Production of activated carbons from a washington lignite using phosphoric acid activation

✍ Scribed by C. Toles; S. Rimmer; J.C. Hower

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 734 KB
• Volume: 34
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/s0008-6223(96)00093-0

✦ Synopsis

Chemical activation

of a Washington state lignite was studied using heat-treatment temperatures (HTT) between 250 and 650°C. Thermal blanks were generated under similar conditions for comparison.

Changes in chemical composition of both the thermal and acid-treated carbons were followed by elemental analysis and FTIR spectroscopy.

With increasing HTT, acid-treatment promotes a more extensive loss of hydrogen.

Fourier-transform infrared spectra show a decrease in aliphatic groups, increased aromaticity and increased stability of carbonyl functions for samples that were reacted with H,PO,.

Ulminite reflectance (O/OR& of the acid-treated samples is consistently higher than the thermal counterparts up to an HTT of 550°C. Above this temperature the relationship is reversed. A rim of higher reflectance material occurs in some of the larger pieces of acid-treated carbon indicating a reaction rim. The sharp boundary may be related to the rate of diffusion of the phosphoric acid into the lignite structure.

Maximum surface area developed for the acid-treated carbons (1266 m'/g) occurs at an HTT of 450°C. The surface areas developed in these carbons is intermediate between those produced from modern white oak and subbituminous coal precursors. These preliminary data for activated carbons produced from a lignite precursor stress the importance of rank in the production of high internal surface areas by acid-activation.