Use of a composition of additives for reducing diesel vehicle emissions

Abstract

The present invention relates to the use of a composition of additives for reducing emissions of nitrogen oxides and of at least one type of pollutant selected from carbon monoxide and hydrocarbons which are unburnt during the combustion of a liquid fuel in a compression-ignition internal combustion engine, said composition comprising: (i) one or more additive(s) selected from compounds having at least one alkylphenol group in their structure; and (ii) one or more additives which improve the cetane number, selected from alkyl nitrates, aryl peroxides and alkyl peroxides; wherein the weight ratio of the amount of additive(s) (i) to the amount of additive(s) (ii) is within the range from 1:3 to 3:1. The present invention also relates to a method for reducing emissions of nitrogen oxides and of at least one type of pollutant selected from carbon monoxide and hydrocarbons which are unburnt during the combustion of a liquid fuel in a compression-ignition internal combustion engine which employs this composition of additives.

1 . A method for reducing emissions of nitrogen oxides and at least one type of pollutant selected from carbon monoxide and unburnt hydrocarbons during combustion of a liquid fuel in a compression-ignition internal combustion engine, the method comprising adding a composition of additives to the liquid fuel, wherein the composition comprises:
 (i) one or more additives selected from compounds having at least one alkyl phenol group in their structure; and   (ii) one or more cetane number improving additives selected from alkyl nitrates, aryl peroxides and alkyl peroxides;   wherein the ratio by weight of the amount of additive(s) (i) to the amount of additive(s) (ii) is in the range from 1:3 to 3:1, and;   subjecting the liquid fuel to combustion in the compression-ignition internal combustion engine;   whereby emissions of nitrogen oxides and at least one type of pollutant selected from carbon monoxide and unburnt hydrocarbons are reduced compared to emissions from a combustion of the liquid fuel without the composition of additives in the compression-ignition internal combustion engine.   
     
     
         2 . The method according to  claim 1 , wherein the additive(s) (i) are selected from compounds (i)a) comprising one or two phenolic ring(s) substituted with one or more alkyl groups selected from methyl and t-butyl groups, and preferably from methyl-t-butyl phenols, dimethyl-t-butyl phenols, ethyl-t-butyl phenols, t-butyl phenols, di-t-butyl phenols, tri-t-butyl phenols, di-t-butyl-di-methyl phenols, and mixtures thereof. 
     
     
         3 . The method according to  claim 2 , wherein the compound(s) (i)a) are selected from (di)tert-butylphenols, methyl-tert-butylphenols and di-methyl-tert-butylphenols, mixtures thereof, and two-by-two condensation products thereof, such as in particular 2,6-di-t-butyl-4-methyl phenol (BHT), 2,4-dimethyl-6-t-butyl phenol, 2,5-dimethyl-4-t-butyl phenol, 2,6 and 2,4 di-t-butyl phenol, 2,4,6-tri-t-butyl phenol, mixtures thereof, and two-by-two condensation products thereof. 
     
     
         4 . The method according to  claim 1 , wherein the additive or additives (i) are selected from modified alkylphenol-aldehyde resins (i)b) obtainable by Mannich reaction of an alkylphenol-aldehyde condensation resin: 
       with at least one aldehyde, ketone or combination of aldehyde and ketone, having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms;
 and at least one hydrocarbon compound having at least one alkyl polyamine group, having between 1 and 30 carbon atoms, preferably between 4 and 30 carbon atoms, 
 
       said alkylphenol-aldehyde condensation resin itself being obtainable by condensation of:
 at least one alkylphenol substituted with at least one linear or branched alkyl group having from 1 to 30 carbon atoms, preferably a monoalkylphenol, 
 with at least one aldehyde and/or ketone having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms. 
 
     
     
         5 . The method according to  claim 4 , wherein the modified alkylphenol-aldehyde resins are obtainable from p-nonylphenol, formaldehyde and at least one hydrocarbon compound comprising at least one alkyl polyamine group. 
     
     
         6 . The method according to  claim 4 , wherein the modified alkylphenol-aldehyde resins are obtainable from at least one alkyl polyamine having at least two primary amine groups, and at least one fatty chain having from 12 to 24 carbon atoms, preferably from 12 to 22 carbon atoms. 
     
     
         7 . The method according to  claim 1 , wherein the composition of additives comprises one or more compounds (i)a) comprising one or two phenolic ring(s) substituted with one or more alkyl groups selected from methyl and t-butyl groups, and one or more modified alkylphenol-aldehyde resins (i)b). 
     
     
         8 . The method according to  claim 1 , wherein the additive or additives (ii) are selected from alkyl nitrates of the formula R—NO 3  with R an alkyl radical comprising from 2 to 12 carbon atoms, more preferably from 4 to 8 carbon atoms, and still better the additive (ii) is ethyl hexyl nitrate. 
     
     
         9 . The method according to  claim 1 , wherein the weight ratio of the amount of additive(s) (i) to the amount of additive(s) (ii) is in the range from 1:2.5 to 2.5:1. 
     
     
         10 . The method according to  claim 1 , wherein the composition of additives additionally comprises one or more deposit control additive(s) (iii) selected from the group consisting of amines, succinimides, alkenyl succinimides, polyalkylamines, polyalkyl polyamines, polyetheramines, quaternary ammonium salts and triazole derivatives; more preferably from polyisobutylene succinimides functionalised with a quaternary ammonium group, fatty acid amides functionalised with a quaternary ammonium group and dimers thereof such as di-(quaternary alkylamido-propyl-ammonium) compounds, fatty chain alkylamidoalkyl betaines and triazole derivatives; and even more preferably from polyisobutylene succinimides functionalised with a quaternary ammonium group and polyisobutylene succinimides functionalised with a triazole group. 
     
     
         11 . The method according to  claim 1 , wherein the ratio of the total content by weight of compounds (i) having at least one alkyl phenol group in their structure, to the total content by weight of deposit control additive(s) (iii), ranges from 1:60 to 1:2. 
     
     
         12 . The method according to  claim 1 , wherein the liquid fuel is selected from gas oils, biodiesels, B x -type gas oils containing x % (v/v) of vegetable or animal oil esters with x a number greater than zero and less than or equal to 100, hydrotreated vegetable oils (HVO), and mixtures thereof; and preferably from B x  type gas oils containing x % (v/v) vegetable or animal oil esters with x a number greater than zero and less than or equal to 100, the vegetable oil esters preferably being selected from fatty acid methyl esters and fatty acid ethyl esters. 
     
     
         13 . The method according to  claim 1 , wherein the emissions of nitrogen oxides, carbon monoxide and unburnt hydrocarbons are reduced simultaneously. 
     
     
         14 . The method according to  claim 1 , whereby emissions of solid particles are reduced compared to emissions of solid particles from a combustion of the liquid fuel without the composition of additives in the compression-ignition internal combustion engine. 
     
     
         15 . The method according to  claim 1 , wherein the compression-ignition internal combustion engine is a hybrid diesel engine or a direct-injection diesel engine. 
     
     
         16 . The method according to  claim 1 , wherein the compression-ignition internal combustion engine is a marine engine. 
     
     
         17 . (canceled) 
     
     
         18 . The method according to  claim 9 , wherein the weight ratio of the amount of additive(s) (i) to the amount of additive(s) (ii) is in the range from 1:2 to 2:1 or from 1:1 to 1.5:1. 
     
     
         19 . The method according to  claim 11 , wherein the ratio of the total content by weight of compounds (i) having at least one alkyl phenol group in their structure to the total content by weight of deposit control additive(s) (iii) ranges from 1:20 to 1:3. 
     
     
         20 . The method according to  claim 15 , wherein the direct-injection diesel engine is a diesel engine with a common-rail injection system.