Showing papers on "Pyrolysis published in 1979"

A kinetic model for pyrolysis of cellulose.

Abstract: It has been shown that the pyrolysis of cellulose at low pressure (1.5 Torr) can be described by a three reaction model. In this model, it is assumed that an “initiation reaction” leads to formation of an “active cellulose” which subsequently decomposes by two competitive first-order reactions, one yielding volatiles and the other char and a gaseous fraction. Over the temperature range of 259–341°C, the rate constants of these reactions, ki (for cellulose → “active cellulose”), kv (for “active cellulose” → “volatiles”), and kc (for “active cellulose” → char + the gaseous fraction) are given by ki = 1.7 × 1021e− (58,000/RT) min −1, kv = 1.9 × 1016e− (47,300/RT) min−1, and kc = 7.9 × 1011e− (36,600/RT) min−1, respectively.

Thermal degradation of cellulose in air and nitrogen at low temperatures

Abstract: Thermal analysis and kinetic studies have shown that oxidative reactions are responsible for acceleration in the rates of weight loss and depolymerization of cellulose on pyrolysis in air at temperatures below 300°C. The oxidative reactions include production of hydroperoxide, carbonyl, and carboxyl groups, which have been investigated at lower temperatures along with the rates of depolymerization and production of carbon monoxide and carbon dioxide. The experimental results are consistent with an autoxidation mechanism involving initiation, propagation, and decomposition reactions. At temperatures above 300°, the rate of pyrolysis is essentially the same in both air and nitrogen, indicating that thermal degradation is independent of the oxidative reactions.

Low temperature synthesis of a monolithic silica glass by the pyrolysis of a silica gel

Abstract: The reaction process in the pyrolysis of silica gel has been investigated as the basic study on the low temperature synthesis of monolithic glass from a metal alkoxide. A large volume change which may cause stress-induced fracture of a gel occurred in the following process stages: (a) the decompostion of residual organic compounds into carbon dioxide (300 to 500° C); (b) small pore collapse (400 to 500° C); (c) larger pore collapse (700 to 900° C). A fracture-free monolithic silica glass was successfully prepared from a dry silica gel formed by the hydrolysis of silicon methoxide by careful heat-treatment. The properties of the synthetic silica glass were similar to those of commercial vitreous silica.

Process for recovering carbon black and hydrocarbons from used tires

Abstract: The invention is a process for economically recovering carbon black, oil and fuel gas from used tires. Used tires are physically fragmented. The fragments are pyrolized at slightly subatmospheric pressure in a reactor while process char is being recycled to increase heat transfer and avoid coke on heat transfer surfaces. Entrained char is separated from the vapor phase products of the pyrolysis, and the vapor phase products of the pyrolysis are then fractionated into oil and fuel gas. A preferred embodiment condenses reactor vapors in two stages at two temperature levels to separate dust from an oil-dust mixture, without water in the first stage and light oil in the second stage. The fuel gas can be compressed and burnt to provide process heat. The entrained char dust and some heavy oil is returned to the reactor. Solid phase pyrolysis products are stripped of trash and milled to carbon black. Carbon black is mechanically separated from the effluent air stream of the mill and formed into pellets with added water and dried.

Pyrolysis of a Precipitated Kraft Lignin

Abstract: A precipitated kraft lignin was pyrolyzed in a "captive sample" reactor at 400-700 °C for 10-120 s. Weight loss and tar were determined gravimetrically and oxides of carbon, hydrocarbons, methanol, acetone and single-ring phenols were determined by gas chromatography. The single-ring phenols (phenol, guaiacol, etc.), which are the most valuable among the products, were obtained at yields up to 3% of the original dry lignin.

Preparation of porous carbon

Abstract: Porous carbon, suitable for instance for chromatography and as a catalyst support is formed by depositing carbon into the pores of a porous inorganic template such as silica gel, porous glass or a porous oxide, e.g. alumina, and thereafter removing the template as by dissolution or evaporation. Carbon is preferably deposited as a polymerizable organic material that is polymerized in situ in the template pores and then pyrolyzed to carbon.

Thermal decomposition of poly(butylene terephthalate)

Abstract: Detailed results of the overall thermal degradation of poly(butylene terephthalate) are reported. Laser microprobe analysis and dynamic mass spectrometric techniques were used to identify the primary volatile degradation products and initial pyrolysis reactions that control polymer degradation. A complex multistage decomposition mechanism was observed which involves two major reaction pathways. Initial degradation occurs by an ionic decomposition process that results in the evolution of tetrahydrofuran. This is followed by concerted ester pyrolysis reactions that involve an intermediate cyclic transition state and yield 1,3-butadiene. Simultaneous decarboxylation reactions occur in both decomposition regimes. Finally, the latter stages of polymer decomposition were characterized by evolution of CO and complex aromatic species such as toluene, benzoic acid, and terephthalic acid. Activation energies of formation for the main pyrolysis products were determined from the dynamic measurements of the major ion species and indicate values of E = 27.9 kcal/mole for the production of tetrahydrofuran and E = 49.7 kcal/mole for the production of butadiene.

Apparatus for solid waste pyrolysis

Abstract: This disclosure is directed to an economical system for the pyrolysis of municipal solid waste to recover valuable by-products while reducing the putrecibility and bulk of the residue requiring disposal. Prior to this treatment, the solid waste has been processed to remove most of the metallic components, and shredded, which steps are not part of the invention disclosed. The pyrolysis and by-product recovery technology is complicated by (a) the inherent variability of the chemical and physical characteristics of the shredded solid waste as received at the pyrolysis plant and (b) the relatively low heat value of said waste as thus received. This pyrolysis and product recovery system includes an improved pyrolysis retort indirectly heated principally by combustion of the least desirable by-product, the solid char, in combination with a furnace for the char combustion, a condenser for the pyrolysis vapor including means for gravity separation of the gas, liquid and solid residues entrained therein, and improved means for conveying the materials through the system including intermittently driven rams for delivering solids into the retort and furnace.

Hydrocarbon cracking catalyst and process utilizing the same

Abstract: A hydrocarbon cracking catalyst comprises an ultrastable Y-type crystalline zeolite, a small pore crystalline zeolite such as mordenite, an inorganic oxide matrix and, optionally, a porous inert component. The cracking catalyst has a high activity and selectivity for the production of high octane naphtha fractions from higher boiling point hydrocarbonaceous oils. Catalytic cracking processes utilizing the catalyst are also provided.

Fluid catalytic cracking of heavy petroleum fractions

Abstract: A process for (i) fluid catalytic cracking in a cracking zone of residuum and other heavy oils comprising gas oil, petroleum residue, reduced and whole crudes, and shale oils with high metals content, (ii) wherein the coke deposits on the used cracking catalyst are reduced in amount by regeneration and wherein (iii) contaminant metals comprising nickel, vanadium, copper and iron deposited on the used cracking catalyst are deactivated in sufficient amount to reduce hydrogen and coke formation during the cracking process whereby the said catalyst is suitable for re-use wherein (A) the catalyst particles are contacted with fresh feed and associated recycle feed, and wherein (B) the feed is cracked in a cracking zone, wherein (C) the used catalyst particles are subjected to alternate exposures of up to 30 minutes in duration of conditions comprising (a) an oxidizing zone at a temperature of above 900° F. wherein molecular oxygen in flue gas emitted from the oxidizing zone is over 0.1 volume percent, and (b) a reducing zone at a temperature within the range of from about 900° F. to about 1450° F., wherein the reducing atmosphere is a material selected from the group consisting of hydrogen, hydrocarbons, carbon monoxide, and mixtures thereof and is present in a concentration of from about 4 to 100 volume percent, and wherein (D) the regenerated catalyst can be returned to the cracking zone.

Formation of fine silicon carbide powders by a vapor phase method

Abstract: The formation of silicon carbide powders by the vapor phase reaction of SiCl4 + CH4 (1400–1500°C), CH3SiCl3 (800–1400°C) and (CH3)4Si (800–1400°C) was studied. The effectiveness of the silicon sources was in the sequence (CH3)4Si > CH3SiCl3 > SiCl4, in accordance with the thermodynamic parameters. Fine β-SiC powders were produced by the pyrolysis of (CH3)4Si in hydrogen above 900°C. The crystallinity of the products increased with increasing reaction temperature. The particles were spherical and had average sizes of 0.02–0.12μm which decreased with increasing reaction temperature and with decreasing (CH3)4Si concentration. A reaction process consisting of the formation of particles of organosilicon polymers and their subsequent decomposition was proposed for the formation of SiC particles by the pyrolysis of (CH3)4Si.

Steam cracking of hydrocarbons 1. Pyrolysis of heptane

Abstract: The thermal decomposition of heptane in the presence of steam was studied in a flow reactor with large inner surface. The experiments were performed at atmospheric pressure in a temperature range of 680-760 OC for a mass ratio of steam to hydrocarbon 3:l. The reaction products were analyzed by gas chromatography. For the identification both comparison of retention indices with those of standard compounds and literature data and mass spectrometry were used. The conversion process appeared to be a first-order reaction with a frequency factor of 1.34 X 10'' s-' and an activation energy of 195.5 kJ mol-'. The composition of the mixture of reaction products was in agreement with the Rice-Kossiakoff theory, except for ethane and 1-hexene.

Pyrolysis of benzene

Abstract: The gas phase pyrolysis of benzene was studied in a static system in the range 873–1036 K. The reaction is largely homogeneous, of order 1.5 and involves free radicals. The products are diphenyl and hydrogen. The Arrhenius plot curves slightly at lower temperatures, but at higher temperatures the rate may be represented by d[h2]/dt=k[c6H6]. where k= 109.83 exp (–225 kJ mol–1/RT) dm mol–½ s–1.The results are interpreted in terms of a simple chain reaction and compared with the results and mechanisms of other workers. The simple mechanism represented the results as well, if not better, than the more complicated mechanisms which have been proposed.Above 1036 K, ring opening occurs and acetylene, ethylene, methane and carbon are formed. A range of polyphenyls and polynuclear aromatic hydrocarbons were detected on the carbon and may be intermediates in soot formation.

Removal of particulates from pyrolytic oil

Abstract: A process for producing organic liquid product from solid organic waste. The process comprises pyrolyzing the solid organic waste to produce pyrolysis vapors and solid pyrolysis residue. The solid residue is separated from the pyrolysis vapors leaving entrained particulate matter in the vapor. At least a portion of the pyrolysis vapor is condensed for producing pyrolysis liquid containing entrained particulate matter. The pyrolysis liquid is centrifuged producing a light fraction containing entrained particulate matter, a middle fraction substantially free of particulate matter and a heavy fraction containing entrained particulate matter. The middle fraction is recovered as organic liquid product substantially free of entrained particulate matter. The light fraction and heavy fraction are mixed and filtered. The liquid filtrate produced is distilled for producing additional organic liquid product.

Apparatus for converting organic material into fuel

Abstract: The apparatus includes a pyrolytic reactor in which an initial charge of charcoal is located. An inlet is provided for introduction of the organic material and an exit is provided for the resulting gases and ash products. The reactor is arranged to permit a continuous flow of organic material volatiles, and char through the reactor, resulting in continual replenishment of organic material in the pyrolizing portion of the reactor, and replenishment of the charcoal bed portion by the char produced from the pyrolysis reaction. The reactor vessel is heated to the correct temperatures by means such as electric heating coils or hot air/flame jackets.