Diesel fuel stabilizer

Details Diesel fuel stabilizer Diesel fuel stabilizer

2001-05-11

2004-01-13

Toomer, Cephia D. (Department: 1714)

Fuel and related compositions

Liquid fuels

Heterocyclic carbon compound containing a hetero ring having...

C044S331000, C044S332000, C044S333000, C044S334000, C044S335000, C044S336000, C044S338000, C044S339000, C044S340000, C044S341000, C044S343000, C044S346000, C044S347000, C044S349000, C044S350000, C044S351000, C044S352000, C044S353000

Reexamination Certificate

active

06676715

ABSTRACT:

The present invention relates to a diesel fuel stabiliser. In particular the present invention relates to a stabiliser for a diesel fuel containing a cetane improver.
As discussed in U.S. Pat. No. 5,482,518 fuel ignition in diesel engines is achieved through the heat generated by air compression, as a piston in the cylinder moves to reduce the cylinder volume during the compression stroke. In the engine, the air is first compressed, then the fuel is injected into the cylinder; as the fuel contacts the heated air, it vaporises and finally begins to burn as the self-ignition temperature is reached. Additional fuel is injected during the compression stroke and the fuel burns almost instantaneously, once the initial flame has been established. Thus, a period of time elapses between the beginning of fuel injection and the appearance of a flame in the cylinder. This period is commonly called “ignition delay” and must be relatively short in order to avoid “diesel knock”.
A major contributing factor to diesel fuel performance and the avoidance of “diesel knock” is the cetane number of the diesel fuel. Diesel fuels of higher cetane number exhibit a shorter ignition delay than do diesel fuels of a lower cetane number. Therefore, higher cetane number diesel fuels are desirable to avoid diesel knock. Most diesel fuels possess cetane numbers in the range of about 40 to 55 and a sulfur content of about 500 ppm and less. A correlation between ignition delay and cetane number has been reported in “How Do Diesel Fuel Ignition Improvers Work” Clothier, et al., Chem. Soc. Rev, 1993, pg. 101-108.
Cetane improvers have been used for many years to improve the ignition quality of diesel fuels. The use of cetane improvers is increasing due to the increased demand for diesel fuel which has resulted in a widening of the fraction recovered, the so called middle distillate fraction, and the lower natural cetane number of diesel base stocks caused by more severe refining of crude oil and the effort made to produce low emission diesel.
Many types of additives have been prepared and evaluated to raise the cetane number of diesel fuel. Such additives include peroxides, nitrates, nitrites, azo compounds and the like.
Alkyl nitrates such as amyl nitrate, hexyl nitrate and mixed octyl nitrates have been used commercially with good results. Other nitrates such as 2-methyl-2-nitropropyl nitrate (U.S. Pat. No. 4,536,190) have been suggested as cetane improvers but found shock sensitive. However, it is generally accepted that organic nitrates, more specifically the commercial 2-ethylhexyl nitrate, are the most cost-effective additives to improve cetane number of diesels. 2-ethylhexyl nitrate is available from the Associated Octel Company Limited under the brand name Cl-0801.
It is known that 2-ethylhexyl nitrate (2-EHN) has a de-stabilising effect on many diesel fuels when subjected to high temperature test conditions, such as ASTM D6468-99, Standard Test Method for High Temperature Stability of Distillate fuels. D6468 is a test that involves aging fuel for 90 or 180 minutes at a temperature of 150° C. This is a temperature above the auto-decomposition temperature of cetane improvers such as 2-EHN, and the decomposition products promote instability of diesel fuels.
Recent data by Bacha, et al. have demonstrated that high temperature stability as measured in D6468 is related to on-road performance of diesel trucks. Because of these findings, the National Council of Weights and Measures has chosen to specify test results developed from ASTM D6468 as a partial basis for defining “premium” diesel fuel in the United States. There is therefore a desire to overcome the problems of diesel destabilisation by cetane improvers, in particular by 2-EHN.
The prior art has provided some additives which are normally used to improve storage stability and will give some improvement in ASTM D6468. EP-A-0947577 teaches tertiary alkyl primary amines may stabilise diesel fuel containing cetane number improver.
The present invention alleviates the problems of the prior art
In a one aspect the present invention provides use of a thermal stabiliser for increasing the thermal stability of a cetane improver in a fuel composition comprising (i) a fuel, and (ii) the cetane improver, wherein the thermal stabiliser is a compound of the formula H—R
1
wherein H is a group comprising a heterocyclic group and R
1
is a hydrocarbyl group having from 10 to 200 carbons.
In a further aspect the present invention provides a fuel composition comprising (i) a fuel (ii) a cetane improver (iii) a thermal stabiliser, wherein the thermal stabiliser is a compound of the formula H—R
1
wherein H is a group comprising a heterocyclic group and R
1
is a hydrocarbyl group having from 10 to 200 carbon.
The present inventors have found that compounds such as those defined in the present claims, for example polyisobutenyl succinimide (PIBSI), are surprisingly effective in stabilising cetane improvers in diesel fuel. In particular the present compounds are effective in reducing the thermal degradation of cetane improvers such as 2-EHN.
The present inventors have found and have demonstrated in the attached examples that the present thermal stabilisers such as PIBSI effectively stabilise cetane improvers in diesel and in some aspects are provide improved stabilisation when compared to the stabilisers of the prior art, for example the stabilisers of EP-A-0947577.
Furthermore, in aspects of the invention, for example when PIBSI is used as a stabiliser, the thermal stabiliser has a further functionality—it is an effective detergent to improve injector cleanliness, for example in an L-10 Cummins diesel engine (a test is commonly used in the USA) and other diesel engine detergency tests.
FURTHER ASPECTS
In the present specification by the term “hydrocarbyl group” it is meant a group comprising at least C and H and may optionally comprise one or more other suitable substituents. Examples of such substituents may include halo-, alkoxy-, nitro-, a hydrocarbon group, an N-acyl group, a cyclic group etc. In addition to the possibility of the substituents being a cyclic group, a combination of substituents may form a cyclic group. If the hydrocarbyl group comprises more than one C then those carbons need not necessarily be linked to each other. For example, at least two of the carbons may be linked via a suitable element or group. Thus, the hydrocarbyl group may contain hetero atoms. Suitable hetero atoms will be apparent to those skilled in the art and include, for instance, sulphur, nitrogen and oxygen.
Thermal Stabiliser
R1 Group
Preferably R
1
is a branched or straight chain alkyl group. Preferably R
1
is a branched alkyl group.
R
1
may be a C
10
-C
200
hydrocarbon group. R
1
is preferably a C
30
-C
80
group and more preferably a polyisobutene (PIB).
Conventional PIBs and so-called “high-reactivity” PIBs (see for example EP-A-0 565 285) are suitable for use in the invention. High reactivity in this context is defined as a PIB wherein at least 50%, preferably 70% or more, of the terminal olefinic double bonds are of the vinylidene type, for example the GLISSOPAL compounds available from BASF.
Preferably R
1
has a molecular weight of from 200 to 2000, more preferably 260 to 1000, for example about 260, 320, 350, 550, 750, 780 or 1000, more preferably from 750 to 780.
Preferably R
1
is a PIB having a molecular weight of from 200 to 2000, more preferably 260 to 1000, for example about 260, 320, 350, 550, 750, 780 or 1000, more preferably from 750 to 780.
H—Heterocyclic Group
Preferably the heterocyclic group is a hydrocarbyl ring at least one member of which is selected from N, S and O. The ring portion of such a ring is referred to as a heterocyclic ring. Preferably at least one member of the hydrocarbyl ring is N.
Preferably the heterocyclic ring has from 4 to 10 members, more preferably from 4 to 6 members, yet more preferably 5 members.
Preferably the heterocyclic ring is substituted. Preferably the heterocyclic ring is substituted with one or more=O groups.
Pr

Affiliated with

Also associated with

Rating

Diesel fuel stabilizer does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Diesel fuel stabilizer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diesel fuel stabilizer will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3241433