Fuel and related compositions – Liquid fuels – Heterocyclic carbon compound containing a hetero ring having...
Reexamination Certificate
1998-03-18
2004-05-11
Medley, Margaret B. (Department: 1714)
Fuel and related compositions
Liquid fuels
Heterocyclic carbon compound containing a hetero ring having...
Reexamination Certificate
active
06733550
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to fuel oil compositions, processes for their preparation, and their use in compression-ignition engines.
BACKGROUND OF INVENTION
As stated in WO 95 33805 (Exxon) environmental concerns have led to a need for fuels with reduced sulphur content, especially diesel fuel and kerosene. However, the refining processes that produce fuels with low sulphur contents also result in a product of lower viscosity and a lower content of other components in the fuel that contribute to its lubricity, for example, polycyclic aromatics and polar compounds. Furthermore, sulphur-containing compounds in general are regarded as providing anti-wear properties and a result of the reduction in their proportions, together with the reduction in proportions of other components providing lubricity, has been an increase in reported failures of fuel pumps in diesel engines using low-sulphur fuels, the failure being caused by wear in, for example, cam plates, rollers, spindles and drive shafts.
This problem may be expected to become worse in future because, in order to meet stricter requirements on exhaust emissions generally, high pressure fuel pumps, for example rotary and unit injector systems, are being introduced, these being expected to have more stringent lubricity requirements than present equipment, at the same time as lower sulphur levels in fuels become more widely required.
At present, a typical sulphur content in a diesel fuel is about 0.25% by weight (2500 ppmw). In Europe maximum sulphur levels have been reduced to 0.05% (500 ppmw), in Sweden grades of fuel with levels below 0.005% (50 ppmw) (Class
2
) and 0.001% (10 ppmw) (Class
1
) are already being introduced.
In the context of this specification low-sulphur fuels are those having a sulphur level below 0.05% by weight (500 ppmw)
Many additives have been described over the years for enhancing engine cleanliness, e.g. for reducing or removing deposits in the intake system (e.g. carburetors, intake manifold, inlet valves) or combustion chamber surfaces of spark-ignition engines, or for reducing or preventing injector nozzle fouling in compression-ignition engines
For example, UK Patent Specification No. 960,493. (California Research Corporation) published Jun. 10, 1964, describes the incorporation of metal-free detergents, in the form of polyolefin substituted succinimides of tetraethylene pentamine, in base fuels for internal combustion engines. The succinimides disclosed correspond to the general formula:
wherein R is derived from a polymer RH of an olefin containing from 2 to 5 carbon atoms, which polymer contains from 30 to 200 carbon atoms. The molecular weight of the radical R is said to range from 400 to 3000, more preferably, 900 to 1200 and is advantageously derived from a polymer of isobutene having a molecular weight of about 1000. The single example of the preparation of such a succinimide is based on polysibotuylene of molecular weight about 1000, and tests are described using the resulting succinimide in gasoline and in a high-sulphur diesel fuel (sulphur content of 0.5% w, i.e. 5,000 ppmw).
More recent publications, e.g. those dating from after expiry of UK Patent No. 960,493 and its equivalents, teach the use of somewhat different succinimides and other succinic acid derivatives in fuel compositions
Thus, EP-B-147 240 (Ethyl) describes a distillate fuel composition for indirect injection compression ignition engines containing in an amount sufficient to suppress and preferably to minimise coking in nozzles of indirect injection compression ignition engines operated on such fuel a combination of (a) organic nitrate ignition accelerator and (b) hydrocarbyl-substituted succinimide or succinamide, and optionally: (c) hydrocarbyl amine having from 3 to 60 carbons and from 1 to 10 nitrogens, or a combination of the hydrocarbyl amine (c) and (d) N,N′-disalicylidene-1,2-diaminopropane. The hydrocarbyl-substituted succinimide is preferably an olefin-polymer substituted succinimide wherein the olefin polymer substituent has an average molecular weight of 500-500,000, preferably being a polyisobutene substituent having an average molecular weight of 700-5,000. The succinimide portion is preferably derived from a polyalkyleneamine of formula H
2
N—(R—NH)
n
—H wherein R is a divalent aliphatic hydrocarbon having 2 to 4 carbon atoms and n is an integer from 1 to 10, including mixtures thereof, and the polyalkyleneamine is preferably a polyethyleneamine having 2 to 6 ethylene units. The most preferred succinimide-succinamide component is the commercial product “HITEC E-644” (trade mark), which is used in the examples and is described as being “made by reacting two moles of a polyisobutenyl succinic anhydride with one mole of a polyethylene amine mixture having an average composition corresponding to tetraethylene pentamine” (Page 7, lines 4 to 6). The base fuel used in the examples was a high-sulphur fuel (sulphur content of 0.41%w, i.e. 4,100 ppmw).
EP-A-482 253 (Ethyl) describes a fuel composition which comprises a liquid middle distillate hydrocarbonaceous fuel containing at least one fuel-soluble ashless dispersant in an amount of at least 50 ppm sufficient to cause a prompt reduction in emissions released upon combustion of said fuel composition. In the example, the ashless dispersant is described as “a polyisobutenyl succinimide of tetraethylene pentamine in which the number average molecular weight of the polyisobutenyl group is about 950, used as a 75% solution in high aromatic solvent” (Page 10, lines 11 to 13), and the base fuel was a high-sulphur fuel (sulphur content of 0.125%w (Page 10, line 27), i.e. 1,250 ppmw). The general description relating to succinimides of ethylene polyamines including tetraethylene pentamine simply states “these ethylene polyamines have a primary amine group at each end so can form mono-alkenylsuccinimides and bis-alkenylsuccinimides” (Page 3, lines 9 and 10). No distinction or preference is expressed as between mono- and bis-succinimides.
EP-A-613 938 (BP) describes hydrocarbon fuel compositions comprising a hydrocarbon fuel and a hydrocarbyl succinic diamide derived from a secondary amine. The hydrocarbon fuel “may suitably comprise a hydrocarbon fraction boiling in the gasoline range or a hydrocarbon fraction boiling in the diesel range” (Page 5 lines 10 and 11). There is no discussion of sulphur content. The engine tests in the examples are in an Open Kadett engine (clearly a spark-ignition engine) and as comparative examples there are used (1) a mono-succinimide derived from a polyisobutylene succinic anhydride of PIB Mn about, 1000 and tetraethylene pentamine and (2) a bis-succinimide derived from the same polyisobutylene succinic anhydride and triethylene tetramine. The mono-succinimide gave results which were significantly inferior to the bis-succinimide (deposits mg/valve of 229 compared with 40, valve rating of 8.0 compared with 9.70) (Page 9, Table 2).
EP-B-557 561 (Chevron) discloses fuel compositions comprising a major amount of hydrocarbons boiling in the gasoline or diesel range and an effective detergent amount of an additive composition comprising:
(a) a polyisobutenyl succinimide having the formula
wherein R is a polyisobutenyl group having a number average molecular weight in the range of 1200 to 1500, preferably 1200 to 1400, more preferably 1250 to 1350, and most preferably about 1300, and x is 1 or 2, and (b) a nonvolatile paraffinic or naphthenic carrier oil, or a mixture thereof. It is stated (Page 3, lines 8 to 12) that the invention therein “is based on the surprising discovery that the unique combination of a polyisobutenyl succinimide and a carrier oil, wherein the polyisobutenyl succinimide is derived from ethylenediamine or diethylenetriamine and the polyisobutenyl group has an average molecular weight of 1200 to 1500, provides unexpectedly superior deposit control performance when compared to prior art polyisobutenyl succinimides of lower molecular weight”. There is no discussion of sulphur content of the fuel.
Grundy Michael John
Pearson Michael
Medley Margaret B.
Shell Oil Company
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