Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-01-06
2003-03-18
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S618000, C568S606000, C044S447000, C044S448000, C514S723000
Reexamination Certificate
active
06534685
ABSTRACT:
The present invention relates to a new liquid mixture consisting of diesel gas oils and certain oxygenated compounds, dialkyl-polyformals, which has increased cetane numbers with respect to conventional diesel gas oils.
The present invention also relates to a process for the selective production of said dialkyl-polyformals starting from alcohols and/or dialkylformals and formaldehyde using liquid acid catalysts.
Gas oil represents the heaviest part of medium distillates (200-360° C.). Both straight-run distillates and analogous cuts coming from conversion processes are joined in this fraction.
The main criteria for defining a gas oil are the boiling-point range and density range (0.760-0.935 at 15° C.). The main engine characteristics which determine the quality of a diesel gas oil are the combustion characteristics simulated by the cetane number.
Future fuel specifications in Europe seem to be directed towards diesels with an ever increasing cetane number, at the same time reducing the content of sulfur and polyaromatic hydrocarbons.
Whereas there are various process alternatives for improving the quality of gasolines, as far as gas oil is concerned, which historically is a less developed product than gasoline, there seem to be only two main methods for obtaining a high quality product in the refinery: either one has a good quality crude oil and therefore the gas oil obtained by distillation is also high quality (it only needs a relatively bland hydro-treatment) or it is necessary to resort to forced hydro-treatment and hydrocracking processes on the various fractions.
A third solution is to synthesize, or obtain from other sources, synthetic fuels or fuels of a natural origin which can form high quality components for reformulated gas oils: examples of the first category are Fischer-Tropsch gas oils and an example of the second category is “bio-diesel” deriving from seed oils.
Another group of particularly interesting compounds consists of linear ethers, with a total number of atoms≧9, which have a blending cetane number that is more than double the specific value of present gas oils and which have extremely interesting cold properties (Pecci, G. C., Clerici, M. G., Giavazzi F., Ancillotti, F., Marchionna, M., Patrini, R., IX Int. Symp. Alcohols Fuels, (1991), 1, 321; Giavazzi F., Terna, D., Patrini, R., Ancillotti, F., Pecci, G. C., Trerè, R., Benelli, M., IX Int. Symp. Alcohols Fuels, (1991) 1, 327).
On adding these ethers to a gas oil, all the properties of the latter are improved; not only is the cetane number considerably increased, but the cold properties are also improved, and in addition the content of aromatics and sulfur as well as the density are reduced as a result of the dilution (Marchionna, M., Patrini, R., Giavazzi, F., Pecci, G. C., Preprints 212
th
Nat. Meet. Am. Chem. Soc., Div. Petr. Chem, (1996), 41, 585).
From the point of view of environmental characteristics, these ethers have a positive effect on the reduction of emissions; in particular, the high cetane number allows a reduction in the emissions of hydrocarbons and CO, whereas the presence of oxygen in the molecule, accounts for a considerable reduction mainly in particulate emissions but also in those of NO
x
.
Other activities of interest have been effected outside our research group. ARCO has carried out studies on the synergic effect of glycol ethers and alkyl peroxides as additives of gas oils. The results of ARCO research (Liotta, F. J., Jr. and Montalvo, D. M., SAE, Tech. Paper 932734, (1993); Nandi, M. K., Jacobs, D. C., Liotta, F. J., Jr. and Kesling, H. S., Jr., SAE, Tech. Paper 942019, (1994) on the use of glycol derivatives (at 5% in gas oil) are briefly summarized hereunder:
the addition of oxygen (as ether) causes a reduction in the particulate, but does not change its composition.
the NO
x
compounds do not decrease but rather increase slightly; if a cetane raiser of the peroxide type is added, however, also the NO
x
compounds decrease.
a fuel containing 31% of aromatics with the addition of oxygenated compounds and peroxides in the above proportion fully satisfies emission specifications in California and corresponds to a fuel containing only 15% of aromatics without oxygenated products.
Recently, moreover, it seems that ARCO Lyondell itself is ready to sell a reformulated gas oil to the Californian market (“EC Ultra Clean Diesel”) which is very advanced for its properties (natural cetane number: 60; sulfur<15 ppm; aromatics<10% vol.). The composition of this gas oil is not known.
Various scientific papers have also recently appeared on the emissions of diesel engines which included glycol ethers, ethers and other oxygenated compounds (methylal) in the formulations of gas oils. In the last few years there has been a growing interest in gas oil components on the part of numerous petroleum companies and institutions.
A liquid mixture essentially consisting of gas oil and oxygenated components, has now been surprisingly found, which allows both the cetane number and oxygen percentage of gas oil to be increased.
The liquid mixture of the present invention, having a cetane number higher than 40, is characterized in that it consists of:
a typical diesel gas oil cut having a boiling point ranging from 150 to 380° C., preferably from 200 to 350° C., and a density ranging from 0.76 and 0.935 g/ml at 15° C.;
one or more compounds selected from dialkyl-polyformals represented by the formula
RO(CH
2
O)
m
R,
wherein R is a C
n
H
2n+1
alkyl chain,
m is an integer equal to or greater than 2 and less than or equal to 6,
n is an integer ranging from 1 to 10,
wherein the concentration of these dialkyl-polyformals in the gas oil ranges from 1 to 20%, preferably from 4 to 11% by volume.
More specifically, m is preferably equal to or greater than 3 and n is preferably equal to 1 or 2, more preferably m is equal to or greater than 3 and less than or equal to 5 and n is equal to 1.
Table A below indicates the blending cetane number data relating to this group of products determined by the addition of these components to a basic gas oil with a cetane number of 48.
These components are extremely interesting because, in addition to having a high cetane number and a high oxygen content (approx. 42-49%), which favours the reduction of the particulate, they originate from an inexpensive and widely available raw material.
TABLE A
Compound
b.p. (° C.)
Blending cetane Nr.
CH
3
O(CH
2
O)
2
CH
3
105
63
CH
3
O(CH
2
O)
3
CH
3
156
78
CH
3
O(CH
2
O)
4
CH
3
202
90
CH
3
O(CH
2
O)
5
CH
3
242
100
CH
3
CH
2
O(CH
2
O)
2
CH
2
CH
3
140
77
CH
3
CH
2
O(CH
2
O)
3
CH
2
CH
3
185
89
Cetane raisers can be added to the typical diesel gas oil cut, used in the mixture of the invention, preferably in a concentration in the diesel gas oil of up to 1% by weight.
These cetane raisers can be selected from nitro-derivatives and dialkyl-peroxides.
The present invention also relates to a process for the selective production of dialkyl-polyformals starting from alcohols and/or dialkylformals and formaldehyde by the use of liquid acid catalysts; the process is characterized by both high yields and the particular recovery method of the catalyst from the product and its recycling.
The synthesis methods of dialkyl-polyformals RO(CH
2
O)
m
R are the following:
2ROH+mCH
2
O→RO(CH
2
O)
m
R+H
2
O (1)
RO(CH
2
O)R+(m−1)CH
2
O→RO(CH
2
O)
m
R (2)
Both reactions take place with acid catalysis.
It is known that poly-oxymethylene-dimethylethers can be prepared starting from methanol and paraformaldehyde at high temperatures (Helv. Chim. Acta 8, 64 (1925), Ann. 474, 213, (1929); in the Dupont patent U.S. Pat. No. 2,449,469, the polyformals are prepared starting from paraformaldehyde and dialkylformal with sulfuric acid as catalyst (acid concentrations of about 0.1-2% by weight).
A process has now been surprisingly found which, operating also with very low concentrations of sulfonic acids, optionally substituted with halogens, as catalysts, allows high yields to polyformals to be obtained
Marchionna Mario
Patrini Renata
Barts Samuel
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Price Elvis O.
Snamprogetti S.p.A.
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