Process and system for redcuing the olefin content of a hydrocarbon feed gas and production of a hydrogen-enriched gas therefrom

Abstract

Olefins can impose deleterious effect on hydrocarbon reforming processes used to generate hydrogen-enriched gas, and thus are converted into saturated compounds. Since the hydrogenation process to convert the olefins into saturated compound, difficulties arise in attempting to regulate the temperature of the hydrogenation. To facilitate temperature regulation, the hydrogenation reaction is carried out in a shell-tube reactor, containing catalyst-filled tubes, which is operated under isothermal or essentially isothermal conditions. Preferably, the heat exchange medium introduced into the shell side of the reactor to regulate the hydrogenation temperature is boiling water.

1 . A process for subjecting an olefin containing gas to a hydrogen treatment wherein olefin compounds are converted into saturated compounds, said process comprising:
 introducing hydrogen and a hydrocarbon feed gas comprising olefins, alkanes, hydrogen, CO 2 , and sulfur compounds into a hydrotreater wherein olefins are converted into saturated compounds and organic sulfur compounds are converted into H 2 S;   wherein the hydrotreater is a shell and tube catalytic reactor containing catalyst filled tubes, the hydrogen and hydrocarbon feed gas being introduced into the catalyst filled tubes, and the shell having at least one inlet for introduction of a heat exchange medium to cool the catalyst filled tubes, and at least one outlet for removal of the heat exchange medium, and wherein the hydrocarbon feed gas is introduced into the catalyst filled tubes at an inlet temperature of about 400 to 525° F.; and   removing the hydrocarbon feed gas from the catalyst filled tubes of the hydrotreater at a temperature that differs from the inlet temperature by no more than 30° F.   
     
     
         2 . A process according to  claim 1 , wherein the temperature of the hydrocarbon feed gas removed from the catalyst filled tubes of the hydrotreater differs from the inlet temperature by no more than 15° F. 
     
     
         3 . A process according to  claim 1 , wherein the temperature of the hydrocarbon feed gas removed from the catalyst filled tubes of the hydrotreater differs from the inlet temperature by no more than 10° F. 
     
     
         4 . A process for treating a hydrocarbon gas to reduce the olefin content and organic sulfur compound content thereof, the process comprising:
 introducing hydrogen and a hydrocarbon feed gas comprising olefins, alkanes, hydrogen, CO 2 , and sulfur compounds, into a hydrotreater wherein olefins are converted into saturated compounds and organic sulfur compounds are converted into H 2 S;   wherein the hydrotreater is a shell and tube catalytic reactor containing catalyst filled tubes, the hydrogen and hydrocarbon feed gas being introduced into the catalyst filled tubes, and the shell having at least one inlet for introduction of a heat exchange medium to cool the catalyst filled tubes, and at least one outlet for removal of the heat exchange medium, and wherein the hydrocarbon feed gas is introduced into the catalyst filled tubes at an inlet temperature of about 400 to 525° F.;   removing the hydrocarbon feed gas from the catalyst filled tubes of the hydrotreater at a temperature that differs from the inlet temperature by no more than 30° F.; and   subjecting the hydrocarbon feed removed from the hydrotreater to a desulfurization step.   
     
     
         5 . A process according to  claim 4 , wherein the temperature of the hydrocarbon feed gas removed from the catalyst filled tubes of the hydrotreater differs from the inlet temperature by no more than 15° F. 
     
     
         6 . A process according to  claim 5 , wherein the temperature of the hydrocarbon feed gas removed from the catalyst filled tubes of the hydrotreater differs from the inlet temperature by no more than 10° F. 
     
     
         7 . A process according to  claim 4 , wherein desulfurization is performed by introducing the hydrotreated gas into one or more adsorbers containing at least one adsorbent comprising zinc oxide. 
     
     
         8 . A process according to  claim 4 , further comprising, following desulfurization, delivering the desulfurized hydrocarbon feed stream to a hydrocarbon cracking procedure to produce a hydrogen-enriched synthesis gas. 
     
     
         9 . A process according to  claim 8 , wherein said hydrocarbon cracking procedure is steam reforming wherein the desulfurized hydrocarbon feed stream is converted in the presence of steam to produce a hydrogen-enriched synthesis gas containing H 2  and CO. 
     
     
         10 . A process according to  claim 9 , further comprising, following steam reforming, delivering the product gas stream from the steam reforming to a shift reactor wherein CO is reacted with water to form hydrogen and CO 2 . 
     
     
         11 . A process according to  claim 1 , wherein the heat exchange medium used in the hydrotreater is boiling water, and the temperature of the hydrocarbon feed stream within the catalyst tubes can be controlled by controlling the pressure of the steam generated in the shell side of the reactor during heat exchange. 
     
     
         12 . A process according to  claim 1 , wherein the hydrocarbon feed introduced into the hydrotreater contains 5 to 50 mol % olefins. 
     
     
         13 . A process according to  claim 1 , wherein the molar ratio of hydrogen to olefins and organic sulfur compounds introduced into the hydrotreater is 1.25:1 to 3:1. 
     
     
         14 . A process according to  claim 1 , wherein the catalyst in the tunes of the hydrotreater comprise at least one Group VI metal or compound thereof and at least one Group VIII metal or compound thereof. 
     
     
         15 . A process according to  claim 14 , wherein said catalyst is a nickel-molybdenum catalyst. 
     
     
         16 . A process according to  claim 1 , wherein said hydrotreater is operated at a temperature of 450 to 500° F., and a pressure of 250 to 400 psig. 
     
     
         17 . A system for preparing a hydrogen-enriched gas from a hydrocarbon feed stream, the system comprising:
 a catalytic hydrotreater comprising a shell and tube reactor wherein the tubes contain a catalyst for hydrogenation of olefins,   the shell and tube reactor further having a first inlet for introducing a hydrocarbon feed, or a mixture of hydrocarbons and hydrogen, into the tube-side of the reactor, and a first outlet for removing a hydrocarbon stream having reduced olefin content from the tube-side of the reactor,   the shell and tube reactor further having a second inlet for introducing a heat exchange medium to the shell-side of the reactor, and a second outlet for removing the heat exchange medium from the shell-side of the reactor,   an adsorber having an adsorbent bed containing an adsorbent for removal of hydrogen sulfide from a hydrocarbon gas stream, the adsorber further comprising an inlet for introduction of a hydrocarbon gas stream containing sulfur compounds, and an outlet for discharging a desulfurized hydrocarbon gas stream,   a first conduit in fluid communication with said first outlet of said reactor and in fluid communication with said inlet of said adsorber for introducing at least a portion of the hydrocarbon stream having reduced olefin content to said adsorber,   a hydrocarbon reformer comprising an inlet for introducing a desulfurized hydrocarbon gas stream and an outlet for discharging a hydrogen-enriched synthesis gas, and a second conduit in fluid communication with said outlet of said adsorber and in fluid communication with said inlet of said reformer for introducing at least a portion of the desulfurized hydrocarbon gas stream to said reformer.