Vehicle oils, coal liquefaction

Continuous catalytic coprocessing and liquefaction experiments were conducted in a computer-controlled 1-liter bench-scale continuous unit of the type diagrammed in Figure I. The feedstocks included Illinois No. 6 coal and Maya atmospheric tower bottoms (ATB) in coprocessing or with a heavy hydrotreated 650 F-975 F recycle distillate (V-1074) from Run 257 at the Wilsonville Advanced Coal Liquefaction Facility in liquefaction experiments. Properties of the two vehicle oils are summarized in Table II. 

Some coal liquefaction methods, such as the Synthoil (5) process and the CO-steam (6) process, are similar to solvent refining in their approach, but more severe conditions or a catalyst are used to give a fiuid product. In the Synthoil reaction, bituminous coal is pulverized, dispersed in a vehicle oil, and hydrogenated in a packed tubular reactor with or without added catalyst. The CO-steam process uses lignite coal and less expensive synthesis gas. The intended product is a heavy liquid fuel having ash, sulfur, and nitrogen contents suflBciently low to avoid stack-gas cleaning. Reactor temperature and pressure are normally 400°-450°C and 4000 psi, respectively. 

Weller et al. (128) provide a classic working model for coal liquefaction. The mechanism proposed is based on reaction of coal under hydrogen pressure and stannous sialfide catalyst. The reaction path proposed is coal asphaltene oil both reactions are first order with water and gas as a by-product. However, no oil vehicle is involved in this model. 

The Exxon donor solvent, direct liquefaction process also used hot oil drying. In this process, LRC is dried by a high-pressure hydrogenation reactor contact with hot recycle hydrogen donor solvent prior to entering. Unfortunately, no data were developed for solvent recovery after drying becanse the dried coal and vehicle solvent were reacted immediately with hydrogen in the Uqnefaction reactor. 

When coal is heated in a slurrying vehicle, it is liquefied at 400°C-500°C (750°F-930°F). Though the reaction mechanism involving conversion of coal to oil is very complex, it appears that the interaction of coal with solvent at the initial stage of the reactions plays the vital role to determine the sequential conversion of coal substances—first to a pyridine-soluble solid and thereafter to benzene-soluble liquid hydrocarbons and low-boiling products. Thus the isolation and identification of the products of coal-solvent interactions to yield pyridine-soluble matter may provide information regarding the suitability of the coal for liquefaction. 

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