Reactions between a gas and a liq. in the presence of a dispersed solid catalyst are carried out in a reactor comprising a vertical series of zones sepd. by perforated baffles. The gas and liq. are fed into the bottom of the reactor and pass upwards through each successive zone via the perforated baffles. The catalyst is fed into the top of the reactor and descends through a series of separate transfer lines connecting each zone to the next. Each transfer line has a relatively calm area at its lower end, where the catalyst collects. The improvement comprises controlling the flow rate of catalyst from one zone to the next by entraining this collected catalyst in a controllable secondary stream of liq. and/or gas injected into the transfer line. The process can be applied to the hydroconversion of hydrocarbons (esp. heavy oils), hydrocarbon synthesis from CO and H2, liquefaction of coal/oil slurries, etc. The process allows the catalyst descent rate to be controlled for optimum catalyst utilisation without the use of mechanical devices such as valves.
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