A. Pappa

Thermal degradation of Pinus halepensis pine-needles using various analytical methods

Abstract The analytical methods of DSC, TG, DI-MS, Py-GC-FID, Py-GC-MSD were used to study the thermal degradation of Pinus halepensis pine-needles. As was shown by DSC measurements endotherm peaks could be attributed to the desorption of high volatility compounds, moisture, softening and/or melting of the waxy constituents of pine-needles; as well as to the degradation of hemicellulose and cellulose. Exotherm peaks could be attributed to the pyrolysis of lignin and char recombination. These results were reconfirmed by DTG curve. In addition, the DI-MS measurements showed, through the presence of certain mass peaks, the existence of volatile degradation products which can be related to the degradation pathways observed by DSC and TG. Py-GC-FID proved that the evolution of organic degradation products commences at 200–250 °C and has its maximum evolution rate between 350 and 450 °C. Py-GC-MSD analysis of the flash pyrolysis products at 400 °C identified a number of organic compounds and CO 2 .

Chemometric methods for studying the effects of chemicals on cellulose pyrolysis by thermogravimetry–mass spectrometry

Abstract Chemometric methods were used for extracting information out of the mixture mass spectra recorded in a thermogravimetric–mass spectrometric (TG–MS) analysis. Principal Component Analysis (PCA) and Discriminant Rotation (DR) were applied for studying the effects of fire retardants on the gases evolved during thermal degradation of cellulose. The chemicals (NH 4 ) 2 SO 4 , (NH 4 ) 2 HPO 4 and a commercial retardant (Fire Trol) were used as fire retardants. PCA and DR resulted in four factors discriminating between untreated cellulose and cellulose treated with fire retardants. For the interpretation of the factors the rotated discriminant spectra were used. For estimating the effects of the fire retardants, the score plot in the first two discriminants space was used. It was shown that in all cases the retardation action was based on various factors such as: the increase of CO 2 evolution produced by dehydration of cellulose, the relative decrease of very flammable volatile products (carbonyl compounds, reduced furans and pyranone derivatives) and the increase of levoglucosenone produced by dehydration of levoglucosan. A differentiation between the effects of (NH 4 ) 2 SO 4 and the other two retardants was also observed and it concerned mainly the production of phenol derivatives and acetic acid.

The effect of salt and oxide-hydroxide additives on the pyrolysis of cellulose and Pinus halepensis pine needles

Abstract Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) were used to study the effects of various salts and oxide-hydroxide additives on the pyrolysis of cellulose and Pinus halepensis pine needles. (NH4) 2 HPO 4 , NaH 2 PO 4 , (NH 4 ) 2 SO 4 , NaHCO 3 , KHCO 3 , (COONa) 2 , Ca(OH) 2 and Na 2 O.CaO were used as additives at concentrations of 4% w/w and 10% w/w. DSC and TGA showed that the addition of (NH 4 ) 2 HPO 4 , NaH 2 PO 4 and (NH 4 ) 2 SO 4 on cellulose causes a significant shift to lower pyrolysis temperatures, i.e. 50°C to 80°C, as well as a significant increase in char residues. The effect of NaHCO 3 , KHCO 3 , and (COONa) 2 on the pyrolysis of cellulose was also found to be significant in terms of the DSC profile, while the increase in char residues was moderate. In contrast the effect of Ca(OH) 2 and Na 2 O·CaO on the pyrolysis of cellulose was found to be minor, under the above-mentioned criteria. The above chemicals, tested as fire retardants, have shown minor effects on the pyrolysis of Pinus halepensis pine needles. Some changes, however, were noticed in the solid pyrolysis residues, particularly when (NH 4 ) 2 HPO 4 and (NH 4 ) 2 SO 4 were used.

Thermal analysis of Pinus halepensis pine-needles and their main components in the presence of (NH4)2HPO4 and (NH4)2SO4

DSC and TG were used to study the effects of fire retardants on the pyrolysis of Pinus halepensis pine-needles and their components (cellulose, lignin and extractives). (NH4)2HPO4 and (NH4)2SO4 were used as fire retardants at the 10% w/w concentration level. The TG results showed that the mass loss profile of pine-needles resembles those of lignin and extractives. The DSC curves showed that in the presence of fire retardants there is a shift to lower pyrolysis temperatures for cellulose. In addition, there is an increase in the pyrolysis residue for both cellulose and pine-needles. Minor or negligible effects were observed for lignin and extractives in the presence of the retardants.

A comparative study of the effects of fire retardants on the pyrolysis of cellulose and Pinus halepensis pine-needles

Abstract Differential scanning calorimetry (DSC) and direct inlet mass spectrometry (DI-MS) were used for studying the effects of fire retardants on the pyrolysis of cellulose and Pinus halepensis pine-needles. The compounds (NH4)2HPO4 and (NH4)2SO4 were used as fire retardants at various concentration levels. DSC showed that the addition of the fire retardants results in a shift to lower pyrolysis temperatures for cellulose and in an increase in the pyrolysis residues for both cellulose and pine-needles. DI-MS was used for monitoring the evolution rate of various pyrolysis products and for the identification of the various pyrolysis phases.

Application of factor analysis for resolving thermogravimetric-mass spectrometric analysis spectra

Factor Analysis was used for extracting information out of the mixture mass spectra recorded in a thermogravimetric–mass spectrometric analysis. Principal component analysis (PCA) and a special diagram, the contour variance diagram (ContVarDia), were used for performing the factor analysis. The method was applied for studying the thermal decomposition of Kraton 1107 copolymer. Pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) was used for identification of the pyrolysis products of Kraton 1107. The application of factor analysis resulted in the determination of the main thermal decomposition steps and the prediction of the mass spectrum corresponding to each step. Those mass spectra were either pure spectra corresponding to main evolved gases or average spectra corresponding to multiple gases evolved in one decomposition step. The advantages and the limitations of the chemometric approach were discussed.

The effect of (NH4)2HPO4 and (NH4)2SO4 on the composition of the volatile organic pyrolysis products of Pinus halepensis pine-needles

Abstract Pyrolysis gas chromatography with flame ionization detector (Py-GC-FID) and pyrolysis gas chromatography with mass selective detector (Py-GC-MSD) were used for studying the effect of (NH4)2HPO4 and (NH4)2SO4 on the pyrolysis of Pinus halepensis pine-needles. Flash Py-GC-MSD analysis of the pine-needles at 400°C, showed differences in the composition of the organic volatile products after treatment with chemicals. The major ones were the formation of new products such as levoglucosenone due to the alteration of thermal degradation mechanism, or due to the interaction of chemicals with the pine-needles pyrolysis products like benzonitrile. Py-GC-FID was applied to pine-needles in a temperature region of 100–600°C, for monitoring changes regarding the evolution profile of various pyrolysis products, as well as their pyrolysis temperature shifting in the presence of chemicals. The Py-GC-MSD and Py-GC-FID proved to be effective and promising methods for the elucidation of retardation mechanisms during the pyrolysis of pine-needles.

The effect of (NH4)2HPO4 and (NH4)2SO4 on the composition of volatile organic pyrolysis products of cellulose: PY-GC studies

Abstract Pyrolysis gas chromatography (PY-GC) was used for studying the effect of (NH 4 ) 2 HPO 4 and (NH 4 ) 2 SO 4 on the pyrolysis of cellulose. The major constituents of volatile organic pyrolysis products were examined, and the changes of their composition in the presence of the above chemicals were determined. PY-GC proved to be an effective and promising method for the elucidation of retardation mechanisms during pyrolysis.

Effects of Drying and Extraction Methods on the Quality and Antioxidant Activity of Sea Buckthorn (Hippophae rhamnoides) Berries and Leaves

Sea buckthorn is a promising source of bioactive compounds. However, there is limited information on the effect of post harvest drying and extraction of sea buckthorn on its antioxidant capacity. The effect of freeze, air, and solar dryingon the extraction yield of sea buckthorn berries and leaves was evaluated with respect to their bioactive content. Sequential extraction with solvents of different polarity and solvent-free microwave-assisted extraction were applied. Freeze-drying has better performance in the berries’ extracts, while air-drying has better performance in the leaves’ extracts. All data were analyzed by Multi Factor Analysis of Variance (ANOVA) and Duncans post-hoc tests at a level of α = .05. Although the extraction yield in the sequential extraction of sea buckthorn berries is significantly better, the leaves’ extracts exhibit superior radical scavenging ability. Accelerated solar drying appears to preserve sea buckthorn leaves without degrading their antioxidant content. The components responsible for the high antioxidant activity of leaves’ extracts were found to be several flavonoids and polyphenols. The extract obtained by the microwave extraction of fresh berries exhibits moderate antioxidant activity compared to the polar extracts of freeze-dried berries.

The pyrolytic behavior of Pinus halepensis needles observed by transmission light microscopy and stereoscopy

Abstract Two microscopic techniques were used for monitoring the changes that occur during the pyrolysis of Pinus halepensis needles at 100, 200, 250, 300, 350, 400 and 500°C. The changes were monitored by transmission light microscopy (LM) and stereoscopy. The following were observed with increasing temperature: (1) deformation of the transverse section; (2) loss of the cuticle layer and cracking of the outer layer; (3) degradation of lignin (a basic component of pine needles); and (4) tar and char formation on the external surface. These changes were attributed to chemical and physical phenomena during the pyrolysis procedure.