97/00833 Coal liquefaction kinetics

Abstract

Understanding the mechanisms of uncatalyzed direct coal liquefaction by means of reaction kinetics has been a long sought goal. Curran et al. in 1967 and Wiser in 1968 and Neavel in 1976 measured the rates of liquefaction of various coals and postulated a free radical mechanism to explain the data obtained. The kinetics as determined by these and other workers is described in detail by Gorin in Chapter 27 of Elliott`s Second Supplementary Volume to the Chemistry of Coal Series. However, it has been well known that most coals contain some material extractable by organic solvents. The solvents used in direct coal liquefaction would of course be expected to also extract soluble material as well as effect the liquefaction reaction. If the extractable material were a significant quantity in the coal, it would seriously affect the kinetics. Cassidy et al. used a stirred autoclave with a sampling port at the bottom in their kinetic studies. They observed that hot charging the coal rapidly formed an oil which they considered to originate predominantly from the {open_quote}guest component{close_quote}, i.e., extractables, in the lignite they studied. Also, the free radical nature of the liquefaction process would be expected to produce secondary reaction productsmore » which would complicate the kinetics as well as lead to retrograde products. The kinetics of the liquefaction of a bituminous and subbituminous coal are reported.« less