Production of aliphatic gasoline

A process combination for selectively upgrading a heavy naphtha feedstock to obtain lower-boiling hydrocarbons comprising the steps of:

• (a) contacting the heavy naphtha fraction with a solid acid selective isoparaffin-synthesis catalyst in a selective-isoparaffin-synthesis zone maintained at selective-isoparaffin-synthesis conditions comprising a pressure of from about 1 MPa to 10 MPa gauge, a molar hydrogen-to-hydrocarbon ratio of from about 0.1 to 10, a liquid hourly space velocity of from about 0.5 to 20 hr.sup.-1, and a temperature of from about 50.degree. to 350.degree. C. and recovering a synthesis effluent having a reduced end point relative to the heavy naphtha fraction;
• (b) separating the synthesis effluent in a separation zone to obtain an isobutane concentrate amounting to at least 8.0 volume % of the heavy naphtha fraction, a light synthesis naphtha comprising pentanes and a heavy synthesis naphtha;
• (c) contacting at least a portion of the heavy synthesis naphtha in a ring-cleavage zone with a nonacidic ring-cleavage catalyst, comprising at least one platinum-group metal component and a support selected from the group consisting of a nonacidic inorganic oxide, a metal-oxide solid solution and a nonacidic large-pore molecular sieve, at cleavage conditions comprising a temperature of from about 100.degree. to 550.degree. C., pressure of from about 100 kPa to 10 MPa, molar ratio of hydrogen to C.sub.5 + hydrocarbons of about 0.01 to 100 and liquid hourly space velocity of from about 0.1 to 30 hr.sup.-1 to convert at least about 50% of naphthenes in the heavy synthesis naphtha to yield at least about 90% of paraffins having the same carbon number as the naphthenes converted and obtain a paraffinic intermediate;
• and,
• (d) contacting the paraffinic intermediate, in combination with the heavy naphtha feedstock, with the selective isoparaffin-synthesis catalyst in the selective-isoparaffin-synthesis zone of step (a) at selective-isoparaffin conditions to obtain additional synthesis effluent.

A process combination for selectively upgrading a heavy naphtha feedstock to obtain lower-boiling hydrocarbons comprising the steps of:

• (a) contacting the heavy naphtha fraction with a solid acid selective isoparaffin-synthesis catalyst comprising a zeolite in a selective-isoparaffin-synthesis zone maintained at selective-isoparaffin-synthesis conditions comprising a pressure of from about 1 MPa to 10 MPa gauge, a molar hydrogen-to-hydrocarbon ratio of from about 0.1 to 10, a liquid hourly space velocity of from about 0.5 to 20 hr.sup.-1, and a temperature of from about 50.degree. to 350.degree. C. and recovering a synthesis effluent having a reduced end point relative to the heavy naphtha fraction;
• (b) separating the synthesis effluent in a separation zone to obtain an isobutane concentrate amounting to at least 8.0 volume % of the heavy naphtha fraction, a light synthesis naphtha comprising pentanes and a heavy synthesis naphtha;
• (c) contacting at least a portion of the heavy synthesis naphtha in a ring-cleavage zone with a nonacidic ring-cleavage catalyst, comprising at least one platinum-group metal component and a support selected from the group consisting of a nonacidic inorganic oxide, a metal-oxide solid solution and a nonacidic large-pore molecular sieve, at cleavage conditions comprising a temperature of from about 100 to 550.degree. C., pressure of from about 100 kPa to 10 MPa and liquid hourly space velocity of from about 0.1 to 30 hr.sup.-1 to convert at least about 50% of naphthenes in the heavy synthesis naphtha to yield at least about 90% of paraffins having the same carbon number as the naphthenes converted and obtain a paraffinic intermediate;
• and,
• (d) transferring the paraffinic intermediate from the ring-cleavage zone to the selective-isoparaffin-synthesis zone without separation of hydrogen or light hydrocarbons and contacting the intermediate, in combination with the heavy naphtha feedstock, with the selective isoparaffin-synthesis catalyst in the selective-isoparaffin-synthesis zone of step (a) at selective-isoparaffin conditions to obtain additional synthesis effluent.