Characterization of the Structural Features of Char from the Pyrolysis of Cane Trash Using Fourier Transform−Raman Spectroscopy

Abstract

Structural features of chars from the pyrolysis of cane trash in a fluidized-bed/fixed-bed reactor under both slow and fast heating rate conditions were investigated using Raman spectroscopy. Chars from the pyrolysis of coals were also investigated for comparison. Spectra were curve-fitted using 10 Gaussian bands representing different structural features of the chars. Differences in the total Raman intensity between cane trash chars and the chars of 3 coals of varying rank were great at low pyrolysis temperature (600°C) but decreased as the pyrolysis temperature was increased to 900°C. Both low (10 K min -1 ) and high (>10 3 -10 4 K s -1 ) particle heating rates resulted in increased aromatization and relative aromatic ring size with increasing pyrolysis temperature from 600 to 900°C. However, pyrolysis at slow and fast heating rates gave chars of very different structural features as revealed by Raman spectroscopy.

Simple procedure for an estimation of the coal rank using micro-Raman spectroscopy

“…This simple fit is satisfactory for the spectra of vitrinite grains with %R r values as low as 0.18 (Fig. 4b) It has to be kept in mind that the choice to fit the spectra with only two Lorentzian curves implies that the fit parameters obtained for both bands cannot be attributed to vibrational modes of specific groups (Keown et al, 2007;Li et al, 2006a,b;Zhang et al, 2011) because each of them accounts for several disorder-induced additional modes of the coal lattice. In this way, the fit parameters, although without deep physical meaning, describe in unique way the grains with different %R r value and are promising empirical quantitative attributes of the vitrinite grains.…”

“…Guedes et al (2010) used 6 lines to fit the Raman spectra of coals; however, their fit does not include the D2 vibration mentioned by Sadezky et al (2005) or Chabalala et al (2011). Several authors utilized as many as 10 different lines between 1200 and 1800 cm −1 to fit the spectra from chars of brown coal (Li et al, 2006a,b;Zhang et al, 2011) or biomass (Keown et al, 2007).…”

Biomass Chars: The Effects of Pyrolysis Conditions on Their Morphology, Structure, Chemical Properties and Reactivity

“…This is related to the decrease of the highly reactive structures such as cycloheptane-and cyclooctane-centered ring systems, defective cyclic clusters and aromatic rings with pyrene sizes in the region of 800 to 1100 cm −1 , and to the pyrolysis of carbonyl bearing structures in the region of 1700 to 1900 cm −1 [30]. The decrease of the Raman signal in these regions (together with the valley region which is related to the amorphous carbon structures) is reflected in a decrease of the TRA with temperature, which was also denoted in [16] for cane trash chars, in [30] for mallee wood chars, as well as in [31] for miscanthus chars.…”

Effect of Temperature on the Evolution of Physical Structure and Chemical Properties of Bio-char Derived from Co-pyrolysis of Lignin with High-Density Polyethylene

“…An obvious increase in the band intensity of CB-550 was observed. This result was attributed to the high relative content of minerals (confirmed by XRD analysis), especially Ca and Na, which passively impact the Raman peak intensity by accelerating the formation of condensed aromatic ring structures (Keown et al 2007). Moreover, two broad peaks at 1340 cm -1 and 1580 cm -1 were observed, implying structural disorder and multiphase bio-char structure.…”

“…Raman spectroscopy was applied to investigate structure, specifically the amorphous, crystalline, and aromatic nature of co-pyrolysis-derived bio-char (Keown et al 2007). Figure 2a shows the Raman spectrum of lignin and its derived bio-char samples.…”