Pyrolysis properties

The pyrolysis properties of four model compounds were examined. Their molecular structures are shown in Table II. The three and four-ring molecules, containing a benzo [b] thiophenic unit were synthesized by Dr. Cagniant (L.S.C.O., Metz University). A polycyclohexanesulfide is an aliphatic sulfide synthesized by Dr. N. Spassky (Laboratory of Macromolecular Chemistry, Paris VI University). Polymeric aromatic sulfide was represented by a polybenzosulfide provided by Philips Petroleum. 

The results presented here are unique in that they are from lH NMR measurements made under the non-equilibrium conditions pertaining to temperature controlled pyrolitic decomposition of the shales. We have established experimental techniques that ensure good reproducibility of the changes manifest in these dynamically recorded 1h NMR solid echo signals. By this technique of -H NMR thermal analysis it is possible to obtain a set of data characterizing the pyrolysis properties of the shale. 

From Zirconium Isopropoxide and Yttrium Acetylacetonate by Flame Pyrolysis Properties 9 mol% yttria, BET specific surface area 68 rnVg [2206]. 

The methodology of LMSMC can be used to reasonably describe the pyrolysis property of coal, and reflect the pyrolysis process of coal aiming at a certain property. 

Catalytic dewaxing Catalytic hydrogenation Catalytic properties Catalytic pyrolysis Catalytic reduction Catalytic reforming... 

Analytical investigations may be undertaken to identify the presence of an ABS polymer, characterize the polymer, or identify nonpolymeric ingredients. Fourier transform infrared (ftir) spectroscopy is the method of choice to identify the presence of an ABS polymer and determine the acrylonitrile—butadiene—styrene ratio of the composite polymer (89,90). Confirmation of the presence of mbber domains is achieved by electron microscopy. Comparison with available physical property data serves to increase confidence in the identification or indicate the presence of unexpected stmctural features. Identification of ABS via pyrolysis gas chromatography (91) and dsc ((92) has also been reported. 

Although NF is an amine, it exhibits virtually no basic properties and is not protonated by the HSO F—SbF —SO superacid medium at 20°C (19). Commercial scmbbing systems for unwanted NF are available (20) and work on the principle of pyrolysis of the NF over reactive substrates at high temperatures. 

As a result of the development of electronic applications for NF, higher purities of NF have been required, and considerable work has been done to improve the existing manufacturing and purification processes (29). N2F2 is removed by pyrolysis over heated metal (30) or metal fluoride (31). This purification step is carried out at temperatures between 200—300°C which is below the temperature at which NF is converted to N2F4. Moisture, N2O, and CO2 are removed by adsorption on 2eohtes (29,32). The removal of CF from NF, a particularly difficult separation owing to the similar physical and chemical properties of these two compounds, has been described (33,34). 

Chemical Properties. The kinetics of decomposition of OF2 by pyrolysis in a shock tube are different, as a result of surface effects, from those obtained by conventional decomposition studies. Dry OF2 is stable up to 250°C (22). 

Vlayl fluoride [75-02-5] (VF) (fluoroethene) is a colorless gas at ambient conditions. It was first prepared by reaction of l,l-difluoro-2-bromoethane [359-07-9] with ziac (1). Most approaches to vinyl fluoride synthesis have employed reactions of acetylene [74-86-2] with hydrogen fluoride (HF) either directly (2—5) or utilizing catalysts (3,6—10). Other routes have iavolved ethylene [74-85-1] and HF (11), pyrolysis of 1,1-difluoroethane [624-72-6] (12,13) and fluorochloroethanes (14—18), reaction of 1,1-difluoroethane with acetylene (19,20), and halogen exchange of vinyl chloride [75-01-4] with HF (21—23). Physical properties of vinyl fluoride are given ia Table 1. 

Table 17. Properties and Analysis of Liquid Fuel and No. 6 Fuel Oil Liquid fuel produced by flash pyrolysis using char recycle (Fig. 10).

Properties. A high volatile western Kentucky bituminous coal, the tar yield of which by Fischer assay was ca 16%, gave a tar yield of ca 26% at a pyrolysis temperature of 537°C (146—148). Tar yield peaked at ca 35% at 577°C and dropped off to 22% at 617°C. The char heating value is essentially equal to that of the starting coal, and the tar has a lower hydrogen content than other pyrolysis tars. The product char is not suitable for direct combustion because of its 2.6% sulfur content. 

PhenoHc and furfuryl alcohol resins have a high char strength and penetrate into the fibrous core of the fiber stmcture. The phenoHc resins are low viscosity resoles some have been neutralized and have the salt removed. An autoclave is used to apply the vacuum and pressure required for good impregnation and sufficient heat for a resin cure, eg, at 180°C. The slow pyrolysis of the part foUows temperatures of 730—1000°C are recommended for the best properties. On occasion, temperatures up to 1260°C are used and constant weight is possible even up to 2760°C (93). 

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. 

Carbon Composites. Cermet friction materials tend to be heavy, thus making the brake system less energy-efficient. Compared with cermets, carbon (or graphite) is a thermally stable material of low density and reasonably high specific heat. A combination of these properties makes carbon attractive as a brake material and several companies are manufacturing carbon fiber—reinforced carbon-matrix composites, which ate used primarily for aircraft brakes and race cats (16). Carbon composites usually consist of three types of carbon carbon in the fibrous form (see Carbon fibers), carbon resulting from the controlled pyrolysis of the resin (usually phenoHc-based), and carbon from chemical vapor deposition (CVD) filling the pores (16). 

Sihcon carbide is also a prime candidate material for high temperature fibers (qv). These fibers are produced by three main approaches polymer pyrolysis, chemical vapor deposition (CVD), and sintering. Whereas fiber from the former two approaches are already available as commercial products, the sintered SiC fiber is still under development. Because of its relatively simple process, the sintered a-SiC fiber approach offers the potential of high performance and extreme temperature stabiUty at a relatively low cost. A comparison of the manufacturing methods and properties of various SiC fibers is presented in Table 4 (121,122). 

Physical properties of pentachloroethane are Hsted in Table 10. The kinetics and mechanism of the pyrolysis of pentachloroethane in the temperature ranges of 407—430°C and 547—592°C have been studied (133—135). Tetrachloroethylene and hydrogen chloride are the two primary pyrolysis products, showing that dehydrochlorination is the primary reaction. 

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