Patent Publication Number: US-6033446-A

Title: Polyalkylpyrrolidines and fuel compositions containing the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to novel polyalkylpyrrolidines and derivatives thereof. In a further aspect, this invention relates to the use of these compounds in fuel compositions to prevent and control engine deposits. 
     2. Description of the Prior Art 
     It is well known in the art that liquid hydrocarbon combustion fuels, such as fuel oils and gasolines, tend to exhibit certain deleterious characteristics, either after long periods of storage or under actual operational conditions. Gasolines, for example, in operational use tend to deposit sludge and varnish at various points in the power system, including carburetor and intake valves. It is desirable, therefore, to find a means for improving liquid hydrocarbon fuels by lessening their tendency to leave such deposits. 
     U.S. Pat. No. 4,240,803 discloses a liquid hydrocarbon fuel composition comprising fuel and a detergent amount of an alkenyl succinimide prepared by reacting an alkenyl succinic acid or anhydride, wherein the alkenyl substituent is derived from a specific mixture of C 16  to C 28  olefins, with a polyalkylene polyamine. This patent teaches that for unexpected effectiveness as a liquid hydrocarbon detergent, it is essential that the alkenyl group attached to the succinimide be derived from a mixture of C 16  to C 28  olefins obtained as the &#34;bottoms&#34; product from an olefin oligomerization. 
     European Patent Application No. 376,578 discloses a three-component additive composition for reducing carbon deposits in internal combustion engines comprising (a) a polyalkylene succinimide, (b) a polyalkylene, and (c) a mineral oil. Also disclosed is a liquid fuel composition containing such additive composition, as well as a method for cleaning a gasoline internal combustion engine utilizing this composition. The sole example disclosed in this European application shows the use of a polyisobutylene succinimide additive in intake valve and carburetor cleanliness tests. However, no mention is made in the example of the type of polyamine used to prepare the succinimide or the molecular weight of the polyisobutylene substituent. 
     British Patent No. 1,486,144 discloses a gasoline additive composition comprising (a) a hydrocarbyl-substituted succinimide, (b) a polymer of a C 2  to C 6  unsaturated hydrocarbon, and (c) a paraffinic or naphthenic oil. Example 1 of the British patent discloses a polyisobutylene succinimide, wherein the polyisobutylene group has a molecular weight of about 900 and the imide moiety is derived from diethylene triamine, in combination with a paraffinic oil and about 28 weight percent of polypropylene having a molecular weight of about 800. This British patent further teaches that all three components are essential to achieving a reduction in carbonaceous deposits. 
     U.S. Pat. No. 4,039,300 discloses a composition for fueling an internal combustion engine equipped with at least one carburetor, which comprises a major amount of hydrocarbons boiling in the gasoline range, a minor amount of at least one detergent and a minor amount of mineral oil of lubricating viscosity comprising at least 50 percent by weight of aromatic hydrocarbons having an average molecular weight of 300 to 700, the detergent and oil being present in amounts sufficient to inhibit formation of deposits on the carburetor. Among the detergents disclosed are polyamino-polyalkylene alkenyl succinimides, preferably polyisobutenyl succinimides. Thus, the thrust of this patent is the use of an aromatic-rich mineral oil containing at least 50 percent aromatic hydrocarbons, in combination with known detergent additives. 
     U.S. Pat. No. 5,393,309 discloses a fuel additive composition comprising a polyisobutenyl succinimide derived from ethylenediamine or diethylenetriamine, wherein the polyisobutenyl group has an average molecular weight of about 1,200 to 1,500 and a nonvolatile paraffinic or naphthenic carrier oil, or mixture thereof 
     Likewise, European Patent Application No. 565,285 discloses a fuel composition comprising a major amount of a liquid hydrocarbon fuel and, in an amount to provide detergency, a polyisobutene succinimide derived from the reaction of a polyisobutene-substituted succinic acylating agent and an amine having at least one reactive hydrogen bonded to an amine nitrogen. The polyisobutene substituent is derived from a highly reactive polyisobutene. 
     Commonly assigned U.S. patent application Ser. No. 09/141,636, filed Aug. 28, 1998, discloses certain polyisobutanyl succinimides, wherein the polyisobutanyl group is derived from a highly reactive polyisobutene and has an average molecular weight of from about 500 to 5,000, which provide excellent control of engine deposits, especially on intake valves, when employed as additives in fuel compositions. 
     SUMMARY OF THE INVENTION 
     We have now discovered that certain polyalkylpyrrolidines provide excellent control of engine deposits, especially intake valve deposits, when employed as fuel additives in fuel compositions. The compounds of the present invention include those having the following formula: ##STR2## or a fuel-soluble salt thereof; wherein R 1  is a polyalkyl group having an average molecular weight in the range of from about 500 to 5,000; 
     R 2  is a straight- or branched-chain alkylene group having from about 2 to 6 carbon atoms; 
     R 3  is H or CH 3  ; and 
     x is an integer from about 0 to 4. 
     The present invention further provides a fuel composition comprising a major amount of hydrocarbons boiling in the gasoline or diesel range and a deposit-controlling effective amount of the compound of the present invention. 
     The present invention is also concerned with a fuel concentrate comprising an inert stable oleophilic organic solvent boiling in the range of from about 150° F. (65° C.) to 400° F. (205° C.) and from about 10 to 50 weight percent of the compound of the present invention. 
     Among other factors, the present invention is based on the discovery that certain polyalkylpyrrolidines, wherein the polyalkyl group has an average molecular weight of from about 500 to 5,000, provides excellent control of engine deposits, especially on intake valves, when employed as additives in fuel compositions. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The compounds of the present invention are polyalkylpyrrolidines having the following formula: ##STR3## or a fuel-soluble salt thereof; wherein R 1 , R 2 , R 3 , and x are as described above. 
     Preferably, R 1  is a polyalkyl group having an average molecular weight in the range of from about 500 to 3,000, more preferably from about 700 to 2,000, and most preferably from about 700 to 1,500. 
     In addition, R 1  is preferably a polyalkyl group derived from polypropylene, polybutene, or polyalphaolefin oligomers of 1-octene or 1-decene. More preferably, R 1  is a polyalkyl group derived from polyisobutene. Most preferably, R 1  is a polyalkyl group derived from a highly reactive polyisobutene containing at least about 20% of a methylvinylidene isomer. 
     Preferably, R 2  is a straight- or branched-chain alkylene group having from about 2 to 4 carbon atoms. Most preferably, R 2  contains about 2 or 3 carbon atoms. 
     Preferably, R 3  is H. 
     Preferably, x is an integer of from about 0 to 2. Most preferably, x is 0. 
     Fuel-soluble salts of the compounds of formula I can be readily prepared and such salts are contemplated to be useful for preventing or controlling engine deposits. Suitable salts include, for example, those obtained by protonating the amino moiety with a strong organic acid, such as an alkyl- or arylsulfonic acid. Preferred salts are derived from toluenesulfonic acid and methanesulfonic acid. 
     Definitions 
     Prior to discussing the present invention in further detail, the following terms will be defined. 
     The term &#34;pyrrolidine&#34; refers to the radical --C 4  H 7  N from pyrrolidine, having the general formula: ##STR4## 
     The term &#34;alkyl&#34; refers to both straight- and branched-chain alkyl groups. 
     The term &#34;lower alkyl&#34; refers to alkyl groups having from about 1 to 6 carbon atoms and includes primary, secondary, and tertiary alkyl groups. Typical lower alkyl groups include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, n-pentyl, n-hexyl, and the like. 
     The term &#34;polyalkyl&#34; refers to alkyl groups which are generally derived from polyolefins which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have from about 2 to 24 carbon atoms, and more preferably, from about 3 to 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene, and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene. 
     The term &#34;highly reactive polyisobutene&#34; refers to a polyisobutene wherein at least about 20% of the residual olefinic double bonds are of the vinylidene type, i.e., represented by the formula: ##STR5## 
     The term &#34;succinimide&#34; is understood in the art to include many of the amide, imide, etc. species that are also formed by the reaction of a succinic anhydride with an amine and is so used herein. The predominant product, however, is succinimide and this term has been generally accepted as meaning the product of a reaction of an alkenyl- or alkyl-substituted succinic acid or anhydride with a polyamine. Alkenyl or alkyl succinimides are disclosed in numerous references and are well known in the art. Certain fundamental types of succinimides and related materials encompassed by the term of art &#34;succinimide&#34; are taught in U.S. Pat. Nos. 2,992,708; 3,018,250; 3,018,291; 3,024,237; 3,100,673; 3,172,892; 3,219,666; 3,272,746; 3,361,673; 3,381,022; 3,912,764; 4,234,435; 4,612,132; 4,747,965; 5,112,507; 5,241,003; 5,266,186; 5,286,799; 5,319,030; 5,334,321; 5,356,552; 5,716,912, the disclosures of which are hereby incorporated by reference. 
     The term &#34;fuel&#34; or &#34;hydrocarbon fuel&#34; refers to normally liquid hydrocarbons having boiling points in the range of gasoline and diesel fuels. 
     General Synthetic Procedures 
     The polyalkylpyrrolidines of the present invention may be prepared by the following general methods and procedures. It should be appreciated that where typical or preferred process conditions (e.g., reaction temperatures, times, mole ratios of reactants, solvents, pressures, etc.) are given, other process conditions may also be used unless otherwise stated. Optimum reaction conditions may vary with the particular reactants or solvents used, but such conditions can be determined by one skilled in the art by routine optimization procedures. 
     The polyalkylpyrrolidines employed in the present invention are prepared by a process that initially involves a reaction of a polyalkenyl succinic anhydride of the formula: ##STR6## wherein R 4  is a polyalkenyl group as defined herein, with ammonia, ammonium hydroxide, methylamine or a suitable polyamine as detailed herein, to provide a polyalkenyl succinimide of the formula: ##STR7## wherein R 2 , R 3 , R 4 , and x are as defined herein. 
     The polyalkenyl succinic anhydride reactant contains a polyalkenyl group, R 4 , having an average molecular weight of from about 500 to 5,000, preferably about 500 to 3,000, more preferably about 700 to 2,000, and most preferably from about 700 to 1,500. 
     The polyalkenyl group on the polyalkenyl succinic anhydride employed is generally derived from polyolefins that are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have from about 2 to 24 carbon atoms, and more preferably, about 3 to 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene. 
     The preferred polyisobutenes used to prepare the presently employed polyalkenyl succinic anhydrides are polyisobutenes which comprise at least about 20% of the more reactive methylvinylidene isomer, preferably at least about 50% and more preferably at least about 70%. Suitable polyisobutenes include those prepared using BF 3  catalysts. The preparation of such polyisobutenes in which the methylvinylidene isomer comprises a high percentage of the total composition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808. Examples of suitable polyisobutenes having a high alkylvinylidene content include Ultravis 30, a polyisobutene having a number average molecular weight of about 1,300 and a methylvinylidene content of about 74%, and Ultravis 10, a polyisobutene having a number average molecular weight of about 950 and a methylvinylidene content of about 76%, both available from British Petroleum. 
     Polyalkenyl succinic anhydrides are well known in the art. Various methods for the preparation of polyalkenyl succinic anhydrides involving the reaction of an olefin and maleic anhydride have been described. Such methods include a thermal process and a chlorination process. The thermal process is characterized by thermal reaction of a chlorinated olefin with maleic anhydride, as described, for example, in U.S. Pat. Nos. 3,361,673 and 3,676,089, which are herein incorporated by reference. Alternatively, the chlorination process is characterized by the reaction of a halogenated olefin, such as a chlorinated polyisobutene, with maleic anhydride, as described, for example, in U.S. Pat. No. 3,172,892, which is herein incorporated by reference. 
     The polyalkenyl succinic anhydride is then reduced by reaction with a suitable hydrogenation catalyst, such as palladium on carbon or platinum oxide, to yield a polyalkyl succinic anhydride, i.e., ##STR8## wherein R 1 , R 2 , R 3 , and x are as defined herein. 
     Reacting the polyalkyl succinic anhydride with ammonia, ammonium hydroxide, methylamine or suitable polyamine will yield a polyalkyl succinimide, as shown in the following reaction. ##STR9## wherein R 1 , R 2 , R 3 , and x are as defined herein. 
     The above reaction will be apparent to those skilled in the art. The reaction of ammonia, ammonium hydroxide, methylamine or suitable polyamine, such as ethylenediamine or diethylenetriamine, with the polyalkyl succinic anhydride may be conducted in the absence of solvent, or alternatively, in the presence of an inert solvent, such as toluene, xylene, C 9  aromatic hydrocarbons, chloroform, 100 neutral oils, aliphatic hydrocarbons, and the like. The reaction is typically conducted at a temperature in the range of from about 80° C. to 200° C. Reaction temperatures in the range of from about 150° C. to 170° C. are generally preferred. 
     Particularly suitable polyalkylene polyamines are those having the formula: 
     
         H.sub.2 N--(R.sub.2 --NH).sub.x --H 
    
     wherein R 2  is a straight- or branched-chain alkylene group having from about 2 to 6 carbon atoms, preferably from about 2 to 4 carbon atoms, most preferably about 2 carbon atoms, i.e., ethylene (--CH 2  CH 2  --); and x is an integer from about 1 to 4, preferably from about 1 or 2. 
     Particularly preferred polyalkylene polyamines are ethylenediamine, diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine. More preferred are ethylenediamine and diethylenetriamine, especially ethylenediamine. 
     Many of the polyamines suitable for use in the present invention are commercially available and others may be prepared by methods that are well known in the art. For example, methods for preparing amines and their reactions are detailed in Sidgewick&#39;s &#34;The Organic Chemistry of Nitrogen&#34;, Clarendon Press, Oxford, 1966; Noller&#39;s &#34;Chemistry of Organic Compounds&#34;, Saunders, Philadelphia, 2nd Ed., 1957; and Kirk-Othmer&#39;s &#34;Encyclopedia of Chemical Technology&#34;, 2nd Ed., especially Volume 2, pp. 99-116. 
     Most preferably for the purposes of the present invention, the polyalkyl succinic anhydride will be reacted with ammonia or ammonium hydroxide, to provide the polyalkyl succinimide. 
     Alternatively, the polyalkenyl succinic anhydride may be first reacted with ammonia, ammonium hydroxide, methylamine or suitable polyamine. The resulting polyalkenyl succinimide may then be reduced to yield the polyalkyl succinimide with a suitable hydrogenation catalyst, such as palladium on carbon or platinum oxide. The reaction of ammonia, ammonium hydroxide, methylamine or suitable polyamine with an alkenyl or alkyl succinic anhydride to produce an alkenyl or alkyl succinimide is well known in the art and is described, for example, in U.S. Pat. Nos. 3,018,291; 3,024,237; 3,172,892; 3,219,666; 3,223,495; 3,272,746; 3,361,673; and 3,443,918. 
     The polyalkylpyrrolidines of the present invention are prepared by reducing the polyalkyl succinimide, as shown in the reaction below. ##STR10## wherein R 1 , R 2 , R 3 , and x are as defined herein. 
     Such reductions can readily be achieved by a variety of well known reducing agents apparent to those skilled in the art, such as complex metal hydrides and metal hydrides. The preferred class of reducing agents involves borane reagents, such as borane-dimethyl sulfide or borane-tetrahydrofuran complex. See for example, Braun et al., J. Org. Chem., 1982, 47, 3153-3163. The amount of borane reagent employed will generally range from about 2 to 10 equivalents. The reduction reaction will generally be conducted at temperatures ranging from about 0° C. to 150° C. and in the presence to a suitable solvent. Suitable solvents include, but are not limited to, tetrahydrofuran, diethyl ether, toluene, and dichloromethane. 
     Alternatively, the polyalkenyl succinimide can be reduced to the polyalkylpyrrolidine with a suitable hydrogenation catalyst under appropriate conditions. See, for example, Japanese Patent No. 06298727 and Dunet et al., Bull. Soc. Chim. France, 877-881,1950. 
     Fuel Compositions 
     The compounds of the present invention are useful as additives in hydrocarbon distillate fuels boiling in the gasoline or diesel range. The proper concentration of additive necessary in order to achieve the desired detergency and dispersancy varies depending upon the type of fuel employed, the presence of other detergents, dispersants, and other additives, etc. Generally, however, from about 35 to 7,500 ppm by weight, preferably from about 35 to 2,500 ppm, of the present additive per part of base fuel is needed to achieve the best results. 
     The deposit control additive may be formulated as a concentrate, using an inert stable oleophilic organic solvent boiling in the range of from about 150° F. to 400° F. Preferably, an aliphatic or an aromatic hydrocarbon solvent is used, such as benzene, toluene, xylene or higher-boiling aromatics or aromatic thinners. Aliphatic alcohols of from about 3 to 8 carbon atoms, such as isopropanol, isobutylcarbinol, n-butanol, and the like, in combination with hydrocarbon solvents are also suitable for use with the detergent-dispersant additive. In the concentrate, the amount of the present additive will be ordinarily at least from about 10 weight percent and generally not exceed about 70 weight percent, preferably from about 10 to 50 weight percent and most preferably from about 20 to 40 weight percent. 
     In gasoline fuels, other fuel additives may be employed with the additives of the present invention, including, for example, oxygenates, such as t-butyl methyl ether, antiknock agents, such as methylcyclopentadienyl manganese tricarbonyl, and other dispersants/detergents, such as hydrocarbyl amines, hydrocarbyl poly(oxyalkylene) amines, hydrocarbyl poly(oxyalkylene) aminocarbamates, succinimides, or Mannich bases. Additionally, antioxidants, metal deactivators and demulsifiers may be present. 
     In diesel fuels, other well-known additives can be employed, such as pour point depressants, flow improvers, cetane improvers, and the like. 
     A fuel-soluble, nonvolatile carrier fluid or oil may also be used with the polyalkylpyrrolidines of this invention. The carrier fluid is a chemically inert hydrocarbon-soluble liquid vehicle, which substantially increases the nonvolatile residue (NVR), or solvent-free liquid fraction of the fuel additive while not overwhelmingly contributing to octane requirement increase. The carrier fluid may be a natural or synthetic oil, such as mineral oil, refined petroleum oils, synthetic polyalkanes and alkenes, including hydrogenated and unhydrogenated polyalphaolefins, and synthetic polyoxyalkylene-derived oils. Such carrier fluids are described, for example, in U.S. Pat. No. 4,191,537, and polyesters, such as those described, for example, in U.S. Pat. Nos. 3,756,793 and 5,004,478, and in European Patent Application Nos. 356,726, published Mar. 7,1990, and 382,159, published Aug. 16, 1990. 
     These carrier fluids are believed to act as a carrier for the fuel additives of the present invention and to assist in removing and retarding deposits. The carrier fluid may also exhibit synergistic deposit control properties when used in combination with a polyalkylpyrrolidine of this invention. 
     The carrier fluids are typically employed in amounts ranging from about 35 to 7,500 ppm by weight of the hydrocarbon fuel, preferably from about 35 to 2,500 ppm of the fuel. Preferably, the ratio of carrier fluid to deposit control additive will range from about 0.5:1 to 10:1, more preferably from about 0.5:1 to 4:1, most preferably about 0.5:1 to 2:1. 
     When employed in a fuel concentrate, carrier fluids will generally be present in amounts ranging from about 20 to 60 weight percent, preferably from about 30 to 50 weight percent. 
    
    
     EXAMPLES 
     The following examples are presented to illustrate specific embodiments of this invention and are not to be construed in any way as limiting the scope of the invention. 
     Example 1 
     Preparation of ##STR11## 
     To a flask equipped with a mechanical stirrer, Dean-Stark trap, thermometer, reflux condenser, addition funnel and nitrogen inlet was added 523.5 grams of polyisobutenylsuccinic anhydride (0.5 moles, derived from polyisobutene which had an approximate molecular weight of 950 and a methylvinylidene content of 86%). The contents were heated to 60° C. and concentrated ammonium hydroxide (303.6 grams, 5.0 moles) was added dropwise. The mixture was heated to 160° C. for 18 hours while removing the water to yield a viscous oil after cooling to room temperature. The resultant oil was chromatographed on silica gel eluting with hexane followed by hexane/ethyl acetate (4:1) to yield 355.6 grams of the desired succinimide. 
     Example 2 
     Preparation of ##STR12## 
     A solution of 160 grams of polyisobutenylsuccinimide from Example 1 in 100 mL of ethyl acetate and 400 mL of toluene containing 15 grams of platinum (IV) oxide was hydrogenated at 40 psi for 48 hours on a Parr low-pressure hydrogenator. The catalyst was filtered away and the solvent was removed in vacuo to yield 157 grams of the desired polyisobutylsuccinimide. 
     Example 3 
     Preparation of ##STR13## 
     To a flask equipped with a magnetic stirrer, addition funnel, thermometer, reflux condenser and nitrogen inlet was added diborane (250 mL of a 1M solution in tetrahydrofuran, 0.25 moles). The solution was cooled to 0° C. and the polyisobutylsuccinimide from Example 2 (52 grams dissolved in 100 mL of anhydrous tetrahydrofuran) was added dropwise maintaining the temperature between 0-5° C. The reaction was then allowed to warm to room temperature and stirred for thirty minutes. The reaction was heated to reflux for 20 hours and then cooled to room temperature. Hydrochloric acid (50 mL of a 50% aqueous solution) was added dropwise and the solvents were removed in vacuo. Th residue was neutralized with 10% aqueous sodium hydroxide and extracted with diethyl ether (3×200 mL). The organic layers were dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo to yield a viscous oil. The oil was chromatographed on silica gel eluting with hexane/ethyl acetate (3:2), followed by hexane/diethyl ether/methanol/isopropylamine (44:44:15:5) to yield 29 grams of the desired pyrrolidine.  1  H NMR (CDCl 3 ) 0.8-3.2 (m, 145H). 
     Example 4 
     Deposit Control Evaluation 
     In the following tests, the polyalkylpyrrolidines of the present invention were blended in gasoline and their deposit control capacity tested in an ASTM/CFR Single-Cylinder Engine Test. 
     In carrying out the tests, a Waukesha CFR single-cylinder engine is used. Each run is carried out for 15 hours, at the end of which time the intake valve is removed, washed with hexane and weighed. The previously determined weight of the clean valve is subtracted from the weight of the valve. The difference between the two weights is the weight of the deposit. A lesser amount of deposit measured indicates a superior additive. The operating conditions of the test are as follows: water jacket temperature 200° F.; manifold vacuum of 12 in. Hg; air-fuel ratio of 12; ignition spark timing of 400 BTC; engine speed is 1,800 rpm; the crankcase oil is a commercial 30W oil. The amount of carbonaceous deposit in milligrams on the intake valves is measured and reported in the following Table I. 
     
                       TABLE 1                                                     
______________________________________                                    
       Intake Valve Deposit Weight                                        
       (in milligrams)                                                    
Sample.sup.1                                                              
         Run 1       Run 2   Average                                      
______________________________________                                    
Base Fuel                                                                 
         361.3       332.7   347.0                                        
Example 3                                                                 
                             0.8                                          
                                       0.5                                
______________________________________                                    
 .sup.1 At 50 parts per million actives (ppma) and 50 ppm of              
 hydroxy-4-dodecylphenoxypoly(oxypropylene) having an average of 12-13    
 oxypropylene units (prepared essentially as described in Example 6 of U.S
 Pat. No. 4,160,648) carrier oil.                                         
 
    
     The base fuel employed in the above single-cylinder engine tests was a regular octane unleaded gasoline containing no fuel detergent. The test compounds were admixed with the base fuel to give a concentration of 50 ppma (parts per million actives) and 50 ppm of α-hydroxy-ω-4-dodecylphenoxypoly(oxypropylene) having an average of 12-13 oxypropylene units (prepared essentially as described in Example 6 of U.S. Pat. No. 4,160,648) carrier oil. 
     The data in Table I illustrate the reduction in intake valve deposits provided by the polyalkylpyrrolidines of the present invention (Example 3), even at a very low concentration.