High temperature corrosion inhibitor

Abstract

A process for the inhibition of corrosion caused by naphthenic acid during the elevated temperature processing of crude oil or the high temperature distillates derived therefrom by use of a treatment comprising (I) tetra functional substituted aromatic compounds and (II) esters or anhydrides of trimellitic acid.

1 . A method for inhibiting corrosion of the internal metallic surfaces of equipment used in the processing of crude oil or high temperature distillates heated to temperatures of between about 350° F. and about 790° F. comprising adding to the crude oil or high temperature petroleum distillate a corrosion inhibiting amount of a corrosion inhibitor selected from the groups (I) and (II) and mixtures thereof, wherein said corrosion inhibitor (I) has the formula:  
     
       
         
         
             
             
         
       
     
     wherein W, X, Y, and Z are all present and are the same or different and are individually selected from the groups consisting of OH; COOH; and COOR 1 , with the proviso that vicinal pairs of W, X, Y, and Z may be selected from  
     
       
         
         
             
             
         
       
     
     R 1  is an alkyl moiety having from about 1 to 16 carbon atoms and Ar is an aromatic compound; 
 said corrosion inhibitor (II) having the formula  
                     
 wherein R 2  and R 3  are COOR 5 ,  
                     
 with the proviso that when one of R 2  or R 3  is  
                     
 then the other is either  
                     
 sufficient to form an anhydride group linking the R 2  and R 3  functions, each R 5  is individually selected from alkyl groups having from about 1 to about 16 carbon atoms; R 4  is COOR 6  wherein R 6  is an alkyl group having from about 1 to about 16 carbon atoms.  
 
   
   
       2 . The method as recited in  claim 1  wherein Ar is substituted benzene.  
   
   
       3 . The method as recited in  claim 2  wherein said corrosion inhibitor (I) is selected from the group consisting of gallic acid, pyromellitic acid, propyl gallate, octyl gallate, tetra octyl pyromellitate, and 1,2,4,5-benzenetetracarboxylic dianhydride.  
   
   
       4 . The method as recited in  claim 3  wherein said corrosion inhibitor (I) is pyromellitic acid.  
   
   
       5 . The method as recited in  claim 2  wherein the corrosion inhibitor (II) is selected from 1,2,4-benzenetricarboxylic anhydride and trioctyltrimellitate.  
   
   
       6 . The method as recited in  claim 3  wherein said crude oil or petroleum distillate comprises naphthenic acid and said corrosion inhibitor is naphthenic acid induced corrosion.  
   
   
       7 . The method as recited in  claim 6  wherein said crude oil or petroleum distillate further comprises a sulfur containing compound.  
   
   
       8 . The method as recited in  claim 1  wherein the amount of corrosion inhibitor (I) and/or (II) added to the crude oil or distillate is an amount sufficient to generate a concentration of from about 1-5,000 ppm by volume.  
   
   
       9 . The method as recited in  claim 8  wherein the concentration is from about 100 to about 1500 ppm.  
   
   
       10 . The method as recited in  claim 3  wherein said corrosion inhibitor is 1,2,4,5-benzenetetracarboxylic dianhydride.