TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The recycled stream consists of ethylene (2-50 wt.%) and ethane (50-98 wt.%).Preferred Process: Ethylbenzene and ethane are fed to the dehydrogenation unit in a molar ratios of 0.01 - 1. The dehydrogenation reaction takes place at 450-700 degreesC at 0.1-3 atmospheres with a gas hourly space velocity = 100-10000 h-1. It may be carried out in a fluid bed reactor, which operates at 450-650 degreesC, at atmospheric pressure or slightly higher with a space velocity = 100-1000 h-1, preferably 150-300 h-1.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The dehydrogenation catalyst is based on gallium and platinum on alumina in delta, theta. delta+theta, theta+alpha or delta+theta+alpha phases, modified with silica, and having a surface area (BET) = less than 100 m2/g.It may comprise (A) Ga2O3 (0.1-34 wt.%, preferably 0.2-3.8 wt.%); platinum (1-99 ppmw, preferably 3-80 ppm); alkaline and/or alkaline earth oxide (e.g. potassium) (0.05-5 wt.%, preferably 0.1-3 wt.%); silica (0.08-3 wt.%); and alumina (balance); or (B) Cr2O3 (6-30 wt.%, preferably 13-25 wt.%); SnO ( 0.1-3.5 wt.%, preferably 0.2-2.8 wt.%); alkaline oxide (e.g. potassium) (0.4-3 wt.%, preferably 0.5-2.5 wt.%); silica (0.08-3 wt.%); and alumina (balance). EXAMPLE - 2 - Catalyst (Ga2O3 (2.33 wt.%), K2O (0.4 wt.%), Pt (75 ppm), SiO2 (1.56 wt.%) and Al2O3 (to 100 wt.%)) (101g) was charged to an electrically heated quartz reactor having an internal diameter = 25 mm. Ethylbenzene (9 vol.%) mixed with ethane (91 vol.%) was preheated to 200 degreesC and fed to the fluidized catalyst in the reactor. Reaction occurred at 600 degreesC and 1.1 atmospheres. The WHSV of ethyl benzene = 0.2 kg/h/kg. SV = 587 h-1.The effluent was sent to a condenser cooled with dry ice and the non-condensable products were collected in a bag connected downstream. At the end of the reaction the condenser was brought slowly to room temperature and the liquid product was collected and analyzed by gc. The ethylbenzene conversion = 57.9% and of ethane = 12%. Mol. selectivity to styrene = 94% and to ethylene = 95%. Styrene was produced at 105 g/h/kg catalyst and ethylene at 60 g/h/kg catalyst. Ethylene/styrene mol./mol = 2.12. The coke deposited on the catalyst was burnt by feeding air to the reactor for 45 min. at 660 degreesC and the effluent was collected in a bag.