Inherently safe ODH operation

A process for the catalytic oxidative dehydrogenation of one or more C2-4 alkanes comprising at least two pre-reactors and one or more downstream main oxidative dehydrogenation reactors comprising:

• i) passing a feed stream comprising said one or more C2-4 alkanes through a first pre-reactor containing a dehydrogenation catalyst that is saturated with reactive oxygen;
• ii) reacting the feed stream with the dehydrogenation catalyst that is saturated with reactive oxygen at a temperature from about 300° C. to about 500° C. and a pressure from about 0.5 to about 100 psig to produce a partially dehydrogenated stream comprising unreacted C2-4 alkanes;
• iii) passing the partially dehydrogenated stream together with additional oxygen feed to one or more downstream main oxidative dehydrogenation reactors;
• iv) oxidatively dehydrogenating the partially dehydrogenated stream at a temperature from about 300° C. to about 500° C. and a pressure from about 0.5 to about 100 psig to produce a product stream;
• v) removing the product stream from said one or more downstream main oxidative dehydrogenation reactors comprising corresponding C2-4 alkenes, unreacted C2-4 alkanes, unreacted oxygen and water vapor;
• vi) passing the product stream through a second pre-reactor comprising a second dehydrogenation catalyst that is depleted of reactive oxygen;
• vii) reacting the product stream, with the dehydrogenation catalyst depleted of reactive oxygen at a temperature from about 50° C. to about 270° C. and a pressure from about 0.5 to about 100 psig to complex the oxygen depleting oxygen from the product stream and regenerating oxidative dehydrogenation catalyst by increasing the saturation with reactive oxygen;
• and
• viii) recovering a product stream depleted of oxygen;
• ix) continuing step (i) to (viii) until either:
• a) the pre-reactor comprising the first dehydrogenation catalyst and through which the feed stream is being passed is depleted of reactive oxygen or is more depleted of reactive oxygen than another pre-reactor;
• or
• b) the pre-reactor comprising the second oxidative dehydrogenation catalyst through which the product stream is being passed is substantially saturated with reactive oxygen;
• x) when condition (a) is achieved the feed stream is diverted from the first pre-reactor to another pre reactor comprising a dehydrogenation catalyst that is saturated with reactive oxygen and the process continues from step (ii) on;
• xi) when condition (b) is achieved the product stream is diverted from the second to another pre reactor comprising a second dehydrogenation catalyst depleted of reactive oxygen and the process continues from step (viii) on.