Showing papers on "Pyrolysis published in 2003"

Oxygen Reduction Catalysts for Polymer Electrolyte Fuel Cells from the Pyrolysis of Iron Acetate Adsorbed on Various Carbon Supports

Abstract: Nonnoble metal catalysts for the electrochemical reduction of oxygen in acidic medium have been produced by adsorbing iron(II) acetate on 19 carbon supports. These materials were then pyrolyzed in an atmosphere containing NH3. The 19 carbon supports are (i) six as-received commercial supports (Printex XE-2, Norit SX Ultra, Ketjenblack EC-600JD, acetylene black, Vulcan XC-72R, and Black Pearls 2000), (ii) three as-received developmental supports (Lonza HS300 and Sid Richardson RC1 and RC2), (iii) the same nine previous supports prepyrolyzed at 900 °C in an atmosphere containing NH3 to increase their N content, and (iv) a synthetic carbon made by pyrolyzing perylene tetracarboxylic dianhydride at 900 °C in an atmosphere containing NH3. The goal of this study is to determine the effect of the carbon support on the catalytic activity of the catalysts. The specific surface area, the pore size distribution, the N and O contents, and the electrocatalytic activities of the 19 types of catalysts were measured. It ...

GC/MS characterization of liquids generated from low-temperature pyrolysis of wood

Abstract: Conventional pyrolysis of beech wood has been carried out for heating temperatures in the range 600−900 K, reproducing conditions of interest in countercurrent fixed-bed gasification. The yields of liquids (water and tars) increase with the heating temperature from about 40 to 55% of dry wood mass, confirming results previously obtained with a laboratory-scale gasifier. Apart from qualitative identification of ∼90 species, GC/MS techniques have been applied to quantify 40−43% of tars (40 species, with major contributions from acetic acid, hydroxypropanone, hydroxyacetaldehyde, levoglucosan, formic acid, syringol, and 2-furaldehyde). Decomposition of holocellulose leads to the formation of furan derivatives and carbohydrates, with a temperature-dominated selectivity toward hydroxyacetaldehyde against levoglucosan. Syringols and guaiacols, originating from primary degradation of lignin, present a maximum for heating temperatures of about 750−800 K whereas, owing to secondary degradation, phenols continuousl...

Sorption hysteresis of benzene in charcoal particles.

Abstract: Charcoal is found in water, soil, and sediment where it may act as a sorbent of organic pollutants. The sorption of organic compounds to natural solids often shows hysteresis. The purpose of this study was to determine the source of pronounced hysteresis that we found in the sorption of a hydrophobic compound (benzene) in water to a maple-wood charcoal prepared by oxygen-limited pyrolysis at 673 K. Gas adsorption (N2, Ar, CO2), 13C NMR, and FTIR show the charcoal to be a microporous solid composed primarily of elemental (aromatic) C and secondarily of carboxyl and phenolic C. Nonlocal density functional theory (N2, Ar) and Monte Carlo (CO2) calculations reveal a porosity of 0.15 cm3/g, specific surface area of 400 m2/g, and appreciable porosity in ultramicropores <10 A. Benzene sorption−desorption conditions were chosen to eliminate artificial causes of hysteresis (rate-limiting diffusion, degradation, colloids effect). Charcoal sorbed up to its own weight of benzene at ∼69% of benzene water solubility. S...

Fast Pyrolysis of Forestry Residue. 3. Storage Stability of Liquid Fuel

Abstract: The storage properties of fuels are critical in regard to the introduction of a new fuel into markets. The fuel must be homogeneous, and the properties of the fuel should not change significantly during the storage at the customer's facility. In this research, the storage stability of wood-based pyrolysis liquids was followed by analysis of the changes in the physical properties and chemical composition during storage. The main physicochemical changes took place during the first six months. The high-molecular-mass (HMM) fraction of water-insolubles, which were originally lignin-derived material, increased, because of polymerization and condensation reactions of carbohydrate constituents, aldehydes, and ketones. Therefore, the average molecular mass of pyrolysis liquids increased, which was also observed as an increase in viscosity. There was a clear correlation of the average molecular mass with the viscosity, water-insolubles, and the HMM fraction of water-insolubles. The chemical changes in the aging we...

Key Compounds of the Hydropyrolysis of Glucose in Supercritical Water in the Presence of K2CO3

Abstract: Hydropyrolysis of glucose as a model compound for cellulose in hot compressed water in the presence of K2CO3 at temperatures of 400 and 500 °C and pressures of 30 and 50 MPa in the range of 1.8−16.3 min reaction time is conducted to characterize key compounds of the thermochemical conversion {phenols (phenol and cresols), furfurals [methylfurfural and (hydroxymethyl)furfural], organic acids, aldehydes}. To compare the effect of alkali salts on the pyrolysis of glucose and biomass, the experiments are conducted in the presence of K2CO3, while biomass includes usually alkali salts. Hydrothermolysis of glucose in the presence of K2CO3 increases the hydrogen yield and the amount of phenols under these conditions. The formation and the degradation pathways of phenols and the other compounds that are identified are discussed. A simplified reaction scheme for glucose decomposition is given and used to discuss the role of these compounds. The effect of varying properties of supercritical water such as density, di...

Pyrolysis behavior of levoglucosan as an intermediate in cellulose pyrolysis: polymerization into polysaccharide as a key reaction to carbonized product formation

Abstract: Pyrolysis behavior of levoglucosan (1,6-anhydro-β-d-glucopyranose), the major anhydromonosaccharide formed during cellulose pyrolysis, was studied at 250°–400°C under nitrogen. The pyrolysis products were found to change stepwise: levoglucosan → MeOH-soluble fraction (lower-molecular-weight products and oligosaccharides) → water-soluble fraction (polysaccharides) → insoluble fraction (carbonized products). From the present experimental results, a pathway of cellulose pyrolysis via anhydromonosaccharide is proposed including polymerization to polysaccharides (a reversible reaction) as a key reaction to carbonized product formation.

Fast Pyrolysis of Forestry Residue. 1. Effect of Extractives on Phase Separation of Pyrolysis Liquids

Abstract: Although high liquid yields of a single phase product can be obtained from bark free “white” wood feedstocks by fast pyrolysis processes, lower yields and a two phase product are obtained from feedstocks containing bark and needles as is commonly found with forestry residues. The liquid yield is thus reduced from levels of 70−75 wt % to those of 60−65 wt %. This will have a significant impact on the economic viability of pyrolysis projects in Scandanavia as forestry residues are a major source of raw materials. The forestry residue product is composed of an extractive rich upper phase which varies from 10 to 20% of the total product and a bottom phase closely resembling the normal bark free wood product. Phase separation occurs due to the higher extractive content of the residues which due to their much lower oxygen phase separate. Extractives are composed of components such as fatty acids, fatty alcohols, terpenes, resin acids, and terpenoids which have lower oxygen content than pyrolysis liquid compound...

Enthalpy for Pyrolysis for Several Types of Biomass

Abstract: This study utilizes a pilot-scale pyrolysis system to determine the enthalpy for pyrolysis for Northern Red Oak (Quercus rubra), Western White Pine (Pinus monticola), corn stover, and oat hulls. The analytical method uses an energy balance on a pyrolytic reactor. The energy required is measured at a fast pyrolysis reactor temperature near 500 °C using nitrogen as an inert fluidizing agent in a fluidized bed reactor. On a dry basis, the energy necessary to pyrolyze these fuels varies between 0.8 ± 0.2 MJ/kg for oat hulls and 1.6 ± 0.3 MJ/kg for pine.