Nowadays, lignocellulosic composition can be determined by using thermogavimetry analysis. However, there is some limitation on it, for example lignin information cannot be obtained. On the other hand, we also can perform a wet chemical method to obtain more reliable result. My question is which method is suitable? Is it better to perform both wet method and TGA method? How does DTG can give the information of lignocellulosic constituents in biomass?
DTG curves (obtained from thermogravimetric curves) are frequently applied to biomass to evaluate pyrolysis kinetics.There is usually a qualitative conformity between t he; hemimicellulose, cellulose and lignin decomposition and the peaks values seen in the DTG curve
As you can see from DTG curve, the natural fibers decomposes in three main stages. The lignin pyrolysis occurred over a wide range of temperatures which the peak is hidden beneath peaks associated with hemicellulose and cellulose. To determine lignocellulose decomposition firstly, all impurities have to remove by cold water washing method and then extract the lignin ingredient with soxhlet system. By removing solvent you have pure lignin and by cooperation the TGA/DTG curve with the natural fiber you can easily determine the lignocellulose decomposition.
Useful paper: “Effect of oil palm kernel shell powder on the mechanical performance and thermal stability of polyester composites”
The DTG curve is often published as the negative of the first derivative of the TGA (mass loss) curve. The TGA curve for a sample volatilizing at a single temperature, for example water, will show a decline in mass when the furnace temperature reaches the volatilization temperature. At the volatilization temperature, e. g. 100°C for water, the DTG curve will show a distinct peak. Multiple peaks may be observed in the DTG curve for certain types of biomass because the volatilization temperatures of components like cellulose or lignin are distinct. Distinct peaks in the DTG curve can be either integrated, or used to determine the temperature range and subsequently the mass loss during the volatilization of a particular component.
The volatilization of a particular component can be measured fast and inexpensively on a relatively new TGA if the composition of the peaks for a particular sample are known, and the peaks on the DTG curve are distinct. If the DTG peaks are not distinct or if the composition of the DTG peaks are not known for a particular sample then established wet chemistry approaches would probably be best for measuring composition.
The DTG curve gives information about the lingo-cellulosic contents of biomass because the size and locations of the peaks offer qualitative insight into how the components of the biomass undergo thermal breakdown through processes like combustion or pyrolysis. Quantitative insight may be gained by directly measuring aspects of the peaks, or by fitting the DTG curves to kinetic models describing thermal breakdown through these same thermal processes.
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