WO2011073780A1

WO2011073780A1 - Composition comprising diethyl carbonate derived from bioethanol from vegetable oil

Info

Publication number: WO2011073780A1
Application number: PCT/IB2010/003272
Authority: WO
Inventors: Marcello Notari; Elena Maria Rebesco; Maria Cristina Savarese
Original assignee: Eni SpA
Current assignee: Eni SpA
Priority date: 2009-12-16
Filing date: 2010-12-13
Publication date: 2011-06-23
Anticipated expiration: 2012-06-16
Also published as: ITMI20092202A1; IT1397623B1

Abstract

Gas oil composition comprising: - from 5% by volume to 79.9% by volume, preferably from 30% by volume to 68% by volume, with respect to the total volume of said composition of at least one gas oil; from 0.1% by volume to 20% by volume, preferably from 2% by volume to 10% by volume, with respect to the total volume of said composition of at least one diethyl carbonate; from 20% by volume to 75% by volume, preferably from 30% by volume to 60% by volume, with respect to the total volume of said composition of at least one hydrotreated vegetable oil (HVO); wherein said diethyl carbonate is obtained from bio- ethanol. Said composition can be advantageously used as fuel for diesel engines.

Description

COMPOSITION COMPRISING DIETHYL CARBONATE DERIVED FROM BIOETHANOL FROM VEGETABLE OIL

The present invention relates to a gas oil composition comprising diethyl carbonate and hydrotreated vegetable oil (HVO) .

More specifically, the present invention relates to a gas oil composition comprising diethyl carbonate obtained from bioethanol and hydrotreated vegetable oil (HVO) .

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 the 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 fatty acid methyl esters (FAME) and of hydrotreated vegetable oils (HVO) as such, or in a mixture with gas oil, as well as of blends of gas oil comprising bioethanol.

Fatty acid methyl esters (FAME) , generally known as biodiesel, can be produced starting from crude vegetable oil (triglycerides) 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, by transesterification in the presence of methanol and of an acid or basic catalyst.

The use of said 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 fuels; - increase in the emissions of nitrogen oxides (NO_x) . The problems indicated above are known and have been 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; by Tang et al . 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; by 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, pg. 1064-1069.

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, pg. 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 oxidative stability and of cold properties. 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.

These hydrotreated vegetable oils (HVO) , however, generally have a high cetane number (normally higher than 60) , and this characteristic may in some way limit their capacity of reducing particulate matter emissions (PM) . It is known, in fact, that with other characteristics remaining identical, fuels having a high cetane number have a higher tendency towards the formation of particulate matter (PM) .

As is known, the ignitability of fuels for diesel engines is measured by their ignition delay time, i.e. the period of time necessary in a diesel engine between the start of the injection and the start of the combustion: the cetane number is a measurement of this ignition delay.

The shorter the ignition delay, the higher the cetane number of the fuel used will be, and consequently the lower will be the amount of fuel present in the combustion chamber when the ignition starts. A high cetane number is consequently preferable as it ensures ignition rapidity of the blend and therefore functioning fluidity, above all in the case of cold start. Over certain cetane number values, however, a further increase in the same has no practical effects, but, on the contrary, can be disadvantageous as the time necessary for a sufficient mixing of the fuel with air may be lacking, with a consequent increase in the smokiness at the exhaust and in the particulate matter emissions (PM) , as described for example, in "Motori a combustione interna per autotrazione" ("Internal combustion engines for motor vehicles") (1995), by R. Delia Volpe and M. Migliaccio, published by Liguori .

As mentioned above, blends of bioethanol with gas oil, usually known as "e-diesel" are also known in the art. These bioethanol/gas oil blends, however, have various problems such as, for example, non-homogeneity, a low cetane number, a 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, pg. 1351-1357. In said article are studied the conditions in which said blends are stable. The stability of said 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 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, 54.

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 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.

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 (PM) .

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 diesel/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 (N0_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, pg. 2691-2697, Ren et al . indicate the results of a bench experimentation carried out on a direct injection diesel engine, with a displacement equal to 903 cm³, at 2000 rpm, with the use of a gas oil containing different oxygenated compounds in variable percentages. For the blends of gas oil with diethyl carbonate and gas oil with dimethyl carbonate, the reduction in the particulate matter emissions (PM) , 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 blends of gas oil with diethyl carbonate with respect to blends of gas oil with dimethyl carbonate .

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 left in the environment, it is slowly transformed, by hydrolytic decomposition, to carbon dioxide and ethanol, which are compounds having a low environmental impact. Diethyl carbonate, however, has a low cetane number: in this respect, in the above- mentioned article "The influence of synthetic oxygenates on Euro 4 diesel passenger car exhaust emissions" published in SAE Report 2008-01-2387, Miloslaw et al . indicate a cetane number of diethyl carbonate equal to 13.8.

The Applicant has observed that the use of hydrotreated vegetable oil (HVO) in compositions comprising gas oil in high amounts (e.g., higher than or equal to 20% by volume with respect to the total volume of said compositions) can cause various drawbacks. In particular, the Applicant has observed that the use of hydrotreated vegetable oil (HVO) in high amounts can negatively influence the characteristics of the starting gas oil such as, for example, the density and the cetane number.

In order to increase the amount of components of a biological origin in said compositions, the Applicant has considered the problem of using high amounts (e.g., higher than or equal to 20% by volume with respect to the total volume of said compositions) of hydrotreated vegetable oil (HVO) in compositions comprising gas oil, avoiding the drawbacks described above.

The Applicant has now found that the addition of diethyl carbonate derived from bio-ethanol in compositions comprising gas oil and hydrotreated vegetable oil (HVO) in high amounts, allows to obtain compositions which do not show the drawbacks described above and can advantageously be used as fuel for diesel engines .

In particular, the Applicant has now found that the addition of said diethyl carbonate, in addition to increasing the percentage of components of a biological origin in said compositions comprising gas oil and hydrotreated vegetable oil (HVO) in high amounts, is capable of improving some of the characteristics such as, for example, the density and the cetane number. Furthermore, the addition of said diethyl carbonate does not negatively influence the other characteristics of said compositions comprising gas oil and hydrotreated vegetable oil (HVO) in high amounts, such as, for example, the cold properties such as the cloud point (CP) and the cold filter plugging point (CFPP) . Furthermore, the addition of said diethyl carbonate allows the absence of oxygen in said compositions comprising gas oil and hydrotreated vegetable oil (HVO) in high amounts, to be compensated, consequently further reducing the particulate matter emissions (PM) .

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

from 5% by volume to 79.9% by volume, preferably from 30% by volume to 68% by volume, with respect to the total volume of said composition of at least one gas oil;

from 0.1% by volume to 20% by volume, preferably from 2% by volume to 10% by volume, with respect to the total volume of said composition of at least one diethyl carbonate;

from 20% by volume to 75% by volume, preferably from 30% by volume to 60% by volume, with respect to the total volume of said composition of at least one hydrotreated vegetable oil (HVO) ;

wherein said diethyl carbonate is obtained from bio- ethanol .

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.

The 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 800 kg/m³ to 870 kg/m³, preferably ranging from 820 kg/m³ to 850 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 49, preferably higher than or equal to 51.

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 at least a 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 to group IVB of the Period 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 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) , pg. 2281, or by Anastas et al . in "Green Chemistry: Theory and Practice" (1998), Oxford University Press, pg. 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 a 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, metallic oxides, or powder or supported metals; a bifunctional catalytic system, consisting of a Lewis acid and 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, dibutyltin oxide, dibutyltin dimethoxide, at a temperature ranging from 120°C to 270°C, removing the reaction ammonia and recovering the product by distillation. The yields of dialkyl carbonates of these processes are about 90% or higher.

Ball et al . in "Angewandte Chemie International Edition in English" (1980), Vol. 19, pg. 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 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 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 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 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, pg. 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 by means of subsequent treatment with potassium hydroxide; or CuCl₂/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 Yanj i et al . in "Applied Catalysis A: General" (1998), Vol. 171, pg. 255; Dunn et al . in "Energy & Fuels" (2002), Vol. 16, pg. 177; Zhang et al . in "Journal of Molecular Catalysis A: Chemical" (2007) , Vol. 266, pg. 202.

Said bioethanol can be obtained by fermentation processes from biomasses, that is from agricultural crops rich in carbohydrates and sugars, such as, for example, cereals, sugary coltures, starchy products, vinasses, 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 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 (e.g., urban waste of a vegetable origin, paper, etc.).

or mixtures thereof .

Said hydrotreated vegetable oil (HVO) can be obtained by means of various processes known in the art. As indicated above, for example, said hydrotreated vegetable oil (HVO) can be obtained by hydrogenation/deoxygenation of a material deriving from renewable sources, such as, for example, soya 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, pg. 67-71.

It is known that, in order to improve the cold behaviour properties of hydrotreated vegetable oil (HVO) , the product obtained from the above hydrogenation/deoxygenation, suitably purified, can be subjected to a hydrogenation/isomerisation process, which transforms a part of the n-paraffins present in said product into isoparaffins , as described, for example, in European patent application 1,728,844 and in international patent application WO 2008/058664.

For the purposes of the present invention, any hydrotreated vegetable oil (HVO) can be used.

According to a preferred embodiment of the present invention, said hydrotreated vegetable oil (HVO) can have a density, at 15°C, determined according to the standard EN ISO 3675:1998, ranging from 720 kg/m³ to 820 kg/m³, preferably ranging from 750 kg/m³ to 800 kg/m³.

According to a preferred embodiment of the present invention, said hydrotreated vegetable oil (HVO) 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.

The composition of gas oil object of the present invention can optionally comprise fatty acid methyl esters (FAME) in an amount lower than or equal to 10% by volume, preferably lower than or equal to 7% by volume, with respect to the total volume of said composition considered equal to 100.

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, antifoaming 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 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 hydrotreated vegetable oil (HVO) having the characteristics indicated in Table 2, was added to a gas oil having the characteristics specified in Table 1, in an amount equal to 45% by volume with respect to the total volume of the composition composed of gas oil and hydrotreated vegetable oil (HVO) : 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 hydrotreated vegetable oil (HVO) in a high amount negatively influences the characteristics of the starting gas oil, in particular with respect to the density which proves to be lower than the specification limit according to the standard EN 590 : 2009 . EXAMPLE 3 (invention)

A hydrotreated vegetable oil (HVO) having the characteristics indicated in Table 2, was added to a gas oil having the characteristics specified in Table 1, in an amount equal to 45% by volume, together with diethyl carbonate (BioDEC) (purity equal to 99.5%) obtained according to Example 1 indicated above, in an amount equal to 4% by volume, said amounts being calculated with respect to the total volume of the composition composed of gas oil, hydrotreated vegetable oil (HVO) and diethyl carbonate: the characteristics of the composition obtained are indicated in Table .

TABLE 4

(*) : cloud point

(**) : cold filter plugging point.

From the data indicated in Table 4, it can be deduced that the addition of diethyl carbonate (BioDEC) obtained from bioethanol, improves the properties of the composition composed of gas oil and hydrotreated vegetable oil (HVO) with respect to the density which thus falls within the specification limits according to the standard EN 590:2009. Furthermore, the addition of diethyl carbonate (BioDEC) obtained from bioethanol does not negatively influence the other characteristics of said composition, in particular, with respect to the flash point, cetane number, cold properties such as the cloud point (CP) and the cold filter plugging point (CFPP) .

Claims

1. Gas oil composition comprising:

from 5% by volume to 79.9% by volume with respect to the total volume of said composition of at least one gas oil;

from 0.1% by volume to 20% by volume with respect to the total volume of said composition of at least one diethyl carbonate;

from 20% by volume to 75% by volume with respect to the total volume of said composition of at least one hydrotreated vegetable oil (HVO) ;

wherein said diethyl carbonate is obtained from bio- ethanol .

2. The gas oil composition according to claim 1, wherein said composition comprises from 30% by volume to 68% by volume with respect to the total volume of said composition of at least one gas oil.

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

4. The composition according to any of the previous claims, wherein said composition comprises from 30% by volume to 60% by volume with respect to the total volume of said composition of at least one hydrotreated vegetable oil (HVO) .

5. The 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 800 kg/m³ to 870 kg/m³.

6. The 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 820 kg/m³ to 850 kg/m³.

7. The 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.

8. The 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.

9. The 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 49.

10. The 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 51.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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 millet, switchgrass, common cane) , including waste products, residues and scraps, of said crops or of of their processing;

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

- residues, not treated chemically, 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 .

16. The gas oil composition according to any of the previous claims, wherein said hydrotreated vegetable oil (HVO) has a density, at 15°C, determined according to the standard EN ISO 3675:1998, ranging from 720 kg/m³ to 820 kg/m³.

17. The gas oil composition according to claim 16, wherein said hydrotreated vegetable oil (HVO) has a density, at 15°C, determined according to the standard EN ISO 3675:1998, ranging from 750 kg/m³ to 800 kg/m³.

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

19. The gas oil composition according to claim 18, wherein said hydrotreated vegetable oil (HVO) has a flash point, determined according to the standard EN ISO 2719:2002, higher than or equal to 65°C.

20. The gas oil composition according to any of the previous claims, wherein said composition comprises methyl esters of fatty acids (FAME) in an amount lower than or equal to 10% by volume with respect to the total volume of said composition considered equal to 100.

21. The gas oil composition according to claim 20, wherein said composition comprises methyl esters of fatty acids (FAME) in an amount lower than or equal to 7% by volume with respect to the total volume of said composition considered equal to 100.

22. 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 considered equal to 100.

23. Use of the composition according to any of the claims from 1 to 22, as fuel for diesel engines.