Elucidating the role of ammonia-based salts on the preparation of cellulose-derived carbon aerogels. (6th April 2017)

• Record Type: Journal Article
• Authors: Arteaga-Pérez, Luis E.; Cápiro, Oscar Gómez; Delgado, Aaron M.; Martín, Serguei Alejandro; Jiménez, Romel
• Is Part Of: Chemical engineering science. Volume 161(2017)
• Page Start: 80
• Page End: 91
• Publication Date: 2017-04-06
• Subjects: Nanofibrils -- Pyrolysis mechanism -- Carbon aerogel -- Ammonia salt; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2016.12.019
• Languages: English
• ISSNs: 0009-2509

Abstract

Highlights: Evaluation of salt impregnation on morphological and textural properties of CNF. Elucidation of main kinetic steps in the pyrolysis mechanism of impregnated CNF. A TGA-MS-supported analysis on the pyrolysis mechanism of CNF. Abstract: The effects of using (NH4 )2 SO4 as a carbonization promoter for producing cellulose-derived carbon aerogels (CAG) was studied. The effects of pretreatment on the textural, morphological, and chemical properties of pristine cellulose nanofibers (CNF) were analyzed through N2 adsorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), elemental analysis, inductively coupled plasma optical emission spectrometry (ICP-OES), and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the thermal behaviors of raw CNF and those impregnated with (NH4 )2 SO4 were investigated by coupling thermogravimetric analysis with mass spectrometry (TGA-MS). The results suggested that the pretreatment did not cause any morphological/structural changes in the nanofibers. However, the presence of (NH4 )2 SO4 affected their pyrolysis by favoring intermolecular dehydration, thereby reducing the formation of levoglucosan and increasing the carbon yield during pyrolysis. Interestingly, above certain impregnation level, the concentration of sulfate-derived species in the gas phase increased. This phenomenon was attributed to an excess of salt within the fiber structure and on their surfaces. Consequently, the levoglucosan-to-carbon route was inhibited, and the mechanisms of intra- and inter-molecular dehydration, chain scission, and crosslinking reactions were affected, leading to a reduced char yield. The chemical effects of ammonia-based salts is elucidated supported on the interpretation of MS signals and kinetic modeling results.