Oxidative pyrolyses

Reaction Conditions. Each of the four SRC II distillation cuts was pyrolyzed at 500, 700, 900, and 1100°C at approximately 7 seconds residence time in helium. The fuel vapor concentration averaged 1.4 volume percent. Oxidative pyrolyses were done at the same temperatures and residence times using MD-4 at average stoichiometric oxygen concentrations of 6.6, 20.4, and 73.0 percent. The range of concentrations at each level was large. 

The orientational behaviour of amine oxide pyrolyses has been adequately summarised by Cope and TrumbulE . As for the acetate decompositions, orientation in the simple alkyl systems is controlled primarily by statistical factors but departure from this influence is noted with the bulky r-butyl substituent and the acid strengthening beta phenyl substituents Eclipsing effects are greater in the planar five-membered transition states than in the puckered six systems and this is borne out by the greater preference for trans-olefin formation from amine oxides than esters and xanthates (152, cf. 149). 

Ube Industries has announced the development of a near-stoichiometric fibre made from a polycarbosilane cross-linked by an aluminium compound. The precursor fibre is cured by oxidation, pyrolysed in two steps first to allow the outgassing of CO and then sintered at a temperature up to around 1800°C. 

Oxidative Pyrolyses of Selected Hydrocarbons Using the Wall-less Reactor... 

The homogeneous high temperature pyrolysis of hydrocarbons normally gives similar products in either the presence or absence of limited amounts of oxygen. The effect of oxygen is often to increase the rate of reaction and to vary product ratios. It is the purpose of this paper to examine the oxidative pyrolyses of a series of hydrocarbons under surface free conditions. Achievement of a totally surface free environment has been made possible by the development of the wall-less reactor(lj 2). 

Since the rates of oxidative pyrolyses may be strongly affected by surfaces(2,1,4, a study of the absolute effects of surface is also included. Surface effects are evaluated by comparing reactions done in a homogeneous environment to those with a surface inserted into the reactor. 

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. 

Pyrolyses of formates, oxalates and mellitates yield CO and C02 (H2, H20 etc.) as the predominant volatile products and metal or oxide as residue. It is sometimes possible to predict the initial compositions from thermodynamic considerations [94], though secondary reactions, perhaps catalyzed by the solids present, may result in a final product mixture that is very different. The complex mixtures of products (hydrocarbons, aldehydes, ketones, acids and acid anhydrides) given [1109] by reactants containing larger organic groupings makes the collection of meaningful kinetic data more difficult, and this is one reason why there are relatively few rate studies available for the decompositions of these substances. 

In this chapter, we discuss free-radical substitution reactions. Free-radical additions to unsaturated compounds and rearrangements are discussed in Chapters 15 and 18, respectively. In addition, many of the oxidation-reduction reactions considered in Chapter 19 involve free-radical mechanisms. Several important types of free-radical reactions do not usually lead to reasonable yields of pure products and are not generally treated in this book. Among these are polymerizations and high-temperature pyrolyses. 

FIGURE 16.13 Mass spectrum of the isolated compound 24-norursa-3,12-dien-ll-one (compound 11) (Rf 0.55), an oxidized product from the pyrolysate of B. serrata. 

To perform optimally, the char, or similar barrier should be continuous, coherent, adherent and oxidation-resistant. It should be a good thermal insulator (which implies closed-cell character) and it should have low permeability to gases, to liquid pyrolysate, and to molten polymer. Moreover, the char must be formed in a timely manner before the polymer is extensively pyrolyzed. 

Die Photolyse von 4-Azido-3-phenyl-furazan-2-oxid in Dichlormethan/Ethanol fiihrt in einer stereoselektiven Reaktion zum (thermodynamisch weniger stabilen) (E)-2-Hydroximino-2-phenyl-acetonitril, bei der Pyrolyse (in Pentanol) entstehen sowohl das (E)- als auch das (Z)-Oxim426. 

The hydroxy-alkoxides condense to form a polymeric gel with metal-oxygen-metal links. Lithium niobate is then formed when the gel is heated. Heating removes any remaining ethanol and any water formed during the condensation. The remaining ethyl groups are pyrolysed (i.e., oxidised to carbon dioxide and water) leaving the oxides. 

In the first step the formation of 5-phenyl-2-TMS-l, 2,3,4,-tetrazole (374) occurs which can either be hydrolyzed to 5-phenyl-l,2,3,4-tetrazole (375) or pyrolysed to give a N-TMS-benzaldehydehydrazonium compound (376). 376 can furthermore either dimerize to form 3,6-diphenyl-l,2,5-bis(TMS)-2,5-dihydro-l,2,4,5-tetrazine (377) and after subsequent hydrolysis and oxidation 3,6-diphenyl-l,2,4,5-tetrazine (3 79) or on the other hand react with a further equivalent 373 yielding in the last step 3,5-diphenyl-l, 2,4-triazole (381)214 (Scheme 55). 

Commercially available non-oxide ceramic reinforcements are in three categories continuous, discontinuous, and whiskers. The great breakthrough in the ceramic fibre area has been the concept of pyrolysing polymers under controlled conditions, containing the desired species to produce high-temperature ceramic fibres. Silicon carbide fibre is a major development in the field of ceramic reinforcements. 

Graphene was prepared by four different methods, namely the reductive pyrolysis of camphor (CG), exfoliation of graphitic oxide (EG),4 conversion of nanodiamond (DG)5 and arc evaporation of SiC (SG).6 In the first method, to prepare CG, camphor was pyrolysed over nickel particles under a reducing atmosphere. The reaction was carried out in a two-stage furnace and camphor was slowly sublimed (170 °C) by heating from the first furnace to the second furnace held at 770 °C where the... 

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