Study of the chemical reactions involved in the initial stages of coal liquefaction was carried out in a novel laboratory scale batch reactor capable of operation up to 450 degrees C and 17 MPa (2500 psig) under well-defined contact times from a few seconds to 30 min or longer. This report covers the design, construction, and use of this apparatus for studying coal liquefaction and other fuel-related processes. The characteristics of the reactor system and its operation include the following : (1) The reaction mixture at ambient temperature is driven through a preheater into a reactor using high-pressure gas. Both preheater and reactor are in a sand bath at reaction temperature prior to the start of the reaction. (2) The reaction mixture is then agitated by gas bubbles introduced through the mixture from the bottom of the reactor. (3) The process is terminated (quenched) in a similar way by blowing the reaction mixture through a precooler into a receiver with high pressure gas. This reactor is particularly effective for running coal liquefaction and the hydroprocessing of coal-derived vacuum resids, when kinetic measurements at very short reaction times are required. The reactor is simple in design and can be conveniently operated in the laboratory. It has the potential to augment the widely used tubing bombs or small autoclaves for laboratory studies of many high-pressure, high-temperature reactions.