Process for hydrocarbon purification by selective hydrogenation

Claim 2

A process according to claim 1, wherein the hydrocarbon mixture passing into the second reaction zone contains less than 5,000 ppm of highly unsaturated compounds by weight.

Claim 3

A process according to claim 1, wherein the temperature difference between the inlet and the outlet of the first reaction zone is maintained lower than 20*C.

Claim 4

A process according to claim 1, wherein the hydrocarbon mixture introduced in the first reaction zone has a content of highly unsaturated compounds of from 0.5 to 3 percent.

Claim 5

A process according to claim 1, wherein the pressure in the first reaction zone is in the range of from 5 to 50 bars.

Claim 6

A process according to claim 1, wherein the pressure in the second reaction zone is in the range of from 15 to 80 bars.

Claim 7

A process according to claim 1, wherein the feed charge is a C3 cut and the hydrogenation temperature is -10* to 50*C in the first stage and 0* to 30*C in the second stage.

Claim 8

A process according to claim 1, wherein the feed charge is a C4 cut and the hydrogenation temperature is -10* to 50*C in the first stage and 0* to 30*C in the second stage.

Claim 9

A process according to claim 1, wherein the feed charge is pyrolysis gasoline, consisting essentially of hydrocarbons having from five to 10 carbon atoms per molecule and wherein the hydrogenation temperature is from 20* to 180*C in both zones.

Claim 10

A process according to claim 1 wherein the Group VIII metal is nickel.

Claim 11

A process according to claim 1 wherein the Group VIII metal is palladium.

Claim 12

A process according to claim 1 wherein the temperature difference between the inlet and the outlet of the first reaction zone is maintained lower than 10*C.

Claim 13

A process as defined by claim 8 wherein the temperature in the second stage is 10* to 20*C.

Claim 14

A process asddefined by claim 9 wherein the temperature in the second stage is 10* to 20*C.

Claim 15

A process according to claim 1 wherein the hydrocarbon mixture introduced in the first reaction zone has a content of highly unsaturated compounds of from 1 to 2 percent.

Claim 16

A process for purification by selective hydrogenation, of a mixture of hydrocarbons of three to 10 carbon atoms, said mixture containing at least one monoolefin, and as an impurity to be selectively hydrogenated, a highly unsaturated compound selected from the group consisting of acetylenic, diolefinic, and alkenylaromatic compounds, said process comprising passing said hydrocarbon mixture in the liquid phase together with a hydrogenation gas into a first stage reaction zone containing a fixed bed Group VIII metal hydrogenation catalyst, conducting said first stage reaction at a temperature of from -10* to 180*C for a sufficient time to partially hydrogenate said impurity and controlling the pressure in said first stage reaction zone to vaporize from 5 to 50 percent by weight of the hydrocarbon mixture within said first stage reaction zone during said time, thereby avoiding a high temperature increase of the reaction medium due to exothermal reaction heat; withdrawing from said first stage reaction zone a reaction mixture comprising both the vaporized and the unvaporized fraction of the hydrocarbon mixture, condensing the vaporized fraction of said mixture, and admixing it with the unvaporized fraction thereof, so as to recover the total outflow from the first stage reaction zone as an essentially liquid phase, and passing said essentially liquid phase, together with a hydrogenation gas into a second stage reaction zone, containing a fixed bed Group VIII metal hydrogenation catalyst, conducting said second stage reaction at a temperature of from 0* to 120*C and under a higher pressure than in the first stage and for a sufficient time to further hydrogenate said impurity and to hydrogenate up to a partial amount of said monoolefin, which pressure is sufficient for maintaining substantially all the reactants in the liquid phase during the hydrogenation in said second stage.

Claim 17

A process for purification, by selective hydrogenation of a butadiene cut, said cut containing a predominant amount of 1,3-butadiene, and as an impurity to be selectively hydrogenated, at least one member selected from the group consisting of 1,2-polybutadiene and an acetylenic compound of three to four carbon atoms, said process comprising passing said butadiene cut in the liquid phase together with a hydrogenation gas into a first stage reaction zone containing a fixed bed Group VIII metal hydrogenation catalyst, conducting said first stage reaction at a temperature of from -10* to 180*C under a sufficient pressure and for a sufficient time both to partially hydrogenate said impurities and to vaporize from 5 to 50 percent by weight of the butadiene cut within said first stage reaction zone, thereby avoiding a high temperature increase of the reaction medium due to exothermal reaction heat; condensing resultant vaporized fraction; and passing resultant total butadiene cut from the first reaction zone, in the liquid phase, together with a hydrogenation gas into a second stage reaction zone, containing a fixed bed Group VIII metal hydrogenation catalyst; conducting said second stage reaction at a temperature of from 0* to 120*C and under a higher pressure than in the first stage and for a sufficient time to further hydrogenate said impurity, which pressure is sufficient for maintaining substantially all the reactants in the liquid phase during the hydrogenation in said second stage.

Claim 18

A process as defined by claim 1 wherein said mixture of hydrocarbon is a propylene cut.

Claim 19

A process as defined by claim 1 wherein said mixture of hydrocarbon is a butene cut.