Reactivation of hydrocarbon isomerization catalysts

A process for isomerizing saturated hydrocarbons which comprises the steps of:

• contacting (a) a fluid feed mixture comprising (i) at least one saturated feed hydrocarbons elected from the group consisting of alkanes containing 4-7 carbon atoms per molecule and cycloalkanes containing 6-7 carbon atoms per molecule, (ii) hydrogen gas and (iii) at least one chlorinated hydrocarbon with (b) an isomerization catalyst comprising platinum, chlorine and an inorganic support material in a reaction zone at effective isomerization conditions comprising a reaction temperature in the range of about 80.degree. F. to about 500.degree. F., a molar ratio of hydrogen gas to said at least one saturated feed hydrocarbon in the range of about 0.02:1 to about 10:1, and a content of said at least one chlorinated hydrocarbon in said fluid feed mixture equivalent to a chloride level in the range of about 15 ppm Cl to about 800 ppm Cl, so as to convert a portion of said at least one saturated feed hydrocarbon to at least one saturated product hydrocarbon isomer for a prolonged period of time until said catalyst is partially deactivated;
• (B) increasing the molar ratio of hydrogen gas to said at least one saturated feed hydrocarbon at least about 10 percent above said molar ratio employed in step (A) and lowering by at least about 5 percent the content of said at least one chlorinated hydrocarbon in said fluid feed mixture employed in step (A) while substantially retaining the remaining operating conditions of step (A), and maintaining the operating conditions of this first reactivation step (B) for a period of at least about 0.1 hour;
• (C) increasing the content of said at least one chlorinated hydrocarbon in said fluid feed mixture at least about 10 percent above said content used in steps (A) and (B) while substantially retaining the remaining operating conditions of step (B), and maintaining the operating conditions of this second reactivation step (C) for a time period of at least about 0.1 hour;
• and
• (D) returning to said effective isomerization conditions employed in step (A) and carrying out this isomerization step (D) using the reactivated catalyst from step (C) until said reactivated catalyst is again partially deactivated.