Pyrolysis, flash gases

Alternative pathways, also discussed in part in the various chapters, include (catalytic) pyrolysis, flash or fast processes for wet biomass without pre-drying, hydro-thermal upgrading (HTU), conversion of solid biomass more or less directly into a natural-gas equivalent called substitute natural gas (SNG), or even to hydrogen. 

Flash-liquid Liquid obtained from flash pyrolysis accomplished in a time of < 1 s Flash-gas Gaseous material obtained from flash pyrolysis within a time of < 1 s Hydropyrolysis Pyrolysis with water Methanopyrolysis Pyrolysis with methanol Ultrapyrolysis Pyrolysis with very high degradation rate... 

GC = gas chromatography, Py = pyrolysis (flash or hydrous heating), MS = mass spectrometry (HR = high resolution), IRMS = isotope ratio mass spectrometry, HPLC = high-pressure liquid chromatography, EC = electron capture. Cl = chemical ionization, NMR = nuclear magnetic resonance spectrometry. X-ray = X-ray crystallography. 

The first isolated 3//-phosphole, namely 3//-phosphaindene 50, was obtained as a 1 1 mixture with its hydration product 51 by gas-phase pyrolysis (flash vacuum pyrolysis, FVP) over a solid base (Scheme 7) <1999TL5271>. The hindered P=G bond of compound 50 is unreactive. 

In slow pyrolysis, the gas phase contains less methane and ethylene and more ethane and propane than hy flash pyrolysis (see Tables 10.4 and 10.7). The product yields obtained in the literature by different authors for the PE for slow pyrolysis (Pinto, Madorsky, Bockhom, Tsuji and Williams) and fast pyrolysis (Kaminsky, Williams, Scott and Conesa) are respectively presented in Eigures 10.2 and 10.3. 

At higher temperature (700°C), in slow pyrolysis, the gas phase contains less methane and more propane, propene and butene than by flash pyrolysis (see Tables 10.9 and 10.12). 

Diels-Alder reactions, 4, 842 flash vapour phase pyrolysis, 4, 846 reactions with 6-dimethylaminofuKenov, 4, 844 reactions with JV,n-diphenylnitrone, 4, 841 reactions with mesitonitrile oxide, 4, 841 structure, 4, 715, 725 synthesis, 4, 725, 767-769, 930 theoretical methods, 4, 3 tricarbonyl iron complexes, 4, 847 dipole moments, 4, 716 n-directing effect, 4, 44 2,5-disubstituted synthesis, 4, 116-117 from l,3-dithiolylium-4-olates, 6, 826 electrocyclization, 4, 748-750 electron bombardment, 4, 739 electronic deformation, 4, 722-723 electronic structure, 4, 715 electrophilic substitution, 4, 43, 44, 717-719, 751 directing effects, 4, 752-753 fluorescence spectra, 4, 735-736 fluorinated derivatives, 4, 679 H NMR, 4, 731 Friedel-Crafts acylation, 4, 777 with fused six-membered heterocyclic rings, 4, 973-1036 fused small rings structure, 4, 720-721 gas phase UV spectrum, 4, 734 H NMR, 4, 7, 728-731, 939 solvent effects, 4, 730 substituent constants, 4, 731 halo... 

Flash Pyrolysis Coal is rapidly heated to elevated temperatures for a brief period of time to produce oil, gas, and char. The increase in hydrogen content in the gases and hquids is the result of removing carbon from the process as a char containing a significantly reduced amount of hydrogen. Several processes have been tested on a rela-... 

Starting from 27, cyclo-Cig was prepared in the gas phase by laser flash heating and the neutral product, formed by stepwise elimination of three anthracene molecules in retro-Diels-Alder reactions, was detected by resonant two-photon-ionization time-of-flight mass spectrometry [23]. However, all attempts to prepare macroscopic quantities of the cyclocarbon by flash vacuum pyrolysis using solvent-assisted sublimation [50] only afforded anthracene and polymeric material. 

UV irradiation (A>300nm) of an argon matrix containing tetra-fluoromethane led to the formation of difluorocarbene CF2 (Milligan and Jacox, 1968a). It was shown that the IR spectrum of this species contains three bands at 1222 (i i), 1102 (v ), and 668 (i 2)cm . Some time later difluorocarbene was stabilized in a neon matrix at 4.2 K from the gas phase after vacuum flash pyrolysis (1300°C) of perfluoroethene (Snelson, 1970b). In this case the IR bands of CF2 differed from those in an argon matrix by less than 2 cm . ... 

Currently, there is renewed interest in this process. At Twente University (The Netherlands), research is performed toward the use of bio-oil from (flash) pyrolysis as the reducing agent for the oxidized iron.149 Therefore, a CO-containing gas stream and a relatively pure H2 stream is generated separately from the biomass-derived bio-oil. 

FVP-gas electron diffraction (FVP-GED), 21 139. See also Flash vacuum pyrolysis (FVP)... 

Gas-phase analytical methods, flash vacuum pyrolysis and, 21 139-140 Gas-phase decomposition, of Group III organometallics, 22 156 Gas-phase grown carbon fibers, 26 736-737 Gas-phase height of a transfer unit (HG), 1 51-52... 

The Curie Point flash evaporation-pyrolysis gas chromatography-mass spectrometric method [32] described in section 2.2.1.2 for the analysis of aromatic hydrocarbons in soils has also been applied to the determination of heteroaromatic compounds (Table 2.2) such as methyledene, isomeric methylidenes, biphenyl and methylbenzofurans. 

The polyaromatic hydrocarbons in the soil sample were quantitated by using an external standard of anthracene. The results reportedly for a polluted soil and sediment sample indicate that this flash evaporation-pyrolysis technique combined with gas chromatography-mass spectrometry is a valuable tool for rapidly screening polluted samples for virtually all types of anthropogenic contaminants except for heavy metals. 

The flash evaporation pyrolysis gas chromatography method [16] as described in section 11.1.4 for the determination of polycyclic aromatic hydrocarbons, haloorganics, aliphatic hydrocarbons, heteroaromatics, elemental sulphur and pyrolysis products of synthetic polymers in soils has also been applied to non-saline sediments. 

Fig. 11.4 shows the total ion current trace and some mass chromatograms obtained by flash evaporation pyrolysis gas chromatography-mass spectrometric analysis of the polluted sediment sample. All compounds present in this complex mixture were not listed. A selection was made to exemplify several aspects of the screening approach. The peak number correspond with the numbers in Table 11.1. Identifications were based on the same criteria as mentioned above. Although several components were shown to be real pyrolysis products, all the compounds are present as such in the sample and resulted from simple thermal extraction from the wire. This was shown in separate analyses using ferromagnetic wires with a Curie temperature of 358°C. 

The gas-phase pyrolysis of vinylogous systems of isopropylidene amino-methylenemalonates (1280,1287, and 1290), prepared from the appropriate enaminone or dienaminone and Meldrum s acid in pyridine, was studied by McNab etal. at 500°C and 10 2 torr (87CC140). Flash vacuum pyrolysis of 1280 gave l//-azepinones (1283) in —60% yields, together with a small amount of cyclopentadienone dimer (1284). They suggested that the azepi-nones (1283) were formed by electrocyclization from dipolar intermediates (1282) produced from the methyleneketenes (1281) by hydrogen transfer (Scheme 54). Cycloaddition of 1282 yielded bicyclics (1285), which col-... 

Pyrolysis oil (bio-oil) is produced in fast and flash pyrolysis processes and can be used for indirect co-firing for power production in conventional power plants and potentially as a high energy density intermediate for the final production of chemicals and/or transportation fuels. Gas chromatographic analysis of the liqtrid fraction of pyrolysis products from beech wood is given in Table 3.6 (Demirbas, 2007). Biocmde resrrlts from severe hydrothermal upgrading (HTU) of relatively wet biomass and potentially can be used for the production of materials, chemicals,... 

The decisive break came in 1991 when Scott and co-workers reported the formation of corannulene from 7,10-diethynylfluoranthene 19 under flash vacuum pyrolysis (FVP) conditions. The critical features of this approach appear to be the high temperature employed (900-1000 °C) and the gas-phase conditions. The high temperature provides energy for drastic fluctuations in 8 away from its equilibrium geometry, allowing the reactive centers to come close enough to form the new bonds while the gas-phase conditions prevent polymerization (although some polymeri-... 

Flash vacuum pyrolysis (FVP) represents a special method for inducing decomposition of thietane compounds. Block et al. succeeded for the first time in the preparation of methylene sulfine in the gas phase, applying this method to thietane 1-oxide. The reaction starting at 600°C was followed by mass and microwave spectroscopy. 

A third advantage that matrix isolation has over frozen solvents is that the reactive intermediates must not necessarily be generated in situ, but can be made by flash vacuum pyrolysis or in plasma processes prior to their quenching with an excess of the host gas on the cold surface. Of course, this considerably widens the range of reactive intermediates that can be investigated, beyond those that require photolysis or some form of radiolysis for their formation. 

The methods for external generation of reactive intermediates are similar to those used in gas-phase experiments, that is, flash vacuum pyrolysis, passing a... 

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