Other pyrolyzer types

Besides the previously described pyrolyzer types, some other pyrolyzers have been constructed and reported in literature [14, 35, 36], Some are based on variations of typical pyrolyzer systems. One such system uses a microfurnace pyrolyzer with the capability to hydrogenate the pyrolysis products. For this purpose, the system uses hydrogen carrier, and, in line with the microfurnace, it has a catalyst column containing a 

A different system utilizes as a source of heat an electric arc [50], but limited applications were reported for it, and also an infrared pyrolyzer is manufactured [49]. Other techniques, such as photolysis [38], were utilized for breaking down polymers for further analysis. However, these cannot be considered pyrolytic procedures. A theoretical approach has been developed [38] to compare mass spectrometric, thermolytic and photolytic fragmentation reactions. 

One other pyrolytic technique used for polymer analysis is pyrolysis-fractography [40]. 

Comparisons between the results obtained using different pyrolyzers are not uncommon in literature [14, 41-43]. These comparisons have two objectives to assess the quality of the analytical results (reproducibility, sensitivity, etc.) of a certain type of pyrolyzer and to indicate how the results of one pyrolyzer can be compared to those of another type. 

The comparison is not always straightforward because the analytical instrument at the end of the pyrolyzer may play an important role regarding the quality of the data. 

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At the other extreme, the most stable derivatives of the B2X4 type appear to be the tetrakis(dialkylamino) compounds. Thus, tetrakis(dimethylamino)-diborane(4) is stable at its boiling point of 206° C 17). The compound decomposes at 300° C to form bis(dimethylamino)borane and involatile residues containing B—C bonds. It is reported that tetra(A -methylanilino)-borane(4) is pyrolyzed at 300° C by a different mechanism to yield N-methylaniline 18). 

In 1969 Willcott and Cargle reported experiments in which they prepared and pyrolyzed l-(2-deuteriovinyl)cyclopropane-trans, trans-2,3-d2 (see Figure 15). They found that the other stereoisomers of this compound were formed at equal rates, consistent with the expectation for a Benson-type biradical sitting in a potential energy well of substantial depth. 

Like other pyrolysis oil processes. Biocarbons Corporation s reactor produces a large number of oil compounds. For mixed hardwood (maple, birch and beech) pyrolyzed at typical operating conditions, 69 peaks were found by GC/MS analysis. Of these, the 14 peaks present at above 2 mole percent, represented 45 mole percent of the product that came through the GC. The 27 peaks between 1 and 2 mole percent, represented an additional 37 mole percent of the product. These compounds that were identified are listed in Table 1, in order of appearance (time). Several of the 4-position groups could also be occurring at the 3 position. All are reactable to make a phenol-forma Idehvde type adhesive. Pyrolysis oil from pine that was nude at the same operating condition (but has not yet been tested for adhesive use) had essentially the same compounds present at >1 mole percent, but at different relative concentrations. Some lower concentration compounds such as fatty acids are only produced from pine, but these compounds are specific to softwoods and the composition of softwoods. A comparison between the mixed hardwoods and pine products is shown in Table 2. 

The true temperature of a sample heated using a filament pyrolyzer can be quite different from the above profile temperature, significantly lower temperatures being recorded inside the samples [4]. In order to obtain a correct Teq, modern equipment uses a feedback controlled temperature system (see e g. [5] for a more detailed description of this type of pyrolyzer). Several other procedures for a precise temperature control of the filament are available, such as the use of optical pyrometry or thermocouples [6, 7], Special pyrolysis systems that allow programmed heated rates at different time intervals also are available [8]. 

There are several advantages of the resistively heated filament pyrolyzers compared to other types. They can achieve very short TRT values, the temperature range is large, and Teq can be set at any desired value in this range. Several commercially available instruments are capable of performing programmed pyrolysis, and autosampling capability is also available (such as the CDS AS-2500). 

A factor that must be considered with furnace pyrolyzers as well as with the other types of pyrolyzers is the achieving of short TRT values. A slow sample introduction in the hot zone of the furnace will end in a long TRT. A poor contact between the sample and the hot source may also lead to long TRT, most of the heat being transferred by radiation and convection and not by conduction. However, fairly short TRTs in furnace pyrolyzers were reported in literature [14, 15]. Also, in furnace pyrolyzers it is more common to see differences in the temperature between the furnace and the sample. Due to the poor contact between the sample and the hot source, the sample may reach a lower actual temperature than the temperature of the furnace wall. This may be the explanation why there were reported variations in the pyrolysis products in microfurnace systems as compared to the results obtained in inductively or filament heated pyrolyzers [16,17]. 

Another typical property of the laser pyrolysis is that it can achieve very short TRT times and also very short cooling times, in the range of 100 to 300 jis. This will contribute to the uniqueness of the degradation conditions for the laser pyrolysis, which are rather different from the other types. In addition to this, the capability to pyrolyze only a very small area of the sample is characteristic for most laser pyrolyzers. This directional nature can be of exceptional utility when combined with the microscopic inspection of a particular sample. Inclusions and inhomogeneities in the samples, etc. can be analyzed successfully using this technique. 

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