Fuel and related compositions – Liquid fuels – Containing organic -c
Patent
1992-10-13
1995-12-26
Medley, Margaret
Fuel and related compositions
Liquid fuels
Containing organic -c
44390, 44395, C10L 118, C10L 120
Patent
active
054783682
DESCRIPTION:
BRIEF SUMMARY
This invention relates to novel polymers useful as flow improvers for fuel oils and to oil and fuel oil compositions to which a flow improver has been added.
When oils and fuel oils are subjected to low ambient temperatures wax will separate out and impair the flow properties unless a Cold Flow Improver is added. The nature of the wax depends upon the type of fuel and this invention is particularly concerned with additives to treat Distillate Fuels which precipitate normal alkane waxes which in the absence of additives form large plates which will block fuel lines and filters.
The invention relates to wax containing Distillate Fuels treated with additives whose size and structural configuration are particularly suited to the crystallography of the wax crystals which form in the Distillate Fuel as it cools, so that the additives interact with these waxes during crystallisation to produce precipitated wax of reduced crystal size.
Mineral oils containing paraffin wax have the characteristic of becoming less fluid as the temperature of the oil decreases. This loss of fluidity is due to the crystallisation of the wax into plate-like crystals which eventually form a spongy mass entrapping the oil therein. The temperature at which the wax crystals begin to form is known as the Cloud Point and the temperature at which the wax prevents the oil from pouring as the Pour Point. Between these temperatures the wax crystals can however block filters and pipes rendering systems such as diesel trucks and domestic heating systems inoperable. The effectiveness of additives to improve the operability at low temperatures can be evaluated by tests such as the CFPP and PCT and their ability to depress the Cloud Point and Wax Appearance Point can also be ascertained.
It has long been known that various additives act as wax crystal modifiers when blended with waxy mineral oils. These compositions modify the size and shape of wax crystals and reduce the cohesive forces between the crystals and between the wax and the oil in such a manner as to permit the oil to remain fluid at lower temperature and in some instances to have improved filterability at temperatures between the cloud point and the pour point.
Various Pour Point depressants have been described in the literature and several of these are in commercial use. For example, U.S. Pat. No. 3,048,479 teaches the use of copolymers of ethylene and C.sub.1 -C.sub.5 vinyl esters, e.g. vinyl acetate, as pour depressants for fuels, specifically heating oils, diesel and jet fuels. Hydrocarbon polymeric pour depressants based on ethylene and higher alpha-olefins, e.g. propylene, are also known.
U.S. Pat. No. 3,961,916 teaches the use of a mixture of copolymers, to control the size of the wax crystals and United Kingdom Patent 1,263,152 suggests that the size of the wax crystals may be controlled by using a copolymer having a low degree of side chain branching. Both systems improve the ability of the fuel to pass through filters as determined by the Cold Filter Plugging Point (CFPP) test since instead of plate like crystals formed without the presence of additives the needle shaped wax crystals produced will not block the pores of the filter rather forming a porous cake on the filter allowing passage of the remaining fluid.
Other additives have also been proposed for example, United Kingdom Patent 1,469,016, suggests that the copolymers of di-n-alkyl fumarates and vinyl acetate which have previously been used as pour depressants for lubricating oils may be used as co-additives with ethylene/vinyl acetate copolymers in the treatment of Distillate Fuels with high final boiling points to improve their low temperature flow properties.
U.S. Pat. No. 3,252,771 relates to the use of polymers of C.sub.16 to C.sub.18 alpha-olefins obtained by polymerising olefin mixtures that predominate in normal C.sub.16 to C.sub.18 alpha-olefins with aluminium trichloride/alkyl halide catalysts as pour depressants in Distillate Fuels of the broad boiling types available in the United States in the early 1960's.
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JP56050995 Abstract.
Journal of the Institute of Petroleum "New Laboratory Test for Predicting Low-temperature Operability of Diesel Fuels" T. Coley, L. F. Rutishauser, and H. M. Ashton Jun. 1966, vol. 52, Issue 510, pp. 173-185.
Bland Jacqueline D.
Lewtas Kenneth
Exxon Chemical Patents Inc.
Mahon John J.
Medley Margaret
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