H. Halttunen

Formation of the main degradation compounds from arabinose, xylose, mannose and arabinitol during pyrolysis

The thermochemical behaviour of sugars (D- and DL-arabinose, D- and DL-xylose and D-mannose) and sugar alcohol (D- and DL-arabinitol) was investigated by TG and pyrolysis-gas chromatography with mass-selective detection (Py-GC/MSD). The temperature of pyrolysis was 500 and 550°C. The TG-curves were measured both in air and nitrogen atmospheres, from 25 to 700°C with the heating rate of 2°C min-1. In each case, the main pyrolysis products were classified into the following compound groups: (i) furanes, (ii) pyranes, (iii) cyclopentanes, (iv) cyclohexanes, (v) anhydroglucopyranoses, (vi) dianhydroglucopyranoses and (vii) saturated fatty acids. For example, the main peaks of the chromatograms of pentoses (arabinose, xylose), hexose (mannose) and sugar alcohols (arabinitols) were different. The greatest peak of pentoses in gas-chromatogram was 2-furancarboxaldehyde and that of hexose was (2H)-furan-3-one. The greatest peak of arabinitols at pyrolysis temperature of 500°C was furan methanol and at 550°C a-angeligalactone. 5-hydroxymethyl-2-furan carboxaldehyde was found only in the pyrolysis of D-mannose (hexose). The former study showed that it was not found in pyrolysis of pentoses. The amount of CO2 and H2O was not determined.

Evolved gas analysis of some solid fuels by TG-FTIR

FTIR spectrometry combined with TG provides information regarding mass changes in a sample and permits qualitative identification of the gases evolved during thermal degradation. Various fuels were studied: coal, peat, wood chips, bark, reed canary grass and municipal solid waste. The gases evolved in a TG analyser were transferred to the FTIR via a heated teflon line. The spectra and thermoanalytical curves indicated that the major gases evolved were carbon dioxide and water, while there were many minor gases, e.g. carbon monoxide, methane, ethane, methanol, ethanol, formic acid, acetic acid and formaldehyde. Separate evolved gas spectra also revealed the release of ammonia from biomasses and peat. Sulphur dioxide and nitric oxide were found in some cases. The evolution of the minor gases and water parallelled the first step in the TG curve. Solid fuels dried at 100°C mainly lost water and a little ammonia.

Formation of the main gas compounds during thermal analysis and pyrolysis: Betaine and betaine monohydrate

The thermochemical behaviour of betaine and betaine monohydrate was investigated under two degradation conditions. Betaine was heated up to 700°C at 10°C min−1 in air and nitrogen flows and the evolved gas was analysed with the combined TG-FTRIR system. The evolved gas from betaine pyrolysis at 350 and 400°C was analysed by gas chromatography using mass-selective detection (Py-GC/MSD). In addition, the electron impact mass spectra of betaine and betaine monohydrate were measured.Esterification is one of the most important pyrolytic processes involving beta- ines. Even glycine betaine can change to dimethylglycine methyl ester via intermolecular transalkylation by heating. Trimethylamine, CO2, and glycine esters were the main degradation products. Small amounts of ester type compounds evolved both in pyrolysis and with TG-FTIR. The monohydrate lost water between 35 and 260°C while the main decomposition took place at 245-360°C. The residual carbon burnt in air to CO2 up to a temperature 570°C.

Solid state co-crystallization of sugar alcohols measured with differential scanning calorimetry☆

Abstract Mixtures of sugar alcohols xylitol, D-sorbitol and D-mannitol were prepared by grinding the solid starting materials together for 20 min. Possible co-crystals were identified by DSC and X-ray powder diffraction. The phase diagrams for the systems xylitol-D-sorbitol, xylitol-D-mannitol and D-sorbitol-D-mannitol were created using the peak values from the DSC measurements as melting points. The phase diagram for xylitol and D-sorbitol showed that co-crystallization between these two components may be achieved by grinding them together. The powder diffraction pattern for a mixture of 0.50 mole fraction of xylitol and 0.50 mole fraction of D-sorbitol showed that the product consisted of both starting reagents and a new co-crystallization product. The melting point of the co-crystallization product was 75–77°C measured from the peak value of DSC measurements.

Comparison of two melting range analysis methods with lactitol monohydrate

Abstract In pharmacopoeia, the melting point is determined by a standard method with a melting point instrument. The melting point can also be determined with differential scanning calorimetry (DSC). In this study, the standard method and DSC method are compared for determining the melting range of lactitol monohydrate. The effect of initial temperature, grinding, and drying on the melting range of different lactitol monohydrate samples was studied by a melting point instrument. The melting point and melting enthalpy of the stable form of lactitol monohydrate was identified by DSC. The statistical analysis of the results is based on a t-test. All studied variables had a small effect on the melting range. Repeatability of these two methods was calculated. The intermediate precision was also determined for the measurements of the melting point instrument. The melting range of lactitol monohydrate taking into account the intermediate precision is 94–100°C determined with a melting point instrument. The melting range determined with the DSC is according to these measurements 93–99°C and the melting enthalpy is 58.5±1.0 kJ mol −1 .

Influence of drying to the structure of lactitol monohydrate

The purpose of this study is to find out the effect of the crystal water content on the crystal structure of lactitol monohydrate. Crystal water was removed by drying over silicagel at 40°C and by using phosphorus pentoxide as drying agent at 20°C.The amouts of water removals were identified by thermogravimetry, the melting points and the heat of fusions were calculated from the results of differential scanning calorimetry measurements and the structure of samples were identified by X-ray powder diffraction method.Over 23 w/w% of total water content could removed by gently drying until significant structural changes could be detected. The melting point of anhydrous lactitol obtained by drying lactitol monohydrate was 120°C and the melting enthalpy was 102 J g−1 when measured with heating rate 10°C min−1 by DSC.

Thermal behaviour of anhydrous, dihydrate and (2/1) ethanol forms of 1-O-α-d-glucopyranosyl-d-mannitol

Abstract The melting points of anhydrous 1-O-α- d -glucopyranosyl- d -mannitol, 1-O-α- d -glucopyranosyl- d -mannitol dihydrate and a new compound, 1-O-α- d -glucopyranosyl- d -mannitol-ethanol (2/1) were determined using differential scanning calorimetry. The melting onset values were 169.2 (3), 104.3 (18) and 158.7 (9), respectively, and the melting peak values were 171.4 (5), 107.9 (15) and 160.1 (6), respectively. 1-O-α- d -glucopyranosyl- d -mannitol dihydrate and 1-O-α- d -glucopyranosyl- d -mannitol-ethanol (2/1) decompose to anhydrous form when heated at slow heating rates. According to TG-FTIR measurements, 1-O-α- d -glucopyranosyl- d -mannitol-ethanol (2/1) lost its ethanol in the 110–190°C range, and 1-O-α- d -glucopyranosyl- d -mannitol dihydrate lost its crystal water in the 60–210°C range. After removal of ethanol and crystal water, both decomposed in air totally as carbohydrates usually do, forming lower hydrocarbons with OH-groups, CO2 and H2O.