Corrosion inhibitor

Abstract

A composition and method of inhibiting corrosion caused by naphthenic acid in fluids includes using a combination of a thiophosphorus compound and a hydrogen sulfide scavenging compound. The hydrogen sulfide scavenging compound significantly enhances the performance of the thiophosphorus compound and may be included at relatively low levels in the composition. The treatment may be applied to fluids including crude oils and lighter fractions thereof.

1 . A method for inhibiting naphthenic acid corrosion in a fluid containing a corrosive amount of naphthenic acid, the method comprising adding to the fluid or to a feed therefor a thiophosphorus compound and a hydrogen sulfide scavenging compound, wherein the thiophosphorus compound and the hydrogen sulfide scavenging compound are in amounts such that corrosion is inhibited.  
   
   
       2 . The method of  claim 1  wherein the thiophosphorus compound and hydrogen sulfide scavenging compound are added as an admixture.  
   
   
       3 . The method of  claim 1  wherein the thiophosphorus compound has the general formula:  
     
       
         
         
             
             
         
       
     
     wherein R 1  is R 3 (OCH 2  CH 2 ) n —, or R 3 (OCH 2  CH 2 ) n O—, R 2  is the same as R 1  or is —XH, each X is independently sulfur or oxygen, provided however that at least one X is sulfur, R 3  is an alkyl group of about 6 to about 18 carbon atoms and n is an integer from 0 to about 12.  
   
   
       4 . The method of  claim 1  wherein the hydrogen sulfide scavenging compound has the general formula:  
       R 3 O(CH 2 ) n —,  
     wherein x is an integer of from about 1 to about 10; R 1  is independently selected from the group consisting of  
     
       
         
         
             
             
         
       
     
     cycloalkyl having about 4 to about 7 carbon atoms, phenyl, benzyl, alkyl having 1 to about 20 carbon atoms, and alkenyl having 1 to about 20 carbon atoms; R 3  is hydrogen, alkyl having from 1 to about 20 carbon atoms, alkenyl having 1 to about 20 carbon atoms, or aryl; n is an integer of 1 to 6; R 4 , R 5 , and R 6  are each independently selected from the group consisting of alkyl containing 1 to about 20 carbon atoms, and  
     
       
         
         
             
             
         
       
     
     R 7  is hydrogen or alkyl having 1 to about 20 carbon atoms, and is the same as R 2  with the proviso that only one of R 4 , R 5  and R 6  may be  
     
       
         
         
             
             
         
       
     
     and R 2  is independently selected from the group consisting of ═CH 2 , cyclohexyl,  
     
       
         
         
             
             
         
       
     
     alkyl containing 1 to about 20 carbon atoms, and alkenyl containing 1 to about 20 carbon atoms; and wherein S denotes at least one sulfur atom in the ring at any location.  
   
   
       5 . The method of  claim 1  wherein the fluid is a crude oil or a fraction thereof.  
   
   
       6 . The method of  claim 2  wherein the hydrogen sulfide scavenging compound is present in the admixture in an amount of from about 1 percent to about 10 percent by weight.  
   
   
       7 . The composition of  claim 6  wherein the hydrogen sulfide scavenging compound is present in the admixture in an amount of from about 4 percent to about 6 percent by weight.  
   
   
       8 . The composition of  claim 2  wherein the thiosphosphorus compound is present in the admixture in an amount of from about 40 percent to about 70 percent by weight.  
   
   
       9 . The composition of  claim 2  wherein the admixture further includes mineral oil.  
   
   
       10 . A composition useful for inhibiting naphthenic acid corrosion in a fluid containing a corrosive amount of naphthenic acid comprising an admixture comprising a thiophosphorus compound and a hydrogen sulfide scavenging compound.  
   
   
       11 . The composition of  claim 10  wherein the fluid is a crude oil or a fraction thereof.  
   
   
       12 . The composition of  claim 10  wherein the hydrogen sulfide scavenging compound is present in the admixture in an amount of from about 1 percent to about 10 percent by weight.  
   
   
       13 . The composition of  claim 12  wherein the hydrogen sulfide scavenging compound is present in the admixture in an amount of from about 4 percent to about 6 percent by weight.  
   
   
       14 . The composition of  claim 10  wherein the thiosphosphorus compound is present in the admixture in an amount of from about 40 percent to about 70 percent by weight.  
   
   
       15 . The composition of  claim 10  wherein the admixture further includes mineral oil.  
   
   
       16 . The composition of  claim 10  wherein the thiophosphorus compound has the general formula:  
     
       
         
         
             
             
         
       
     
     wherein R 1  is R 3  (OCH 2  CH 2 ) n —, or R 3  (OCH 2  CH 2 ) n O—, R 2  is the same as R 1  or is —XH, each X is independently sulfur or oxygen, provided however that at least one X is sulfur, R 3  is an alkyl group of about 6 to about 18 carbon atoms and n is an integer from 0 to about 12.  
   
   
       17 . The composition of  claim 10  wherein the hydrogen sulfide scavenging compound has the general formula  
       R 3 O(CH 2 ) n —,  
     wherein x is an integer of from about 1 to about 10; R 1  is independently selected from the group consisting of  
     
       
         
         
             
             
         
       
     
     cycloalkyl having about 4 to about 7 carbon atoms, phenyl, benzyl, alkyl having 1 to about 20 carbon atoms, and alkenyl having 1 to about 20 carbon atoms; R 3  is hydrogen, alkyl having from 1 to about 20 carbon atoms, alkenyl having 1 to about 20 carbon atoms, or aryl; n is an integer of 1 to 6; R 4 , R 5 , and R 6  are each independently selected from the group consisting of alkyl containing 1 to about 20 carbon atoms, and  
     
       
         
         
             
             
         
       
     
     R 7  is hydrogen or alkyl having 1 to about 20 carbon atoms, and is the same as R 2  with the proviso that only one of R 4 , R 5  and R 6  may be  
     
       
         
         
             
             
         
       
     
     and R 2  is independently selected from the group consisting of ═CH 2 , cyclohexyl,  
     
       
         
         
             
             
         
       
     
     alkyl containing 1 to about 20 carbon atoms, and alkenyl containing 1 to about 20 carbon atoms; and wherein S denotes at least one sulfur atom in the ring at any location.