TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Reactor System: The reactor system comprises up to 250 high shear mixing zone(s) which project through walls of the reactor vessel or are located within the reactor vessel, and an external heat exchanger positioned on external conduit and/or an internal heat exchanger positioned within the suspension in the reactor vessel. The mixing zone comprises an injector mixing nozzle which is preferably a venturi nozzle or a blast nozzle. The reactor vessel is a tank reactor or tubular loop reactor. When the reactor vessel is a tank reactor, the liquid coolant is introduced into the suspension recycle stream through an external conduit. When the reactor is a tubular loop reactor, the mixing zone comprises a section of tubular loop reactor containing high shear pump or venturi plate and synthesis gas is injected immediately upstream or downstream of the pump or plate. The heat exchangers are disposed along at least a portion of the length of the tubular loop reactor.Preferred Process: The liquid coolant is introduced into the reactor system at a temperature which is at least 25 degrees C below (preferably 35-85 degrees C below) the temperature of the suspension in the reactor vessel, and is cooled to less than 15 degrees C using refrigeration techniques. The coolant is capable of vaporizing in the reactor system under the conditions of elevated temperature and pressure, and has a boiling point of 30-280 degrees C, preferably 30-100 degrees C, at standard pressure. The coolant is introduced into mixing zones and/or reactor vessels. When the injector-mixing nozzle(s) is(a) venturi nozzle(s), the pressure drop of the suspension over the nozzle(s) is 1-40 bar, preferably 1-15 bar, and the ratio of the volume of gas (Qg) to volume of liquid (Ql) passing through the nozzle(s) is 0.5:1-10:1, preferably 1:1-5:1 (determined at the desired reaction temperature and pressure); or(b) gas blast nozzle(s), the pressure drop of the gas over the nozzle(s) is 3-100 bar, the pressure drop of the suspension over the nozzle(s) is 1-40 bar, preferably 4-15 bar, and the ratio of Qg to Ql passing through the nozzle(s) is 0.5:1-50:1, preferably 1:1-10:1.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Coolant: The liquid coolant is a 5-10C aliphatic hydrocarbon, cyclic hydrocarbon preferably cyclopentane or cyclohexane, 1-4C alcohol preferably methanol or ethanol, ether preferably dimethyl ether, tetrahydrofuran or water. EXAMPLE - Activated particulate Fischer-Tropsch catalyst (10 g), comprising cobalt on zinc oxide obtained as in U.S.4826800, was transferred under an inert gas blanket to a tank reactor containing 30 ml of squalane. The stirrer was turned ON and a synthesis gas mixture comprising hydrogen (in volume%) (54.1), carbon monoxide (26.4), carbon dioxide (10.3) and nitrogen (9.2) was admitted to the reactor at a space velocity of 6000 hour-1 and the system pressure was increased to 425 psig. A gaseous stream was continuously removed from the reactor and passed through a water cooled pot. The temperature of the system was increased over a period of 4 hours to 180 degrees C and then increased at a rate of 2 degrees C every 3 hour to 220 degrees C. The system was allowed to run for a total on-stream time of 372 hours. Liquid pentane was introduced to the reactor at a rate of 0.5 ml/hour, at a position below the suspension level, and allowed to evaporate in the reactor. The injection was continued for 36.3 hours, and hydrocarbon was produced. The conversion of carbon monoxide was 11 mol%, 11.3 mol% and 13.8 mol%, respectively prior to, during and after pentane injection. The productivity was 109.3 g/l/hour, 96.9 g/l/hour and 121.8 g/l/hour, respectively prior to, during and after pentane injection.