Mannich bases useful in middle distillate fuel having improved storage stability

Abstract

 Mannich Bases derived from a hindered phenol, formaldehyde and an amine are useful as stabilizers for middle distillate fuels.

Description

[0001] This invention relates generally to Mannich Bases useful for improving the stability of middle distillate fuels, more particularly when used in combination with N,N-dimethylcyclohexyl amine. This Application is a divisional of our Application No. 90301791.1 (Publication No. 0385633).

[0002] Middle distillate fuels such as diesel oil, fuel oil, jet fuel and kerosene when stored for long periods of time are subject to the formation of colour and solid deposits. The deposits accumulate on filters causing the filters to become plugged. Various additives and combinations of additives have been employed to reduce colour and deposit formation. For example: U.S. Patent 2,984,550 discloses the use of Mannich bases derived from phenols, formaldehyde and polyamines for stabilization; U.S. Patent 3,490,882 discloses stabilized petroleum distillate fuel oils containing N,N-dimethylcyclohexylamine antioxidant and a N,N′-di(ortho-hydroxyarylidene)-1,2-­alkylenediamine metal deactivator such as N,N′-disalicylidene-1,2-propylenediamine; U.S. Patent 4,166,726 discloses a fuel additive which is a mixture of a polyalkylene amine and a Mannich Base; and U.S. Patents 4,501,595 and 4,533,361 disclose diesel oil which contains a condensate of tetraethylene pentamine, paraformaldehyde, a hindered phenol such as 2,6-di-t-butylphenol and polyisobutenyl succinic anhydride.

[0003] The effectiveness of any particular type of additive combination can vary with different fuel stocks and combinations which are more effective at the same total additive concentration reduce treatment cost. In our aforesaid present Application No. 90301791.1 we have described and claimed novel, synergistic additive combinations which include certain Mannich Bases and provide middle distillate fuels having generally improved storage stability compared to fuels containing the same total concentrations of either N,N-dimethylcyclohexylamine antioxidant alone or N,N-dimethylcyclohexylamine in combination with an N,N′-di-(ortho-hydroxyarylidene)-1,2-­alkylenediamine metal deactivator.

[0004] The Mannich Base component of the compositions of our aforesaid Application is produced by the Mannich condensation reaction of a (a) hindered phenol having the formula:

where R₁, R₂, R₃ are independently selected from hydrogen, t-butyl, t-amyl and isopropyl, provided that at least one of R₁, R₂ and R₃ is hydrogen and at least one of R₁ and R₂ is t-butyl, t-amyl or isopropyl; or a (b) p-alkyl phenol having the formula:

where R₄ is C₉ to C₃₀ alkyl, an aldehyde, such as formaldehyde, ethanal, propanal, and butanal (preferably formaldehyde in its monomeric form or paraformaldehyde) and primary and secondary amines.

[0005] Of these Mannich Bases, those of the formula:

where R₁ and R₂ are independently selected from hydrogen, t-butyl, t-amyl and isopropyl provided that at least one of R₁ and R₂ is t-butyl, t-amyl, or isopropyl, or of the formula:

where R₁ and R₂ are independently selected from hydrogen, t-butyl, t-amyl and isopropyl provided that at least one of R₁ and R₂ is t-butyl, t-amyl, or isopropyl are novel compounds.

[0006] The hindered phenols which are useful in preparing the Mannich Bases of the invention are phenols which are characterised by the presence of at least one and preferably two ortho-t-butyl, t-amyl, and/or isopropyl groups. Specific examples of such hindered phenols include: 2,4-di-­t-butylphenol, 2,4-diisopropylphenol, 2,6-diisopropylphenol, 2-t-butylphenol, and 2-t-amylphenol with 2,6-di-t-­butylphenol being most preferred.

[0007] The amines which are useful in preparing the Mannich Base component of the invention include:

A. alkyl diamines of the formula;

where R₅ is selected from H and C₁ to C₅ alkyl, R₈ is C₁ to C₆ alkylene and A and B are independently selected from H, C₁ to C₅ alkyl, monohydroxysubstituted C₁ to C₅ alkyl, and the group (CH₂)_n-OR₇ where n = 1 to 10 and R₇ is C₁ to C₂₀ alkyl, and

B. cyclic amines of the formula;

where n and m are independently integers from 1 to 3, and X can be NH.

[0008] Specific examples of such amines include 1,3-di­aminopropane.

[0009] The Mannich Base can be formed by reacting from 1 to 5 moles of aldehyde, from about 1 to 2 moles of amine and from 1 to 4 moles of phenol at a temperature of from 0°C to 150°C for 0.5 to 10 hours. A inert solvent such as isopropanol can be used which is distilled from the product along with water formed in the reaction.

[0010] The Mannich Base product is usually a mixture of materials which may contain unreacted ingredients, especially the phenol. The Mannich Bases can be isolated from the product mixture but the product mixture itself can conveniently be used in forming the compositions of the invention. Examples of Mannich reactions and products are illustrated below:

where R₁ and, R₂ are as defined above.

[0011] The invention is further illustrated by, but is not intended to be limited to, the following Examples wherein parts are parts by weight unless otherwise indicated.

Example 1

[0012] A Mannich Base reaction product of formaldehyde, 1,3-diaminopropane and 2,6-di-t-butylphenol is prepared by the following process.

[0013] Dissolve 103 grams (0.5 mole) of 2,6-di-t-­butylphenol in 100 grams of isopropyl alcohol (IPA) in a 500 ml round bottom flask. Add 18.5 grams (0.25 mole) of 1,3-diaminopropane dropwise over 15 minutes while the contents of the flask are stirred. There is an exotherm observed as the amine is added. Cool the contents of the flask to below 30°C and add a 10% excess, (44.6 grams 0.55 mole) of 37% aqueous formaldehyde solution dropwise over 30 minutes while maintaining the temperature below 30°C. Heat the contents of the flask to reflux and continue to reflux for one hour. Switch from reflux to distillation and distill off IPA/water mixture to 105°C. Apply 28 in. Hg vacuum to remove residual materials. The total product yield is 122.2 or 96% of theory which contains compounds of the Structure III and IV.

[0014] Additive blends of the reaction product were prepared and tested in different fuels using both the D 4625 43°C (110°F) Storage Stability Test, in which the colour change (using ASTM D1500) and the total insolubles in the fuel (reported in mg/100 ml) are determined on 400 ml samples stored for 13 weeks in the dark and the F-21-61 149°C (300°F) Accelerated Stability Test in which the colour change and insoluble gums are determined on 50 ml samples heated to 149°C for a selected time, which was 90 minutes, allowed to cool in the dark, tested for colour (ASTM D1500), and then filtered (using a 4.25 cm Whatman #1 filter paper) and the filtrate discarded. The filter is washed clean of fuel with isooctane and measured for deposits by comparison with a set of reference papers. The blend compositions and test results in comparison to untreated fuel and blends without the Mannich Base product are reported in Table I below.

TABLE I

Composition in Pounds Per Thousand Barrels
	Fuel #1					Fuel #2			Fuel #3			Fuel #4
Components	1	2	3	4	5	1	2	3	1	2	3	1	2	3	4	5
DMCA¹	0.0	5.0	4.0	4.75	3.80	0.0	4.75	3.8	0.0	9.5	7.6	0.0	2.38	1.90	4.75	3.80
MDA²	0.0	0.0	0.0	0.25	0.25	0.0	0.25	0.24	0.0	0.5	0.5	0.0	0.12	0.12	0.25	0.24
Mannich Base	0.0	0.0	1.0	0.00	0.95	0.0	0.0	0.96	0.0	0.0	1.9	0.0	0.0	0.48	0.00	0.96
Total Additives	0.0	5.0	5.0	5.0	5.0	0.0	5.0	5.0	0.0	10.0	10.0	0.0	2.5	2.5	5.0	5.0

Test Results
149°C (F-21-61)
	Fuel #1					Fuel #2			Fuel #3			Fuel #4
Components	1	2	3	4	5	1	2	3	1	2	3	1	2	3	4	5
Color	L7	L3.5	2.5	L3	2	8	3	3	8	L2.5	2	L2.5	2	2	2.5	L2.5
Deposit	13	5	4	4	2	17	10	5	17	5	3	6	4	4	4	4

43°C (D 4625)
	Fuel #1					Fuel #2			Fuel #3			Fuel #4
Components	1	2	3	4	5	1	2	3	1	2	3	1	2	3	4	5
Color	L5	4	4	4	L4	L3.5	L3.5	L3.5	L3.5	L3.5	L3.5	2.5	L2.5	L2.5	L2.5	L2.5
Deposit	6.8	3.2	2.4	2.5	1.8	7.9	4	4.7	6.7	3	2.1	2.2	2	1.6	1.3	1
L = less than

¹N,N-dimethylcyclohexylamine

²N,N′-disalicylidene-1,2-propylenediamine

Fuel #1 is Midwest Refinery

Fuel #2 is Mid-Continent #2 Diesel (Corning Crude)

Fuel #3 is Mid-Continent #2 Diesel (Ill. Basin Crude)

Fuel #4 is Midwest #2 Diesel (KS/Tx Crude)

[0015] A significant difference in stability at 149°C is indicated by a colour difference of about 1/2 number and/or a deposit difference of 2 numbers and a significant difference in stability at 43°C is indicated by a colour difference of about 1/2 number and a deposit difference of 20%. The results in Table I show that the blends of the invention which contain Mannich Base in addition to DMCA or DMCA and MDA gave significantly better overall stability when compared to comparable blends which did not contain the Mannich Base, for example, blend 3 vs blend 2 and blend 5 vs blend 4 of Fuel #1.

Claims

1. A Mannich Base of the formula:

where R₁ and R₂ are independently selected from hydrogen, t-butyl, t-amyl and isopropyl provided that at least one of R₁ and R₂ is t-butyl, t-amyl, or isopropyl, or of the formula:

where R₁ and R₂ are independently selected from hydrogen, t-butyl, t-amyl and isopropyl provided that at least one of R₁ and R₂ is t-butyl, t-amyl, or isopropyl.

2. A Mannich Base according to claim 1 wherein R₁ and R₂ are both t-butyl.

3. A Mannich Base according to claim 1 which is the reaction product of formaldehyde, 2,6-di-t-butyl phenol and 1,3-diaminopropane.