Showing papers on "Pyrolysis published in 1973"

Molecular weight decrease in the early pyrolysis of crystalline and amorphous cellulose

Abstract: Samples of ordinary “ash-free” cellulose papers and similar samples decrystallized by swelling in liquid ammonia were pyrolyzed in vacuo to a weight loss ranging from <0.1% to nearly 20%. The samples were then nitrated and their molecular weight distributions determined by gel permeation chromatography. When weight loss reached 1%, both the ordinary and the ammonia-swelled celluloses showed a large drop in average degree of polymerization (D.P.). However, the ordinary cellulose showed this sharp drop long before there was any measurable weight loss; the ammonia-swelled cellulose changed D.P. only gradually in the early stages. Further, x-ray diffraction measurements showed that by the time the D.P. of the ammonia-swelled cellulose had dropped appreciably, the material had developed a significant crystalline pattern. These results support the suggestion that initial rupture of the cellulose molecule occurs at strain points at the crystalline–amorphous boundaries.

The influence of fine structure on the pyrolysis of cellulose. I. Vacuum pyrolysis

Abstract: The effects of crystallinity, orientation and degree of polymerization on the vacuum pyrolysis of cellulose have been investigated. Natural, modified and manmade celluloses were characterized and the kinetics of their pyrolysis at 251°C studied. The high-temperature pyrolysis of these samples was also investigated by means of DSC and TGA. At 251°C all of the samples showed a rapid, initial weight loss followed by a linear (weight loss)1/2 versus time dependency. Both the initial weight loss and the subsequent reaction rate were dependent upon the crystallinity of the sample. The reaction rate was shown to be inversely proportional to (DP)1/2 and related to the orientation. Effects of crystallinity and orientation could also be seen in the DSC thermograms and in the apparent energies of activation. Results are interpreted in terms of probable mechanisms of the uncatalyzed pyrolysis of cellulose.

Compositions and methods for high temperature stable catalysts

Abstract: Catalysts having good high temperature stability which are particularly useful for selected high temperature reactions are disclosed as are methods for their preparation and use. The catalytically-active materials include platinum group metal deposited on a catalytic slip or composite which contains a mixture of alumina, selected VIB metal oxides, and a metallic oxide or oxide mixture wherein the metal or metals are selected IIA, IVA, and IIA-IVA mixtures, selected IIA and IVB mixtures and selected IVA and IVB mixtures. The slips or carrier compositions are calcined at a temperature of at least 500°C. before deposition of platinum group metal and characterized by having a surface area of at least 20 m2 g after calcination at a temperature of 1200°C. for two hours.

The influence of fine structure on the pyrolysis of cellulose. II. Pyrolysis in air

Abstract: The pyrolysis of purified celluloses in air at 251°C was studied. The pyrolysis was found to obey first-order kinetics, and the rate constants correlated with the crystallinities, orientations and accessibilities of the samples. The results are interpreted in terms of an oxygen-catalyzed decomposition, with the accessibility of oxygen to the cellulose determining the rate of pyrolysis. The production of levoglucosan under conditions approaching combustion was shown to be a function of the crystallinity and orientation of cellulose. Some levoglucosan appears to be produced from the less ordered regions.

The distribution in lunar soil of carbon released by pyrolysis

Abstract: The carbon contents of various lunar soil particle types and sieve fractions of Apollo 15 and 16 samples have been determined by the pyrolysis method. The mineral, glass, and high-grade breccia fragments in the soils examined contain relatively low amounts of carbon (approximately 8, 25, and 25 microg C/g sample respectively in 149-250 micron grains). Most low-grade breccias and all agglutinates examined have high carbon contents (approximately 52 and 80 microg C/g sample respectively), and agglutinate abundance is indicative of the carbon content and maturity of a soil. The distribution of carbon with respect to particle size in mature soils generally reveals a minimum in carbon content at about 100 micron particle diameter. At smaller particle diameters, carbon content is directly proportional to particle surface area and therefore increases with the ratio (surface area)/(particle mass). A model relating the cycle of comminution and aggregation of soil particles to the redistribution of surface implanted carbon is developed.

Preparation and DC conductivity of an amorphous organic semiconducting system

Abstract: A series of semiconducting samples with noncrystalline structure was prepared by the thermal degradation of phenol formaldehyde resin at different heat treatment temperatures. DC measurements on these organic materials yield an interesting extension of the existing knowledge about the amorphous state. The most important result is the fact that pyrolyzed phenol formaldehyde resins show a temperature dependence on conductivity which is characteristic for the Mott hopping mechanism and identical with that of layers made by evaporating Ge, Si, GaAs or carbon. Hence it does not seem to be the chemical composition that is determining the mechanism of electrical conduction in amorphous solids but only the physical structure.

Production of gaseous olefins from petroleum residue feedstocks

Abstract: Normally gaseous olefins are produced from an atmospheric petroleum residue feedstock by: A. CONTACTING THE FEEDSTOCK IN A HYDROGENATION ZONE WITH A HYDROGENATION CATALYST, OF WHICH NICKEL/TUNGSTEN/SILICA/ALUMINA AND COBALT/MOLYBDENUM/ALUMINA ARE MOST SUITABLE, UNDER CONDITIONS WHICH EFFECT HYDROGENATION OF AROMATIC HYDROCARBONS. Typical conditions are a temperature in the range 50* to 500*C, a pressure in the range 50 to 500 psig, and an LHSV of 0.1 to 5.0 with a hydrogen feed rate of 5 to 10 times the molar feed rate of the feedstock. B. SEPARATING FROM THE HYDROGENATED FEEDSTOCK A GASEOUS PHASE CONTAINING HYDROGEN AND A LIQUID PHASE CONTAINING HYDROCARBONS. C. RECYCLING AT LEAST A PORTION OF SAID GASEOUS PHASE CONTAINING HYDROGEN TO SAID HYDROGENATION ZONE. D. SEPARATING THE LIQUID PHASE FROM (C) INTO A DISTILLATE FRACTION HAVING A BOILING RANGE BELOW 650*C and a residue fraction having a higher boiling range, advantageously by vacuum distillation. E. SUBJECTING THE DISTILLATE FRACTION FROM (D) TO THERMAL CRACKING IN THE PRESENCE OF STEAM THEREBY CONVERTING AT LEAST A PORTION OF THE LIQUID PHASE TO NORMALLY GASEOUS HYDROCARBONS AND F. RECOVERING THE NORMALLY GASEOUS OLEFINS FROM THE PYROLYSIS ZONE EFFLUENT.

Making active carbon from sewage sludge

Abstract: The process of removing solids from sewage, subjecting these solids to pyrolysis, thereby producing active carbon and char, and using both of these materials as adsorbent agents in the treatment of the sewage or other waste water.

Method for treating waste plastics

Abstract: A method for treating waste plastics characterized by melting waste of plastics derived from at least one monomer selected from aliphatic and aromatic unsaturated hydrocarbons, bringing the melt into contact with a particulate solid heat medium in fluidized state maintained at a temperature of 350*-550*C to effect pyrolysis of the melt, and thereafter collecting and condensing the resulting gaseous product to recover a mixture of liquid hydrocarbons Such mixture of liquid hydrocarbons contains ethylenically unsaturated compounds useful as starting material for the production of plastics, such as various olefins and styrene

Reactive intermediates. Part XXIII. Pyrolysis of 1-phthalimido-1,2,3-triazoles: formation and thermal reactions of 2H-azirines

Abstract: Pyrolysis in the vapour phase of 4,5-disubstituted 1-phthalimido-1,2,3-triazoles (1) gives 2H-azirines (2) as the primary isolable products The azirines undergo further thermal reactions under the conditions of the pyrolysis: with a methyl or an ethyl 2-substituent they are cleaved to nitriles and phthalimido-carbenes, but with a phenyl 2-substituent they rearrange to indoles 4-Methyl-5-phenyl-1 -phthalimido-1,2,3-triazole (1c) and 5-methyl-4-phenyl-1-phthalimido-1,2,3-triazole (1d) give identical mixtures of azirines and their pyrolysis products, indicating that the products are formed through a common intermediate, considered to be the antiaromatic 2-methyl-3-phenyl-1-phthalimido-1H-azirine

Process for producing carbon fiber

Abstract: A high productivity process for producing high quality carbon fibers is presented. An acrylonitrile copolymer containing at least 85 mole % acrylonitrile, 0.03 - 11 mole % of at least one cross-linkable vinyl monomer and, if desired, other comonomers, is spun into fibers. The fibers are stretched, pyrolyzed in an oxidizing atmosphere, and further heat-treated in a non-oxidizing atmosphere to effect carbonization and graphitization. To enhance pyrolysis in oxidizing atmosphere, a pyrolysis catalyst is added to the acrylonitrile copolymer, such as ethylene diamine copper nitrate.

Manufacture of catalytic cracking charge stocks by hydrocracking

Abstract: A desirably upgraded charge stock for catalytic cracking containing a relatively large proportion of heavy hydrocarbons boiling above about 800° F., is produced by first subjecting a raw feedstock boiling predominantly above 600° F. and containing a substantial proportion of material boiling above 800° F., to catalytic hydrofining followed by catalytic hydrocracking at high pressures in the presence of a Group VIB and/or Group VIII metal-promoted, crystalline zeolite hydrocracking catalyst. The hydrocracking catalyst and conditions are chosen so as to achieve selective conversion of material boiling between about 600° and 800° F. to lower boiling materials with a relatively minor conversion of the 800° F+ material. The resulting product boiling above 400° F is rich in 800° F+ material, and constitutes an excellent catalytic cracking charge stock.

Homogeneous gas‐phase pyrolyses with a wall‐less reactor. III. The oxygen–ethane reaction. A double reversal in oxygen and surface effects

Abstract: The impact of surface and oxygen on the oxidative pyrolysis of ethane at temperatures above 590°C was studied using a wall-less reactor. At very low conversions under homogeneous conditions, ethene formation begins at the same temperature regardless of whether oxygen is present or absent. Between 0.00 and 0.13% conversion (592–632°C), the rate with oxygen is actually less than the rate in the absence of oxygen. A reversal occurs at about 633°C above which oxygen has a promoting effect. It is concluded that under homogeneous conditions the initiation step in the oxygen-promoted pyrolysis is the same as in the oxygen-free pyrolysis; therefore, initiation by direct attack of oxygen on ethane does not make an important contribution. The decrease in rate observed upon addition of oxygen implies the formation of the relatively unreactive HO2 · radical. As conversion of the HO2 · radical to the more reactive HO · radical becomes significant, the reaction is highly accelerated. If a stainless steel surface is added, the reaction is inhibited at higher conversions in the presence of oxygen. Again at low conversions, a second reversal occurs, and the stainless steel surface acts as a promoter below 649°C. The rate of surfacecatalyzed ethene formation at 590°C equals the rate of homogeneous ethene formation at 630°C.

Additional Volatile Compounds Produced by Pyrolysis of Sulfurcontaining Amino Acids

Abstract: (1973). Additional Volatile Compounds Produced by Pyrolysis of Sulfur-containing Amino Acids. Agricultural and Biological Chemistry: Vol. 37, No. 7, pp. 1759-1761.

The pyrolysis of hexachloroethane

Abstract: The thermal decomposition of hexachloroethane in the presence of chlorine has been studied over the temperature range 340-400°C and a pressure range of 0.5°2.5 atm. The rate of the unimolecular CC bond spliting reaction can be described by the Arrhenius equation Comparison of these rate data with thermodynamic data suggests a combination rate for CCl3 radicals which is consistent with earlier measurements.

Accumulation of Carbon in Lunar Soils

Abstract: Analyses of the carbon compounds released by pyrolysis from size fractions and particle separates of lunar soils indicate that the rate at which extralunar carbon is accumulated is slow compared to the rate at which it is redistributed among the different particle types by the cycle of particle erosion and aggregation. Consequently, much of the carbon acquired from the solar wind and meteorites has been modified by the energetic events that cycle lunar soils.