Reductive pyrolysis

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... 

The TGA data from Figure 1(a) and Schemel indicate that there are five intermediates A, B, C, D, and E before V2O3 (F) forms at 620°C in the reductive pyrolysis process of the precursor. It can be seen from Figure 1(b) that there are eight endothermic peaks on the DTA curve due to the thermolysis effects of the formation of the intermediates. The large exothermic peak at 612°C on the DTA curve is attributed to the exothermic effect of reduction of to The small exothermic peak at 730°C on the DTA curve is attributed to the crystallization of V2O3. 

It is interesting to note in this context that the reductive pyrolysis of Me3SbX2 is synthetically useful only for X = I (see below), for X = Cl, yields of Me2SbCl are low, and Me3SbCl2 has even been sublimed under mild conditions without decomposition. 

Burchfield and his associates (12, 13, 14) reported a procedure involving reductive pyrolysis of the effluent gases whereby compounds containing chlorine, sulfur, or phosphorus form HCl, H2S, or PH3, respectively. By using an aluminum oxide scrubber following the pyrolysis stage, the system was specific for phosphorus. However, the detection system appears to be inferior to other available detectors for phosphorus and will probably have little or no use for this purpose. 

Pyrolysis is commonly carried out in an inert atmosphere. However, oxidative pyrolysis (a pyrolysis that occurs in the presence of an oxidative atmosphere) or reductive pyrolysis (a pyrolysis that occurs in the presence of a reducing atmosphere) is sometimes utilized. 

Fig. 7.14. XRD pattern (a), Raman spectrum (b) and SEM image (c) of the diamond sample synthesized by the reduction-pyrolysis-catalysis route.

Fig. 6.12 Sample pretreatment and conversion of organic compounds into gases for isotope ratio mass spectrometry (IRMS). The reductive pyrolysis is normally performed on glassy carbon (for a summary see e.g. [ 1291). In case of coupled HPLC-IRMS for determination wet oxidation is used [ 122f In the routine isotope ratio analysis of water often isotope equilibration with gases are used for 0-analysis CO2 [ 130], for S H-analysis H2 gas in the presence of Pt [131]. Recently an on-line method for S O and in water has been described showing dual-inlet like performance [ 132]. Low-temperature pyrolysis in connection with GC is used for compound fragmentation with the aim of partial isotope pattern analysis [133]. TC-EA = thermo conversion elemental analyser...

The reference principle for on-line methods has to be different as compared to classic dual-inlet isotope ratio analysis, as it is not possible to introduce sample and reference gas in exactly the same maimer into the mass spectrometer. Reference gas pulses have to be set at different points during one mn, but also laboratory standards with knovm 8-values have to be analysed periodically and exactly in the same manner and under the same conditions as the samples under investigation (identical treatment principle ]13]). A general problem of on-line HPLC and GC methods in isotope ratio analysis is the lack of international reference materials suitable to fulfil the above mentioned requirements. This implies the necessity to establish suitable laboratory standards by EA (elemental analysis) or classic measurements. Meanwhile, also efforts in supplying suitable international organic standards have been overtaken by the IAEA (e.g. caffeine, glutamic acid ]176, 177]). This programme (benzoic acid reference materials with different 8 0-values) will also support the on-line EA and GC 8 0-meas-urement by reductive pyrolysis (carbon reduction) methods (standardisation problems are compiled in ]178]). 

Intermolecular isotopic correlations are thus indicative for the authenticity of natural flavour mixtures. The method for their assessment is GC-C/P-IRMS (combustion/ reductive pyrolysis). As an early example for intermolecular isotope correlations, the result of a GC-C-IRMS analysis of the essential oil from Coriandrum sativum is given in Fig. 6.19 [327]. Further examples are corresponding analyses of oils from Artemisia vulgaris [327], Coriandrum sativum [337] and various lemon oils (Table 6.8) ]325, 338, 339]. In any of these cases typical correlations are found between the compounds of the same origin, even when their average 8-values may differ between... 

Unlike most other elements, the determination of oxygen involves a reductive pyrolysis in an inert gas. The pyrolysis products are passed over carbon, which converts oxygen in the pyrolysis products to carbon monoxide. The general reaction is as follows ... 

Louw, R., J. A. Manion, and P. Mulder. 1986. Reductive pyrolysis an effective method for destruction of chlorinated organic wastes. In Proceedings of the International Conference on Chemicals in the Environment, ed. J. N. Lester, R. Perry, and R. M. Sterritt, pp. 710-14. London Selper. 

Recently a new simple method for the synthesis of diamond, called metallic reduction-pyrolysis-catalysis, was reported. In this method diamond powder was... 

The discovery of phosphorus (white phosphorus, P4) is reported to have occurred as a consequence of the reductive pyrolysis of phosphate (POc ) found in human (and other animal) urine the carbon-containing components being oxidized in the process to CO2 and CO. Phosphate-containing minerals are currently used with charcoal to produce the same material. 

The reductive pyrolysis of organic compounds in the presence of metals leads to the formation of the metal cyanide, which can be detected as Prussian blue (Fe4[Fe(CN)g]3) or by the copper(ii) acetate-benzidine test . Several metals and salts have been recommended for the fusion of the organic compound, e.g. potassium , sodium , magnesium mixed with potassium carbonate , zinc mixed with potassium carbonate , and a mixture of dextrose with sodium carbonate . When the compound contains sulphur the metal thiocyanate is also produced, which can be detected by ferric chloride . ... 

J. Langmaier, F. Opekar, and V. Pacakova. Application of a metallized membrane electrode for the determination of gaseous sulfur compoimds after reductive pyrolysis. Talanta 34 453-459,1987. 

D5454, Water vapor in gaseous fuels D5622, Total oxygen by reductive pyrolysis X X X ... 

Determination of Total Oxygen in Gasoline and Methanol Fuels by Reductive Pyrolysis ... 

These test methods cover the quantitative determination of total oxygen in gasoline and methanol fuels by reductive pyrolysis. 

Precision—The precision of these test methods was determined by statistic analysis of interlaboratory test results. Twelve laboratories analyzed in duplicate eight different samples, providing a total of thirteen data sets. One laboratory us two different test methods. The breakdown on data sets by test method is Test Method A, three Test Method B, two Test Method C, three Test Me od D, five. The statistical analysis was performed on the set of 13 data sets because the reductive pyrolysis technique is common to all four test methods. Separate statistics were not determined for individual test methods. The sample set included anhydrous methanol and gasoline stocks that were spiked with one or more of the following isobutanol, n-butanol, sec-butanol, tfrt-butanol, di-isopropyl ether, ethanol, ethyl ten-butyl ether, methanol, methyl rm-butyl ether, n-propanol, isopropanol, tert-amyl methyl ether. 

The apparatus of this test method can be setup in two different configurations, which will be described herein as the reductive pyrolysis configuration, and the oxyhydropyroly-sis configuration. The reductive pyrolsis configuration is the... 

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