Process for preparing butadiene and/or butenes from n-butane

A process for preparing butadiene from n-butane, comprising the steps of

• A) providing a feed gas stream a comprising n-butane;
• B) feeding the feed gas stream a comprising n-butane into at least one first dehydrogenation zone and nonoxidatively catalytically dehydrogenating n-butane to obtain a gas stream b comprising n-butane, 1-butene, 2-butenes, butadiene and hydrogen, with or without water vapor, with or without carbon oxides and with or without inert gases;
• C) compressing in at least one first compression stage and cooling the gas stream b to obtain at least one condensate stream c1 comprising water and a stream c2 comprising butenes and butadiene, n-butane, hydrogen and water vapor, with or without carbon oxides and with or without inert gases;
• D) absorbing the butenes and the stream c2 comprising butadiene, n-butane, hydrogen and water vapor, with or without inert gases and with or without carbon oxides, with a selective solvent such as a mixture comprising 80 to 97% by weight of N-methylpyrrolidone and 3 to 20% by weight of water, to obtain a stream d1 comprising selective solvent such as N-methylpyrrolidone, water, and butenes, butadiene and butane, with or without carbon dioxide, and a stream d2 comprising hydrogen, with or without inert gases and butane;
• E) extractively distilling the stream d1 comprising selective solvent such as N-methylpyrrolidone, water, and butenes, butadiene and butane, with or without carbon oxides, with a selective solvent such as a stream e1 comprising 80 to 97% by weight of N-methylpyrrolidone and 3 to 20% by weight of water, to separate the stream d1 comprising selective solvent such as N-methylpyrrolidone, water, and butenes, butadiene and butane, with or without carbon oxides, into a stream e2 comprising selective solvent such as N-methylpyrrolidone, water, and butane, butenes and butadiene, and a stream e3 comprising essentially butane, with or without carbon oxides;
• F) distilling the stream e2 comprising selective solvent such as N-methylpyrrolidone, water, butane and butenes, butadiene, to give a stream e1 comprising essentially selective solvent such as N-methylpyrrolidone and water, and a stream f comprising butane, butenes, butadiene;
• G) feeding stream f and an oxygenous gas into at least one second dehydrogenation zone and oxidatively dehydrogenating 1-butene and 2-butenes to obtain a gas stream g comprising n-butane, unconverted 1-butene and 2-butenes, butadiene and water vapor, with or without carbon oxides, with or without hydrogen and with or without inert gases.