Process for improving thermostability of lubricant oils in internal combustion engines

Abstract

The present invention refers to a process to improve the thermostability of lubricant oils contained in an internal combustion engine, which process comprises operating the said engine with a fuel containing one or more ashless thermostability boosters selected from aromatic amines, substituted phenols and polycyclic phenolic compounds or mixtures thereof. The present invention further refers to a fuel additive composition and to a fuel composition comprising specific nitrogen-containing dispersants, carrier oils, the said ashless thermostability boosters, and optionally corrosion inhibitors and friction modifiers.

1 . A process for improving thermostability of a lubricant oil in an internal combustion the process, comprising:
 operating an internal combustion engine with a fuel comprising an effective amount of one or more ashless thermostability boosters selected from the group consisting of:   (A) an aromatic amine of formula (I):   
       
         
           
           
               
               
           
         
         (B) a substituted phenol of formula (II): 
       
       
         
           
           
               
               
           
         
       
       and
 (C) a polycyclic phenolic compound having up to 20 benzene rings per molecule,
 wherein: 
 R1 designates hydrogen or a C 1 - to C 24 -hydrocarbyl residue; 
 R2 designates a C 1 - to C 24 -hydrocarbyl residue which is optionally 
 a) substituted by one or more hydroxyl groups, one or more amino groups, or both, 
 b) interrupted by one or more oxygen, one or more sulphur, or both, or 
 both a) and b); 
 R3 and R4 designate independently hydrogen or a C 1 - to C 24 -hydrocarbyl residue; 
 R5 designates a residue of formula —C n H 2n —CO—OR8 or of a residue of formula —C m H 2m —S x —R9 wherein n and m are independently 0, 1, 2 or 3; 
 x is the number 1, 2, 3 or 4; 
 R8 designates a C 1 - to C 24 -hydrocarbyl residue; and 
 R9 designates hydrogen or a C 1 - to C 24 -hydrocarbyl residue; 
 R5 and R6 designate independently hydrogen or a C 1 - to C 24 -hydrocarbyl residues residue; 
 
 the polycyclic phenolic compound is obtainable by a process comprising reacting a tetrahydrobenzoxazine with one or more of the same or different phenols, one or more of the same or different tetrahydrobenzoxazines, or both. 
 
     
     
         2 . The process according to  claim 1 ,
 wherein the fuel is gasoline and   the internal combustion engine is a spark-ignited combustion engine.   
     
     
         3 . The process according to  claim 1 ,
 wherein the effective amount of the one or more ashless thermostability boosters in the fuel is from 1 to 3,000 ppm by weight.   
     
     
         4 . The process according to  claim 1 ,
 wherein R1 designates hydrogen;   R2 designates a phenyl residue which is optionally substituted by one or two C 1 - to C 24 -alkyl residues; and   R3 and R4 designate independently hydrogen or a C 1 - to C 24 -alkyl residue.   
     
     
         5 . The process according to  claim 1 ,
 wherein R5 designates a residue of formula —C n H 2n —CO—OR8, wherein n is 0, 1, 2 or 3;   R8 designates a C 1 - to C 24 -alkyl residue and   R5 and R6 designate independently a C 1 - to C 24 -hydrocarbyl residue.   
     
     
         6 . A fuel additive composition, comprising:
 (i) at least one nitrogen-containing dispersant (D) selected from the group consisting of:
 (D1) a polyisobutenyl monoamine, 
 (D2) a polyisobutenyl polyamine, 
 (D3) a Mannich reaction product of a substituted phenol with an aldehyde and a mono- or polyamine, and 
 (D4) a polyoxyalkylene which is terminated by a mono- or polyamino group; 
   (ii) in case of presence of (D1), (D2) or (D3), at least one carrier oil, which is substantially free of nitrogen, selected from the group consisting of a synthetic carrier oil and a mineral carrier oil;   (iii) the one or more ashless thermostability boosters of  claim 1 ;   (iv) optionally, a corrosion inhibitor (E); and   (v) optionally, a friction modifier (F).   
     
     
         7 . The fuel additive composition according to  claim 6 ,
 wherein the at least one nitrogen-containing dispersant (i) is a polyisobutenyl monoamine (D1) with a number average molecular weight of from 550 to 1000.   
     
     
         8 . The fuel additive composition according to  claim 6 , wherein the weight ratio of the at least one nitrogen-containing dispersant (i) to the one or more ashless thermostability boosters (iii) is from 0.25:1 to 15:1. 
     
     
         9 . A fuel composition, comprising:
 a major amount of a liquid fuel in gasoline boiling range and   a minor amount of the fuel additive composition according to  claim 6 .   
     
     
         10 . The fuel composition according to  claim 9 ,
 wherein the fuel additive composition comprises:   the at least one nitrogen-containing dispersant (i) in an amount of from 50 to 3000 ppm,   the at least one carrier oil (ii), if present, in an amount of from 10 to 2500 ppm,   the one or more ashless thermostability boosters (iii) in an amount of from 1 to 3000 ppm,   the corrosion inhibitor (iv), if present, in an amount of from 2 to 100 ppm, and   the friction modifier (v), if present, in an amount of from 5 to 2000 ppm.