GB737881A - Improvements in the catalytic dehydrogenation of hydrocarbons - Google Patents

Abstract

Hydrocarbons are dehydrogenated in the gaseous or vaporous phase at elevated temperature in the presence of a finely divided dehydrogenation catalyst which is brought into a turbulent state by a mixture consisting of gaseous or vaporous hydrocarbons and steam blown into the reaction chamber, by a process wherein the hydrogen evolved by the dehydrogenation of the hydrocarbons is converted into water by equivalent amounts of oxygen which are introduced separately into the reaction chamber after the dehydrogenation has been initiated. The heat of combustion of hydrogen is sufficient to supply the necessary dehydrogenation heat and further external heating is not required once the process is initiated. Excess heat may be removed by introducing the hydrocarbons to be dehydrogenated partly or wholly in the liquid phase or by spraying in water. The process is illustrated with reference to a cylindrical reaction vessel having a conical bottom which is filled to one quarter or fifth with a finely powdered dehydrogenation catalyst with a grain size of 20 microns to 2 mm. The catalyst is brought into a turbulent state by blowing in steam or nitrogen at the bottom and is heated to reaction temperature by an electrical heating jacket or directly with fuel gas. The hydrocarbon is blown in as a vapour, if desired with steam, and once the reaction is initiated, oxygen or air is blown in by means of annularly arranged nozzles and the heating is discontinued. The product vapours pass through a separator, a filter and a heat exchanger and then into a dephlegmator in which the reaction product and water are precipitated. The conversion of ethylbenzene to styrene at a temperature of 580 DEG C. is described by way of example.