Inert atmosphere pyrolysis

Proponents of the equivalence of inert-atmosphere pyrolysis of a tobacco component and its behavior in a burning cigarette during the smoking process misinterpreted one set of data and disregarded another ... 

Elemental and thermogravimetric analysis confirmed the high metal content of the material (polymer 2c is 35 wt. % Sn). In fact, an essentially quantitative ceramic yield to Sn metal is observed in its inert atmosphere pyrolysis (N2). In turn, differential scanning calorimetry reveals that the polymer 2c (a viscous liquid at room temperature) is completely amorphous (no melting transition is observed in the range -100 to +50 °C are observed) with a Tg of ca. -98 °C [22,23]. 

Other techniques include oxidative, steam atmosphere (33), and molten salt (34) pyrolyses. In a partial-air atmosphere, mbber pyrolysis is an exothermic reaction. The reaction rate and ratio of pyrolytic filler to ok products are controlled by the oxygen flow rate. Pyrolysis in a steam atmosphere gives a cleaner char with a greater surface area than char pyroly2ed in an inert atmosphere however, the physical properties of the cured compounded mbber are inferior. Because of the greater surface area, this pyrolytic filler could be used as activated carbon, but production costs are prohibitive. Molten salt baths produce pyroly2ed char and ok products from tine chips. The product characteristics and quantities depend on the salt used. Recovery of char from the molten salt is difficult. 

Pyrolysis of Re2(CO)2Q at 400°C in vacuo or in an inert atmosphere has been used to obtain pure rhenium metal. 

Mechanism [5] was based on the results obtained from multi-step sequential pyrolysis experiments in an inert atmosphere (23). This mechanism [5] differs from [3], primarily in that [5] was proposed to be surface catalytic in nature, and that the reaction between the oxide particle surface and the organohalogen was considered only as the first step, initiating the process leading to the eventual formation of volatile antimony species. 

Pyrolysis has a long history in the upgrading of biomass. The dry distillation of hardwood was applied in the early 1990s to produce organic intermediates (methanol and acetic acid), charcoal and fuel gas [3]. Today s processes can be tuned to form char, oil and/or gas, all depending on the temperature and reaction time, from 300 °C and hours, to 400-500 °C and seconds-minutes, to >700 °C and a fraction of a second [3, 19, 23, 24], The process is typically carried out under inert atmosphere. We illustrate the basic chemistry of pyrolysis by focusing on the conversion of the carbohydrate components (Fig. 2.4). The reaction of the lignin will not be covered here but should obviously be considered in a real process. Interested readers could consult the literature, e.g., [25]. Pyrolysis is discussed in more details elsewhere in this book [26],... 

The resorcinol-formaldehyde polymers have been used to prepare highly porous carbon materials, by controlled pyrolysis in an inert atmosphere [144,154], The microstructure of the carbon is an exact copy of the porous polymer precursor. Poly(methacrylonitrile) (PM AN) PolyHIPE polymers have also been used for this purpose. These monolithic, highly porous carbons are potentially useful in electrochemical applications, particularly re-chargeable batteries and super-capacitors. The RF materials, with their very high surface areas, are particularly attractive for the latter systems. 

Pyrolysis processes simply cook the feedstock in an essentially inert atmosphere at relatively low temperatures (500°to 700°C) hydropyrolysis operates under similar conditions, but in a reducing atmosphere. 

A manufactured fiber made by pyrolysis of sin organic precursor— rayon, polyacrylonitrile, or pitch in an inert atmosphere. 

A variety of other ceramics are prepared by pyrolysis of preceramic polymers.32,38 Some examples are silicon carbide, SC, tungsten carbide, WC, aluminum nitride, AIN, and titanium nitride, TiN. In some cases, these materials are obtained by simple pyrolysis in an inert atmosphere or under vacuum. In other cases a reactive atmosphere such as ammonia is needed to introduce some of the atoms required in the final product. Additional details are given in Chapter 9. 

The third approach, this one by Seyferth, is based on the coordinative linkage of borane cage structures by diamines or phosphines to form soluble oligomers (9.21), followed by pyrolysis (reaction (20)).66-68 Pyrolysis in an inert atmosphere gives a 70-90% ceramic yield of a black boron carbonitride, but pyrolysis in ammonia yields white BN in 70% yield. A disadvantage of a process based on a borane starting material is its high cost. 

The total volatile matter yield, and hence the yield of tar plus light oils, is proportional to the hydrogen-to-carbon ratio in the raw material. On the other hand, the chemically formed water vapor that distills off during pyrolysis in an inert atmosphere is proportional to the oxygen-to-carbon ratio. The yields and product distributions also depend on the rate of pyrolysis. 

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