Showing papers on "Pyrolysis published in 1996"
TL;DR: In this paper, the authors used both a thermogravimetric analyser and a packed-bed pyrolyser to investigate the relationship between pyrolyses of isolated biomass components and the composition of the biomass.
673 citations
TL;DR: In this paper, the slow pyrolysis of biomass in the form of pine wood was investigated in a static batch reactor at pyrolysisation temperatures from 300 to 720°C and heating rates from 5 to 80 K min−1.
549 citations
TL;DR: In this article, a mixture of mixed wood waste was pyrolysed in a fluidized bed reactor at 400, 450, 500 and 550°C, and the results showed that only low quantities of hydrocarbons were present and the oxygenated and polar fractions were dominant.
419 citations
TL;DR: In this article, the kinetics of the thermal conversion of aromatic hydrocarbons in the presence of hydrogen and steam were studied, using anphthalene, toluene and benzene as model compounds.
372 citations
TL;DR: In this paper, a series of nine large-scale, open fires was conducted in the Intermountain Fire Sciences Laboratory (IFSL) controlled-environment combustion facility, and mid-infrared spectra of the smoke were recorded throughout each fire by open path Fourier transform infrared (FTIR) spectroscopy at 0.12 cm−1 resolution over a 3 m cross-stack pathlength and analyzed to provide pseudocontinuous, simultaneous concentrations of up to 16 compounds.
Abstract: A series of nine large-scale, open fires was conducted in the Intermountain Fire Sciences Laboratory (IFSL) controlled-environment combustion facility. The fuels were pure pine needles or sagebrush or mixed fuels simulating forest-floor, ground fires; crown fires; broadcast burns; and slash pile burns. Mid-infrared spectra of the smoke were recorded throughout each fire by open path Fourier transform infrared (FTIR) spectroscopy at 0.12 cm−1 resolution over a 3 m cross-stack pathlength and analyzed to provide pseudocontinuous, simultaneous concentrations of up to 16 compounds. Simultaneous measurements were made of fuel mass loss, stack gas temperature, and total mass flow up the stack. The products detected are classified by the type of process that dominates in producing them. Carbon dioxide is the dominant emission of (and primarily produced by) flaming combustion, from which we also measure nitric oxide, nitrogen dioxide, sulfur dioxide, and most of the water vapor from combustion and fuel moisture. Carbon monoxide is the dominant emission formed primarily by smoldering combustion from which we also measure carbon dioxide, methane, ammonia, and ethane. A significant fraction of the total emissions is unoxidized pyrolysis products; examples are methanol, formaldehyde, acetic and formic acid, ethene (ethylene), ethyne (acetylene), and hydrogen cyanide. Relatively few previous data exist for many of these compounds and they are likely to have an important but as yet poorly understood role in plume chemistry. Large differences in emissions occur from different fire and fuel types, and the observed temporal behavior of the emissions is found to depend strongly on the fuel bed and product type.
353 citations
TL;DR: In this paper, the thermochemical behavior of pine wood and its main structural constituents (cellulose, hemicelluloses, and lignin) was investigated by pyrolysis-gas chromatography with mass-selective detection (Py-GC/MSD).
337 citations
TL;DR: In this paper, the thermochemistry of cellulose pyrolysis has been studied by a combination of differential scanning calorimetry and thermogravimetric analysis, and the vapor pressure and heat of vaporization of levoglucosan have been determined by an effusion method.
Abstract: The thermochemistry of cellulose pyrolysis has been studied by a combination of differential scanning calorimetry and thermogravimetric analysis. Additionally, the vapor pressure and heat of vaporization of levoglucosan have been determined by an effusion method. The cellulose pyrolysis has been carried out under inert gas at heating rates from 0.1 to 60 K/min. The main cellulose thermal degradation pathway is endothermic, in the absence of mass transfer limitations that promote char formation. The endothermicity is estimated to be about 538 J/g of volatiles evolved. It is concluded that this endothermicity mainly reflects a latent heat requirement for vaporizing the primary tar decomposition products. Pyrolysis can be driven in the exothermic direction by char-forming processes that compete with tar-forming processes. The formation of char is estimated to be exothermic to the extent of about 2 kJ/g of char formed. Low heating rates, in concert with mass transfer limitations, serve to drive the pyrolysis ...
307 citations
TL;DR: In this article, the effects of heating rate, temperature, particle size and residence time on the product distribution, gas composition and char reactivity in a free-fall pyrolysis of biomass, wood and agricultural residues were investigated.
278 citations
Enel1
TL;DR: In this paper, a simple laboratory apparatus was used to obtain the pyrolysis products of the biomass samples, allowing a small amount of oil to be collected for thermogravimetric evaluation of its quality.
250 citations
TL;DR: In this paper, the authors compared the performance of a vacuum pyrolysis and an inert purging method on a polyimide precursor material and found that the purging process produced more selective but less productive carbon molecular sieve membranes.
Abstract: In previous research, carbon molecular sieve (CMS) membranes for gas separations have been produced using either a vacuum pyrolysis or an inert purge pyrolysis technique on a precursor which is often polymeric. This study compares both techniques using the same polyimide precursor material. Additional pyrolysis variables included the type of “inert” purge gas (argon, helium, and carbon dioxide), purge flow rate, and temperature. Vacuum pyrolysis produced more selective but less productive CMS membranes than the inert purge pyrolyzed membranes. “High” purge gas flow rates (i.e., 200 standard cubic centimeters per minute or cm3(STP)/min) produced a much higher permeability, but lower selectivity membrane compared to those produced in a “low” purge flow rate (20 cm3(STP)/min). By raising the pyrolysis temperature from 550 to 800 °C, the effective pore size was reduced, thereby making the CMS membranes more selective but less productive. Mixed gas tests using oxygen/nitrogen and hydrogen/nitrogen mixtures wer...
241 citations
TL;DR: In this article, the authors experimented with sequential cold filtering of biocrude oils using filters of varying pore size and found that most of the ash and alkali metals detected in biocarriers are trapped in the chars.
Abstract: Inorganic compoundsespecially potassium, calcium, sodium, silicon, phosphorus, and chlorineare the main constituents of the ash in biomass feedstocks. The concentrations of ash range from less than 1% in softwoods to 15% in herbaceous biomass and agricultural residues. During biomass pyrolysis, these inorganics, especially potassium and calcium, catalyze biomass decomposition and char-forming reactions. Chars formed during these reactions invariably end up in the biomass pyrolysis oils (biocrude oils) as suspended submicron particles. The presence of high concentrations of submicron char particles in biocrude oils will make them problematic for combustion in steam boilers, diesel engines, and turbine operations because of the potential release of the ash and alkali metals during combustion. We experimented with sequential cold filtering of biocrude oils using filters of varying pore size and this revealed that most of the ash and alkali metals detected in biocrude oils are trapped in the chars. Leaching s...
TL;DR: In this article, the coupled effects of particle size and external heating conditions (reactor heating rate and final temperature) on cellulose pyrolysis were investigated by means of a computer model accounting for all main transport phenomena, variable thermophysical properties and primary, and secondary reaction processes.
Abstract: The coupled effects of particle size and external heating conditions (reactor heating rate and final temperature) on cellulose pyrolysis are investigated by means of a computer model accounting for all main transport phenomena, variable thermophysical properties and primary, and secondary reaction processes. The dynamics of particle conversion are predicted, and final product distributions are favorably compared with experimental measurements. A map is constructed, in terms of particle size as a function of the reactor temperature, to identify the transition from a kinetically controlled conversion to a heat transfer controlled conversion (thermally thin and thermally thick regimes) and from flash to slow-conventional pyrolysis. Conditions for maximizing oil, gas, or char yields are also discussed.
TL;DR: In this paper, the authors used a fixed-bed microreactor interfaced with a molecular beam mass spectrometer (MBMS) to study the catalytic steam reforming of model oxygencontaining compounds present in biomass pyrolysis vapors.
Abstract: Biomass can be pyrolytically converted in high yields (∼ 70 wt.%) into vapors (or oils when condensed) composed mainly of oxygenated organic compounds. Using a fixed-bed microreactor interfaced with a molecular beam mass spectrometer (MBMS), we have been studying the catalytic steam reforming of model oxygen-containing compounds present in biomass pyrolysis vapors. This MBMS sampling system is unique in its rapid, real-time, and universal detection of gaseous and condensible products. In this paper, we present results for steam reforming of acetic acid (HAc) and hydroxyacetaldehyde (HAA), two major products derived from the pyrolysis of carbohydrates in biomass. We propose mechanisms to couple the thermal decomposition and steam reforming reactions of these compounds. Both HAc and HAA undergo rapid thermal decomposition; complete steam reforming of these two model compounds can be achieved with commercial Ni-based catalysts. HAc forms coke on the catalyst surface, which is subsequently gasified by steam. The proposed mechanism for this coke formation involves an adsorbed acetate species that decar☐ylates to form the coke precursor, (CH 1–3 ) abs , and also ketene, a dehydration product of HAc, that decomposes to form (CH 1,2 ) abs . The reforming of HAA by steam does not involve any detectable intermediate and proceeds smoothly to a complete breakdown to CO and H 2 on the catalyst surface.
TL;DR: In this article, the heating values of various types of biomass components and their pyrolysis products such as char, liquids and gases are presented, and correlations are developed to express these.
TL;DR: In this paper, the pyrolysis of olive and grape bagasse has been studied with the aim of determining the main characteristics of the charcoals formed and the nature and quantity of gases and liquids produced.
Abstract: The pyrolysis of olive and grape bagasse has been studied with the aim of determining the main characteristics of the charcoals formed and the nature and quantity of gases and liquids produced. Variables investigated were temperature between 300 and 900°C and particle size between 0.4 and 2 mm diameter. Experiments were carried out in an isothermal manner. As a general rule, particle size does not exert any influence, whereas temperature is a very significant variable. Thus an increase in this variable yields an increase in the fixed carbon content, gases produced and, to a lesser extent, ash percentage. On the other hand, volatile material and solid yields decrease with increasing temperature. The principal gases generated are H2, CH4, CO and CO2, while among the liquid components the presence of methanol, acetone, furfuryl alcohol, phenol, furfural, naphthalene and o-cresol has to be highlighted. Heating values of both gas and solid phases were determined from gas composition and elemental carbon analysis. The quality of charcoals and heating value allow the conclusion that the most convenient temperature for the pyrolysis should be between 600 and 700°C, at which the production of liquids is at its maximum. Finally, a kinetic study of the pyrolysis, based on gas generation from thermal decomposition of residues, has been carried out. From this model, rate constants for the formation of each gas and their corresponding activation energies were determined.
TL;DR: In this article, a flame spray pyrolysis of alcoholic solutions of a double alkoxide precursor was used to produce ultrafine crystalline spinel powder with particle formation by rapid oxidation of the organic ligands followed by nucleation and growth from oxide species.
Abstract: Ultrafine crystalline spinel powder has been prepared using flame spray pyrolysis of alcoholic solutions of a novel double alkoxide precursor. The particles produced are spherical, dense, single crystals with diameters of 10--100 nm and specific surface areas ranging from 40 to 60 m{sup 2}/g. Powder production rates of 50--100 g/h are achieved using a bench-top apparatus. Particle formation appears to occur by rapid oxidation of the organic ligands followed by nucleation and growth from oxide species.
TL;DR: In this article, a pyrolysis temperature of 700 °C yields activated carbons with a wider pore size distribution than those prepared at 500 °C, and the use of an activating agent/coal ratio of 2/1 compared to 1/1 has favorable effects.
Abstract: Activated carbons from Spanish coals have been prepared by chemical activation with alkali and alkaline-earth hydroxides. The paper analyzes the following aspects: presence of water during pyrolysis, extension of the impregnation and drying processes, activating agent, temperature and time of pyrolysis, activating agent/coal ratio, coal rank, and mineral matter content. KOH and NaOH activation provides very successful results in which N2 apparent surface areas of 2500 m2/g are obtained; contrarily, Ca(OH)2 produces a small porosity development. A pyrolysis temperature of 700 °C yields activated carbons with a wider pore size distribution than those prepared at 500 °C. The pyrolysis time does not affect the microporosity development but an important reduction in the ash content is observed when the time is increased. The use of an activating agent/coal ratio of 2/1 compared to 1/1 has favorable effects: (i) a decrease in the ash content and (ii) a wider pore size distribution. The addition of a drying st...
TL;DR: In this paper, a numerical model for endothermic biomass pyrolysis, which includes both high activation energy kinetics and heat transfer across a boundary layer to the reacting solid particle, is presented.
Abstract: Results from a numerical model for endothermic biomass pyrolysis, which includes both high activation energy kinetics and heat transfer across a boundary layer to the reacting solid particle, are presented. The model accounts for conventional thermocouple thermal lag and unconventional thermal lag due to heat demand by the chemical reaction (which is governed by Arrhenius kinetics). Biomass fusion, first identified quantitatively by Lede and Villermaux, is shown to be a manifestation of severe thermal lag that results from the chemical reaction heat demand. Over the wide range of conditions studied, the true substrate temperature remains almost constant during pyrolysis, as is the case with compounds undergoing fusion or sublimation at constant pressure. A simple algebraic model, whose derivation presupposes the idea that biomass pyrolysis mimics the melting of a block of ice, accurately predicts the maximum value of thermal lag during pyrolysis. Unidentified thermal lag in TGA experiments lowers the valu...
TL;DR: In this article, pyrolyzed sugar carbons are used as anode materials in Li-ion batteries. But the performance of these carbons depends on the pyrosis temperature, heating rate, argon gas flow rate, and morphology of the precursors.
Abstract: Table sugar was pyrolyzed under various conditions. Carbons of pyrolyzed sugar demonstrated high capacity for Li intercalation, exceeding that of graphite. Experiments were carried out to search for optimal pyrolyzing conditions. The electrochemical behavior of these carbons was found to depend on the pyrolysis temperature, heating rate, argon gas flow rate, and morphology of the precursors. Pyrolysis of sugar was also carried out under vacuum, which is equivalent to a high argon gas flow. Carbons of pyrolyzed sugar under optimal conditions showed large reversible capacity, {approx} 650 mAh/g, small irreversible capacity, {le} 170 mAh/g, and small hysteresis between discharge and charge in carbon/Li metal electrochemical test cells. Pyrolyzed sugar carbons are therefore potential candidates as anode materials in Li-ion batteries.
TL;DR: The most important structure modifications appeared between 300 and 400 °C, and they are characterized by the decrease of intensities of C O and C C C bands and the formation of alkyl bands as discussed by the authors.
TL;DR: In this article, the pyrolytic behavior of three different kinds of solid fuel and their blends in order to understand and further improve the performance of fluidized bed gasification of biomass-poor coal blends was reported.
TL;DR: In this article, the thermal analysis of polyamides modified with magnesium hydroxide fire retardant filler is studied using combined TGA, DSC EGA and on-line FTIR techniques.
TL;DR: In this article, two approaches were employed to reveal the pyrolysis reactions: one is an analysis of evolved compounds, the other is a hydrolysis method that selectively converts polyimide char into low-molecular-weight compounds.
TL;DR: This study constitutes the first comprehensive chemical characterization of the pyrolysis products of invertebrate cuticles and provides the basis for future investigations requiring qualitative screening for cross-linked chitin and proteins in modern and fossil cuticle and in materials, e.g. geopolymers, that may be derived from them.
Abstract: Flash pyrolysis/gas chromatography (py/GC) and py/GC/mass spectrometry (MS) have been utilized to characterize the cuticles of invertebrates chemically. Pyrolysis products have been identified and assigned to specific cuticular components. Acetylpyridones, acetamidofuran, 3-acetamido-5-methylfuran and 3-acetamido-(2 and 4)-pyrones are proposed as characteristic pyrolysis markers for chitin. Pyrolysis products displaying ions of m/z 70, 154, 168, 194 are thought to derive from diketopiperazine structures and provide potential markers for proteins and peptides in which proline, alanine, valine, arginine and glycine are the dominant amino acids. These products, constituting specific pyrolysis markers for invertebrate cuticles, may reflect the amino acid composition of their constituent structural proteins. The source of the various pyrolysis products of proteins has been verified by pyrolysis of reference proteins, peptides and amino acid mixtures. The presence of additional pyrolysis products related directly to histidine and catechol moieties is consistent with the chemical structure and composition proposed for arthropod cuticles based on recent work utilizing solid state 13C and 15N nuclear magnetic resonance. This study constitutes the first comprehensive chemical characterization of the pyrolysis products of invertebrate cuticles and provides the basis for future investigations requiring qualitative screening for cross-linked chitin and proteins in modern and fossil cuticles and in materials, e.g. geopolymers, that may be derived from them.
TL;DR: In this paper, pyrolysis vapours were upgraded by passing them over a fixed bed of ZSM-5 zeolite catalyst, which was diluted with stainless steel ball bearings.
TL;DR: In this paper, improved experimental techniques are described, using a wire mesh reactor, for determining the pyrolysis yields of lignocellulosic materials in this apparatus pyrolyssis tars are rapidly swept from the hot zone of the reactor and quenched, secondary reactions are thereby greatly diminished.
Abstract: Improved experimental techniques are described, using a wire mesh reactor, for determining the pyrolysis yields of lignocellulosic materials In this apparatus pyrolysis tars are rapidly swept from the hot zone of the reactor and quenched, secondary reactions are thereby greatly diminished Particular emphasis is placed upon the measurement of the pyrolysis yields for sugar cane bagasse, an abundant agricultural waste product The role of the important pyrolysis parameters, peak temperature and heating rate, in defining the ultimate tar yield is investigated, with the value for bagasse being 546% at 500 °C and 1000 °C/s The pyrolysis yields, under similar conditions, of another biomass material, silver birch, are also reported and compared to those of bagasse
TL;DR: In this article, noncrystalline solids with LiCoC6H5O7·5H2O and (NH4)3LiCo(C 6H 5O7)2 compositions were obtained by ethanol dehydration of concentrated lithium−cobalt citrate solutions.
Abstract: Noncrystalline solids with LiCoC6H5O7·5H2O and (NH4)3LiCo(C6H5O7)2 compositions were obtained by ethanol dehydration of concentrated lithium−cobalt citrate solutions. Electron spectroscopy of solut...
TL;DR: In this article, the authors used temperature-programmed desorption (TPD) to determine the nature and extent of carbon-oxygen (CO) complexes formed on the char surface.
TL;DR: In this article, the thermally induced interrelation between total tar, chemical distribution of principal tar constituents and the three C2 compounds (ethane, ethene, ethyne) obtained from wood pyrolysis at atmospheric pressure in a continuous bench-scale fixed bed reactor was investigated.
TL;DR: In this article, a new method for the automated sample preparation and on-line isotope ratio determination of organic compounds is presented, based on sudden pyrolysis in a helium carrier stream at a temperature of 1080 °C in the absence of surplus carbon.