Enhanced light olefin production

A process for producing ethylene and propylene comprising:

• a) passing a feedstream to an olefin production zone and therein producing an olefinic product stream comprising ethylene, propylene, and butylene and heavier olefins;
• b) passing the olefinic product stream to an olefin separation zone to provide an ethylene product stream, a propylene product stream, a mixed butylene and heavier stream, and a reject stream;
• c) passing the mixed butylene and heavier stream comprising normal olefins, iso-olefins, paraffins, and di-olefins to a di-olefin removal zone to provide a mixed mono-olefin stream comprising normal olefins, iso-olefins, and paraffins;
• d) converting at least a portion of the mixed mono-olefin stream in an olefin conversion zone containing an acid catalyst selective for the conversion of iso-olefins in the presence of at least a stoichiometric amount of an oxygen-containing compound to provide a conversion product stream comprising oxygenates, normal olefins, and paraffins;
• e) passing the conversion product stream to an oxygenate separation zone to separate oxygenates from the normal olefins and produce a net butylene stream;
• f) passing at least a portion of the net butylene stream to a butylene cracking zone and therein contacting the net butylene stream with a small pore selective catalyst for the cracking of the normal olefins to produce a light olefin stream comprising additional amounts of ethylene and propylene;
• and,
• g) recovering the additional amounts of ethylene and propylene.

A process for producing ethylene and propylene comprising:

• a) passing a feedstream comprising an oxygenate selected from the group consisting of methanol, dimethyl ether, ethanol, and mixtures thereof to an olefin production zone containing a non-zeolitic catalyst having an effective small pore size and an empirical chemical composition, on an anhydrous basis, expressed by the empirical formula:
• (EL.sub.x Al.sub.y P.sub.z)O.sub.2
• where EL is an element selected from the group consisting of silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium and mixtures thereof, x is the mole fraction of EL and is at least 0.005, y is the mole fraction of Al and is at least 0.01, z is the mole fraction of P and is at least 0.01 and x+y+z=1, and in said olefin production zone producing an olefinic product stream comprising ethylene, propylene, and butylene and heavier olefins;
• b) passing the olefinic product stream to an olefin separation zone to provide an ethylene product stream, a propylene product stream, a mixed butylene and heavier stream, and a reject stream;
• c) passing the mixed butylene and heavier stream comprising mono-olefins and di-olefins to a selective hydrogenation zone and therein contacting the mixed butylene and heavier stream with a hydrogenation catalyst in the presence of hydrogen to convert the di-olefins to mono-olefins and to provide a mixed mono-olefin stream comprising normal olefins, iso-olefins, and paraffins;
• d) passing the mixed mono-olefin stream to an etherification zone containing an acid catalyst, and in the presence of at least a stoichiometric amount of an alcohol, converting the iso-olefins to provide an ether product stream essentially free of iso-olefins comprising oxygenates, normal olefins, and paraffins;
• e) passing the ether product stream to an oxygenate separation zone to separate oxygenates from the normal olefins and produce a net butylene stream;
• f) passing at least a portion of the net butylene stream at effective cracking conditions to a butylene cracking zone containing a small pore catalyst selective for the conversion of linear mono-olefins to light olefins and therein contacting the net butylene stream with said catalyst to produce a light olefin stream comprising additional amounts of ethylene and propylene;
• and,
• g) recovering the additional amounts of ethylene and propylene.