Abstract: Catalytic system for dehydrogenating ethylbenzene to styrene, containing chromium oxide, tin oxide, at least one oxide of an alkaline metal (M) and an alumina carrier, in delta or theta phase or in a mixture of delta+theta or theta+alpha or delta+theta+alpha phases, modified with silica, and characterized in that: the chromium, expressed as Cr2O3, is in a quantity of between 6 and 30% by weight; the tin, expressed as SnO, is in a quantity of between 0.1 and 3.5% by weight; the alkaline metal, expressed as M2O, is in a quantity of between 0.4 and 3% by weight; the silica is in a quantity of between 0.08 and 3% by weight, the complement to 100 being alumina.

Abstract: Process for the production of styrene which comprises:a) feeding to an alkylation unit a stream of benzene and a stream of recycled product containing ethylene;b) mixing the stream at the outlet of the alkylation unit, containing ethylbenzene, with a stream consisting of ethane;c) feeding the mixture thus obtained to a dehydrogenation unit containing a catalyst capable of contemporaneously dehydrogenating ethane and ethylbenzene;d) feeding the product leaving the dehydrogenation unit to a separation section to produce a stream essentially consisting of styrene and a stream containing ethylene;e) recycling the stream containing ethylene to the alkylation unit.

Abstract: Catalytic system for dehydrogenating ethylbenzene to styrene, containing chromium oxide, tin oxide, at least one oxide of an alkaline metal (M) and an alumina carrier, in delta or theta phase or in a mixture of delta+theta or theta+alpha or delta+theta+alpha phases, modified with silica, and characterized in that:the chromium, expressed as Cr.sub.2 O.sub.3, is in a quantity of between 6 and 30% by weight;the tin, expressed as SnO, is in a quantity of between 0.1 and 3.5% by weight;the alkaline metal, expressed as M.sub.2 O, is in a quantity of between 0.4 and 3% by weight,the silica is in a quantity of between 0.08 and 3% by weight, the complement to 100 being alumina.