Inger Ericsson

Influence of pyrolysis parameters on results in pyrolysis-gas chromatography

Abstract Different parameters were varied when pyrolysing a low-boiling polyol (b.p. 267°C, 39 mmHg), polybutadiene, polystyrene, poly(methyl methacrylate) and a copolymer of styrene and methyl methacrylate. The parameters varied were the temperature-time profile, the temperature rise time, the ambient temperature, the carrier gas flow-rate, the sample size and the material of the sample holder. The results show that it is not always necessary or even recommendable to pyrolyse under “ideal pyrolysis” conditions. In practice, the pyrolysis conditions should be chosen on the basis of the practical problem to be solved. Therefore, the more possibilities the operator has to change the parameters, the more problems one can solve by studying the qualitative, quantitative, kinetic and catalytic effects of pyrolysis.

Studies of the thermal degradation of polysulfones by filament-pulse pyrolysis—gas chromatography

Abstract The thermal degradation of poly(1,4-phenylene ether—sulfone) (PES), Mw 47000, and of a polysulfone resin (PSR) Mw 75000, was studied by flash-pyrolysis, with a temperature rise time (TRT) of 8 ms. Pyrolysis products were monitored by a pyrolysis-gas chromatography flame ionisation detector/flame photometric detector (Py-GC-FID/FPD) and pyrolysis-gas chromatography mass spectrometry (Py-GC/MS). Special attention was given to the formation of sulphur-containing pyrolysis products. The kinetics of SO2 formation were studied by sequential pyrolysis of PES and PSR. It was possible to differentiate between the rates of formation of SO2 from PES and PSR. The rate of formation of SO2 was somewhat higher for PES than for PSR. The activation energies were 270 and 280 kJ/mol, respectively, and the frequency factors were 1014 and 1015s−1.

Determination of the temperature—time profile of the sample in pyrolysis—gas chromatography

Abstract The mean temperature-time profile in a sample has been determined in order to establish whether it is possible to equate the temperature of the pyrolyzer with that of the sample being pyrolyzed. This was done by studying the degradation of cis-1,4-polybutadiene be sequential pyrolysis. The rate of degradation was determined for different amounts (0.5–20 μg) of sample. The temperature dependence of the degradation rate was determined from an Arrhenius plot. The experimental results were combined with theoretically derived expressions for the heating of samples subjected to pyrolysis. The temperature–time profiles of different amounts of sample could then be calculated. It was found that samples thinner than 1 μm were heated to a mean temperature of 95% of the temperature of the pyrolyzer in 40 ms or faster. Too thin samples can give rise to noticeable catalytic effects. By choosing the appropriate pyrolysis conditions of sample thickness, time and temperature it is possible to assume that the temperature of the sample is nearly the same as that of the pyrolyzer.

Trace determination of high molecular weight polyvinylpyrrolidone by pyrolysis-gas chromatography

Abstract The possibilities of using pyrolysis-gas chromatography as a technique for selective determination of polyvinylpyrrolidone (PVP) in trace quantities and the use of an appropriate detector such as a thermionic specific detector (TSD) have been investigated. However, the determination down to 0.2 ppm in the presence of polyhydric alcohols and high hydrophilic polymers such as polyethylene oxide was obtained with a flame ionization detector.

Determination of the temperature—time profile of filament pyrolyzers

Abstract The temperature—time profile (TTP) of a pyrolyzer can be checked or determined by pyrolyzing a standard substance, cis -1,4-polybutadiene. This was demonstrated with a home-built and with a commercially available filament pyrolyzer. At low temperatures the TTP of these pyrolyzers can be determined with sequential pulse pyrolyses where the time of the pulse is varied. At high temperatures, when the reaction rate is fast, the yield of pyrolysis products at different pyrolysis time will give information about the temperature rise time of the pyrolyzer.

Studies of the thermal degradation of polythiophenes by pyrolysis-gas chromatography

Abstract The thermal degradation products of four polythiophenes were investigated by using pyrolysis-gas chromatography with a flame ionisation detector (FID) and a sulphur-selective flame photometric detector (FPD). The influence of pyrolysis temperature (550–1400 °C) and sample size (5–20 μg) were studied, and the rates of formation and yields of sulphur and hydrocarbons were determined. At low temperatures most of the sulphur was found as H 2 S and the most abundant hydrocarbons were hexane and heptene. At high temperatures CS 2 and C 1,2 hydrocarbons were formed secondarily. Only a very small amount of thiophenes was found. The ratio between the hydrocarbons changed somewhat with sample size, because of a change of the temperature gradient in the sample. Rates of formation for C 6 and C 7 hydrocarbons were the same for the different polythiophenes. The different chemical environment of the thiophenic ring influenced the rate of formation of H 2 S and the yield of sulphur. The yields of the aromatic and thiophenic hydrocarbons were much less than aliphatics, because of a higher degree of carbonisation for the aromatic and thiophenic hydrocarbons.

Thermal degradation of organic polymers using different metals as the pyrolysis filament

Abstract Samples of polystyrene, cis -1,4-polybutadiene, poly(methyl methacrylate) and poly-acrylonitrile were pyrolysed on filaments made from iron, nickel and platinum. Iron generally gave the highest yields of pyrolysis products. Nickel gave high yields at low temperatures, but at higher temperatures the secondary degradation became important. Platinum generally gave the lowest yields. Two sample sizes, 5 and 0.5 μg, were used to make it possible to separate the effects of catalysis from pure temperature effects.

Samples from ng to mg in pyrolysis—gas chromatography

Abstract Samples of polystryrene, polybutadiene and poly(methyl methacrylate) were pyrolysed in amounts from nanograms to miligrams. With a gas cromatograph equipped with a flame-ionization detector it was possible to detec: 1 ng of polystryrene, 10 ng of polybutadiene and 100 ng of poly(methyl methacrylate). After the addition of microgram amounts of another substance the yield of the pyrolysis procducts from the smallest samples increased. Amounts from micrograms to milligrams were pyrolysed and unambiguous calibration graphs were obtained. The highest yields were obtained by pyrolysing repeatedly for relatively short periods until no further products were formed.

Studies of the yield of sulphur from a coal sample by pyrolysis—gas chromatography

Abstract An SBN standard coal 136 (20–100 μg) was pyrolysed in order to characterise the sulphur in coal by Py-GC. The sulphur-containing pyrolysis products were separated and detected by a flame photometric detector. Simultaneously, a flame ionisation detector was used to measure the total amount of organic pyrolysis products. The influence of different conditions, sample handling, inertness of the system and pyrolysis temperature on the yield of sulphur was tested. The repeatability was good, even with sample sizes of less than 100 μg. The maximum yield of sulphur was about 40% at pyrolysis temperatures of between 1000 and 1400°C. When the coal samples were combusted after pyrolysis, an additional 30% was detected. The reason for the low yield is discussed.

Characterization of sulfur in wood pulps using pyrolysis-gas chromatography with sulfur-selective detection: Part 1. Fractionated pyrolysis

Abstract A new analytical method for the characterization of sulfur in wood and chemical pulps has been developed. The method involves fractionated pyrolysis using pyrolysis-gas chromatography (Py-GC). In fractionated pyrolysis, the sample is pyrolyzed at different temperatures in order to study particular fractions of the sample and to minimize secondary effects. In the new method, each sample is pyrolyzed at progressively increasing temperatures from 300 to 1350°C and afterwards combusted at 1350°C. The pyrolysis products are separated using a gas chromatograph equipped with a flame photometric detector (FPD) for selective detection of the sulfur-containing pyrolysis products. To develop the suggested new method, the influence of different pyrolysis parameters on the formation of sulfur-containing pyrolysis products from sulfur-treated softwoods was studied. Reference materials such as human protein and wood primary cell wall layer, rich in wood protein, were pyrolyzed in order to understand the formation of sulfur-containing products from different chemical functionalities in the biomolecules. The detection limit of the method is 1 ng.