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<p>Glycerol oligomerization is one of the alternatives to add commercial value to surplus glycerol from biodiesel industries. Also known as glycerol self-etherification, the oligomerization process aims to produce short-chain polyglycerols, mainly diglycerol. Short-chain polyglycerols are suitable for the manufacture of food, cosmetics, and polymers. Selective glycerol oligomerization can be achieved using basic and form-selective catalysts. Due to their outstanding physical and chemical properties, activated carbons (ACs) were evaluated as catalysts for the selective oligomerization of glycerol. Different methodologies were used to modify a commercial H<sub>3</sub>PO<sub>4</sub>-AC: thermal treatment, hydrothermal treatment with NH<sub>4</sub>OH, and chemical treatment with KOH. The study mainly focused on investigating the catalytic activity of different AC structures: (1) oxygen-containing functional groups (OCFGs); (2) phosphorus-containing functional groups (PCFGs); (3) nitrogen-containing functional groups (NCFGs); and (4) K-intercalated species. The synthesized ACs were characterized through CHN elemental analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), N<sub>2</sub> physisorption, Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetry (TG), and acid-base titration. The catalytic tests were carried out at 230&#xa0;°C for 8, 16, and 24&#xa0;h and with catalyst loadings of 2 wt%, 4 wt%, and 6 wt%. OCFGs and NCFGs did not exhibit significant catalytic activity during glycerol oligomerization tests. For the acid-activated carbons, PCFGs were found to be active sites producing both polyglycerols and dehydration products. The intercalated potassium of the basic carbon leached completely and selectively produced short-chain polyglycerols through homogeneous catalysis (X<sub>G</sub><sup>24 h, 2 wt%</sup> = 29%, Y<sub>DG</sub><sup>24 h, 2 wt%</sup> = 24%).</p> Graphical Abstract <p></p>

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First Insights into the Use of Activated Carbons as Catalysts for Selective Oligomerization of Glycerol

  • 期刊论文

  • 发表日期：

    2026年2月18日

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  • Italo O. Monteiro,
  • Matheus Z. Gonçalves,
  • Cristiane A. Henriques,
  • Alexandre B. Gaspar

摘要

Glycerol oligomerization is one of the alternatives to add commercial value to surplus glycerol from biodiesel industries. Also known as glycerol self-etherification, the oligomerization process aims to produce short-chain polyglycerols, mainly diglycerol. Short-chain polyglycerols are suitable for the manufacture of food, cosmetics, and polymers. Selective glycerol oligomerization can be achieved using basic and form-selective catalysts. Due to their outstanding physical and chemical properties, activated carbons (ACs) were evaluated as catalysts for the selective oligomerization of glycerol. Different methodologies were used to modify a commercial H3PO4-AC: thermal treatment, hydrothermal treatment with NH4OH, and chemical treatment with KOH. The study mainly focused on investigating the catalytic activity of different AC structures: (1) oxygen-containing functional groups (OCFGs); (2) phosphorus-containing functional groups (PCFGs); (3) nitrogen-containing functional groups (NCFGs); and (4) K-intercalated species. The synthesized ACs were characterized through CHN elemental analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), N2 physisorption, Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetry (TG), and acid-base titration. The catalytic tests were carried out at 230 °C for 8, 16, and 24 h and with catalyst loadings of 2 wt%, 4 wt%, and 6 wt%. OCFGs and NCFGs did not exhibit significant catalytic activity during glycerol oligomerization tests. For the acid-activated carbons, PCFGs were found to be active sites producing both polyglycerols and dehydration products. The intercalated potassium of the basic carbon leached completely and selectively produced short-chain polyglycerols through homogeneous catalysis (XG24 h, 2 wt% = 29%, YDG24 h, 2 wt% = 24%).

Graphical Abstract