Chemistry, Physics and Technology of Surface

ISSN 2518-1238 (Online), ISSN 2079-1704 (Print)

The purpose of this work is to study the influence of the activation temperature on the porous structure characteristics of carbonaceous materials (CMs) prepared from long-flame coal under thermoprogrammed activation at the KОН/coal ratio R_KOH = 1.0 g/g.

The CMs were obtained in argon in three stages: 1) heating (4 grad/min) to the specified temperature t in the range of 350–825 °С; 2) isothermal exposure 1 h; 3) cooling, washing from alkali and drying. Samples are denoted as CM(t). The CM yield (Y, %) and CMs elemental composition are determined. Based on low-temperature (77 K) nitrogen adsorption-desorption isotherms, integral and differential dependences of the specific surface area S_DFT (m²/g) and pore volume V (cm³/g) on the average pore diameter (D, nm) were calculated by 2D-NLDFT-НS method (SAIEUS program). They were used to define volumes of ultramicropores (V_umi), supermicropores (V_smi) and micropores (V_mi). The total pore volume V was calculated from the nitrogen amount adsorbed at a relative pressure p/p₀ ~ 1.0. The S values of ultramicropores (S_umi), supermicropores (S_smi) and micropores (S_mi) were similarly determined.

The CM yield was established to decrease linearly (R² = 0.979) from 70.2 to 45.3 % with an increase in temperature from 350 to 825 °С. The carbon content decreases to a minimum value at 500 °С (72.6 %), and then increases to a maximum value (87.5 %) at 825 °С; the oxygen content changes antibatically. Two temperature regions were identified: region I (≤ 500 °С) of increasing the oxygen content due to reactions in which KOH acts as a donor of O atoms; region II (≥ 500 °C) of dominating the thermal destruction of functional groups (carboxyl, lactone, ester) with the release of CO and CO₂, and condensation increasing the size of polyarenes of the CM secondary framework and formsng single С_ar-С_аr bonds between them. The CM(350) sample was found to contain only mesopores (D ≥ 10 nm) and macropores. An activation temperature increase to 400 °C initiates the additional formation of small-diameter micropores and mesopores. In samples CM(400) - CM(825), the main portion of newly formed pores falls on pores with D ≤ 5 nm. With increasing temperature, the micropores volume increases almost linearly (R² = 0.992). The V_umi and V_smi volumes increase up to 600 °C. At higher temperatures the ultramicropores volume decreases due to transforming ultramicropores (D ≤ 0.7 nm) into supermicropores (D = 0.7–2.0 nm). Portion of the ultramicropores volume changes with a maximum (23.9 %) in the CM(600) sample. The S_BET specific surface area linearly (R² = 0.992) increases with temperature up to 1729 m²/g. The S_DFT values are close to S_BET, but noticeably lower (1514–1530 m²/g) for CM(785)-CM(825). The micropores specific surface area increases to 1415 m²/g, and ultramicropore surface S_umi changes extremely with a maximum (526 m²/g) for the CM(600) sample, which should be expected based on the temperature dependence of the V_umi parameter. The decrease in S_umi values after the maximum is compensated by an increase in the supermicropore surface. Such an effect - the redistribution of pores by size in the microporous range (D ≤ 2 nm) with an increase in the alkaline activation temperature is not described in the literature. The portion of the micropores surface is dominant (92.6–97.0 %) in samples prepared at t ≥ 450 °C. The portion of the ultramicropore surface is maximum (56.3 %) in CM(500). Pores are revealed that do not form at all at 450–750 °C. These are supermicropores (D = 0.96–2.00 nm) and mesopores of small diameters (D = 2.0–2.82 nm). This effect was assumed to be due to the properties of the CM supramolecular framework, which is formed from polyarene fragments of the initial and activated coals having polyarenes with diameters of the same order (1.68–2.54 nm).

1. Mochizuki T., Kubota M., Matsuda H., D'Elia Camacho L.F. Adsorption behaviors of ammonia and hydrogen sulfide on activated carbon prepared from petroleum coke by KOH chemical activation. Fuel Process. Technol. 2016. 144: 164. https://doi.org/10.1016/j.fuproc.2015.12.012

2. Javed H., Luong D.X., Lee C.-G., Zhang D., Tour J.M., Alvarez P.J.J. Efficient removal of bisphenol-A by ultra-high surface area porous activated carbon derived from asphalt. Carbon. 2018. 140: 441. https://doi.org/10.1016/j.carbon.2018.08.038

3. Wei F., Zhang H., He X., Ma H., Dong S., Xie X. Synthesis of porous carbons from coal tar pitch for high-performance supercapacitors. New Carbon Mater. 2019. 34(2): 132. https://doi.org/10.1016/S1872-5805(19)60006-5

4. Heimböckel R., Kraas S., Hoffmann F., Fröba M. Increase of porosity by combining semi-carbonization and KOH activation of formaldehyde resins to prepare high surface area carbons for supercapacitor applications. Appl. Surf. Sci. 2018. 427(Part A): 1055. https://doi.org/10.1016/j.apsusc.2017.08.095

5. Cheng J., Gu J.-J., Tao W., Wang P., Liu L., Wang C.-Y., Li Y.-K., Feng X.-H., Qiu G.-H., Cao F.-F. Edible fungus slag derived nitrogen-doped hierarchical porous carbon as a high-performance adsorbent for rapid removal of organic pollutants from water. Bioresour. Technol. 2019. 294: Article 122149. https://doi.org/10.1016/j.biortech.2019.122149

6. Yakaboylu G.A., Yumak T., Jiang C., Zondlo J.W., Wang J., Sabolsky E.M. Preparation of highly porous carbon through slow oxidative torrefaction, pyrolysis, and chemical activation of lignocellulosic biomass for high-performance supercapacitors. Energy Fuels. 2019. 33(9): 9309. https://doi.org/10.1021/acs.energyfuels.9b01260

7. Li Y., Liang Y., Hu H., Dong H., Zheng M., Xiao Y., Liu Y. KNO3-mediated synthesis of high-surface-area polyacrylonitrile-based carbon material for exceptional supercapacitors. Carbon. 2019. 152: 120. https://doi.org/10.1016/j.carbon.2019.06.001

8. Liang Y., Huang G., Zhang Q., Yang Y., Zhou J., Cai J. Hierarchical porous carbons from biowaste: Hydrothermal carbonization and high-performance for Rhodamine B adsorptive removal. J. Mol. Liq. 2021. 330: Article 115580. https://doi.org/10.1016/j.molliq.2021.115580

9. Liu Z., Hu J., Shen F., Tian D., Huang M., He J., Zou J., Zhao L., Zeng Y. Trichoderma bridges waste biomass and ultra-high specific surface area carbon to achieve a high-performance supercapacitor. J. Power Sources. 2021. 497: Article 229880. https://doi.org/10.1016/j.jpowsour.2021.229880

10. Du Z., Wang Q., Du Y., Xu Q., Wang D., Zhang W. Obtaining high-value nitrogen-containing carbon nanosheets with ultrahigh surface area from waste sludge for energy storage and wastewater treatment. Sci. Total Environ. 2021. 805: Article 150353. https://doi.org/10.1016/j.scitotenv.2021.150353

11. Zhao R., Yang X., She Z., Wu Q., Shi K., Xie Q., Ruan Y. Ultrahigh-surface-area and N,O co-doping porous carbon derived from biomass waste for high-performance symmetric supercapacitors. Energy Fuels. 2023. 37(4): 3110. https://doi.org/10.1021/acs.energyfuels.2c02916

12. Hamyali H., Nosratinia F., Rashidi A., Ardjmand M. Anthracite coal-derived activated carbon as an effectiveness adsorbent for superior gas adsorption and CO2 / N2 and CO2 / CH4 selectivity: Experimental and DFT study. J. Environ. Chem. Eng. 2022. 10(1): Article 107007. https://doi.org/10.1016/j.jece.2021.107007

13. Tiwari D., Bhunia H., Bajpai P.K. Adsorption of CO2 on KOH activated, N-enriched carbon derived from urea formaldehyde resin: kinetics, isotherm and thermodynamic studies. Appl. Surf. Sci. 2018. 439: 760. https://doi.org/10.1016/j.apsusc.2017.12.203

14. Zhang P., Wang J., Fan W., Zhong Y., Zhang Y., Deng Q., Zeng Z., Deng S. Ultramicroporous carbons with extremely narrow pore size distribution via in-situ ionic activation for efficient gas-mixture separation. Chem. Eng. J. 2019. 375: Article 121931. https://doi.org/10.1016/j.cej.2019.121931

15. Chmiola J., Yushin G., Gogotsi Y., Portet C., Simon P., Taberna P.L. Anomalous increase in carbon capacitance at pore sizes less than 1 nanometer. Science. 2006. 313(5794): 1760. https://doi.org/10.1126/science.1132195

16. Jiang Y., Chen J., Zeng Q., Zou Z., Li J., Zeng L., Sun W., Li C.M. Facile method to produce sub-1 nm pore-rich carbon from biomass wastes for high performance supercapacitors. J. Colloid Interface Sci. 2022. 612: 213. https://doi.org/10.1016/j.jcis.2021.12.144

17. Guerrera J.V., Burrow J.N., Eichler J.E., Rahman M.Z., Namireddy M.V., Friedman K.A., Coffman S.S., Calabro D.C., Mullins C.B. Evaluation of two potassium-based activation agents for the production of oxygen- and nitrogen-doped porous carbons. Energy Fuels. 2020. 34(5): 6101. https://doi.org/10.1021/acs.energyfuels.0c00427

18. So S.H., Lee S., Mun J., Rho J., Park C.R. What induces the dense storage of hydrogen of liquid- or solid-like density levels in carbon nanopores with sub-1 nm diameters? Carbon. 2023. 204: 594. https://doi.org/10.1016/j.carbon.2022.12.057

19. Zhang Y., Peng J., Feng G., Presser V. Hydration shell energy barrier differences of sub-nanometer carbon pores enable ion sieving and selective ion removal. Chem. Eng. J. 2021. 419: Article 129438. https://doi.org/10.1016/j.cej.2021.129438

20. Gao Y., Yue Q., Gao B., Li A. Insight into activated carbon from different kinds of chemical activating agents: A review. Sci. Total Environ. 2022. 746: Article 141094. https://doi.org/10.1016/j.scitotenv.2020.141094

21. Singh G., Ruban A.M., Geng X., Vinu A. Recognizing the potential of K-salts, apart from KOH, for generating porous carbons using chemical activation. Chem. Eng. J. 2023. 451(4): Article 139045. https://doi.org/10.1016/j.cej.2022.139045

22. Tamarkina Yu.V., Anishchenko V.M., Redko A.M., Kucherenko V.O. Alkali activated coals. Microporous structure and capability to adsorb phenol compounds. Him. Fiz. Tehnol. Poverhni. 2022. 13(1): 111. [in Ukrainian]. https://doi.org/10.15407/hftp13.01.111

23. Jagiello J. Olivier J.P. 2D-NLDFT adsorption models for carbon slit-shaped pores with surface energetical heterogeneity and geometrical corrugation. Carbon. 2013. 55: 70. https://doi.org/10.1016/j.carbon.2012.12.011

24. Jagiello J., Kyotani T., Nishihara H. Development of a simple NLDFT model for the analysis of adsorption isotherms on zeolite templated carbon (ZTC). Carbon. 2020. 169: 205. https://doi.org/10.1016/j.carbon.2020.06.032

25. Thommes M., Kaneko K., Neimark A.V., Olivier J.P., Rodriguez-Reinoso F., Rouquerol J., Sing K.S.W. Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report). Pure Appl. Chem. 2015. 87(9-10): 1051. https://doi.org/10.1515/pac-2014-1117

26. Saranchuk V.I., Butuzova L.F., Minkova V.N. Thermochemical destruction of coals. (Kyiv: Naukova dumka, 1993). [in Russian].

27. Tamarkina Yu.V., Kucherenko V.A., Shendrik T.G. Alkaline activation of coals and carbonbase materials. Solid Fuel Chem. 2014. 48(4): 251. https://doi.org/10.3103/S0361521914040119

28. Utz B.R., Nowak M.A., Fauth D.J. Nucleophilic properties of molten hydroxides in the desulfurization of coal and model compounds. In: Proceedings of 1989 ICCS, October 23-27, Tokyo, Japan. 1: 197.

29. Nesmeyanov A.N., Nesmeyanov N.F. Beginnigs of inorganic chemistry. Part 2. (Moskow: Khimia, 1974). [in Russian].

30. Tamarkina Yu.V., Saberova V.O., Kucherenko V.O. Formation of potassium humates during alkaline activation of brown coal. Issues of Chemistry and Chemical Technology. 2019. 6: 221. [in Ukrainian]. https://doi.org/10.32434/0321-4095-2019-127-6-221-227

31. Yoshizawa N., Maruyama K., Yamada Y., Ishikawa E., Kobayashi M., Toda Y., Shiraishi M. XRD-evaluation of KOH activation process and influence of coal rank. Fuel. 2002. 81(13): 1717. https://doi.org/10.1016/S0016-2361(02)00101-1

32. Lillo-Rodenas M.A., Juan-Juan J., Cazorla-Amoros D., Linares-Solano A. About reactions occurring during chemical activation with hydroxides. Carbon. 2004. 42(7): 1371. https://doi.org/10.1016/j.carbon.2004.01.008

33. Tamarkina Yu.V., Tamko V.A., Kucherenko V.A., Shendrik T.G. Formation of alkanes C1-C4 under alkali activation of brown coal. J. Appl. Chem. 2013. 86(12): 1226. [in Russian]. https://doi.org/10.1134/S1070427213120045

34. Saberova V.A., Tamarkina Yu.V., Kucherenko V.A. Changing the structure of brown coal by alkaline activation with thermal shock. Solid Fuel Chem. 2019. 53(3): 135. https://doi.org/10.3103/S0361521919030091

35. Clar E. Polycyclic Hydrocarbons. (New York: Academic Press, 1964). [in Russian]. https://doi.org/10.1007/978-3-662-01665-7

36. Yang T., Lua A.C. Characteristics of activated carbons prepared from pistachio-nut shells by potassium hydroxide activation. Microporous Mesoporous Mater. 2003. 63(1-3): 113. https://doi.org/10.1016/S1387-1811(03)00456-6

37. Xiao R., Xu S., Li Q., Su Y. The effects of hydrogen on KOH activation of petroleum coke. J. Anal. Appl. Pyrolysis. 2012. 96: 120. https://doi.org/10.1016/j.jaap.2012.03.013

38. Lillo-Ródenas M.A., Marco-Lozar J.P., Cazorla-Amorós D., Linares-Solano A. Activated carbons prepared by pyrolysis of mixtures of carbon precursor/alkaline hydroxide. J. Anal. Appl. Pyrolysis. 2007. 80(1): 166. https://doi.org/10.1016/j.jaap.2007.01.014

39. Illingworth J.M., Brian R., Williams P.T. Understanding the mechanism of two-step, pyrolysis-alkali chemical activation of fibrous biomass for the production of activated carbon fibre matting. Fuel Proces. Technol. 2022. 235: Article 107348. https://doi.org/10.1016/j.fuproc.2022.107348

40. Serafin J., Dziejarski B., Cruz Junior O.F., Sreńscek-Nazzal J. Design of highly microporous activated carbons based on walnut shell biomass for H2 and CO2 storage. Carbon. 2023. 201: 633. https://doi.org/10.1016/j.carbon.2022.09.013

41. Singh G., Ruban A.M., Geng X., Vinu A. Recognizing the potential of K-salts, apart from KOH, for generating porous carbons using chemical activation. Chem. Eng. J. 2023. 451(4): Article 139045. https://doi.org/10.1016/j.cej.2022.139045

42. Abbaci F., Nait-Merzoug A., Guellati O., Harat A., El Haskouri J., Delhalle J., Mekhalif Z., Guerioune M. Bio/KOH ratio effect on activated biochar and their dye based wastewater depollution. J. Anal. Appl. Pyrolysis. 2022. 162: Article 105452. https://doi.org/10.1016/j.jaap.2022.105452

43. Kucherenko V.A., Tamarkina Yu.V., Saberova V.A., Influence of temperature on the surface area development of brown coal materials under heat shock alkali activation. Issues of Chemistry and Chemical Technology. 2019. 1: 100. [in Ukrainian]. https://doi.org/10.32434/0321-4095-2019-122-1-100-106

44. Tamarkina Yu.V., Sabierova V.O., Mysyk R.D., Kucherenko V.O. Change of coals supramolecular structure during activation of potassium hydroxide. J. Coal Chemistry. 2019. 4: 4. [in Russian]. https://doi.org/10.31081/1681-309X-2019-0-4-4-11