Process for the conversion of sugars to lactic acid and 2-hydroxy-3-butenoic acid or esters thereof comprising a metallo-silicate material and a metal ion

Abstract

A process for the preparation of lactic acid and 2-hydroxy-3-butenoic acid or esters thereof from a sugar in the presence of a metallo-silicate material, a metal ion and a solvent, wherein the metal ion is selected from one or more of the group consisting of potassium ions, sodium ions, lithium ions, rubidium ions and caesium ions.

Claims

1. A process for the preparation of lactic acid and 2-hydroxy-3-butenoic acid or esters thereof from a sugar in the presence of a metallo-silicate material, a metal ion and a solvent, said process comprising contacting the sugar with a metallo-silicate material, wherein the metal ion is selected from one or more of the group consisting of potassium ions, sodium ions, lithium ions, rubidium ions and caesium ions.

2. A process according to claim 1, wherein the metal ion is obtainable by the addition to the process of one or more compounds selected from the group consisting of K.sub.2CO.sub.3, KNO.sub.3, KCl, potassium acetate (CH.sub.3CO.sub.2K), potassium lactate (CH.sub.3CH(OH)CO.sub.2K), Na.sub.2CO.sub.3, Li.sub.2CO.sub.3 and Rb.sub.2CO.sub.3.

3. A process according to claim 1, wherein the metallo-silicate material framework structure is selected from the group consisting of BEA, MFI, FAU, MOR, FER, MCM and SBA.

4. A process according to claim 1, wherein the metallo-silicate material comprises an active metal selected from one or more of the group consisting of Sn, Ti, Pb, Zr, Ge and Hf.

5. A process according to claim 1, wherein the metallo-silicate material is selected from the group consisting of Sn-BEA, Sn-MFI, Sn-FAU, Sn-MCM-41 and Sn-SBA-15.

6. A process according to claim 1, wherein the sugar is selected from one or more of the group consisting of glucose, fructose, mannose, sucrose, xylose, erythrose, erythrulose, threose and glycolaldehyde.

7. A process according to claim 1, wherein the solvent is selected from one or more of the group consisting of methanol, ethanol, 1-propanol, 1-butanol and water.

8. A process according to claim 1, wherein the ester of lactic acid is methyl lactate or ethyl lactate.

9. A process according to claim 1, wherein the yield of methyl lactate is equal to or greater than 69%.

10. A process according to claim 1, wherein the metallo-silicate material is prepared using a post synthesis process.

11. A process according to claim 1, wherein the metallo-silicate material is prepared by impregnating a de-aluminated or de-boronated zeotype material or mesoporous amorphous silicate material with an active metal.

12. A process according to claim 1, wherein the metallo-silicate material is prepared by impregnating a de-aluminated or de-boronated zeotype material or mesoporous amorphous silicate material with an active metal and a metal ion.

Description

EXAMPLES

(1) The following examples are provided to illustrate the invention. The examples shall not be construed as a limitation of how the invention may be practised.

(2) Method A: Method for Preparing Methyl Lactate from Sucrose [16 Hour Reaction Duration].

(3) A stainless steel pressure vessel (40 cc, Swagelok) is charged with a methanol (15.0 g; Sigma-Aldrich, >99.8%) solution of the metal salt (metal ion source), sucrose (0.450 g; Fluka, >99.0%) and catalyst (0.150 g). The reactor is closed and heated to 160 C. under stirring (700 rpm). The reaction is continued at 160 C. for 16 h and after this period, the reaction is quenched by submerging the vessel in cold water. Samples from the reaction vessel are filtered and analysed by HPLC (Agilent 1200, Biorad Aminex HPX-87H column at 65 C., 0.05 M H.sub.2SO.sub.4, 0.6 ml min.sup.1) to quantify unconverted hexoses and dihydroxyacetone (DHA), glyceraldehyde (GLA); and GC (Agilent 7890 with a Phenomenex Solgel-wax column) was used to quantity: methyl lactate (ML), methyl vinylglycolate (MVG, methyl 2-hydroxy-3-butenoate) and glycolaldehyde dimethylacetal (GADMA).

(4) The amount of metal salt is provided for all Examples via the column entitled: initial metal ion concentration in methanol.

(5) Method B: Method for Preparing Methyl Lactate from Sucrose [4 Hour Reaction Duration].

(6) A method for preparing methyl lactate from sucrose as described in Method A, with the exception that the reaction duration is 4 hours.

(7) Catalyst Preparation:

(8) Catalyst A [Sn-BEA (Si/Sn=125)]:

(9) Commercial zeolite Beta (Zeolyst, Si/Al 12.5, ammonium form) is calcined (550 C. for 6 h) to obtain the zeolite Beta H form (de-aluminated form) and treated with 10 grams of concentrated nitric acid (Sigma-Aldrich, 65%) per gram of zeolite Beta powder for 12 h at 80 C. The resulting solid is filtered, washed with ample water and calcined (550 C. for 6 h) to obtain the de-aluminated Beta solid.

(10) The de-aluminated Beta solid is impregnated with Sn by incipient wetness methodology with a Sn/Si ratio of 125 using the following method: tin (II) chloride (0.128 g, Sigma-Aldrich, 98%) is dissolved in water (5.75 mL) and added to the de-aluminated Beta (5 g). After impregnation the samples are dried 12 h at 110 C. and calcined (550 C. for 6 h).

(11) Catalyst A [Sn-BEA (Si/Sn=125) Comprising a Metal Ion]:

(12) Sn-BEA (Si/Sn=125) comprising a metal ion is prepared according to a modification of the previous procedure (preparation of Catalyst A). Commercial zeolite Beta (Zeolyst, Si/Al 12.5, ammonium form) is calcined (550 C. for 6 h) to obtain the H form (de-Aluminated form) and treated with 10 g of concentrated nitric acid (Sigma-Aldrich, 65%) per gram of zeolite Beta powder for 12 h at 80 C. The resulting solid is filtered, washed with ample water and calcined (550 C. for 6 h) to obtain a de-aluminated Beta solid.

(13) The de-aluminated Beta solid is impregnated with Sn and potassium ions by incipient wetness methodology to obtain a Sn/Si ratio of 125 using the following method: tin (II) chloride (0.125 g, Sigma-Aldrich, 98%) is dissolved in a K.sub.2CO.sub.3 solution (5.75 mL of 0.0015 M in water) and added to the de-aluminated Beta (5 g). After impregnation the samples are dried 12 h at 110 C. and calcined (550 C. for 6 h).

(14) Catalyst A:

(15) Sn-BEA (Si/Sn=200) is prepared according to a modification of the route described in U.S. Pat. No. 6,306,364 B1. TEOS (30.6 g; Aldrich, 98%) is added to TEAOH (33.1 g; Sigma-Aldrich, 35% in water) under stirring, forming a two-phase system. After 60-90 min, one phase is obtained. Tin(IV)chloride pentahydrate (0.26 g; SnCl.sub.4.5H.sub.2O, Aldrich, 98%) is dissolved in water (2.0 mL) and added dropwise. The solution is then left for several hours under stirring until a viscous gel was formed. The gel is then mineralized by the addition of HF (3.1 g; Fluka, 47-51%) in demineralized water (1.6 g). A suspension of de-aluminated seeds of Sn-BEA (0.36 g) in demineralized water (3.0 g) is added, followed by manual mixing. The gel is homogenized and transferred to a Teflon-lined container and placed in a stainless steel autoclave and heated statically at 140 C. for 14 days. The solid is recovered by filtration and washed with ample amounts of deionized water, followed by drying overnight at 80 C. in air. The synthesis is finalized by removing the organic template by heating the sample at 2 C./min to 550 C. in static air and maintaining this temperature for 6 h.

(16) Catalyst B [SnY]:

(17) Commercial zeolite Y (Zeolyst, Si/Al 50, hydrogen form) is treated with 10 grams of concentrated nitric acid (Sigma-Aldrich, 65%) per gram of zeolite Beta powder for 12 h at 80 C. The resulting solid is filtered, washed with ample water and calcined (550 C. for 6 h) to obtain de-aluminated Y.

(18) The de-alumintaed Y solid is impregnated with Sn by incipient wetness methodology with a Sn/Si ratio of 125 using the following method: tin (II) chloride (0.124 g, Sigma-Aldrich, 98%) is dissolved in water (7.5 mL) and added to de-aluminated Y (5 g). After impregnation the samples are dried for 12 h at 110 C. and calcined (550 C. for 6 h).

(19) Catalyst C [Sn-MCM-41]:

(20) Sn-MCM-41 is prepared according to the method described by Li, L. et al. [Green Chem. 2011, 13, 1175-1181]. In a typical synthesis hexadecyltrimethylammonium bromide (13.0 g; CTABr, Sigma >98%) is dissolved in water (38.0 g). Tetramethylammonium silicate (26.4 g; TMAS, Aldrich, 15-20 wt % in water) is added slowly. The mixture is stirred for 50 min. Tin(IV)chloride pentahydrate (SnCl.sub.4.5H.sub.2O; 0.179 g; Aldrich, 98%) and HCl (0.605 g; Sigma-Aldrich, 37 wt %) are dissolved in water (2.1 g) and added slowly to the solution. The resulting mixture is stirred for 1.5 h and TEOS (12.2 g) is added. The mixture is stirred for another 3 h and transferred to a Teflon lined autoclave and heated to 140 C for 15 h. The solid is recovered by filtration and washed with ample amounts of deionized water, followed by drying overnight at 80 C. in air. The synthesis was finalized by removing the organic template by heating the sample at 2 C./min to 550 C. in static air and maintaining this temperature for 6 h.

Examples 1-6

(21) Method A (16 h reaction) was followed using Catalyst A and the metal salt (metal ion source). Results are provided in Table 1.

(22) TABLE-US-00001 TABLE 1 Initial metal ion concentration in Ratio of Percentage Total Metal salt methanol active Yield of Conversion [Metal ion (mmol/L) metal to methyl of Hexose Ex source] [M+] metal ion lactate Sugars 1 27 76 2 K.sub.2CO.sub.3 0.13 5 72 96 3 KNO.sub.3 0.13 5 23 93 4 KCl 0.13 5 28 95 5 Potassium 0.13 5 39 95 Acetate 6 Potassium 0.13 5 46 95 lactate

Examples 7-10

(23) Method A (16 h reaction) was followed using Catalyst A and the metal salt (metal ion source). Results are provided in Table 2.

(24) TABLE-US-00002 TABLE 2 Initial metal ion concentration in Ratio of Percentage Total Metal salt methanol active Yield of Conversion [Metal ion (mmol/L) metal to methyl of Hexose Ex source] [M+] metal ion lactate Sugars 2 K.sub.2CO.sub.3 0.13 5 72 96 7 Li.sub.2CO.sub.3 0.13 5 59 84 8 Na.sub.2CO.sub.3 0.13 5 72 97 9 Rb.sub.2CO.sub.3 0.13 5 67 98 10 CaCO.sub.3 0.13 5 18 94

Examples 11-17

(25) Method A (16 h reaction) was followed varying the type of metallo-silicate material. The metal salt used as a source of metal ions is K.sub.2CO.sub.3. Results are provided in Table 3.

(26) TABLE-US-00003 TABLE 3 Initial metal ion concentration in Ratio of Percentage Total methanol active metal Yield of Conversion (mmol/L) to metal methyl of Hexose Ex Catalyst [M+] ion lactate Sugars 1 A 27 76 2 A 0.13 5 72 96 11 A 7 71 96 12 A 26 93 13 A 0.13 3 58 73 14 B 11 67 15 B 0.13 5 67 97 16 C 20 79 17 C 0.13 3 52 89

Examples 18-23

(27) Method A (16 h reaction) was followed varying the concentration of the metal ion; the metal salt used as a metal ion source is K.sub.2CO.sub.3. Catalyst A is used. Results are provided in Table 4.

(28) TABLE-US-00004 TABLE 4 Initial metal ion concentration Ratio of Percentage in active Yield of Total methanol metal to methyl Conversion Ex (mmol/L) [M+] metal ion lactate of Hexose Sugars 1 0 27 76 18 0.06 10.3 57 97 19 0.11 6.2 67 98 2 0.13 5.0 72 96 20 0.14 4.2 72 94 21 0.17 3.9 72 96 22 0.20 3.2 67 88 23 0.23 2.6 62 73

Examples 24-28

(29) Method A (16 h reaction) was followed varying the concentration of the metal ion; the metal salt used as a metal ion source is K.sub.2CO.sub.3. Catalyst A is used. Results are provided in Table 5.

(30) TABLE-US-00005 TABLE 5 Initial metal ion concentration Ratio of Percentage Total in active Yield of Conversion methanol metal to methyl of Hexose Ex (mmol/L) [M+] metal ion lactate Sugars 12 0 26 93 24 0.03 16.0 57 97 25 0.045 9.0 67 93 26 0.055 7.0 69 94 27 0.065 6.5 75 93 28 0.1 4.5 59 78 13 0.13 3 58 73

Examples 29-33

(31) Method B (4 h reaction) was followed varying the concentration of the metal ion; the metal salt used as a metal ion source is K.sub.2CO.sub.3. Catalyst B is used. Results are provided in Table 6.

(32) TABLE-US-00006 TABLE 6 Initial metal ion concentration Ratio of Percentage Total in active Yield of Conversion methanol metal to methyl of Hexose Ex (mmol/L) [M+] metal ion lactate Sugars 14 0 11 67 29 0.07 7.7 33 30 0.10 6.3 45 31 0.13 5.0 56 32 0.17 4.0 44 33 0.20 3.3 45
Key:
[M+]=Metal ion concentration in the reaction solution.
[K.sub.2CO.sub.3]=Metal ion concentration; in this Example the metal ion is potassium originating from K.sub.2CO.sub.3.
%=Percentage Yield of methyl lactate
Conversion of Sugar=Total Conversion of Sugar Starting Material.

(33) FIG. 1:

(34) Examples 1, 2 and 18 to 23: Comparison of methyl lactate yield and conversion of sugar with variation of the metal ion concentration. Method A was followed using Catalyst A.

(35) FIG. 2:

(36) Examples 1, 2 and 12 to 17: Comparison of methyl lactate yield prepared via Method A using catalysts A, A, B and C; wherein the reaction is carried out in pure methanol (i.e. without a metal ion), or methanol and a metal ion (i.e. potassium ions). Methyl lactate yield is significantly increased by the addition of a metal ion (i.e. potassium ions).