Vacuum pyrolysis properties

Most nitrile oxides are unstable, some of them are explosive. This fact hinders the study of their physical properties. Nevertheless, there are a number of publications concerning not only stable but also unstable nitrile oxides. In particular, mass spectral data for nitrile oxides among other unstable compounds containing an N+-X bond are summarized in a review (9). In such studies, the molecular ions must be generated using indirect procedures, including dissociative electron ionization, online flash-vacuum pyrolysis mass spectrometry, or ion-molecular reactions. Their characterization is mainly based on collisional activation and ion-molecular reactions. 

Synthesis. Homometallic pz dimers of Ru (227a) and Os (227b) were prepared, in almost quantitative yield, by vacuum pyrolysis of the monomeric Ru(py)2 or Os(py)2 octaethylporphyrazines (226a and 226b). Heterometallic pz dimers, composed of octaethylporphyrazine and octaethylporphyrin were prepared by the same route that initially produces a mixture of two homometallic (16% each) and the heterometallic dimer (68%), Ru (228a) or Os (229b). The redox properties of the three products are significantly different, by 0.4-0.6 V, so the heterometallic dimer can be separated from the homometallic dimers by redox titrations. 

The compound Os3(CO)j j(C5H5N) is very soluble in acetonitrile, dichl-oromethane, acetone, and methanol, and its solutions are stable to air. It is sparingly soluble in hydrocarbons. Its purity can be checked by IR spectroscopy (dichloromethane solution) v(CO)cm 1 2106(w), 2052(s), 2035(vs), 2008 (s), 1976 (m). Other physical properties have been reported.2 The vacuum pyrolysis of this compound provides a high-yield route to the carbido-dianion [Os10C(CO)24]2-.5... 

Silacyclopentan-2-ol properties, 1, 612 Silacyclopentan-3-ol properties, 1, 612 Silacyclopent-3-ene, 1,1 -dichloro-NMR, 1, 614 Silacyclopentenes flash vacuum pyrolysis, 1, 615 synthesis, 1, 610-612 Silacyclopent-2-enes synthesis, 1, 610 Silacyclopent-3-enes properties, 1, 612 reactions... 

Boucher, M. E., Chaala, A., and Roy, C., Bio-oils obtained by vacuum pyrolysis of softwood bark as a liquid fuel for gas turbines. Part I Properties of bio-oil and its blends with methanol and a pyrolytic aqueous phase. 

Based on the above three models, a dynamic model to scale-up the vacuum pyrolysis process was developed, which correlates the temperature and the mass of feedstock at any position on top of the heating plates inside the reactor, as a function of heat transfer, panicle flow and pyrolysis kinetics phenomena. The energy conservation in the reactor is the foundation of the model. It assumes i) steady flow, ii) one dimensional terr erature variation and, iii) feedstock thermal properties vary as a function of temperature T. 

Vacuum pyrolysis of biomass yields a high amount of oils (bioliiels) which meet several of the heavy fuel performance specifications [9,10]. Some properties of these bio-oils might be improved by upgrading processes such as co-pyrolysis of biomass with heavy crude oils or petroleum residues. 

The physico-chemical properties of the bagasse-derived bio-oil obtained in the large batch reactor are summarized in Table 4. The bio-oil obtained after evaporation contains 13.8 wt.% water. Like the bio-oils originating from diverse biomasses using various pyrolysis techniques, the oil from vacuum pyrolysis of bagasse is heavier (djo = 1.211 g/rnl) than water,... 

The effects of the pyrolysis conditions on the separation properties of the CMS membranes from polyimides were further studied by Geiszler and Koros (1996). It was shown that by raising the pyrolysis temperature from 500 to 800 °C, the effective pore size was reduced, thereby making the CMS membranes more selective but less productive (i.e., lower permeation fluxes). Vacuum pyrolysis versus that in inert gases had the same effect as raising the temperature. 

Recent examples featuring acenaphthylene moieties are included in this section. In general, Pd-catalyzed methods of constructing the CPPAs have overtaken traditional annulations and the harsh conditions of flash vacuum pyrolysis. Readily available haloarenes and reliable synthetic procedures have allowed the preparation of these planar fullerene fragments. Study of the compounds has brought to light some of the defining properties of CPPAs and how the desirable traits of fullerenes can be expressed in small molecules. 

Thermal degradation of polymers is the collection of chemical reactions that result in deterioration of properties in the absence of air or radiation. Purely thermal degradation, in inert atmosphere or vacuum (pyrolysis), defines the ultimate stability of a polymer in the absence of other degradative infiuences. It represents the point where the chemical bonds of the polymer acquire enough thermal energy to break or rearrange spontaneously at significant rates. 

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). 

The chemical properties of 2,3-dihydro-1,4-diazepines are dominated by the presence of the diene portion of the molecules, either by electrophilic attack at the 1, 4 or 6 positions, or nucleophilic attack at positions 5 or 7. There have previously been no observations of the involvement of the saturated part of the molecule. It has now been demonstrated, however, that in vacuum flash pyrolysis there is a suprafacial 1,5 hydrogen shift of a proton from position 7 to position 3 . This has been confirmed by deutero-labelling studies when 7-deutero-2,3-dihydro-methyl-1,4-diazepine is converted into the 3-deutero-isomer. When the study is repeated with the bicyclic t/.s-2,3-cyclohexano derivative the /ram-isomer is isolated, confirminf a suprafacial shift mechanism... 

A property seemingly unique to microwave chemistry is that the individual phases in multi-phase systems can be heated at different rates owing to differences in the dielectric properties. In some cases, a sizeable temperature difference can be maintained for several minutes. This technique has been applied usefully to produce aryl vinyl ketones batchwise by Hofmann elimination in a two-phase system comprising water and chloroform [77]. Although reactions took place in the aqueous phase, the thermally unstable products simultaneously were extracted and diluted into the cooler organic phase, which could be recycled. Yields were nearly quantitative and twice those obtained by traditional pyrolysis-distillation under vacuum. 

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