Process of converting ethylbenzene to styrene by catalytic dehydrogenation

In a process of converting ethylbenzene to styrene by catalytic dehydrogenation at a temperature about 600.degree. C. in the presence of water vapor in a tubular reactor, the improvement which comprises supplying heat to said tubular reactor in the form of a molten salt bath, consisting essentially of a mixture of sodium carbonate, potassium carbonate and lithium carbonate, effecting dehydrogenation isothermally in said tubular reactor in a single stage under atmospheric pressure or under a subatmospheric pressure and with a water vapor-ethylbenzene ratio of 1.2-1.5 kg steam per kg ethylbenzene, the temperature of the ethylbenzene/water vapor mixture introduced into the tubular reactor being 50.degree. to 100.degree. C. below the temperature of the molten salt bath.