Abstract:
The present subject matter relates generally to methods for selectively saturating the unsaturated C 2 -C 4 . More specifically, the present subject matter relates to methods for saturating butadiene and butenes from a hydrocarbon stream before it is combined with a fresh feed and enters a reaction zone. Removing the unsaturates from the hydrocarbon stream before the hydrocarbon stream enters the reaction zone prevents the reactor internals from coking.

Description:
FIELD 
     The present subject matter relates generally to methods for selectively saturating the unsaturated C 2 -C 4 . More specifically, the present subject matter relates to methods for saturating butadiene and butenes from a hydrocarbon stream before it is combined with a fresh feed and enters a reaction zone. Removing the unsaturates from the hydrocarbon stream before the hydrocarbon stream enters the reaction zone prevents the reactor internals from coking. 
     BACKGROUND 
     Dehydrocyclo-oligomerization is a process in which aliphatic hydrocarbons are reacted over a catalyst to produce aromatics and hydrogen and certain byproducts. This process is distinct from more conventional reforming where C 6  and higher carbon number reactants, primarily paraffins and naphthenes, are converted to aromatics. The aromatics produced by conventional reforming contain the same or a lesser number of carbon atoms per molecule than the reactants from which they were formed, indicating the absence of reactant oligomerization reactions. In contrast, the dehydrocyclo-oligomerization reaction results in an aromatic product that typically contains more carbon atoms per molecule than the reactants, thus indicating that the oligomerization reaction is an important step in the dehydrocyclo-oligomerization process. Typically, the dehydrocyclo-oligomerization reaction is carried out at temperatures in excess of 260° C. using dual functional catalysts containing acidic and dehydrogenation components. 
     Aromatics, hydrogen, a C 4+  non-aromatics byproduct, and a light ends byproduct are all products of the dehydrocyclo-oligomerization process. The aromatics are the desired products of the reaction as they can be utilized as gasoline blending components or for the production of petrochemicals. Hydrogen is also a desirable product of the process. The hydrogen can be efficiently utilized in hydrogen consuming refinery processes such as hydrotreating or hydrocracking processes. The least desirable product of the dehydrocyclo-oligomerization process is light ends byproducts. The light ends byproducts consist primarily of C 1  and C 2  hydrocarbons produced as a result of the cracking side reactions. 
     The uncoverted aliphatic hydrocarbons and a portion of cracking products from dehydrocyclodimerization reactor is separated, recovered and combined with the fresh feed, before entering the reactor. This recycle stream contains diolefins, mainly butadiene and C 2 -C 4  olefins and aromatics. Olefins that are in the recycle stream are thermally converted to diolefins in the heater train. Some other products of the dehydrocyclo-oligomerization process are also not desirable. For example, di-olefins such as butadiene are known to cause pyrolytic coking of reactor internals and thus builds up pressure of reactors. 
     Accordingly, it is desirable to develop methods for saturating butadiene and butenes before the recycle stream is combined with the fresh feed and enters the reaction zone. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background. 
     SUMMARY 
     A first embodiment is a method for saturating hydrocarbons including passing a hydrocarbon stream to a guard bed wherein the hydrocarbon stream is contacted with an adsorbent to form a treated hydrocarbon stream. The treated hydrocarbon stream and a hydrogen stream are then passed to a reaction zone containing a hydrogenation catalyst to form a reaction zone effluent stream. The hydrocarbon stream may include light paraffins, olefins, diolefins mainly butadiene, aromatics, water, hydrogen sulfide, and other sulfur containing compounds. Saturating the unsaturates prevents the reactor internals from coking. 
     Additional objects, advantages and novel features of the examples will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following description and the accompanying drawings or may be learned by production or operation of the examples. The objects and advantages of the concepts may be realized and attained by means of the methodologies, instrumentalities and combinations particularly pointed out in the appended claims. 
     DEFINITIONS 
     As used herein, the term “dehydrocyclodimerization” is also referred to as aromatization of light paraffins. Within the subject disclosure, dehydrocyclodimerization and aromatization of light hydrocarbons are used interchangeably. 
     As used herein, the term “stream”, “feed”, “product”, “part” or “portion” can include various hydrocarbon molecules, such as straight-chain, branched, or cyclic alkanes, alkenes, alkadienes, and alkynes, and optionally other substances, such as gases, e.g., hydrogen, or impurities, such as heavy metals, and sulfur and nitrogen compounds. The stream can also include aromatic and non-aromatic hydrocarbons. Moreover, the hydrocarbon molecules may be abbreviated C 1 , C 2 , C 3 , Cn where “n” represents the number of carbon atoms in the one or more hydrocarbon molecules or the abbreviation may be used as an adjective for, e.g., non-aromatics or compounds. Similarly, aromatic compounds may be abbreviated A 6 , A 7 , A 8 , An where “n” represents the number of carbon atoms in the one or more aromatic molecules. Furthermore, a superscript “+” or “−” may be used with an abbreviated one or more hydrocarbons notation, e.g., C 3+  or C 3− , which is inclusive of the abbreviated one or more hydrocarbons. As an example, the abbreviation “C 3+ ” means one or more hydrocarbon molecules of three or more carbon atoms. 
     As used herein, the term “zone” can refer to an area including one or more equipment items and/or one or more sub-zones. Equipment items can include, but are not limited to, one or more reactors or reactor vessels, separation vessels, distillation towers, heaters, exchangers, pipes, pumps, compressors, and controllers. Additionally, an equipment item, such as a reactor, dryer, or vessel, can further include one or more zones or sub-zones. 
     As used herein, the term “rich” can mean an amount of at least generally 50%, and preferably 70%, by mole, of a compound or class of compounds in a stream. 
     As used herein, the term “substantially” can mean an amount of at least generally 80%, preferably 90%, and optimally 99%, by mole or weight, of a compound or class of compounds in a stream. 
     As used herein, the term “active metal” can include metals selected from IUPAC Groups that include 6, 7, 8, 9, 10, and 13 such as chromium, molybedenum, tungsten, rhenium, cobalt, nickel, platinum, palladium, rhodium, iridium, ruthenium, osmium, gallium, indium, copper, silver, zinc, and mixtures thereof. 
     As used herein, the term “modifier metal” can include metals selected from IUPAC Groups that include 11-17. The IUPAC Group 11 trough 17 includes without limitation sulfur, gold, tin, germanium, and lead. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawing figures depict one or more implementations in accord with the present concepts, by way of example only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements. 
         FIG. 1  is a schematic depiction of one embodiment of the method for saturating hydrocarbons. 
         FIG. 2  is a schematic depiction of another embodiment of the method for saturating hydrocarbons. 
         FIG. 3  is a schematic depiction of yet another embodiment of the method for saturating hydrocarbons. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the application and uses of the embodiment described. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
     In one embodiment as depicted in  FIG. 1 , the hydrocarbon feed  10  passes through a dryer  12  producing a dried hydrocarbon stream  14 . The dried hydrocarbon stream  14  then passes through a guard bed  16  to remove H 2 O, H 2 S, and other sulfur containing compounds to give a pretreated hydrocarbon stream  20 . The pretreated hydrocarbon stream  20  contains reduced contents of H 2 O, H 2 S, and other sulfur containing compounds. The amounts of H 2 O and sulfur contents are around 10-1000 and 20-1000 mol ppm (on an elemental sulfur basis), respectively. The amounts of H 2 O and sulfur containing compounds in the pretreated stream  20  are less than 20 and 1 mol ppm and preferably less than 10 and 0.1 mol ppm, respectively. 
     The pretreated hydrocarbon stream  20  is combined with a H 2  stream  22  and then enters the selective hydrogenation reactor  24 . The selective hydrogenation reactor  24  contains the selective hydrogenation catalyst  26 . The selective hydrogenation catalyst  26  is made up of at a least one hydrogenation component selected from Groups 6 through 10 supported on inorganic oxides to effect the utilization. Preferably the hydrogenation catalysts are made up of nickel, cobalt, palladium, platinum, copper, zinc, silver, gallium, indium, germanium, tin and the mixture of thereof, supported in inorganic oxides such as alumina, silica, magnesia and the mixture of thereof. The supports can take the shapes of extrudates and spheres; in particular ones that possess high geometric surface area to volume ratios. In addition, the catalyst may contain alkali or alkali earth elements. More preferably the catalysts are made up of palladium, platinum, and mixtures thereof. The total amount of metals is greater than 0.05 wt %, more preferably greater than 0.2 wt % and most preferably greater than 0.40 wt %. In addition the catalyst may contain elements selected from alkali and alkali earth groups at a level greater than 0.1 wt %. Furthermore, substantial amounts of the active metal components are located within 200 um from the exterior of the catalysts and preferably within 100 um from the exterior of the catalyst. The butadiene and olefin are preferentially saturated over aromatics at levels of greater than 50% and preferably greater than 70% with aromatics saturations maintained at less than 10%, preferably less than 5% and most preferably less than 2%. The operating pressures range from 40 psig to 300 psig, temperatures range from 60° C. to 350° C., hydrogen to olefin ratios from about 0.5 to about 4.0 and space velocity from 2 to 50 hr−1 WHSV. 
     In another embodiment, the guard bed is designed to remove H 2 O, while leaving H 2 S and sulfur containing compounds relatively intact as depicted in  FIG. 2 . In this embodiment illustrated in  FIG. 2 , the hydrocarbon stream  10  passes through a dryer  12  and the pretreated hydrocarbon  14  is combined with a hydrogen stream  22  before entering the selective hydrogenation reactor  24 . It is also contemplated that if the H 2 O content is low, for example a H 2 O content of around 100 ppm, there would be no need for a dryer. The selective hydrogenation reactor  24  contains the selective hydrogenation catalyst  26  made up of at a least a hydrogenation component selected from Groups 6 through 10 supported on inorganic oxides to effect the utilization. Preferably the hydrogenation catalysts are made up of nickel, cobalt, chromium, molybedinum, palladium, platinum, and the mixture of thereof, supported in inorganic oxides such as alumina, silica, magnesia and the mixture of thereof. Most preferably the selective hydrogenation catalysts are made up of nickel, cobalt, molybedenum, tungsten and mixtures of thereof. The total amount of metals is greater than 0.5 wt %, preferably greater than 2% and most preferably greater than 5%. The butadiene and olefin are preferentially saturated over aromatics at levels of greater than 50% and preferably greater than 70% with aromatics saturations maintained at less than 10%, preferably less than 5% and most preferably less than 2%. The operating pressures range from 40 to 300 psig and temperatures range from 60 to 350° C. and hydrogen to olefin ratios from about 0.5 to about 4.0. 
     In another embodiment as depicted in  FIG. 3 , the selective hydrogenation is performed over multiple reactors with inter-stage quenching. Inter-stage quenching may be accomplished via heat exchangers using the incoming hydrocarbon feed stream to remove the heat of saturation reaction. As illustrated in  FIG. 3 , hydrogen is divided and injected into the reactors so to operate saturation of individual olefins under optimized process conditions. Saturations of ethylene and propylene are thermodynamically favorable and can be substantially saturated at stoichiometric H 2  to olefin ratio and over wide temperature ranges. In contrast, saturation of butenes and especially isobutylene are thermodynamically limited and substantial conversions are favored at H 2  to olefin ratios appreciably higher than stoichiometric ratios and lower temperatures. Preferably the stoichiometric amount of H 2  required to saturate ethylene and propylene will be injected in the lead reactors, while the remaining unreacted H 2 , in excess of saturating ethylene and propylene, is injected into the lag reactors. Furthermore, in this embodiment the reacting effluent coming of the lead reactors, where the substantial saturation of ethylene and propylene takes place, would be quenched before combining with make-up H 2  stream and entering the lag reactor. Here, the saturation of butenes and especially isobutylene would take place under a process environment of lower temperatures and high H 2  to butene ratio to drive complete conversions. 
     In one embodiment as depicted in  FIG. 3 , the hydrocarbon feed  10  passes through a dryer  12  producing a dried hydrocarbon stream  14 . The dried hydrocarbon stream  14  passed through a guard bed  16  to remove H 2 O, H 2 S and other sulfur containing compounds to give a pretreated hydrocarbon stream  20  of reduced contents of H 2 O, H 2 S and sulfur containing compounds. The amounts of H 2 O and sulfur contents in the feed are around 10-1000 and 20-1000 mol ppm (on an elemental sulfur basis), respectively. The amounts of H 2 O and sulfur containing compounds in the pretreated stream  20  are less than 20 and 1 mol ppm and preferably less than 10 and 0.1 mol ppm, respectively. The pretreated hydrocarbon  20  is combined with a first H 2  stream  22  and then enters a first selective hydrogenation reactor  24 . The first selective hydrogenation reactor  24  contains the selective hydrogenation catalyst  26 . The first selective hydrogenation reactor effluent  28  is combined with a second H 2  stream  30  and then enters a second selective hydrogenation reactor  32 . The second selective hydrogenation reactor  32  contains the selective hydrogenation catalyst  34 . In another embodiment, the dried hydrocarbon stream  14  may not pass over the guard bed  16  but it may pass directly to the first selective hydrogenation reactor  24 . 
     The first selective hydrogenation catalyst  26  and the second selective hydrogenation catalysts  34  are made up of at a least one hydrogenation component selected from Groups 6 through 10 supported on inorganic oxides to effect the utilization. Preferably the hydrogenation catalysts are made up of chromium, molybdenum, tungsten, nickel, cobalt, palladium, platinum, copper, zinc, silver and the mixture of thereof, supported in inorganic oxides such as alumina, silica, magnesia and the mixture of thereof. In addition alkali and alkali earth elements may be included. It is contemplated that the first selective hydrogenation catalyst  26  and the second selective hydrogenation catalyst  34  may be the same. However, it is also contemplated that the first selective hydrogenation catalyst  26  and the second selective hydrogenation catalyst  34  may be different. 
     In this embodiment the butadiene and olefin are preferentially saturated at levels of greater than 60% and preferably greater than 80% with aromatics saturations maintained at less than 10%, preferably less than 5% and most preferably less than 2%. The operating pressures of the lead reactors range from 40 psig to 300 psig and temperatures range from 60° C. to 350° C. and hydrogen to ethylene and propylene molar ratios from about 0.5 to about 1.2. The operating pressures of lag reactors range from 70 psig to 400 psig and temperatures range from 60° C. to 280° C. and hydrogen to butene molar ratios from about 1.2 to about 5.0. The space velocity of the lead reactor ranges from 4 to 100 hr−1, which that of the lag reactor ranges from 4 to 30 hr−1 WHSV. 
     EXAMPLES 
     The following examples are intended to further illustrate the subject embodiments. These illustrations of embodiments are not meant to limit the claims of this subject matter to the particular details of these examples. These examples are based on pilot plant data. 
     As shown in Table 1, catalysts A and B were tested for selective hydrogenation of olefins in the feed stream where the feed stream contains both olefins and aromatics. Catalysts A and B are palladium containing catalysts supported on alumina. The alumina may include gamma and theta alumina Palladium is placed within 100 um from the exterior of the support. Catalyst B may contain lithium as well. 
     
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 catalyst 
                 A 
                 B 
               
               
                   
               
             
             
               
                   
                 support 
                 gamma Al2O3 
                 theta-Al2O3 
               
               
                   
                 cat shape 
                 extrudate 
                 sphere 
               
               
                   
                 Wt % metal 
                 0.5% Pd 
                 0.25% Pd, 0.21% Li 
               
               
                   
               
             
          
         
       
     
     The catalysts were tested in a fixed bed reactor using 6 ml of catalyst mixed with quartz sand to minimize the axial dispersion. The composition of the feed stream is shown in Table 2. Test conditions include 100 psig pressure over temperatures of 100° C. to 300° C. inlet temperatures and H 2  to total olefin molar ratios from about 0.7 to about 3.5 with WHSV of about 11 hr−1. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Component 
                 Wt % 
                 mol % 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Ethylene 
                 3.42 
                 4.90 
               
               
                   
                 Ethane 
                 22.45 
                 30.06 
               
               
                   
                 Propylene 
                 4.10 
                 3.92 
               
               
                   
                 Propane 
                 59.44 
                 54.27 
               
               
                   
                 1-butene 
                 1.34 
                 0.96 
               
               
                   
                 Isobutylene 
                 0.81 
                 0.58 
               
               
                   
                 Normal Butane 
                 5.10 
                 3.53 
               
               
                   
                 Isobutane 
                 0.92 
                 0.64 
               
               
                   
                 1,3 Butadiene 
                 0.03 
                 0.02 
               
               
                   
                 Benzene 
                 1.20 
                 0.62 
               
               
                   
                 Toluene 
                 0.72 
                 0.31 
               
               
                   
                 EB 
                 0.09 
                 0.03 
               
               
                   
                 pX 
                 0.14 
                 0.05 
               
               
                   
                 mX 
                 0.22 
                 0.08 
               
               
                   
                 oX 
                 0.03 
                 0.01 
               
               
                   
               
             
          
         
       
     
     Example 1 
     Catalyst A was tested as per the prescribed procedure described above. The results are shown in Table 3. As shown in Table 3 and Table 4, butadiene conversions are consistently at 100%. Olefin conversions are consistently greater than 90%. These results occur when H 2  to olefin molar ratios are greater than 1.0 at about 70 psig and 100 psig overall pressures over a temperature range from about 150° C. to about 220° C. bed temperatures. While the olefin conversions are high, the aromatics conversions are consistently below 2%. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Selective hydrogenation of Catalyst A at 110 psig 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 inlet temperature, ° C. 
                 160 
                 160 
                 160 
               
               
                   
                 bed temperature, ° C. 
                 179 
                 181 
                 182 
               
               
                   
                 pressure, psig 
                 110 
                 110 
                 110 
               
               
                   
                 H2/olefin molar ratio 
                 0.98 
                 1.17 
                 1.37 
               
               
                   
                 C2 = conversion, % 
                 97 
                 99.9 
                 99.9 
               
               
                   
                 C3 = conversion, % 
                 84.3 
                 99.6 
                 99.7 
               
               
                   
                 C4 = conversion, % 
                 72.6 
                 97.9 
                 100 
               
               
                   
                 butadiene conversion, % 
                 100 
                 100 
                 100 
               
               
                   
                 aromatics conversion, % 
                 0 
                 0.12 
                 1.71 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 Selective Hydrogenation of Catalyst A at 72 psig 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 inlet temperature, 
                 130 
                 200 
                 160 
                 130 
                 130 
                 160 
                 130 
               
               
                 ° C. 
               
               
                 bed temperature, 
                 152 
                 214 
                 179 
                 154 
                 155 
                 179 
                 155 
               
               
                 ° C. 
               
               
                 pressure, psig 
                 73 
                 73 
                 73 
                 72 
                 73 
                 73 
                 73 
               
               
                 H2/olefin molar 
                 0.98 
                 1.17 
                 1.17 
                 1.17 
                 1.37 
                 1.37 
                 1.56 
               
               
                 ratio 
               
               
                 HOS 
                 106 
                 155 
                 135 
                 112 
                 118 
                 139 
                 170 
               
               
                 C2= conversion, % 
                 98.3 
                 99.4 
                 99.5 
                 99.7 
                 99.7 
                 99.7 
                 99.8 
               
               
                 C3= conversion, % 
                 82.4 
                 97.7 
                 98 
                 98.7 
                 98.9 
                 98.6 
                 98.7 
               
               
                 C4= conversion, % 
                 65.3 
                 97.9 
                 94.7 
                 95.6 
                 97.2 
                 96.9 
                 96.9 
               
               
                 butadiene 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
               
               
                 conversion, % 
               
               
                 aromatics 
                 0 
                 0 
                 0 
                 0 
                 0.16 
                 0.21 
                 0.22 
               
               
                 conversion, % 
               
               
                   
               
             
          
         
       
     
     Example 2 
     Catalyst B was tested as per the prescribed procedure described above. The results are shown in Table 5. As shown in the Table 5, olefin conversions are consistently greater than 90% when H 2  to olefin molar ratios are greater than 1.0 at about 100 psig overall pressures and over a temperature range about 200° C. bed temperatures. While the olefin conversions are high, the aromatics conversions are consistently below 2%. 
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                 Selective hydrogenation of Catalyst B at 103 psig 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 inlet temperature, ° C. 
                 130 
                 133 
                 130 
                 131 
                 130 
               
               
                 bed temperature, ° C. 
                 171 
                 177 
                 172 
                 172 
                 172 
               
               
                 pressure, psig 
                 103 
                 103 
                 103 
                 104 
                 103 
               
               
                 H2/olefin molar ratio 
                 1.16 
                 1.28 
                 1.36 
                 1.55 
                 1.74 
               
               
                 C2 = conversion, % 
                 100 
                 100 
                 100 
                 100 
                 100 
               
               
                 C3 = conversion, % 
                 99.9 
                 99.4 
                 100 
                 100 
                 100 
               
               
                 C4 = conversion, % 
                 94.9 
                 95.5 
                 97.8 
                 100 
                 100 
               
               
                 butadiene conversion, % 
                 100 
                 100 
                 100 
                 100 
                 100 
               
               
                 aromatics conversion, % 
                 0.03 
                 0.07 
                 0.21 
                 0.69 
                 0.93 
               
               
                   
               
             
          
         
       
     
     It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present subject matter and without diminishing its attendant advantages. 
     SPECIFIC EMBODIMENTS 
     While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims. 
     A first embodiment of the invention is a method for saturating hydrocarbons comprising passing a hydrocarbon stream comprising butadiene to a guard bed wherein the hydrocarbon stream is contacted with an adsorbent to form a treated hydrocarbon stream; and passing the treated hydrocarbon stream and a hydrogen stream to a reaction zone containing a hydrogenation catalyst to form a reaction zone effluent stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the hydrocarbon stream comprises light paraffins, olefins, diolefins mainly butadiene, and aromatics, water, hydrogen sulfide, and other sulfur containing compounds. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the treated hydrocarbon stream comprise C 2 -C 4  paraffin and olefins, diolefins mainly butadiene, and aromatics. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the guard beds contains molecular sieves to remove H 2 O. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the guard beds contains molecular sieves to remove H 2 O and H 2 S. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the guard beds contain molecular sieves and metal or metal oxides that are capable of going through reduction-oxidation cycle to remove H 2 S and other sulfur containing compounds. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the reaction zone does not saturate more than 20% of aromatics in the treated hydrocarbon stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the reaction zone comprises multiple reactors in series having inter-stage quenching. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the inter-stage quenching includes dividing H 2  and injecting it into individual reactors. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the reaction zone operates at a temperature from about 60° C. (140° F.) to about 350° C. (662° F.). An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the reaction zone operates at a pressure from about 40 psig to about 300 psig. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, further comprising contacting the treated hydrocarbon stream with the hydrogenation catalyst in the reaction zone to selectively hydrogenate butadiene and olefins. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the hydrogenation catalyst comprise at least one active metals chosen from Groups 6 through 10. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the hydrogenation catalyst comprises one of more of transition metals nickel, palladium, platinum, rhodium, iridium or mixtures thereof supported on inorganic metal oxides. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the hydrocarbon stream comprises olefins and the reaction zone effluent stream comprises a reduced olefin content relative to the treated hydrocarbon stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein hydrogenation catalyst contains at least one Group VIII metal selected from nickel, palladium, platinum and mixtures thereof supported on an inorganic oxide. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein overall H 2  to olefin molar ratios range from 0.5 to 5.0. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the guard bed operates over a cycle from 2 to 48 hours. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein diolefins comprise greater than 50% butadiene. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein diolefins comprise greater than 50% butadiene. 
     Without further elaboration, it is believed that using the preceding description that one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of this invention, without departing from the spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limiting the remainder of the disclosure in any way whatsoever, and that it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims. 
     In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.