Fuel and related compositions – Liquid fuels – Organic nitrogen compound containing
Reexamination Certificate
2001-08-20
2003-12-02
Toomer, Cephia D. (Department: 1714)
Fuel and related compositions
Liquid fuels
Organic nitrogen compound containing
C044S333000, C044S340000, C044S347000, C044S349000, C044S350000, C044S329000
Reexamination Certificate
active
06656237
ABSTRACT:
This invention relates to fuel compositions of low sulphur content which contain at least one component capable of enhancing the lubricity of such low sulphur fuels.
Fuels such as diesel are widely used in automotive transport due to their low cost. However, one of the problems with such fuels is the presence of relatively high concentrations of sulphur containing compounds. Excessive sulphur contributes to exhaust particulate emissions and can also degrade the effectiveness of some exhaust after-treatment technology which is being introduced in response to regulated limits on exhaust emissions. As a result, the permitted level of sulphur in diesel fuel has been progressively reduced over the years and further reductions are planned for the future. Whilst reduction in sulphur content can be readily achieved by well known processes such as eg hydrodesulphurisation which is generally carried out in the presence of a catalyst, such process also adversely affects the lubricity of the resultant desulphurised product. Consequently, it is necessary to formulate compositions which are low in sulphur content but are also of the desired lubricity in order to minimise wear and friction and thus protect against damage to the injection system of a diesel engine. It has hitherto been the practice to add anti-wear agents to such formulations including fatty acid esters, lactones, polyoxyalkylene ethers, amino compounds and the like for this purpose. However, compositions containing compounds such as esters are expensive in terms of both material and storage costs. An article by D. Wei et al in Lubrication Science, 1989, 2(1), pp 63-67 entitled “The Influence of Chemical Structure of Certain Nitrogen-Containing Organic Compounds on Their Antiwear Effectiveness: The Critical Role of Hydroxy Group” discloses that some heterocyclic nitrogen compounds have a beneficial effect on the antiwear performance of base stocks. This author goes on to state that hydroxy groups involved in some nitrogen-containing compounds have been found to improve their antiwear performance significantly and states that hydroxy substituted benzothiazoles are most effective in wear reduction and anti-scuffing. With this in view the author reports the results of the tests carried out on films formed on rubbing surfaces by the benzo-derivatives of pyridine and thiazole, with or without hydroxy groups on the rings. The article concludes that protective films formed on rubbing surfaces by the above heterocyclic compounds bearing a hydroxy group are significantly different from those produced by the analogous compounds without a hydroxyl group.
Recently published EP-A-0885947 discloses the use of various additives to fuel oil compositions which contain no more than 0.05 wt % of sulphur and having a T
95
of <350° C., the additives being (a) an ashless dispersant comprising an acylated nitrogen compound and (b) a monocarboxylic acid having from 2-50 carbon atoms. There is no mention of fused polycyclic amines or of any fuel containing <50ppm of sulphur. Again, prior published WO 98/16601 claims a fuel oil composition obtainable by the addition of a minor proportion of a compound comprising one or more aromatic ring systems wherein at least one of the ring systems bears as substituents (i) one or more hydrocarbon groups imparting oil solubility to the compound, (ii) one or more hydroxyl groups or derivatives thereof or both, and (iii) one or more amine salt groups. The sulphur concentration of the fuel oil is said to be ≦0.02 wt %. None of the amine salts described, however, are attached directly to a ring carbon atom and no fused polycyclic aromatic amines are disclosed.
The use of compounds such as benzothiazoles will add to the sulphur content of such fuels and consequently derogate from the objective of achieving low Sulphur fuels. Moreover, it has also been found that it is not necessary for the antiwear additive to be a heterocyclic compound. The desired objective can be achieved equally well by using antiwear additives based on polycyclic compounds containing exocyclic nitrogen groups.
The present invention therefore provides a fuel composition having a sulphur content of not more than 50 ppm by weight and comprising at least 50 ppm based on the total weight of the fuel composition of at least one fused polycyclic aromatic compound which comprises at least one exocyclic group containing nitrogen wherein the nitrogen is attached directly to a ring carbon atom.
The sulphur content of the fuel composition is preferably less than 50 ppm by weight and more preferably less than 40 ppm by weight. Such low sulphur levels can be achieved in a number of ways. For instance, this may be achieved by well known methods such as eg, catalytic hydrodesulphurisation. Typically, the present invention is applicable to a broad range of petroleum fuels from light boiling gasoline (boiling range from 120-140° C.). The most common distillate fuels are kerosene, jet fuels, diesel fuels and heating oils. The lubricity properties of ultra-low sulphur (50 ppm or less) base fuels with a T
95
of suitably 370° C., preferably 360° C., particularly benefit from the presence of the nitrogen compounds referred to above. Especially, the lubricity properties are more of an issue with diesel fuels because diesel fuel injection pumps are more sensitive to wear problems. The base fuels may comprise mixtures of saturated, olefinic and aromatic hydrocarbons and these can be derived from straight run streams, thermally or catalytically cracked hydrocarbon feedstocks, hydrocracked petroleum fractions, catalytically reformed hydrocarbons, or synthetically produced hydrocarbon mixtures. The present invention is particularly applicable to diesel fuels that have recently been introduced into the UK market and are generally referred to as ultra-low sulphur automotive diesel oils (hereafter “ULSADO” and is sampled eg from Esso's Fawley Refinery).
The fused polycyclic aromatic compound which has at least one exocyclic group containing nitrogen wherein the nitrogen is attached directly to a ring carbon atom is capable of acting as an antiwear and lubricity enhancing additive for low sulphur fuels according to the invention. The expression “fused polycyclic aromatic compound” as used herein and throughout the specification is meant that said compound comprises an aromatic moiety which has at least two fused rings of which at least one is an aromatic ring, which aromatic ring may in turn be a heterocyclic ring, whether or not the remaining ring(s) in the fused polycyclic structure are aromatic or carry other hydrocarbyl or functional groups such as alkyl, hydroxyl or ketonic or ester groups. One such example where a cycloaliphatic ring is fused with an aromatic/heterocyclic ring is 1-amino indan and another example is an amino anthraquinone.
The exocyclic amino group may also be attached directly to a carbon atom of a ring which is itself attached to but is not part of the fused polycyclic ring structure.
Where the fused polycyclic aromatic compound contains a heterocyclic ring, the heteroatom may be nitrogen or oxygen.
The exocyclic group containing nitrogen may be a primary or a secondary amino group and may carry hydrogen and/or hydrocarbyl groups, such hydrocarbyl groups being aliphatic, cycloaliphatic or aromatic in nature and is preferably a primary amino group. In this context, it is worth noting that compounds having two exocyclic nitrogen groups are preferable to compounds which have only one exocyclic nitrogen group. Furthermore, where such compounds have more than one exocyclic nitrogen group, especially primary amino groups, it is even more preferable that these groups are in close proximity and in non-hindered position on the fused polycyclic compound. Thus, it is preferable that the exocyclic nitrogen groups are attached to adjacent carbon atoms, such as eg the 1,2-, 2,3-, 3,4-carbon atoms, or, the 1,8-positions of a binuclear structure of eg the diamino naphthalene type, or, eg the 1,7-positions a diamino indan type. As will be apparent, in th
Barbour Robert Howie
Rickeard David John
Schilowitz Alan Mark
ExxonMobil Research and Engineering Company
Purwin Paul E.
Toomer Cephia D.
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