BIOFUEL AND METHOD FOR PREPARATION BY ISOMERIZING METATHESIS

Abstract

Subject of the invention is a process for producing a biofuel from fatty acid methyl esters (FAMEs) obtained by transesterification of vegetable oils, comprising the steps of (a) ethenolysis of the fatty acid methyl esters in the presence of ethylene and an ethenolysis catalyst, and (b) isomerizing metathesis in the presence of an isomerization catalyst and a metathesis catalyst.

The invention also relates to biofuels obtainable by the inventive process and to uses of ethylene for adjusting and optimizing biofuels.

Claims

1.-24. (canceled)

25. A process for producing a biofuel from fatty acid methyl esters (FAMEs) obtained by transesterification of vegetable oils, comprising the steps of (a) ethenolysis of the fatty acid methyl esters in the presence of ethylene and an ethenolysis catalyst, and (b) isomerizing metathesis in the presence of an isomerization catalyst and a metathesis catalyst, wherein ethenolysis (a) and isomerizing metathesis (b) are carried out simultaneously and wherein the process is carried out without an additional solvent.

26. The process according to claim 25, wherein the vegetable oil and/or fatty acid methyl esters comprise more than 80 mol-% unsaturated fatty acids, based on the total amount of fatty acids in esterified and free form, wherein the vegetable oil is preferably rapeseed oil, soy bean oil, jatropha oil or tall oil.

27. The process according to at least claim 25, wherein the isomerization catalyst is an organometallic palladium catalyst.

28. The process according to at least claim 25, wherein the isomerization catalyst is an organometallic palladium containing palladium in oxidation states selected from the group consisting of Pd(0), Pd(I), Pd(II) and combinations thereof.

29. The process according to at least claim 25, wherein the isomerization catalyst is an organometallic palladium catalyst containing at least one structural element Pd—P(R.sup.1R.sup.2R.sup.3), wherein the R.sup.1 to R.sup.3 radicals each independently have 2 to 10 carbon atoms, each of which may be aliphatic, alicyclic, aromatic or heterocyclic, with the proviso that at least one of the R.sup.1 to R.sup.3 radicals contains a beta-hydrogen.

30. The process according to at least claim 25, wherein the isomerization catalyst is a compound (I): ##STR00004## wherein X is a spacer selected from halogen, oxygen and O-alkyl, Y.sup.1 is a P(R.sup.1R.sup.2R.sup.3) group, Y.sup.2 is a P(R.sup.4R.sup.5R.sup.6) group in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 each independently have 2 to 10 carbon atoms, each of which may be aliphatic, alicyclic, aromatic or heterocyclic, with the proviso that at least one of the R.sup.1 to R.sup.6 radicals contains a beta-hydrogen.

31. The process according to claim 30, wherein groups Y.sup.1 and Y.sup.2 are the same.

32. The process according to claim 30, wherein X is bromine and R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sup.5 and R.sup.6 are each defined as tert-butyl, in particular bromo(tri-tert-butylphosphine)palladium(I) dimer.

33. The process according to at least claim 25, wherein the ethenolysis catalyst and/or the metathesis catalyst are organometallic ruthenium catalysts, preferably N-heterocyclic carbene ruthenium complexes.

34. The process according to at least claim 25, wherein the ethenolysis catalyst is selected from the group consisting of dichloro(o-isopropoxyphenylmethylene)(tricyclohexylphosphine)ruthenium(II) (HGI), [1,3-bis(2,6-diisopropylphenyl)-2-imidazolidinylidene]dichloro[5-(isobutoxycarbonylamido)-2-isopropoxybenzylidene]ruthenium(II), [[1-[2,6-bis(1-methylethyl)phenyl]-3,3,5,5-tetramethyl-2- pyrrolidinylidene]dichloro[[2-(1-methylethoxy-KO)phenyl]methylene-.sub.KC]ruthenium(II) (Ru-CAAC) and combinations thereof.

35. The process according to at least claim 25 wherein the metathesis catalyst is selected form the group consisting of [1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]-[2-[[(2-methylphenyl)imino] methyl]-phenolyl]- [3-phenyl- 1H-inden-1-ylidene] (chloro)ruthenium(II) (Ru-1), [1,3-Bis(2,6-Diisopropylphenyl)-2-imidazolidinylidene]dichloro[5-(Isobutoxycarbonylamido)-2-isopropoxybenzylidene]ruthenium(II) (M73 SIPr), [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(2-iodophenylmethylene)ruthenium(II) (M91), [1,3-Bis(2,6-diisopropylphenyl)-2-imidazolidinylidene]dichloro[(2-isopropoxy)(5-pentafluorobenzoylamino)benzylidene]ruthenium(II) (M72SIMes) and combinations thereof.

36. The process according to at least claim 25, wherein ethenolysis (a) and isomerizing metathesis (b) are carried out repetitively.

37. The process of claim 29, wherein the ethenolysis catalyst is [[1-[2,6-bis(1-methylethyl)phenyl]-3,3,5,5-tetramethyl-2- pyrrolidinylidene]dichloro[[2-(1-methylethoxy-.sub.KO)phenyl[methylene-.sub.KC[ruthenium(II) (Ru-CAAC), wherein preferably the isomerization catalyst is bromo(tri-tert-butylphosphine)palladium(I) dimer (IC-1), wherein preferably the metathesis catalyst is selected from [1,3-bis(2,6-diisopropylphenyl)-2-imidazolidinylidene[dichloro[5-(isobutoxycarbonylamido)-2-isopropoxybenzylidene[ruthenium(II) (M73SIPr), [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene[dichloro(2-iodophenylmethylene)ruthenium(II) (M91), and [1,3-Bis(2,6-diisopropylphenyl)-2-imidazolidinylidene] dichloro[(2-isopropoxy)(5-pentafluorobenzoylamino)benzylidene[ruthenium(II) (M72SIMes).

38. The process according to at least claim 25, wherein the ethenolysis catalyst and metathesis catalyst are the same catalyst.

39. The process according to at least claim 25, wherein the process is carried out at a pressure of 2 bar or less.

40. The process according to at least claim 25, wherein the process is carried out as a one-pot reaction.

41. The process according to at least claim 25, wherein the biofuel obtained in step (b) is further processed in post-treatment steps which do not chemically change the chain lengths of the fatty acids, especially in physical treatment steps such as washing, filtration or distillation, or in an adsorptive, antioxidative or sulphur removal treatment.

42. The biofuel obtainable by a process of at least claim 25.

43. The biofuel of claim 42, wherein the average chain length of the olefins is between 4.5 and 14, and/or the average chain length of the unsaturated monoesters is between 6.5 and 15, and/or the average chain length of the unsaturated diesters is between 7 and 17, wherein all amounts are determined by gas chromatography after hydrogenation.

44. The biofuel of claim 42, wherein the molar amount of compounds comprising more than 22 carbon atoms in the main chain is below 2%, wherein all amounts are determined by gas chromatography after hydrogenation.

45. The biofuel according to claim 41 having a molecular weight distribution of the olefins and/or of the unsaturated diesters, respectively, which essentially follows an even curve with a single maximum, wherein all amounts are determined by gas chromatography after hydrogenation.

46. The biofuel according to claim 41, having a boiling curve determined according to EN ISO 3405, which essentially follows a rising curve without peaks or steps at least between 180° C. and 350° C., and/or wherein the recovery during boiling at 250° C. is <65%, the recovery at 350° C. is at least 85%, and/or the recovery at 360° C. is at least 95%, respectively determined according to EN 590:2013-04.

47. The biofuel of at least claim 41, comprising between 25 to 90% mol-% olefins, 10 to 80% mol-% unsaturated monoesters and 1 to 20 mol-% unsaturated diesters, wherein all amounts are determined by gas chromatography after hydrogenation.

48. The use of ethylene for adjusting and/or optimizing the composition of a biofuel in a method of claim 25.

Description

[0110] Exemplified embodiments of the invention and aspects of the invention are shown in the figures.

[0111] FIG. 1: Schematic boiling point curves of standard petrodiesel (dotted line), pure RME (upper continuous line) and cross-metathesized RME (dashed line).

[0112] FIG. 2: Mass-corrected gas chromatogram of the hydrogenated product from RME and ethylene produced in a sequential reaction according to example 1.

[0113] FIG. 3: Mass-corrected gas chromatogram of the hydrogenated product from RME and ethylene produced in a single step reaction according to example 2 (retention times in FIGS. 2 and 3 are not directly comparable due to process variations).

[0114] FIG. 4: Boiling curve determined according to EN ISO 3405:2001-04 of the product from RME and ethylene produced in a sequential reaction according to example 1 (dotted line), in a single step reaction according to example 2 (dashed line) and of petrodiesel (continuous line). The areas on the top left and bottom right show the “forbidden” areas for petrodiesel defined in EN 590.

EXAMPLES

[0115] Catalysts:

[0116] In preceding experiments, catalysts were identified which are applicable for a combined ethenolysis and isomerizing metathesis. A large number of experiments and diligent research were necessary to identify catalysts and combinations which are compatible and suitable for simultaneous batch reactions. Known protocols regarding isomerizing metathesis had to be revised considerably in order to overcome the known problems with gaseous ethylene described further above and its inhibitory effect on palladium catalysts. The catalysts identified thereby which are used according to the working examples are summarized in scheme 2 below.

##STR00003##

[0117] IC-1: Bromo(tri-tert-butylphosphine)palladium(I) dimer; CAS number 185812-86-6; Sigma Aldrich.

[0118] Ru-1: [1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]-[2-[[(2 methylphenyl)imino]methyl]- phenolyl]-[3-phenyl-1H-inden-1 ylidene](chloro)ruthenium(II), CAS number: 934538-12-2; Umicore M42.

[0119] Ru-CAAC: [[1-[2,6-bis(1-methylethyl)phenyl]-3,3,5,5-tetramethyl-2-pyrrolidinylidene]dichloro[[2-(1-methylethoxy-.sub.KO)phenyl]methylene-.sub.KC]ruthenium(II), CAS number 959712-80-2; prepared according to Lavallo et al., 2005; Marx et al., 2015, and Anderson et al., 2007.

[0120] HGI: Dichloro(o-isopropoxyphenylmethylene)(tricyclohexylphosphine) ruthenium(II), CAS number 203714-71-0; Hoveyda Grubbs I catalyst; Sigma Aldrich.

[0121] M73SIPr: [1,3-bis(2,6-diisopropylphenyl)-2-imidazolidinylidene]dichloro[5-(isobutoxycarbonylamido)-2-isopropoxybenzylidene]ruthenium(II); CAS number: 1212009-05-6; Umicore M73 SIPr.

Example 1: Sequential Reaction

[0122] Step 1: Ethenolysis of RME

[0123] Under an atmosphere of argon, a 1 L stirred Parr autoclave was charged with HGI catalyst (Hoveyda Grubbs I; 3.60 g, 600 μmol) and rape seed oil methyl ester (178 g, 200 mL, 600 mmol based on methyl oleate). The vessel was pressurized with 10 bar ethylene and stirred for 16 h at 25° C. The reactor was cooled down to −20° C. and the ethylene pressure was slowly released. After warming up to ambient temperature, the reaction mixture was filtered over silica and distilled under vacuum (1×10.sup.−3 mbar, up to 250° C.) yielding a mixture of 1-decene and methyl decenoate:methyl oleate:dimethyl octadec-9-enedionate with the ratio 82.7:10.0:5.00 as well as small amounts of additional olefins and saturated components of RME. Due to the reaction being equilibrium, complete conversion could not be achieved. Under the above mentioned solvent-free conditions the excess of ethylene in solution is too small to shift the equilibrium completely to the side of the ethenolysis products.

[0124] Step 2: Isomerizing Metathesis

[0125] In a glovebox under nitrogen atmosphere, a 100 mL Büchi bmd 075 miniclave drive autoclave was charged with the mixture prepared according to step 1 above (54.0 g, 60.0 mL), IC-1 catalyst (303 mg, 390 μmol) and Ru-1 catalyst (329 mg, 390 μmol). The resulting reaction mixture was stirred for 18 h at 50° C. The reactor was cooled down to ambient temperature and a 30% solution of H.sub.2O.sub.2 (27.6 mL, 270 mmol) was slowly added at 0° C. under vigorous stirring (1000 rpm, KPG stirrer). The organic phase was separated, dried over 3 Å molecular sieves and filtered over a short column of celite and MgSO.sub.4. Due to RME and therefore the ethenolysis product being mixtures of different compounds, it is only possible to give a yield based on the volume. Starting from 60 mL of the ethenolysis mixture, 50 mL of the isomerizing metathesis blend was isolated (83%). The composition was analyzed by gas chromatography (GC). For facilitating GC, the sample was hydrogenated before analysis. The peaks were assigned by GC-MS and corrected for their mass to generate the histogram of FIG. 2.

Example 2: Single Step Reaction Upscale

[0126] In a glovebox under nitrogen atmosphere, a 1 L Parr autoclave was charged with Ru-CAAC catalyst [CAS: 959712-80-2] (243 mg, 0.40 mmol), IC-1 (1.24 g, 1.60 mmol), M73SIPr catalyst (330 mg, 0.40 mmol) and RME (135 mL, 400 mmol based on methyl oleate). The resulting reaction mixture was put under a stream of ethylene at atmosphere pressure and was stirred for 16 h at 60° C. The reactor was cooled down to ambient temperature and a 30% solution of H.sub.2O.sub.2 (40.9 mL, 400 mmol) was slowly added at 0° C. under vigorous stirring. The organic phase was separated, dried over MgSO.sub.4 and filtered over a short column of celite and MgSO.sub.4, yielding 75 mL of a brown oil (55% based on volume). The total yield could be increased to 75% or higher if further product was recovered from the aqueous phase. After distillation in vacuum (1E-3 mbar, >350° C.), the product mixture was obtained as a light yellow liquid (>98 wt-% recovery after distillation). The composition was analyzed by gas chromatography (GC). For facilitating GC, the sample was hydrogenated before analysis. The peaks were assigned by GC-MS and corrected for their mass to generate the histogram of FIG. 3.

Example 3: Single Step Reaction with Optimized Yield

[0127] In a glovebox under nitrogen atmosphere, a 30 mL glass reactor was charged with Ru-CAAC catalyst [CAS: 959712-80-2] (30.3 mg, 50.0 μmol), IC-1 (155 mg, 200 μmol), M73SIPr catalyst (41.3 mg, 50.0 μmol) and RME (16.9 mL, 50 mmol based on methyl oleate). The resulting reaction mixture was put under a stream of ethylene at atmosphere pressure and was stirred for 16 h at 60° C. Two of these batches were combined, cooled down to ambient temperature and a 30% solution of H.sub.2O.sub.2 (5.11 mL, 50 mmol) was slowly added at 0° C. under vigorous stirring. The organic phase was separated, dried over MgSO.sub.4 and filtered over a short column of celite and MgSO.sub.4, yielding 25 mL of a brown oil (74% based on volume). After distillation in vacuum (1E-3 mbar, >350° C.), 24 mL of the product mixture was obtained as a light yellow liquid (96% recovery after distillation).

Example 4: Product Properties and Suitability as Biodiesel

[0128] The physical and chemical properties of the products of example 1 and 2 and suitability as biodiesel were investigated. Distillation analyses was carried out in an EN ISO 3405:2001-04 apparatus and furnished experimental boiling point curves shown in FIG. 4 (the continuous line is petrodiesel for comparison). Since 90% distilled below 360° C., the product passed the ASTM D 6751 (2008) specification for biodiesel in this regard. It also passed the specifications for petrodiesel fuels detailed in EN 590:2013-04, namely a recovery of <65% at 250° C. and of at least 85% at 350° C. The product of example 1 had about 95% recovery at a maximum of 360° C. The product of example 2 clearly met the requirement of at least 95% at a maximum of 360° C., thus meeting all boiling specifications. In addition, no decomposition was visible during distillation for all products, which is indicative of a low content of undesired components of very high molecular weight and undesired polyunsaturated components. It can be followed that the inventive reaction provides biofuels with excellent physical properties and that the product of the one step reaction is even more advantageous, possible due to a more homogenous composition.

[0129] Further analysis using standard methods for fuel testing revealed that the material has a sulphur content of <5 mg/kg, a viscosity of 2.12 mm.sup.2/s and a lubricity of 232 μm, all values well within the specifications in EN 590. Moreover, the acid value of 0.360 mg KOH/g is below the threshold for pure biodiesel. Solely the oxidation stability analysis does not yet meet EN 590, but this may certainly be adjusted using standard anti-oxidant additives. The cloud and pour points, which are not explicitly specified, are significantly below 0° C. and thus in a good range for unmodified fuel.

[0130] In conclusion, isomerizing metathesis with ethylene allows converting RME into mixtures of olefins and esters that match the boiling behavior of diesel fuel as specified in EN 590. The inventive composition is applicable as a pure biodiesel without the need for dilution with petrodiesel or other hydrocarbons. The inventive technology may turn out to be a decisive breakthrough towards increasing the content of renewables in diesel fuel—ideally up to 100%.

[0131] For comparison, an isomerizing metathesis of RME with 1-hexene was put into practice. A high effort was necessary to identify specific catalysts which yield a homogenous product. The 1-hexene/RME product showed a recovery of 93% at 360° C., which misses the value of at least 95% required for petrodiesel. Towards the end of the distillation, the product derived from 1-hexene partially decomposed with smoke formation. This is a common problem for biodiesel, caused by oxidation of sensitive polyunsaturated fatty acid derivatives, and is usually addressed by partial hydrogenation of the product fractions. Further, the hexene product showed a less favourable initial boiling behavior at lower temperatures. Overall, the results demonstrated that the hexene product had different and less advantageous properties, which can be attributed to the higher molecular weight of hexene compared to ethylene and the resulting less favourable molecular weight distribution of the products.

LITERATURE

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