Change in the pore structure of active carbons in precipitation of carbon from methane

Abstract

1. The rates of precipitation of carbon in pyrolysis of methane in active carbons are maximum initially and decrease in time. The dependences of the initial rates of the increase in carbon in granules of active carbon with a narrow micropore size distribution in the range of 600–900°C and with methane pressures from 2.66 to 1000 hPa are similar to the dependences of the rate of precipitation of pyrocarbon on nonporous carbonaceous substances. The activation energies of the precipitation process are 230 kJ/mole with high methane pressures and 290 kj/mole with low methane pressures. 2. Precipitation of carbon from methane in the kinetic region of the process in active carbon with a narrow micropore size distribution results in a decrease in the volume of the micropores with preservation of the value of the characteristic adsorption energy. Precipitation of carbon in active carbon with a wide micropore size distribution decreases both the volume of the micropores (but to a significantly smaller degree than with a narrow size distribution) and the characteristic adsorption energy.