Organic nitrates as ignition enhancers

Abstract

A diesel fuel composition comprising an organic nitrate is described. The organic nitrate may be a terpene nitrate. Methods of using an organic nitrate for achieving a desired cetane number, and uses of organic nitrates for the purpose of reducing the ignition delay of the fuel and/or for increasing its cetane number to a defined level are also described, as are methods of operating a compression ignition engine.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of priority of European Patent Application No. 11195433.5, filed on Dec. 22, 2011, the disclosure of which is incorporated by reference herein in its entirety.FIELD OF THE INVENTION[0002]Embodiments of the present invention relate to a method of improving diesel fuels, and in particular to the use of organic nitrates as additives in a diesel fuel composition to give improvements in fuel combustion and cetane number.BACKGROUND OF THE INVENTION[0003]This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of any prior art.[0004]The cetane number of a fuel com...

AI Technical Summary

Benefits of technology

[0014]Embodiments of the invention provide alternative organic nitrates which are effective as combustion improvers or cetane number improvers. Embodiments of the invention also provide alternative organic nitrates which have similar or lower volatility than known cetane number improvers, or which meet acceptable safety levels for use in commercial diesel fuels. In addition, embodiments of the invention provide alternative organic nitrates for use as ignition / combustion improvers and that are most cost-effective and / or more convenient to manufacture than known organic nitrate cetane number improvers. Also, embodiments of the invention provide alternative organic nitrates for use as cetane number enhancers that work well under harsh engine conditions (for example, some known cetane enhancers may undesirably over-advance combustion. Embodiments of the invention further provide cetane enhancers derived from renewable (or waste) feedstocks or by-products. Additionally, embodiments of the invention provide methods for producing organic nitrates useful as cetane number improvers by nitration of corresponding organic alcohols.

Problems solved by technology

However, 2-EHN is also a radical initiator, and can potentially have an adverse effect on the thermal stability of a fuel.

Poor thermal stability in turn results in an increase in the products of instability reactions, such as gums, lacquers and other insoluble species.

These products can block engine filters and foul fuel injectors and valves, and consequently can result in loss of engine efficiency or emissions control.

The organic nitrates described in the prior art as combustion improvers and / or cetane number improvers have a series of disadvantages, especially lack of thermal stability, excessively high volatility and insufficient efficacy.

However, it may be expected that by decreasing the volatility of a cetane enhancer, e.g. by using a molecule of higher molecular weight, its efficacy as a combustion improver and / or cetane number improver may then decline.

It can also be difficult to store in concentrated form as it tends to decompose, and so is prone to forming potentially explosive mixtures.

These disadvantages, taken together with the often significant cost of incorporating 2-EHN as an additive into a fuel composition, mean that it would be generally desirable to reduce or eliminate the need for 2-EHN and other known cetane number improvers in diesel fuel compositions, whilst at the same time maintaining acceptable combustion properties.

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