Catalytic process for the production of propylene glycol from glycerol, a copper and cerium catalyst, and a process to produce such catalyst

Abstract

A process for producing propylene glycol from glycerol including a catalyst of Cu and Ce at concentrations of up to 15% of each metal. In addition, it is described a catalyst of Cu and Ce to perform the selective reduction of glycerol and the process of production of such catalyst.

Claims

1. A process for producing a catalyst; comprising the following steps: a. grinding an alumina support to produce alumina particles and sieving to a particle size ranging between 35 and 80 mesh; b. conditioning the alumina particles at 110 C. for one hour and then burning them in air stream at 500 C. for 3 hours; c. adding drop by drop the solution of the precursor of a first metal on the alumina particles support to damp the whole mass of alumina particles, with ongoing stirring, until wet particles remain united despite the stirring; then, continue adding 5% more solution than the equivalent to the volume of pores belonging to the support; d. maintaining the impregnated support in a desiccator between 4 and 6 hours; e. drying in oven at 110 C. for at least 8 hours; f. burning the dried impregnated support in air stream at a temperature of up to 3000 C for at least 1.5 hours, remaining the metal oxide on the support; g. cooling in a stream of nitrogen; h. adding drop by drop the solution of precursor of a second metal on the alumina particles support until damping the whole mass of alumina particles, with ongoing stirring, until the wet particles remain united despite the stirring; then, continue adding 5% more of solution than the equivalent to the volume of the pores belonging to the support; i. maintaining the impregnated support in a desiccator between 4 and 6 hours; j. drying in oven at 110 C. for at least 8 hours; k. burning the dried impregnated support in air stream at a temperature of up to 3000 C for at least 1.5 hours, remaining the metal oxide on the support; and l. cooling in a stream of nitrogen; wherein x-ray diffraction of said catalyst shows peaks at 43, 28 and 56.

2. The process of claim 1 wherein the first metal of step c) is copper and the second metal of step h) is cerium.

3. The process of claim 1 wherein the first metal of step c) is cerium and the second metal of step h) is copper.

4. The process of claim 1 wherein the catalyst obtained comprises a concentration of cerium of up to 15% by weight and a concentration of copper of up to 15% by weight.

5. The process of claim 1 wherein the catalyst obtained comprises a concentration of cerium of up to 7% by weight and a concentration of copper of up to 7% by weight.

6. A catalyst made by the process of claim 1 and comprising copper and cerium supported on alumina, wherein the concentration of Cu is up to 10% by weight, the concentration of Ce is up to 10% by weight.

7. The catalyst of claim 6 wherein the concentration of Cu is up to 7% by weight and the concentration of Ce is up to 7% by weight.

8. The catalyst of claim 6 comprising: an alumina support with specific surface ranging between 150 and 250 m.sup.2 g.sup.1 and pore volume ranging between 0.1 and 1.0 cm.sup.3 g.sup.1; copper oxide; and cerium oxide.

9. A catalytic process for producing propylene glycol by the selective reduction of glycerol comprising the following steps: a. providing a stream of glycerol and H.sub.2; b. contacting the stream of step with the catalyst of claim 3; and c. obtaining a stream of propylene glycol.

10. The catalytic process of claim 9 wherein the operating conditions of step b comprise the following: a temperature between 170 and 200 C.; a total pressure of 1 atm; a partial pressure of H.sub.2 ranging between 0.3 and 1 atm; a relation of helium/hydrogen ranging between 0 and 3/2; a concentration of glycerol ranging between 20 and 50% in weight; a liquid hourly space velocity ranging between 0.05 and 15.00 h.sup.1; and a contact time ranging between 0.03 and 5.00 minutes.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1: XRD patterns corresponding to alumina and to catalysts made up of CuCe impregnated on alumina.

(2) FIG. 2: RTP profiles of catalysts made up of CuCe impregnated on alumina.

(3) FIG. 3: FTIR spectra of the catalysts made up of CuCe impregnated on alumina.

(4) FIG. 4: Conversion of glycerol (X) and selectivities to propylene glycol (S.sub.PG) and propylene glycol plus acetol (S.sub.PG+AC) for different Cu catalysts.

(5) FIG. 5: Conversion of glycerol (X) and selectivities to propylene glycol (S.sub.PG) and propylene glycol plus acetol (S.sub.PG+AC) for different catalysts of CuCe/Al.sub.2O.sub.3-experience conditions table 2.

(6) FIG. 6: Conversion of glycerol (X) and selectivities to propylene glycol (S.sub.PG) and propylene glycol plus acetol (S.sub.PG+AC) for different catalysts of CeCu/Al.sub.2O.sub.3 experience conditions table 3.

(7) FIG. 7: Comparison of conversion of glycerol (X) and selectivities to propylene glycol (S.sub.PG) and propylene glycol plus acetol (S.sub.PG+AC) for CuCe/Al.sub.2O.sub.3 and CeCu/Al.sub.2O.sub.3.

(8) FIG. 8: Conversion of glycerol (X) and selectivities to propylene glycol (S.sub.PG) and propylene glycol plus acetol (S.sub.PG+AC) with CeCu/Al.sub.2O.sub.3 catalystexperience conditions table 4

BRIEF DESCRIPTION OF THE INVENTION

(9) This invention describes a catalytic process to produce propylene glycol from glycerol, comprising the selective reduction of such glycerol through a catalyst of copper and cerium supported on alumina, wherein the concentration of Cu is of up to 15% in weight, the concentration of Ce is of up to 15% in weight, and the operating conditions of such process include a temperature ranging from 170 to 200 C., a total pressure of 1 atmosphere, partial pressure of H.sub.2 ranging from 0.3 to 1 atmosphere, a helium/hydrogen relation ranging from 0 to 3/2, a glycerol concentration ranging from 20 to 50% in weight, a liquid hourly space velocity ranging from 0.05 to 15.00 h-1, and a contact time ranging from 0.03 to 5.00 minutes.

(10) Furthermore, this invention includes a catalyst for such catalytic process comprising copper and cerium supported on alumina wherein the concentration of Cu is of up to 15% in weight, the concentration of Ce is of up to 15% in weight; preferably such concentration of Cu is of up to 7% in weight and such concentration of Ce is of up to 7% in weight.

(11) Another object of this invention is a process to produce the cerium and copper catalyst comprising: an alumina support with a specific surface ranging from 150 to 250 m2 g-1 and pore volume ranging from 0.1 to 1.0 cm3 g-1; copper and cerium precursors; and also comprising the following steps:

(12) a. grinding alumina support and sieving at a particle size ranging from 35 to 80 mesh;

(13) b. conditioning alumina particles at 110 C. for one hour and then burn them in air stream at 500 C. for 3 hours;

(14) c. adding drop by drop the solution of the precursor of the first metal on the support until dampening the whole mass, with ongoing stirring, until the wet particles remain united despite stirring; then continuing adding 5% more of solution than the equivalent to the volume of pores corresponding to the support;
d. maintaining the impregnated support in a desiccator between 4 and 6 hours;
e. drying in oven at 110 C. for at least 8 hours;
f. burning the dried impregnated support in air stream at temperatures of up to 300 C. for at least 1.5 hours, leaving the metal oxide on the support;
g. cooling in air stream of nitrogen;
h. adding drop by drop the solution of the precursor of the second metal on the support until damping the whole mass, with ongoing stirring, until wet particles remain united although stirring; then, continuing adding 5% more of solution than the equivalent to the volume of the pores belonging to the support;
i. maintaining the impregnated support in desiccator between 4 and 6 hours;
j. drying in oven at 110 C. for at least 8 hours;
k. burning the dry impregnated support in air stream at a temperature of up to 300 C. for at least 1.5 hours, leaving the metal oxide on the support;
l. cooling in a stream of nitrogen.

(15) Wherein in such step c), such first metal is copper; and on the second impregnation of such step h), such second metal is cerium. Alternatively, such first metal of step c) is cerium and such second metal of step h) is copper.

(16) Wherein from such production process, it is obtained a catalyst comprising a concentration of cerium of up to 15% in weight and a concentration of copper of up to 15% in weight; preferably, it comprises a concentration of cerium of up to 7% in weight and a concentration of copper of up to 7% in weight

DETAILED DESCRIPTION OF THE INVENTION

(17) 1. Preparation of the Catalysts

(18) The base material used for preparations was commercial gamma alumina (identified as -Al.sub.2O.sub.3, with specific surface of 199 m.sup.2 g.sup.1 and pore volume of 0.5 cm.sup.3 g.sup.1), which was ground and sieved at particle size of 35-80 mesh, conditioned at 110 C. for one hour in oven and then burned in air stream at 500 C. for 3 hours.

(19) The precursors of copper (Cu) and cerium (Ce) used were hexahydrate copper nitrate and hexahydrate cerium nitrate, respectively. The concentrations of the common impregnation solutions used were 45.5 and 9.1 g/l of Cu and Ce, respectively, modifying them to obtain other metal loadings.

(20) Impregnation of metal precursors on the support was carried out by means of the technique of incipient wetness impregnation. It was added drop by drop the solution of the desired precursor on the support until damping the whole mass, with ongoing stirring, until the wet particles remain united despite stirring; then, it was added 5% more of solution than the equivalent to the volume of pores corresponding to the support. The impregnated material was kept 4-6 hours in a desiccator to allow proper interaction between the support and the solution of the metal precursor; then, it was taken to oven at 110 C. all the night. The impregnated and dried material was burned in a tubular reactor with fixed bed and downstream flow, heated by an electric oven, passing through the catalyst's bed an air stream of 50 cm.sup.3/min., with a heating rate from 4.5 C./min to 300 C. and maintaining such temperature for 2.5 hours to achieve decomposition of the precursor, thus remaining the metal oxide on the support; after burning, the material was cooled in a nitrogen stream. To introduce the second metal precursor the above sequence is repeated from the step implying addition drop by drop of the solution with the new precursor. Monometallic materials prepared were identified as Cu/-Al.sub.2O.sub.3 and Ce/-Al.sub.2O.sub.3, while bimetallic ones: when entering first Cu and then Ce as CuCe/-Al.sub.2O.sub.3 and when the order is reversed, that is Ce is impregnated in first place and then Cu, as CeCu/-Al.sub.2O.sub.3.

(21) 2. Pretreatment of Catalysts

(22) The pretreatment steps were: i) burning, by passing through the material bed an air stream of 50-100 cm.sup.3 min.sup.1, with a heating rate of 3-6 C. min.sup.1 up to the selected temperature and maintaining it for 2-4 hours; ii) cooling, up to room temperature in nitrogen stream; and iii) reduction, in hydrogen flow of 50-100 cm.sup.3 min.sup.1, using the same heating rate than for burning, and maintaining it for 1-3 hours at 250-400 C.

(23) For bimetallic catalysts, prepared by following different sequences of impregnation of precursor, that is, in first place Cu and then Ce or in first place Ce and then Cu, the pretreatment conditions were selected according to the precursors used, including a burning step between impregnations and a single reduction step. Such pretreatment reduction step comprises hydrogen flow of 70 cm.sup.3/min, using a heating rate from 4.5 C./min to 300 C. and maintaining such temperature for 2 hours to obtain in the material the corresponding metal sites.

(24) Table 1 shows details of the identification of catalysts, as well as the sequence of impregnation of metals, the loads and burning and reduction pretreatment steps.

(25) TABLE-US-00001 TABLE 1 Identification of catalysts, sequence of addition of metals, loads thereof and burning and reduction steps. Impregnation 1 Pretreatments Impregnation 2 Pretreatments ID Metal Load (%) Burning Reduction Metal Load (%) Burning Reduction Cu/-Al.sub.2O.sub.3 Cu 4-15 Yes Yes Ce/-Al.sub.2O.sub.3 Ce 4-12 Yes Yes CuCe/-Al.sub.2O.sub.3 Cu 4-15 Yes No Ce 4-12 Yes Yes CeCu/-Al.sub.2O.sub.3 Ce 4-12 Yes No Cu 4-15 Yes Yes
3. Catalytic Assessment The ranges of operating conditions used to assess the behavior of materials were: Reaction temperature: 170-230 C. Total pressure: 1 atm Hydrogen partial pressure: 0.3-1 atm Helium/hydrogen relation: 0-1.5 Glycerol concentration in supply solution: 20-50% (w/v) Liquid hourly space velocity (LHSV, in relation to glycerol): 0.05-15.00 h.sup.1 Contact time (.sub.c, in relation to hydrogen): 0.03-5.00 min

EXAMPLES

Examples 1-3

(26) FIGS. 1-2-3 show characterizations by XRD, TPR and FTIR, respectively, for monometallic catalysts of Cu and Ce and bimetallic ones of CuCe and CeCu prepared as detailed herein.

(27) FIG. 1 shows the characterization by X-ray diffraction (XRD) of gamma alumina (-Al.sub.2O.sub.3) and catalysts of copper (Cu) and cerium (Ce) impregnated on -Al.sub.2O.sub.3. -Al.sub.2O.sub.3 has its typical pattern. Cu impregnated on -Al.sub.2O.sub.3 (Cu/-Al.sub.2O.sub.3) shows a sharp peak at 43, corresponding to Cu metal species of Cu, without changing the crystal structure of -Al.sub.2O.sub.3. Impregnation of Ce on -Al.sub.2O.sub.3 (Ce/-Al.sub.2O.sub.3) causes peaks, one at 28 and the other one at 56, respectively, corresponding to metal species of Ce, without changing the crystal structure of -Al.sub.2O.sub.3. By impregnating Cu and then Ce (CuCe/-Al.sub.2O.sub.3), the peak intensity of 43 is lower and peaks at 28 and 56 appear; by impregnating in reverse order, that is, in first place Ce and then Cu (CeCu/-Al.sub.2O.sub.3), the peak of 43 is more intense and sharp, which is related to the dispersion of Cu species.

(28) FIG. 2 shows the characterization by temperature programmed reduction (TPR) of -Al2O3 and catalysts of Cu and/or Ce impregnated on -Al2O3. -Al2O3 (profile not shown) does not show hydrogen consumption. Cu/-Al2O3 profile shows that the reduction of species begins at 170 C., with a main max. peak at 225 C. and a small shoulder between 250 and 277 C. Ce/-Al2O3 has a wider and offset reduction profile at higher temperature; impregnated species on the support start to reduce at 250 C., with main max. peak at 350 C. and a small shoulder between 377 and 425 C. For CuCe/-Al2O3, the reduction peak remains well defined but it shifts to higher temperature, being the main max. peak at 265 C. For CeCu/-Al2O3, the species start to reduce at 165 C., being the main max. peak at 220 C. and a second small peak mounted on the tail of the main one, with max. peak at 250 C.

(29) FIG. 3 shows the characterization by Fourier transform infrared spectroscopy (FTIR) of -Al.sub.2O.sub.3 and catalysts of Cu and/or Ce impregnated on -Al.sub.2O.sub.3. All spectra are similar and they include in the high-frequency region an intense band centered at 3500 cm.sup.1, characteristic of -Al.sub.2O.sub.3, related to OH interaction of the support and/or chemisorbed water to the support, and a weak band at 3780 cm.sup.1, related to acid, neutral and basic OH groups. In the low-frequency region, both monometallic catalysts (Cu/-Al.sub.2O.sub.3 and Ce/-Al.sub.2O.sub.3) show a well-defined sharp band at 1385 cm.sup.1, which also appears on bimetallic ones, regardless of the order of impregnation.

Examples 4-9

(30) The behavior of six catalysts containing Cu was assessed during hydrogenolysis reaction or selective reduction of glycerol to propylene glycol.

(31) The catalysts were: Cu/H-FER: material prepared and impregnated by incipient wetness Cu on the acid form of ferrierite zeolite, which has a porous structure that allows housing the glycerol molecule. The Cu load was 6.6%. Cu/K-FER: material prepared and impregnated by incipient wetness Cu on the potassium form of zeolite ferrierite. Cu loading was 6%. Cu Chromite: Commercial material (Sud Chemie). Cu/-Al.sub.2O.sub.3: material prepared according to the technique herein described. The load of Cu was 6.6%. CuCe/-Al.sub.2O.sub.3: material prepared according to the technique herein described. The loads of Cu and Ce were 6.6 and 6.0%, respectively. CeCu/-Al.sub.2O.sub.3: material prepared according to the technique herein described. The loads of Ce and Cu were 6.0 and 6.6% respectively.

(32) The operating conditions for catalytic assessment were: 200 C., atmospheric pressure, hydrogen partial pressure of 1 atm, glycerol concentration in supply solution of 20% in weight, .sub.c 0.64 min, and LHSV 0.40 h.sup.1.

(33) FIG. 4 compares the catalytic behavior, stated as glycerol conversion (X) and selectivities to propylene glycol (S.sub.PG) and propylene glycol plus acetol (S.sub.PG+AC) for the different catalysts with Cu. Acetol, intermediate reaction product (obtained in the first dehydration step and then hydrogenated to propylene glycol), can be turned into propylene glycol, so selectivity to propylene glycos plus acetol is shown, thus allowing the comparison of materials and getting an idea of other undesirable byproducts. Bimetallic catalysts of Cu and Ce achieve the best catalytic performance, being slightly better the one impregnated in first place with Ce and then with Cu.

Examples 10-14

(34) Catalysts CuCe/-Al.sub.2O.sub.3 impregnated with loads of 6.6% of Cu and 6% of Ce were assessed with respect of the reaction of selective reduction of glycerol to propylene glycol.

(35) The operating conditions used for the catalytic assessment were: 200 C., atmospheric pressure, glycerol concentration in supply solution 20% in weight and LHSV 0.40 h.sup.1, .sub.c varied between 0.64 and 1.50 min.

(36) Table 2 shows the operating conditions modified in Examples 10-14 and identification of each one.

(37) TABLE-US-00002 TABLE 2 Operating conditions modified in examples 10-14 and identification of each one. Relation Identification Example Prereduction .sub.c (min) He/H.sub.2 in FIG. 5 10 No 0.64 0 Experience 1 11 Yes 1.50 1.33 Experience 2 12 Yes 0.82 0.27 Experience 3 13 Yes 0.64 0 Experience 4 14 Yes From From 0.27 Experience 5 0.82 to to 0 0.64

(38) FIG. 5 compares the catalytic behavior, considering conversion of glycerol (X) and selectivities to propylene glycol (S.sub.PG) and propylene glycol plus acetol (S.sub.PG+AC) for the different examples. Example 10 shows the importance and need of prereduction to reaction. Examples 11 to 14 show that an increased flow of H.sub.2 favors selectivity to propylene glycol and that a strategy of co-supply with inert may result in an additional improvement of selectivity.

Examples 15-18

(39) Catalysts CeCu/-Al.sub.2O.sub.3, impregnated with loads of 6% of Ce and 6.6% and 12% of Cu, were assessed in the selective reduction of glycerol to propylene glycol.

(40) The operating conditions used for catalytic assessment were: 200 C., atmospheric pressure, glycerol concentration in supply solution 20% in weight and LHSV 0.4 h.sup.1, .sub.c varied between 0.64 and 1.50 min.

(41) Table 3 shows the operating conditions modified in Examples 15-18 and the identification of each one.

(42) TABLE-US-00003 TABLE 3 Operating conditions modified in examples 15-18 and identification of each one. Load of Relation Identification Example Cu (%) .sub.c (min) He/H.sub.2 in FIG. 6 15 6.6 1.50 1.33 Experience 1 16 6.6 0.82 0.27 Experience 2 17 6.6 0.64 0 Experience 3 18 12.0 0.82 0.27 Experience 4

(43) FIG. 6 compares the catalytic behavior, considering conversion of glycerol (X) and selectivities to propylene glycol (S.sub.PG) and to propylene glycol plus acetol (S.sub.PG+AC) for the different examples. Glycerol conversion is completed with these catalysts, increasing the selectivity to propylene glycol by increasing the flow of hydrogen. Twice the increase of the load of Cu does not result in increased activity of the material.

Examples 13 and 17

(44) FIG. 7 compares the catalytic behavior of CuCe/-Al.sub.2O.sub.3 (Example 13) with CeCu/-Al.sub.2O.sub.3 (Example 17), considering conversion of glycerol (X) and selectivities to propylene glycol (S.sub.PG) and to propylene glycol plus acetol (S.sub.PG+AC) under similar reaction conditions. The operating conditions used were: 200 C., atmospheric pressure, glycerol concentration in supply solution 20% in weight, .sub.c 0.64 min and LHSV 0.40 h.sup.1.

(45) The sequence of impregnation is important; adding in first place Ce and then impregnation of Cu leads to a material that reaches full conversion of glycerol, as well as higher selectivity to PG and lower quantity of byproducts (difference between 100 and selectivity to PG plus acetol).

Examples 19-23

(46) Catalysts CeCu/-Al.sub.2O.sub.3, impregnated with loads of 6% of Ce and 6.6 of Cu, showing better performance in the selective reduction of glycerol to propylene glycol were assessed by changing reaction conditions.

(47) The operating conditions that were held steady for catalytic assessment were: 200 C., atmospheric pressure (hydrogen only), varying the catalyst mass, the flow of hydrogen and the glycerol concentration in the supply solution (20-50% in weight).

(48) Table 4 shows the operating conditions modified in Examples 19-23 and the identification of each one.

(49) TABLE-US-00004 TABLE 4 Operating conditions modified in examples 19-23 and the identification of each one. Identification Example .sub.c (min) LHSV (h.sup.1) in FIG. 8 19 0.64 0.40 Experience 1 20 3.21 0.08 Experience 2 21 3.21 0.20 Experience 3 22 0.64 0.40 Experience 4 23 0.13 0.40 Experience 5

(50) FIG. 8 compares the catalytic behavior, considering conversion of glycerol (X) and selectivities to propylene glycol (S.sub.PG) and to propylene glycol plus acetol (S.sub.PG+AC) for the different examples. The conversion of glycerol is higher than 96% in all cases, being affected selectivity to propylene glycol according to reaction conditions, but not the sum of propylene glycol and acetol. Therefore, by selecting the operating conditions, it can be reached 99.5% conversion, 96% selectivity to PG 96% and selectivity to propylene glycol plus acetol 99%, thus obtaining also 1% of byproducts.