High frequency pyrolysis

Vapor phase pyrolysis of 2-aminobiphenyl in chloroform at 350°C produces carbazole,as does heating at 500-800°C in a high-frequency glow discharge at 25-34 A small amount (11%) of carbazole 280 was formed during the reaction of 281 with copper-potassium carbonate and 1-iodo-naphthalene in nitrobenzene. ... 

Curie-point pyrolysis employs high-frequency (HF) inductive heating of a ferromagnetic wire (d 1 mm). A diagram of a Curie-point pyrolyzer designed for Py-GC is shown in Fig. 4.7.2. 

The heating time of the wire is usually from 1 sec [63] to a few tenths of a second [61, 64], or even two or three hundredths of a second, depending on the pyrolysis conditions for the Curie-point pyrolyser. The kinetics of heating or cooling of the wire depends on its diameter and the power output of the high frequency oscillator [57, 65, 66] (see Fig. 3.4D [65] and E [57]). 

In a Curie-point pyrolyzer, an oscillating current is induced into the pyrolysis filament by means of a high-frequency coil. It is essential that this induction coil be powerful enough to permit heating the wire to its specific Curie-point temperature quickly. In such systems, the filament temperature is said to be self-limiting, since the final or pyrolysis temperature is selected by the composition of the wire itself, and not by some selection made in the electronics of the instrument. Properly powered, a Curie-point system can heat a filament to pyrolysis temperature in milliseconds. Providing that wires of the same alloy composition are used each time, the final temperature is well characterized and reproducible. 

The Curie-point pyrolyzer uses the Curie points of ferromagnetic sample holders to achieve precisely controlled temperatures when the holder containing the sample is subjected to high-frequency induction heating. Foils of various ferromagnetic materials enable the analyst to select pyrolysis temperatures from 150 to 1000°C. 

The equipment used in the spray-pyrolysis technique consists basically of an atomizer and a temperature controller. There are several types of atomizers. The most common ones are compressed air atomizers [2] (when the spray of the precursor solution is produced by a jet of air), electric field atomizers [3] (when the spray of the precursor solution is produced by an electric field) and ultrasound atomizers [4] (when the spray of the precursor solution is produced through high frequencies). 

Compared to those just described, our investigations utilizing high frequency gas discharge [30] had the advantage that no contact is made between reactant and electrodes, and that reactions induced by this kind of energy transfer proceed at temperatures below 200 °C, whereas temperatures of the order of 600-700 °C are required for pyrolysis [31]. In order to sustain this plasma state, the pressure in the system was not permitted to exceed 10 mm Hg, while our pyrolysis reactions were carried out just below atmospheric pressure. 

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