Hydrogen adsorption on KOH activated carbons from mesophase pitch containing Si, B, Ti or Fe

Different activated carbons with large micropore volume (0.78–0.99 cm3/g) have been prepared by KOH activation of mesophase pitch obtained by co-pyrolysis of a petroleum residue and small amounts of different compounds, triphenylsilane, borane pyridine complex, tetrabutyl orthotitanate or ferrocene. During the preparation, the Ti introduced in the petroleum residue concentrate into the activated carbon, whereas some loss of Si and Fe occurs. The compounds modify the size of mesophase structure formed during the co-pyrolysis process, as well as the apparent height of lamelae stack, Lc, both having an important effect in the development of the porosity of the activated carbon. However, there is a scarce influence of all heteroatoms in the adsorption capacity of H2 at −196 °C and at 25 °C, which seems to be mainly influenced by the volume and size of micropores of the activated carbon. Only the activated carbon containing Fe adsorbs a higher amount of hydrogen at 25 °C and 10 MPa than the expected one according to its micropore volume.