Total Volatile Yield Research Articles

Airborne Compositae dermatitis: monoterpenes and no parthenolide are released from flowering Tanacetum parthenium (feverfew) plants.

The air around intact feverfew (Tanacetum parthenium) plants was examined for the presence of airborne parthenolide and other potential allergens using a high-volume air sampler and a dynamic headspace technique. No particle-bound parthenolide was detected in the former. Among volatiles emitted from the aerial parts of feverfew plants and collected by the dynamic headspace technique a total of 41 compounds, mainly monoterpenes, were identified and quantified by GC and GC-MS. Alpha-Pinene, camphene, limonene, gamma-terpinene, (E)-beta-ocimene, linalool, p-cymene, (E)-chrysanthenol, camphor and (E)-chrysanthenyl acetate were the predominant monoterpenes accounting for nearly 88% of the total volatiles emitted. The average total yield of volatiles emitted over 24 h was 18,160 ng/g fresh weight of leaves and flowers, corresponding to the emission of approximately 8 mg volatiles per day from one full-grown feverfew plant. No parthenolide or other sesquiterpene lactones were detected. The present investigation does not support the theory of airborne sesquiterpene lactone-containing plant parts or of direct release of sesquiterpene lactones from living plants as the only explanations for airborne Compositae dermatitis. Potential allergens were found among the emitted monoterpenes and their importance in airborne Compositae dermatitis is discussed.

Co-pyrolysis and co-gasification of coal and biomass in bench-scale fixed-bed and fluidised bed reactors

Tar and total volatile yields from the co-pyrolysis and co-gasification of coal and biomass samples were described (850°C and 1000°C; up to 25 bar). Two reactors were used: a fixed-bed reactor providing intimate contact between neighbouring fuel particles and a fluidised-bed reactor designed to provide near total segregation of sample particles. In pyrolysis experiments, neither intimate contact between fuel particles, nor their relative segregation appears to lead to synergistic effects. Small differences in tar yields were observed in the fixed-bed reactor when using a combination of Daw Mill coal and silver birch wood. Similar behaviour was observed under CO 2-gasification. However this weak trend appears to be sample dependent, for a second sample set, total volatile yields were about 5% higher than would be expected in the absence of synergistic effects. The differences were systematic and larger than levels of experimental repeatability, but too small to provide information that might explain them. Isothermal combustion reactivities of Daw Mill coal and silver birch wood (mixture) chars prepared at 1000°C, in the fixed-bed reactor, were almost twice as high as those of coal char alone, despite the total gasification of the wood at this temperature. Mineral matter residue from the wood appears to have played a catalytic effect during combustion. When chars were separated with solvent, the effect could not be observed. The analogous effect observed with a second pair of samples was smaller, suggesting that the composition of ashes from different samples play a role. Apart from the catalytic effect of biomass ashes formed at high temperatures, observed synergistic effects were not of a magnitude that might influence process design. No evidence of synergy was found with the fluidised-bed reactor, thereby demonstrating the lack of contact between coal and biomass particles in the system.

Effects of Heating Rate and Ion-Exchangeable Cations on the Pyrolysis Yields from a Victorian Brown Coal

A Victorian low-rank coal (Loy Yang) was acid-washed and ion-exchanged with Na and Ca to prepare the H-form, Na-form, and Ca-form coal samples. Two more H-form samples were also prepared by rewashing the Na-form and Ca-form samples with acid. These coal samples were pyrolyzed in a wire-mesh reactor where the secondary reactions of the evolved volatiles were minimized. The ion-exchanged coal samples were found to give very different tar yields from those of the raw coal samples. While the tar yields from the pyrolysis of the raw and H-form coal samples were observed to be very sensitive to changes in heating rate, the tar yields from the Ca-form and Na-form samples showed little heating rate sensitivity. Unlike higher rank coals studied previously, the tar yields from the pyrolysis of the raw coal and the H-form coal samples at 600 °C were found to increase much more than the corresponding increases in the total volatile yields as the heating rate was increased from 1 to 2000 K s-1. Reexchanging Na in the ...

Hydropyrolysis of sugar cane bagasse: effect of sample configuration on bio-oil yields and structures from two bench-scale reactors

A wire-mesh reactor, with the capability of virtually eliminating secondary reactions, has been used as base-case in the study of product yields and structures from the pyrolysis and hydropyrolysis of a sample of sugar cane bagasse in a fixed-bed `hot-rod' reactor. Results from the two reactors have been compared to determine how best to assess bench-scale data which might be used for eventual process development. Experiments have been carried out at 600°C at pressures up to 70 bar. Structural features of the bio-oils have been examined by size exclusion chromatography and FT-infrared spectroscopy. In both reactors the effect of increasing pressure was to reduce the bio-oil and total volatile yields; hydropyrolysis bio-oil yields were marginally higher than pyrolysis yields under equivalent operating conditions. About 5 to 6% bio-oil product is lost in the fixed-bed reactor, compared with the wire-mesh reactor, with consequent increase in recovered chars. Pressure and reactor bed depth appear to affect only the thermally more sensitive components of the bio-oils, and increasing pressure beyond 40 bar, or bed depth beyond the level reported, was found not to affect yields to an appreciable extent. Taken together, these data indicate that about one-third of the original biomass may be converted to oil by direct pyrolysis. Size exclusion chromatograms and FT-infrared spectra of bio-oils from the hydropyrolysis experiments conducted at 1 and 70 bar suggest that oils from the hot-rod reactor experience a greater degree of secondary reactions than those from the wire-mesh reactor. Using tetrahydrofuran as eluent, the highest molecular masses were found to be around 1000 u in terms of polystyrene standards. However, comparison with size exclusion chromatograms using 1-methyl-2-pyrrolidinone indicated partial loss of sample when operating in THF. Our findings strongly suggest that THF is not a suitable eluent for the characterisation of biomass-derived pyrolysis oils by size exclusion chromatography.

98/03749 Determination of the gasification kinetics of plastics with the aid of an isothermally operating circulating reactor

Tar and total volatile yields from the co-pyrolysis and co-gasification of coal and biomass samples were described (850°C and 1000°C; up to 25 bar). Two reactors were used: a fixed-bed reactor providing intimate contact between neighbouring fuel particles and a fluidised-bed reactor designed to provide near total segregation of sample particles. In pyrolysis experiments, neither intimate contact between fuel particles, nor their relative segregation appears to lead to synergistic effects. Small differences in tar yields were observed in the fixed-bed reactor when using a combination of Daw Mill coal and silver birch wood. Similar behaviour was observed under CO2-gasification. However this weak trend appears to be sample dependent, for a second sample set, total volatile yields were about 5% higher than would be expected in the absence of synergistic effects. The differences were systematic and larger than levels of experimental repeatability, but too small to provide information that might explain them. Isothermal combustion reactivities of Daw Mill coal and silver birch wood (mixture) chars prepared at 1000°C, in the fixed-bed reactor, were almost twice as high as those of coal char alone, despite the total gasification of the wood at this temperature. Mineral matter residue from the wood appears to have played a catalytic effect during combustion. When chars were separated with solvent, the effect could not be observed. The analogous effect observed with a second pair of samples was smaller, suggesting that the composition of ashes from different samples play a role. Apart from the catalytic effect of biomass ashes formed at high temperatures, observed synergistic effects were not of a magnitude that might influence process design. No evidence of synergy was found with the fluidised-bed reactor, thereby demonstrating the lack of contact between coal and biomass particles in the system.

Selective maceral enrichment during grinding and effect of particle size on coal devolatilisation yields

The effect of particle size on rapid-heating volatile yields from a range of particle size cuts prepared from three different coals have been measured using a wire-mesh apparatus. Samples were pyrolysed in helium at heating rates of 1000 K s −1 to 950°C with 10 s hold time. Particle size cuts over the range 38–150 μm were prepared by two methods: sieving from a ground coal and regrinding the largest-sieved size cut. The latter approach was employed in a (partially successful) effort to minimise differences in size-cut compositions. In general, total daf volatile yields were observed to increase slightly with decreasing particle size, but for two of the coals, this effect was not monotonic over the range 38–150 μm and was also dependent on the sample preparation method. Maceral analysis showed significant differences in all cases; however, with smaller particle-size cuts generally enriched in liptinite. To examine the effect of particle size without interference from maceral enrichment, a vitrain was used to prepare size cuts over the range 38–300 μm. Volatile yields from these samples were virtually identical. The overall conclusion from this study is that mass transfer effects due to different particle sizes are probably less significant than unavoidable maceral enrichment effects during sample preparation. For rapid-heating volatile release tests (e.g., drop tube furnace, wire-mesh apparatus) requiring a sized coal sample, a comparison of TGA (thermogravimetric analysis) volatile yield measurements have been shown to be a reasonable indicator of whether or not the size cut has a similar composition to the whole coal.

98/03422 Complex equipment for semicoking and gasification of brown coals: Savinov, M. M. et al. Ugol' Ukr., 1996, (5/6), 10–11. (In Russian)

A set of NaCl-loaded coal samples was prepared by physically impregnating NaCl into a Victorian (Loy Yang) brown coal. This set of brown coal samples was pyrolysed in a thermogravimetric analyser and in a novel fluidised-bed/fixed-bed reactor. The latter reactor has some features of both a fluidised-bed reactor and a fixed-bed reactor. The reactor configuration allowed the volatilised Na to be swept away by carrier gas from the bed of char particles, avoiding the re-condensation of the volatilised Na on the char particles at lower temperatures. The volatilisation of Na and of Cl during pyrolysis was quantified simultaneously. The results indicated that a significant proportion of Cl could be volatilised at temperatures around 200°C. The volatilisation of Cl increased drastically with increasing temperature, from 200 to about 500°C. At higher temperatures with a fast heating rate, Cl could interact with the nascent char to be retained in the char. The volatilisation of Na followed a different trend from that of Cl and increased monotonically with increasing temperature. The loading of NaCl into the brown coal had negligible effects on the total volatile yields and on the volatilisation of Mg and Ca during pyrolysis. It is concluded that NaCl in the brown coal was mainly released as Na and Cl separately rather than as NaCl molecules. Reactions involving radicals play important roles in the volatilisation of Na and Cl.

Pyrolysis and Gasification in a Bench-Scale High-Pressure Fluidized-Bed Reactor

A bench-scale high-pressure fluidized-bed reactor designed for pyrolysis, gasification, and combustion experiments (up to 1000 °C, 40 bar) has been constructed and commissioned. The system is intended to generate fuel reactivity data rapidly and cheaply, under realistic experimental conditions; it is relatively simple to construct and capable of operation by a single researcher. The reactor body (Incoloy Alloy 800HT, 34 mm i.d., 504 mm long) serves as the resistance heater and is designed to withstand the reaction pressure, obviating use of a “cold” pressure casing. The reactor is lined with a loosely fitting quartz tube to limit corrosion and catalytic effects. Sample (up to 2000 mg) is held between two air actuated valves and injected batchwise (“single-slug”) through a water-cooled probe. The design of the reactor allows determination of tar/oil and char yields. Exhaust gases are passed through a dryer before entering the analytical stage. The present report focuses on equipment design and preliminary data from pyrolysis and gasification experiments with Daw Mill coal (UK) at up to 1000 °C and 30 bar. Extents of gasification were calculated by subtraction of total volatile yields in CO2 from mass loss during pyrolysis in helium, performed under otherwise identical conditions. Combustion reactivities of chars were determined in an atmospheric pressure TGA instrument. A number of design adjustments have been described, enabling total volatile yields from the FB reactor to match those from a high-pressure wire-mesh reactor. As expected, tar yields from the fluidized-bed reactor were significantly lower than those from the wire-mesh instrument, due to longer residence times of volatiles in the bed of solids and the reactor freeboard.

The effect of pH on the volatiles formed in an extruded starch-glucose-lysine model system

Starch-glucose-lysine extrudates were produced using a twin-screw co-rotating machine. The final barrel zone and die temperatures were 150 ± 3 °C and 150 ± 7 °C, respectively. The residence time was 32 s, the moisture content of the feed was 18% (m m −1) and the feed pH was 4.0, 5.0 or 7.7. Isolates of the volatile components were prepared using continuous steam distillation-solvent extraction with pentane:ether (9:1, v/v) as the solvent. Analysis by gas chromatography-mass spectrometry resulted in the identification of 32, 20 and 16 compounds, respectively, from each isolate. At pH 7.7, nitrogen compounds dominated the isolate and pyrazines accounted for over 80% (m m −1) of the volatiles. At pH values of 5.0 and 4.0, the yield of pyrazines was less than 10% of that at pH 7.7 and furans comprised more than 80% (m m −1) of these aroma isolates. The yield of total volatiles was more than 60% greater at pH 7.7 than at the other pH values.

Effect of changing inertinite concentration on pyrolysis yields and char reactivities of two South African coals

Pyrolysis experiments have been carried out with sets of inertinite graded samples prepared from two South African coals (Durban Navigation and Vryheid Coronation Collieries). The effects on product distributions of increasing inertinite concentration, and of different heating rates, have been determined. An atmospheric pressure wire-mesh pyrolysis reactor was used during these experiments (1 or 1000 K s -1 to 700 °C with 30 s holding at peak temperature) in order to minimize reactor related effects on the results. Tar and total volatile yields from the South African samples decreased with increasing inertinite concentration ; the decrease in yields were in line with those observed for a set of maceral concentrate samples from a UK coal (Point of Ayr) and other Northern Hemisphere coals. Total volatile yields showed no detectable deviations when plotted alongside a correlation based on data from 24 Northern Hemisphere derived coals. Relative combustion reactivities of the chars from the pyrolysis experiments have been determined using a standard TGA-based method, as a function of inertinite contents of the original samples. The lower rank DNC set showed a rapid drop in char combustion reactivity with increasing inertinite concentration. By contrast, the reactivity of the VCC samples showed no sensitivity to changes in maceral concentration. It seems tempting to ascribe this similarity between vitrinites and inertinites of the VCC samples to progressively diminishing differences between macerals of higher rank coals. Clearly, however, many more samples need to be studied before definitive conclusions can be drawn.

Effect of Changing Inertinite Concentration on Pyrolysis Yields and Char Reactivities of Two South African Coals

Pyrolysis experiments have been carried out with sets of inertinite graded samples prepared from two South African coals (Durban Navigation and Vryheid Coronation Collieries). The effects on product distributions of increasing inertinite concentration, and of different heating rates, have been determined. An atmospheric pressure wire-mesh pyrolysis reactor was used during these experiments (1 or 1000 K s -1 to 700 °C with 30 s holding at peak temperature) in order to minimize reactor related effects on the results. Tar and total volatile yields from the South African samples decreased with increasing inertinite concentration ; the decrease in yields were in line with those observed for a set of maceral concentrate samples from a UK coal (Point of Ayr) and other Northern Hemisphere coals. Total volatile yields showed no detectable deviations when plotted alongside a correlation based on data from 24 Northern Hemisphere derived coals. Relative combustion reactivities of the chars from the pyrolysis experiments have been determined using a standard TGA-based method, as a function of inertinite contents of the original samples. The lower rank DNC set showed a rapid drop in char combustion reactivity with increasing inertinite concentration. By contrast, the reactivity of the VCC samples showed no sensitivity to changes in maceral concentration. It seems tempting to ascribe this similarity between vitrinites and inertinites of the VCC samples to progressively diminishing differences between macerals of higher rank coals. Clearly, however, many more samples need to be studied before definitive conclusions can be drawn.

Volatile constituents of ambarella (Spondias cytherea Sonnerat) fruit

AbstractThe volatile constituents of ambarella (Spondias cytherea Sonnerat) fruit were isolated by vacuum distillation with subsequent extraction of the distillate with dichloromethane. The concentrated extract was analysed by capillary GC and GC‐MS. The volatile constituents of the green (unripe) and ripe fruits were very similar, being dominated by C6 compounds and monoterpene hydrocarbons, with (E)‐hex‐2‐enal and α‐pinene constituting the two major components. The ripe fruit, however, gave a higher yield of total volatiles and a greater number of minor constituents which were mostly esters.

Volatile Components ofLawsonia inermisL. Flowers

ABSTRACT The volatile constituents of yellow and red Lawsonia inermis L. (henna) flowers were analyzed by capillary GC and GC/MS following isolation by solvent extraction. The total yield of volatiles isolated was higher from the yellow flowers which also differed markedly from the red flowers in volatile composition, the former giving greater proportions of β-ionone (48.6% vs 2.5%) and its derivatives, while the latter producing larger fractions of 2-phenylethanol (11.5% vs 5.8%), benzyl alcohol and C6 alcohols and aldehydes.

Structural relationships between kerogens and their pyrolysis products determined with a wire-mesh reactor

Two samples, of different geological age, of each of the three major types of kerogen were pyrolysed in a wire-mesh reactor, allowing tars to be recovered quantitatively under conditions minimizing extraparticle secondary reactions. To gain improved understanding of the reactions leading from kerogens to oil, the structures of the kerogens and their pyrolysis tars were compared by FT-i.r. spectroscopy. Tars were also characterized by size exclusion and planar chromatography. For each type of kerogen, the geologically younger sample gave the greater oil and total volatile yields. The aliphatic hydrogen contents of the kerogen samples were correlated with the oil yields from the wire-mesh reactor. The infrared spectra showed that the tars had substantially higher aliphatic hydrogen and slightly higher aromatic hydrogen contents than those of the original kerogens. Concentrations of phenolic-OH and carbonyl groups were also somewhat higher than in the original kerogen, at the expense of etheric structures, which tend to be present in very low concentrations in kerogen tars. Initial results indicate that a more comprehensive treatment needs to be formulated than that provided by conventional elemental analysis in predicting hydrocarbon production from kerogens.

An experimental study of high-temperature, oxidative pulverized coal devolatilization

Flat-flame coal-dust burner and entrained-flow reactor experiments were performed to study the devolatilizationof size-graded Pittsburgh #8 coal samples under rapid heating, oxidizing conditions. The flat-flame burner characterized by high heating rates, high temperatures, and short residence times was used on three different particle-size cuts and two proximate volatiles-to-oxygen equivalence ratios. The entrained-flow reactor characterized by high heating rates, lower temperatures, and longer residence times was used at two different ambient temperatures. Solid samples were collected at different positions and thereby different residence times in the flames and subjected to ultimate and TGA proximate analysis. The results indicate that, in rapid heating systems (10 5 K/s), release of primary volatiles occurred within 5–10 ms. The 10–20- and 30–40- μ m fractions gave approximately the same total volatile yield of 50% and peak temperatures of 1550 K, while the conversion for a 0–75- μ m fraction was 5% higher with measured peak temperatures 100 K higher, indicating in situ combustion of small particles and devolatilization of large particles. Increasing equivalence ratio lowered the temperatures around 100 K, and volatiles yield decreased 5%. Devolatilization kinetics for flat-flame burner (FFB) and entrained-flow reactor (EFR) were fit by the distributed activation energy parallel reaction model using literature data combined with a total volatile yield estimate of 52% and ultimate analysis data from the flame experiments. Thermogravimetric analyzer (TGA) devolatilization profiles of the collected samples and comparisons of characteristic temperature and time of devolatilization to time of diffusion were found to be very useful tools in the analyzing process of the experimental results.

A method of predicting coal devolatilization behavior based on the elemental composition

An interpolation method was proposed to correlate the input parameters of a coal devolatization model[functional group-depolymerization, vaporization, cross-linking (FG-DVC)] to coals of a wide range of ranks, and it conceptually applicable to other devolatilization models. This method uses a set of well-defined coals (library coals) to form a triangular mesh in the van Krevelen diagram. If an unknown coal is within a triangle formed by three library coals, the model input parameters for this unknown coal can be interpolated from those of the three library coals based solely on the elemental composition. This method extends the FG—DVC model to be able to model any coal that can be interpolated, without the requirement for any additional characterization of the coal. It is also easy to accommodate more library coals so that a wider range of coal types can be covered. The validity of this method was demonstrated by comparing the tar yield measurements and the predictions for 27 coals over a wide range of pressures and heating rates. For most of the coals, the predictions compare very well with the data. For selected coals, data were available on the variation of the yield of total volatiles with pressure and heating rate, and again, good agreement was obtained. The model could be improved by using additional parameters to describe the exchangeable cation content, sulfur content, and/or the maceral composition.

Initial stages of the devolatilization of pulverized-coal in a turbulent jet

The initial stages of the devolatilization of three United Kingdom pulverized coals have been studied in a coal-laden turbulent air jet emerging into the combustion gas environment produced by a methane-air flat flame burner. The temperature range provided by these flames was between 1670 and 1870 K and the corresponding particle heating rate was about 10 5 K/s. Data are reported for major gas species concentrations, particle weight losses, and nitrogen released, which quantify the effects of gas temperature, particle size, and coal type. Overall, the results show that the rate of devolatilization increases with temperature, significantly decreases with particle size and that the composition of the volatiles released is a strong function of the structure of the parent coal. The fuel nitrogen release is correlated to the total volatile yield. The formation of fuel-NO depends on the extent of the nitrogen release and the coal particle combustion mechanism. The turbulence intensity has an important effect on the extent of devolatilization; hence the total weight losses detected in the present experiment exceed those found under nonturbulent conditions.

Effect of H 2-pressure on yields and structures of liquids from the hydropyrolysis of maceral concentrates

The recent development of a high-pressure wire-mesh pyrolysis reactor providing for the passage of a stream of sweep-gas through the sample holder - hitherto only available at atmospheric pressure - has allowed direct and reliable determinations of high-pressure pyrolysis tar yields in the relative absence of extraparticle secondary reactions. Sweeping volatiles into liquid-N 2 cooled traps has also made possible the quantitative recovery of tars for subsequent characterisation. Liquid and total volatile yields have been determined as a function of pressure, between vacuum (1 · 10 −5 torr) and 70 bar H 2, for a set of maceral concentrates prepared from Janina (Polish) coal. Variations in liquid product structures with reaction conditions have been characterised by size exclusion chromatography, UV-fluorescence and FT-ir spectroscopy.

Swelling properties of coal chars during rapid pyrolysis and combustion

Coal devolatilization experiments are commonly conducted at moderate temperatures (800 to 1300 K) and heating rates (10 3 to 10 4 Ks −1) in inert environments in order to measure evolved species before secondary reaction in the gas phase. However, chars from these experiments exhibit different physical characteristics than chars obtained under typical combustion conditions (1500 to 2000 K, 10 5 Ks −1, and 3 to 10 mol% oxygen). Experiments were conducted in two laminar, entrained-flow reactors to determine characteristics of coal chars in inert and oxygen-rich environments. One flow reactor was heated electrically, with gas temperatures of 1250 K, and the mol% oxygen was varied from 0 to 10%. The other flow reactor used a flat flame burner as the heat source, with gas temperatures of 1600 K, and the post-flame oxygen content was varied from 0 to 12 mol%. In both reactors, sampling was limited to regions during and immediately following devolatilization. Five coals of different rank were examined; for a given coal, similar total volatile yields were obtained in both flow reactors, and similarities in chemical compositions of the resulting chars are discussed. For softening coals, the apparent densities of chars obtained in the electrically heated reactor are much lower than that of chars from the flat-flame reactor, regardless of the gas phase oxygen content. This implies that changes in particle swelling behaviour between typical devolatilization experiments and char combustion experiments are not due to the presence of oxygen, but due to heating rate or post-flame gas species other than oxygen.

Effect of H2-pressure on the structures of bio-oils from the mild hydropyrolysis of biomass

Low intensity hydropyrolysis of biomass has been investigated as a likely process route for upgrading agricultural and municipal waste, aiming to produce less highly oxygenated bio-oils with more stable storage characteristics than atmospheric pressure pyrolysis oils. A high-pressure wire-mesh pyrolysis reactor, recently re-designed to allow continuous sweeping of volatile products away from the reaction zone, was used during these experiments. This reactor configuration allows the determination of bio-oil yields and the recovery of condensible products for analytical characterisation in the relative absence of extra-particle secondary reactions. Samples of Swedish pine-wood and pine-wood lignin have been pyrolysed at temperatures between 300–700°C, at hydrogen pressures up to 70 bar. Product bio-oils have been characterised by size exclusion chromatography (SEC), UV-fluorescence spectroscopy (UV-F) and gas chromatography-mass spectrometry (GC-MS). Bio-oil yields from both pine-wood and lignin decreased by relatively small amounts over the pressure range, but significant changes in liquid product structures were observed: product bio-oils with progressively smaller molecular masses and lower polarity have been obtained with increasing pressure. Nevertheless, product bio-oils were characterised by a preponderance of oxygenates, including syringol and guaiacol derivatives and carboxylic acids, rather than alcohols, ketones, terpenoid and polynuclear aromatic hydrocarbons. Considerable differences have been observed between hydropyrolysis yields from pinewood and lignin: bio-oil and total volatile yields from the parent wood were greater than those observed for the lignin sample by about 30%. Comparison by GC-MS and UV-F suggests that the lignin derived bio-oils contain considerably more aromatic and less polar structures than the wood derived oils. At 70 bars, traces of di- and tri-bromodibenzodioxins have been detected in pinewood bio-oils from experiments at 400 and 700°C, apparently liberated from the wood during hydropyrolysis; it is presumed that the precursor fungicide molecules had previously been incorporated into the wood structure.