Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D317/00—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms
  • C07D317/08—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3
  • C07D317/10—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings
  • C07D317/14—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings with substituted hydrocarbon radicals attached to ring carbon atoms
  • C07D317/18—Radicals substituted by singly bound oxygen or sulfur atoms
  • C07D317/22—Radicals substituted by singly bound oxygen or sulfur atoms etherified
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D317/00—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms
  • C07D317/08—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3
  • C07D317/10—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings
  • C07D317/32—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
  • C07D317/34—Oxygen atoms
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/582—Recycling of unreacted starting or intermediate materials

Definitions

• the present invention falls within the field of fuel components.
• the present invention relates to a process for preparing cyclic acetals that can be used as components for diesel fuel.
• 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.
• 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 .
• 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 impose, within a strict time limits, the ever-expanding use of these biofuels, in particular in the field of automotive fuels.
• 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.
• 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 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.
• triglycerides triesters of glycerol with long-alkyl- chain fatty acids
• 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.
• 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.
• the addition of FAMEs to gasoil reduces its cold performance and increases the emission of NO x by combustion.
• 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 .
• 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 .
• 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
• 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 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.
• 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.
• 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) .
• step (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 .
• step (2) provides the use of a pure carbonyl compound, in step (2), selected from aldehydes and ketones, previously synthetized and isolated.
• 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 .
• the above process comprises the following steps:
• 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,
• reaction mixture 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.
• 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.
• 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 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.
• 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.
• 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.
• 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)
• 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.
• 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.
• molecule with a 1 , 3-dioxolane structure refers to any cyclic molecule comprising the 1 , 3-dioxolane nucleus.
• molecule with a 1,3-dioxane structure refers to any cyclic molecule comprising the 1,3-dioxane nucleus.
• 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 .
• 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) :
• reaction mixture comprising a cyclic acetal having formula (III) :
• 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.
• 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.
• 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.
• 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) .
• 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 .
• R is CH 3 and R'" is H.
• the cyclic acetal having formula (III) is 2-ethyl-4-methyl-l , 3- dioxolane.
• R and R'" in the acetal of formula (III) are equal to each other and in particular they are both hydrogen .
• 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 .
• R' is C 3 H 7 .
• R is preferably H or CH 3 and R' is C 3 H 7 .
• the cyclic acetal having formula (I) is 2- ethyl-4-propoxymethyl-l , 3-dioxolane .
• R' is C 2 H 5 .
• R is preferably H or CH 3 and R' is C 2 H 5 .
• the cyclic acetal having formula (I) is 2- ethyl-4-ethoxymethyl-l , 3-dioxolane .
• R' is CH 3 .
• R is preferably H or CH 3 and R' is CH 3 .
• the cyclic acetal having formula (I) is 2- ethyl-4-methoxymethyl-l , 3-dioxolane .
• 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 .
• R" is n-C 3 H 7 .
• R is preferably H or CH 3 and R" is n-C 3 H 7 .
• the cyclic acetal having formula (II) is 2-ethyl-5-propoxy-l , 3-dioxane .
• R" is C 2 H 5 .
• R is preferably H or CH 3 and R" is C 2 H 5 .
• the cyclic acetal having formula (II) is 2- ethyl-5-ethoxy-l , 3-dioxane .
• R" is CH 3 .
• R is preferably H or C3 ⁇ 4 and R" is C3 ⁇ 4.
• the cyclic acetal having formula (II) is 2- ethyl-5-methoxy-l , 3-dioxane .
• 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 .
• 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:
• 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.
• 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) :
• 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) :
• 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.
• 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.
• the etherified 1,2-diol having formula (IV) is 3-methoxy-l , 2- propanediol .
• the etherified 1,2-diol having formula (IV) is 3-ethoxy- 1 , 2-propanediol .
• the etherified 1,2-diol having formula (IV) is 3-propoxy- 1 , 2-propanediol .
• 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.
• the etherified 1,3-diol having formula (V) is 2-methoxy-l , 3- propanediol .
• the etherified 1,3-diol having formula (V) is 2-ethoxy-l , 3- propanediol .
• the etherified 1,3-diol having formula (V) is 2-propoxy- 1 , 3-propanediol .
• 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.
• 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.
• 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)
• 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.
• 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) .
• 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.
• 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) .
• 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.
• 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.
• 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.
• 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 .
• the space velocity LHSV Liquid Hourly Space Velocity
• the space velocity ranges from 0.1 to 20 hf 1 and more preferably from 1 to 10 hf 1 .
• the space velocity ranges from 2 to 8 h "1 .
• 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) .
• 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 .
• 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.%.
• the cyclic acetal having formula (III) is 2-ethyl-4-methyl-l , 3- dioxolane :
• the process according to the present invention can lead to the production of etherified cyclic acetals having formula ( ⁇ ') and/or (II' ) :
• R' and R" have the meanings previously described .
• 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:
• 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) .
• 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) :
• 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 can be selected from H and an alkyl having from 1 to 5 carbon atoms, preferably H, said mixture being substantially free of aldehydes;
• 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) :
• the cyclic acetal having formula (VII) can also be obtained by means of a process comprising the following steps:
• 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) :
• R' is an alkyl having from 1 to 6 carbon atoms, said mixture being substantially free of aldehydes ;
• 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 :
• 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:
• 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) :
• R' can be an alkyl having from 1 to 6 carbon atoms, said mixture being substantially free of aldehydes;
• 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) :
• 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.
• 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.
• 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) .
• a reaction mixture 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) .
• 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.
• 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.
• 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.
• 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 .
• the 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.
• 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.
• 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.
• 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.
• 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 .
• steps b) or b' ) in the presence of an acid catalyst is preferably carried out in at least one fixed bed catalyst reactor.
• 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 .
• CSTR reactor Continuous Stirred-Tank Reactor
• ebullated bed reactor ebullated bed reactor
• the temperature was brought to 40°C, a pressure of
• 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.
• 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.
• 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.%.
• 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.
• 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.
• 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 .
• 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.
• 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.
• 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.

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