Pyrolysis, flash ethylene

CARBENE. The name quite generally used for the methylene radical, CH,. It is formed during a number of reactions. Thus the flash photochemical decomposition of ketene (CH2=C=0) has been shown to proceed in two stages. The first yields carbon monoxide and CHj. the latter then reacting with more ketene to form ethylene and carbon monoxide. Carbcne reacts by insertion into a C- H bond to form a C-CH, bond. Thus carbene generated from ketene reacts with propane to form, i-butane and isobutane. Carbene generated by pyrolysis uf diazomethane reacts with diethyl ether to form ethylpropyl ether and ethylisopropyl ether. 

The products of the thermolysis of 3-phenyl-5-(arylamino)-l,2,4-oxadiazoles and thiazoles have been accounted for by a radical mechanism.266 Flash vacuum pyrolysis of 1,3-dithiolane-1-oxides has led to thiocarbonyl compounds, but the transformation is not general.267 hi an ongoing study of silacyclobutane pyrolysis, CASSF(4,4), MR-CI and CASSCF(4,4)+MP2 calculations using the 3-21G and 6-31G basis sets have modelled the reaction between silenes and ethylene, suggesting a cyclic transition state from which silacyclobutane or a trcins-biradical are formed.268 An AMI study of the thermolysis of 1,3,3-trinitroazacyclobutane and its derivatives has identified gem-dinitro C—N bond homolysis as the initial reaction.269 Similar AMI analysis has determined the activation energy of die formation of NCh from methyl nitrate.270 Thermal decomposition of nitromethane in a shock tube (1050-1400 K, 0.2-40 atm) was studied spectrophotometrically, allowing determination of rate constants.271... 

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. 

Several reports are available In literature regarding thermal decomposition of poly(ethylene oxide) not in flash pyrolysis conditions. One such report indicates that at temperatures between 324° C and 363° C, the polymer generates 9.7% of volatile compounds (at 25° C), 3.9% monomer with smaller amounts of CO2, formaldehyde, ethanol, and saturated C1-C7 compounds [4]. Another report indicates that at temperatures between 225° C and 250° C, the polymer generates CO2, HCHO,... 

Table 15 compares the results of laser irradiation of coal with flash irradiation and conventional carbonization at 1200 K. Laser irradiation yielded higher conversions of coal and greater percentages of acetylene and higher hydrocarbons than flash irradiation or carbonization. When five bursts of 10 J energy were used to irradiate a cube of coal the acetylene yield increased from 20.9 to 25.9 mole % this constituted 90% of total hydrocarbon products. The decrease in H2 (Table 15), relative to the product from the flash irradiation, is possibly related to the increase in partially saturated structures such as ethylene (4.9%) and propylene (0.7%). Further, components with molecular weights up to 130 were found in the gas from laser irradiation diacetylene and vinylacetylene recognized as pyrolysis products of acetylene accounted for 2.4% of the product. 

Carbonylation of a mixture of ethylene, ethanol, and diphenylacetylene in the presence of rhodium carbonyl gives the butenolide (10). 2 Another formation of a butenolide, that of compound (12), is by flash vacuum pyrolysis of diphenylmethyl propiolate, Ph2CH02C H. It has been suggested that the ester isomerizes to the methylene-carbene (11), which yields the product by intramolecular insertion. Ozonization of tetraphenyl-... 

The Diels-Alder reaction of cyclohexa-1,3-diene (17) with the phosphaalkyne 9a only proceeds under drastic conditions in a pressure Schlenk tube but then does provide the 2-phos-phabicyclooctadiene 18 [23] in quantitative yield (Scheme 6-4). This compound represents the first member of the previously unknown class of polycyclic phosphaallrenes. From a thermal point of view, 18 is unexpectedly stable cycloreversion only occurs under flash vacuum pyrolysis conditions (520°C/10 mbar) but then it does not give rise to the starting materials 9a and 17 instead it proceeds by cleavage of ethylene to furnish the 2-terr-butyl-X -phosphinine [23]. 

Sundaram, M.S., and Steinberg, M. (1986) Interaction between Coal and Methane during En-trained-Flow Flash Pyrolysis in Relation to Enhancement in Ethylene Yield, ACS Div. of Fuel Chem. Prepr 31(1), 162-9, New York, NY (Apr. 13-18). 

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