DESCRIPTION

The present invention relates to a fuel composition for internal combustion engines, more particularly to a gasoline composition for internal combustion and controlled ignition engines, characterized by a C4 hydrocarbon content from 2.5% (w/w) to 8% (w/w) and a low vapour pressure, preferably from 0.5 to 0.7 bar, even more preferably lower than 0.6 bar.

Present gasolines, the green or unleaded gasoline (Super gasoline) and the so-called "Superplus" gasoline can get an Octane Number (RON) of at least 95 (usually of 95-98), and 98-102 respectively, said values being required by modern engines.

Another restriction regarding the gasoline compositions is related to the volatility (vapour pressure and some values of the distillation curve).

The most recent restriction concerns the necessity to set a limit to the so-called evaporation losses, causing introduction in the atmosphere of substantial amounts of volatile organic substances (VOCs). Moreover, VOC emission must be reduced in the working environment due to the fact that these volatile substances are easily inflammable and also explosive in particular situations. Obviously, said prescription concerns, in particular, gasolines distributed in the summer season and in warmer areas.

The Reid Vapour Pressure (RVP) is a measure of the gasoline volatility. It is defined as the absolute vapour pressure exerted by a liquid at 100°F (37.8°C). Method ASTM D323- 15A measures the vapour pressure at 37.8°C (100°F) of oil and oil-related products having an initial boiling point greater than 0°C (32°F). This test cannot be applied to liquefied oil gas or to oxygenated compounds different from MTBE. Method D4953 is the reference for determining the vapour pressure of mixtures gasoline - oxygenated compounds, said method being used in the presence of composition having a vapour pressure from 0.35 to 1.0 bar (from 5 to 15 psi). The norm EN 228:2012 describes the requirements of gasoline utilized in the European Union. According to this regulation, RVP is a characteristic that depends on the season and the climate of every country. Gasolines are classified in 10 classes (A, B, C, C1, D, D1, E, E1 , F, F1 ) in relation to the RVP value and, according to the climate characteristic, every country can select the gasoline class for winter and for summer,

Consequently, some European countries do not allow, particularly in the summer, to market gasolines having RVP greater than 0.6 bar (Class A) or than 0.7 bar (Class B). For these reasons, blending of different hydrocarbon fractions for preparing a final gasoline is very difficult, particularly in the summer, due to the restrictions about RVP; the more volatile fractions giving rise to a marked increase of the final gasoline RVP.

Moreover, it is known that fraction C4 is a composition mainly consisting of hydrocarbon C4, i.e. n-butane and iso-butane.

The C4 cut is not a valuable fraction, since it is very volatile and highly inflammable, by consequence its use in the gasoline formulation is not so easy. Recently some efforts were made in order to increase the C4 fraction value, by adding it to gasoline compositions. Although showing a significant value of RON, this C4 fraction is rich in butane; consequently its presence causes a significant increase of the vapour pressure of the final gasoline.

On the other hand, in order to meet the requirements of a high RON gasoline, the addition of relevant quantities of MTBE or similar oxygenated compounds, all of them having a relatively high RVP, is necessary.

According to the above, people skilled in the art like to prepare an unleaded and devoid or organometal compounds gasoline composition characterised by an appreciable quantity of C4, a low RVP and a high RON.

The gasoline composition of the present invention is able to meet all these requirements. The present invention relates to the use of N-alkyl substituted aromatic amines to prepare a gasoline composition devoid of organometal compounds useful as fuel for internal combustion and controlled ignition engines, characterized in that said gasoline composition has a low vapour pressure, measured as RVP, preferably from 0.5 to 0.7 bar, more preferably lower than 0.6 bar, and a C4 fraction content from 2.5 to 8.0% by weight. The C4 fraction is a mixture of light hydrocarbons mainly comprising iso-butane and n- butane, a low quantity of propane and traces of other compounds. The C4 fraction is usually obtained during the oil processing. A typical example of C4 composition is reported in Table A.

TABLE A

Data reported in Table A were obtained by analysing some C4 samples from an Italian refinery referring to 2015, used for the preparation of gasoline compositions. The above Table A reports the maximum and the minimum values of each component during 2015. We note that the above C4 fractions have a density at 15°C in the range 2.20 to 2.80 kg/m ³ .

Later on, the term "gasoline composition useful as fuel for internal combustion and controlled ignition engines" will be replaced by the term "composition of the invention". In relation to the Octane Number, its meaning is well known to people skilled in the art. It is also known that the Octane Number can be determined either according to the "Research" method (RON) or to the "Motor" method (MON). In the present document the Octane Number will be always determined as RON, except in the case the opposite is clearly stated.

The "N-alkyl substituted aromatic amine" definition encompasses both aniline derivative and mono- or di- alkyl substituted aniline derivatives. In the preferred embodiment of the present invention the N-alkyl substituted aromatic amines are selected from the N-methyl aromatic amines, the preferred one being N-methyl aniline.

Said aromatic amines are comprised in the composition of the present invention in a quantity of 0.05% to 4% by weight, preferably of 0.1 to 3% by weight.

The composition of the present invention can be used as a "Super" gasoline having a RON equal or greater than 95 and lower than 98, or as a so-called "Superplus" gasoline having a RON from 98 to 102. Moreover the compositions of the present invention can be used as high octane fractions for blending with one or more fraction having a lower RON. The gasoline composition of the present invention can also comprise one or more oxygenated compounds. The term "oxygenated compounds" includes both alcohols and ethers. Usually alcohols have a number of carbon atoms from 1 to 4, let say methanol, ethanol, n-propanol, iso-propanol, primary or secondary or tertiary butanol, and mixtures thereof.

As the ethers, the ethers usually comprised in the gasoline formulation are preferably selected between MTBE (methyl tert-butyl ether), DIPE (di-isopropyl ether), TAME (methyl t-amyl ether), and mixtures thereof. The only product of this class commercially available is MTBE, usually added to increase the Octane Number. The MTBE content in the gasoline composition of the present invention is in the range 0 to 5% by weight. Preferably, the gasoline composition of the present invention comprises MTBE in the lowest possible quantity. In the most preferable embodiment, MTBE and any different oxygenated compounds are not present.

The N-substituted aromatic amines of the present invention allow to increase the Octane Number as MTBE, but without the drawbacks of MTBE. The aromatic amines of the present invention increase the Octane Number (RON) of the gasoline composition, but at the same time they reduce or maintain RVP, while the addition of oxygenated compounds, mainly MTBE, increases RVP of the gasoline composition. Consequently, the addition of aromatic amines of the present invention allows to use the C4 fraction for blending gasolines. On the contrary, the addition of oxygenated compounds, mainly MTBE, does not allow the C4 addition, unless huge quantities of MTBE (see experimental part) are used.

Moreover the suggested and preferred replacement of MTBE by the aromatic amines of the present invention, preferably by N-methyl aniline (NMA), has further advantages:

1. The NMA handling and storage in a refinery entail much less risks in comparison with whatever oxygenated compound, because NMA shows a negligible RVP at 20°C (0.13 mbar = about 0.002 psi) and a high Flash Point (about 100°C). This feature is very important in case the refinery is located in a very warm country.

2. NMA is much less water soluble in comparison with ethers and alcohols, mainly MTBE and ethanol, usually blended in the gasoline. Moreover, in order to obtain the same increasing in the Octane Number, a much less quantity of NMA in comparison with MTBE, usually about 15 time less, is necessary. These NMA features enable to have a negligible or no risk of pollution of the aquifer and the water at the bottom of the tanks.

3. The time necessary for NMA biodegradation is lower in comparison to MTBE and the pollution risks, in the event of liquid waste, are lower. MTBE biodegradation is very low and not so easy, since MTBE is a strong biocide. 4. Using MTBE instead of any oxygenated, both alcohol and ether, enables to reduce the fuel consumption. Obviously, the energy content of the present invention gasoline, preferably devoid of oxygenated compounds, is greater than any gasoline composition containing ethers or alcohols. Then, the covered distance being equal, C0 ₂ emissions are lower.

The present invention also relates to a process for preparing a gasoline composition devoid of organometal compounds having a RON from 95 to 102, a low vapour pressure RVP, preferably from 0.5 to 0.7 bar, more preferably lower than 0.6 bar, and a C4 hydrocarbon content from 2.5% to 8.0% (w/w), said process comprising the steps of:

a) preparing a base gasoline having a C4 hydrocarbon content lower than 2.5% (w/w) and RON equal or lower than 102;

b) adding to said base gasoline one or more N-alkyl substituted aromatic amines so increasing RON of the base gasoline and in the same time maintaining or reducing the vapour pressure of the base gasoline;

c) adding the C4 hydrocarbon composition to the formulation of the base gasoline obtained in step (b), so obtaining the final gasoline composition characterized by:

a C4 hydrocarbon content from 2.5% to 8.0 % (w/w);

a vapour pressure (RVP) low, preferably from 0.5 a 0.7 bar, even more preferably lower than 0.6 bar;

RON from 95 to 102.

In the preferred embodiment of the present invention, the N-alkyl substituted aromatic amines are selected from the group of N-methyl substituted aromatic amines, the preferred one being N-methyl aniline.

Usually the aromatic amines are present in a quantity of 0.05% w/w to 4% w/w, preferable of 0.1 % w/w to 3% w/w.

More details for preparing a gasoline of the present invention are reported in the claims of 12 to 14. The base gasoline disclosed in step (a) are usually obtained by blending different hydrocarbon fractions available in a refinery, in relation to the plant setup of the refinery.

Typical examples of said hydrocarbon fractions are:

Butane gas C4, mainly containing 4 carbon atom hydrocarbons:

Light gasoline from the first distillation (sometimes named "light naphtha");

Isomerate gasoline C5;

Isomerate gasoline C6;

Reformed gasoline (at different severity grade);

Gasoline from alkylation process;

Light gasoline from cracking process;

Gasoline from the first distillation (sometimes named "virgin naphtha" or "full range naphtha");

Natural gasoline (sometimes called "condensate"), let say room temperature liquid hydrocarbons, present in petroleum gas directly produced at the oil well;

HTG gasoline (Hydrotreated gasoline).

The following example are reported for a better comprehension of the present invention.

EXAMPLES

Example 1

Table 1 reports the features of four hydrocarbon fractions used for preparing different gasolines, available in a refinery placed in a very warm area, particularly in the summer. Table 1 reports the chemical composition, the distillation data, RON and RVP of every fraction.

RON measurements were carried out according to method ISO 5164 (ASTM D 2699) and RVP measurements according to ASTM D323-15A and D4953.

TABLE 1 RVP (bar) 0,1034 0,8998 0,1999 4,3600

Olefins 18,00% 35,00% 0,00% 0,00%

Aromatics 0,07% 0,07% 1 ,30% 0,00%

Saturates 81 ,93% 64,93% 98,70% 100,00%

Density (kg/I) 0,7659 0,6899 0,7133 0,574

S (ppm w) 680 60 0,3 0

Benzene (%vol) 1 0,16 0 0

Oxygen (%vol) 0 5 0 0

Dist. 10% (°C) 89 40 74,6

Dist. 50% (°C) 124 50 111

Dist. 90% (°C) 180 83 118,8

Dist. 100% (°C) 200 95 152 40,6

The fraction called HTG is not a valuable hydrocarbon fraction since its RON is low.

The fraction called EtOH is a valuable hydrocarbon fraction comprising oxygenated compounds since its RON is very high, but, as all the oxygenated compounds, it gives rise to a large increase of RVP of the final gasoline composition.

The Alkylated hydrocarbon fraction is a valuable fraction having a high RON value.

The C4 hydrocarbon fraction (mainly butane) shows a very high RON but, obviously, a RVP very high; it is the most tricky fraction, since in a warm season only very low quantities of C4 can be added in a final blending.

Table 2 reports chemical composition, RON and RVP of four gasolines (gasoline 1-4) obtained starting from the fractions of Table 1.

All the gasolines reported in Table 2 are comparative examples since they do not comprise NMA, an essential component of the present invention gasoline. Table 2

(comparative examples)

RON of the base formulation (Gasoline 1 ) is lower than the minimum value required to a Super gasoline (RON 95,0), but corresponds to the specifications of summer RVP (lower than 0,6 bar). In order to prepare a gasoline having a right RON (more than 95 for a Super gasoline), addition to the base formulation of a proper quantity of MTBE is required. By substitution of the fraction HTG (having a very low RON = 87) with MTBE (very high RON = 108), is possible to obtain compositions having higher RON.

In order to obtain compositions having RON greater than 95 (Gasoline 3 and 4), adding MTBE in a quantity of 7% to 14% is necessary, but these final compositions have a RVP greater than 0.6 bar; consequently these gasoline compositions cannot be put in the market during summer or in warm countries.

Table 3 reports the features of 4 gasoline compositions (Gasoline 5-8) according to the present invention, all of them comprising NMA. Table 3 (invention)

On the contrary, use of NMA (1%) allows to obtain very high RON (99) without any significant increase of RVP (Gasoline 5, RVP = 0.57), though in the presence of 3.02% C4 fraction.

In the presence of 2% NMA, is even possible to blend Super Plus gasoline (Gasoline 6, RON = 104) always in the presence of 3.02% C4.

Alternatively, a gasoline having RON = 95 can be in any case prepared by greatly decreasing the quantity of the fraction Alkylated (having a high RON) and increasing the presence of C4 in the final gasoline up to very significant values, particularly up to 6.40% (Gasoline 7) and 6.00% (Gasoline 8).

Example 3

Table 4 shows the features of 4 hydrocarbon fractions available in an Italian refinery to be used for blending gasolines. These fractions are:

Reformed: High RON, valuable fraction;

Isomerate: Low RON, components very volatile, tricky fraction;

LCN (Light cut naphtha): very low RON, not valuable fraction;

C4 (mainly butane): very high RVP, tricky fraction. Table 4

Table 5 discloses the features of 3 gasolines obtained by blending the fractions disclosed in Table 4. These gasoline formulations are outside the scope of the present invention, since they do not comprise NMA.

Table 5

(comparative examples)

Benzina 1 : RVP is lower than 0.6 and RON = 96, then Benzina 1 is a gasoline Super, not Super Plus. MTBE and NMA are not present and the C4 fraction is present only at 2.50%. Starting from Benzina 1 , the use of MTBE does not allow to formulate any Super Plus gasoline. Not even a 15% MTBE addition enables to get a RON above 100 (benzina 2 and benzina 3); moreover RVP increases until to overcome the value fixed for the summer season (Benzina 3).

Table 6 discloses 3 gasolines (benzina 4-6) prepared starting from the hydrocarbon fractions reported in Table 4, said gasolines being part of the present invention since they comprise 1% NMA. Table 6 (invention)

On the contrary, the use of NMA enables to overcome RON 100 without increasing RVP (Benzina 4); By using NMA is even possible to re-blend the gasoline increasing the C4 fraction up to a concentration of 3% (Benzina 5) or up to 3.3% (Benzina 6).

We point out that all the 3 gasolines (benzina 4-6) are devoid of MTBE; then they present all the advantages above described.