Desulfurization of hydrocarbons by ionic liquids and preparation of ionic liquids

Abstract

The present invention relates to an improved desulfurization process using an ionic liquid compound of general formula C + A − , where C + represents an organic cation such as alkyl-pyridinium, di-alkyl imidazolium and tri-alkyl imidazolium; and A − is an anion of halides of iron (III), such as, for example, FeCl 4 − . The desulfurization process is also improved when producing the ionic liquid compound by heating the reactants using microwave energy. The ionic liquids can be used to desulfurize hydrocarbon mixtures by a liquid-liquid extraction.

What is claimed is: 
     
         1 . An ionic liquid for the desulfurization of hydrocarbons, comprising a heterocyclic cation and an iron (III) halide anion wherein said ionic liquid is capable of removing sulfur and sulfur compounds from a liquid hydrocarbon. 
     
     
         2 . The ionic liquid according to  claim 1 , wherein the ionic liquid is symmetrical or asymmetrical and the heterocyclic cation is imidazolium or a derivative thereof having linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups having from 1 to 10 carbon atoms; linear or branched alkoxy groups or functionalized alkyl groups having one heteroatom selected from the group consisting of N, O and S or halogen atoms. 
     
     
         3 . The ionic liquid according to  claim 2 , wherein the anion is a halide of iron (III) derived from FeCl 3 . 
     
     
         4 . The ionic liquid according to  claim 2 , wherein said heterocyclic anion has the formula 
       
         
           
           
               
               
           
         
       
       R 1 , R 2 , and R 3  are independently selected from group consisting of hydrogen; linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups having from 1 to 10 carbon atoms; linear or branched alkoxy groups or functionalized alkyl groups having one heteroatom selected from N, O and S or halogen atoms and the anion is FeCl 4   − . 
     
     
         5 . The ionic liquid according to  claim 4 , wherein the imidazolium cation is symmetrical when R 1  is the same as R 2  or asymmetrical where R 1  is not the same as R 2 . 
     
     
         6 . The ionic liquid according to  claim 1 , wherein said heterocyclic anion has the formula 
       
         
           
           
               
               
           
         
       
       wherein the pyridine nucleus is substituted with at least one group selected from a linear or branched C 1 -C 10  alkyl. 
     
     
         7 . The ionic liquid according to  claim 6 , wherein R 1 , and R 2  are independently selected from group consisting of hydrogen, linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups having from 1 to 10 carbon atoms. 
     
     
         8 . The ionic liquid according to  claim 6 , wherein R 1  is a hydrogen atom and R 2  is a C 2  to C 10  alkyl group and the anion is FeCl 4   − . 
     
     
         9 . A process for the synthesis of a symmetrical ionic liquid of  claim 2 , comprising the steps of:
 activating a secondary nitrogen with a trimethylsilyl group according to the following reaction step to form a 1-trimethylsilazane and N-trimethylsilylimidazol:
   Im+(CH 3 ) 3 SiNHSi(CH 3 ) 3 - Δ →Im-If(Me) 3 +(CH 3 ) 3 SiNH 2    I)
 
   alkylizing the reaction product with an alkyl chloride according to the following reaction step:
   Im-If(Me) 3 +2 CL-Alq→Alq-Im + -Alq CL −   II)
 
   and treating the precursor with FeCl 3  to produce an dialkylimidazolium tetrachloroferrate according to the following reaction step:
   Alq-Im + -Alq CL − +FeCl 3 →Alq-Im + -Alq FeCl 4   −   III)
 
   where:   Im=Imidazolium   (CH 3 ) 3 SiNHSi (CH 3 ) 3 =Hexamethylbisilazane   Im-If (Me) 3 =N-Trimethylsilylimidazolium   (CH 3 ) 3 SiNH 2 =Trimethylsilylamine   CL-Alq=Alkyl chloride   Alq-Im + -Alq CL − =Dialkyl imidazolium chloride   Alq-Im + -Alq FeCl 4   − =Dialkylimidazolium tetrachloroferrate   
     
     
         10 . A process for the synthesis of asymmetrical ionic liquids of  claim 2 , comprising the steps of:
   HetCic-N+CL-Alq- Δ →HetCic-N + -Alq CL −   I)
   and treating the reaction product of step I with FeCl 3  to form an alkylimidazolium tetrachloroferrate according to the following reaction:
   HetCic-N + -Alq CL − +Faith CL 3 →HetCic-N + -Alq FeCl 4   −   II)
 
   where:   HetCic-N=Heterocycle with nitrogen   HetCic-N + -Alq CL − =Alkyl imidazolium chloride   HetCic-N + -Alq FeCl 4   − =Alkyl imidazolium tetrachloroferrate   
     
     
         11 . The process of  claim 9 , wherein the first and second steps comprises irradiating the reaction mixture with microwave energy for 10 min. to 1 hr. 
     
     
         12 . The process of  claim 10 , wherein said first step comprises irradiating the reaction mixture with microwave energy for 10 min. to 1 hour. 
     
     
         13 . An ionic liquid composition comprising
 a hydrocarbon liquid containing sulfur compounds, and   an ionic liquid in an amount sufficient to remove the sulfur compounds from hydrocarbon liquid, said ionic liquid has a heterocyclic cation and an iron (III) halide anion.   
     
     
         14 . The ionic liquid composition according to  claim 13 , wherein the ionic liquid is symmetrical or asymmetrical and the heterocyclic cation is imidazolium or a derivative thereof having linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups having from 1 to 10 carbon atoms; linear or branched alkoxy groups or functionalized alkyl groups having one heteroatom selected from the group consisting of N, O and S or halogen atoms. 
     
     
         15 . The ionic liquid composition according to  claim 14 , wherein the anion is a halide of iron (III) derived from FeCl 3 . 
     
     
         16 . The ionic liquid composition according to  claim 14 , wherein said heterocyclic anion has the formula 
       
         
           
           
               
               
           
         
       
       R 1 , R 2 , and R 3  are independently selected from group consisting of hydrogen; linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups having from 1 to 10 carbon atoms; linear or branched alkoxy groups or functionalized alkyl groups having one heteroatom selected from N, O and S or halogen atoms and the anion is FeCl 4   − . 
     
     
         17 . The ionic liquid composition according to  claim 16 , wherein the imidazolium cation is symmetrical when R 1  is the same as R 2  or asymmetrical where R 1  is not the same as R 2 . 
     
     
         18 . The ionic liquid composition according to  claim 13 , wherein said heterocyclic anion has the formula 
       
         
           
           
               
               
           
         
       
       wherein the pyridine nucleus is substituted with at least one group selected from a linear or branched C 1 -C 10  alkyl. 
     
     
         19 . The ionic liquid composition according to  claim 18 , wherein R 1 , and R 2  are independently selected from group consisting of hydrogen, linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups having from 1 to 10 carbon atoms. 
     
     
         20 . The ionic liquid composition according to  claim 18 , wherein R 1  is a hydrogen atom and R 2  is a C 2  to C 10  alkyl group and the anion is FeCl 4   − .