Patent Publication Number: US-2010108569-A1

Title: Mild cracking of paraffins

Description:
FIELD OF THE INVENTION 
     The present invention relates to a process for the mild cracking of paraffins. In another aspect, this invention relates to a process for the mild cracking of C 7 + paraffins using a supported ionic liquid. 
     BACKGROUND OF THE INVENTION 
     It is known that ionic liquids can be used in various hydrocarbon conversion processes. However, we have found an ionic liquid dispersed on a support which is unexpectedly effective at mildly cracking paraffins at moderate conversion conditions. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a process is provided including the following: 
     (a) contacting a hydrocarbon feed stream comprising C 7 + paraffins having at least seven carbon atoms per molecule with a composition comprising an ionic liquid supported on silica thereby producing a product stream comprising light paraffins having in the range of from four to six carbon atoms per molecule; wherein the ionic liquid has the formula: AB, wherein: 
     A is a cation capable of forming an ionic liquid, and 
     B is an anion containing aluminum and a halogen which is capable of forming an ionic liquid. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The hydrocarbon feed stream of the present invention can be any feed comprising, consisting of, or consisting essentially of C 7 + paraffins having at least seven carbon atoms per molecule, preferably in the range of from seven to thirty carbon atoms per molecule, more preferably in the range of from seven to fifteen carbon atoms per molecule, and most preferably in the range of from seven to twelve carbon atoms per molecule. Typically, the feed is a heavy straight run naphtha having a boiling range between around 180° F. and around 380° F. Preferably, C 7 + paraffins are present in the hydrocarbon feed stream in an amount in excess of about 50 weight %, more preferably in an amount in excess of about 70 weight %, and most preferably in an amount in excess of about 90 weight %. 
     The hydrocarbon feed stream is contacted with a composition comprising an ionic liquid supported on silica thereby producing a product stream comprising light paraffins having in the range of from four to six carbon atoms per molecule. The silica of the composition is preferably non-crystalline. The ionic liquid preferably has the formula: AB, wherein: 
     A is a cation capable of forming an ionic liquid, and B is an anion containing aluminum and a halogen which is capable of forming an ionic liquid. 
     A is preferably (CH 3 ) 3 NH + , and B is preferably an anion selected from the group consisting of Al 2 Cl 7   − , AlCl 4   − , Al 3 CL 10   − , and combinations thereof. 
     The ionic liquid is present in the composition in an amount in the range of from about 50 wt. % to about 90 wt. %, preferably in the range of from about 60 wt. % to about 90 wt. %, and more preferably in the range of from about 70 wt. % to about 85 wt. %. Silica is present in the composition in an amount in the range of from about 10 wt. % to about 50 wt. %, preferably in the range of from about 10 wt. % to about 40 wt. %, and more preferably in the range of from about 15 wt. % to about 30 wt. %. 
     The hydrocarbon feed stream is contacted with the composition at a temperature in the range of from about 50° C. to about 150° C., preferably at a temperature in the range of from about 60° C. to about 100° C., and more preferably at a temperature in the range of from about 70° C. to about 95° C.; at a pressure in the range of from about 25 psig to about 650 psig, preferably at a pressure in the range of from about 100 psig to about 550 psig, and more preferably at a pressure in the range of from about 150 psig to about 300 psig; and at a liquid hourly space velocity of about 0.1 hr. −1  to about 3 hr. −1 , preferably at a liquid hourly space velocity of about 0.2 hr. −1  to about 2 hr. −1 , and more preferably at a liquid hourly space velocity of about 0.25 hr. −1  to about 1 hr. −1 . 
     The light paraffins of the product stream preferably contain isobutane, and more preferably contain isobutane, isopentane, and hexane isomers (such as 2,2 dimethylbutane, 2-methylpentane and 3-methylpentane). 
     Preferably at least about 10%, more preferably at least about 15%, and more preferably at least about 20% by weight of the C 7 + paraffins of the hydrocarbon feed stream are converted to the light paraffins of the product stream. 
     The light paraffins of the product stream preferably contain at least about 40 weight %, and more preferably at least about 70 weight % isoparaffins having from three to six carbon atoms per molecule. 
     The following example is provided to further illustrate this invention and is not to be considered as unduly limiting the scope of this invention. 
     EXAMPLES 
     A 7.38 gram quantity of AlCl 3  was mixed with 2.71 grams of trimethylammonium chloride (N(CH 3 ) 3 :HCl) (at approximately 2 equivalents AlCl 3  and 1 equivalent (N(CH 3 ) 3 :HCl)) to form an ionic liquid. A 1.98 gram quantity of silica spheres, having a surface area greater than about 400 m 2 /g, a pore volume of 3.0 cc/g, and an average pore diameter of 308 Å, were added to the ionic liquid along with 17.01 grams of the inert support Alundum alumina to form a mixture. The mixture was then charged to a reactor. 
     A n-heptane feed was charged to the reactor at 90° C., 300 psig and varying liquid hourly space velocities. Results of such are presented in the Table below. 
     
       
         
           
               
               
             
               
                   
                 TABLE 
               
             
            
               
                   
                   
               
               
                   
                 TOS, Hrs. 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Feed 
                 1 
                 2 
                 3 
                 4 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 LHSV, hr −1   
                   
                 ~0.5 
                 ~0.5 
                 ~0.5 
                 ~0.5 
               
               
                 Component (wt. %) 
               
               
                 C 3   
                 0.00 
                 0.46 
                 0.02 
                 0.44 
                 0.36 
               
               
                 iC 4   
                 0.00 
                 6.40 
                 6.01 
                 4.22 
                 3.13 
               
               
                 n-C 4   
                 0.00 
                 1.37 
                 1.11 
                 0.74 
                 0.51 
               
               
                 i-C 5   
                 0.00 
                 7.26 
                 5.68 
                 4.10 
                 3.04 
               
               
                 2-MB-1 
                 0.00 
                 1.08 
                 0.79 
                 0.53 
                 0.36 
               
               
                 n-C 5   
                 0.00 
                 0.57 
                 0.40 
                 0.26 
                 0.16 
               
               
                 2,2-DMC4 
                 0.00 
                 3.72 
                 2.86 
                 2.10 
                 1.57 
               
               
                 2-MC5 
                 0.00 
                 1.46 
                 1.12 
                 0.83 
                 0.62 
               
               
                 3-MC5 
                 0.00 
                 2.20 
                 2.29 
                 2.22 
                 1.95 
               
               
                 n-C 6   
                 0.00 
                 1.01 
                 0.00 
                 0.00 
                 0.00 
               
               
                 2-MC6 
                 0.00 
                 0.35 
                 0.27 
                 0.21 
                 0.17 
               
               
                 n-C 7   
                 99.52 
                 65.91 
                 71.65 
                 78.95 
                 83.87 
               
               
                 Others 
                 0.48 
                 8.21 
                 7.2 
                 5.4 
                 4.26 
               
               
                 Total 
                 100 
                 100 
                 100 
                 100 
                 100 
               
               
                 n-C 7  conversion % 
                 — 
                 33.8 
                 28.0 
                 20.7 
                 15.7 
               
               
                 Wt. % C 4 -C 6   
                 — 
                 86.5 
                 86.0 
                 84.8 
                 84.7 
               
               
                 hydrocarbons in Product 
               
               
                 on n-C 7  free basis 
               
               
                   
               
            
           
         
       
     
     As can be seen in the Table, the silica supported ionic liquid of this invention results in conversion of n-heptane to lower molecular weight paraffins and isoparaffins (including isobutane, isopentane, 2,2 dimethylbutane, 2-methylpentane and 3-methylpentane) at moderate conversion conditions. 
     While this invention has been described in detail for the purpose of illustration, it should not be construed as limited thereby but intended to cover all changes and modifications within the spirit and scope thereof.