Direct pyrolysis

Manufacture. For the commercial production of DPXN (di-/)-xylylene) (3), two principal synthetic routes have been used the direct pyrolysis of -xylene (4, X = Y = H) and the 1,6-Hofmaim elimination of ammonium (HNR3 ) from a quaternary ammonium hydroxide (4, X = H, Y = NR3 ). Most of the routes to DPX share a common strategy PX is generated at a controlled rate in a dilute medium, so that its conversion to dimer is favored over the conversion to polymer. The polymer by-product is of no value because it can neither be recycled nor processed into a commercially useful form. Its formation is minimised by careful attention to process engineering. The chemistry of the direct pyrolysis route is shown in equation 1 ... 

Acetylene traditionally has been made from coal (coke) via the calcium carbide process. However, laboratory and bench-scale experiments have demonstrated the technical feasibiUty of producing the acetylene by the direct pyrolysis of coal. Researchers in Great Britain (24,28), India (25), and Japan (27) reported appreciable yields of acetylene from the pyrolysis of coal in a hydrogen-enhanced argon plasma. In subsequent work (29), it was shown that the yields could be dramatically increased through the use of a pure hydrogen plasma. 

Direct pyrolysis in the ion source of a mass spectrometer (QMS) was used to analyse PE/(dicumylperoxide, Santonox R) and PVC/DIOP [259]. In-source PyMS is an analytical tool for fast analysis of flame retardants in unknown mixtures of polymers [223, 265], Heeren and Boon [224] used in-source filament pyrolysis FTMS for high-speed, broadband screening of additives in polymeric household appliances. 

DPyMS Direct pyrolysis mass EGC Evolved gas collection... 

Montaudo and co-workers have used direct pyrolysis mass spectrometry (DPMS) to analyse the high-temperature (>500°C) pyrolysis compounds evolved from several condensation polymers, including poly(bisphenol-A-carbonate) [69], poly(ether sulfone) (PES) and poly(phenylene oxide) (PPO) [72] and poly(phenylene sulfide) (PPS) [73]. Additionally, in order to obtain data on the involatile charred residue formed during the isothermal pyrolysis process, the pyrolysis residue was subjected to aminolysis, and then the aminolyzed residue analysed using fast atom bombardment (FAB) MS. During the DPMS measurements, EI-MS scans were made every 3 s continuously over the mass range 10-1,000 Da with an interscan time of 3 s. 

A. Ballistreri, M. Fichera, P. Fifi, G. Musumarra, Characterization of Vasari and Zuccari Binding Media by Direct Pyrolysis in the Mass Spectrometer, Science and Technology for Cultural Heritage, 7, 27 30 (1998). 

Qian, K. Killinger, W.E. Casey, M. Nicol, G.R. Rapid Polymer Identification by In-Source Direct Pyrolysis Mass Spectrometry and Library Searching Techniques. Anal. Chem. 1996, 68, 1019-1027. 

BaUistreri A, Eichera M, Eifi AP, Musumarra G (1998) Characterisation of Vasari and Zuc-cari binding media by direct pyrolysis in the mass spectrometer. Sci Tech Cult Heritage 7 27-30. 

With so few examples little has been done to define the general reactions of the parent systems. However, direct pyrolysis of the benzoxazinone (14) yields biphenylene, whereas flash vacuum pyrolysis causes C-N transposition and leads to the 3,1-isomer (15) (78CC9). 

Schulten, H.-R. (1996). Direct pyrolysis-mass spectrometry of soils A novel tool in agriculture, ecology, forestry, and soil science. In Mass Spectrometry of Soils, Boutton,T. W., and Yamasaki, S., eds., Marcel Dekker, New York, pp. 373-436. 

Thus, the presence of 03 as a background gas provides new sources for OH radical formation during sonolysis. The direct pyrolysis in the cavitation bubbles of volatile intermediates generated during ozonation also explains the improvement in the overall efficiency. In addition to these direct chemical effects, sonication also increases mass transfer coefficients of ozone from the bubbles to the solution, where the direct reaction of 03 with the substrates, or further radical formation, takes place. 

Direct pyrolysis of the cyclic sulfides without prior chemical modification [11] special method without general importance in cyclophane chemistry. 

After these preheat treatment processes, the two treated (cross-linked) PMS resins were pyrolyzed at 1273 K. Resin recovery after preheat treatment and ceramic yield of these cross-linked resins at 1273 K are summarized in Table 19.2. Use of the reflux system is effective to increase resin recovery and ceramic yield. Figure 19.4 shows the overall ceramic yield of the starting PMS with different thermal histories. The dotted line indicates the intrinsic ceramic yield from PMS by direct pyrolysis up to 1273 K (about 30%). The filled circle indicates the ceramic yield at 1273 K with two-step pyrolysis, in which reflux treatment is the first step. Overall ceramic yield begins to increase at 423 to 523 K, and is saturated (approximately 75%) at 623 K. Even when a preheat treatment step on PMS is a simple heat treatment in an open argon gas flow (open circle), the overall... 

The chemicals that are produced from polysaccharides by direct pyrolysis were discussed in Chapter 8. A few of them are expected to be marketed in the future, particularly some of the oxygenates from fast pyrolysis processes (Scott, Piskorz, and Radlein, 1993 Piskorz et al, 1995). 

Direct pyrolysis of the DKPs corresponding to Pro-Val or Val-Pro was proven to generate the same types of compounds shown in Table 12.2.2. This is a proof that DKPs are the main primary pyrolysis products of these dipeptides. However, the pyrolysis of the dipeptides and their corresponding DKP does not generate identical pyrograms (chromatographic profiles of the pyrolysates). Therefore, some other processes may take place during the pyrolysis of each compound. 

Numerous studies done on conjugated proteins were oriented toward the differentiation of the material without performing special separations. For example, direct pyrolysis of several enzymes showed a significant difference in the chromatographic profile of the pyrolysate. The enzymes analyzed by this procedure included a-chymotrypsin, creatine kinase, lactate dehydrogenase, catalase, acetylcholinesterase, and urease [19,20]. 

The controversy around the two possible origins of the BH ion (from direct pyrolysis or from the nucleoside-like ion) necessitated studies using linked scan techniques and metastable-ion mapping." From those results it is clear that the BH ions, as well as methylfuran particles, are formed directly by the pyrolitic process. 

Pyrolysis with TMAH derivatization may provide more information regarding the end groups than straight pyrolysis since it may occur at lower temperature and generate fewer polar compounds, which can be analyzed more successfully with chromatography. For example, the structures of some copolymers of polycarbonates were determined with better results using pyrolysis with TMAH than by direct pyrolysis [24]. 

This group of semi-synthetic resins is rather difficult to analyze by other techniques, and pyrolytic methods have been applied successfully for their analysis, either using direct pyrolysis or using pyrolysis with hydrolysis and methylation for example in the presence of TI H [66, 67], The pyrolysate in the presence of TMAH contains fragments of both components of the resin, including the methyl ester of abietic acid and various methylated phenols. 

A direct pyrolysis-gas chromatography of the kerogens was also performed and is presented in Figure 7 (9). The chromatograms taken at pyrolysis temperature of 475°C show the total distribution of hydrocarbons, with the relative importance of long-chain molecules up to C30 in types I and III. It also shows the importance of low-boiling aromatics (B benzene T toluene ... 

In this study, to make a comparison with drying-pyrolysis process, the experiments on direct feed processes, i.e., direct pyrolysis process and incineration process, were conducted. In these processes, the dewatered cake was directly fed into the furnace. The plant was operated at steady state for at least 5 or 6 hours in all runs. 

Process Drying-pyrolysis Direct pyrolysis Incineration ... 

Exhaust Gases Table IV shows the analytical results of exhaust gas from drying-pyrolysis process and from direct pyrolysis process and incineration process on cake A, 3 to 83 % of S in the fed cake remains in the residue, 17 to 51 % of S converts... 

---