Studies of the reactions of dibenzyl ether under preconversion processing conditions

The occurrence of retrogressive reactions during direct coal liquefaction processing is harmful because these reactions result in the formation of high molecular weight material that is refractory to further processing. Therefore, the yields of desired products are decreased, downstream processing conditions must be more severe than if retrogressive reactions did not occur, and in some cases, an accumulation of solids causes process shutdown. The objectives of this research project are (1) to determine the causes of retrogressive reactions during the initial processing of coal (known as preconversion processing) in direct liquefaction and (2) to devise methods for minimizing these undesired reactions. The first objective involves evaluating the effects of process conditions and additives on retrogressive reactions. The approach to completing this objective is twofold. Initial scoping studies have been done using the model compound dibenzyl ether (DBE). Subsequent work will use coal. Work on the second research objective will be performed in conjunction with the evaluation of the effects of process variables and additives on coal. Research for completing the second objective will involve several different approaches such as the use of cleaned coals, and the use of different coal pretreatments.