Selective hydrogenation of aromatics contained in hydrocarbon streams

A process for the hydrogenation of benzene contained in a full boiling range naphtha stream comprising the steps of:

• (a) feeding a full boiling range C.sub.5 -C.sub.8 naphtha stream containing benzene, toluene and xylenes to a distillation column reactor into a feed zone;
• (b) feeding a gas stream containing hydrogen into said feed zone;
• and
• (c) concurrently in a distillation reaction zone:
• (1) contacting said full boiling range naphtha stream and said gas stream with a fixed bed hydrogenation catalytic distillation structure in said distillation reaction zone under hydrogenation conditions to form a reaction mixture;
• and
• (2) fractionating said reaction mixture to:
• (i) maintain a fraction comprising benzene contained in said full boiling range naphtha stream in the distillation reaction zone to selectively react at least a portion of said benzene with said hydrogen to form a reaction mixture containing cyclohexane, unreacted benzene, unreacted hydrogen, unreacted toluene and unreacted xylenes and
• (ii) separating the resultant cyclohexane and benzene from unreacted toluene and xylenes;
• (d) withdrawing a C.sub.7 and heavier stream containing the unreacted toluene and xylenes from the distillation column reactor as bottoms;
• (e) withdrawing a C.sub.6 and lighter stream containing cyclohexane from distillation column reactor as overheads;
• (f) condensing the C.sub.5 and heavier compounds in said overheads and separating any unreacted gas from said overheads;
• and
• (g) returning a portion of said condensed overheads to said distillation column reactor as reflux.

In a process for hydrogenating selected aromatic compounds contained in a hydrocarbon stream, comprising:

• (a) feeding a mixed hydrocarbon stream containing a plurality of aromatic compounds to a distillation column reactor into a feed zone;
• (b) feeding a gas stream containing hydrogen into said feed zone;
• and
• (c) concurrently in said distillation column reactor:
• (1) contacting said mixed hydrocarbon stream and said gas stream with a fixed bed hydrogenation catalyst in a reaction zone under hydrogenation conditions to form a reaction mixture;
• and
• (2) fractionating said reaction mixture to separate the resultant saturated ring compounds from unreacted aromatic compounds
• wherein the improvement comprises maintaining a selected fraction comprising at least one and less than all of said aromatic compounds in the reaction zone to selectively react at least a portion thereof with said hydrogen to form a reaction mixture containing saturated ring compounds, unreacted hydrogen and unreacted aromatic compounds.

In a process for the hydrogenation of benzene contained in a full boiling range naphtha stream comprising the steps of:

• (a) feeding a full boiling range C.sub.5 -C.sub.8 naphtha stream containing benzene, toluene and xylenes to a distillation column reactor into a feed zone;
• (b) feeding a gas stream containing hydrogen into said feed zone;
• and
• (c) concurrently in a distillation reaction zone:
• (1) contacting said full boiling range naphtha stream and said gas stream with a fixed bed hydrogenation catalytic distillation structure in said distillation reaction zone under hydrogenation conditions to form a reaction mixture;
• and
• (2) fractionating said reaction mixture to separate the resultant cyclohexane and benzene from unreacted toluene and xylenes;
• (d) withdrawing a C.sub.7 and heavier stream containing the unreacted toluene and xylenes from the distillation column reactor as bottoms;
• (e) withdrawing a C.sub.6 and lighter stream containing cyclohexane from distillation column reactor as overheads;
• (f) condensing the C.sub.5 and heavier compounds in said overheads and separating any unreacted gas from said overheads;
• and
• (g) returning a portion of said condensed overheads to said distillation column reactor as reflux
• wherein the improvement comprises maintaining a fraction comprising benzene contained in said full boiling range naphtha stream in the distillation reaction zone to selectively react at least a portion of said benzene with said hydrogen to form a reaction mixture containing cyclohexane, unreacted benzene, unreacted hydrogen, unreacted toluene and unreacted xylenes.