RIZZO CATERINA (IT)
ASSANELLI GIULIO (IT)
| EP0638541A1 | 1995-02-15 | |||
| EP0638541A1 | 1995-02-15 | |||
| US6031122A | 2000-02-29 | |||
| EP0625519A1 | 1994-11-23 |
WATANABE Y ET AL: "Hydrotalcite-type materials as catalysts for the synthesis of dimethyl carbonate from ethylene carbonate and methanol", MICROPOROUS AND MESOPOROUS MATERIALS, ELSEVIER SCIENCE PUBLISHING, NEW YORK, US, vol. 22, no. 1-3, 17 June 1998 (1998-06-17), pages 399 - 407, XP004128332, ISSN: 1387-1811, DOI: 10.1016/S1387-1811(98)00099-7
MURUGAN, C. ET AL: "Transesterification of propylene carbonate with methanol using Mg-Al-CO3 hydrotalcite as solid base catalyst", INDIAN JOURNAL OF CHEMISTRY, SECTION A: INORGANIC, BIO-INORGANIC, PHYSICAL, THEORETICAL & ANALYTICAL CHEMISTRY , 49A(9), 1182-1188 CODEN: ICACEC; ISSN: 0376-4710, September 2010 (2010-09-01), XP008151759
DATABASE CA [online] CHEMICAL ABSTRACTS SERVICE, COLUMBUS, OHIO, US; SHU, TING ET AL: "Synthesis of propylene carbonate from urea and 1,2-propanediol catalyzed by hydrotalcite -like compounds", XP002675711, retrieved from STN Database accession no. 2006:138999
XIANMEI XIE ET AL: "Synthesis of Propylene Carbonate Catalyzed by Copper-containing Hydrotalcite-like Compounds", MRS PROCEEDINGS, vol. 1279, 2010, XP055026714, ISSN: 0272-9172, DOI: 10.1557/PROC-1279-24
| CLAIMS A process for the preparation of dialkyl carbonates compounds starting from urea and from reagents selected from ethylene glycol, propylene glycol and linear alcohols having a number of carbon atoms comprised from 1 and 20, said process comprising the steps: ■ carrying out a glycolysis reaction, in the presence of a first catalyst in heterogeneous phase, between urea and a reagent selected from ethylene glycol, propylene glycol and linear alcohols with a number of carbon atoms in the chain comprised from 1 and 20, so as to form an alkenyl carbonate; ■ carrying out a transesterification reaction, in the presence of a second catalyst in heterogeneous phase, between .the alkenyl carbonate so obtained and an aliphatic alcohol having a number of carbon atoms comprised in the range 1-22, so as to form the dialkyl carbonates compounds . The process according to claim 1 wherein the catalyst in the step (a) is a hydrotalcite of formula : M^aM11^ (OH) 16X ·ηΗ20 (I) wherein M11 is a bivalent metal selected from Mg, Fe11, Ni11, Zn, Cd, Co11 and mixture thereof; M is a trivalent metal selected from Al, Fe111, Ga111, Cr111, Mn111, Co111 and mixture thereof, X is an anion selected from C032 , OH~ and NO3", n is an integer number comprised from 0 and 6, a is an integer number comprised from 4 and 6. The process according to claim 1 wherein the catalyst in the step (b) is an hydrotalcite of formula : wherein M11 is a bivalent metal selected from: Mg, Fe11, Ni11, Zn, Cd, CoI]:and mixture thereof; M111 is a trivalent metal selected from Al, Fe111, Ga111, Cr111, Mn111, Co111 and mixture thereof, and X is an anion comprised from C032~ , OH" and N03" . The process according to claim 2 wherein M11 is magnesium or zinc and M111 is aluminium. The process according to claim 4 wherein "a" is 6 and the anion X is C032~ N03" or OH. The process according to claim 3 wherein M11 is zinc or magnesium, or mixture of the two, and M111 is selected from Al, Fe and Cr. The process according to claim 6 wherein M111 is Al. The process according to claim 3 wherein M11 is zinc or magnesium and M111 is selected from Al, Fe and Cr, "a" is 6 and X is C03~. The process according to claims 1-8 wherein the aliphatic alcohol is of biologic origin and has a number of carbon atoms up to 22. 10. The process according to claim 9 wherein the aliphatic alcohol has a number of carbon atoms comprised from 1 to 6. 11. The process according to claims 1-8 wherein the aliphatic alcohol is ethanol or butanol . 12. The process according to claims 1-11 wherein the step (a) of the process is carried out at temperatures comprised from 100°C and 150°C and pressures comprised from 2 atm and 0.01 atm. 13. The process according to claims 1-11 wherein the step (b) of the process is carried out at temperatures comprised from 80°C and 130°C, with pressures comprised from 1 atm and 15 atm. 14. The process according to claims 1-11 wherein the aliphatic alcohol is in excess with respect of the stoichiometric with molar ratios alcohol/ (alkenil carbonates) comprised from 2.5/1 and 10/1. |
The present invention relates to a process for the preparation of dialkyl carbonate compounds which can be advantageously used as additives of a biological origin in fuels such as diesel or gasolines.
The legislation in force, and even more so in the years to come, envisages that a part of the fuels used, such as diesel and gasoline, contain a component of a biological origin. Dialkyl carbonates, and in particular diethyl carbonate, can be used as additives for said fuels, increasing the aliquot of product of a biological origin in the fuel and thus reducing the particulate.
The synthesis of diethyl carbonate is described in the Mistubishi patents EP 0638541, US 6,031,122 and EP 0625519, wherein urea reacts directly with ethanol, using a catalyst in homogeneous phase (catalysts based on metal oxides, in particular ZnO, and acetates), at a temperature ranging from 150°C to 190°C. The yields obtained are lower than 80% as main by-product in the relative carbamate, which is a toxic and highly carcinogenic substance. Triazines, which are also toxic and mutagenic, are also obtained as further by- products.
The Applicant has now found a new method for the preparation of dialkyl carbonate compounds, using a heterogeneous catalyst based on hydrotalcite , obtaining extremely high product yields, higher than 95% molar, at the same time avoiding the formation of toxic and carcinogenic by-products.
The present invention therefore relates to a process for the preparation of dialkyl carbonate compounds starting from urea and reagents selected from ethylene glycol, propylene glycol and linear alcohols having a number of carbon atoms ranging from 1 to 20. Said process comprises the following steps:
• carrying out a glycolysis reaction, in the presence of a first catalyst in heterogeneous phase based on hydrotalcite , between urea and a reagent selected from ethylene glycol, propylene glycol and .linear alcohols with a number of carbon atoms in the chain ranging from 1 to 20, so as to form an alkenyl carbonate ;
• carrying out a transesterification reaction, in the presence of a second catalyst in heterogeneous phase based on hydrotalcite, between the alkenyl carbonate thus obtained and an aliphatic alcohol having a number of carbon atoms within the range of 1-22, so as to form dialkyl carbonate compounds.
The use of a catalyst in heterogeneous phase allows the end-product to be easily separated without additional costs contrary to what occurs with processes of the known art which use catalysts in homogeneous phase .
The use of a catalyst in heterogeneous phase also allows an end-product to be obtained, in which metals dissolved in a significant quantity are not present. Detailed description
An object of the present invention .therefore relates to a process for the preparation of dialkyl carbonate compounds starting from urea and reagents selected from ethylene glycol, propylene glycol and linear alcohols having a number of carbon atoms ranging from 1 to 20. Said process comprises two steps:
• carrying out a glycolysis reaction, in the presence of a first catalyst in heterogeneous phase, between urea and a reagent selected from ethylene glycol, propylene glycol and linear alcohols with a number of carbon atoms in the chain ranging from 1 to 20, preferably ethylene glycol, so as to form an alkenyl carbonate;
• carrying out a transesterification reaction, in the presence of a second catalyst in heterogeneous phase, between the alkenyl carbonate thus obtained and an aliphatic alcohol having a number of carbon atoms within the range of 1-22, preferably within the range of 1-6, even more preferably ethyl or butyl alcohol, so as to form dialkyl carbonate compounds .
The intermediate products formed in step (a) are, for example, ethylene carbonate or propylene carbonate.
The end-products obtained with the process, object of the present invention, are dialkyl carbonates. Preferred products are diethyl carbonate and dibutyl carbonate.
The use of the end-products, dialkyl carbonates, (obtained with the process of the present invention) as additives for diesel or gasolines, has various advantages .
The linear alcohols having a number of carbon atoms ranging from 1 to 20 can preferably be of biological origin and even more preferably can be obtained starting from fatty acids with a number of carbon atoms in the chain ranging from 16 to 22.
First of all, the use of a biological component obtained via fermentation as additive in diesel fuel represents an alternative to biocomponents obtained from vegetable oils (FAME or Fatty Acid Methyl Ester, HVO or Hydrogenated Vegetable Oil) . Secondly, the possibility of using alcohols in the formulation of fuels for diesel (such as Diethyl carbonate DEC), allows the imbalance currently existing in Europe between the demand and offer profile of gasoline/diesel fuel, to be partially rebalanced.
The end-products obtained with the process, object of the present invention, can be used as biological component in both gasoline and diesel fuel, allowing a saving of hydrogen in the refinery, which on the other hand, is required for the production of other fuels of a biological nature such as HVO.
Finally, the synthesis process from urea for the production of dialkyl carbonates uses C0 2 for the production of urea, with the consequent recovery of aliquots of CO 2 according to the Kioto protocol.
The catalysts used in the process, object of the present invention, in both steps, are in heterogeneous phase, preferably in solid phase.
The catalyst used in step (a) of the process described and claimed in the present text, can be any hydrotalcite having the formula:
M^ a M 11 ^ (OH) 16 X ·ηΗ 2 0 (I) wherein M 11 is a bivalent metal selected from Mg, Fe 11 , Ni 11 , Zn, Cd, Co 11 and mixture thereof; M 111 is a trivalent metal selected from Al, Fe 111 , Ga 111 , Cr 111 , Mn 111 , Co 111 and mixtures thereof, X is an anion selected from CC>3 2~ , OH ~ and NO 3 "" , n is an integer ranging from 0 to 6, a is an integer ranging from 4 to 6.
Hydrotalcites in which M 11 is magnesium or zinc and 1 11 is aluminium, iron or chromium are preferred; among these, hydrotalcites even more preferred are those in which "a" is 6 and the anion X is C0 3 2" , N0 3 " or OH.
The reaction step (a) is carried out at temperatures ranging from 100°C to 150°C and pressures ranging from 2 atm to 0.01 atm. The reaction is preferably carried out at a pressure lower than atmospheric pressure and even more preferably at pressures ranging from 0.05 atm to 0.01 atm.
Under these conditions, the conversion of the limiting agent (urea) is total and the selectivity to the desired product >95% molar.
The aliphatic alcohol is preferably of a biological origin, in the text indicated as bioalcohol, and can be obtained either by fermentation of a biomass or molasses, or by the reduction of a fatty acid, acids that normally have an extremely high number of carbon atoms, for example up to 22 carbon atoms. The aliphatic alcohol of a biological origin may preferably have up to 22 carbon atoms in the chain and more preferably the aliphatic alcohol obtained can have from 1 to 6 carbon atoms. Among these aliphatic alcohols ethanol and butanol are particularly preferred.
The catalyst used in step (b) of the process described and claimed in the present text, can be a hydrotalcite having the formula:
M II 6M III 2 (OH) ΐβΧ ·η¾0 (II) wherein M 11 is a bivalent metal selected from: Mg, Fe 11 , Ni 11 , Zn, Cd, Co 11 and mixtures thereof.; M 111 is a trivalent metal selected from Al, Fe 111 , Ga 111 , Cr 111 , Mn 111 , Co 111 and mixtures thereof, and X is an anion selected from C0 3 2~ , OH " and N0 3 " .
Particularly preferred are hydrotalcites wherein M 11 is Zn or Mg, or mixtures of the two, and M 111 is selected from Al, Fe and Cr, M 111 is more preferably Al . Hydrotalcites wherein M 11 is Zn or Mg and M 111 is selected from Al, Fe and Cr, "a" is 6 and X is CO 3 " , are more preferred.
The reaction step (b) is carried out at temperatures ranging from 80°C to 130°C, with pressures ranging from 1 atm to 15 atm. The reaction step (b) is carried out using alcohol in excess with respect to the stoichiometric with molar ratios alcohol/ (alkenyl carbonate) ranging from 2.5/1 to 10/1, more preferably from 4/1 to 8/1. The reaction reaches thermodynamic equilibrium with a quantitative selectivity to dialkyl carbonate .
The catalysts of step (a) and step (b) can be preferably the same, but can also have a different chemical composition. When the catalyst is the same in both steps, then M 11 is preferably Zn and M 111 is Al .
In the end-product, obtained with the process described and claimed above, there are no metals dissolved in a significant quantity due to the fact that the catalyst used in both steps is in heterogeneous form, and is preferably a solid. In particular, metals such as Zn, Mg and Cu are present in a quantity lower than 0.05 ppm.
This factor is extremely important as the presence of metals in the end-product causes fouling in the fuel injectors, in particular in common rail diesel engines.
The same products obtained with the processes of the known art, on the other hand, have a much higher metal content, and in the order of percent as the catalyst used (for example ZnO) is partially soluble in the reaction mixture. Consequently the dialkyl carbonates obtained with the conventional processes cannot be used as additives for diesel or gasolines, as only one ppm of Zn is sufficient in the diesel for significantly fouling the injectors.
Example 1
Step (a) of the synthesis of diethylene carbonate with hydrotalcite Zn-Al-N0 3 .
Urea and ethylene glycol are charged into a glass reactor in a molar ratio of 1/1.2 and the hydrotalcite ΖηεΑΐ2 (OH) 16 O 3 ·ηΗ 2 0, synthesized by the Applicant, is added in a ratio of 5% by weight; the reaction mixture is heated to 130°C and a vacuum is applied reducing the pressure to 30 mbar. After 3 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography . The conversion of urea proves to be total with a selectivity to the desired product (ethylene carbonate) equal to 95%. The by- products consist of oxazolidone (3%) and the corresponding hydroxycarbonate (2%) .
Example 2
Step (b) of the synthesis of diethylene carbonate with hydrotalcite Zn-Al-NQ 3 .
Ethylene carbonate, produced according to Example
1, and ethanol are charged into a glass reactor in a molar ratio of 1/4; the hydrotalcite
Zn 6 Al2 (OH) i 6 N0 3 ·ηΗ 2 0, synthesized by the Applicant, is then added in a ratio of 5% by weight; the reaction mixture is heated to 83°C and is sent to reflux for 3 hours. After 3 hours, the reaction is interrupted and the reaction product is analyzed by means of ■ gaschromatography. The conversion of ethylene carbonate proves to be equal to 80% (thermodynamic limit of the transesterification reaction) with a selectivity to the desired product (diethyl carbonate) higher than 99%. N ' o significant quantities of by-products are- observed. A quantitative analysis on the reaction product thus obtained excludes the presence of metals (Zn, g) up to the analytical limit analyzable (0.5 ppm) .
Example 3
Step (a) of the synthesis of diethylene carbonate with hydrotalcite Zn-Al-C0 3 .
Urea and ethylene glycol are charged into a glass reactor in a molar ratio of 1/1.2 and the hydrotalcite Zn 6 Al 2 (OH) 16CO3 ■ 6¾0, synthesized by the Applicant, is added in a ratio of 5% by weight; the reaction mixture is heated to 130°C and a vacuum is applied reducing the pressure to 30 mbar. After 3 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography . The conversion of urea proves to be total with a selectivity to the desired product (ethylene carbonate) equal to 96%. The by- products consist of oxazolidone (3%) and the corresponding hydroxycarbonate (1%) .
Example 4
Step (b) of the synthesis of diethylene carbonate with hydrotalcite Zn-Al-CQ 3 .
Ethylene carbonate, produced according to Example
3, and ethanol are charged into a glass reactor in a molar ratio of 1/4; the hydrotalcite Zn 6 Al 2 (OH) 16 O 3 · 6 H 2 O, synthesized by the Applicant, is then added in a ratio of 5% by weight; the reaction mixture is heated to 83°C and is sent to reflux for 3 hours. After 3 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography. The conversion of ethylene carbonate proves to be equal to 80% (thermodynamic limit of the transesterification reaction) with a selectivity to the desired product (diethyl carbonate) higher than 99%. No significant quantities of by-products are observed. A quantitative analysis on the reaction product thus obtained excludes the presence of metals (Zn, Mg) up to the analytical limit analyzable (0.5 ppm) .
Example 5
Step (a) of the synthesis of diethylene carbonate with hydrotalcite Cu-Zn-Al-CQ 3 .
Urea and ethylene glycol are charged into a glass reactor in a molar ratio of 1/1.2 and the hydrotalcite Cu Zn 2 Al 2 (OH) 16 C0 3 ·ηΗ 2 0, synthesized by the Applicant, is added in a ratio of 5% by weight; the reaction mixture is heated to 130°C and a vacuum is applied reducing the pressure to 30 mbar. After 10 hours, the reaction is interrupted and the reaction product is analyzed by means- of gaschromatography . The conversion of urea proves to be total with a selectivity to the desired product (ethylene carbonate) equal to 90%. The byproducts consist of oxazolidone (4%) and the corresponding hydroxycarbonate (6%) .
Step (b) of the synthesis of diethylene carbonate with hydrotalcite Cu-Zn-Al-CQ 3 .
Ethylene carbonate, produced according to Example 5, and ethanol are charged into a glass reactor in a molar ratio of 1/4; the hydrotalcite
Cu 4 Zn2Al2 (OH) 16CO3 ·ηΗ 2 0, synthesized by the Applicant, is then added in a ratio of 5% by weight; the reaction mixture is heated to 83°C and is sent to reflux for 3 hours. After 3 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography . The conversion of ethylene carbonate proves to be equal to 80% (thermodynamic limit of the transesterification reaction) with a selectivity to the desired product (diethyl carbonate) equal to 98%. No significant quantities of by-products are observed, the only product present with the desired product is the reaction intermediate ( 2 -hydroxyethylcarbonate ) . A quantitative analysis on the reaction product thus obtained excludes the presence of metals (Zn, Cu) up to the analytical limit analyzable (0.5 ppm) .
Example 6
Step (a) of the synthesis of diethylene carbonate with hydrotalcite Zn-Fe-CQ 3 .
Urea and ethylene glycol are charged into a glass reactor in a molar ratio of 1/1.2 and the hydrotalcite Zn 6 Fe2 (OH) 16 CO 3 ·ηΗ 2 0, synthesized by the Applicant, is added in a ratio of 5% by weight; the reaction mixture is heated to 130°C and a vacuum is applied reducing the pressure to 30 mbar. After 7 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography. The conversion of urea proves to be total with a selectivity to the desired product (ethylene carbonate) equal to 92%. The byproducts consist of oxazolidone (3%) and the corresponding hydroxycarbonate (4%) .
Step (b) of the synthesis of diethylene carbonate with hydrotalcite Zn-Fe-CQ 3 . Ethylene carbonate, produced according to Example 5, and ethanol are charged into a glass reactor in a molar ratio of 1/4; the hydrotalcite
Zn 6 Fe2 (OH) i 6 C0 3 ·ηΗ2θ, synthesized by the Applicant, is then added in a ratio of 5% by weight; the reaction mixture is heated to 83°C and is sent to reflux for 3 hours. After 3 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography . The conversion of ethylene carbonate proves to be equal to 80% (thermodynamic limit of the transesterification reaction) with a selectivity to the desired product (diethyl carbonate) equal to 99%. No significant quantities of by-products are observed, the only product present with the desired product is the reaction intermediate (2-hydroxyethylcarbonate) . A quantitative analysis on the reaction product thus obtained excludes the presence of metals (Zn, Fe) up to the analytical limit analyzable (0.5 ppm) .
Example 7
Step (a) of the synthesis of diethylene carbonate with hydrotalcite Zn-Cr-CC>3 .
Urea and ethylene glycol are charged into a glass reactor in a molar ratio of 1/1.2 and the hydrotalcite Zn 6 Cr 2 (OH) ieC0 3 ·ηΗ 2 0, synthesized by -the Applicant, is added in a ratio of 5% by weight; the reaction mixture is heated to 130°C and a vacuum is applied reducing the pressure to 30 mbar. After 6 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography. The conversion of urea proves to be total with a selectivity to the desired product (ethylene carbonate) equal to 91%. The byproducts consist. of oxazolidone (4%) and the corresponding hydroxycarbonate (5%) .
Step (b) of the synthesis of diethylene carbonate with hydrotalcite Zn-Cr-C0 3 .
Ethylene carbonate, produced according to Example 5, and ethanol are charged into a glass reactor in a molar ratio of 1/4; the hydrotalcite Zn 6 Cr 2 (OH) i 6 C0 3 ·ηΗ 2 θ, synthesized by the Applicant, is then added in a ratio of 5% by weight; the reaction mixture is heated to 83°C and is sent to reflux for 3 hours. After 3 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography . The conversion of . ethylene carbonate proves to be equal to 80% (thermodynamic limit of the transesterification reaction) with a selectivity to the desired product (diethyl carbonate) equal to 97%. No significant quantities of by-products are observed, the only product present with the desired product is the reaction intermediate ( 2-hydroxyethylcarbonate ) . A quantitative analysis on the reaction product thus obtained excludes the presence of metals (Zn, Cr) up to the analytical limit analyzable (0.5 ppm) .
Comparative Example 1
Step (a) of the synthesis of diethylene carbonate with hydrotalcite PURAL MG 70.
Urea and ethylene glycol are charged into a glass reactor in a molar ratio of 1/1.2 and the hydrotalcite PURAL MG 70, a commercial product with a molar ratio Mg/Al of 7/3, is added in a ratio of 5% by weight; the reaction mixture is heated to 130°C and a vacuum is applied reducing the pressure to 30 mbar. After 3 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography . The conversion of urea proves to be total with a selectivity to the desired product (ethylene carbonate) equal to 18%. The by-products consist of oxazolidone (62%), the corresponding hydroxycarbonate (15%) and ethylene urea (5%) .
Comparative Example 2
Step (b) of the synthesis of diethylene carbonate with hydrotalcite EXM 2221.
Ethylene carbonate, produced according to comparative Example 1, and ethanol are charged into a glass reactor in a molar ratio of 1/4; the commercial hydrotalcite EXM 2221, magnesium and aluminium hydrotalcite with an unknown chemical composition, is then added in a ratio of 5% by weight; the reaction mixture is heated to 83°C and is sent to reflux for 3 hours. After 4 hours, the reaction is interrupted and the reaction product is analyzed by means of gaschromatography. The conversion of ethylene carbonate proves to be equal to 7.3% (thermodynamic limit of the transesterification reaction) with a selectivity to the desired product (diethyl carbonate) equal to 48%, whereas 52% of the reaction product consists of .the partial transesterification product (ethyl-2 hydroxyethyl carbonate) .