AN AMERICAN CHEMICAL SOCIETY JOURNAL VOLUME 3, NUMBER 3
MAY/JUNE 1989
0 Copyright 1989 by the American Chemical Society
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Heviews Role of Catalysis in Coal Liquefaction Research and Development? Frank Derbyshire Sutcliffe Speakman Carbons Limited, Guest Street, Leigh, Lancashire WN7 2HE, England Received November 22, 1988. Revised Manuscript Received February 17, 1989
The economic viability and operability of processes to convert coals to useful liquid products is contingent upon the development and application of effective catalysts. The present understanding of the role of catalysis in direct liquefaction is reviewed, and approaches that could lead to improved and novel catalysts are discussed. Existing supported catalysts are unsuitable for hydroprocessing high-boiling coal liquids. Two approaches are indicated: the development of radically different supported catalyst formulations and the use of dispersed catalysts to control the process of primary dissolution. The latter may lead to improved quality feeds for further hydroprocessing. The functions of dispersed sulfide and acid catalysts are considered. In both cases, multicomponent catalyst systems offer promise for significant advancement.
Introduction The production of distillate fuels and chemicals from coal has never been economical in a free market economy. The principal factors that contribute to the high cost of coal-derived liquids are the large amounta of hydrogen that must be added to remove heteroatoms and to convert material containing about 5 wt % hydrogen to products with between 12 and 14 wt % hydrogen, the severe reaction conditions (temperature and pressure), and the relatively low rates of conversion that are experienced. In spite of these limitations there are valid reasons for pursuing research and development in coal liquefaction. Practically every future energy scenario envisions the development of indigenous fossil fuel resources to supplement and replace materials derived from petroleum crudes. In the short term, situations could arise whereby the supplies of imported crudes to oil-poor industrialized nations are restricted, and in the long term, world petroleum reserves will be eventually be depleted. The technology to liquefy coals has been available since before the Second World War. Modern process developments have demonstrated considerably superior perform'Based in part upon ref 1.
ance over that of the first commercial-scale plants. Nevertheless, it is still not possible to produce liquids at prices that are competitive with those derived from petroleum. As has occurred in the development of the petroleum processing and chemical industries, the route to further significant improvements in liquefaction processing lies in the successful development and application of suitable catalyst systems. In this paper, some of the more salient aspects of liquefaction catalysis are reviewed in relation to the limitations of our present understanding and to avenues for research that could lead to improved and novel developments. The material presented in this paper has been based in part upon a much more extensive review, which was recently published by IEA Coal Research under the sponsorship of the U.S.Department of Energy.' A companion review on catalysis in syngas conversion has also been prepared.2 The recognition that liquefaction takes place in two loosely defined stages, consisting of coal dissolution followed by upgrading of the solubilized products, has lead (1) Derbyshire, F.J. Catalysis in Coal Liquefaction: New Directions for Research; IEA Coal Research London, 1988. (2) Mills, G. A. Catalysts for Fuels from Syngas; IEA Coal Research London, 1988.
0887-0624/89/2503-0273$01.50/00 1989 American Chemical Society
274 Energy & Fuels, Vol. 3, No. 3, 1989
Reviews
Table I. History of Process Development and Performance for Bituminous Coal Liquefaction' configuration single stage two staee noncatanoncatalytic/ catalytic/ lytic catalytic catalytic catalytic (1982) (1982) (1985) (1986) distillate, wt % 41 52 62 70 of coal (maf) 20.2 20.2 26.8 distillate, 12.3 qualitylgravitr. OAPI non1hydrocarbons, w t % S 0.33 0.20 0.23 0.11 0 2.33 1.0 1.9
