Influence of the Formaldehyde-to-Phenol Ratio in Resin Synthesis on the Production of Activated Carbons from Phenol−Formaldehyde Resins

Abstract

Phenol-formaldehyde resins synthesized using different formaldehyde-to-phenol molar ratios (F/P ratios) were used as precursors for production of activated carbons from steam activation and KOH etching. The base-catalyzed method was employed in the synthesis with the F/P ratio ranging within 1-4. It was found that the resin yield decreased with the F/P ratio, while the fixed carbon content of the resins increased with the ratio. Solid-state 13 C NMR analysis showed that increasing the F/P ratio resulted in an increased degree in aromatic ring substitution, which would lead to a promoted cross-linking upon heat treatment and thus to a higher carbon yield. The specific porosity of the carbons from steam activation was shown to decrease with the F/P ratio. The difference in the porosity has been ascribed to the different numbers of original pores embedded in the carbons prior to activation. The F/P ratio did not show obvious influence on the specific porosity development for carbon production using KOH etching. The yield for producing high-porosity carbons from KOH etching was higher than that from steam activation. For both of the activation methods, a F/P ratio of unity is recommended for creating high overall carbon porosity based on per unit mass of phenol used.

Microporous activated carbon spheres prepared from resole‐type crosslinked phenolic beads by physical activation

“…The activated carbons showed a high BET surface area (2100 m 2 /g) at higher burn-off levels ($ 80%), which corresponded to a low carbon yield (<10%). Furthermore, activated carbon from urea-impregnated cured resins 34 under the same conditions reported previously showed a higher BET surface area of 2000 m 2 /g at 70% burn-off. Activated carbons prepared in a spherical form have an advantage over powder ones, in that they have better abrasion resistance due to the absence of sharp edges and irregular shapes.…”

“…32 Teng and Wang 33 prepared activated carbons with a specific BET surface area up to 2220 m 2 /g at a higher burnoff of 78% and with a carbon yield of 12.0% by a physical and chemical etching method from phenolformaldehyde resins, which were grounded and sieved. Lin and Teng 34 reported that cured resins carbonized in N 2 at 700 C, and this was followed by gasification of the resulting char in steam at the same temperature for different extents of burn-off. The activated carbons showed a high BET surface area (2100 m 2 /g) at higher burn-off levels ($ 80%), which corresponded to a low carbon yield (<10%).…”

A simplified preparation of mesoporous carbon and the examination of the carbon accessibility for electric double layer formation

“…Carbons from phenol-formaldehyde resins are glass-like, containing a large number of original pores [36,53]. Upon slight gasification to open the isolated original pores, carbons with high microporosity can be obtained.…”

Functionalization of Porous Carbon Materials with Designed Pore Architecture

“…C NMR studies related to designed porous carbons include an investigation of the phenol-formaldehyde resin precursors, [183] porous carbon nanospheres, [184] zeolite-templated, furfuryl alcohol-based microporous carbons, [185] and mesoporous carbon CMK-3 samples before and after sulfonation. [ N NMR experiments need to address the opposite challenge: low natural abundance, a negative gyromagnetic ratio, and 50-times lower sensitivity than 13 C. Nonetheless, 15 N CP-MAS NMR spectroscopy has been successfully applied to determine nitrogen functional groups (pyrroles, indoles, carbazoles, pyridines, amides, imides, imines, and nitrile functionalities) in carbon samples, though with only modest signal-tonoise ratios.…”