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Understanding Different Types of Pyrolyzers

Did you know there are different types of pyrolyzers?

In fact, there are three different types of pyrolyzers that are commercially available: filament, Curie-point, and micro-furnace. Flash pyrolysis can be done by all types of pyrolyzers. However, the pyrolysis temperature cannot be tuned continuously by a Curie-point pyrolyzer, and it cannot be applicable, in principle, to the evolved gas analysis (EGA). The analysis of volatile and semi-volatile compounds in a sample cannot be done by a filament pyrolyzer, because it requires pre-heating of a sample before pyrolysis to avoid condensation of pyrolyzates with a high-boiling point. Both flash pyrolysis and EGA can be done effectively by a temperature-programmable microfurnace pyrolyzer since it is directly connected to the GC without any dead volume and cold spots, and cryo-trap is not always necessary in the daily analysis. To better understand the different types of pyrolyzers, practical specifications of these pyrolyzers are given below.

 

Fig 1 Schematic Diagrams of Different Pyrolyzers

 

Filament Type Pyrolyzer

The first type of pyrolyzer we’ll cover is the Filament Type Pyrolyzer. Filament type pyrolyzers heat a sample tube with a filament.

Filament pyrolyzer suffers from poor temperature accuracy and poor reproducibility because of non-uniform heating. Sample placement and heat-transfer variations affect the temperature of the sample (depending on where the sample sits in relation to platinum wire coils and on sample contact). The filament temperature is estimated from the electrical properties of the wire, but the temperature of the sample is not actually measured as it changes over time. The sample must be pre-heated prior to the analysis in the heating manifold to avoid the condensation of pyrolyzates with a high boiling point. This preheating step causes denaturation, degradation, or thermosetting of samples and evaporation of volatile and semi-volatile compounds in samples.

Some filament pyrolysis systems also use a 2-step pyrolysis process in which some of the pyrolyzates are collected first off-line on a focusing trap. Then the switching valve sequentially sends the pyrolyzates from the focusing trap into the GC/MS. The pyrolysis indirectly places the pyrolyzates on the GC column in a two-step and non-continuous process. Polar and heavy compounds stick irreversibly in the focusing trap but are not removed for analysis similar to a cold spot.

 

Fig. 2 Thermal Profile of a Filament Pyrolyzer

 

Curie-Point Pyrolyzer

The Curie-point pyrolyzer can indeed have a high heating temperature accuracy; however, the heating temperature depends on the alloy composition of the sample foil. It is therefore impossible to continuously raise the heating temperature of the Curie-point device to allow for the EGA techniques. The pre-heating of the heater manifold is necessary, similar to the filament pyrolyzer. Moreover, the results vary depending on how the sample is wrapped with the alloy foil, and this leads to worse reproducibility. Despite the power of modern analytical instruments techniques of analysis such as gas chromatography and mass spectrometry one of the most important challenges remains that of sample preparation – especially far non-volatile, insoluble materials and chemicals. Sample preparation can require a lot of time and expertise particularly when dealing with small sample amounts

 

Fig. 3 Thermal Profile of a Micro-Furnace Pyrolyzer

 

Micro-Furnace Pyrolyzer

Micro-furnace allows a full range EGA to obtain a thermal profile of an unknown sample for light compounds, volatiles, and additives as well as oligomers, heavy, and polymeric compounds. The EGA experiments can be performed from 40°C to maximum temperature (1050°C) and correlate results to well-established TGA techniques throughout the entire temperature range of the experiment. This capability is critical for evaluation of unknown samples.

This technology directly deposits all pyrolyzates on-column in a single step process for a continuous-mode analysis. The sample is placed in an inert deactivated cup held at the ambient temperature in helium and is not subjected to heat prior to the analysis. The micro-furnace is preheated to the desired temperature which is precisely measured with a thermal couple sensor near the sample. The sample cup then drops into the quartz pyrolysis tube where the sample is quickly and reproducibly pyrolyzed.  The pyrolyzates are then continuously swept onto the GC analytical column for separation and detection by MS or any other detector. The continuous-mode process of the micro-furnace allows low and high molecular-weight as well as polar compounds to be detected and analyzed. The absence of any transfer line is also critical in the ability of this device to detect heavy and polar pyrolyzates and additives.

The micro-furnace technology guarantees reproducibility and accuracy of the temperature with ±0.1°C. Every facet of the system is designed to ensure reliability and data quality. All wetted surfaces are quartz or temperature stable deactivated; there is no transfer line with cold spots and no cross contamination.

What sets Frontier Pyrolyzers apart from different types of pyrolyzers?

The Frontier EGA/PY-3030D Multi-Shot Pyrolyzer is a sophisticated and powerful instrument based on a micro-furnace design. It features high performance and ease of use, from the heating furnace to the control software. The Frontier EGA/PY-3030D is a versatile multi-shot pyrolyzer that offers temperature programmability from ambient (+10ᵒC) to 1050ᵒC with precise temperature control (+/- 0.1ᵒC) of the ceramic micro furnace. This allows the user to analyze materials using a variety of techniques for greater flexibility.

  • With a direct connection to the GC injection port (no transfer line or switching valves) and performing a continuous-mode pyrolysis, all pyrolyzates are continuously and directly transferred in a single step process into GC as they are generated. Heavy and polar compounds are directly placed on-column and light compounds are never lost.
  • The sample, placed in an inert sample cup, is held in an ambient temperature and is not exposed to any heat prior to the analysis. Therefore, there is no chance of evaporation, degradation, or thermosetting before the analysis. Also the sample is purged of oxygen before heated so that there are no oxidation reactions.
  • Critical for evaluation of unknown samples, the Frontier system can perform EGA experiments from 40°C to maximum temperature (1050°C) and correlate results to well-established TGA(thermal gravimetric analysis) techniques throughout the entire temperature range of the experiment.
  • The Frontier pyrolyzer controls actual sample temperatures to within a 0.1°C set point of the pyrolysis furnace. Other pyrolysis devices only control the temperature of a heating element, not the actual sample temperature.

It is important to note that based on actual bond energy strengths in polymers and materials, all organic materials will pyrolyze prior to a temperature of approximately 700 °C. Therefore, the only reason to set an initial pyrolysis temperature in excess of 700 °C is because the actual sample temperature in the pyrolyzer is not accurate. Literature indicating pyrolysis at 1200 or 1300 °C is either unnecessary, over pyrolysis, or indicates poor actual sample temperature control in the particular pyrolysis device.

 

Learn more about the Frontier micro-furnace pyrolyzer and request pricing information.

References:

  1. This technical note was developed by Frontier Laboratories Ltd. 4-16-20 Saikon, Koriyama, Fukushima, 963-8862 JAPAN.
    http://www.frontier-lab.com/.
  2. “Analysis of Curie-Point-Pyrolysis Coupled with Gas Chromatography MS”, Envirotech Online, April 2018, https://www.envirotech-online.com/news/environmental-laboratory/7/gsg-analytical-instruments/analysis-by-curie-point-pyrolysis-coupled-with-gas-chromatography-ms/2545.
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