Frank P. Larkins

Hydrogenation of brown coal. 3. Roles of hydrogen and hydrogen-donor solvents in systems catalysed by iron and tin compounds

Abstract The role of hydrogen and hydrogen-donor solvents in the liquefaction of a Victorian brown coal without added catalyst and in the presence of iron-and tin-based catalysts has been studied. Results of an investigation of the effect of temperature and pressure on the conversion parameters, of independent studies of asphaltene hydrogenation, and of work with model ethers are described. A mechanism is tentatively proposed to describe the role of iron, tin and iron-tin catalyst systems based upon these results.

Evidence for direct interaction of hydrogen with brown coal in tin-catalysed reactions

Abstract Evidence is presented which shows that the major mechanism for the tin-catalysed hydrogenation of suspensions of brown coals in tetralin involves a direct interaction of hydrogen with the coal.

Synergistic catalytic effect in the hydrogenation of Victorian brown coals

Abstract Evidence is presented that a mixed metal catalyst system, which is predominantly iron-based with trace amounts of tin, displays a significant synergistic effect in the hydrogenation of Victorian brown coal, when compared with hydrogenation results using only iron- or tin-based catalysts of comparable metal concentrations to the mixed metal system.

Hydrogenation of brown coal: IV Model compound studies and mechanistic considerations

Abstract A series of lignin-related phenyl, benzyl and alkyl ethers have been reacted with hydrogen in the presence of iron (II) acetate and tin metal as additives. Iron reduced the rate of reaction of the phenyl ethers and increased the rate of reaction of the benzyl and alkyl ethers compared to the reactions without additive. Tin decreased the rate of reaction of the phenyl and benzyl ethers and had no effect on the reaction of the alkyl ether. Neither iron nor tin changed the products from the reactions of the ethers compared to the reactions without additive. The results are discussed in terms of the use of iron and tin compounds as additives in coal liquefaction reactions.

Rapid extraction of products from coal hydrogenation reactions using an ultrasonic bath

Abstract Extraction of products into dichloromethane solution from reactions of Victorian brown coals with hydrogen in tetralin can be achieved in 2 min by immersing the extraction mixture in an ultrasonic bath at ambient temperature. The same levels of extraction using the Soxhlet technique can only be achieved by prolonged periods of extraction during which the coal extracts are heated at the reflux temperature of the solvent.

Hydrogenation of brown coal

Abstract A series of batch autoclave experiments has been conducted in which the product boiling in the range 220–450°C was recycled several times to test the suitability of this liquid as a vehicle for the hydroliquefaction of Victorian brown coal. The product liquid was used at the end of each cycle as a vehicle for an independent small-scale coal hydrogenation and repetitive hydrogenations of the parent solvent were also carried out to help facilitate understanding of the role and chemical changes associated with the vehicle. It has been shown that the distillable coal-derived liquid, even without recycling part of the bottoms, has a hydrogenation potential in the same range as tetralin and hydrogenated anthracene oil, despite its relatively poor quality. However, the amount of liquid produced was less than the amount of solvent used.

Surface reduction of some transition-metal oxides. An X-ray photoelectron spectroscopic study of iron, cobalt, nickel and zinc oxides

X-Ray photoelectron spectroscopy has been used to examine the effect of heating under high-vacuum conditions of some transition-metal oxides. Nickel and cobaltic oxides were found to undergo reduction to Ni metal and CoO below 300 °C. This reduction is shown to be caused by reaction with surface carbon-containing contaminants. Removal of this contamination by an in situ oxidation treatment resulted in a well defined surface which was stable to further heating. High-surface-area NiO underwent more extensive reduction than low-surface-area material. In contrast, ZnO was not reduced and only minor changes in the Fe2O3 spectra were observed. The results are explained by reference to bulk thermodynamic data. The findings are important particularly for characterisation of oxide surfaces used in catalytic studies.

Promoters for the liquefaction of wet Victorian brown coal in carbon monoxide

Abstract Sodium aluminate and sodium silicate have been found to be useful as promoters for the reaction of brown coal with carbon monoxide and water. Promoters such as sodium aluminate have been shown to behave effectively as a two-component system. The first component involves the sodium aluminate behaving as a mild base interacting with acidic groups in the coal. This role can be adopted by other basic salts (acetate, hydroxide, carbonate, etc.) of other alkali metals which have been found to be effective in the order Cs > K > Na > Li . The second component of the sodium aluminate system is an alkali metal ion doped alumina, whose role in the liquefaction is unclear but may involve the generation of strong Lewis base sites on the alumina which can facilitate one electron transfer reactions leading to radical stabilisation. These systems also catalyse the production of hydrogen by the water gas shift reaction but this has been shown not to be an essential feature of their action as magnesium acetate, which does not promote the water gas shift reaction, shows similar promoter activity. When these catalyst systems are combined with those traditionally active in promoting the reaction of coal with hydrogen (e.g. Cu, Ni, Co) new multi-element promoter systems are obtained which are particularly effective for promoting the reaction of brown coal with synthesis gas (CO + H 2 ) and water.

Hydrogenation of brown coal: 6. Reactions of coal-derived products with hydrogen in the presence of metal-based catalysts

Abstract The product from the hydrogenation of an iron-tin treated Morwell, Victorian coal was separated into a number of fractions by solvent separation. Each of these fractions (tetrahydrofuran-insoluble materials, asphaltols, asphaltenes and oils) was reacted separately with hydrogen in tetralin both with and without added catalysts. The effect of added catalyst and of temperature, pressure, time and solvent on the hydrocracking and repolymerization reactions is discussed. The interconvertibility of the brown coal-derived products is clearly established, reinforcing the importance of incorporating reversibility of reactions in mechanistic models developed to describe coal hydroliquefaction.

Regeneration studies on nickel molybdate catalysts used for the upgrading of coal-derived liquids

Abstract Nickel molybdate catalysts used in several different upgrading reactions of coal-derived materials from low-rank Australian coals have been regenerated and their activity assessed using a number of physical and chemical techniques. Regeneration of spent coked catalysts for 20 hours in air at 450°C was sufficient to restore chemical hydrogenation activity to catalyst used for pre-asphaltene, asphaltene and oil upgrading, provided poisoning of the catalyst surface by other impurities, principally chlorine-containing molecules, had not occurred.