Method for producing light unsaturated hydrocarbons

A process for producing partly renewable light unsaturated hydrocarbons, comprising:

• (a) contacting ethanol with an acid catalyst in at least one reactor under conditions suitable to form a reaction effluent stream comprising water, ethene, propene and unsaturated hydrocarbons with four carbon atoms, besides other co-products of secondary reactions;
• (b) feeding the stream generated in (a) to a direct-contact cooling unit under conditions suitable to form a top stream containing most of the light unsaturated hydrocarbons present in the effluent stream of step (a) and a bottom stream containing most of the water present in the effluent stream of step (a);
• (c) contacting naphtha with steam in a pyrolysis furnace of an existing cracking unit under conditions suitable to from a cracking effluent stream comprising light unsaturated hydrocarbons, fuel oil, gas oil and gasoline;
• (d) separating the effluent generated in the cracking reaction (c) into a light unsaturated hydrocarbon stream containing most of the light unsaturated hydrocarbons present in the effluent of step (c) and at least one heavy hydrocarbon stream;
• (e) feeding the stream rich in light unsaturated hydrocarbons from step (d) to a direct-contact cooling unit under conditions suitable to form a top stream containing most of the light unsaturated hydrocarbons present in the effluent of reaction (d) and a bottom stream containing the condensed compounds and most of the water present in the effluent of reaction (c);
• (f) combining the streams (b) and (e) and contacting them with a base solution in a caustic wash unit under conditions suitable to remove at least a part of the CO2 from the stream and sending them to the steps of separating and purifying unsaturated hydrocarbons C2, C3 and C4 of the existing cracking unit, wherein said pyrolysis furnace of said existing cracking unit is gradually replaced by reactors for conversion of ethanol to light unsaturated hydrocarbons.

A process for producing partly renewable light unsaturated hydrocarbons, comprising:

• (a) contacting ethanol with an acid catalyst in at least one reactor under conditions suitable to form a reaction effluent stream comprising water, ethene, propene and unsaturated hydrocarbons with four carbon atoms, besides other co-products of secondary reactions;
• (b) contacting naphtha with steam in a pyrolysis furnace of an existing cracking unit under conditions suitable to form a cracking effluent stream comprising light unsaturated hydrocarbons, fuel oil, gasoil and gasoline;
• (c) separating the effluent generated in the cracking reaction (c) into a light unsaturated hydrocarbon stream containing most of the light unsaturated hydrocarbons present ion the effluent of step (c) and at least one heavy hydrocarbon stream;
• (d) combining the effluent stream of the step of converting ethanol to unsaturated hydrocarbons (a) and the light unsaturated hydrocarbon stream generated in step (c) before the direct-contact fooling step for removal of condensates and water, followed by contact with a base solution in a caustic wash unit under conditions suitable to remove at least a part of the CO2 from the stream and from the steps of separating and purifying unsaturated hydrocarbons C2, C3 and C4 of the existing cracking unit, wherein said pyrolysis furnace of said existing cracking unit is gradually replaced by reactors for conversion of ethanol to light unsaturated hydrocarbons.