Alkane dehydrogenation process

Abstract

Disclosed herein are processes for dehydrogenation of an alkane to an alkene using an iridium pincer complex. In the dehydrogenation reactions, hydrogen that is co-formed during the process must be removed for the chemical reaction to proceed and to prevent the excess hydrogen from poisoning the catalyst. In one embodiment the process comprises providing an alkane feedstock comprising at least one alkane and contacting the alkane with an iridium pincer complex in the presence of a hydrogen acceptor selected from the group consisting of ethylene, propene, or mixtures to form an alkene product. The processes disclosed herein can accomplish facile, low-temperature transfer dehydrogenation of alkanes with unprecedented selectivities and TONs at a reasonable rate of conversion.

That which is claimed is: 
     
         1 . A process for preparing alpha-olefins from an at least one alkane, comprising the steps of:
 providing an alkane feedstock in a gaseous phase comprising the at least one alkane;   contacting the at least one alkane in the gaseous phase with an iridium pincer complex in the presence of a gaseous hydrogen acceptor selected from the group consisting of ethylene, propene, and mixtures thereof; and   recovering an alpha-olefin product.   
     
     
         2 . The process of  claim 1 , wherein the at least one alkane in the gaseous phase is selected from the group consisting of a butane, a pentane, an octane, a nonane, a decane, a dodecane, and mixtures thereof. 
     
     
         3 . The process of  claim 1 , wherein the iridium pincer complex has a Formula 
       
         
           
           
               
               
           
         
         wherein M is K or a solid support; “n” is an integer from 0 to 4; and each L is independently H, alkyl, or alkene. 
       
     
     
         4 . The process of  claim 1 , wherein the iridium pincer complex is selected from the group consisting of: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         and mixtures thereof. 
       
     
     
         5 . The process of  claim 1 , wherein the iridium pincer complex is ( iPr4 PCP)Ir(C 2 H 4 ) or (p-OK- iPr4 PCP)Ir(C 3 H 6 ). 
     
     
         6 . The process of  claim 1 , wherein the iridium pincer complex is unsupported. 
     
     
         7 . The process of  claim 1 , wherein the iridium pincer complex is immobilized on a solid support. 
     
     
         8 . The process of  claim 7 , wherein the solid support is selected from the group consisting of a silica, a γ-alumina, a basic alumina, a florisil, and a neutral alumina. 
     
     
         9 . The process of  claim 8 , wherein the solid support is the florisil or the neutral alumina. 
     
     
         10 . The process of  claim 1 , wherein the contacting is performed at a reaction temperature of less than 300° C. 
     
     
         11 . The process of  claim 10 , wherein the reaction temperature is in a range of 160° C.-260° C. 
     
     
         12 . The process of  claim 10 , wherein the reaction temperature is about 240° C. 
     
     
         13 . The process of  claim 10 , wherein the reaction temperature is about 200° C. 
     
     
         14 . The process of  claim 10 , wherein the reaction temperature is about 160° C. 
     
     
         15 . The process  claim 1 , wherein the contacting is performed for up to 24 hours. 
     
     
         16 . The process of  claim 1 , wherein the contacting is performed for 10-100 minutes. 
     
     
         17 . The process of  claim 1 , wherein a selectivity to the alpha-olefin product is at least 20% of an alkene product. 
     
     
         18 . The process of  claim 17 , wherein the selectivity to the alpha-olefin product is at least 30% of the alkene product. 
     
     
         19 . The process of  claim 18 , wherein the selectivity to the alpha-olefin product is at least 50% of the alkene product. 
     
     
         20 . The process of  claim 17 , wherein a conversion of the at least one alkane to an alkene is at least 50%. 
     
     
         21 . The process of  claim 20 , wherein the conversion to an alkene is at least 75%. 
     
     
         22 . The process of  claim 21 , wherein the conversion to an alkene is at least 95%.