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Fischer T, Kretzschmar A, Selmert V, Jovanovic S, Kungl H, Tempel H, Eichel RA. Post-treatment strategies for pyrophoric KOH-activated carbon nanofibres. RSC Adv 2024; 14:3845-3856. [PMID: 38274173 PMCID: PMC10810230 DOI: 10.1039/d3ra07096d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 12/30/2023] [Indexed: 01/27/2024] Open
Abstract
The effect of two atmospheric post-treatment conditions directly after the KOH activation of polyacrylonitrile-based nanofibres is studied in this work. As post-treatment different N2 : O2 flow conditions, namely high O2-flow and low O2-flow, are applied and their impact on occurring reactions and carbon nanofibres' properties is studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Raman spectroscopy, elemental analysis and CO2 and Ar gas adsorption. At high O2-flow conditions a pyrophoric effect was observed on the KOH-activated carbon nanofibers. Based on the obtained results from the TGA and DSC the pyrophoric effect is attributed to the oxidation reactions of metallic potassium formed during the KOH activation process and a consequent carbon combustion reaction. Suppression of this pyrophoric effect is achieved using the low O2-flow conditions due to a lower heat formation of the potassium oxidation and the absence of carbon combustion. Compared to the high O2-flow samples no partial destruction of the carbon nanofibers is observed in the SEM images. The determination of the adsorption isotherms, the surface area, the pore size distribution and the isosteric enthalpies of adsorption show the superior properties under low O2-flow conditions. The present micropore volume is increased from 0.424 cm3 g-1 at high O2-flow to 0.806 cm3 g-1 for low O2-flow samples, resulting in an increase of CO2 adsorption capacity of 38% up to 6.6 mmol g-1 at 1 bar. This significant improvement clearly points out the importance of considering highly exothermic potassium oxidation reactions and possible post-treatment strategies when applying KOH activation to electrospun carbon nanofiber materials.
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Affiliation(s)
- Tom Fischer
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-9) - Fundamental Electrochemistry Jülich 52425 Germany
- RWTH Aachen University, Institute of Physical Chemistry Aachen 52056 Germany
| | - Ansgar Kretzschmar
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-9) - Fundamental Electrochemistry Jülich 52425 Germany
| | - Victor Selmert
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-9) - Fundamental Electrochemistry Jülich 52425 Germany
- RWTH Aachen University, Institute of Physical Chemistry Aachen 52056 Germany
| | - Sven Jovanovic
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-9) - Fundamental Electrochemistry Jülich 52425 Germany
| | - Hans Kungl
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-9) - Fundamental Electrochemistry Jülich 52425 Germany
| | - Hermann Tempel
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-9) - Fundamental Electrochemistry Jülich 52425 Germany
| | - Rüdiger-A Eichel
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-9) - Fundamental Electrochemistry Jülich 52425 Germany
- RWTH Aachen University, Institute of Physical Chemistry Aachen 52056 Germany
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Gómez-Díaz D, Domínguez-Ramos L, Malucelli G, Freire MS, González-Álvarez J, Lazzari M. S/N/O-Enriched Carbons from Polyacrylonitrile-Based Block Copolymers for Selective Separation of Gas Streams. Polymers (Basel) 2024; 16:269. [PMID: 38257068 PMCID: PMC10819996 DOI: 10.3390/polym16020269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Revised: 01/12/2024] [Accepted: 01/16/2024] [Indexed: 01/24/2024] Open
Abstract
A series of polyacrylonitrile (PAN)-based block copolymers with poly(methyl methacrylate) (PMMA) as sacrificial bock were synthesized by atom transfer radical polymerization and used as precursors for the synthesis of porous carbons. The carbons enriched with O- and S-containing groups, introduced by controlled oxidation and sulfuration, respectively, were characterized by Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectrometry, and their surface textural properties were measured by a volumetric analyzer. We observed that the presence of sulfur tends to modify the structure of the carbons, from microporous to mesoporous, while the use of copolymers with a range of molar composition PAN/PMMA between 10/90 and 47/53 allows the obtainment of carbons with different degrees of porosity. The amount of sacrificial block only affects the morphology of carbons stabilized in oxygen, inducing their nanostructuration, but has no effect on their chemical composition. We also demonstrated their suitability for separating a typical N2/CO2 post-combustion stream.
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Affiliation(s)
- Diego Gómez-Díaz
- Departamento de Ingeniería Química, ETSE, Universidade de Santiago de Compostela, Rua Lope Gómez de Marzoa s/n, 15782 Santiago de Compostela, Spain; (L.D.-R.); (M.S.F.); (J.G.-Á.)
| | - Lidia Domínguez-Ramos
- Departamento de Ingeniería Química, ETSE, Universidade de Santiago de Compostela, Rua Lope Gómez de Marzoa s/n, 15782 Santiago de Compostela, Spain; (L.D.-R.); (M.S.F.); (J.G.-Á.)
- Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - Giulio Malucelli
- Department of Applied Science and Technology, Politecnico di Torino, Viale Teresa Michel 5, 15121 Alessandria, Italy;
| | - María Sonia Freire
- Departamento de Ingeniería Química, ETSE, Universidade de Santiago de Compostela, Rua Lope Gómez de Marzoa s/n, 15782 Santiago de Compostela, Spain; (L.D.-R.); (M.S.F.); (J.G.-Á.)
| | - Julia González-Álvarez
- Departamento de Ingeniería Química, ETSE, Universidade de Santiago de Compostela, Rua Lope Gómez de Marzoa s/n, 15782 Santiago de Compostela, Spain; (L.D.-R.); (M.S.F.); (J.G.-Á.)
| | - Massimo Lazzari
- Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
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Du S, Huang B, Hao GP, Huang J, Liu Z, Oschatz M, Xiao J, Lu AH. pH-Regulated Refinement of Pore Size in Carbon Spheres for Size-Sieving of Gaseous C 8 , C 6 and C 3 Hydrocarbon Pairs. CHEMSUSCHEM 2023; 16:e202300215. [PMID: 37186177 DOI: 10.1002/cssc.202300215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/24/2023] [Accepted: 04/24/2023] [Indexed: 05/17/2023]
Abstract
Selective separation of industrial important C8 , C6 and C3 hydrocarbon pairs by physisorbents can greatly reduce the energy intensity related to the currently used cryogenic distillation techniques. The achievement of size-sieving based on carbonaceous materials is desirable, but commonly hindered by the random structure of carbons often with a broad pore size distribution. Herein, a pH-regulated pre-condensation strategy was introduced to control the carbon pore architecture by the sp2 /sp3 hybridization of precursor. The lower pH value during pre-condensation of glucose facilitates the growth of aromatic nanodomains, rearrangement of stacked layers and a concomitant transition from sp3 -C to sp2 -C. The subsequent pyrolysis endows the pore size manipulated from 6.8 to 4.8 Å and narrowly distributed over a range of 0.2 Å. The refined pores enable effective size-sieving of C8 , C6 and C3 hydrocarbon pairs with high separation factor of 1.9 and 4.9 for C8 xylene (X) isomers para-X/meta-X and para-X/ortho-X, respectively, 5.1 for C6 alkane isomers n-hexane/3-methylpentane, and 22.0 for C3 H6 /C3 H8 . The excellent separation performance based-on size exclusion effect is validated by static adsorption isotherms and dynamic breakthrough experiments. This synthesis strategy provides a means of exploring advanced carbonaceous materials with controlled hybridized structure and pore sizes for challenging separation needs.
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Affiliation(s)
- Shengjun Du
- Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Ministry of Education, Department of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
- Institute for Technical Chemistry and Environmental Chemistry, Center for Energy and Environmental Chemistry Jena, Friedrich-Schiller-University, Jena, 07745, Germany
| | - Baolin Huang
- Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Ministry of Education, Department of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Guang-Ping Hao
- State Key Laboratory of Fine Chemicals, Liaoning Key Laboratory for Catalytic Conversion of Carbon Resources and School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, P. R. China
| | - Jiawu Huang
- Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Ministry of Education, Department of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Zewei Liu
- Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Ministry of Education, Department of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Martin Oschatz
- Institute for Technical Chemistry and Environmental Chemistry, Center for Energy and Environmental Chemistry Jena, Friedrich-Schiller-University, Jena, 07745, Germany
| | - Jing Xiao
- Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Ministry of Education, Department of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - An-Hui Lu
- State Key Laboratory of Fine Chemicals, Liaoning Key Laboratory for Catalytic Conversion of Carbon Resources and School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, P. R. China
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