Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
PROCESS FOR THE PREPARATION OF CYCLIC ACETALS THAT CAN BE USED AS COMPONENTS FOR DIESEL FUELS
Document Type and Number:
WIPO Patent Application WO/2018/116207
Kind Code:
A1
Abstract:
The present invention relates to a process for preparing cyclic acetals that can be used as components for diesel fuel. More specifically, the present invention relates to a process for preparing cyclic acetals having an ethereal function that can be used as diesel fuel components preferably starting from precursors of a biological origin such as, for example, starting from glycerol of a biological origin. With the process of the present invention, it is possible, for example, to prepare etherified cyclic acetals having a 1,3-dioxolane and 1,3-dioxane structure, that can be used as diesel fuel components, starting from non-etherified cyclic acetals having a 1,3-dioxolane structure, which in turn can be obtained from glycerol derivatives, in particular glycerol of a biological origin, such as 1,2-diols, for example, 1,2-propanediol.

Inventors:
ASSANELLI GIULIO (IT)
MOLINARI DANIELE (IT)
Application Number:
PCT/IB2017/058216
Publication Date:
June 28, 2018
Filing Date:
December 20, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ENI SPA (IT)
International Classes:
C07D317/22; C07D317/34
Domestic Patent References:
WO2015155659A12015-10-15
WO2014125416A12014-08-21
WO2013150457A12013-10-10
WO2009039347A12009-03-26
WO2005093015A12005-10-06
WO2013150457A12013-10-10
WO2014125416A12014-08-21
WO2015155659A12015-10-15
Other References:
MORI K ET AL: "Catalytic dehydration of 1,2-propanediol into propanal", APPLIED CATALYSIS A: GENERAL, ELSEVIER, AMSTERDAM, NL, vol. 366, no. 2, 25 September 2009 (2009-09-25), pages 304 - 308, XP026520648, ISSN: 0926-860X, [retrieved on 20090718], DOI: 10.1016/J.APCATA.2009.07.018
FARACI, G.; GOSLING, C.; HOLMGREN, J.; MARINANGELI, R.; MARKER, T.; PEREGO, C.: "New developments in renewable fuels offer more choices", HYDROCARBON PROCESSING, September 2007 (2007-09-01), pages 67 - 71
CHEN, H.; WANG, J.; SHUAI, S.; CHEN, W.: "Study of oxygenated biomass fuel blends on a diesel engine", FUEL, vol. 87, 2008, pages 3462 - 3468, XP023438346, DOI: doi:10.1016/j.fuel.2008.04.034
GARCIA, E.; LACA, M.; PEREZ, E.; GARRIDO, A.; PEINADO, J.: "New class of acetal derived from glycerin as a biodiesel fuel component", ENERGY & FUELS, vol. 22, 2008, pages 4274 - 4280, XP055054852, DOI: doi:10.1021/ef800477m
BELLUSSI, G.; PEREGO, C.; CARATI, A.; PERATELLO, S.; PREVIDE MASSARA, E.: "Amorphous mesoporous silica-alumina with controlled pore size as acid catalysts", STUDIES IN SURFACE SCIENCE AND CATALYSIS, vol. 84, 1994, pages 85 - 92
Attorney, Agent or Firm:
MARTURANO, Pasqualino (IT)
Download PDF:
Claims:
CLAIMS

1. Process for preparing at least one cyclic acetal having general formula (I) and/or (II) :

(I) (ID

which comprises reacting, at a temperature ranging from 30 to 150°C, in the presence of an acid catalyst, a reaction mixture comprising a cyclic acetal having formula III) :

(in)

and at least one etherified 1,2-diol having formula (IV) :

CH2OH-CHOH-CH2OR' (IV),

obtaining the cyclic acetal having formula (I), and/or at least one etherified 1,3-diol having formula (V) :

CH2OH-CHOR"-CH2OH (V) , obtaining the cyclic acetal having formula (II), wherein R and R'", equal to or different from each other, can be independently selected from H and an alkyl having from 1 to 6 carbon atoms, and R' and R", equal to or different from each other, can be an alkyl having from 1 to 6 carbon atoms.

Process according to claim 1, wherein, in said cyclic acetal of formula (III), R and '" are independently selected from H, CH3 and C2H5.

Process according to claim 1 or 2, wherein, in said cyclic acetal of formula (I), R' is selected from CH3, C2H5, C3H7 and C4H9, and preferably is selected from C2H5 and C3H7.

Process according to any one of the claims from 1 to 3, wherein, in said cyclic acetal of formula (II), R" is selected from CH3 and C2H5, C3H7 and C4H9, and preferably is selected from C2H5 and C3H7. Process according to any one of the claims from 1 to 4, wherein, when the reaction mixture with the cyclic acetal of formula (III) comprises at least one etherified 1,2-diol of formula (IV) in substantial absence of etherified 1,3-diol of formula (V) or comprises at least one etherified 1,3-diol of formula (V) in substantial absence of etherified 1,2-diol of formula (IV), in the above- mentioned reaction mixture said etherified 1,2- diol of formula (IV) or said etherified 1,3 diol of formula (V) is present in a percentage preferably comprised between 20% and 90% by weight with respect to the total weight of the mixture, preferably comprised between 40% and 80% by weight, more preferably comprised between 60% and 80% by weight with respect to the total weight of the mixture, the complement making up to 100% consisting of the cyclic acetal of formula (III) .

6. Process according to any one of the claims from 1 to 4, wherein, when both the etherified 1,2-diol of formula (IV) and the etherified 1,3-diol of formula (V) are comprised in the reaction mixture with the cyclic acetal of formula (III), said etherified diols are preferably collectively present in the reaction mixture in a percentage comprised between 20% and 90% by weight with respect to the total weight of the mixture, preferably in a percentage comprised between 40% and 80% by weight, more preferably in a percentage comprised between 60% and 80% by weight with respect to the total weight of the mixture, the complement making up to 100% consisting of the cyclic acetal of formula (III) .

7. Process according to any one of the claims from 1 to 6, wherein, in formula (III) said R is methyl and said R'" is hydrogen.

8. Process according to any one of the claims from 1 to 7, wherein said temperature is comprised between 40°C and 120°C and preferably it is comprised between 40°C and 80°C.

9. Process according to any one of the claims from 1 to 8, wherein said process is carried out by maintaining the reaction mixture in liquid phase.

10. Process according to any one of the claims from 1 to 9, wherein said process is carried out at a pressure comprised between 0.5 MPa and 5 MPa and preferably it is carried out at a pressure comprised between 1 MPa and 4 MPa.

11. Process according to any one of the claims from 1 to 10, wherein said solid acid catalyst is selected from acidic ion-exchange resins, zeolites in the acid form, silicoaluminas , supported phosphoric acid and mixtures thereof.

12. Process according to any one of the claims from 1 to 11, wherein said process is carried out continuously and the space velocity LHSV of the reaction mixture on the catalyst is comprised between 0,1 and 20 hf1, preferably comprised between 1 and 10 hf1 and more preferably comprised between 2 and 8 hf1.

13. Process according to any one of the claims from 1 to 12, carried out in at least one fixed bed reactor filled with acid catalyst.

14. Process according to any one of the claims from 1 to 12, carried out in at least one fixed bed reactor with the recycle of continuously unconverted reagents.

15. Process according to any one of the claims from 1 to 14, wherein said cyclic acetal of formula (III) is obtained by a process comprising the steps of:

a) providing a reaction mixture comprising at least one 1,2-diol of formula (VI) :

Ri-CH2-CHOH-CH2OH (VI),

wherein Ri is selected from H and an alkyl having from 1 to 5 carbon atoms, said mixture being substantially free of aldehydes; b) subjecting said reaction mixture to a heat treatment at a temperature comprised between 100°C and 300°C in the presence of an acid catalyst, thus obtaining said cyclic acetal of formula (III) .

16. Process according to any one of the claims from 1 to 14, wherein a cyclic acetal of formula (VII) is obtained by a process comprising the steps of:

a' ) providing a reaction mixture comprising at least one 1,2-diol of formula (VI) :

Ri-CH2-CHOH-CH2OH (VI),

wherein Ri is selected from H and an alkyl having from 1 to 5 carbon atoms, and at least one etherified 1,2-diol of formula (IV) :

CH2OH-CHOH-CH2OR' (IV)

wherein R' is an alkyl having from 1 to 6 carbon atoms, said mixture being substantially free of aldehydes;

b' ) subjecting said reaction mixture to a heat treatment at a temperature comprised between 100°C and 300°C in the presence of an acid catalyst, thus obtaining a mixture comprising the cyclic acetal of formula (VII) and the etherified cyclic acetal of formula (VIII) :

(VII) (VIII) wherein R and R' have the meanings described above ;

c' ) separating the cyclic acetal of formula (VII) from said mixture obtained in step b' ) , preferably by distillation.

17. Process according to claim 16, wherein said 1,2-diol of formula (VI) and said etherified 1,2- diol of formula (IV) are present in the mixture of step a') in a molar ratio comprised between 0.5 and 12, preferably comprised between 2 and 10.

18. Process according to any one of the claims from 15 to 17, wherein the heat treatment of steps b) or b' ) in the presence of an acid catalyst is carried out at a temperature comprised between 110°C and 200°C and preferably at a temperature comprised between 115°C and 150°C.

19. Process according to any one of the claims from 15 to 18, wherein said heat treatment of steps b) or b' ) is carried out at a pressure comprised between 0,5 MPa and 5 MPa, preferably comprised between 1 MPa and 4 MPa.

20. Process according to any one of the claims from 15 to 19, wherein the acid catalyst, in the presence of which said heat treatment of steps b) or b' ) is carried out, is selected from acidic ion-exchange resins, zeolites in the acid form, silicoaluminas, supported phosphoric acid and mixtures thereof.

Description:
Process for the preparation of cyclic acetals that can be used as components for diesel fuels

~k ~k ~k ~k ~k

The present invention falls within the field of fuel components.

In particular, the present invention relates to a process for preparing cyclic acetals that can be used as components for diesel fuel.

More specifically, the present invention relates to a process for preparing cyclic acetals having an ethereal function that can be used as diesel fuel components preferably starting from precursors of a biological origin such as, for example, starting from glycerol of a biological origin.

With the process of the present invention, it is possible, for example, to prepare etherified cyclic acetals having a 1 , 3-dioxolane and 1,3-dioxane structure, that can be used as diesel fuel components, starting from non-etherified cyclic acetals having a 1 , 3-dioxolane structure, which in turn can be obtained from glycerol derivatives, in particular glycerol of a biological origin, such as 1,2-diols, for example, 1,2- propanediol .

As is known, the accumulation in the atmosphere of carbon dioxide (CO 2 ) , carbon monoxide (CO) , nitrogen oxides (ΝΟχ) , sulfur oxides (SO x ) , unburned hydrocarbons (HC) , volatile organic compounds and particulate (PM) , present in the emissions produced by the combustion of fuels of a fossil origin, causes the persistence and aggravation of environmental problems such as, for example, acid rain, and global overheating due to the greenhouse effect.

In recent years, a mature awareness of environmental problems has caused attention to be focused on so-called bio-fuels, i.e. fuels from renewable sources and of a biological origin deriving, for example, from the treatment of algae, vegetable biomass, oils and fats of a plant or animal origin, etc ..

New national and supranational regulations and directives, on the other hand, impose, within a strict time limits, the ever-expanding use of these biofuels, in particular in the field of automotive fuels.

In particular, the European Directive 2009/28/EC, known as "Renewable Energy Directive (RED) " envisages a communitarian target of 20% for the overall share of energy from renewable sources and a target of 10% for the share of automotive fuels from renewable sources within 2020, sustaining and promoting the production and use of bio-fuels. In addition, the European Directive 2009/30/EC, known as the "Fuel Quality Directive" (FQD), imposes fuel producers to reduce the greenhouse gas emissions by 6% in automotive fuels, with respect to the reference value of 2010. It is evident that this result can be achieved by using formulations of fossil fuels added with ever increasing amounts of biofuels or other components deriving from renewable sources.

Biodiesel and HVO (or Green Diesel) are among the most important biofuels.

Biodiesel is a biofuel composed of monoalkyl esters of long-chain fatty acids deriving from vegetable oils or animal fats and which meets the international standard ASTM D6751-15c and is part of the European standard specification EN 13214-2008. Pure biodiesel (B100) does not contain oil derivatives, it is common practice, however, to prepare and use mixtures of biodiesel at 10% by volume, 20% by volume and 50% by volume with respect to the total volume of the mixture, with gasoil of a fossil origin (respectively defined as B10, B20 and B50) .

Pure biodiesel can be produced starting from raw materials of a biological origin containing triglycerides (triesters of glycerol with long-alkyl- chain fatty acids) . These are subjected to transesterification with a short-chain alcohol in the presence of a catalyst; when the alcohol used in the transesterification reaction is methanol, fatty acid methyl esters (FAMEs) are obtained.

Some features of FAMEs make biodiesel a better fuel than gasoil; for example, the cetane number, the lubricity, the flash point and oxygen content are higher with respect to the corresponding fuel of fossil origin, against a substantial absence of aromatic hydrocarbons, in particular polycyclic aromatic hydrocarbons (PAH and sulfur compounds. Due to its chemical composition, on the other hand, biodiesel consisting of FAMEs has various drawbacks linked to a lower stability to oxidation and to degradation processes caused by bacterial proliferation. The oxygen present in FAME can generate peroxides, which can catalyze the formation of gums and other insoluble compounds, which deposit on the filters and other parts of the engine. Furthermore, the addition of FAMEs to gasoil reduces its cold performance and increases the emission of NO x by combustion.

The main problems relating to the use of biodiesel based on FAMEs are described in the report Concawe n. 9/09 "Guidelines for handling and blending FAME" of November 2009.

In addition, a drawback associated with the production process of biodiesel based on FAMEs is represented by obtaining, as by product, high quantities of glycerol, in percentage equal to about 10% by weight with respect to the weight of FAMEs obtained, whose market is now generally considered mature .

An alternative process for producing biofuels from renewable sources exploits the hydrotreatment of vegetable oils obtaining so-called HVOs (Hydrotreated Vegetable Oils) . HVOs consist of linear paraffinic chains or with a low branching degree, free of aromatic hydrocarbons and PAH, oxygen and sulfur, characterized by a high cetane number. HVOs, which have the characteristics of a diesel fuel (and in fact constitute so-called Green Diesel) can be obtained by the hydrodeoxygenation of a material of a biological origin, such as, for example, palm oil, soybean oil, rapeseed oil, corn oil, sunflower oil, comprising triglycerides and possibly free fatty acids, in the presence of hydrogen and a catalyst, optionally followed by the hydroisomerization of the product obtained, always in the presence of hydrogen and a catalyst, with the aim of increasing the proportion of branched hydrocarbons, as described, for example, in WO 2009/039347 Al .

It is known that HVOs represent an improvement with respect to biodiesel based on FAMEs, in particular in terms of greater stability to oxidation and better cold properties (Faraci, G., Gosling, C., Holmgren, J., Marinangeli, R., Marker, T., Perego, C., in "New developments in renewable fuels offer more choices", Hydrocarbon Processing, September 2007 issue, pages 67- 71) . Furthermore, HVOs with respect to FAMEs do not have the problem of increasing the emission of NO x by combustion .

HVOs, on the other hand, are characterized by a lower density with respect to gasoil of fossil origin and, due to the lack of oxygen atoms in their molecular structure, they do not provide significant benefits for the reduction of particulate when used in diesel engines in a blend with gasoil, in a quantity lower than 5% by volume with respect to the total volume of said blend.

In order to counteract this inconvenience, resort can be made to the addition, to diesel fuels comprising HVOs, of oxygenated compounds which favour the complete combustion of hydrocarbons and therefore reduce the emission of particulate (Chen, H., Wang, J., Shuai, S., Chen, W., "Study of oxygenated biomass fuel blends on a diesel engine" (2008), Fuel, vol. 87, pages 3462-3468) .

The obtainment of the above-mentioned oxygenated compounds starting from glycerol, and in particular glycerol of a biological origin, has proved to be an effective expedient for exploiting the fraction of the same glycerol, obtained in production processes of biodiesel in excess with respect to market demands (Garcia, E., Laca, M. Perez, E., Garrido, A., Peinado, J., "New class of acetal derived from glycerin as a biodiesel fuel component" (2008), Energy & Fuels, vol.22, pages 4274-4280) .

In WO 2005/093015 Al , a process is described for the production of biofuels through the transformation of triglycerides into at least two families of bio- fuels, containing monoesters of fatty acids and soluble ethers and/or acetals of glycerol. Said ethers and acetals of the known art have a high affinity to water and a low miscibility with the hydrocarbon phase: these characteristics limit the use of these compounds as fuel components as they favour the solubilization of non-negligible quantities of water, responsible, inter alia, of possible corrosion phenomena of the metal parts of the engine.

International patent application WO 2013/150457, filed by the Applicant, describes new fuel compositions comprising hydrophobic derivatives of glycerol, represented by cyclic acetals or ketals of the type 1 , 3-dioxolane and 1,3-dioxane comprising no hydroxy substituent. Due to their hydrophobic behaviour, the above-mentioned compounds provide high performances as fuel components as they allow to overcome the known drawbacks of acetals linked to their high affinity with water and low affinity with the remaining hydrocarbon component of the fuel, at the same time contributing to the reduction of the particulate emission and without significantly altering the characteristics of the fuel, for example the "cloud point" ( CP ) , the cold filter plugging point ( C FPP ) , the characteristics of demulsibility, the lubricity properties (lubricity) .

The above-mentioned cyclic acetals or ketals of the 1 , 3-dioxolane and 1,3-dioxane type are prepared by means of a process comprising the following steps:

(1) transformation of glycerine into propanediol or alkoxy-propanediol ,

(2) reaction of the diol obtained in step (1) with a carbonyl compound selected from aldehydes and ketones, to give the desired cyclic acetal or ketal .

It is important to note that said process provides the use of a pure carbonyl compound, in step (2), selected from aldehydes and ketones, previously synthetized and isolated.

International patent application WO 2014/125416, filed by the Applicant, describes an integrated process for the production of fuel components comprising:

- the transformation of glycerol into an alkoxy- propanediol having formula Z O- CH 2 - CHOH- CH 2 OH , wherein Z is a linear or branched Ci- Cs alkyl, the transformation of glycerol into 1,2- propanediol ,

- the dehydration of the 1 , 2-propanediol obtained to propionic aldehyde,

the reaction of part of the propionic aldehyde obtained with the alkoxy-propanediol having formula Z O- CH2 - CHOH- CH2OH , to give an acetal having formula ( C ) :

(C) wherein Z is a linear or branched Ci-Ce alkyl,

the oxidation of part of the propionic aldehyde obtained to propionate having formula CH 3 -CH 2 -COOT, wherein T is a linear or branched Ci-Ce alkyl.

Also in this case, the synthesis of the cyclic acetal passes through the reaction of an etherified diol with a carbonyl compound, in this specific case propionic aldehyde, which is specifically obtained by dehydration of 1 , 2-propanediol .

International patent application WO 2015/155659, filed by the Applicant, describes a process for the preparation of cyclic acetals of the type 1 , 3-dioxolane that can be used, for example, as fuel components having general formula (D) :

(D) wherein Y and Y' , equal or different from each other, are independently selected from H and an OZ' group, Z' being a linear or branched alkyl containing from 1 to 8 carbon atoms. The embodiments of the invention which provide that Y and/or Y' be OZ', i.e. those in which the cyclic acetal having formula (D) is etherified, are preferred, particularly for use as diesel fuel components.

In fact, it is important to note that, although the process described in WO 2015/155659 allows cyclic acetals to be obtained wherein both Y and Y' can be H, however it is preferable that at least one substituent selected from Y and Y' to be an ethereal group. Only the cyclic acetals having formula (D) wherein at least one substituent Y or Y' is OZ' , are, in fact, characterized by boiling points sufficiently high for being used in diesel fuel compositions.

The above process comprises the following steps:

(i) providing a reaction mixture comprising at least one vicinal diol having formula Q- CH2-CHOH- CH2OH wherein Q is selected from H and a group OZ' , Z' being a linear or branched alkyl containing from 1 to 8 carbon atoms,

ii) subjecting said reaction mixture to heat treatment at a temperature within the range of 100°C- 300°C in the presence of at least one acid catalyst.

Even if the process described in WO 2015/155659 is characterized by excellent yields, it is particularly simple when a compound having formula (D) wherein Y is the same as Y' , is to be obtained. Otherwise, in order to obtain compounds having formula (D) wherein Y is different from Y' , in step (i) of the process, a reaction mixture must be provided, comprising at least two vicinal diols of formula Q- CH2-CHOH- CH2OH having respectively two different Q groups corresponding to Y and Y' , whose subsequent heat treatment will lead to the formation of at least four different compounds having formula (D) mixed together. In other words, with the process of WO 2015/155659, the production yield of a compound having formula (D) will only be optimal when said desired compound is characterized by a residue Y equal to Y' . The production yield of a compound having formula (D) wherein the two residues Y and Y' are different, on the other hand, will be inversely proportional to the number of compounds having formula (D) having the different combinations of Y and Y' that can be theoretically obtained through this process.

It is therefore evident that in the case described above, the overall yield of the process can be compromised by obtaining undesired compounds having formula (D) ; furthermore, the isolation of the mixture of products of a single compound having formula (D) having any residue Y different from the residue Y' , could prove to be difficult and involve adopting various separation and purification steps.

The Applicant has therefore considered the problem of finding a process which allows an etherified cyclic acetal to be obtained in a simple way and with high yields, that can be advantageously used as diesel fuel component, and that can overcome the drawbacks of the processes of the known art described above.

A new process has now been found which unexpectedly allows cyclic acetals having a 1 , 3-dioxolane and 1,3- dioxane structure and functionalized with an ethereal residue, to be obtained directly, starting from a non- etherified cyclic acetal having a 1 , 3-dioxolane structure, which is reacted with a diol functionalized with said ethereal residue.

Both types of products, i.e. the cyclic acetal functionalized with the above-mentioned ethereal residue having a 1 , 3-dioxolane structure, and the cyclic acetal functionalized with the above-mentioned ethereal residue having a 1,3-dioxane structure, can be advantageously used, possibly also in a mixture, as diesel fuel components.

The starting non-etherified cyclic acetal is preferably obtained by means of heat treatment, in the presence of an acid catalyst, of at least one 1,2-diol with the substantial absence of carbonyl compounds previously synthetized and purified.

In this way, the glycerol obtained as by-product of transesterification or hydrolysis reactions of the triglycerides contained in lipids of a vegetable or animal origin used in production processes of bio- fuels, can be exploited, through the process of the present invention, in a simple and economically convenient way.

When the starting non-etherified cyclic acetal is therefore obtained from at least one 1,2-diol, in turn deriving from glycerol from renewable sources (for example, from the transesterification or hydrolysis of triglycerides contained in lipids of a vegetable or animal origin) , compounds are obtained, through the process of the present invention, which intrinsically have a biological origin and which therefore contribute to obtaining so-called "advanced" bio-fuels, capable of complying with the restrictions of the most recent international reference directives.

Further characteristics and advantages of the present invention will appear evident from the following detailed description.

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

In the description of the embodiments of the present invention, the terms "comprising" and "containing" indicate that the options described, relating, for example, to the steps of a method or process or the components of a product or device, are not necessarily exhaustive. It is important to note, however, that the object of the present patent application also relates to embodiments in which the term "comprising" referring to the options described - regarding, for example, the steps of a method or process or the components of a product or device should also be interpreted as "which essentially consists of" or "which consists of" even if not explicitly declared.

For the purposes of the present description and following claims, the percentages are always by weight, except in cases where it is not otherwise specified.

For the purposes of the present description and following claims, whenever reference is made to a compound, whether it be a reagent or a product, of which there may be several stereoisomers, (R) - (S) enantiomers, for example, in the case in which there is at least one asymmetric sp 3 carbon, said reference to said compound comprises all of its possible stereoisomers .

For the purposes of the present description and following claims, "molecule with a 1 , 3-dioxolane structure" refers to any cyclic molecule comprising the 1 , 3-dioxolane nucleus.

For the purposes of the present description and following claims, "molecule with a 1,3-dioxane structure" refers to any cyclic molecule comprising the 1,3-dioxane nucleus.

For the purposes of the present description and following claims, "etherified" compound (for example "etherified diol" or "etherified cyclic acetal") refers to a compound comprising at least one ethereal functional group (for example OR') in its own structural formula, R' being an alkyl having from 1 to 6 carbon atoms .

For the purposes of the present description and following claims, "carbonyl compound" refers to a compound characterized by the functional group C=0 which, when reacted with a diol, can generate an adduct such as an acetal or ketal . Aldehydes, ketones, urea, alkyl carbonates, dialkyl carbonates, etc., are included, for example, among carbonyl compounds.

A first object of the present invention therefore relates to a process for the preparation of at least one cyclic acetal having the following general formula (I) and/or (II) :

which comprises reacting, at a temperature ranging from 30 to 150°C, in the presence of an acid catalyst, a reaction mixture comprising a cyclic acetal having formula (III) :

(III)

and at least one etherified 1,2-diol having formula (IV) :

CH 2 OH-CHOH-CH 2 OR' (IV),

obtaining the cyclic acetal having formula (I),

and/or at least one etherified 1,3-diol having formula (V) :

CH 2 OH-CHOR"-CH 2 OH (V) ,

obtaining the cyclic acetal having formula (II), wherein R and R'", equal to or different from each other, can be independently selected from H and an alkyl having from 1 to 6 carbon atoms, and R' and R", equal to or different from each other, can be an alkyl having from 1 to 6 carbon atoms.

It is important to note that the cyclic acetal having formula (III) can be used as a mixture of different geometric and/or optical isomers: for the purposes of the present process, either single isomers or mixtures of said isomers can be used. Analogously, the final cyclic acetals having formula (I) and (II) can be produced as mixtures of different geometric isomers: also in this case, either the single isomers or mixtures of said isomers can be used in the composition of fuels.

In the process of the present reaction, a 1,2-diol of formula CH 2 OH-CHOH-CH 2 R'" is always obtained as co- product, both when the above-mentioned etherified 1,2- diol having formula (IV) is used, and also when the above-mentioned etherified 1,3-diol having formula (V) is used. This co-product can be easily separated from the etherified cyclic acetals having formula (I) and (II) by means of distillation, and recycled for other uses or further condensation to produce cyclic acetals of formula (III) .

In the cyclic acetal having formula (III), R and R'" can be independently selected, for example, from H, CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 , C 5 H 11 , C 6 H 13 , and are preferably selected from H, CH 3 and C 2 H 5 . In a particularly preferred aspect, R is CH 3 and R'" is H. In this case, the cyclic acetal having formula (III) is 2-ethyl-4-methyl-l , 3- dioxolane.

In another preferred aspect of the present invention, R and R'" in the acetal of formula (III) are equal to each other and in particular they are both hydrogen .

In the cyclic acetal having formula (I), and therefore in the etherified 1,2-diol having formula (IV) , R' can be selected, for example, from CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 , C 5 H 11 , C 6 H 13 , R' is preferably selected from CH 3 , C 2 H 5 , C 3 H 7 and C 4 H 9 , R' is even more preferably selected from CH 3 , C 2 H 5 and n-C 3 H 7 .

In a particularly preferred aspect, R' is C 3 H 7 . R is preferably H or CH 3 and R' is C 3 H 7 . When R is CH 3 and R' is C 3 H 7 , the cyclic acetal having formula (I) is 2- ethyl-4-propoxymethyl-l , 3-dioxolane .

In a particularly preferred aspect, R' is C 2 H 5 . R is preferably H or CH 3 and R' is C 2 H 5 . When R is CH 3 and R' is C 2 H 5 , the cyclic acetal having formula (I) is 2- ethyl-4-ethoxymethyl-l , 3-dioxolane .

In another particularly preferred aspect, R' is CH 3 . R is preferably H or CH 3 and R' is CH 3 . When R is CH 3 and R' is CH 3 , the cyclic acetal having formula (I) is 2- ethyl-4-methoxymethyl-l , 3-dioxolane .

In the cyclic acetal having formula (II), and therefore in the etherified 1,3-diol having formula

(V) , R" can be selected, for example, from CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 , C 5 H 11 , C 6 Hi 3 , and R" is preferably selected from CH 3 , C 2 H 5 , C 3 H 7 and C 4 H 9 . R" is even more preferably selected from CH 3 , C 2 H 5 and n-C 3 H 7 .

In a particularly preferred aspect, R" is n-C 3 H 7 . R is preferably H or CH 3 and R" is n-C 3 H 7 . When R is CH 3 and R" is n-C 3 H 7 , the cyclic acetal having formula (II) is 2-ethyl-5-propoxy-l , 3-dioxane .

In a particularly preferred aspect, R" is C 2 H 5 . R is preferably H or CH 3 and R" is C 2 H 5 . When R is CH 3 and R" is C 2 H 5 , the cyclic acetal having formula (II) is 2- ethyl-5-ethoxy-l , 3-dioxane .

In another particularly preferred aspect, R" is CH 3 . R is preferably H or C¾ and R" is C¾. When R is C¾ and R" is CH 3 , the cyclic acetal having formula (II) is 2- ethyl-5-methoxy-l , 3-dioxane .

As described above, the process of the present invention comprises the reaction, in the presence of an acid catalyst, between the above-mentioned cyclic acetal having formula (III) and an etherified diol, selected from an etherified 1,2-diol having formula (IV) and an etherified 1,3-diol having formula (V) and requires no addition of any carbonyl compound to the reaction mixture, such as, for example, an aldehyde, with which said diols could form an acetal and in general a condensation adduct .

The process of the present invention is characterized in that, when the cyclic acetal having formula (III) is reacted in the presence of an acid catalyst with an etherified 1,2-diol having formula (IV), the above-mentioned cyclic acetal having formula (III) unexpectedly selectively exchanges only its R'" functional group with the ethereal functional group OR' of said etherified 1,2-diol having formula (IV), and is therefore transformed into the etherified cyclic acetal having the 1 , 3-dioxolane structure of formula (I), as represented hereunder:

+ CH2OH-CHOH-CH2OR ' + CH2OH-CHOH- CH2R 1

:iii) (IV) (I)

A derivative of 1 , 2-propanediol is formed as co- product in the reaction, in which the residual R'" deriving from the cyclic acetal having formula (III), is present.

When the above-mentioned cyclic acetal having formula (III) is reacted in the presence of said acid catalyst with an etherified 1,3-diol having formula (V) , on the other hand, in addition to the selective exchange of its R'" functional group with the ethereal functional group OR" of said etherified 1,3-diol having formula (V) , there is an unexpected enlargement of the heterocyclic ring obtaining the etherified cyclic acetal having the structure of the 1,3-dioxane having formula (II), as represented h reunder:

+ CH 2 OH-CHOR"-CH 2 OH ¾ + CH 2 OH-CHOH-CH 2 R'" (III) (V) II)

Also in this case, a derivative of 1 , 2-propanediol is formed as co-product in the reaction, in which the residual R'" deriving from the cyclic acetal having formula (III), is present.

In a preferred aspect of the present invention, the above-mentioned process allows a cyclic acetal having general formula (I) to be obtained:

wherein R can be selected from H and an alkyl having from 1 to 6 carbon atoms and R' can be an alkyl having from 1 to 6 carbon atoms, and wherein said process comprises reacting, at a temperature ranging from 30 °C to 150°C, in the presence of an acid catalyst, a reaction mixture comprising said cyclic acetal having formula (III) and at least one etherified 1,2-diol having formula (IV) :

CH 2 OH-CHOH-CH 2 OR' (IV),

wherein R' has the meanings described above, obtaining the cyclic acetal having formula (I) .

In another preferred aspect of the present invention, the above-mentioned preparation process allows a cyclic acetal having general formula (II) to be obtained:

(ID

wherein R can be selected from H and an alkyl having from 1 to 6 carbon atoms and R" can be an alkyl having from 1 to 6 carbon atoms, and wherein said process comprises reacting, at a temperature ranging from 30 °C to 150°C, in the presence of an acid catalyst, a reaction mixture comprising said cyclic acetal having formula (III) and at least one etherified 1,3-diol having formula (V) :

CH 2 OH-CHOR"-CH 2 OH (V) , wherein R" has the meanings described above, obtaining the cyclic acetal having formula (II) .

In a further preferred aspect, the above-mentioned etherified diols having formula (IV) and (V) can be used in a mixture: in this case, the process can comprise the reaction in the presence of an acid catalyst at a temperature ranging from 30°C to 150°C, of a reaction mixture comprising the above-mentioned cyclic acetal having formula (III), at least one etherified 1,2-diol having formula (IV) and at least one etherified 1,3-diol having formula (V) . The product obtained will be a mixture of etherified cyclic acetals having formula (I) and formula (II), with the above- mentioned derivative of 1 , 2-propanediol CH2OH-CHOH-CH2R'" as co-product. Said mixture, after removing the co- product by means of simple distillation, can be advantageously used as diesel fuel component without any further purification steps.

In a preferred aspect of the invention, the etherified 1,2-diol having formula (IV) is obtained by means of an etherification process of glycerol with at least one alcohol, according to conventional methods, for example by reacting glycerol with at least one alcohol having formula R'OH, wherein R' can be an alkyl having from 1 to 6 carbon atoms, in the presence of at least one acid catalyst. The glycerol is preferably obtained as by-product of transesterification or hydrolysis reactions of triglycerides of a biological origin; the alcohol having formula R'OH used for the etherification is preferably obtained biologically, for example by the fermentation of biomasses or biomass derivatives, in particular lignocellulosic or algal biomasses .

The etherified 1,2-diol having formula (IV) is preferably selected from the group consisting of 3- methoxy-1, 2-propanediol, 3-ethoxy-l, 2-propanediol, 3- propoxy-1, 2-propanediol, 3-butoxy-l, 2-propanediol, 3- pentoxy-1, 2-propanediol, 3-hexoxy-l , 2-propanediol and mixtures thereof and is more preferably selected from 3-methoxy-l, 2-propanediol, 3-ethoxy-l, 2-propanediol, 3- propoxy-1 , 2-propanediol and mixtures thereof.

In a particularly preferred aspect, the etherified 1,2-diol having formula (IV) is 3-methoxy-l , 2- propanediol .

In a second particularly preferred aspect, the etherified 1,2-diol having formula (IV) is 3-ethoxy- 1 , 2-propanediol .

In a third particularly preferred aspect, the etherified 1,2-diol having formula (IV) is 3-propoxy- 1 , 2-propanediol .

In a preferred aspect of the invention, the etherified 1,3-diol having formula (V) is obtained by means of an etherification process of glycerol with at least one alcohol, according to conventional methods, for example by reacting glycerol with at least one alcohol having formula R"OH, wherein R" can be an alkyl having from 1 to 6 carbon atoms, in the presence of at least one acid catalyst. The glycerol is preferably obtained as by-product of transesterification or hydrolysis reactions of triglycerides of a biological origin; the alcohol having formula R"OH used for the etherification is preferably obtained biologically, for example by the fermentation of biomasses or biomass derivatives, in particular lignocellulosic or algal biomasses .

The etherified 1,3-diol having formula (V) is preferably selected from the group consisting of 2- methoxy-1, 3-propanediol, 2-ethoxy-l, 3-propanediol, 2- propoxy-1, 3-propanediol, 2-butoxy-l, 3-propanediol, 2- pentoxy-1, 3-propanediol, 2-hexoxy-l , 3-propanediol and mixtures thereof and is more preferably selected from 2-methoxy-l, 3-propanediol, 2-ethoxy-l, 3-propanediol, 2- propoxy-1 , 3-propanediol and mixtures thereof.

In a particularly preferred aspect, the etherified 1,3-diol having formula (V) is 2-methoxy-l , 3- propanediol .

In a second particularly preferred aspect, the etherified 1,3-diol having formula (V) is 2-ethoxy-l , 3- propanediol .

In a third particularly preferred aspect, the etherified 1,3-diol having formula (V) is 2-propoxy- 1 , 3-propanediol .

In a preferred aspect of the invention, the etherification process of glycerol with an alcohol can produce a mixture comprising both an etherified 1,2- diol and an etherified 1,3-diol. As described above, said mixture can be advantageously used in the process of the present invention without separating the two compounds from each other and purifying them, allowing an etherified cyclic acetal with a 1 , 3-dioxolane structure having formula (I), and an etherified cyclic acetal with a 1,3-dioxane structure having formula (II), to be simultaneously obtained. In a preferred aspect of the invention, when the reaction mixture with the cyclic acetal having formula (III) comprises at least one etherified 1,2-diol having formula (IV) in the substantial absence of etherified 1,3-diol having formula (V) or comprises at least one etherified 1,3-diol having formula (V) in the substantial absence of etherified 1,2-diol having formula (IV), in the above reaction mixture, said etherified 1,2-diol having formula (IV) or said etherified 1,3-diol having formula (V) is present in a percentage preferably ranging from 20% to 90% by weight with respect to the total weight of the mixture, the complement to 100% consisting of the cyclic acetal having formula (III) and preferably ranging from 40% to 80% by weight with respect to the total weight of the mixture. In a particularly preferred aspect, in the above reaction mixture, the etherified 1,2-diol having formula (IV) or the etherified 1,3-diol having formula (V) is present in a percentage ranging from 60% to 80% by weight with respect to the total weight of the mixture, the complement to 100% consisting of the cyclic acetal having formula (III) .

In a preferred aspect of the invention, when the reaction mixture with the cyclic acetal having formula (III) comprises both the etherified 1,2-diol having formula (IV) and the etherified 1,3-diol having formula (V) , said etherified diols are preferably present in the reaction mixture in an overall percentage ranging from 20% to 90% by weight with respect to the total weight of the mixture, the complement to 100% consisting of the cyclic acetal having formula (III) and preferably in a percentage ranging from 40% to 80% by weight with respect to the total weight of the mixture. In a particularly preferred aspect, in the above reaction mixture, the above etherified diols are present in a percentage ranging from 60% to 80% by weight with respect to the total weight of the mixture, the complement to 100% consisting of the cyclic acetal having formula (III) .

When both the etherified 1,2-diol having formula (IV) and the etherified 1,3-diol having formula (V) are included with the cyclic acetal having formula (III) in the reaction mixture, the weight percentage ratio between the two etherified diols preferably ranges from 1%:99% by weight to 99%:1% by weight and more preferably from 50%:50% by weight to 95%:5% by weight.

The process of the present invention can be carried out at a temperature ranging from 30°C to 150°C and is preferably carried out at a temperature ranging from 40°C to 120°C. In a particularly preferred aspect, said process is carried out at a temperature ranging from 40°C to 80°C.

The process according to the invention is preferably carried out keeping the reaction mixture in liquid phase. For this purpose, the process can be carried out at a pressure ranging from 0.5 MPa to 5 MPa and preferably at a pressure ranging from 1 MPa to 4 MPa.

The acid catalyst used in the process of the present invention can be selected from ion-exchange acid resins, zeolites in acid form, silicoaluminas , supported phosphoric acid and mixtures thereof. The ion-exchange acid resins can be used directly in the form of microspheres, as normally available on the market. The acid zeolites and silica-alumina are preferably extruded together with a binder.

Acid resins that can be used are those containing sulfonic or carboxylic groups as acid groups.

Commercial resins can be used, for example, such as Amberlyst A-36, Amberlyst A-70, Amberlyst BD-20, Amberlite IR-120, Amberlite IRC-86, Amberlite IRC-50, Nafion.

Preferred zeolites are medium-pore or large-pore zeolites, even more preferably zeolite Y, Beta zeolite or ZSM-5 zeolite.

The zeolites are used in acid form, i.e. in the form in which the cationic sites present in their structure are occupied for at least 50% by hydrogen ions, and it is especially preferable for at least 90% of the cationic sites to be occupied by hydrogen ions.

Silico-aluminas that can be used are, for example, those having a silica : alumina molar ratio ranging from 1:1 to 1000:1, and even more preferably from 20:1 to 200 : 1.

Silico-aluminas that can be used are described, for example, in Bellussi, G., Perego, C, Carati, A., Peratello, S., Previde Massara, E., "Amorphous mesoporous silica-alumina with controlled pore size as acid catalysts" (1994), Studies in Surface Science and Catalysis, vol. 84, pag. 85-92. Commercial silico- aluminas can also be used, such as, for example Siral 1, Siral 5, Siral 20, Siral 30, Siral 40. The process of the present invention can be carried out either batchwise or in continuous. When it is carried out batchwise, the reaction step between said cyclic acetal having formula (III) and said etherified 1,2-diol having formula (IV) and/or said etherified 1,3-diol having formula (V), can be carried out for a time ranging from 30 minutes to 180 minutes and is preferably carried out for a time ranging from 30 to 60 minutes .

When the process of the present invention is carried out in continuous, the space velocity LHSV (Liquid Hourly Space Velocity) of the reaction mixture on the catalyst preferably ranges from 0.1 to 20 hf 1 and more preferably from 1 to 10 hf 1 . In a particularly preferred aspect, the space velocity ranges from 2 to 8 h "1 .

The process of the present invention can be carried out using conventional equipment known to skilled person in the art.

In a preferred aspect, the process of the present invention can be carried out in at least one fixed bed reactor filled with acid catalyst (for example, a fixed bed of an acid resin) .

In a preferred aspect, said process can be carried out in at least one fixed bed reactor with recycling of the unconverted reagents in continuous.

In this case, due to the desired low conversion of the reagents with the aim of reducing the formation of by-products, the recycling ratio can be within the range of 10 to 25, and preferably within the range of 15 to 20. The reaction can be carried out with other reaction systems, such as, for example, a CSTR reactor (Continuous Stirred-Tank Reactor) or an ebullated bed reactor .

When carried out under the conditions indicated above, the process according to the invention, both when the cyclic acetal having formula (III) is reacted with an etherified 1,2-diol, and also when said cyclic acetal having formula (III) is reacted with an etherified 1,3-diol, is characterized by conversions per step preferably greater than 75 mol.% and preferably ranging from 75 mol.% to 85 mol.%, with a selectivity towards the reaction products, i.e. the cyclic acetal having formula (I) or the cyclic acetal having formula (II), preferably more than 95 mol.%.

In a preferred aspect of the invention, the cyclic acetal having formula (III) is 2-ethyl-4-methyl-l , 3- dioxolane :

In this case, the process according to the present invention can lead to the production of etherified cyclic acetals having formula (Ι') and/or (II' ) :

wherein R' and R" have the meanings previously described .

In a preferred aspect of the invention, a particular cyclic acetal having formula (VII), comprised within the cyclic acetals of formula (III), can be obtained by means of a process comprising the following steps:

a) providing a reaction mixture comprising at least one 1,2-diol having formula (VI) :

Ri-CH 2 -CHOH-CH 2 OH (VI)

said mixture being substantially free of aldehydes; subjecting said reaction mixture to heat treatment at a temperature ranging from 100°C to 300°C in the presence of an acid catalyst, thus obtaining said cyclic acetal having formula (VII) .

o

wherein Ri can be selected from H and an alkyl having from 1 to 5 carbon atoms, preferably H.

A preferred embodiment of the present invention therefore relates to a process for the preparation of at least one cyclic acetal having general formula (VIII) and/or (IX) :

(VIII) (IX)

wherein Ri can be selected from H and an alkyl having from 1 to 5 carbon atoms, preferably H, and R' and R", the same or different, can be an alkyl having from 1 to 6 carbon atoms, which comprises the following steps: a) providing a reaction mixture comprising at least one 1,2-diol having formula (VI) :

Ri-CH 2 -CHOH-CH 2 OH (VI),

wherein Ri can be selected from H and an alkyl having from 1 to 5 carbon atoms, preferably H, said mixture being substantially free of aldehydes;

b) subjecting said reaction mixture to heat treatment at a temperature ranging from 100°C to 300°C in the presence of an acid catalyst, thus obtaining a cyclic acetal having formula (VII) :

(VII)

wherein Ri has the meanings described above;

c) reacting, at a temperature ranging from 30°C to 150°C, in the presence of an acid catalyst, said cyclic acetal having formula (VII) with at least one etherified 1,2-diol having formula (IV) : CH 2 OH-CHOH-CH 2 OR' (IV),

wherein R' has the meanings described above, obtaining the cyclic acetal having formula (VIII), and/or with at least one etherified 1,3-diol having formula (V) :

CH 2 OH-CHOR"-CH 2 OH (V) ,

wherein R" has the meanings described above, obtaining the cyclic acetal having formula (IX) . In a preferred aspect of the invention, the cyclic acetal having formula (VII) can also be obtained by means of a process comprising the following steps:

a') providing a reaction mixture comprising at least one 1,2-diol having formula (VI) :

R 1 - CH2-CHOH- CH2OH (VI),

wherein R is selected from H and an alkyl having from 1 to 5 carbon atoms, preferably hydrogen, and at least one etherified 1,2-diol having formula (IV) :

CH2OH-CHOH- CH2OR ' (IV)

wherein R' is an alkyl having from 1 to 6 carbon atoms, said mixture being substantially free of aldehydes ;

b') subjecting said reaction mixture to heat treatment at a temperature ranging from 100°C to 300°C in the presence of an acid catalyst, thus obtaining a mixture comprising the cyclic acetal having formula (VII) and the etherified cyclic acetal having formula (VIII) :

(VII) (VIII)

wherein Ri and R' have the meanings described above; c' ) separating the cyclic acetal having formula (VII) from said mixture obtained in step b' ) , preferably by means of distillation.

A further preferred embodiment of the present invention therefore relates to a process for the preparation of at least one cyclic acetal having general formula (VIII) and/or (IX :

(VIII) (IX)

wherein Ri can be selected from H and an alkyl having from 1 to 5 carbon atoms and R' and R", the same or different, can be an alkyl having from 1 to 6 carbon atoms, which comprises the following steps:

a' ) providing a reaction mixture comprising at least one 1,2-diol having formula (VI) :

Ri-CH 2 -CHOH-CH 2 OH (VI) ,

wherein Ri is selected from H and an alkyl having from 1 to 5 carbon atoms, and at least one etherified 1,2-diol having formula (IV) :

CH 2 OH-CHOH-CH 2 OR' (IV) wherein R' can be an alkyl having from 1 to 6 carbon atoms, said mixture being substantially free of aldehydes;

b' ) subjecting said reaction mixture to heat treatment at a temperature ranging from 100°C to 300°C in the presence of an acid catalyst, obtaining a mixture comprising the cyclic acetal having formula (VII) and the etherified cyclic acetal having formula (I) :

(VII) (VIII)

wherein Ri and R' have the meanings described above; c' ) separating the cyclic acetal having formula (VII) from said mixture obtained in step b' ) , preferably by means of distillation;

d' ) reacting, at a temperature ranging from 30°C to

150°C, in the presence of an acid catalyst, said separated cyclic acetal having formula (VII) with at least one etherified 1,2-diol having formula

(IV) :

CH 2 OH-CHOH-CH 2 OR' (IV),

wherein R' independently has the meanings described above, obtaining the cyclic acetal having formula (VIII), and/or with at least one etherified 1,3- diol having formula (V) :

CH 2 OH-CHOR"-CH 2 OH (V) ,

wherein R" has the meanings described above, obtaining the cyclic acetal having formula (IX) .

The 1,2-diol having formula (VI) and the etherified 1,2-diol having formula (IV) are preferably present in the mixture of step a' ) in a molar ratio ranging from 0.5 to 12, more preferably in a molar ratio ranging from 2 to 10.

According to this preferred aspect of the invention, the etherified cyclic acetal having formula (VIII) and the cyclic acetal having formula (VII), which represents the starting compound of a preferred embodiment of the process according to the invention, can be obtained directly. The presence of the ethereal function on one of the products causes the two compounds obtained to be characterized by boiling points sufficiently different from each other, thus making the isolation and purification of the single products by means of distillation particularly easy. Consequently, the cyclic acetal having formula (VII), after separation (preferably by means of distillation) , can then be reacted with an etherified 1,2-diol having formula (IV) and/or with an etherified 1,3-diol having formula (V) to respectively produce the etherified cyclic acetal having a 1 , 3-dioxolane structure having formula (VIII) and/or the etherified cyclic acetal having a 1, 3-dioxane structure having formula (IX) .

According to these preferred aspects of the invention, in steps a) or a' ) , a reaction mixture is prepared comprising a 1,2-diol having formula (VI), possibly also comprising an etherified 1,2-diol having formula (IV), wherein said mixture is substantially free of aldehydes, and in general substantially free of any carbonyl compound, with which said diols can form an acetal, and in general a condensation adduct similar to the cyclic acetal having formula (III) .

Preferably, when the cyclic acetal having formula (VII) is obtained by heat treatment, in the presence of an acid catalyst, of a mixture comprising at least one 1,2-diol having formula (VI), and optionally also comprising at least one etherified 1,2-diol having formula (IV), said 1,2-diol having formula (VI) is selected in the group consisting of 1 , 2-propanediol , 1 , 2-butanediol , 1 , 2-pentadiol , 1 , 2-hexanediol , 1,2- heptanediol, 1 , 2-octanediol and mixtures thereof and more preferably it is selected from 1 , 2-propanediol , 1 , 2-butanediol and 1 , 2-pentanediol and mixtures thereof.

When the 1,2-diol having formula (VI) is 1,2- propanediol, it is preferably obtained by means of a catalytic hydrogenation process of glycerol with hydrogen, according to conventional methods known to skilled persons in the field.

Examples of catalysts that can be used in the catalytic hydrogenation process of glycerol are: copper chromite, mixed oxides of chromium-zinc-copper, carbon- supported noble metals, noble metals supported on iron oxide, preferably palladium on carbon, platinum on carbon, palladium on iron oxide and mixtures thereof.

Said glycerol is preferably obtained as by-product of transesterification or hydrolysis reactions of triglycerides of a biological origin, for example reactions used in production processes of biodiesel.

In a preferred embodiment of the present invention, when the 1,2-diol having formula (VI) is 1,2- propanediol, the cyclic acetal having formula (VII) obtained by heat treatment in the presence of an acid catalyst in steps b) or b' ) described above, is 2- ethyl-4-methyl-l , 3-dioxolane .

Preferably, when the cyclic acetal having formula (VII) is obtained by heat treatment, in the presence of an acid catalyst, of a mixture comprising at least one 1,2-diol having formula (VI), and optionally also comprising at least one etherified 1,2-diol having formula (IV), said heat treatment of steps b) or b' ) is carried out at a temperature ranging from 100°C to 300°C and preferably from 110°C to 200°C. In a particularly preferred aspect, said heat treatment is carried out at a temperature ranging from 115°C to 150°C.

Said heat treatment of steps b) or b' ) is preferably effected keeping the reaction mixture in liquid phase. For this purpose, the above-mentioned heat treatment can be carried out keeping the reaction mixture at a pressure ranging from 0.5 MPa to 5 MPa and preferably at a pressure ranging from 1 MPa to 4 MPa.

Preferably, when the cyclic acetal having formula (VII) is obtained by heat treatment, in the presence of an acid catalyst, of a mixture comprising at least one 1,2-diol having formula (VI), and optionally also comprising at least one etherified 1,2-diol having formula (IV), said acid catalyst can be selected from the acid catalysts previously described.

Said heat treatment can be carried out batchwise or in continuous, preferably is carried out in continuous. The space velocity (Liquid Hourly Space Velocity - LHSV) of the reaction mixture on the catalyst preferably ranges from 0.1 to 20 hf 1 and more preferably ranges from 1 to 12 hf 1 . In a particularly preferred aspect, the space velocity ranges from 2 to 8 hf 1 .

The heat treatment of steps b) or b' ) in the presence of an acid catalyst is preferably carried out in at least one fixed bed catalyst reactor.

In a preferred aspect, said process can be carried out in at least one fixed bed reactor with recycling of the unconverted reagents in continuous.

The recycling ratio can be within the range of 10 to 25, and preferably within the range of 15 to 20.

The reaction can be carried out with other reaction systems, such as, for example, a CSTR reactor (Continuous Stirred-Tank Reactor) or an ebullated bed reactor .

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

Example 1 (Synthesis of 2-ethyl-4-ethoxymethyl-l , 3- dioxolane from 2-ethyl-4-methyl-l , 3-dioxolane batchwise in an autoclave)

6 g of acid catalyst Amberlyst A-36 (Dow Chemical) were charged into a 90 ml autoclave and 60 mL of a mixture consisting of 40% by weight of 2-ethyl-4- methyl-1 , 3-dioxolane (purity 88% by weight) and 60% of 3-ethoxy-l , 2-propanediol (purity 99.3% by weight) were added .

The temperature was brought to 40°C, a pressure of

4 MPa was applied, and the mixture was kept under these conditions under stirring for 30 minutes.

At the end of this period, the product obtained was analyzed: the molar conversion of 2-ethyl-4-methyl-l , 3- dioxolane is equal to 52 mol.% and the molar selectivity to the desired product, 2-ethyl-4- ethoxymethyl-1 , 3-dioxolane, is about 98 mol.%.

The product obtained was separated from the unreacted components and from the reaction co-product 1 , 2-propanediol by means of distillation.

Example 2 (Synthesis of 2-ethyl-4-ethoxymethyl-l , 3- dioxolane from 2-ethyl-4-methyl-l , 3-dioxolane in continuous in a fixed bed reactor in "once-through" mode )

60 cm 3 (about 46 g) of acid catalyst Amberlyst A-36 (Dow Chemical) were charged into a fixed bed reactor having a length of 100 cm and an internal diameter of 1 cm.

After bringing the temperature of the reactor to 55°C, a mixture was fed, consisting of 20% by weight of 2-ethyl-4-methyl-l , 3-dioxolane (purity 88% by weight) and 80% of 3-ethoxy-l , 2-propanediol (purity 99.3% by weight) .

The feeding of the mixture is effected at a space velocity of 4 h _1 .

The reaction mixture is kept in liquid phase, applying a counterpressure of 4 MPa to the reactor.

During the reaction, samples of the mixture of products leaving the reactor are taken and analyzed by means of gas chromatography.

The gas chromatographic analysis confirmed a molar conversion per step of 2-ethyl-4-methyl-l , 3-dioxolane equal to 72 mol.%. The molar selectivity to the desired product, 2-ethyl-4-ethoxymethyl-l , 3-dioxolane, is about 89 mol.%.

Example 3 (Synthesis of 2-ethyl-4-ethoxymethyl-l , 3- dioxolane from 2-ethyl-4-methyl-l , 3-dioxolane in continuous in a fixed bed reactor with recycling)

60 cm 3 (about 46 g) of acid catalyst Amberlyst A-36 (Dow Chemical) were charged into a fixed bed reactor having a length equal to 100 cm and an internal diameter of 1 cm.

After bringing the temperature of the reactor to 55°C, a "make-up" mixture was fed, consisting of 60% by weight of 2-ethyl-4-methyl-l , 3-dioxolane (purity 88% by weight) and 40% of 3-ethoxy-l , 2-propanediol (purity 99.3% by weight), with which a portion of the mixture of products is premixed, which is then recycled to the feeding. This causes the reaction mixture to modify its composition, when under regime conditions, so that the 2-ethyl-4-methyl-l , 3-dioxolane passes from 60% by weight to 20% by weight with respect to the total weight of the mixture and the 3-ethoxy-l , 2-propanediol passes from 40% by weight to 80% by weight with respect to the total weight of the same mixture.

The feeding of the mixture is effected at a space velocity of 2 h _1 .

The reaction was carried out in continuous, for about 116 hours.

The reaction mixture is kept in liquid phase, applying a counterpressure of 4 MPa to the reactor.

During the reaction, samples of the mixture of products leaving the reactor are taken and analysed by means of gas chromatography.

The gas chromatographic analysis confirmed a molar conversion per step of 2-ethyl-4-methyl-l , 3-dioxolane equal to 67.2 mol.%. The molar selectivity to the desired product, 2-ethyl-4-ethoxymethyl-l , 3-dioxolane, is equal to 100%.

The catalyst is stable under the reaction conditions for over 880 hours, showing no variations in either the conversion or the selectivity towards the desired product during this time interval.

The 2-ethyl-4-ethoxymethyl-l , 3-dioxolane obtained was separated from the reaction mixture by distillation .

Example 4 (Synthesis of 2-ethyl-4-ethoxymethyl-l , 3- dioxolane from 1 , 2-propanediol and 3-ethoxy-l , 2- propanediol )

60 cm 3 (about 46 g) of acid catalyst Amberlyst A-36 (Dow Chemical) were charged into a fixed bed reactor having a length equal to 100 cm and an internal diameter of 1 cm.

After bringing the temperature of the reactor to 115°C, a mixture was fed, consisting of 86% by weight of pure 1 , 2-propanediol and 14% of 3-ethoxy-l , 2- propanediol (purity 99.3% by weight) .

The feeding of the mixture is effected at a space velocity of 6 h _1 .

The reaction mixture is kept in liquid phase, applying a counterpressure of 4 MPa to the reactor.

During the reaction, samples of the mixture of products leaving the reactor are taken and analyzed by means of gas chromatography. The composition of the mixture of products distilled from the reactor effluent is composed of an upper organic phase (70% by weight) and a lower aqueous phase (30% by weight, with respect to the total weight of the mixture of products) . The lower aqueous phase substantially consists of the stoichiometric reaction water and entrained 1 , 2-propanediol . The organic phase mainly comprises 2-ethyl-4-methyl-l , 3-dioxolane (73% by weight, with respect to the total weight of the mixture of products) and 2-ethyl-4-ethoxymethyl-l , 3-dioxolane (20% by weight, with respect to the total weight of the mixture) , the complement to 100% consisting of reaction by-products and water.

Gas chromatographic analysis confirmed a molar conversion per step of 1 , 2-propanediol equal to 4 mol.% and the molar conversion per step of the limiting agent 3-ethoxy-l , 2-propanediol also proved to be equal to 4 mol.%. The molar selectivity to the desired products (2-ethyl-4-methyl-l, 3-dioxolane + 2-ethyl-4-ethoxy- methyl-1, 3-dioxolane) is equal to about 84.5 mol.%.

The separation of the two main reaction products was effected by distillation under reduced pressure conditions (2 kPa) .

The 2-ethyl-4-methyl-l , 3-dioxolane was used for producing further 2-ethyl-4-ethoxy-methyl-l , 3- dioxolane, under the conditions described in Example 1.

Finally, it is understood that further modifications and variations can be made to the process described and illustrated herein, that are included within the scope of the appended claims.