Fuels

The invention concerns a fuel comprising a mixture of (A) at least one alcohol with an average molecular weight of less than 160, and (B) at least one further organic compound which has a spontaneous ignition temperature of less than 450.degree. C. The further organic compound is PA1 (1) a compound which contains one or more oxygen atoms but no nitrogen atoms, with the proviso that, (1.1) the compound is not a dialkoxy compound of formula ##STR1## in which R.sub.1 and R.sub.2 indicate hydrogen or straight-chain or branched alkyl radicals with up to 4 C-atoms, and R.sub.3 and R.sub.4 are straight-chain or branched alkyl radicals with up to 4 C-atoms; or PA0 (2) a compound which contains one or more nitrate groups and one or more ether linkages, or PA0 (3) a nitrogen-containing organic compound selected from the group consisting of azo compounds, tetrazines, nitroso compounds, nitro compounds, nitrates, and hyponitrites, with the proviso that component (B) is not entirely a linear or branched-chain alkyl nitrate containing between 2 and 8 carbon atoms. There are the provisos that, when the alcohol is methanol, the component (B) is not PA0 (a) a polyether of the general formula R[O(A).sub.n H]m wherein R represents hydrogen or a residue of an organic compound, which is built up of hydrogen and carbon and optionally oxygen and which has from 1 to 12 hydrogen atoms, which can be reacted with ethylene oxide or propylene oxide; A represents independently of each other a group derived from ethylene oxide or propylene oxide; m is a number from 1-12, and n has such a value that the total number of units derived from ethylene oxide and/or propylene oxide is 4-400, and is not PA0 (b) a polyether soluble in methanol and which contains 4-400 oxyalkylene units, derived from ethylene oxide and/or propylene oxide, wherein said oxyalkylene units constitute at least 40 percent by weight of the polyether.

This invention relates to fuels, in particular fuels for compression 
ignition engines. 
The use of methanol as a fuel suffers from the drawback that we are not 
aware of it being able to be used on its own in conventional compression 
ignition engines, commonly know as diesel engines. On the other hand, it 
would be desirable to utilise methanol as a fuel since it can be obtained 
from coal, of which there are large resources in many Western countries, 
particularly in the Republic of South Africa. 
The use of ethanol as a fuel has recently become of great interest in view 
of the high cost of fuels from oil. 
In one aspect the present invention provides a fuel comprising a mixture of 
(A) at least one alcohol with an average molecular weight of less than 
160, and (B) at least one further organic compound or mixture of organic 
compounds which together have a spontaneous ignition temperature of less 
than 450.degree. C., said further organic compound or mixture being one or 
more of: 
(1) a compound which contains one or more oxygen atoms but no nitrogen 
atoms, with the proviso that: 
(1.1) the compound is not a dialkoxy compound of formula 
##STR2## 
in which R.sub.1 and R.sub.2 indicate hydrogen or straight-chain or 
branched alkyl radicals with up to 4 C-atoms, and R.sub.3 and R.sub.4 are 
straight-chain or branched alkyl radicals with up to 4 C-atoms; and with 
the proviso that: 
(1.2) when the alcohol is methanol, the component (B) is not 
(1.2.1) a polyether of the general formula 
EQU R[O(A).sub.n H]m 
wherein R represents hydrogen or a residue of an organic compound, which 
is built up of hydrogen and carbon and optionally oxygen and which has 
from 1 to 12 hydrogen atoms, which can be reacted with ethylene oxide or 
propylene oxide; A represents independently of each other a group derived 
from ethylene oxide or propylene oxide; m is a number from 1-12, and n has 
such a value that the total number of units derived from ethylene oxide 
and/or propylene oxide is 4-400, and is not 
(1.2.2) a polyether soluble in methanol and which contains 4-400 
oxyalkylene units derived from ethylene oxide and/or propylene oxide, 
wherein said oxyalkylene units constitute at least 40 percent by weight of 
the polyether, or 
(2) a compound which contains one or more nitrate groups and one or more 
ether linkages, (an ether linkage being an oxygen atom linking two carbon 
atoms), or 
(3) a nitrogen-containing organic compound selected from the group 
consisting of azo compounds, tetrazines, nitroso compounds, nitro 
compounds, nitrate compounds, and hyponitrites, with the proviso that 
component (B) is not entirely a linear or branched-chain alkyl nitrate 
containing between 2 and 8 carbon atoms. 
In a second aspect the invention also provides a method of running an 
engine, which comprises injecting and/or inducting into the engine both 
(A) at least one alcohol with a molecular weight of less than 160 and (B) 
at least one further organic compound or mixture of organic compounds 
which together have a spontaneous ignition temperature of less than 
450.degree. C., said further organic compound or mixture being one or more 
of: 
(1) a compound which contains one or more oxygen atoms but no nitrogen 
atoms, with the proviso that: 
(1.1) the compound is not a dialkoxy compound of formula 
##STR3## 
in which R.sub.1 and R.sub.2 indicate hydrogen or straight-chain or 
branched alkyl radicals with up to 4 C-atoms, and R.sub.3 and R.sub.4 are 
straight-chain or branched alkyl radicals with up to 4 C-atoms; and with 
the proviso that: 
(1.2) when the alcohol is methanol, the component (B) is not 
(1.2.1) a polyether of the general formula 
EQU R[O(A).sub.n H]m 
wherein R represents hydrogen or a residue of an organic compound, which 
is built up of hydrogen and carbon and optionally oxygen and which has 
from 1 to 12 hydrogen atoms, which can be reacted with ethylene oxide or 
propylene oxide; A represents independently of each other a group derived 
from ethylene oxide or propylene oxide; m is a number from 1-12, and n has 
such a value that the total number of units derived from ethylene oxide 
and/or propylene oxide is 4-400, and is not 
(1.2.2) a polyether soluble in methanol and which contains 4-400 
oxyalkylene units, derived from ethylene oxide and/or propylene oxide, 
wherein said oxyalkylene units constitute at least 40 percent by weight of 
the polyether, or 
(2) a compound which contains one or more nitrate groups and one or more 
ether linkages, or 
(3) a nitrogen-containing organic compound selected from the group 
consisting of azo compounds, tetrazines, nitroso compounds, nitro 
compounds, nitrate compounds, and hyponitrites, with the proviso that 
component (B) is not entirely a linear or branched-chain alkyl nitrate 
containing between 2 and 8 carbon atoms. 
The components of the fuel may be injected and/or inducted as a mixture or 
may be injected and/or inducted separately from separate containers. The 
engine conveniently can be a compression ignition engine. 
We have found that, when mixed with said alcohols, said further organic 
compounds up-rate the compression-ignition characteristics of said 
alcohols as compression ignition fuels. Thus these alcohols can be 
up-rated to form suitable fuels for naturally aspirated commercial 
compression ignition engines by addition of the further organic compounds, 
where the alcohols are, without the added organic compounds, either less 
suitable or unsuitable for use as such fuels. Alcohols up-rated in this 
way can thus act as fuels in naturally aspirated commercial 
compression-ignition engines without the need for additional energy inputs 
and/or aids such as heated air aspiration, turbocharging, spark-ignition, 
abnormally high compression ratios or other additional energy sources 
and/or aids, although such additional energy sources and/or aids may be 
used, if desired. The further organic compounds act, when added in 
increasing amounts to fuels according to the invention which are barely 
capable of use in naturally aspirated compression-ignition engines, to 
increase power output and to cause said engines to run more smoothly. 
We have found, in particular, that if the organic compound (B) contains 
both nitrate groups and ether linkages, these particular compounds are 
especially suitable as ignition improvers for the alcohol fuel. 
The alcohol or mixture of alcohols, forming component (A), conveniently has 
an average molecular weight of less than 90. Particularly preferred 
alcohols are methanol and ethanol. 
Component (B) is an organic compound or mixture of organic compounds having 
a spontaneous ignition temperature of less than 450.degree. C. The term 
`spontaneous ignition temperature` is understood to mean the lowest 
temperature at which the material will ignite on its own in air. The 
organic compounds providing component (B), and which can be mixed with the 
alcohol, are oxygen-containing organic compounds, and the above defined 
nitrogen-containing compounds, some of which contain both nitrogen and 
oxygen atoms. 
Examples of oxygen-containing compounds (1) which can be used as component 
(B) are other alcohols, ethers, peroxides, hydroperoxides, acyl compounds 
of the formula R--(CO)--R' (where R and R' are suitable organic residue 
but one of which may be hydrogen), cyclic ethers containing one or more 
oxygen atoms in the ring, and esters. An ether linkage is a linkage where 
an oxygen atom joins two carbon atoms. 
The ether linkages in the oxygen compounds (1) which can be used according 
to the invention as component (B) may be present in any of the following 
forms, in which R.sub.1 and R.sub.2 are alkyl groups each containing 1 to 
20 carbon atoms, each of R.sub.3, R.sub.4, R.sub.5 and R.sub.7 may be 
alkyl groups each containing 1 to 20 carbon atoms, or an organic radical 
containing further ether linkages, and optionally also other functional 
groups, such as hydroxyl, carbonyl (to include other carbonyl-containing 
groups such as carboxylic acid, ester, aldehyde or carbonate), azo, and 
nitro, in particular O-nitro (nitrate) and R.sub.6 is H, or any of the 
radicals represented by R.sub.3. 
The ethers may be 
(a) Simple ethers of formula R.sub.1 --O--R.sub.2, for example di-iso-amyl 
ether where R.sub.1 and R.sub.2 are --CH.sub.2 CH.sub.2 
CH(CH.sub.3).sub.2. 
(b) Alkoxy ethers of formula R.sub.3 --O--R.sub.1 for example 1,2-dibutoxy 
ethane, where R.sub.1 is --nC.sub.4 H.sub.9, and R.sub.3 is 
--(CH.sub.2).sub.2 --O--nC.sub.4 H.sub.9. 
(c) Ethers containing ether linkages between radicals containing further 
functional groups, of formula R.sub.3 --O--R.sub.4. For example: 
(i) diethylene glycol dimethyl ether, where R.sub.3 and R.sub.4 are 
--(CH.sub.2).sub.2 --O--CH.sub.3 ; 
(ii) diethylene glycol monobutyl ether, nC.sub.4 H.sub.9 OCH.sub.2 CH.sub.2 
OCH.sub.2 CH.sub.2 OH; 
(iii) 1,3 dibutoxy-2-propanol, 
##STR4## 
(iv) ethyl 2-butoxyethyl carbonte 
##STR5## 
(d) Ethers containing acetal and/or ketal groups, of formula 
##STR6## 
For example: (i) acetaldehyde dihexyl acetal where R.sub.3 and R.sub.4 
are --nC.sub.6 H.sub.13, R.sub.5 is --CH.sub.3 and R.sub.6 is --H. 
(ii) glyoxal tetrabutyl acetal, (nC.sub.4 H.sub.9 O).sub.2 
CH--CH(O--nC.sub.4 H.sub.9).sub.2. 
(iii) glyoxal tetra-(2-butoxyethyl)acetal (nC.sub.4 H.sub.9 OCH.sub.2 
CH.sub.2 O).sub.2 CH--CH(OCH.sub.2 CH.sub.1/2 O--nC.sub.4 H.sub.9).sub.2. 
(e) Ethers containing orthoester groups of formula 
##STR7## 
For example: (i) Triethyl orthoformate, where R.sub.3,R.sub.4 and R.sub.5 
are --C.sub.2 H.sub.5 and R.sub.6 is --H 
(ii) Tributyl orthoacetate, R.sub.3,R.sub.4 and R.sub.5 are --nC.sub.4 
H.sub.9 and R.sub.6 is --CH.sub.3. 
(f) Ethers containing orthocarbonate groups, of formula 
##STR8## 
For example: tetrabutyl orthocarbonate R.sub.3,R.sub.4,R.sub.5 and 
R.sub.7 are --nC.sub.4 H.sub.9. 
(g) Cyclic ethers, of formula 
##STR9## 
in which R.sub.8 may be a hydrocarbon chain containing two or more carbon 
atoms, or may be an organic radical containing other ether linkages and/or 
other functional groups as described for radicals R.sub.3 -R.sub.7 above. 
For example: 
(i) tetrahydrofuran, R.sub.8 is (CH.sub.2).sub.4 
(ii) Paraldehyde, R.sub.8 is 
##STR10## 
(iii) Furfural, R.sub.8 is 
##STR11## 
When the component (B) contains a nitrate group and an ether linkage, (i.e. 
a `compound 2` above), the ether linkages may be present for example in 
one or more of the following forms: 
(a) simple ether linkages e.g. 2-ethoxyethyl nitrate and 2'-butoxy-2-ethoxy 
ethyl nitrate 
(b) acetal or ketal groups e.g. 2,2-diethoxy ethyl nitrate 
(c) ortho ester groups 
(d) ortho carbonate groups 
(e) cyclic ethers e.g. 1,3-dioxane-5-nitrate. 
The nitrogen compounds (3) which can be used as component (B), are azo 
compounds and tetrazines (including those containing up to two organic 
residues substituted on each terminal nitrogen atom), as well as the 
following compounds containing both nitrogen and oxygen atoms, namely 
nitroso compounds (of Formula R.sub.9 --NO), nitro compounds (of Formula 
R.sub.9 --NO.sub.2), nitrate compounds (of Formula R.sub.9 --ONO.sub.2), 
and hyponitrites (of Formula R.sub.9 --ON.dbd.NO--R.sub.10). In these 
formulae the radicals R.sub.9 and R.sub.10 are organic radicals. 
The ratios of constituents (A) and (B) can vary widely, e.g. from about 
99,9999 to 0,1 parts of alcohol per 100 parts fuel mixture, the balance 
being the further organic compound, more conveniently 50 to 99% of the 
alcohol constituent generally is present. If desired, up to about 15% by 
weight of water may be added. 
Particular examples of compounds which can be mixed with methanol and/or 
ethanol are acetaldehyde, paraldehyde, tetrahydrofuran, nitromethane, 
propionaldehyde, 2-ethoxy ethyl nitrate, 2-butoxyethyl nitrate, 
2'-butoxy-2-ethoxy-ethyl nitrate, diethylene glycol dinitrate, triethylene 
glycol dinitrate and the dinitrate of polyethylene glycol of an average 
molecular weight of 400. 
When manufacturing a fuel, the fuel may be made by mixing the constituents 
together. If desired, a lubricant such as castor oil also may be added. 
Other organic, organometallic or inorganic materials may be added to the 
fuel, for example lubricants, stabilisers, corrosion inhibitors, ignition 
improvers, other fuels, fuel extenders and fuel additives. 
Fuel may be injected into the engine via the fuel injection system and/or 
inducted into the engine via the air inlet manifold. 
When running an engine on the fuel, the components may be injected and/or 
inducted as a mixture or may be injected and/or inducted separately from 
separate containers. If desired, injection may be effected by utilizing an 
initial small amount, followed subsequently by a larger amount. If 
desired, diesel fuel may be injected as a mixture with the fuel of the 
invention or separately therefrom.