Physico-Chemical nanomaterials science

Synthesis and catalytic activity of activated carbons grafted with acidic groups

Grishchenko L.M.1, Diyuk V.E.1, Novychenko N.S.2, Tsapyuk G.G.1, Mischanchuk O.V.3, Boldyrieva O.Yu.1, and Lisnyak V.V.1

1Faculty of Chemistry, Taras Shevchenko National University of Kyiv, olodymyrska Street 64/13, Kyiv 01601, Ukraine.E-mail: liudmyla.grishchenko@gmail.com

2M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, Kyiv 01004, Ukraine.

3O.O. Chuiko Institute of Surface Chemistry, National Academy of Sciences of Ukraine, Kyiv 03164, Ukraine.

Nanoporous carbon-based materials are widely used because of the unique textural and surface properties that depending on the preparation and activation methods can be significantly changed [1]. The chemical modification of the surface layer of activated carbon (AC) is important in order to prepare strong acid sites. In fact, the development, production and industrial adaptation of solid acid catalysts based on functionalized nanoporous AC are favorable from technological and environmental points of view. 
The purpose of this work was to obtain and investigate properties of solid acid AC catalysts with grafted acidic groups. We examined the catalytic activity of them in the vapor phase dehydration of isopropyl alcohol. For the acidification of selected AC, we treated them with oleum, chlorosulfonic, sulfuric acids, and sulfur vapors and sulfonated α-methylstyrene polymerized on the AC surface with sulfuric acid. When AC was treated with oleum and chlorosulfonic acid, we obtained only a small amount of chemically grafted sulphogroups, of 0.15–0.30 mmol/g. The solid acids obtained by treatment with sulfuric acid and sulfur vapors contain up to 1 mmol/g sulfo groups. The obtained samples were investigated by the TPD MS, TGA, TPD IR, and SEM. TGA showed that the synthesized solid acids have a sufficiently high thermal stability. Depending on the synthesis method, the solid acids have different catalytic activity if addressed to the temperature at the total conversion of isopropyl alcohol to propylene, which is found between 160 and 300 °C. In sum, nanoporous AC having a high concentration of sulphogroups are effective low-temperature dehydration catalysts.

1.Grishchenko L.M., Diyuk V.E., Konoplitska O.P., Lisnyak V.V., Maryichuk R.T. Modelling of copper ions adsorption onto oxidative-modified activated carbons // Adsorption Sci. Technol.-2017.-35.-P.884-900.