TG–FTIR and Py–GC/MS analysis on pyrolysis and combustion of pine sawdust

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Abstract

Pyrolysis and combustion of pine sawdust have been investigated by using thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG–FTIR) analysis in this paper. Pyrolysis–gas chromatography and mass spectrometry (Py–GC/MS) analysis was employed to characterize subsequently the structure and composition of evolving gas in pine sawdust pyrolysis process. TG results showed that both pyrolysis and combustion of pine sawdust presented three weight loss stages, respectively. The apparent activation energy of pyrolysis reaction is 108.18 kJ mol−1 in temperature of 239–394 °C, while under combustion process which is 128.43 kJ mol−1 and 98.338 kJ mol−1 in 226–329 °C and 349–486 °C, respectively. The evolving gaseous products during the pyrolysis and combustion infrared spectrums such as H2O, CH4, CO, CO2, phenol and alkane were found. Py–GC/MS results indicated that the main compounds of pine sawdust thermal decomposition were small molar gases, acetaldehyde, acetic acid, anhydride with formic and acetic anhydride. And possible formation pathways for main pyrolysis products were tentatively presented.

Highlights

► Pyrolysis and combustion of pine sawdust were investigated with TG–FTIR and Py–GC/MS analysis. ► Kinetic parameters for pine sawdust pyrolysis and combustion process were obtained. ► The gaseous species were identified by the spectra: H2O, CO2, CO, CH4, phenols, and paraffin gas. ► The main compounds of pine sawdust thermal decomposing were organic acid, aldehyde and acid anhydride group.

Introduction

As a potential energy resource, biomass energy is one of most important renewable energy. There are several ways (e.g. physical, thermal, chemical, and biological conversion) to generate energy from biomass [1]. Of all the different processes for biomass utilization, the pyrolysis and combustion are main thermal methods to optimize the conversion of the chemical energy of the fuel [2].

During biomass pyrolysis and combustion, it is necessary to know the possible thermal conversion mechanisms by which pyrolysis and combustion occurs in the different molecular fractions. This may allow us to control the process in order to obtain acceptable and reusable products [3]. The determination of kinetic parameters and process products gives us information on the thermal events occurring as well as the structure and composition of the materials [4].

Thermogravimetric analysis (TG) coupled with Fourier transform infrared (FTIR) analysis is a well established method for obtaining weight loss to study biomass thermal decomposition characteristics, reaction mechanisms and evolved products during pyrolysis and combustion. This method offers the potential for the non-destructive, simultaneous, real-time measurement of multiple gas phase compounds in complex mixture. Pyrolysis and combustion thermogravimetric analysis involves the sample thermal degradation in an inert and oxygen existing atmosphere, and the loss of the sample weight was recorded simultaneously at a uniform temperature ramping rate. Weight loss and calculated kinetic parameters are easily obtained from thermogravimetric analysis without the complex chemical reactions in the thermal degradation, and the evolved gases are detected in real-time and sensitively, which is an important and often a difficult task in many thermal applications. Extensive studies had carried out with thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG–FTIR) for biomass and other materials thermal events [5], [6], [7], [8], [9].

Another way to study biomass pyrolysis components evolving is by quantitative pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). Py–GC/MS is an important technique for biomass characterization, because it involves not only the compositional information of the complex component macromolecules, but also the characteristics of volatile pyrolysis products. A number of aspects of Py–GC/MS used as a quantitative tool were discussed. And also Py–GC/MS has been shown to be a reliable analytical technique for the characteristics of biomass [10], [11], [12]. Fahmi et al. [12] determined the composition of the thermal degradation products of lignin with Py–GC/MS by the use of different biomass samples. Lu et al. [13] investigated the effect of Al/SBA-15 catalysts on biomass fast pyrolysis vapors by Py–GC/MS. Although analytical pyrolysis techniques were employed the portion of the sample which is pyrolitically volatile, comparative studies using TG–FTIR and Py-GC/MC are rare. In the present study, we quantify analysis the composition of gas evolved during the thermal degradation of pine sawdust. The thermal decomposition of pine sawdust is investigated during pyrolysis and combustion process, respectively. TG–FTIR and Py–GC/MS experiments were performed to investigate how the thermal degradation of pine sawdust will affect the structure and composition of various products formed during the pyrolysis and combustion.

Section snippets

Materials

The original material (pine sawdust) used in this study was collected from a timber mill in Dalian, China. The pine sawdust sample was ground to pass a 60-mesh screen. The carbon (C), hydrogen (H), nitrogen (N), sulphur (S) analyses of pine sawdust were performed on a CHNS/O analyzer (Elementar, VarioEL III, Germany), the ash value of the pine sawdust sample was measured by a automatic proximate analyzer (SDTGA5000, Sundy, China), oxygen (O) obtained by difference to 100%. ASTM standardized

Thermogravimetric analysis

The thermogravimetric curve and differential thermogravimetric curve during pyrolysis and combustion of pine sawdust at the heating rate of 10 °C min−1 are presented in Fig. 1, Fig. 2 respectively. Three stages were found in pyrolysis process as shown in Fig. 1. The first stage (3.26% weight loss) was attributed to moisture evaporation from ambient temperature to 120 °C. The second stage is main weight loss between 200 and 405 °C with a sharp decrease on pine sawdust weight, and this stage might be

Conclusions

The properties and characteristics of pyrolysis and combustion of pine sawdust were investigated by TG–FTIR. The kinetics parameters of pine sawdust determined by thermogravimetric data were close to literature values. Both the pyrolysis and combustion process of pine sawdust can be divided into three stages. The activation energy of pine sawdust pyrolysis is 108.18 kJ mol−1 during 239–394 °C, and the values were is 128.43 kJ mol−1 and 98.338 kJ mol−1 during 226–329 °C and 349–486 °C in combustion

Acknowledgments

The work cited in this paper was supported by the National Natural Science Foundation of China (NSFC) (51006018), China Postdoctoral Science Foundation (no. 20090451264) and by an open foundation of State Key Laboratory of Multiphase Complex Systems (no. MPCS-2011-D-11).

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