Showing papers on "Pyrolysis published in 1993"
TL;DR: In this paper, a variation of the thermal/optical reflectance method has been applied to over 27,000 samples taken in more than a dozen urban and regional air quality studies in the U.S.
1,186 citations
01 Jan 1993
TL;DR: The state of the art in carbon-carbon composites can be found in this paper, where a brief survey of commercial CVD composite fabrication processes is presented, as well as a review of the state-of-the-art.
Abstract: Part 1 Introduction: carbon bonding in carbon materials order and disorder in carbon materials techniques for characterizing the structure of carbons definition of carbon forms and processes carbon composites carbon-carbon composites. Patr 2 Carbon fibres: processing of carbon fibres the structure of carbon fibres commercially available fibres surface treatment of carbon fibres and interfacial bonding carbon fibre product form. Part 3 Gas phase impregnation/densification of carbon-carbon and other high-temperature composite materials: the CVD process physics - chemical principles of the CVD process experimental CVD techniques CVD processing of carbon-carbon composites CVD processing of ceramic matrix composites a brief study of commercial CVD composite fabrication processes. Part 4 Thermosetting resin matrix precursors: general considerations isotropic carbon carbon yield from polymers carbonization of composites graphitization impregnation technology high carbon yield matrix precursors. Part 5 Thermoplastic matrix precursors: pitch characterization of pitches pyrolysis of pitches carbon yield from pitch the influence of additives on carbonization control of microstructure in pitch-derived carbon-carbon composites low-pressure composites processing high-pressure processing of pitch derived carbon-carbon thermoplastic polymer matrix precursors. Part 6 Oxidation behaviour of carbon-carbon: fundamental concerns in the oxidation protection of carbon-carbon composites protection at temperatures below 1500 degrees C protection coating for the 1500-1800 degree C range oxidation protection at temperatures in excess of 1800 degrees C. Part 7 Raw materials: densification of composites by CVD fabrication of thermoset resin laminated precursors processing thermoplastic precursors graphitization of carbon-carbon mechanical testing of carbon-carbon microscopy density and porosity measurements oxidation and oxidation protection measurement of thermal conductivity. Part 8 The properties of carbon-carbon composites: general consierations microstructure interfaces in carbon-carbon composites mechanical properties thermal properties electromagnetic properties. Part 9 Applications of carbon-carbon composites: brakes and clutches rocket motors heatshields for re-entry vehicles aero-engine components industrial applications biomedical devices. Part 10 Technology summary and market review: the state of the art the carbon-carbon market commercializing a product organization of the carbon-carbon business major companies in the carbon-carbon market.
664 citations
TL;DR: In coal pyrolysis, a number of new experimental and theoretical approaches have been proposed to shed new light on the subject as mentioned in this paper, such as kinetics, the formation of volatile products, network models, cross-linking, rank effects, and the two-component model of coal structure.
305 citations
Patent•
27 May 1993
TL;DR: An intergrated recycle process for the production of methanol from a process synthesis gas produced by hydrogasification of a condensed carbonaceous feedstock to produce a process gas which is reacted in a steam pyrolysis reactor with additional natural gas and steam to produce said synthesis gas containing hydrogen and carbon monoxide in more than a 2:1 molar ratio which constituents in turn are reacted in an intermediate stage as discussed by the authors.
Abstract: An intergrated recycle process for the production of methanol from a process synthesis gas produced by hydrogasification of a condensed carbonaceous feedstock to produce a process gas which is reacted in a steam pyrolysis reactor with additional natural gas and steam to produce said synthesis gas containing hydrogen and carbon monoxide in more than a 2:1 molar ratio which constituents in turn are reacted in a methanol synthesis reactor to produce methanol. The important factor in this process includes the sequence of reactors of the condensed carbonaceous material: a hydrogasification reactor; the stream and natural gas pyrolysis reactor; the methanol synthesis reactor and the recycling to the hydrogasification reactor of the hydrogen-rich gas stream remaining after the methanol synthesis and separation of the methanol product.
249 citations
TL;DR: In this paper, the upgrading of a fast pyrolysis bio-oil and its two fractions was studied at atmospheric pressure using HZSM-5 as catalyst and the goal was to maximize the desired organic distillate product with a high concentration of aromatic hydrocarbons.
Abstract: The upgrading of a fast pyrolysis bio-oil and its two fractions was studied at atmospheric pressure using HZSM-5 as catalyst. The two fractions were pyrolytic lignin (which remained after removing water-soluble components from the whole bio-oil) and resid oil (which remained after separating phenolic fraction from the whole bio-oil). The upgrading was done in the temperature range of 340-410°C in a fixed bed microreactor. The objective was to maximize the desired organic distillate product with a high concentration of aromatic hydrocarbons. The maximum organic distillate from the upgrading of whole bio-oil was 19 wt% of bio-oil and the highest concentration of aromatic hydrocarbons in the distillate was 83 wt%
232 citations
TL;DR: In this article, a mathematical model of transport phenomena (heat, momentum and mass transfer) and chemical processes (primary and secondary reactions) of the thermal degradation of wood is presented, where implicit finite difference equations for energy, momentum, and chemical species mass balances are formulated according to an operator splitting technique and are numerically solved.
Abstract: A mathematical model of transport phenomena (heat, momentum and mass transfer) and chemical processes (primary and secondary reactions) of the thermal degradation of wood is presented. Implicit finite difference equations for energy, momentum and chemical species mass balances are formulated according to an operator-splitting technique and are numerically solved. The progress of the pyrolysis process along a wooden slab, radiatively heated on one side, is characterized by the following main processes: 1( a virgin wood region, crossed by a slow flow of pyrolysis products, where temperature and pressure values decrease as the non-irradiated boundary is approached; 2( a primary pyrolysis region where, due to the relatively low temperatures, secondary reactions are not active and 3( a char layer where volatile products of primary pyrolysis mainly flow and, temperature being higher, undergo secondary reactions. For low medium permeabilities, a peak in the gas overpressure is observed, separating the v...
204 citations
TL;DR: In this article, the formation of NO x precursors during rapid pyrolysis was investigated for 20 coals covering wide ranks at temperatures of 853-1488 K to elucidate the influence of coal properties on NO x formation during coal combustion.
Abstract: The formation of NO x precursors during rapid pyrolysis was investigated for 20 coals covering wide ranks at temperatures of 853-1488 K to elucidate the influence of coal properties on NO x formation during coal combustion. It was found that the main compositions of volatile nitrogen are HCN, NH 3 , and N 2 under these experimental conditions. Their yields are strongly dependent on coal types and pyrolysis temperature. By analyzing functional forms of coal nitrogen in parent coals and chars after pyrolysis using X-ray photoelectron spectroscopy, the relation between nitrogen functionality and formation of nitrogen-containing species has been further demonstrated. Three nitrogen functional forms of pyrrole type, pyridine type, and quaternary nitrogen are observed for all coals
183 citations
Patent•
23 Nov 1993
TL;DR: In order to reduce the rate of coke formation during the industrial pyrolysis of hydrocarbons, the interior surface of a reactor is coated with a thin layer of a ceramic material, the layer being deposited by thermal decomposition of a non-oxygen containing silicon-nitrogen precursor in the vapor phase, in an inert or reducing gas atmosphere in order to minimize the formation of oxide ceramics as discussed by the authors.
Abstract: In order to reduce the rate of coke formation during the industrial pyrolysis of hydrocarbons, the interior surface of a reactor is coated with a thin layer of a ceramic material, the layer being deposited by thermal decomposition of a non-oxygen containing silicon-nitrogen precursor in the vapor phase, in an inert or reducing gas atmosphere in order to minimize the formation of oxide ceramics.
181 citations
TL;DR: In this article, the formation of C60 and C70 by pyrolysis of naphthalene at ∼1,000 °C was reported, showing that closed fullerene cages can be built from well defined aromatic fragments.
Abstract: THE formation of bulk quantities of C60 by arc discharge between carbon electrodes in an atmosphere of helium1 or argon2,3 has led to an explosion in fullerene research. Methods for improving the rate of fullerene production have included increasing the reactor size and the diameter of the carbon rods, and varying the rate of rod consumption and helium pressure4. Systems using several rods have also been employed5,6. The ideal method, however, would involve a continuous process that does not require rod replacement. Approaches using carbon granules6 and powders7 have been reported, as well as combustion methods using hydrocarbons8,9. Here we report the formation of C60 and C70 by pyrolysis of naphthalene at ∼1,000 °C. C60 and C70 are formed by the 'patching together' of six and seven naphthalene molecules respectively, as demonstrated by mass-spectrometric analysis of intermediate products. These results point to a continuous method of fullerene formation, and also show that closed fullerene cages can be built from well defined aromatic fragments.
177 citations
TL;DR: In this article, the authors describe the noncatalytic conversion of cellulose in supercritical and subcritical water and demonstrate that even without any acid catalyst, cellulose was rapidly converted to water soluble species with a relatively high glucose yield in near critical water and glucose yield increased with elevating temperature.
Abstract: This paper describes the noncatalytic conversion of cellulose in supercritical and subcritical water. First, it was demonstrated that even without any acid catalyst, cellulose was rapidly converted to water soluble species with a relatively high glucose yield in near critical water and glucose yield increased with elevating temperature. Then the rate constants for cellulose decomposition and glucose decomposition were evaluated at a pressure of 25 MPa over a temperature ranging from 473 K to 673 K by using semi-batch reactor and a flow reactor, respectively. From the reported cellulose pyrolysis rate constant and the evaluated cellulose decomposition rate constant, cellulose hydrolysis rate constant was evaluated. By using the cellulose hydrolysis rate, cellulose pyrolysis rate and the glucose decomposition rate, glucose yield obtained in the semi-batch experiment was reasonably explained.
174 citations
TL;DR: In this paper, a thermogravimetric analyser was applied for the temperature range from 300 to 450 °C and an entrained flow reactor was used for measurements in the temperature ranges from 450 to 600 °C, the kinetic expression that describes the mass loss of sawdust due to pyrolysis was assumed to be of a single first-order in the unconverted wood.
TL;DR: In this article, the primary thermal degradation mechanisms of polyethyleneterephthalate (PET) and polybutylenetrephthalate(PBT) have been studied by direct pyrolysis mass spectrometry using negative chemical ionization (NCI).
TL;DR: In this article, the pyrolysis history of polyvinyl chloride (PVC) in the experimental conditions of this investigation consisted of two distinct stages with four reactions, which can be also expressed by an overall rate equation.
TL;DR: A series of silsesquioxane copolymers synthesized by hydrolysis and condensation of phenyl- and methyltrimethoxysilanes have been studied as preceramic polymers as mentioned in this paper.
Abstract: A series of silsesquioxane copolymers synthesized by hydrolysis and condensation of phenyl- and methyltrimethoxysilanes have been studied as preceramic polymers. The pyrolytic conversion to ceramics was characterized by thermogravimetric analysis, 29Si and 13C nuclear magnetic resonance and Raman spectroscopy. The pyrolysed materials were further characterized by differential thermal analysis. X-ray diffractometry and transmission electron microscopy. The ratio of phenyl to methyl groups in the copolymer was found to control polymer structure and rheology, as well as ceramic composition and char yield. On pyrolysis to 1000 °C under inert conditions, silicon oxycarbides were formed, along with glassy carbon. On heating from 1200 °C to 1400 °C, the oxycarbide structure diminished, and the materials were comprised primarily of amorphous silica, amorphous Si-C, some small crystallite SiC and graphitic carbon. The carbon content increased, and char yield decreased, with increasing concentration of phenyl groups in the copolymer. The presence of free carbon appears to inhibit the crystallization of silica. Significant carbothermal reduction was observed only above 1500 °C. Oxidation studies of the pyrolysed materials indicated the presence of at least two forms of carbon.
TL;DR: In this paper, three Tertiary Catalan lacustrine oil shales were analyzed by light microscopy, flash pyrolysis-gas chromatography-mass spectrometry, and bulk composition methods.
TL;DR: In this paper, a static batch of shredded scrap automotive tyres were pyrolysed in a static-batch reactor in a stream of nitrogen and the products were passed directly to a second heated reactor, where secondary reactions of the pyrolysis vapours occurred.
TL;DR: In this paper, particles with narrow size distributions were produced by CO2 laser pyrolysis of vapor mixtures of Fe(CO)5 and C2H4, and they were observed to be ferromagnetic in this size range.
Abstract: Nanocrystalline α–Fe, Fe3C, and Fe7C3, particles with narrow size distributions were produced by CO2 laser pyrolysis of vapor mixtures of Fe(CO)5 and C2H4. Details of the synthesis procedure are discussed. Mossbauer spectroscopy and x-ray diffraction were used to identify the structural phases and the former was used also to study the magnetism of the nanoparticles. All the nanoparticles were observed to be ferromagnetic in this size range. If excess C2H4 appears in the reactant gas mixture, several monolayers of pyrolytic carbon were observed to form on the particle surface, as deduced from transmission electron microscopy and Raman scattering studies. Results of thermo-gravimetric analysis/mass spectroscopy studies of this carbon coating indicate it is gasified in hydrogen at temperatures T ∼ 250 °C.
TL;DR: In this article, X-ray diffraction performed on CoPc/XC-72 pyrolyzed between 700 and 1,150 C reveals the presence of [beta]-Co particles whose average size varies from 9 nm at 700 C to 44 nm at 1, 150 C.
Abstract: Cobalt phthalocyanine (CoPc) adsorbed on carbon black (XC-72) and heat-treated at temperature ranging from 300 to 1,150 C display catalytic activity toward the electroreduction of oxygen in acidic medium (H[sub 2]SO[sub 4],pH 05) The best catalysts are obtained for pyrolysis temperatures ranging from 700 to 950 C X-ray diffraction performed on CoPc/XC-72 pyrolyzed between 700 and 1,150 C reveals the presence of [beta]-Co particles whose average size varies from 9 nm at 700 C to 44 nm at 1,150 C Co and N bulk elemental analyses have been performed on CoPc/XC-72 heat-treated from 20 to 1,150 C These show that: (1) there is no loss of Co even after pyrolysis at 1,150 C when the loading is at 2 weight percent (w/o) Co; (2) the bulk N content decreases as the pyrolysis temperatures are increased and the N content reaches the detection limit (05 w/o) at pyrolysis temperatures [>=] 1000 C X-ray photoelectron spectroscopy (XPS) study shows that at 600 C there is a sudden three-fold increase in the surface concentration of Co and N at the surface of the carbon black support A sublimation-redistribution of the CoPc is proposed The effect appears to limit the Co loading to approximatelymore » 2 w/o (At loadings of 4 and 8 w/o Co, most of the Co is lost due to the sublimation) The XPS study also shows that metallic Co particles begin to be formed at 600 C, and that the formation and growth of Co particles occurs as the pyrolysis temperature increases to 1,050 C The chemical stability of the pyrolyzed catalysts was evaluated in concentrated H[sub 2]SO[sub 4],HCl, and HNO[sub 3] for time periods ranging from 1 to 30 min Bulk Co analysis, after immersion in acid, indicate that up to 40% of the Co can be lost in the process, and that this induces a decrease in the catalyst activity« less
TL;DR: In this article, a comprehensive review of the interactive transport processes in the gasification and combustion of a cloud of drops and solid particles is presented, and the results on the internal ignition of porous char particles using a Frank-Kamenetskii type of analysis.
TL;DR: In this article, the porosity development during steam activation of tire pyrolysis char is similar to that reported for various other chars, suggesting that the activation process consists of micropore formation, followed by pore enlargement.
Abstract: The primary objective of this work was to demonstrate the conversion of scrap tires to activated carbon. The authors have been successful in this endeavor, producing carbons with surface areas greater than 500 m[sup 2]/g and significant micropore volumes. Tire shreddings were pyrolyzed in batch reactors, and the pyrolysis chars activated by reaction with superheated steam. Solid products of pyrolysis and activation were studied with nitrogen adsorption techniques. They find that the porosity development during steam activation of tire pyrolysis char is similar to that reported for various other chars. A maximum in micropore volume is observed as a function of conversion, but the total surface area increases monotonically with conversion. They suggest that the activation process consists of micropore formation, followed by pore enlargement. The process conditions used in this study are a good starting point from which to optimize a process to convert tires to activated carbon.
TL;DR: In this article, the pyrolysis of polycarbosilazane copolymers was investigated up to 1600 °C by analyses performed on the solids (elemental analysis; EPMA; TGA, density; 1H, 13C and 29Si solid state NMR, i.r.
Abstract: Novel polycarbosilazanes (PCSZs) were prepared by stepwise synthesis and thermal crosslinking of polysilasilazane (PSSZ) copolymers. Their pyrolysis under inert gas, producing Si-C-N ceramics, was investigated up to 1600 °C by analyses performed on the solids (elemental analysis; EPMA; TGA, density; 1H, 13C and 29Si solid state NMR, i.r. XRD, electrical conductivity) and analyses of the evolved gases (gas chromatography and mass spectrometry). From 250 to 450 °C, a first strong weight loss was observed, which was due to the formation and elimination of low-boiling-point oligomers. The weight loss closely depends on the cross-linking degree of the ceramic precursor resulting from the PSSZ/PCSZ conversion. Then, the organic/inorganic transition took place between 500 and 800 °C, proceeding via evolution of gases (mainly H2 and CH4) and yielding a hydrogenated silicon carbonitride. This residue remained stable up to 1250 °C although it progressively lost its residual hydrogen as the temperature was raised. Then, crystallization occurred between 1250 and 1400 °C, yielding β-SiC crystals surrounded by free-carbon cage-like structures. Finally, above 1400 °C, the remaining amorphous Si-C-N matrix underwent a decomposition process accompanied by nitrogen evolution and a second substantial weight loss. At 1600 °C, the pyrolytic residue was a mixture of β-SiC and free carbon. So, the amorphous silicon carbonitride resulting from the pyrolysis of PCSZ precursors was found to be appreciably more thermally stable than the previously reported Si-C-O ceramic obtained by pyrolysis of polycarbosilane precursors.
TL;DR: In this article, a high vapor pressure liquid hydrocarbon (hexane) dissolves a suitable organometallic source of iron catalyst particles, ferrocene, and is efficiently vaporized by incorporating it in a flowing gas stream containing some hydrocarbons and air.
TL;DR: In this paper, a wide range of substrates, including methylene chloride, 1,2-dichloroethane and carbon tetrachloride, are converted selectively to CO 2, CO, and HCl.
Abstract: Catalysts comprising metal oxides dispersed on porous carbon supports are shown to be very effective in the decomposition of halogenated hydrocarbons by air at and below 250 o C. A wide range of substrates, including methylene chloride, 1,2-dichloroethane, 1,2,4-trichlorobenzene, tetrachloroethylene, 1, 1,2,2-tetrachloroethane, and carbon tetrachloride, are converted selectively to CO 2 , CO, and HCl. The carbon supports also show significant activity in the absence of metal species. Trends in reactivity with catalyst variation suggest that the carbon micropore content and acidity are determining factors in the catalgic activity
TL;DR: In this paper, the conversion of a solid copolymer into a ceramic was studied in the 20-1450°C temperature range under different atmospheres (inert or oxidative) and the implications of these observations to the pyrolysis mechanism are discussed.
Abstract: The conversion of a solid copolymer (ViSiHNH)x─(MeSiHNH)y into a ceramic was studied in the 20–1450°C temperature range under different atmospheres (inert or oxidative). The ceramic yield, the ceramic composition, and the gaseous evolution directly depend on the heating rate, the pyrolysis atmosphere, and the duration of pyrolysis. The implications of these observations to the pyrolysis mechanism are discussed. The silicon carbonitride obtained after pyrolysis is amorphous up to 1400°C with high carbon content. It will be shown in Parts II and III that either SiC or Si3N4 could be selectively crystallized depending upon processing conditions.
TL;DR: In this article, the thermal decomposition of Avicel cellulose was studied by non-isothermal differential scanning calorimetry in hermetically sealed sample holders and the experimental results showed a marked catalytic effect of the water on the cellulose decomposition.
Patent•
09 Mar 1993
TL;DR: In this paper, a process for the production of anhydrosugars such as levoglucosan (1,6-anhydro-β-Dglucopyranose), from liquids obtained by the fast thermal pyrolysis of pretreated lignocellulosics or celluloses is described.
Abstract: A process is described for the production of anhydrosugars such as levoglucosan (1,6-anhydro-β-D-glucopyranose), from liquids obtained by the fast thermal pyrolysis of pretreated lignocellulosics or celluloses. In this process, the pyrolytic liquids containing the anhydrosugars are produced with a substantially reduced amount of lignin-derived components by using as feedstock materials which have been previously delignified and then pretreated, or by preferential oxidation of the lignin fraction of a pretreated biomass during pyrolysis. The preparation from pretreated biomass of pyrolytic liquors from which the lignin derived chemical products of fast pyrolysis are absent or in low concentrations permits simpler and more economical recovery of crystalline levoglucosan and other anhydrosugars, or a more economical preparation of readily fermentable aqueous sugar solutions therefrom. A new procedure for the recovery of crystalline levoglucosan from such solutions is described.
TL;DR: In this paper, a Du Pont differential scanning calorimeter (DCS) and thermogravimetric analyzer (TGA) were used to characterize pyrolysis and combustion properties of two heavy crude oils.
TL;DR: In this paper, a variety of oxide-based catalysts have been prepared, characterised, and tested in the oxidative dehydrogenation reaction and it has been found that with these catalysts, the maximum selectivity to propene at a specific conversion of propane is never higher than can be obtained in the absence of a catalyst.
Abstract: The pyrolysis and the oxidative dehydrogenation of propane have been investigated in a quartz reactor. It has been found that by optimising the propane/air ratio it has been possible to obtain very high yields of propene and ethene. A variety of oxide-based catalysts have been prepared, characterised, and tested in the oxidative dehydrogenation reaction. It has been found that with these catalysts, the maximum selectivity to propene at a specific conversion of propane is never higher than can be obtained in the absence of a catalyst. The results also show no obvious correlation between catalytic properties and the presence of specific crystalline phases. It is suggested that lower than optimum selectivities to propene may arise because of the presence in the catalysts of small, but undetected, amounts of pure V 2 O 5 . Comparison with other published work suggests that there is an upper limit on the yield of propene which can be obtained for a purely heterogeneously catalysed reaction. A combination of homogeneous and heterogeneous contributions to the oxidative dehydrogenation reaction may provide a means of obtaining even higher yields of propene.
TL;DR: In this paper, a system was developed for producing high yields of a biomass rich in proteins and low in polymeric carbohydrates from the halophilic alga Dunaliella grown in saline water.
TL;DR: In this paper, experiments were conducted burning aerosol of poly(styrene), poly(methyl methacrylate), and poly(vinyl chloride) particles, in size cuts in the range of 150-300 μm.
Abstract: Polynuclear aromatic hydrocarbon (PAH) emissions from the combustion of selected synthetic polymers (plastics), commonly found in municipal solid waste streams, were monitorsd using bench-scale furnaces. Experiments were conducted burning aerosol of poly(styrene), poly(ethylsns), poly(propylene), poly(methyl methacrylate), and poly(vinyl chloride) particles, in size cuts in the range of 150-300 μm. Most experiments involved dilute dispersions of polymer particles free-falling in a drop-tube laminarflow furnace, at gas temperatures of 750-1150 o C and residence times of 0.5-2 s in air. Upon melting and pyrolysis, the polymer particles burned with luminous envelope flames, whose temperature and duration were measured pyrometrically in the near infrared