Catalyst regeneration

An improved process for dehydrogenating an alkane, the process comprising placing an alkane in operative contact with a heated alkane dehydrogenation catalyst in a reactor, the catalyst comprising a Group VIII noble metal, a Group IIIA metal and, optionally, a promoter metal, removing from the reactor a partially deactivated catalyst, rejuvenating the partially deactivated catalyst in a regenerator, and transporting the rejuvenated catalyst from the regenerator to the reactor, wherein the improvement comprises a combination of treatment within the regenerator and transport of the rejuvenated catalyst from the regenerator to the reactor, the treatment within the regenerator comprising sequential steps:

• a. heating the partially deactivated catalyst to a temperature of at least 660 degrees Celsius using heat generated combustion products obtained by combusting both coke contained on the partially deactivated catalyst and a fuel source other than the coke, the heating yielding a heated, further deactivated catalyst which has an alkane dehydrogenation activity that is less than that of the partially deactivated catalyst;
• b. subjecting the heated, further deactivated catalyst to a conditioning step which comprises maintaining the heated, further deactivated dehydrogenation catalyst at a temperature of at least 660 degrees Celsius while exposing the heated, further deactivated dehydrogenation catalyst to a flow of an oxygen-containing gas with a chlorine or chlorine containing compound with an overall Cl concentration 0.1 ppm-volume to 100 ppm-volume for a period of time sufficient to yield an oxygen-containing reactivated dehydrogenation catalyst that has an activity for dehydrogenating alkane that is greater than that of either the partially deactivated catalyst or the further deactivated catalyst;
• and, optionally,
• c. maintaining the oxygen-containing reactivated catalyst at a temperature of at least 660 degrees Celsius while exposing the reactivated catalyst to a flow of stripping gas that is substantially free of molecular oxygen and combustible fuel for a period of time greater than two minutes and sufficient to remove from the oxygen-containing reactivated dehydrogenation catalyst at least a portion of molecular oxygen trapped within or between catalyst particles and chemisorbed oxygen that is desorbable at the temperature during that period of time and yield a rejuvenated dehydrogenation catalyst;
• with
• transport from the regenerator to the reactor being effected by a combination of gravity and motive force imparted by an inert transport gas.

A method of reducing a time of an air-soak treatment in a regeneration process, comprising:

• (i) removing surface carbon species from a gallium-based alkane dehydrogenation catalyst in a combustion process using a fuel gas;
• and
• (ii) conditioning, after the surface carbon species is removed from the gallium-based alkane dehydrogenation catalyst, the gallium-based alkane dehydrogenation catalyst in the air-soak treatment at a temperature of 660 degree Celsius (° C.) to 850° C. with (iii) a flow of oxygen-containing gas having (iv) 5 to 90 parts per million by volume (ppmv) of a chlorine source selected from chlorine, a chlorine compound or a combination thereof,
• wherein a predetermined alkane conversion percentage for the gallium-based alkane dehydrogenation catalyst undergoing the air-soak containing regeneration process is achieved using (i) through (iv) at least 10% to 50% sooner in air-soak treatment than a time required to achieve the same predetermined alkane conversion percentage for the gallium-based alkane dehydrogenation catalyst undergoing the air-soak treatment containing regeneration process using (i) through (iii), but without (iv).