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The effect of biochar addition on the levels of black carbon (BC) and polcyclic aromatic hydrocarbons (PAHs) in a vineyard soil in central Italy was investigated within a two year period. Hydropyrolysis (HyPy) was used to determine the contents of BC (BCHyPy) in the amended and control soils, while the hydrocarbon composition of the semi-labile (non-BCHyPy) fraction released by HyPy was determined by gas chromatography-mass spectrometry, together with the solvent-extractable PAHs. The concentrations of these three polycyclic aromatic carbon reservoirs changed and impacted differently the soil organic carbon over the period of the trial. The addition of biochar (33 ton dry biochar ha(-1)) gave rise to a sharp increase in soil organic carbon, which could be accounted for by an increase in BCHyPy. Over time, the concentration of BCHyPy decreased significantly from 36 to 23 mg g(-1) and as a carbon percentage from 79% to 61%. No clear time trends were observed for the non-BCHyPy PAHs varying from 39 to 34 μg g(-1) in treated soils, not significantly different from control soils. However, the concentrations of extractable PAHs increased markedly in the amended soils and decreased with time from 153 to 78 ng g(-1) remaining always higher than those in untreated soil. The extent of the BCHyPy loss was more compatible with physical rather than chemical processes.

Compound-specific stable carbon isotope analysis by gas chromatography/combustion/isotope ratio mass spectrometry is an effective and risk-free means of investigating fatty acid metabolism. Straightforward analysis, however, leads to poor chromatographic resolution, while derivatization adds carbon thereby corrupting the starting stable isotopic composition. Hydropyrolysis is a new approach which defunctionalizes fatty acids to yield the corresponding n-alkanes thus retaining the carbon skeleton intact and improving chromatography, allowing the faithful measurement of carbon isotope ratios., (Copyright (c) 2005 John Wiley & Sons, Ltd.)

Ni-CaO-ZrO2 catalysts with different properties were prepared and tested for CO2 reforming of methane. The catalysts were characterized by means of transmission electron microscopy, thermogravimetric analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction to reveal their distinct properties and carbon deposition behaviors in the reforming reaction. It was found that the catalyst prepared by a coprecipitation method and ageing by heating to reflux exhibited a nanocrystalline structure with strong metal-support interaction, which was responsible for both high activity and stability, but it also exhibited the highest carbon formation rate among the tested catalysts. This result suggests that catalyst deactivation might not necessarily correlate with the amount of formed carbon, and the individual properties of carbon residuals could play a more decisive role. Carbon residuals on different catalysts were identified as amorphous carbon, encapsulating carbon, whisker carbon, and graphite, which had different influence on the deactivation. On the surface of the most active and stable catalyst, the carbon species mainly consisted of amorphous and whisker carbon, suggesting that the formation of such carbon species does not necessarily lead to catalyst deactivation. In contrast, the deactivation was found to be closely related to the formation of encapsulating carbon and graphite, which could coat the catalyst surface. The accumulation of different carbon residuals was proven to follow a formation-diffusion/elimination scenario, which was significantly influenced by the Ni particle size and Ni-ZrO2 interactions. [ABSTRACT FROM AUTHOR]

Abstract: Hydropyrolysis (hypy) as a fast means for preparing lignin concentrates for stable carbon isotope analysis was evaluated by performing hypy at different temperatures (200–500°C) on Klason lignin concentrates, cellulose, and wood samples followed by bulk stable carbon isotope analysis of the solid residues. The δ 13C values of cellulose, Klason lignin and their hypy residues revealed that hypy does not produce isotopic fractionation throughout the temperature range explored. The δ 13C of hypy residues from cellulose-Klason lignin physical mixtures obtained at 500°C were in the value range of the corresponding Klason lignin indicating that cellulose decomposed completely and that no major structural rearrangements, which could lead to carbon cross-linking between these two moieties are produced by hypy. The hypy residues obtained from wood samples at 500°C were consistently depleted in 13C by 0.8‰ and enriched by 1.6‰ relative to the original wood and Klason lignin, respectively. This finding results from polysaccharide derivatives remaining in the wood residue, with a percentage of polysaccharide derived carbon 1.9 and 3.7 times higher than expected at 300 and 350°C, respectively. It is concluded that the results presented here provide an indicator of the extent of cross-linking between lignin and polysaccharides (hemicellulose) in the native wood forming lignin–carbohydrate complexes. [Copyright &y& Elsevier]

Abstract: A Ni-Cu (4:1wt/wt) metal alloy catalyst has been studied for the catalytic decomposition of ethylene to produce hydrogen and carbon nanofibers. To maximise ethylene conversion in a horizontal tube reactor with high residence times, hydrogen yields and selectivities, the temperature, sample mass and ethylene flow rate were varied. Both high ethylene conversions (>80%) and high hydrogen selectivities (75%) were obtained at 873 and 923K. The highest coke yield obtained after just 3h was around 480gC/gNi+Cu at 873K (86% ethylene conversion) and was significantly higher than the value of 250gC/gNi+Cu which was previously reported as the maximum coke yield for the decomposition of ethylene over Ni-Cu catalysts at this temperature. At 923K, the optimum conditions were achieved with 50mg of Ni-Cu, which gave ethylene conversions of 74%, a hydrogen selectivity of 71%, hydrogen yields in excess of and even higher coke yields of 1112gC/gNi+Cu after 15h with the catalyst still possessing high catalytic activity. The Ni-Cu (4:1wt/wt) catalyst behaved similarly to a Ni-Pd (4:1wt/wt) catalyst, which suggests that unsupported Ni-Cu alloys can replace the more expensive Ni-Pd alloys for the catalytic decomposition of hydrocarbons. In addition, there were no obvious structural differences between the carbon nanofibers obtained with the Ni-Cu and Ni-Pd alloys, which were twisted, branched and straight nanofibers composed of crystalline and amorphous carbon with diameters ranging from 30 to 300nm. [Copyright &y& Elsevier]

Abstract: Widely different hydrogen adsorption capacities have been reported for a variety of carbon materials which have attracted attention for hydrogen storage. This has led to doubts as to the validity of some of the claims and it has been suggested that one possible reason for the disparate hydrogen sorption capacities may lie in the inaccurate measurement of the hydrogen adsorbed. The aim of the work described in this paper was to make a contribution to this debate by developing a means and method of producing repeatable, accurate measurements of hydrogen sorption capacity in carbon materials. The apparatus developed is a volumetric differential pressure set-up operating at up to 10MPa and the method has a conservative limit of detection of 0.1wt% and an accuracy of ±0.05wt%, using 1.0–2.5g samples of the carbon materials studied. These included a carbon nanofiber sample and a series of activated carbons, the latter displaying a direct correlation between the BET effective surface area and the hydrogen sorption capacity of the materials. The amount of hydrogen adsorbed was less than 1wt% for all the carbons examined. [Copyright &y& Elsevier]

The addition of biomass to coking coals can reduce operational costs and carbon emissions but also reduces fluidity development. The use of heating rates up to 20 °C min−1 in the softening stage of coal has been investigated using high-temperature small-amplitude oscillatory-shear (SAOS) rheometry to improve the fluid characteristics of binary blends of two coking coals with Scots pine. The effects of biomass concentration and particle size, biomass torrefaction, pellet mass and thermal pre-treatment of the blend on fluidity development and semicoke strength have also been studied. Fluidity increased with an increase in heating rate and an increase in the final temperature for fast heating. Relationships were found between the minimum complex viscosity of the blend, the heating rate and the concentration of biomass, which have been used to propose an equation to calculate the heating rate necessary to achieve optimum fluidity for a particular blend with biomass. The fluid characteristics of the blend were not affected to a great extent by the particle sizes of the biomass studied (<500 μm and >500 μm) or the torrefaction of the biomass (250 °C for 1 h in N2), were increased by an increase in pellet mass, and were destroyed by blend pre-heating. The semicoke strength of the blend with a mass fraction of 10% Scots pine and fast heating (10 °C min−1) proved to be higher than that of the coal alone with slow heating (3 °C min−1) and resulted in a 3% reduction in non-renewable carbon emissions. [ABSTRACT FROM AUTHOR]