) from 0.5 to 1.5. Comparing the tests of ionisation/ozonisation (I/O) of pure CCl4 streams and CCl 4-CH4 admixtures, the efficiency of the hydrogen donor role of CH4 was evidenced. The residue CH4 concentration was not affected by the residence time (14-42s) in the ionisation reactor while the residue concentration of CCl4 decreased by increasing it. A first-order rate equation in CCl4 concentration was found to represent the ionisation process both in the absence and in the presence of hydrocarbon. On the manganese oxide catalyst, CCl4 catalytic combustion (CC) was not remarkably influenced by CH4 presence. CCl4 destruction by catalytic combustion assisted with ionisation (IOCC) gave rise to higher HCl yield in comparison with conventional combustion. The HCl formation increased with increasing the RH/Cl value both in the I/O and IOCC experiments, while the CO2 formation lightly decreased for high RH/Cl in the CC and IOCC experiments due to incomplete oxidation of CH4.