WO2011045657A1

WO2011045657A1 - Gas oil composition comprising dialkyl carbonate from bioalcohol

Info

Publication number: WO2011045657A1
Application number: PCT/IB2010/002611
Authority: WO
Inventors: Giuseppe Bellussi; Marcello Notari; Elena Maria Rebesco; Maria Cristina Savarese; Pietro Scorletti; Despina Collia; Luca Paolo Serbolisca
Original assignee: Eni S.P.A.
Priority date: 2009-10-13
Filing date: 2010-10-11
Publication date: 2011-04-21
Also published as: IT1396205B1; WO2011045657A8; ITMI20101214A1; IT1401103B1; ITMI20091753A1

Abstract

Gas oil composition comprising: - at least one gas oil; - at least one dialkyl carbonate; wherein said dialkyl carbonate is obtained from bio- alcohol. Said composition can be advantageously used as fuel, for example, as fuel for burners, or for heating boilers. In particular, said composition can be advantageously used as fuel for diesel engines.

Description

GAS OIL COMPOSITION COMPRISING DIALKYL CARBONATE FROM BIOALCOHOL

The present invention relates to a gas oil composition comprising dialkyl carbonate.

More specifically, the present invention relates to a gas oil composition comprising at least one dialkyl carbonate obtained from bioalcohol .

The present invention also relates to the use of dialkyl carbonate obtained from bioalcohol as a component for gas oil.

The above composition can be advantageously used as fuel, for example, as fuel for burners, or for heating boilers .

In particular, 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 ( ΝΟχ ) , sulfur oxides (SO_x) , unburnt hydrocarbons (HC) , volatile organic compounds and particulate matter (PM) , are the cause of environmental problems such as, for example, the production of ozone, the greenhouse effect (in the case of nitrogen and carbon oxides) , 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 of hydrotreated vegetable oils (HVO) as such, or mixed with gas oil, and also of blends of gas oil comprising bioalcohols .

Biodiesel generally comprises a mixture of fatty acid alkyl esters, in particular a mixture 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 long-alkyl-chain fatty acids) such as, for example, raw 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. These raw materials as such, or triglycerides obtained after subjecting these 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) .

The> use of fatty acid methyl esters" (FAME) as such, or mixed with gas oil, however, can cause various problems in particular linked to:

- a low stability to oxidation, which can become particularly critical if the product remains for a long period of time inside the tank;

- poorer cold properties in terms of cloud point (CP) , pour point (PP) and cold filter plugging point (CFPP) which are generally higher with respect to the gas oil deriving from fossil sources ;

- increase in the emissions of nitrogen oxides (NO_x) .

The low stability to oxidation is one of the main problems associated with biodiesel, as described, for example, by Knothe G. in the review "Some aspects of biodiesel oxidative stability", published in "Fuel Processing Technology" (2007), Vol. 88, pg. 669-677. In said review, Knothe points out the fact that the oxidation process of biodiesel, mainly due to the presence of unsaturations in the alkyl chain of fatty acids of which it is formed, in addition to the presence of air, is influenced by various other factors such as, for example: the presence of light; the high temperature; the presence of metals, peroxides and/or antioxidants; as well as by the extension of the contact area between biodiesel and air. Knothe also points out the fact that the higher or lower oxidation stability of biodiesel depends on the nature of the oil, and therefore of the alkyl chain present in the triglycerides, from which it is initially produced.

In the article "Fuel properties and precipitate formation at low temperature in soy- , cottonseed- and poultry fat-based biodiesel blends" , published in "Fuel" (2008), Vol. 87, pg. 3006-3017, Tang et al . compare the cold properties of gas oil blends with biodiesel deriving from different triglyceride sources: that deriving from soya seed oil, with that deriving from cottonseed oil and with that deriving from poultry fat. In this article, Tang et al . underline the fact that the increase in the amount of biodiesel mixed with gas oil causes a deterioration in the cold properties, in particular, it causes an increase in the cloud point (CP) , pour point (PP) and cold filter plugging point (CFPP) . Furthermore, Tang et al . point out the fact that these cold properties depend on the origin of the biodiesel and therefore on the chemical structure of the alkyl chain contained therein: the worst cold properties were observed in the blends of gas oil with biodiesel of an animal origin.

Krahl J. et al. in the article "Comparison of exhaust emissions and their mutagenicity from the combustion of biodiesel, vegetable oil, gas-to-liquid and petrodiesel fuel", published in "Fuel" (2009), Vol. 88, pages 1064-1069, compare a biodiesel produced starting from rapeseed oil ["rapeseed methyl ester" (RME) ] with a reference gas oil ["diesel fuel" (DF) ] according to the standard EN590. The comparison was carried out according to the "13 -mode European Stationary Cycle" (ESC) . From the comparison, it emerges that the biodiesel produced from rapeseed oil (RME) used as such allows a reduction higher than about 55% of particulate matter (PM) emissions to be obtained, together with a reduction higher than about increase equal to about 20% of the emissions of nitrogen oxides (NO_x) , exceeding the Euro 3 limit for diesel engines.

Hydrotreated vegetable oils (HVO) , also known as green diesel, are produced by hydrogenation/deoxygenation of a material deriving from renewable sources such as, for example, soy oil, rape oil, corn oil, sunflower oil, 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. In said article, the best characteristics of said hydrotreated vegetable oils (HVO) are indicated, with respect to fatty acid methyl esters (FAME) , in particular, in terms of improved oxidation stability and improved cold properties. Furthermore, said hydrotreated vegetable oils (HVO) do not have the problem of 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 (PM) emissions. There is a tendency, however, towards a reduction in the particulate matter (PM) emissions, 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.

The use of alcohols deriving from renewable sources (i.e. bioalcohols) as such, or in a blend with gasoline, as fuels for gasoline engines, is also known in the art. Bioethanol, for example, can be used in a blend with gasoline in an amount of up to 85% by volume with respect to the total volume of the bioethanol- gasoline blend (E85) , whereas biobutanol can be used in a blend with gasoline in higher amounts, or it can even be used as such as fuel for gasoline engines. 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 products 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 fatty acid methyl esters (FAME) and of hydrotreated vegetable oils (HVO) described above.

Mixtures of bioalcohols with gas oil, normally known as "diesohol" are also known in the art. Said mixtures, however, for example mixtures of bioethanol- gas oil or mixtures of biobutanol-gas oil, can have various problems such as, for example, non-homogeneity, low cetane number, low flash point and poor lubricity.

One of the main problems, i.e. non-homogeneity, is linked to the fact that as bioethanol, for example, 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 said 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 bioethanol content. The results obtained show that the presence of water in the blends, the low temperatures and the high content of bioethanol, favour phase separation, whereas the presence of additives such as, for example, surfactants and/or co-solvents, have the opposite effect.

Biobutanol, on the other hand, has a better miscibility with gas oil than that of bioethanol but still not satisfactory however. At a low temperature, in fact, biobutanol-gas oil blends are not homogeneous. Studies have been carried out for overcoming this problem .

Chotwichien et al . , for example, in the article "Utilization of palm oil alkyl esters as an additive in ethanol-diesel and butanol-diesel blend", published in "Fuel" (2009), Vol. 88, pages 1618-1624, disclose the use of gas oil-biodiesel-alcohol blends. Said article underlines the fact that the most promising blend is that comprising 85% by volume of gas oil, 10% by volume of palm oil ethyl ester and 5% by volume of n-butanol: said blend in fact has a good homogeneity within a wide temperature range . Said blend however not only has the same drawbacks described above in relation to the use of fatty acid methyl esters (FAME) (i.e. biodiesel) , but also has a low flash point value.

As indicated above, a further problem linked to the use of bioalcohols such as, for example, bioethanol and biobutanol, is the low cetane number of the bioalcohol- gas oil blend, 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 composition comprising: a diesel 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 beet 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.

International patent application WO 2008/072039 describes a composition of tetra-component additives for the reformulation of ecological gasolines with improved octane properties and with a high oxygen content, consisting of: (A) diethyl carbonate (DEC); (B) diisopropyl ether (DIPE) ; (C) 2 , 2 , 3 - trimethyl butane; (D) branched hexane (E.R.). Said diethyl carbonate (DEC) derives from renewable sources as it is obtained by direct catalytic synthesis between carbon dioxide and ethyl ether, said ethyl ether deriving from the etherification of bioethanol. No mention is made of the possibility of using diethyl carbonate (DEC) deriving from renewable sources in gas oil.

It is also known in the art that the use of dxalkyl carbonates, such as, for example, 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 a 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.

Dialkyl carbonates are non-toxic compounds which can be used as oxygenated components for fuels. Due to its physico-chemical characteristics, dimethyl carbonate is more suitable for being used as component for gasolines, whereas dialkyl carbonates having a higher number of carbon atoms such as, for example, diethyl carbonate, di-n-butyl carbonate, are more suitable for being used as components for gas oils.

The Applicant has considered the problem of using bio-components such as, for example, bioethanol, other bioalcohols, or their derivatives, obtained from renewable sources, preferably from the fermentation of biomasses deriving from agricultural crops rich in carbohydrates and sugars, or from the fermentation of lignocellulosic biomasses, or from the fermentation of algal biomasses, as components for gas oil, in order to make the use of these renewable sources more effective and to rebalance the disequilibrium of the European production between gas oil and gasoline.

In particular, the Applicant has considered the problem of using dialkyl carbonates deriving from bio- components obtained from renewable sources, in particular bioalcohols, as components for gas oil.

The Applicant has now found that the addition to gas oil of at least one dialkyl carbonate deriving from bioalcohol, allows a composition to be obtained which can be advantageously used as fuel, in particular as fuel for diesel engines.

In particular, the Applicant has found that the addition of at least one dialkyl carbonate deriving from bioalcohol does not negatively influence the characteristics of the starting gas oil, such as, for example, the cold properties such as the cloud point (CP) and the cold filter plugging point (CFPP) . Furthermore said dialkyl carbonate is miscible with gas oil and consequently does not create problems of phase separation. The addition of said dialkyl carbonate, moreover, does not negatively influence the demulsification characteristics and lubricity of the composition. Furthermore, the addition of said dialkyl carbonate does not negatively influence the oxidation stability of the starting gas oil. The addition of said dialkyl carbonate, moreover, allows a consistent reduction in the particulate matter (PM) emissions in diesel engines.

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

- at least one gas oil;

- at least one dialkyl carbonate; wherein said dialkyl carbonate is obtained from bio- alcohol .

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 .

According to a preferred embodiment of the present invention, said gas oil can be present in said composition in an amount ranging from 75% by volume to 99.9% by volume, preferably ranging from 85% by volume to 98% by volume, with respect to the total volume of said composition.

According to a preferred embodiment of the present invention, said dialkyl carbonate can be present in said composition in an amount ranging from 0.1% by volume to 25% by volume, preferably ranging from 2% by volume to 15% by volume, with respect to the total volume of said composition.

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

The gas oil is generally a blend containing hydrocarbons such as, for example, paraffins, aromatic hydrocarbons and naphthenes, typically having from 9 to 30 carbon atoms. The distillation temperature of the gas oil generally ranges from 160°C to 450°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 12185 : 1996/Cl : 2001, 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 47, preferably higher than or equal to 51.

According to a preferred embodiment of the present invention, said gas oil can have a derived cetane number, determined according to the standard ASTM D6890:2008, higher than or equal to 47, preferably higher than or equal to 51.

According to a preferred embodiment of the present invention, said dialkyl carbonate can be selected from dialkyl carbonates having general formula (I) :

O

RO—C—OR, (I)

wherein R and R_i( the same or different, are selected from linear or branched alkyl groups, containing from 1 to 12 carbon atoms, preferably from 2 to 8 carbon atoms .

According to a further preferred embodiment of the present invention, said dialkyl carbonate can be selected from: diethyl carbonate; di-n-butyl carbonate; di-isobutyl carbonate; 1-butanol, 3 -methyl carbonate (di-isoamyl carbonate) ; 1-butanol, 2 -methyl carbonate; or mixtures thereof. Diethyl carbonate, di-n-butyl carbonate, or mixtures thereof, are preferred.

Said dialkyl carbonate can be obtained by means of various processes known in the art for the synthesis of dialkyl carbonate from alcohols.

According to a preferred embodiment of the present invention, said dialkyl 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 a cyclic carbonate such as, for example, ethylene carbonate, propylene carbonate, with at least one bioalcohol in the presence of at least one catalyst. Said process is particularly advantageous as it uses non-toxic carbonylating agents (i.e. dimethyl 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, either homogeneous or heterogeneous, which can be selected, for example, 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, lead, zinc or thallium; ion exchange resins; solid inorganic compounds such as, for example, hydrotalcites , aluminium silicates, 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 the Elements, preferably supported on a porous carrier; rare earth oxides.

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

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

Greater details relating to the above transesterification process are described, for example, 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, pg . 11, in which the transesterification of dialkyl carbonates with alcohols is described.

According to a further preferred embodiment of the present invention, said dialkyl carbonate can be obtained by means of a process which comprises the reaction of urea with at least one bioalcohol, 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 bioalcohol and carbon dioxide .

The above process firstly involves the formation of alkyl carbamate which is subsequently converted to dialkyl 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, in the presence of at least one catalyst which can be selected, for example, 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 a Lewis base; mineral acids or bases; and removing the ammonia co-produced.

Greater details relating to the above production process of dialkyl carbonate by the reaction of urea with at least one bioalcohol, can be found, for example, in the following documents, in which the reaction of urea with alcohols is described. European patent EP 61 672 and International patent application WO 95/17369, for example, describe synthesis processes of dialkyl carbonates from urea and alcohols 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 ammonia co-produced and recovering the product by distillation. The yields of dialkyl carbonate of 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 in the presence of a bifunctional catalytic system, consisting of a Lewis acid, such as diisobutylaluminium hydride, and a Lewis base, such as triphenylphosphine, which allows a reduction in the formation of by-products deriving from the decomposition of the alkyl carbamate, and removing the ammonia co-produced. 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 take 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 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 a pressure of about 0.6 MPa, feeding to the reactor, the urea-alkyl carbamate mixture in alcohol coming from the pre-reactor and removing the dialkyl carbonate at the top. The selectivity to dialkyl carbonate indicated for this process is about 91%-93%.

The above process for the production of dialkyl carbonate by the reaction of urea with at least one bioalcohol 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 dialkyl 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 dialkyl carbonate can be obtained by means of a process which comprises a first step in which at least one alkylene glycol is reacted with urea, in the presence of metal oxides as catalysts, so as to obtain alkylene carbonate, and a second step in which said alkylene carbonate is subjected to transesterification reaction with at least one bioalcohol, so as to obtain dialkyl carbonate and alkylene glycol, said alkylene glycol being recycled to said first reaction step.

Greater details relating to the above process for the production of dialkyl carbonate by the reaction of at least one alkylene glycol with urea and the subsequent transesterification with at least one bioalcohol, can be found, for example, in European patent EP 638 541 which describes the reaction of alkylene glycols with urea and subsequent transesterification with alcohols.

According to a further preferred embodiment of the present invention, said dialkyl carbonate, in particular diethyl carbonate, can be obtained by means of a process which comprises the oxidative carbonylation of at least one bioalcohol 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 CuCl₂/PdCl₂/KCl/AC-NaOH, obtained by impregnation of activated carbon with CuCl₂, PdCl₂, KCl and subsequent treatment with sodium hydroxide .

Greater details relating to the above oxidative carbonylation process of bioalcohol, are described, for example, by Yanj i 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, which describe the oxidative carbonylation of alcohols. According to a further preferred embodiment of the present invention, said bioalcohol can be selected from bioalcohols having general formula (II) :

R₂-OH (II)

wherein R₂ is selected from linear or branched alkyl groups, containing from 1 to 12 carbon atoms, preferably from 2 to 8 carbon atoms.

According to a further preferred embodiment of the present invention, said bioalcohol can be selected from: bioethanol, bio-n-butanol , bio-isobutanol, bio- 3- methyl-l-butanol, bio-2-methyl-l-butanol , or mixtures thereof. Bioethanol, bio-n-butanol, or mixtures thereof, are preferred.

Said bioalcohol can be obtained by the fermentation of biomasses or derivatives of biomasses, that is by the fermentation of biomasses deriving from agricultural crops rich in carbohydrates and sugars, or by the fermentation of lignocellulosic biomasses, or by the fermentation of algal biomasses.

According to a preferred embodiment of the present invention, said bioalcohol can be obtained by the fermentation of at least one biomass deriving from agricultural crops rich in carbohydrates and sugars, such as, for example, corn, sorghum, barley, beet, sugar cane, or mixtures thereof. According to a further preferred embodiment of the present invention, said bioalcohol 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 (such as, for example, miscanthus, foxtail millet, switchgrass, common cane) , including waste products, residues and scraps 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;

- waste of agro-food products destined for human feeding or zootechnics ;

- residues, not chemically treated, of the paper industry;

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

or mixtures thereof .

According to a further preferred embodiment of the present invention, said bioalcohol can be obtained by the fermentation of at least one algal biomass cultivated for energy purposes, or by the fermentation of residues or derivatives from the cultivation of said biomass .

Said fermentation can be carried out according to methods known in the art. Said fermentation can be carried out, for example, in the presence of natural microorganisms, or of microorganisms genetically modified for the purpose of improving said fermentation .

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

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

EXAMPLE 1

Synthesis of diethyl carbonate (BioDEC) by_ 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 3 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 bioethanol 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 bioethanol.

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 said 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 bioethanol;

- 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

Diethyl carbonate (BioDEC) (purity equal to 99.5%) obtained according to Example 1 above, was added in various amounts to a gas oil having the characteristics reported in Table 1. The amounts of diethyl carbonate and the characteristics of the gas oil after the addition of diethyl carbonate (BioDEC) are reported in Table 2.

TABLE 1

( * ) : cloud point ;

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

(*) : cloud point;

(**): cold filter plugging point;

(**^★) : variation with respect to starting gas oil.

From the data reported in Table 2, it can be deduced that the addition of diethyl carbonate (BioDEC) obtained from bioethanol, does not negatively influence the characteristics of the starting gas oil, in particular, with respect to the cetane number, density, flash point, cold properties such as cloud point (CP) and cold filter plugging point (CFPP) , demulsivity and oxidation stability.

EXAMPLE 3

Diethyl carbonate (BioDEC) (purity equal to 99.5%) obtained according to Example 1 above, was added in various amounts to a gas oil having the characteristics reported in Table 3. The amounts of diethyl carbonate and the characteristics of the gas oil after the addition of diethyl carbonate are reported in Table 4.

TABLE 3

( * ) : cloud point ;

(**) : cold filter plugging point.

From the data reported in Table 3, it can be deduced that said gas oil is particularly suitable for use in severe climates as it has optimum cold properties (cloud point) and cold filter plugging point .

TABLE 4

(*) : cloud point;

(**): cold filter plugging point.

From the data reported in Table 4, it can be deduced that the addition of diethyl carbonate (BioDEC) obtained from bioethanol, does not negatively influence the characteristics of the starting gas oil, in particular, with respect to the derived cetane number, density, flash point, cold properties such as cloud point (CP) and cold filter plugging point (CFPP) . Furthermore it can be deduced that the addition of diethyl carbonate (BioDEC) obtained from bioethanol allows gas oil compositions to be obtained which are particularly suitable for use in severe climates.

EXAMPLE 4

Synthesis of di-n-butyl carbonate (BioDBC) by transesterification of dimethyl carbonate (PMC) with bio-n-butanol

The equipment used for the preparation of di-n- butyl carbonate (BioDBC) consisted of a jacketed glass flask, having a volume of 5 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: 1,350 g (15 moles) of dimethyl carbonate (purity equal to 99.9%), containing 200 mg/kg of water and 0.1% by weight of methanol; 2,223 g (30 moles) of bio-n-butanol (purity equal to 99.6%) containing 1,000 mg/kg of water, 0.1% by weight of ethanol and 0.2% by weight of C₅ saturated alcohols; 10 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°C - 64°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 bio-n-butanol in the distillate .

In this first phase of the reaction, which lasted about 4 hours (temperature at the top of the column: 63°C - 64°C) , an amount of distillate equal to 911 g was collected, characterized by the following composition, determined by gaschromatographic analysis:

74.40% by weight of methanol;

- 25.57% by weight of dimethyl carbonate; 0.03% by weight of bio-n-butanol .

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 obtaining the transformation of most of the methyl-butyl carbonate to di-n-butyl carbonate (BioDBC) by reaction with bio-n- butanol and the formation of methanol which was removed by distillation. Said second reaction phase, which lasted about 6 hours, was carried out for the first 4 hours at atmospheric pressure (temperature at the top of the column: 64°C - 116°C) and for the remaining 2 hours gradually reducing the pressure from 760 mmHg to 40 mmHg. In said second phase, an amount of distillate equal to 563 g was collected, characterized by the following composition, determined by gaschromatographic analysis:

20% by weight of methanol;

73.5% by weight of bio-n-butanol;

2.9% by weight of dimethyl carbonate;

0.9% by weight of methyl-butyl carbonate;

2.2% by weight of di-n-butyl carbonate (BioDBC);

0.2% by weight of diethyl carbonate.

The reaction mixture remaining in the glass flask, mainly containing BioDBC, was subjected to distillation, operating at a pressure of 20 mmHg (temperature at the top of the column: 100°C) . At the end of the distillation (about 1 hour), 2,055.7 g of distillate were collected, characterized by the following composition determined by gaschromatographic analysis :

99.8% by weight of di-n-butyl carbonate (BioDBC); 0.2% by weight of methyl-butyl carbonate.

The distillation residue was subjected to filtration to eliminate the catalyst, obtaining 50 g of product, mainly containing di-n-butyl carbonate (BioDBC) (89.9% by weight) and dialkyl carbonates from C₅ alcohols (11.1% by weight).

The synthesis of di-n-butyl carbonate (BioDBC) , carried out as described above, was characterized by a conversion of dimethyl carbonate equal to 81.5%, a conversion of bio-n-butanol equal to 81.3%, and a selectivity of dimethyl carbonate to di-n-butyl carbonate (BioDBC) equal to 99.2%.

The di-n-butyl carbonate (BioDBC) obtained has a purity equal to 99.8%.

EXAMPLE 5

Di-n-butyl carbonate (BioDBC) (purity equal to 99.8%) obtained according to Example 4 above, was added to a gas oil having the characteristics reported in Table 5, in an amount equal to 7% by volume with respect to the total volume of the gas oil + di-n-butyl carbonate (BioDBC) composition, together with ethyl hexyl nitrate (cetane improver) in an amount equal to 0.05% by volume with respect to the total volume of said gas oil + di-n-butyl carbonate (BioDBC) composition considered as being equal to 100.

The characteristics of the gas oil after the addition of di-n-butyl carbonate (BioDBC) and ethyl hexyl nitrate are reported in Table 6.

TABLE 5

TABLE 6

From the data reported in Table 6, it can be deduced that the addition of di-n-butyl carbonate (BioDBC) obtained from bio-n-butanol , does not negatively influence the characteristics of the starting gas oil, in particular, with respect to the density, flash point, cold properties such as cloud point (CP) and cold filter plugging point (CFPP) , oxidation stability and lubricity.

EXAMPLE 6

The emissions of a Diesel motor vehicle fuelled with a composition comprising gas oil and diethyl carbonate (BioDEC) obtained from bioethanol according to the present invention were compared with those of the same motor vehicle fuelled with gas oil as such (the same gas oil but without diethyl carbonate) .

The motor vehicle used in the experimentation has a engine displacement equal to 1,900 cm³, Euro 4 homologation group, and is equipped with an oxidation catalyst .

The composition comprising gas oil and diethyl carbonate (BioDEC) was prepared by adding diethyl carbonate (BioDEC) to the gas oil (purity equal to 99.5%), obtained according to Example 1 above, in an amount equal to 4% by volume with respect to the total volume of the gas oil + diethyl carbonate (BioDEC) composition. The characteristics of the above composition and the gas oil as such used in the experimentation reported in Table 7.

TABLE 7

The experimentation was carried out according the New European Driving Cycle (NEDC) , consisting of an urban driving cycle and an extra-urban driving cycle, as shown in Figure 1.

During the whole test cycle, the contents were measured, in the emissions of the motor vehicle, of substances regulated according to European directives, i.e. carbon dioxide (CO), unburnt hydrocarbons (HC) , nitrogen oxides (NO_x) , total particulate matter (PM) and carbon dioxide (C0₂) .

The average values of two consecutive tests, of the content of said substances in the motor vehicle emissions, fuelled with gas oil as such and with the composition comprising gas oil and diethyl carbonate (BioDEC) , are reported in Table 8.

TABLE 8

From the data reported in Table 8, it can deduced that the addition to the gas oil of diethyl carbonate (BioDEC) obtained from bioethanol, in an amount equal to 4% by volume with respect to the total volume of the gas oil + diethyl carbonate (BioDEC) composition, allows a consistent reduction in the particulate matter (PM) emissions, equal to 11.1%, to be obtained.

EXAMPLE 7

The emissions of a Diesel motor vehicle fuelled with a composition comprising gas oil and di-n-butyl carbonate (BioDBC) obtained from bio-n-butanol according to the present invention were compared with those of the same motor vehicle fuelled with gas oil as such (the same gas oil but without di-n-butyl carbonate) .

The motor vehicle used in the experimentation has a engine displacement equal to 1,900 cm³, a common rail injector system, Euro 3 homologation group, and is equipped with an oxidation catalyst.

The composition comprising gas oil and di-n-butyl carbonate (BioDBC) was prepared by adding di-n-butyl carbonate (BioDBC) to the gas oil (purity equal to 99.8%), obtained according to Example 4 above, in an amount equal to 7% by volume with respect to the total volume of the gas oil + di-n-butyl carbonate (BioDBC) composition, and ethyl hexyl nitrate (cetane improver) in an amount equal to 0.05% by volume with respect to the total volume of said gas oil + di-n-butyl carbonate (BioDBC) composition considered as being equal to 100.

The characteristics of the above composition and of the gas oil as such used in the experimentation are reported in Table 9.

TABLE 9

The experimentation was carried out according to the New European Driving Cycle (NEDC) , consisting of an urban driving cycle and an extra-urban driving cycle, as shown in Figure 1.

The average value of four consecutive tests, of the content of said substances in the motor vehicle emissions, fuelled with gas oil as such and with gas oil containing di-n-butyl carbonate (BioDBC) , are reported in Table 10.

TABLE 10

From the data specified in Table 10, it can be deduced that the addition to the gas oil of di-n-butyl carbonate (BioDBC) obtained from bio-n-butanol , in an amount equal to 7% by volume with respect to the total volume of the gas oil + di-n-butyl carbonate (BioDBC) composition, allows a consistent reduction in the particulate matter (PM) emissions, equal to 26.9% to be obtained, with a benefit also on the emissions of unburnt hydrocarbons (HC) and carbon monoxide (CO) .

Claims

A gas oil composition comprising:

- at least one gas oil;

- at least one dialkyl carbonate;

wherein said dialkyl carbonate is obtained from bioalcohol .

The gas oil composition according to claim 1, wherein said gas oil is present in an amount ranging from 75% by volume to 99.9% by volume with respect to the total volume of said composition. The gas oil composition according to claim 2, wherein said gas oil is present in an amount ranging from 85% by volume to 98% by volume with respect to the total volume of said composition.

The gas oil composition according to any of the previous claims, wherein said dialkyl carbonate is present in an amount ranging from 0.1% by volume to 25% by volume with respect to the total volume of said composition.

The gas oil composition according to claim 4, wherein said dialkyl carbonate is present in an amount ranging from 2% by volume to 15% by volume with respect to the total volume of said composition .

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 12185:1996/01:2001 ranging from 780 kg/m³ to 845 kg/m³.

The gas oil composition according to claim 6, wherein said gas oil has a density, at 15°C, determined according to the standard EN ISO 12185:1996/01:2001, 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 8, 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 47.

The gas oil composition according to claim 10, 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 any of the previous claims, wherein said gas oil has a derived cetane number, determined according to the standard ASTM D6890:2008, higher than or equal to 47.

The gas oil composition according to claim 12, wherein said gas oil has a derived cetane number, determined according to the standard ASTM D6890:2008, higher than or equal to 51.

The gas oil composition according to any of the previous claims, wherein said dialkyl carbonate is selected from dialkyl carbonates having general formula (I) :

wherein R and Ri, the same or different, are selected from linear or branched alkyl groups, containing from 1 to 12 carbon atoms.

The gas oil composition according to claim 14, wherein in said general formula (I) , R and Ri, the same or different, are selected from linear or branched alkyl groups containing from 2 to 8 carbon atoms .

The gas oil composition according to claim 14 or 15, wherein said dialkyl carbonate is selected from: diethyl carbonate; di-n-butyl carbonate; di- isobutyl carbonate; 1-butanol, 3 -methyl carbonate (di-isoamyl carbonate) ; 1-butanol, 2 -methyl carbonate; or mixtures thereof.

The gas oil composition according to claim 16, wherein said dialkyl carbonate is selected from: diethyl carbonate, di-n-butyl carbonate, or mixtures thereof .

The gas oil composition according to any of the previous claims, wherein said dialkyl carbonate is obtained by means of a process which comprises the transesterification of at least one dialkyl carbonate, or of at least one cyclic carbonate, with at least one bioalcohol, in the presence of at least one catalyst.

The gas oil composition according to any of the claims from 1 to 17, wherein said dialkyl carbonate is obtained by means of a process which comprises the reaction of urea with at least one bioalcohol, in the presence of at least one catalyst.

The gas oil composition according to any of the claims from 1 to 17, wherein said dialkyl carbonate is obtained by means of a process which comprises a first step in which at least one alkylene glycol is reacted with urea, in the presence of metal oxides as catalysts, in order to obtain alkylene carbonate and a second step in which said alkylene carbonate is subjected to a transesterification reaction with at least one bioalcohol, in order to obtain dialkyl carbonate and alkylene glycol, said alkylene glycol being recycled to said first reaction step.

The gas oil composition according to any of the claims from 1 to 17, wherein said dialkyl carbonate is obtained by means of a process which comprises the oxidative carbonylation of at least one bioalcohol 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 bioalcohol is selected from bioalcohols having general formula (ID :

R₂-OH (II)

wherein R₂ is selected from linear or branched alkyl groups, containing from 1 to 12 carbon atoms.

The gas oil composition according to claim 22, wherein in said general formula (II) , R₂ is selected from linear or branched alkyl groups containing from 2 to 8 carbon atoms .

The gas oil composition according to claim 22 or 23, wherein said bioalcohol is selected from: bioethanol, bio-n-butanol , bio-isobutanol, bio-3- methyl -1-butanol, bio-2 -methyl - 1 -butanol , or mixtures thereof .

The gas oil composition according to claim 24, wherein said bioalcohol is selected from: bioethanol, bio-n-butanol , or mixtures thereof.

The gas oil composition according to any of the previous claims, wherein said bioalcohol is obtained by the fermentation of at least one biomass deriving from agricultural cultivations rich in carbohydrates and sugars such as corn, sorghum, barley, beet, sugar cane, or mixtures thereof .

The gas oil composition according to any of the claims from 1 to 25, wherein said bioalcohol is obtained by the fermentation of at least one lignocellulosic biomass which can be selected from: products of crops expressly cultivated for energy use (such as miscanthus, foxtail millet, switchgrass, common cane) , including waste products, residues and scraps of said crops or their processing;

products of agricultural cultivations, forestation and silviculture, comprising wood, plants, residues and waste products of agricultural processing, of forestation and of silviculture; waste of agro-food products destined for human feeding 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 claims from 1 to 25, wherein said bioalcohol is obtained by the fermentation of at least one algal biomass cultivated for energy purposes, or by the fermentation of residues or derivatives from the cultivation of said algal biomass.

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, anticorrosion agents, antistatic agents, dyes, in an amount not higher than 0.3% by volume with respect to the total volume of said composition considered as being equal to 100.

Use of the gas oil composition according to any of the previous claims, as fuel for burners, or for heating boilers.

31. Use of the gas oil composition according to any of the claims from 1 to 29, as fuel for diesel engines .

32. Use of dialkyl carbonate obtained from bioalcohol as component for gas oil.