WO2011073779A1

WO2011073779A1 - Gas oil composition comprising biodiesel and diethyl carbonate from bioethanol

Info

Publication number: WO2011073779A1
Application number: PCT/IB2010/003271
Authority: WO
Inventors: Marcello Notari; Elena Maria Rebesco; Maria Cristina Savarese
Original assignee: Eni S.P.A.
Priority date: 2009-12-18
Filing date: 2010-12-13
Publication date: 2011-06-23
Also published as: ITMI20092235A1; IT1396959B1

Abstract

Gas oil composition comprising: - from 65% by volume to 92.5% by volume, preferably from 83% by volume to 89% by volume, with respect to the total volume of said composition, of at least one gas oil; - from 0.5% by volume to 20% by volume, preferably from 1% by volume to 10% by volume, with respect to the total volume of said composition, of at least one diethyl carbonate, said diethyl carbonate being obtained from bioethanol; - from 0.5% by volume to 15% by volume, preferably from 3% by volume to 7% by volume, with respect to the total volume of said composition, of at least one biodiesel; on the condition that the total amount of said diethyl carbonate and of said biodiesel is higher than or equal to 7.5% by volume with respect to the total volume of said composition. Said composition can be advantageously used as fuel for diesel engines.

Description

GAS OIL COMPOSITION COMPRISING BIODIESEL AND DIETHYL CARBONATE FROM BIOETHANOL

The present invention relates to a gas oil composition comprising diethyl carbonate and biodiesel.

More specifically, the present invention relates to a gas oil composition comprising diethyl carbonate obtained from bioethanol and biodiesel.

The above composition can be advantageously used as fuel for diesel engines.

It is known that the emissions produced by the combustion of fuels of a fossil origin containing carbon dioxide (C0₂) , carbon monoxide (CO) , nitrogen oxides (NO_x) , sulfur oxides (SO_x) , volatile organic compounds and particulate matter (PM) , are not only harmful, but are also the main cause of environmental problems such as, for example, the greenhouse effect (in the case of nitrogen and carbon oxides) and acid rains (in the case of sulfur and nitrogen oxides) .

In recent years, the increase in the cost of crude oil and a maturing awareness with respect to the environmental problems described above, have increased the necessity for finding alternative, biodegradable and renewable energy sources .

Consequently, the progressive substitution of fuels deriving from fossil energy sources such as, for example, coal, petroleum, natural gas, with fuels deriving from alternative, biodegradable and renewable energy sources such as, for example, vegetable oils, animal fats, biomasses, algae, is becoming of increasing interest on a worldwide scale.

Efforts have therefore been made in the art to obtain fuels from renewable energy sources.

With respect to fuels for diesel engines, for example, the use is known of biodiesel and hydrotreated vegetable oils (HVO) as such, or in a blend with gas oil, and also of blends of gas oil comprising bioethanol .

Biodiesel generally comprises a blend of fatty acid alkyl esters, in particular a blend of fatty acid methyl esters (FAME) and can be produced starting from raw materials of a natural origin containing triglycerides (generally triesters of glycerine with fatty acids having a long alkyl chain) such as, for example, crude vegetable oils obtained by squeezing the seeds of oleaginous plants such as, for example, rape, palm, soya, sunflower, mustard, and also from other triglyceride sources such as, for example, algae, animal fats, or used or waste vegetable oils. Said raw materials as such, or the triglycerides obtained after subjecting said raw materials to separation, are subjected to a transesterification process in the presence of an alcohol, in particular methanol, and of a catalyst, in order to obtain said fatty acid alkyl esters, in particular said fatty acid methyl esters (FAME) .

At present, however, as provided for by the standard EN 590:2009, said biodiesel can be used in blends with gas oil in amounts lower than or equal to 7% by volume with respect to the total volume of said blends. Only a few motorizations, specifically modified, can be capable of using blends of gas oil comprising amounts of biodiesel higher than 7% by volume with respect to the total volume of said blends or even of using biodiesel as such, as fuel.

The main problems which limit the use of gas oil blends comprising amounts of biodiesel higher than 7% by volume with respect to the total volume of said blends as fuel for diesel engines, are:

- compatibility with the materials used in the feed pipes of gas oil vehicles, above all for vehicles registered before the use of biodiesel in a blend with gas oil,

- compatibility with the exhaust gas post-treatment systems ;

- compatibility with the injection systems;

- greater dilution of the engine lubricant.

Hydrotreated vegetable oils (HVO) , also known as green diesel, are produced by the hydrogenation/deoxygenation of a material deriving from renewable sources comprising triglycerides and free fatty acids, in the presence of hydrogen and of a catalyst as described, for example, by Holmgren J. et al . in the article "New developments in renewable fuels offer more choices", published in "Hydrocarbon Processing", September 2007, pages 67-71. This article indicates the best characteristics of said hydrotreated vegetable oils (HVO) with respect to biodiesel, in particular with respect to the blend of fatty acid methyl esters (FAME) . In particular, the best oxidative stability and the best improved cold properties of said hydrotreated vegetable oils (HVO) , are indicated. Furthermore, said hydrotreated vegetable oils (HVO) do not have the problem of the higher emissions of nitrogen oxides (NO_x) .

Due to the lack of oxygen atoms in said hydrotreated vegetable oils (HVO) , however, their use in diesel engines mixed with gas oil in an amount lower than 5% by volume with respect to the total volume of said blend, does not provide significant benefits with respect to particulate matter emissions (PM) . There is a tendency, however, towards a reduction in the particulate matter emissions (PM) when said hydrotreated vegetable oils (HVO) are used in diesel engines mixed with gas oil in an amount equal to or higher than 20% by volume with respect to the total volume of said blend, as described, for example, by L. Rantanen et al. in the article "NExBTL - Biodiesel Fuel of the Second Generation" , published in SAE Report 2005-01-3771.

Whereas in the United States private transportation greatly privileges the market of gasoline vehicles, in Europe the situation is the opposite. The use of gas oil vehicles is expanding and the oil product market therefore has an excess production of gasoline with its relative exportation, whereas a consistent importation is necessary for gas oil. This situation also has important consequences in activities for the development of biofuels. In Europe, there is in fact a certain interest in the development of biocomponents for gas oil which overcome the drawbacks connected to the use of biodiesel and hydrotreated vegetable oils (HVO) described above and which preferably derive from biodegradable and renewable energy sources, in particular from the fermentation of vegetable substances (e.g., agricultural crops comprising sugar cane, corn, etc.), such as, for example, bioethanol, other bioalcohols or their derivatives.

The use of said biocomponents, traditionally used in blends with gasoline, in blends with gas oil, would make the use of said biodegradable and renewable energy sources more effective and the rebalance of the disequilibrium of the European production between gas oil and gasoline.

As mentioned above, blends of bioethanol with gas oil, normally known as "e-diesel", are also known in the art. These bioethanol/gas oil blends, however, can have various problems such as, for example, non- homogeneity, low cetane number, low flash point.

One of the main problems, i.e. non-homogeneity, is linked to the fact that as bioethanol is immiscible with gas oil within a wide temperature range, there is a phase separation and the blends obtained are therefore unstable, as described for example by Lapuerta et al . in the article "Stability of diesel- bioethanol blends for use in diesel engines" , published in "Fuel" (2007), Vol. 86, pages 1351-1357. In this article, the conditions in which said blends are stable, are studied. The stability of these blends is mainly influenced by three factors: the temperature, the water content and the initial ethanol content. The results obtained show that the presence of water in the blends, the low temperatures and the high content of ethanol favour phase separation, whereas the presence of additives such as, for example, surfactants and/or co-solvents, have the opposite effect.

As indicated above, a further problem linked to the use of bioethanol mixed with gas oil is the low cetane number of said bioethanol/gas oil blends, which causes a high ignition delay in internal compression diesel engines. A way of solving this problem is described, for example, in European patent application EP 1, 721, 954.

European patent application EP 1,721,954 describes a diesel fuel composition comprising: a diesel fuel as base material; ethanol in an amount ranging from 5% by weight to 30% by weight with respect to the total amount of said diesel; ethyl nitrite or, alternatively, ethyl nitrate in an amount ranging from 0.5% by weight to 7% by weight with respect to the total amount of said diesel. Said ethanol is preferably obtained from vegetable material, for example from the fermentation of vegetable substances such as agricultural crops comprising sugar cane and corn. Thanks to the presence of ethyl nitrite or ethyl nitrate, the above diesel composition is said to have an excellent ignitability in spite of the presence of ethanol. Said patent application does not provide data relating to the flash point of the above diesel composition.

It is also known in the art that the use of diethyl carbonate mixed with gas oil, leads to a consistent reduction in particulate matter emissions.

Miloslaw et al . , for example, in the article "The influence of synthetic oxygenates on Euro 4 diesel passenger car exhaust emissions" published in SAE Report 2008-01-2387, indicate, among other things, the results of an experimentation carried out on a Euro 4 motor vehicle according to the NEDC cycle and according to the FTP-75 cycle with the use of a gas oil containing 5% by volume of diethyl carbonate with respect to the total volume of the gas oil/diethyl carbonate blend, which corresponds to an oxygen content in the blend equal to about 2.4% by weight. In the case of the NEDC cycle, a reduction in the particulate matter emissions of 32% is indicated, coupled with an increase in the emissions of nitrogen oxides (NO_x) of only 4%, without significantly influencing the fuel consumptions (increase of 0.5%). In the case of the FTP-75 cycle, on the other hand, a reduction in the particulate matter emissions of 19% is indicated, with an increase in the emissions of nitrogen oxides (NO_x) of 13% and an increase in the consumptions of 2.6%.

In the article "Combustion and emissions of a DI diesel engine fuelled with diesel-oxygenate blends", published in "Fuel" (2008), Vol. 87, pages 2691-2697, Ren et al . indicate the results of a bench experimentation carried out on a direct injection diesel engine, with an engine displacement equal to 903 cm³, at 2000 rpm, with the use of a gas oil containing different oxygenated compounds in variable percentages. For the gas oil-diethyl carbonate blends and gas oil- dimethyl carbonate blends, the reduction in the particulate matter emissions, measured by means of an opacimeter, is higher than 35% with respect to the gas oil as such. Said article also specifies that, with the same oxygen content, the entity of the reductions in the particulate matter emissions is more consistent for gas oil-diethyl carbonate blends with respect to gas oil-dimethyl carbonate blends.

Diethyl carbonate is a non-toxic compound, having a density equal to 975 kg/m³ and an oxygen content equal to 40.7% by weight, which, with respect to other oxygenated components for fuels such as, for example, dimethyl carbonate, ethanol, has the advantage of having a more favourable gas oil/water distribution coefficient. A further advantage of diethyl carbonate with respect to other oxygenated components for fuels, for example, methyl-tert-butyl ether (MTBE) , is that if it is accidentally released into the environment, it is slowly transformed, by hydrolytic decomposition, to carbon dioxide and ethanol, which are compounds having a low environmental impact .

The only oxygenated biocomponent currently used on a wide scale in blends with gas oil for producing fuels for diesel engines, is biodiesel which, however, as indicated above, can be used in amounts lower than or equal to 7% by volume with respect to the total volume of said blends. Consequently, at present, fuels for diesel engines (i.e. gas oils) only contain a limited amount of oxygenated biocomponents.

The Applicant has considered the problem of using higher amounts of oxygenated biocomponents, deriving from biodegradable and renewable energy sources, in compositions comprising gas oil, avoiding the drawbacks described above.

The Applicant has now found that the addition of diethyl carbonate deriving from bioethanol in compositions comprising gas oil and biodiesel allows compositions comprising a higher content of oxygenated biocomponents to be obtained, in particular allows to obtain gas oil compositions having a content of oxygenated biocomponents higher than or equal to 7.5% by volume with respect to the total volume of said compositions, which can be advantageously used as fuel for diesel engines.

In particular, the Applicant has found that the addition of said diethyl carbonate deriving from bioethanol allows the amount of oxygenated biocomponents to be increased in gas oil compositions without negatively influencing the characteristics of the starting gas oil, such as, for example, density, flash point, cetane number and cold properties such as the cloud point (CP) and the cold filter plugging point (CFPP) . Furthermore the addition of said diethyl carbonate deriving from bioethanol allows the amount of oxygenated biocomponents to be increased in gas oil compositions without negatively influencing the oxidation stability of the same.

Furthermore, the possibility of increasing the amount of oxygenated biocomponents in gas oil compositions allows the particulate matter emissions to be further reduced.

An object of the present invention therefore relates to a gas oil composition comprising:

- from 65% by volume to 92.5% by volume, preferably from 83% by volume to 89% by volume, with respect to the total volume of said composition, of at least one gas oil;

- from 0.5% by volume to 20% by volume, preferably from 1% by volume to 10% by volume, with respect to the total volume of said composition, of at least one diethyl carbonate, said diethyl carbonate being obtained from bioethanol;

- from 0.5% by volume to 15% by volume, preferably from 3% by volume to 7% by volume, with respect to the total volume of said composition, of at least one biodiesel; on the condition that the total amount of said diethyl carbonate and of said biodiesel is higher than or equal to 7.5% by volume with respect to the total volume of said composition.

For the purposes of the present description and of the following claims, the definitions of the numerical ranges always comprise the extremes unless otherwise specified.

For the purposes of the present invention, any gas oil can be used. In particular, said gas oil can be selected either from gas oils which fall within the specifications of gas oil for motor vehicles according to the standard EN 590:2009, or from gas oils which do not fall within these specifications.

Gas oil is generally a blend containing aliphatic hydrocarbons such as, for example, paraffins, aromatic hydrocarbons and naphthenes, typically having from 13 to 30 carbon atoms. The distillation temperature of the gas oil generally ranges from 160°C to 380°C.

According to a preferred embodiment of the present invention, said gas oil can have a density, at 15 °C, determined according to the standard EN ISO 3675:1998, ranging from 780 kg/m³ to 845 kg/m³ , preferably ranging from 800 kg/m³ to 840 kg/m³.

According to a preferred embodiment of the present invention, said gas oil can have a flash point, determined according to the standard EN ISO 2719:2002, higher than or equal to 55°C, preferably higher than or equal to 65°C.

According to a preferred embodiment of the present invention, said gas oil can have a cetane number, determined according to the standard EN ISO 5165:1998, higher than or equal to 51, preferably higher than or equal to 53. Said diethyl carbonate can be obtained by means of various processes known in the art for the synthesis of diethyl carbonate from ethanol .

According to a preferred embodiment of the present invention, said diethyl carbonate can be obtained by means of a process which comprises the transesterification of at least one dialkyl carbonate such as, for example, dimethyl carbonate, or of at least one cyclic carbonate such as, for example, ethylene carbonate, propylene carbonate, with bioethanol, in the presence of at least one catalyst. Said process is particularly advantageous as it uses non-toxic carbonylating agents (i.e. dialkyl carbonate, or cyclic carbonate) .

Said transesterification can be carried out at a temperature ranging from 50°C to 250°C, in the presence of at least one catalyst which can be selected from: inorganic basic compounds such as, for example, hydroxides (e.g., sodium hydroxide), alkoxides (e.g., sodium methoxide) ; alkaline metals or compounds of alkaline metals; organic basic compounds such as, for example, triethylamine , triethanolamine , tributylamine ; compounds of tin, titanium, zirconium or thallium; heterogeneous catalysts such as, for example, zeolites, modified zeolites such as, for example, titanium silicalites (e.g., titanium silicalite TS-1 treated with potassium carbonate) ; metal oxides belonging to group IVA and/or group IVB of the Periodic Table of Elements, preferably supported on a porous carrier; rare earth oxides.

In the case of the production of diethyl carbonate by the transesterification of dimethyl carbonate with bioethanol, the methanol co-produced can be removed by distillation as an azeotropic mixture with dimethyl carbonate, whereas the diethyl carbonate produced can be recovered by separating it by distillation from the excess of ethanol and from the methyl-ethyl carbonate which is the reaction intermediate.

In the case of the production of diethyl carbonate by the transesterification of ethylene carbonate or of propylene carbonate with bioethanol, the diethyl carbonate produced can be recovered by separating it by distillation from the excess of bioethanol, from the non-reacted alkylene carbonate and from the alkylene glycol co-produced.

Greater details relating to the above transesterification process are described in American patents US 4,181,676, US 4,062,884, US 4,661,609, US 4,307,032, US 5,430,170, US 5,847,189, or in Japanese patent application JP 2004/010571, or by Tatsumi et al . in "Chemical Communication" (1996) , page 2281, or by Anastas et al . in "Green Chemistry: Theory and Practice" (1998), Oxford University Press, page 11.

According to a further preferred embodiment of the present invention, said diethyl carbonate can be obtained by means of a process which comprises the reaction of urea with bioethanol, in the presence of at least one catalyst. This process uses urea as carbonylating agent, which is a non-toxic, inexpensive and easily available product. Furthermore, the possibility of recycling the ammonia co-produced to the production of urea, makes the synthesis process highly sustainable as it uses bioethanol and carbon dioxide.

The above process firstly involves the formation of ethyl carbamate which is subsequently converted to diethyl carbonate. Said process which can be either a single-step or two-step process, can be carried out at temperatures ranging from 100°C to 270°C, removing the reaction ammonia, in the presence of at least one catalyst which can be selected from: homogenous catalysts such as, for example, compounds of tin; heterogeneous catalysts such as, for example, metal oxides, or powder or supported metals; a bifunctional catalytic system, consisting of a Lewis acid and of a Lewis base; mineral acids or bases.

Greater details relating to the above production process of diethyl carbonate by the reaction of urea with bioethanol, can be found, for example, in the following documents .

European patent EP 0061672 and international patent application WO 95/17369, for example, describe synthesis processes of dialkyl carbonates from urea and alcohol carried out, in either a single step or two consecutive steps, in the presence of tin compounds as catalysts such as, for example, dibutyl-tin oxide, dibutyl-tin dimethoxide, at a temperature ranging from 120°C to 270°C, removing the reaction ammonia and recovering the product by distillation. The yields to dialkyl carbonate indicated for these processes are about 90% or higher.

Ball et al . in "Angewandte Chemie International Edition in English" (1980), Vol. 19, page 718, indicate that the formation step of the alkyl carbamate can be carried out at a relatively low temperature, ranging from 100°C to 170°C, whereas the production step of the dialkyl carbonate can be carried out at a temperature ranging from 180°C to 270°C. Both steps are conveniently carried out by removing the reaction ammonia, in the presence of a bifunctional catalytic system, consisting of a Lewis acid, such as diisobutyl aluminium hydride, and of a Lewis base, such as triphenylphosphine, which allows a reduction in the formation of by-products deriving from the decomposition of the alkyl carbamate.

American patent application US 2005/0203307 describes a synthesis process of dialkyl carbonates from urea and alcohol characterized in that the removal of the water present as impurity of the reagents and the partial or complete formation of alkyl carbamate takes place in a pre-reactor, in the absence of a catalyst, at a temperature ranging from 120°C to 180°C and at a pressure ranging from 0.2 MPa and 2 MPa. The production of dialkyl carbonate, on the other hand, takes place in a reactor equipped with a distillation column, in the, presence of at least one tin (IV) alkoxide such as, for example, dibutyltin dimethoxide and of at least one high-boiling solvent containing electron-donor atoms such as, for example, triglime (triethylene glycol dimethylether) . The reaction is carried out at a temperature of about 180°C and at a pressure of about 0.6 MPa, feeding to the reactor, the urea-alkyl carbamate bend in alcohol coming from the pre-reactor and removing the dialkyl carbonate at the head. The selectivity to dialkyl carbonate indicated for this process is about 91%-93%.

The above process for the synthesis of diethyl carbonate from bioethanol and urea can also be carried out in the presence of heterogeneous catalysts such as, for example, metal oxides, less toxic than organo-tin compounds. Wang et al, for example, in "Fuel Processing Technology" (2007), Vol. 88, page 807, indicate that among the oxides tested, zinc oxide is that which showed the best catalytic activity, even if the yields to diethyl carbonate obtained were much lower with respect to those of the processes previously described.

According to a further preferred embodiment of the present invention, said diethyl carbonate can be obtained by means of a process which comprises the oxidative carbonylation of bioethanol with carbon monoxide and oxygen, in the presence of at least one catalyst. Said process is preferably carried out in gas phase using heterogeneous catalysts such as, for example, CuCl₂/PdCl₂/AC, containing copper (II) chloride and palladium (II) chloride supported on activated carbon (AC) ; or CuCl₂/PdCl₂/AC-KOH, obtained from the previous catalyst for subsequent treatment with potassium hydroxide; or CuCl /PdCl₂/KCl/AC-NaOH, obtained by impregnation of activated carbon with CuCl₂, PdCl₂, KC1 and subsequent treatment with sodium hydroxide .

Greater details relating to the above oxidative carbonylation process of ethanol, are described, for example, by Yanji et al. in "Applied Catalysis A: General" (1998), Vol. 171, page 255; Dunn et al . in "Energy & Fuels" (2002), Vol. 16, page 177; Zhang et al . in "Journal of Molecular Catalysis A: Chemical" (2007), Vol. 266, page 202.

Said bioethanol can be obtained from fermentation processes from biomasses, that is from various agricultural products rich in carbohydrates and sugars, such as, for example, cereals, sugar, starch or rape crops, or mixtures thereof, known in the art.

According to a preferred embodiment of the present invention, said bioethanol can be obtained by the fermentation of at least one biomass deriving from agricultural crops, such as, for example, corn, sorghum, barley, beet, sugar cane, or mixtures thereof.

According to a further preferred embodiment of the present invention, said bioethanol can be obtained by the fermentation of at least one lignocellulosic biomass which can be selected from:

products of crops expressly cultivated for energy use (for example, miscanthus, foxtail, goldenrod, common cane) , including scraps, residues and waste products, of said crops or of their processing; products of agricultural cultivations, forestation and silviculture, comprising wood, plants, residues and waste products of agricultural processing, of forestation and of silviculture;

scraps of agro-food products intended for human nutrition or zootechnics ;

residues, not chemically treated, of the paper industry;

waste products coming from the differentiated collection of solid urban waste (e.g., urban waste of a vegetable origin, paper, etc.);

or mixtures thereof .

As indicated above, biodiesel comprises a blend of fatty acid alkyl esters, in particular a blend of fatty acid methyl esters (FAME) and can be produced starting from raw materials of a natural origin containing triglycerides (generally triesters of glycerine with fatty acids having a long alkyl chain) such as, for example, crude vegetable oils obtained by squeezing the seeds of oleaginous plants such as, for example, rape, palm, soya, sunflower, mustard, and also from other triglyceride sources such as, for example, algae, animal fats, or used or waste vegetable oils. Said raw materials as such, or the triglycerides obtained after subjecting said raw materials to separation, are subjected to a transesterification process in the presence of an alcohol, in particular, methanol, and a catalyst, in order to obtain said fatty acid alkyl esters, in particular said fatty acid methyl esters (FAME) . In addition to said fatty acid alkyl esters, glycerine is also obtained from said transesterification process, which must be separated as it is immiscible with said fatty acid alkyl esters. Said catalyst can preferably be selected from basic catalysts such as, for example, sodium hydroxide (NaOH) , potassium hydroxide (KOH) , sodium methoxide (NaOCH₃) . Alternatively, said catalyst can be selected from acid catalysts [e.g., sulfuric acid (H₂S0₄) , p- toluenesulfonic acid (C₇HS0₃H) ] ; enzymatic catalysts (e.g., lipase); heterogeneous catalysts based on metallic oxides (e.g., ZnO/Al₂0₃, MgO/Al₂0₃, ₂C0₃/A1₂0₃, Na/NaOH/Al₂0₃ , K 0₃/A1₂0₃, Zr0₂); or zeolites [e.g., NaX, NaX treated with potassium hydroxide (KOH) , ETS-10] .

Said biodiesel can also be produced starting from raw materials comprising, in addition to triglycerides, also free fatty acids, by means of a process comprising the esterification of said free fatty acids and the transesterification of said triglycerides with an alcohol (e.g., methanol). Said process can be carried out in a single step, or in two separate steps, in the presence of catalysts which can be selected from those described above .

Greater details on the production of biodiesel are described, for example, by Hanna et al . in the review "Biodiesel production: a review", published in "Bioresource Technology" (1999), Vol. 70, pages 1-15; or by Palligarnai et al . in the review "Biodiesel production: current state of the art and challenges", published in "Journal of Industrial Microbiology and Biotechnology" (2008), Vol. 35, pages 421-430; or by Di Serio et al . in the article "Heterogeneous catalyst for biodiesel production", published in "Energy & Fuels" (2008), Vol. 22, pages 207-217.

For the purposes of the present invention, blends can be used also comprising, in addition to said fatty acid alkyl esters, glycerine acetals, or glycerine ethers, or alkyl esters of glycerol carbonate, produced for using glycerine which, as indicated above, is obtained from the synthesis process of biodiesel. Said blends are described, for example, in international patent applications WO 2006/093896 and WO 2005/093015, in American patents US 6,174,501 and US 5,578,090, in European patent EP 1,569,923, and also in international patent application WO 2009/115274 in the name of the Applicant .

For the purposes of the present invention, any biodiesel comprising a blend of fatty acid alkyl esters, in particular a blend of fatty acid methyl esters (FAME) , can be used. Said biodiesel can preferably be selected from those which fall within the specifications of biodiesel for motor vehicles according to the standard EN 14214:2009.

According to a preferred embodiment of the present invention, said biodiesel can have a density, at 15 °C, determined according to the standard EN ISO 3675:1998, ranging from 860 kg/m³ to 900 kg/m³ , preferably ranging from 865 kg/m³ to _.890 kg/m³.

According to a preferred embodiment of the present invention, said biodiesel can have a flash point, determined according to the standard EN ISO 2719:2002, higher than or equal to 101°C, preferably higher than or equal to 140°C.

The composition of gas oil, object of the present invention, can optionally comprise conventional additives known in the art such as, for example, flow improvers, lubricity improvers, cetane improvers, antifoam agents, detergents, antioxidants, anticorrosion agents, antistatic additives, dyes, or mixtures thereof. These additives, if present, are generally present in an amount not higher than 0.3% by volume with respect to the total volume of said composition considered equal to 100.

Some illustrative and non-limiting examples are provided for a better understanding of the present invention and for its embodiment.

EXAMPLE 1

Synthesis of diethyl carbonate (BioDEC) by the transesterification of dimethyl carbonate (PMC) with bioethanol

The equipment used for the preparation of diethyl carbonate (BioDEC) consisted of a jacketed glass flask, having a volume of 2 litres, heated by circulation in the jacket of oil coming from a thermostatic bath, equipped with a magnetic stirrer, a thermometer and a glass distillation column with 30 perforated plates. All the vapour is condensed at the top of the column and only a part of the liquid is removed by the intervention of an electromagnetic valve.

The following reagents were added to the above glass flask, in an inert atmosphere: 1,081 g (12 moles) of dimethyl carbonate (purity equal to 99.9%), containing 200 mg/kg of water and 0.1% by weight of methanol; 1,106 g (23.9 moles) of anhydrous bioethanol (purity equal to 99.6%) for motor vehicles, in conformance with the standard EN 15376:2008, containing 1,000 mg/kg of water, 0.1% by weight of methanol and 0.2% by weight of C₃-C₅ saturated alcohols; 8.6 g of a solution of sodium methoxide at 30% by weight in methanol .

The reaction mixture was kept under stirring, at atmospheric pressure, and heated to boiling point. When the temperature at the top of the column became stabilized at a value of 63.5°C, the collection of the distillate, containing the azeotropic mixture of methanol-dimethyl carbonate, was initiated, operating with a reflux ratio which was such as to maintain the temperature at the top as constant as possible, thus minimizing the content of ethanol in the distillate.

In this first phase of the reaction, which lasted about 5 hours (temperature at the top of the column: 63.5°C - 64.5°C), an amount of distillate equal to 580.5 g was collected, characterized by the following composition, determined by gaschromatographic analysis:

69.5% by weight of methanol; 30.0% by weight of dimethyl carbonate;

0.5% by weight of ethanol .

In the second phase of the reaction, the reaction mixture remaining in the glass flask, after removal, by distillation, of the azeotropic mixture of methanol- dimethyl carbonate formed during said first reaction phase, was heated to boiling point, at atmospheric pressure, obtaining the transformation of most of the methyl-ethyl carbonate to diethyl carbonate (BioDEC) by reaction with bioethanol and the formation of methanol which was removed by distillation. In this second reaction phase, which lasted about 13 hours (temperature at the top of the column: 64.5°C - 124°C), an amount of distillate equal to 784.1 g was collected, characterized by the following composition, determined by gaschromatographic analysis:

19.5% by weight of methanol;

39.9% by weight of ethanol;

7.4% by weight of dimethyl carbonate;

- 23.4% by weight of methyl-ethyl carbonate;

9.8% by weight of diethyl carbonate (BioDEC).

The reaction mixture remaining in the glass flask, mainly containing diethyl carbonate, was subjected to distillation, operating at atmospheric pressure. At the end of the distillation (about 1 hour) , 768 g of distillate were collected, characterized by the following composition determined by gaschromatographic analysis:

- 99.5% by weight of diethyl carbonate (BioDEC); 0.5% by weight of methyl-ethyl carbonate.

The distillation residue was subjected to filtration to eliminate the catalyst, obtaining 61 g of product, mainly containing diethyl carbonate (BioDEC) (95.8% by weight) and dialkyl carbonates from C₃-C₅ alcohols (4.2% by weight) .

The synthesis of diethyl carbonate (BioDEC) , carried out as described above, was characterized by a conversion of dimethyl carbonate equal to 78.5%, a conversion of bioethanol equal to 71.3%, a selectivity of dimethyl carbonate to diethyl carbonate (BioDEC) equal to 80.7% and a selectivity of dimethyl carbonate to methyl-ethyl carbonate equal to 19.1%.

The diethyl carbonate (BioDEC) obtained has a purity equal to 99.5%.

EXAMPLE 2 (comparative)

A biodiesel having the characteristics indicated in Table 2, was added to a gas oil having the characteristics indicated in Table 1, in an amount equal to 7% by volume with respect to the total volume of the composition composed of gas oil + biodiesel: the characteristics of the composition obtained are indicated in Table 3. TABLE 1

(*) : cloud point

(**) : cold filter plugging point. TABLE 2

cloud point

cold filter plugging point

TABLE 3

(*) : cloud point

(**) : cold filter plugging point.

From the data indicated in Table 3 , it can be deduced that the addition of biodiesel to the gas oil composition in an amount equal to 7% by volume with respect to the total volume of the composition consisting of gas oil and biodiesel, does not negatively influence the characteristics of the starting gas oil.

EXAMPLE 3 (invention)

A biodiesel having the characteristics indicated in

Table 2, was added to a gas oil having the characteristics indicated in Table 1, in an amount equal to 7% by volume, together with diethyl carbonate (BioDEC) (purity equal to 99.5%) obtained according to Example 1 reported above, in different amounts, i.e. in an amount equal to 2% by volume and in an amount equal to 4% by volume, the amount of biodiesel and diethyl carbonate (BioDEC) being calculated with respect to the total volume of the composition consisting of gas oil, biodiesel and diethyl carbonate (BioDEC) : the characteristics of the composition obtained are indicated in Table 4.

TABLE 4

(*) : cloud point

(**) : cold filter plugging point.

From the data indicated in Table 4 , it can be deduced that the addition of oxygenated biocomponents, i.e. biodiesel and diethyl carbonate (BioDEC) obtained from bioethanol in gas oil compositions, in an amount equal to 9% by volume and 11% by volume, with respect to the total volume of the composition consisting of gas oil, biodiesel and diethyl carbonate (BioDEC) , does not negatively influence the characteristics of the starting gas oil, in particular with respect to the density, flash point, cetane number and cold properties such as cloud point (CP) , cold filter plugging point (CFPP) . It can also be deduced that although said gas oil compositions contain a higher amount of oxygenated biocomponents , they have an oxidation stability equal to that of the gas oil composition containing 7% by volume of biodiesel indicated in Example 2 (see Table 3) .

EXAMPLE 4 (comparative)

A biodiesel having the characteristics indicated in

Table 2, was added to a gas oil having the characteristics indicated in Table 5, in an amount equal to 7% by volume with respect to the total volume of the composition composed of gas oil + biodiesel: the characteristics of the composition obtained are indicated in Table 6.

TABLE 5

cloud point

cold filter plugging point

TABLE 6

(*) : cloud point

(**) : cold filter plugging point.

From the data indicated in Table 6 , it can be deduced that the addition of biodiesel to the gas oil composition in an amount equal to 7% by volume with respect to the total volume of the composition consisting of gas oil and biodiesel, does not negatively influence the characteristics of the starting gas oil.

EXAMPLE 5 (invention)

A biodiesel having the characteristics indicated in Table 2, was added to a gas oil having the characteristics indicated in Table 5, in an amount equal to 7% by volume, together with diethyl carbonate (BioDEC) (purity equal to 99.5%) obtained according to Example 1 reported above, in different amounts, i.e. in an amount equal to 2% by volume, in an amount equal to 4% by volume and in an amount equal to 6% by volume, the amount of biodiesel and diethyl carbonate (BioDEC) being calculated with respect to the total volume of the composition consisting of gas oil, biodiesel and diethyl carbonate (BioDEC) : the characteristics of the composition obtained are indicated in Table 7.

TABLE 7

(*) : cloud point; (**) : cold filter plugging point.

From the data indicated in Table 7, it can be deduced that the addition of oxygenated biocomponents, i.e. biodiesel and diethyl carbonate (BioDEC) obtained from bioethanol in gas oil compositions, in an amount equal to 9% by volume, 11% by volume and 13% by volume, with respect to the total volume of the composition consisting of gas oil, biodiesel and diethyl carbonate (BioDEC) , does not negatively influence the characteristics of the starting gas oil, in particular with respect to the density, flash point, cetane number and cold properties such as the cloud point (CP) , cold filter plugging point (CFPP) .

Claims

A gas oil composition comprising:

from 65% by volume to 92.5% by volume with respect to the total volume of said composition of at least one gas oil;

- from 0.5% by volume to 20% by volume with respect to the total volume of said composition of at least one diethyl carbonate, said diethyl carbonate being obtained from bioethanol;

- from 0.5% by volume to 15% by volume with respect to the total volume of said composition of at least one biodiesel;

on the condition that the total amount of said diethyl carbonate and of said biodiesel is higher than or equal to 7.5% by volume with respect to the total volume of said composition.

The gas oil composition according to claim 1, wherein said composition comprises from 83% by volume to 89% by volume with respect to the total volume of said composition of at least one gas oil. The gas oil composition according to claim 1 or 2 , wherein said composition comprises from 1% by volume to 10% by volume with respect to the total volume of said composition of at least one diethyl carbonate, said diethyl carbonate being obtained from bioethanol.

The gas oil composition according to any of the previous claims, wherein said composition comprises from 3% by volume to 7% by volume with respect to the total volume of said composition of at least one biodiesel.

The gas oil composition according to any of the previous claims, wherein said gas oil has a density, at 15 °C, determined according to the standard EN ISO 3675:1998, ranging from 780 kg/m³ and 845 kg/m³.

The gas oil composition according to claim 5, wherein said gas oil has a density, at 15°C, determined according to the standard EN ISO 3675:1998, ranging from 800 kg/m³ to 840 kg/m³.

The gas oil composition according to any of the previous claims, wherein said gas oil has a flash point, determined according to the standard EN ISO 2719:2002, higher than or equal to 55°C.

The gas oil composition according to claim 7, wherein said gas oil has a flash point, determined according to the standard EN ISO 2719:2002, higher than or equal to 65°C.

The gas oil composition according to any of the previous claims, wherein said gas oil has a cetane number, determined according to the standard EN ISO

5165:1998, higher than or equal to 51.

The gas oil composition according to claim 9, wherein said gas oil has a cetane number, determined according to the standard EN ISO

5165:1998, higher than or equal to 53.

The gas oil composition according to any of the previous claims, wherein said diethyl carbonate is obtained through a process comprising the transesterification of at least one dialkyl carbonate, or of at least one cyclic carbonate, with bioethanol in the presence of at least one catalyst .

The gas oil composition according to any of the claims from 1 to 10, wherein said diethyl carbonate is obtained through a process comprising the reaction of urea with bioethanol, in the presence of at least one catalyst.

The gas oil composition according to any of the claims from 1 to 10, wherein said diethyl carbonate is obtained through a process comprising the oxidative carbonylation of bioethanol with carbon monoxide and oxygen, in the presence of at least one catalyst.

The gas oil composition according to any of the previous claims, wherein said bioethanol is obtained from the fermentation of at least one biomass deriving from agricultural cultivations, such as corn, sorghum, barley, beetroot, sugar cane, or mixtures thereof.

The gas oil composition according to any of the claims from 1 to 13, wherein said bioethanol is obtained from the fermentation of at least one lignocellulosic biomass selected from:

products of crops expressly cultivated for energy use (such as miscanthus, foxtail, goldenrod, common cane) , including scraps, residues and waste products, of said crops or of their processing;

products of agricultural cultivations, forestation and silviculture, comprising wood, plants, residues and waste products of agricultural processing, of forestation and of silviculture ;

scraps of agro-food products intended for human nutrition or zootechnics ;

residues, not chemically treated, of the paper industry;

waste products coming from the differentiated collection of solid urban waste (such as urban waste of a vegetable origin, paper) ;

or mixtures thereof .

The gas oil composition according to any of the previous claims, wherein said biodiesel has a density, at 15 °C, determined according to the standard EN ISO 3675:1998, ranging from 860 kg/m³ to 900 kg/m³.

The gas oil composition according to claim 16, wherein said biodiesel has a density, at 15°C, determined according to the standard EN ISO 3675:1998, ranging from 865 kg/m³ to 890 kg/m³.

The gas oil composition according to any of the previous claims, wherein said biodiesel has a flash point, determined according to the standard EN ISO 2719:2002, higher than or equal to 101°C.

The gas oil composition according to claim 18, wherein said biodiesel has a flash point, determined according to the standard EN ISO 2719:2002, higher than or equal to 140°C.

The gas oil composition according to any of the previous claims, wherein said composition comprises additives such as flow improvers, lubricity- improvers, cetane improvers, antifoam agents, detergents, antioxidants, anti-corrosion agents, antistatic additives, dyes, in an amount not higher than 0.3% by volume with respect to the total volume of said composition taken equal to 100.

Use of the composition according to any of the claims from 1 to 20, as fuel for diesel engines.