Barry D. Batts

Effect of groundwater fulvic acid on the adsorption of arsenate by ferrihydrite and gibbsite

Abstract Adsorption studies have been conducted at pH 4, 6 and 8 to assess the effect of fulvic acid on arsenate adsorption to ferrihydrite and gibbsite. The studies compared the adsorption of arsenate on the mineral surfaces in the absence of fulvic acid, to those cases where increasing concentrations of fulvic acid (0.3–60 μM) were added to the mineral–arsenate suspensions. Experiments where arsenate was added to mineral–fulvate suspensions were also conducted. The results suggest that arsenate adsorption on both gibbsite and ferrihydrite decreases with increasing concentrations of fulvic acid. This effect was highest at pH 4, and decreased at pH 6 and 8. Ferrous ion concentrations were very low during the ferrihydrite experiments and support the view that fulvic acid can both displace arsenate from and inhibited its adsorption to mineral surfaces. The experiments also indicated that the amount of arsenate adsorbed was lower if fulvic acid was added before rather than after arsenate. This may reflect the relative size of arsenate and fulvic acid molecules and their ability to penetrate the crystal matrices of the minerals.

The effect of maturation on the isotopic composition of fossil fuels

Abstract Few measurements of the D/H ratios in liquid and solid fossil fuels have been made. Additional isotopic data are reported here in the form of D/H and 13 C/ 12 C ratios for crude oils and brown coals which occur together in the Bass Strait region of Australia. Studies of petrographic fractions of these coals and of the changes in the isotopic composition of coals and coal extracts with increasing maturity show that the original D/H ratios characteristic of contributing plant materials are more readily erased and homogenized during early diagenesis than the corresponding 13 C/ 12 C ratios.

The origin of nitriles in shale oil

Abstract Because nitriles are unlikely to occur naturally in a geological environment but have been reported as being present in some shale oils their origin was investigated. A careful infrared study could find no trace of the nitriles in the shale but it was shown, by infrared and gas chromatography with a nitrogen sensitive detector, that they do occur in some but not all oils. They are formed in the pyrolysis process by the reaction of car☐ylic acids and ammonia liberated from minerals such as ammonium feldspars present in the shale. If both species are not present nitriles are not formed in the product oil. Pyrolysis of a brown coal, Loy Yang, in the presence of ammonia produced nitriles but none were generated when a more mature coal (Metropolitan) was similarly treated.

Hydrous pyrolysis of model compounds

Abstract In pursuit of a method for the determination of the total n -alkyl content of petroleum source rocks, the reactions of model organic compounds containing a long-chain n -alkyl constituent with water have been studied in sealed tubes. At 330°C, the n -alkyl component of n -alcohols and n -ethers and the n -alcohololic components of esters are largely converted to, and release as, the corresponding n -alkanes. Some fragmentation of carbon chains accompanies this reaction. The conversion of n -alkanoic acids to n -alkanes is only partial, even at 350°C, and n -alkyl aromatics and n -alkyl hydroaromatics remain virtually unaffected under these conditions. Where significant n -alkane generation from model compounds is observed, additions of brown coal generally promote this process. In view of the stability of n -alkanoic acids and n -alkylated hydrocarbons observed under the conditions of hydrous pyrolysis used in this study, this technique is not entirely suitable for determining the total n -alkyl content of all source rocks nor, presumably, their full petroleum potential.

The geosynthesis of alkylaromatics

Phenanthrene, anthracene and pyrene have been pyrolysed in sealed reactors in the presence of coal. No methylation occurs at 220°C but increasing amounts of methylaromatics are formed at temperatures to 350 or 400°C. This methylation provides support for geosynthetic processes in sediments, because the experimental conditions used may be thermally equated to Ro values of 0.63–2.03%. The high concentration of n-alkanes generated from the coal may play a crucial role in such reactions. With increasing temperature there are systematic and theoretically predictable increases in the ratio of the β/α substituted methyl isomers of the parent aromatic hydrocarbons. The greater proportions of β-substituted isomers in the methyl products of reactions at higher temperatures may be due either to α→β rearrangements, or to direct methylation at the β-positions. Yields of methylphenanthrenes continue to increase up to 400°C. Lower yields of methylanthracenes and methylpyrenes at 400°C are attributed to demethylation.

Hydrous pyrolysis reactions of sulphur in three Australian brown coals

Abstract Hydrous pyrolysis of three Australian brown coals in the presence of cadmium acetate (CdOAc) indicates that as much as 77% of the original organic sulphur may be generated as H 2 S. In the absence of CdOAc much of the generated H 2 S was re-adsorbed back into the insoluble coal residues. GC–MS analyses of the solvent extracts of the coals and of the solvent extracts of the hydrous pyrolysates at 110–330°C both in the presence and absence of cadmium acetate reveal a little parent thiophene and benzothiophene totally dominated by a broad range of methyl derivatives. Yields of these sulphur compounds tend to be greater when cadmium acetate is absent. Benzothiophenes are favoured over thiophenes at the higher hydrolysis temperatures. Analyses of the solvent extracted residues by FP–GC–MS and of mixtures of low sulphur coal and elemental sulphur, produced a similar range of parent thiophene and benzothiophene and their methylated derivatives. The ubiquity of these sulphur compounds suggests these to be the thermodynamically favoured products of sulphur/organic matter interaction. The only other class of sulphur compounds seen, the longer chain n -alkyl thiophenes, occurred in the soluble 200°C hydrous pyrolysis products obtained in the absence of cadmium acetate. Only these appear to reflect structures in the original brown coals. The implication of this study is that the earliest formed organic sulphur compounds in immature sediment will, with increasing temperature, continue to decompose and release H 2 S and elemental sulphur. The released sulphur species will, in turn, undergo reaction with the organic matter to form more stable sulphur compounds. Sulphur incorporation is likely to be a continuing process throughout diagenesis and catagenesis.

Evidence for synthetic generation of methylphenanthrenes in sediments

Abstract All isomers of methylphenanthrene are formed when phenanthrene is reacted with methane and/or long chain n -alkanes in the presence of coals or kaolinite in closed steel reactors in the range 230–360 °C. In particular, the 3-methylphenanthrene isomer, for which a convincing degradative precursor-controlled source has not been described, becomes increasingly prominent at higher experimental temperature due to the 4 → 3 methyl shift promoted by steric interaction at the 4- and 5-positions. Therefore, a geosynthetic origin for the high concentrations of 3-methylphenanthrene in mature carbonaceous sediments is indicated. Furthermore, in a broader sense, the data demonstrate the need to consider synthetic, in addition to degradative, reactions in maturational processes in sediments.

The effects of varying tissue preservation on the aliphatic hydrocarbons within a high-volatile bituminous coal

Detailed petrographic analyses of the Barrett Coal, an Upper Permian high-volatile bituminous coal in the Hunter Coalfield, Australia, reveal cycles of peat formation defined by the Tissue Preservation Index. These cycles correspond to coal plies that are separated by dirtbands. The petrographic cyclicity is also manifested by a corresponding stratigraphic cyclicity in the biomarker composition of the extracted aliphatic hydrocarbons. Higher amounts of hopanes and lower Carbon Preference Index values (n-C22 to n-C30) show greater bacterial contribution in samples characterised by low values of Tissue Preservation Index. The inherited biodegradation signal from the diagenetic stage has now been partially diluted by the generation of new hydrocarbons from the macromolecule. The C31 αβ (22S22S + 22R) hopane and C29 ααα (20S20S + 20R) sterane ratios show least variation through the seam. The homohopane epimer ratios have attained equilibrium, whilst the hopane/moretane ratios are typical of coals with unsupressed vitrinite reflectance of > 0.65%. However, other hopane and sterane maturity ratios appear slightly affected by the degree of preservation of organic matter. The C29 (αββαββ + ααα) and C29 ααα (20S20S + 20R) sterane ratios were not found to be useful for maturity comparisons with other coals because of the low values (average 0.18 and 0.43, respectively) due to heating-rate effects. These and other biomarker distributions are syndepositional features of the coal precursor and therefore are controlled by the environmental conditions during the stage of peat accumulation and its subsequent coalification. All these changes are evident in a coal member only 2.2 m in thickness. The petrographic and geochemical evidence suggest that the environmental affinity of the Barrett Coal is that of a delta-plain depositional setting.

Thermal reactions of 1,8-dimethylnaphthalene

Abstract The distribution of products from the thermal reaction of 1,8-dimethylnaphthalene in hydrous and anhydrous conditions at temperatures of 275–360°C has been shown to be controlled largely by the presence of brown coal, silica or clays during reaction. In particular, ratios of product 1,7- and 2,7-dimethylnaphthalene to parent 1,8-dimethylnaphthalene cannot be related to reaction temperatures. The role of water in the reaction is obscure. Certainly, conversion to the 1,7-isomer is promoted at 360°C, but otherwise, water inhibits the catalytic activity of clays and the generation of the 2,7-isomer. In addition, reflectance measurements ( R ) on a brown coal subjected to parallel thermal regimes, demonstrate R undergoes a greater increase in hydrous rather than anhydrous conditions. Geochemical interpretations of these data suggest that isometric distributions of the dimethylnaphthalenes may be more strongly influenced by sediment composition in terms of content of carbonaceous material, silica and clays than by temperature. In addition, these distributions may reflect concentrations of specific precursors and/or hydrocarbons synthesized in situ, rather than the thermal isomeric re-arrangements of existing hydrocarbons.

Reaction of methane with coal

Abstract The reactivities of Australian coals and one American coal with methane or methane-hydrogen mixtures, in the range 350–400°C and a range of pressures (6.0–8.3 MPa, cold) have been examined. The effects of aluminophosphates (AlPO) or zeolite catalysts, with and without exchanged metals, on reactivity have also been examined. Yields of dichloromethane extractable material are increased by using a methane rather than a nitrogen atmosphere and different catalysts assist dissolution to various extents. It appears that surface exchanged catalysts are effective, but incorporating metals during AlPO lattice formation is detrimental. Aluminium phosphate catalysts are unstable to water produced during coal conversion, but are still able to increase extraction yields. For the American coal, under methane-hydrogen and a copper exchanged zeolite, 51.5% conversion was obtained, with a product selectivity close to that obtained under hydrogen alone, and with only 2% hydrogen consumption. The conversion under methane-hydrogen was close to that obtained under hydrogen alone, while a linear dependence of conversion on proportion of methane would predict a 43% conversion under methane-hydrogen. This illustrates a synergistic effect of the methane-hydrogen atmosphere for coal liquefaction using this catalyst system.