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1. A process in a reactor system comprising a reactor having a rhenium-based zeolite catalyst therein, said process comprising:
(i) a step comprising introducing nitrogen gas into said reactor system to at least partially displace any oxygen and/or moisture in said reactor system under conditions including a temperature T1 and a pressure P1, and then contacting said rhenium-based zeolite catalyst with said nitrogen gas for a predetermined period of time and/or until oxygen and/or moisture in said reactor system fall to a predetermined level; (ii) a step comprising introducing hydrogen gas into said reactor system to at least partially displace said nitrogen in said reactor system under conditions including a temperature T2 and a pressure P2, and then contacting said rhenium-based zeolite is catalyst with said hydrogen gas for a period of time which may be predetermined and/or measured by one or more of reactor system characteristics selected from ammonia levels, oxygen levels, moisture levels, and nitrogen gas levels measured in said reactor system; wherein T2≦T1 and P2≦P1 and at least one of T2<T1 and P2<P1 is true; and (iii) a step comprising contacting said rhenium-based zeolite catalyst with a paraxylene-depleted feedstream comprising orthoxylene and metaxylene, whereby at least a portion of said orthoxylene and metaxylene are isomerized to paraxylene.
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