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.