Study of the thermal decomposition of polymers by on-line cross-correlation gas chromatography

Urbas, E.; Kaljurand, Mihkel; Küllik, E.

doi:10.1016/0165-2370(80)80004-0

Cited by 9 publications

(5 citation statements)

References 3 publications

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“…Work done by Ide et al shows a similar trend while degrading polystyrene with active charcoal as a catalyst. Styrene evolution from thermally degrading polystyrene has been used to represent the decomposition process by many researchers. ,,,, Using the TG/MS data obtained on thin polystyrene film, we compared the conversion calculated from monomer yield ( m / z 104, representing styrene) to the yields obtained from the weight-loss curve. Figure shows the conversion curves based on styrene yield and weight loss.…”

Section: Resultsmentioning

confidence: 99%

“…These observations lend support to our proposed used of the styrene evolution profile to represent polystyrene thermal degradation. The thermal decomposition kinetics of polystyrene are well studied. − ,,,,− , In the literature, the reported apparent activation energies of decomposition range from 20 to 83 kcal/mol. ,, Using the data obtained by TG/MS an Arrhenius plot was constructed using a first-order rate law (the plot is shown in Figure ). The calculated values of activation energies and frequency factors are shown in Table .…”

Section: Resultsmentioning

confidence: 99%

“…To achieve these conditions, we constructed and tested the CO 2 laser pyrolysis system (shown in Figure ). − Porous (Spherocarb) and nonporous (Glassy Carbon) spherical particles were selected as the carbonaceous substrates, and polystyrene was chosen as the model polymer for these studies. Not only is polystyrene one of the most extensively studied and characterized polymers, − but also it has some degree of structural resemblance to coal in that alkylaromatic “tar” components are produced upon pyrolysis. − Hence, studying the thermal degradation behavior of polystyrene in the presence of porous and nonporous carbonaceous substrates could help shed light on the effect of porosity on the elution of similar products from coal.

1 Schematic layout of the laser pyrolysis system. …”

Section: Introductionmentioning

confidence: 99%

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Effect of Porous and Nonporous Carbonaceous Substrates on Polystyrene Thermal Degradation during Fast CO₂ Laser Heating

et al. 1999

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To investigate the effect of porosity on elution of volatiles from a devolatilizing coal particle under pulverized coal combustion (PCC) type heating rate conditions, polystyrene was doped into porous model char (Spherocarb) particles and also coated on the surface of nonporous model char (Glassy Carbon) particles. Particles of approximately 80 µm (( 10 µm) diameter were then individually handpicked. These 80 µm diameter particles were heated to a temperature in the range of 1200-2000 K in 32 ms by means of two converging CO 2 laser beams. The eluted products were analyzed by combined gas chromatography/mass spectrometry (GC/MS). The evolved product information was used to construct yield curves. These yield curves were compared to a simple first-order rate law prediction. It was observed that while the styrene yield profile was predicted satisfactorily in the case of nonporous Glassy Carbon, styrene evolution rates were approximately four times slower than predicted in the case of porous Spherocarb. Also, the ratio of secondary pyrolysis products of polystyrene (benzene, toluene, etc.) to a primary pyrolysis product (styrene) was approximately four times higher in the case of Spherocarb than in the Glassy Carbon case. Both findings strongly suggest the presence of transport limitations in porous Spherocarb under PCC-type heating rate conditions.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

1 Schematic layout of the laser pyrolysis system. …”

Section: Introductionmentioning

confidence: 99%

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Effect of Porous and Nonporous Carbonaceous Substrates on Polystyrene Thermal Degradation during Fast CO₂ Laser Heating

et al. 1999

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“…Multiplexing GC was used to study the thermal decomposition of polymers. − The chromatograms in this case represent an averaged chromatogram of the peaks which elute within the time duration of the last PRBS. However, for a true high-throughput measurement, it is expected that the composition of a sample can be analyzed exactly at the time of each injection.…”

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confidence: 99%

“…Since the introduction of mpGC in 1967, several very fast gas injection systems, which define the sample volume via gas volume flow and time, have been designed and tested for mpGC. Such an injection can take place by controlling the time for opening and closing of solenoid valves ,,,, or with fluidic switching elements like a bistable fluidic amplifier or a deans switch. , According to Hagen–Poiseuille’s law, a laminar volume flow along a pipe depends also on the viscosity of the sample. In cases where concentrations and therefore also the viscosity of the sample are changing, injecting reproducible sample volumes via controlling the duration of a volume flow is not possible.…”

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Online High Throughput Measurements for Fast Catalytic Reactions Using Time-Division Multiplexing Gas Chromatography

et al. 2018

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Developing new catalysts is crucial for optimization of chemical processes. Thus, advanced analytical methods are required to determine the catalytic performance of new catalysts accurately. Usually, gas chromatographic methods are employed to analyze quantitatively the product distribution of volatile compounds generated by a specific catalyst. However, the characterization of rapidly changing catalysts, e.g., due to deactivation, still poses an analytical challenge because gas chromatographic methods are too slow for monitoring the change of the complex product spectra. Here, we developed a gas chromatographic technique based on the concept of multiplexing gas chromatography (mpGC) for fast and comprehensive analysis of the product stream from a catalytic testing unit. This technique is applied for the study of the catalytic reaction of methanol-to-olefins (MTO) conversion. For this method, the time distance between two measurements is chosen so that the chromatograms but not the peaks themselves are superimposed. In this way, stacked chromatograms are generated in which the components from successively injected samples elute baseline separated next to each other from the column. The peaks from different samples are interlaced, and for this reason, the method is referred to as time-division multiplexing gas chromatography (td-mpGC). The peaks are analyzed by direct peak integration not requiring a Hadamard transformation for deconvolution of the raw data as usual for many mpGC applications. Therefore, the sample can be injected equidistantly. The integrated peaks have to be allocated to the correct retention times. The time distance between two measurements for studying the reaction and regeneration cycles of MTO catalysts is 4.3 min and 38 s, respectively. Column switching techniques such as back-flush and heart-cut are introduced as general tools for multiplexing gas chromatography.

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Thermal decomposition of aliphatic nylons

Levchik¹,

Weil²,

Lewin³

1999

Polym. Int.

367

254

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An overview of the literature together with selected authors' data on thermal and thermo‐oxidative decomposition of commercial aliphatic nylons (nylon 6, nylon 7, nylon 11, nylon 12, nylon 6.6, nylon 6.10, nylon 6.12) is presented. Despite the high level of research activity and the large number of publications in the field, there is no generally accepted mechanism for the thermal decomposition of aliphatic nylons. Polylactams (nylon 6, nylon 11 and nylon 12) tend to re‐equilibrate to monomeric or oligomeric cyclic products. Diacid–diamine type nylons (nylon 6.6, nylon 6.10 and nylon 6.12) produce mostly linear or cyclic oligomeric fragments and monomeric units. Because of the tendency of adipic acid to fragment with elimination of CO and H2O and to undergo cyclization, significant amounts of secondary products from nylon 6.6 are reported in some papers. Many authors have shown that the primary polyamide chain scission occurs either at the peptide C(O)NH or at adjacent bonds, most probably at the alkyl–amide NHCH2 bond which is relatively the weakest in the aliphatic chain. Hydrolysis, homolytic scission, intramolecular CH transfer and cis‐elimination (a particular case of CH transfer) are all suggested as possible primary chain‐scission mechanisms. There are no convincing results reported which tend to generally support one of these mechanisms relative to the others; rather, it seems that the contribution of each mechanism depends on experimental conditions. This conclusion is also supported by the wide spread of kinetic parameters measured under the different experimental conditions. More uniform results are observed in the literature regarding the mechanism of thermo‐oxidative decomposition of aliphatic nylons. Most authors agree that oxygen first attacks the N‐vicinal methylene group, which is followed by the scission of alkyl–amide NC or vicinal CC bond. Alternatively, it is suggested that any methylene group which is β‐positioned to the amide group methylene can be initially oxidized. There are few mechanisms in the literature which explain discoloration (yellowing) of nylons. UV/visible active chromophores are attributed either to pyrrole type structures, to conjugated acylamides or to conjugated azomethines. Some secondary reactions occurring during the thermal or thermo‐oxidative decomposition lead to crosslinking of nylons. Nylon 6.6 crosslinks relatively easily, especially in the presence of air, whereas nylon 11 and nylon 12 crosslink very little. Strong mineral acids, strong bases, and some oxides or salts of transition metals catalyse the thermal decomposition of nylons, but minimize crosslinking. In contrast, many fire retardant additives promote secondary reactions, crosslinking and charring of aliphatic nylons. © 1999 Society of Chemical Industry

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Study of the thermal decomposition of polymers by on-line cross-correlation gas chromatography

Cited by 9 publications

References 3 publications

Effect of Porous and Nonporous Carbonaceous Substrates on Polystyrene Thermal Degradation during Fast CO₂ Laser Heating

Effect of Porous and Nonporous Carbonaceous Substrates on Polystyrene Thermal Degradation during Fast CO₂ Laser Heating

Online High Throughput Measurements for Fast Catalytic Reactions Using Time-Division Multiplexing Gas Chromatography

Thermal decomposition of aliphatic nylons

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Study of the thermal decomposition of polymers by on-line cross-correlation gas chromatography

Cited by 9 publications

References 3 publications

Effect of Porous and Nonporous Carbonaceous Substrates on Polystyrene Thermal Degradation during Fast CO2 Laser Heating

Effect of Porous and Nonporous Carbonaceous Substrates on Polystyrene Thermal Degradation during Fast CO2 Laser Heating

Online High Throughput Measurements for Fast Catalytic Reactions Using Time-Division Multiplexing Gas Chromatography

Thermal decomposition of aliphatic nylons

Contact Info

Product

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About

Effect of Porous and Nonporous Carbonaceous Substrates on Polystyrene Thermal Degradation during Fast CO₂ Laser Heating

Effect of Porous and Nonporous Carbonaceous Substrates on Polystyrene Thermal Degradation during Fast CO₂ Laser Heating