Porous carbon materials from anthracites

The main problem limiting the use of anthracites in the production of carbon sorbents is their low reactivity, because of which traditional methods of activation by water vapor or CO₂ prove to be insufficiently effective. The developed industrial methods for the activation of anthracites are inefficient and cannot provide a sufficiently wide range of carbon sorbents based on them. To obtain carbon sorbents with good adsorption characteristics, traditional methods of physical activation require a long time and high temperatures. In this case, a loss of more than 50% of the initial weight of anthracite occurs due to its burnout. There is evidence that a low-temperature chemical modification of anthracite (for example, HClO₄ or HNO₃) increases its reactivity with subsequent physical activation.

The development of new methods for the synthesis of nanoporous carbon materials has been used to study the activation of anthracites in a number of deposits in the presence of lithium, sodium and potassium hydroxides. As a result of the performed studies, experimental dependences connecting the textural characteristics of the obtained carbon materials with the nature of anthracite and activating agent, as well as with the conditions of the activation process, are revealed. It was found that the activating ability of hydroxides increases in the series LiOH<NaOH<KOH. The selection of regime parameters for the chemical activation of anthracites by Li, Na, K hydroxides (temperature, reagent ratio, reaction medium) allowing the production of nanoporous carbon materials with a high specific surface area is obtained. The most significant development of the specific surface area of the carbon material was detected by the activation of anthracite in the presence of potassium hydroxide (the specific surface area was about 3000 m²/g, the pore volume was 1.77 cm³/g, the average pore size was 2.2 nm). When anthracite is activated in the presence of sodium hydroxide, the specific surface area of the obtained carbon materials reaches 1500 m²/g, and for the lithium hydroxide / anthracite system it is 240 m²/g, with an average pore size of 2.6 and 1.0 nm, respectively. The selection of regime parameters for the chemical activation of anthracites with mineral acids and alkalis (temperature, reagent ratio, reaction medium) allowing the production of porous carbon materials with a high specific surface area. Based on these data, new methods for the production of porous carbon materials from anthracites with a specific surface area of 240 to 3000 m²/g and an average pore size of 1.0 to 2.6 nm have been developed.