Stepwise pyrolysis

Macromolecular Symposia Vol.135, Dec.1998, p.35-41 STEPWISE PYROLYSIS FOR RECYCLING OF PLASTIC MIXTURES... 

For chemical recycling of plastics refuse, a cascade of cycled-spheres reactors was developed which combined separation and decomposition of polymer mixtures by stepwise pyrolysis at moderate temps. In low-temp, pyrolysis, mixtures of PVC, PS and PE or PS, polyamide-... 

Yang and Epstein76 measured 8D values up to +2860%o on a sample of Murchison obtained by a stepwise pyrolysis of acid residues. These very abnormal 8D values are associated with 813C which are also very high ( +508%o). These observations led the authors to entitle their paper Relic interstellar grains in Murchison meteorite . This problem will be discussed below. 

For the stepwise pyrolysis, the "parent" kerogen for each step is the residual kerogen of the preceding stage of heating. 

H. Bockhom, A. Homung, and U. Homnng, Stepwise pyrolysis for raw material recovery from plastic waste, J. Anal. Appl. Pyrolysis, 46, 1, (1998). 

H. Bockhorn, A. Homung and U. Homung, Stepwise Pyrolysis for Raw Material Recovery from Plastic Waste, J. Anal. Appl. Pyrol, 46, 1-13 (1998). 

H. Bockhorn, J. Hentschel, A. Homung and U. Homung Environmental engineering stepwise pyrolysis of plastic waste, Chem. Eng. ScL, 54, 3043-3051 (1999). 

A. Homung, W. Koch, J. Schoner, J. Furrer and H. Seifert, Stepwise pyrolysis of electronic scrap, TMS Fall 2002 Extraction and Processing Division Meeting on Recycling and Waste Treatment in Mineral and Metal Processing Technical and Economic Aspects, B. Bjorkman, C. Samuelsson, J. O. Wikstrom (Eds.), GTC-Print... 

Stepwise pyrolysis A pyrolysis in which the sample temperature is raised stepwise, i.e. pyrolysis is carried out at a selected temp>erature for a selected period of time after which pyrolyser is stepped rapidly to a higer temperature. 

Commonly, analytical pyrolysis is performed as flash pyrolysis. This is defined as a pyrolysis that is carried out with a fast rate of temperature increase, of the order of 10,000° K/s. After the final pyrolysis temperature is attained, the temperature is maintained essentially constant (isothermal pyrolysis). Special types of analytical pyrolysis are also known. One example is fractionated pyrolysis in which the same sample is pyrolysed at different temperatures for different times in order to study special fractions of the sample. Another special type is stepwise pyrolysis in which the sample temperature is raised stepwise and the pyrolysis products are analyzed between each step. Temperature-programmed pyrolysis in which the sample is heated at a controlled rate within a temperature range is another special type. 

Another special type is stepwise pyrolysis, in which the sample temperature is raised stepwise and the pyrolysis products are analyzed between each step. Temperature-programmed pyrolysis, in which the sample is heated at a controlled rate within a temperature range, is another special type. This type of pyrolysis can be used for analytical purposes but is not very common. 

The results for other conditions for polystyrene pyrolysis were reported. For example, pyrolysis on different catalysts was shown to lead to modifications of the yield of specific components in the pyrolysate. During the pyrolysis of PS on solid acid catalysts, the increase of contact time and surface acidity enhanced the production of ethylbenzene. Pyrolysis in the presence of water increases the yield of volatile products and that of monomer [30]. Studies on the generation of polycyclic aromatic hydrocarbons (PAHs) in polystyrene pyrolysates also were reported [36]. It was demonstrated that the content in PAHs in polystyrene pyrolysates increases as the pyrolysis temperature increases. The analysis of the end groups in polystyrenes with polymerizable end groups (macromonomers) was reported using stepwise pyrolysis and on-line methylation [46]. 

Lopez-Urionabarrenechea A, de Marco I, Caballero BM, Laresgoiti MF, Adrados A. Catalytic stepwise pyrolysis of packaging plastic waste. J Anal Appl Pyrolysis 2012, Jnly 96 54-62... 

Figure 3.8 shows a distribution pattern of volatiles produced during the heating of PES as measured by a combination of TGA and stepwise pyrolysis-gas chromatography-mass spectrometry [95], which indicates that the major products, sulfur dioxide and phenol, are not produced at temperatures below 450 °C. 

The resistively heated pyrolyzer uses either a metal foil or a coil as the sample holder. The heat energy is supplied to the sample holder in pulses by an electric current. This permits stepwise pyrolysis at fixed or increasing pyrolysis temperatures. This feature makes it possible to perform discriminative analysis of volatile formulations and high polymers in a given compound without any preliminary sample treatment. 

C. J. Tsai, L. H. Perng, and Y. C. Ling. "A study of thermal degradation of poly(aryl-ether-ether-ketone) using stepwise pyrolysis/gas chromatography/ mass spectrometry." Rapid Communications in Mass Spectrometry, pp. 1987-1995, 1997. 

A 1 1-mixture of polyvinylacetate and polyvinylpropionate gives acetic and pro-[donic acids. It is striking in both cases that acetic acid is still formed from polyvinylacetate even above 350 °C this conflicts with the results of stepwise pyrolysis-GC It is further noteworthy that the sample required for TFG is only one third of that customary in pyrolysis-GC. 

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