Pyrolysis atmosphere

Edinger et al. [4] studied rapid decomposition of coal in a transport-type reactor, with residence times 8-40 ms (COED-FMC). They found that pyrolysis atmosphere affects the products. Coal particles never reached the reactor temperature, even at the lowest particle transfer rate 59% of the coal volatilized when the reactor temperature was 1300°C. This is far above the 41% indicated by the ASTM volatile-matter determination. 

The pyrolysis of polysilanes and polycarbosilanes is usually carried out using inert gas (e.g., argon) as pyrolysis atmosphere. A general problem associated with the pyrolytic formation of carbides is the desired stoichiometry of the calcined products in contrast to nitrides, excess carbon carmot be evaporated during calcining it may therefore contaminate the powders obtained as an elemental impurity and thus influences the physical, especially mechanical and electrical, properties of the sintered ceramic bodies. The volatiles evaporated during pyrolytic treatment of carbosilanes to form a network structure are H2 and CH4, and they depend on the structure of the polycarbosilane used (Fig. 2). 

Tripathi, A. Maswadeh, W.M. Snyder, A.P., Optimization of quartz tube pyrolysis atmospheric-pressure ionization mass spectrometry for the generation of bacterial hiomwk xs. Rapid Commun. Mass Spectrom. 2001, 18, 1672-1680. 

Kiyono M, Williams PJ, Koros WJ. Effect of pyrolysis atmosphere on separation performance of carbon molecular sieve membranes. 7 Afcmbr Sci 2010 359 2-10. 

Snyder, P.A., Kremer, J.H., Liebman, S.A., Schroeder, M.A. and Fifer, R.A. (1989) Characterization of Cyclotrimethylene trinitramine (RDX) by N,H Isotope Analysis with Pyrolysis-Atmospheric Pressure Ionization Tandem Mass Spectroscopy Organic Mass Spectrometry 24, 15-21. 

As for the effect of pyrolysis atmosphere on the conversion of polysiloxanes, vacuum was preferred to Ar atmosphere to develop the correct composition and microstructure in the case of preparation of oxycarbide coating films (Colombo, 1994). 

Snyder AP (1990) Acrylic compound characterization by oxidative pyrolysis, atmospheric pressure chemical ionization-tandem mass spectrometry. Journal of Analytical and Applied Pyrolysis 17 127-141. 

Suda and Haraya (1997a) have formed flat CMS films from Kapton polyimide by pyrolysis at 1000°C in argon and in vacuum. The results from this study have shown that there was little difference in the permeation properties between membranes formed in argon purge and vacuum. Therefore, it is likely that the effect of pyrolysis atmosphere may be related to the properties of the precursor and the temperamrc profile used during pyrolysis. 

Organic compounds are a major constituent of the FPM at all sites. The major sources of OC are combustion and atmospheric reactions involving gaseous VOCs. As is the case with VOCs, there are hundreds of different OC compounds in the atmosphere. A minor but ubiquitous aerosol constituent is elemental carbon. EC is the nonorganic, black constituent of soot. Combustion and pyrolysis are the only processes that produce EC, and diesel engines and wood burning are the most significant sources. 

Pyrolysis of chlorodifluoromethane is a noncatalytic gas-phase reaction carried out in a flow reactor at atmospheric or sub atmospheric pressure yields can be as high as 95% at 590—900°C. The economics of monomer production is highly dependent on the yields of this process. A significant amount of hydrogen chloride waste product is generated during the formation of the carbon—fluorine bonds. 

In this pyrolysis, sub atmospheric partial pressures are achieved by employing a diluent such as steam. Because of the corrosive nature of the acids (HE and HCl) formed, the reactor design should include a platinum-lined tubular reactor made of nickel to allow atmospheric pressure reactions to be mn in the presence of a diluent. Because the pyrolysate contains numerous by-products that adversely affect polymerization, the TFE must be purified. Refinement of TFE is an extremely complex process, which contributes to the high cost of the monomer. Inhibitors are added to the purified monomer to avoid polymerization during storage terpenes such as t7-limonene and terpene B are effective (10). 

A report on the continuous flash pyrolysis of biomass at atmospheric pressure to produce Hquids iadicates that pyrolysis temperatures must be optimized to maximize Hquid yields (36). It has been found that a sharp maximum ia the Hquid yields vs temperature curves exist and that the yields drop off sharply on both sides of this maximum. Pure ceUulose has been found to have an optimum temperature for Hquids at 500°C, while the wheat straw and wood species tested have optimum temperatures at 600°C and 500°C, respectively. Organic Hquid yields were of the order of 65 wt % of the dry biomass fed, but contained relatively large quantities of organic acids. 

Coal pyrolysis has been studied at both reduced and elevated pressures (136), and in the presence of a variety of agents and atmospheres (137). Although important to the study of coal stmcture and reactions, coal pyrolysis, as a means to generate Hquids, has proved to have limited commercial value. 

Atmospheric Conditions. In addition to complete combustion, wastes may be destroyed by treatment at high temperatures either without oxygen (qv) (pyrolysis), usiag limited oxygea (partial combustioa), or ia reactive atmospheres (gasiftcatioa), such as those containing steam (qv), hydrogea (qv), or carboa dioxide (qv). 

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. 

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