Authors:Helena Halttunen, J. Nurmi, P. Perkkalainen, I. Pitkänen, and S. Räisänen
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
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.
Authors:H. Halttunen, M. Hurtta, I. Pitkänen, and J. Nurmi
Summary Anhydrous lactitols (A1, α- and β-lactitol), lactitol monohydrate, lactitol dihydrate and lactitol trihydrate were kept for varying times in atmospheres of different relative humidity at 20°C in equivalent size plastic desiccators. The relative humidities (8-95%) were maintained with saturated salt solutions and drying agents (silica gel and phosphorous pentoxide). The composition of the samples was monitored by thermogravimetry, differential scanning calorimetry and X-ray powder diffraction. According to these measurements both lactitol monohydrate and lactitol dihydrate were substantially stable under the conditions used. Lactitol monohydrate converts to lactitol dihydrate at the highest relative humidity used. All phases of anhydrous lactitol convert into a form of lactitol monohydrate but not to lactitol dihydrate, even at the highest relative humidity used. At a high relative humidity lactitol trihydrate easily loses part of its crystal water and converts partly to lactitol dihydrate. At a lower relative humidity, the phase forming from trihydrate is difficult to identify.
Authors:I. Pitkänen, J. Huttunen, H. Halttunen, and R. Vesterinen
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 100C mainly
lost water and a little ammonia.
Authors:J. Suuronen, I. Pitkänen, H. Halttunen, and R. Moilanen
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.
Authors:M. Lappalainen, I. Pitkänen, H. Heikkilä, and J. Nurmi
enantiomeric forms of xylose were identified as α-D-xylopyranose
and α-L-xylopyranose by powder diffraction.
Their melting behaviour was studied with conventional DSC and StepScan DSC
method, the decomposition was studied with TG and evolved gases were analyzed
with combined TG-FTIR technique. The measurements were performed at different
heating rates. The decomposition of xylose samples took place in four steps
and the main evolved gases were H2O, CO2
and furans. The initial temperature of TG measurements and the onset and peak
temperatures of DSC measurements were moved to higher temperatures as heating
rates were increased. The decomposition of L-xylose
started at slightly higher temperatures than that of D-xylose
and L-xylose melted at higher temperatures
than D-xylose. The differences were more
obvious at low heating rates. There were also differences in the melting temperatures
among different samples of the same sugar. The StepScan measurements showed
that the kinetic part of melting was considerable. The melting of xylose was
anomalous because, besides the melting, also partial thermal decomposition
and mutarotation occurred. The melting points are affected by both the method
of determination and the origin and quality of samples. Melting point analysis
with a standardized method appears to be a good measure of the quality of
crystalline xylose. However, the melting point alone cannot be used for the
identification of xylose samples in all cases.