TGA-GC-MS Measurements on Pinewood/Sapwood

Introduction

Nowadays, biomass is more and more frequently used as an alternative to conventional energy sources. Key benefit is the “CO2 neutrality“. Wood belongs to the most important renewable raw materials. The main components of wood are cellulose, hemicellulose and lignin.

1) TG 209 F1 Libra® with GC-MS coupling

Table 1: TGA measurement parameters

Parameters

Temperature rangeRT to 500°C
Heating rate10 K/min
AtmosphereHelium
Flow rate65 ml/min
Sample holderSample holder for corrosive gases
CrucibleAl2O3 (85 μl)
Sample mass6.9 mg

Table 2: GC-MS measurement parameters

ParametersQuasi-continuous ModeEvent-controlled Mode
ColumnAgilent HP-5msAgilent HP-5ms
Column length30 m30 m
Column diameter0.25 mm0.25 mm
Furnace temperature150°C100°C to 310°C (10 K/min)
GasHeliumHelium
Gas flow (split)20 ml/min (10:1)20 ml/min (10:1)
Column flow2 ml/min2 ml/min
Valveevery 2 min1x per event

Quasi-continuous Mode

Simultaneous coupling of the TGA to the GC-MS allows for easy correlation of the outgassing substances with temperature. 

The PyrolysisPyrolysis is the thermal decomposition of organic compounds in an inert atmosphere.pyrolysis of pinewood takes place in three steps (figure 2). The first step is the evolvement of the water contained. The main Reazione di DecomposizioneLa decomposizione è la reazione indotta termicamente con cui una sostanza chimica genera prodotti solidi e/o gassosi. decomposition of wood occurs at approx 300°C.

First, the cellulose components are decomposed, then the lignin components decompose.

Corresponding to the DTG curve, the main Reazione di DecomposizioneLa decomposizione è la reazione indotta termicamente con cui una sostanza chimica genera prodotti solidi e/o gassosi. decomposition can be seen at 300°C in the total ion chromatogram.

2) PyrolysisPyrolysis is the thermal decomposition of organic compounds in an inert atmosphere.Pyrolysis of pinewood: TGA (black), DTG (green) and TIC (purple) results versus temperature
3) PyrolysisPyrolysis is the thermal decomposition of organic compounds in an inert atmosphere.Pyrolysis of pinewood: TIC results versus temperature (380°C to 385°C)

An enlarged scaling of the TIC in this range is presented in figure 3; the substances detected at the peaks are listed in table 3.

Table 3: Detected molecules and their retention times

Time/MinMoleculeMolar MassMass Number
35.138Acetone5858
35.1641,2,3-Thiadiazole8658, 86
35.1722-Methylfuran8282, 81, 53
35.1892-Methyl-Mannomethylpyranosid17860, 74
35.2232-Butenal, 2-Methyl8455, 84
35.240Thiophene8484, 58, 45
35.265Furan, 2,3-Dihydro-5-Methyl8484, 55, 69
35.290Furfural9696, 95
35.2991H-Pyrazol, 1,3-Dimethyl9696, 81, 68, 54
35.3082,5-Dimethylfuran9696, 95, 81, 53
35.4092(5H)-Furanon8455, 84, 70
35.4262H-Pyran, 3,4-Dihydro8455, 84, 69
4) TGA results (black) and ion chromatograms of mass numbers 82, 96, 114, 125 and 138

The individual mass numbers for pinewood are presented in figure 4 as a function of temperature.

Event-controlled Mode

For a more detailed evaluation of the forming substances, the TGA-GC-MS measurement was carried out in the event-controlled mode (figure 5). For this, individual chromatograms at certain temperatures were recorded.

5) TGA results (black) and temperature (red) versus time
6) TIC results versus time at 350°C

Figure 6 shows the chromatogram at 350 °C. The substances measured at the corresponding retention times are presented in table 4.

Table 4: Detected molecules at 350°C and their retention times

Parameters

Retention time/minSubstance
1.047CO2
1.0883(2H)-Furanon, Dihydro-2-Methyl
1.1241-Propanol
1.1971-Hydroxy-2-Propanone
1.3052(5H)-Furanon
1.330Acetic Acid, Methylester
1.370Acetone
1.4244H-1,2,4-Tiazol, 4-Amino
1.528Fufural
1.5762-Furanmethanol
1.8882(3H)-Furanon, 5-Methyl
3.073Phenol, 2-Methoxy
4.150Phenol, 2-Methyoxy-4-Methyl