Tantalum-based catalyst deposited on silica for the transformation of ethanol into butadiene

Abstract

The invention concerns a catalyst comprising at least the element tantalum, and at least one mesoporous oxide matrix that has undergone an acid wash comprising at least 90% by weight of silica before washing, the mass of the element tantalum being in the range 0.1% to 30% of the mass of said mesoporous oxide matrix.

Claims

1. A catalyst comprising at least the element tantalum, and at least one mesoporous oxide matrix based on silica that has undergone an acid wash, wherein said matrix comprises at least 90% by weight of silica before washing, wherein the mass of tantalum is in the range 0.1% to 30% of the mass of said mesoporous oxide matrix, wherein said wash is carried out by contacting with an inorganic acid that is nitric acid, sulfuric acid or hydrochloric acid, at a concentration in the range 0.05 M to 3 M, at a temperature in the range 0° C. to 120° C. and with a contact time in the range 10 min to 10 h.

2. The catalyst as claimed in claim 1, wherein said at least one mesoporous oxide matrix is an amorphous mesoporous silica with an unorganized porosity without micropores.

3. The catalyst as claimed in claim 1, wherein before washing, said at least one mesoporous oxide matrix has a specific surface area in the range 250 m.sup.2/g to 700 m.sup.2/g.

4. The catalyst as claimed in claim 1, wherein said oxide matrix is mesostructured.

5. The catalyst as claimed in claim 1, further comprising at least one element selected from the group consisting of the elements from groups 2, 3, 4 or 5 of the periodic table and mixtures thereof, the mass of said element being in the range 0.01% to 5% of the mass of said at least one mesoporous oxide matrix.

6. The catalyst as claimed in claim 5, comprising at least one element selected from the group consisting of the elements from groups 2 and 5 of the periodic table and mixtures thereof, the mass of said element being in the range 0.01% to 5% of the mass of said at least one mesoporous oxide matrix.

7. The catalyst as claimed in claim 6, comprising at least one element selected from the group consisting of the elements Ca, Ba and Nb and mixtures thereof, the mass of said element being in the range 0.01% to 5% of the mass of said at least one mesoporous oxide matrix.

8. The catalyst as claimed in claim 1, further comprising at least one element selected from the group consisting of groups 11 and 12 of the periodic table and mixtures thereof, the mass of said element being in the range 0.5% to 10% of the mass of said at least one mesoporous oxide matrix.

9. The catalyst as claimed in claim 8, further comprising at least the element Zn, the mass of said element being in the range 0.5% to 10% of the mass of said at least one mesoporous oxide matrix.

10. A process for the preparation of a catalyst as claimed in claim 1, comprising at least: a) at least one acid washing of a at least one mesoporous oxide matrix comprising at least 90% by weight of silica before washing, the percentage by weight being expressed with respect to the total mass of the at least one mesoporous oxide matrix, with at least one inorganic acid that is nitric acid, sulfuric acid or hydrochloric acid, at a concentration in the range 0.05 M to 3 M, at a temperature in the range 0° C. to 120° C. and with a contact time for said acid solution with said at least one mesoporous oxide matrix in the range 10 min to 10 h, b) at least one heat treatment at 80° C. to 300° C., for less than 72 h, of said washed matrix obtained from a) to obtain a catalyst support, c) at least one deposit of at least one metallic precursor of at least the element tantalum onto the surface of said support obtained at the end of b), and d) at least one heat treatment of solid obtained from c), said heat treatment being drying followed by calcining, wherein the drying is carried out by circulating a gas at a temperature of 80° C. to 150° C. over solid obtained from c), for 1 to 24 hours, and the calcining is carried out by circulating a gas containing oxygen, at a temperature of 450° C. to 600° C., over dried solid, for 1 to 6 h.

11. A process for the preparation of a catalyst as claimed in claim 1, comprising at least: a′) at least one step for depositing at least one metallic precursor of at least the element tantalum onto the surface of a at least one mesoporous oxide matrix comprising at least 90% by weight of silica before washing, the percentage by weight being expressed with respect to the total mass of the at least one mesoporous oxide matrix, b′) at least one heat treatment of solid obtained from a′) said heat treatment being drying followed by calcining, wherein the drying is carried out by circulating a gas at a temperature of 80° C. to 150° C. over solid obtained from a′), for 1 to 24 hours, and the calcining is carried out by circulating a gas containing oxygen, at a temperature of 450° C. to 600° C., over dried solid, for 1 to 6 h, c′) at least one acid washing of the solid obtained from b′) with at least one inorganic acid that is nitric acid, sulfuric acid or hydrochloric acid, at a concentration in the range 0.05 M to 3 M, at a temperature in the range 0° C. to 120° C., and with a contact time for said acid solution with said solid in the range 10 min to 10 h, d′) at least one heat treatment of the solid obtained from c′), wherein said heat treatment is carried out at a temperature of 80° C. to 300° C. for less than 72 h.

12. A process for the conversion of a feed comprising at least ethanol into butadiene comprising contacting said feed with a catalyst according to claim 1, at a temperature in the range 300° C. to 400° C., at a pressure in the range 0.15 to 0.5 MPa, and at a space velocity in the range 0.5 to 5 h.sup.−1.

13. The process as claimed in claim 12, wherein the temperature is in the range 320° C. to 380° C.

14. The process as claimed in claim 12, wherein the pressure is in the range 0.15 to 0.3 MPa.

15. The process as claimed in claim 12, wherein the space velocity is in the range 1 to 4 h.sup.−1.

16. A catalyst comprising at least the element tantalum, and at least one mesoporous oxide matrix based on silica that has undergone an acid wash, wherein said at least one mesoporous oxide matrix comprises at least 90% by weight of silica before washing, further comprises at least one oxide selected from the group consisting of zirconium oxide, titanium oxide, boron oxide, lanthanum oxide, cerium oxide and mixtures thereof, wherein the mass of tantalum is in the range 0.1% to 30% of the mass of said at least one mesoporous oxide matrix, wherein said wash is carried out by contacting with an inorganic acid that is nitric acid, sulfuric acid or hydrochloric acid, at a concentration in the range 0.05 M to 3 M, at a temperature in the range 0° C. to 120° C. and with a contact time in the range 10 min to 10 h.

17. A process for the preparation of a catalyst as claimed in claim 16, comprising at least: a) at least one acid washing of at least one mesoporous oxide matrix comprising at least 90% by weight of silica before washing, further comprising at least one oxide selected from the group consisting of zirconium oxide, titanium oxide, boron oxide, lanthanum oxide, cerium oxide and mixtures thereof, the percentages by weight being expressed with respect to the total mass of said at least one mesoporous oxide matrix, with at least one inorganic acid that is nitric acid, sulfuric acid or hydrochloric acid, at a concentration in the range 0.05 M to 3 M, at a temperature in the range 0° C. to 120° C. and with a contact time for said acid solution with said at least one mesoporous oxide matrix in the range 10 min to 10 h, b) at least one heat treatment of said washed matrix obtained from a) to obtain a catalyst support, c) at least one deposition of at least one metallic precursor of at least the element tantalum onto the surface of said support obtained at the end of b), and d) at least one heat treatment of solid obtained from c).

18. A process for the preparation of a catalyst as claimed claim 16, comprising at least: a′) at least one deposition of at least one metallic precursor of at least the element tantalum onto the surface of at least one mesoporous oxide matrix comprising at least 90% by weight of silica before washing, further comprising at least one oxide selected from the group consisting of zirconium oxide, titanium oxide, boron oxide, lanthanum oxide, cerium oxide and mixtures thereof, the percentages by weight being expressed with respect to the total mass of the at least one mesoporous oxide matrix, b′) at least one heat treatment of the solid obtained from a′), c′) at least one acid washing of the solid obtained from b′) with at least one inorganic acid that is nitric acid, sulfuric acid or hydrochloric acid, at a concentration in the range 0.05 M to 3 M, at a temperature in the range 0° C. to 120° C., and with a contact time for said acid solution with said solid in the range 10 min to 10 h, d′) at least one heat treatment of solid obtained from c′).

19. A catalyst consisting of the element tantalum, and at least one mesoporous oxide matrix based on silica that has undergone an acid wash, wherein said matrix comprises at least 90% by weight of silica before washing, wherein the mass of tantalum is in the range 0.1% to 30% of the mass of said at least one mesoporous oxide matrix, wherein said wash is carried out by contacting with an inorganic acid that is nitric acid, sulfuric acid or hydrochloric acid, at a concentration in the range 0.05 M to 3 M, at a temperature in the range 0° C. to 120° C. and with a contact time in the range 10 min to 10 h.

Description

EXAMPLES

Definition of Terms

(1) $\mathrm{WHSV}\left(g\text{/}{g}_{\mathrm{Ta}}\text{/}h\right)\text{:}\mathrm{WHSV}=\frac{\mathrm{mass}\mathrm{flow}\mathrm{rate}\mathrm{of}\mathrm{feed}\left(\frac{g}{h}\right)}{\mathrm{mass}\mathrm{of}\mathrm{tantalum}\left(\mathrm{gTa}\right)}$

(2) Productivity (g.sub.c/g.sub.Ta/h):

(3) $\mathrm{productivity}=\frac{\mathrm{mass}\mathrm{flow}\mathrm{rate}\mathrm{of}\mathrm{carbon}\mathrm{belonging}\mathrm{to}\mathrm{butadiene}\left(\frac{\mathrm{gc}}{h}\right)}{\mathrm{mass}\mathrm{of}\mathrm{tantalum}\mathrm{present}\mathrm{on}\mathrm{catalyst}\left(\mathrm{gTa}\right)}$

(4) Selectivity (% C):

(5) $\mathrm{selectivity}=\frac{\mathrm{mass}\mathrm{flow}\mathrm{rate}\mathrm{of}\mathrm{carbon}\mathrm{belonging}\mathrm{to}\mathrm{butadiene}\left(\frac{\mathrm{gc}}{h}\right)}{\mathrm{mass}\mathrm{flow}\mathrm{rate}\mathrm{of}\mathrm{carbon}\mathrm{belonging}\mathrm{to}\mathrm{converted}\mathrm{feed}}$

Example 1—Preparation of the Silica

(6) 12.5 mL of a solution of 68% (by volume) nitric acid are added to a solution containing 55 mL of tetraethylorthosilicate (TEOS, Si(OCH.sub.2CH.sub.3).sub.4) and 150 mL of ethanol, at ambient temperature. The mixture is stirred for 30 min. 50 mL of a 14% (by volume) ammoniacal solution is then added. The system become cloudy and a gel is formed. 19 mL of ethanol are then added to enable additional stirring for 3 hours. The final gel is filtered, washed with ethanol then dried at 100° C. for 24 hours. The obtained silica powder is then calcined in air at 550° C. for 4 hours.

(7) The characteristics of the used mesoporous oxide matrices in the examples are summarized below.

(8) TABLE-US-00001 TABLE 1 BET specific Mean pore Mesoporous surface area diameter Presence of oxide matrix (m.sup.2/g) (nm) WU (mL/g) alkali metals Merck 7734 550 6 0.8 >500 ppm Davisil 636 507 7 1 >500 ppm Davisil 646 300 15 1.2 >500 ppm Silica 690 15 1.5 <100 ppm synthesized in accordance with Example 1

Example 2—Washing of Mesoporous Oxide Matrix

(9) The various mesoporous oxide matrices described in Table 1 (granulometry: 250-500 μm) are placed on a No. 4 frit over which a washing solution is passed for 1 hour. The used volume of the solution represents around 5 times the volume occupied by the mesoporous oxide matrix. The washed solids are rinsed with an equivalent volume of distilled water for 1 additional hour, then are placed in an oven at 115° C. for at least 4 hours.

(10) The characteristics of the mesoporous oxide matrices after washing are summarized in Table 2.

(11) TABLE-US-00002 TABLE 2 BET specific Mean pore surface area diameter Pore volume Presence of Silica support (m.sup.2/g) (nm) (mL/g) alkali metals Merck 7734 570 6 0.8 <500 ppm Davisil 636 512 7 1 <500 ppm Davisil 646 320 14 1.2 <500 ppm Silica 620 13 1.5 <100 ppm synthesized in Example 1

(12) The acid wash described above induces decreasing the alkali contents to less than 1000 ppm for all of the silica supports and slightly modifies the texture of the supports.

Example 3—Dry Impregnation of Supports in Order to Deposit Tantalum

(13) Tantalum pentaethoxide (Ta(OCH.sub.2CH.sub.3).sub.5) (the amount of which is calculated from the amount of Ta to be deposited onto the support) is diluted in a solution of ethanol (the amount of which is proportional to the pore volume of the silica support). This solution is rapidly added drop by drop and mixed with the silica support until the wetness is observed on the surface thereof (dry impregnation). The solid is then placed in an atmosphere saturated with ethanol for 3 hours, then dried at 100° C. for 24 hours. The catalyst is obtained by calcining the dried solid in air at 550° C. for 4 hours.

Example 4—Dry Impregnation in Order to Deposit Niobium

(14) Ammonium niobium oxalate pentahydrate (the amount of which is calculated from the amount of Nb to be deposited on the support) is diluted to form an aqueous solution (the amount of which is proportional to the pore volume of the silica support). This solution is rapidly added drop by drop and mixed with the silica until the wetness is observed on the surface thereof (dry impregnation). The solid is then placed in an atmosphere saturated with ethanol for 3 hours, then dried at 100° C. for 24 hours. The catalyst is obtained by calcining the dried solid in air at 550° C. for 4 hours.

Example 5—Dry Impregnation in Order to Deposit Zirconium

(15) Zirconyl chloride (the amount of which is calculated from the amount of Zr to be deposited on the support) is diluted to form an aqueous solution (the amount of which is proportional to the pore volume of the silica, support). This solution is rapidly added drop by drop and mixed with the silica until the wetness is observed on the surface thereof (dry impregnation). The solid is then placed in an atmosphere saturated with ethanol for 3 hours, then dried at 100° C. for 24 hours. The catalyst is obtained by calcining the dried solid in air at 550° C. for 4 hours.

(16) Table 3 provides an overview of the prepared catalysts.

(17) TABLE-US-00003 TABLE 3 In accordance Metal and with the Washing impregnated Catalyst invention? Y/N Starting silica solution quantity A N Davisil 636 — 0.5% Ta B Y Davisil 636 HCl 1N 0.5% Ta C N Davisil 636 — 2% Ta D Y Davisil 636 HCl 0.1N 2% Ta E Y Davisil 636 HCl 1N 2% Ta F N Davisil 646 — 2% Ta G Y Davisil 646 HCl 0.1N 2% Ta H N Merck 7734 — 0.5% Ta I N Merck 7734 water 0.5% Ta J Y Merck 7734 HCl 0.1N 0.5% Ta K N Synthesized silica — 2% Ta L Y Synthesized silica HCl 0.1N 2% Ta M N Davisil 636 — 2% Nb N N Davisil 636 HCl 1N 2% Nb O N Davisil 636 — 2% Zr P N Davisil 636 HCl 1N 2% Zr Q Y 2% Ta/Davisil 636 HCl 0.1N —

(18) Description of the Catalytic Test Unit

(19) The reactor used in the examples below consists of a 20 cm long stainless steel tube with a diameter of 10 mm. The reactor is initially charged with carborundum, then with catalyst diluted in carborundum, and finally with carborundum. Carborundum is inert regarding the feed and has no influence on the catalytic results; it is used to position the catalyst in the isothermal zone of the reactor and to limit the risk of problems relating to heat and matter transfer. The temperature of the reactor is controlled with a tube furnace with three heating zones. The liquid feed (mixture of ethanol and acetaldehyde in a proportion R) is injected using a twin piston HPLC pump. The liquid stream is vaporized in the heated lines by a tracer before entering the reactor and is homogenized by passage through a static mixer. The products formed during the reaction are kept in the vapour phase so that they can be analysed in-line using gas chromatography (PONA and Carboxen 1010 capillary columns) in order to identify the hundreds of products formed as accurately as possible. The catalyst is activated in situ in nitrogen at the test temperature. The specific operating conditions are described in the following examples.

Example 6—Impact of Acid Washing on Catalysts Comprising Tantalum

(20) In this test, the ethanol/acetaldehyde ratio of the charge is fixed at 2.6 (mol/mol), the temperature at 350° C. and the pressure at 0.15 MPa. For each catalyst, the flow rate of the feed is adjusted to obtain a constant WHSV of 250 g/g.sub.Ta/h.

(21) The values for selectivity and carbon productivity are measured at this point of the operation.

(22) The impact of the acid wash on catalysts based on tantalum is demonstrated by the results summarized in Table 4.

(23) TABLE-US-00004 TABLE 4 In accordance with the Butadiene Gain in Cat- invention? productivity productivity Gain in alyst Y/N (gC/gTa/h) (%) Selectivity selectivity A N 27 — 66% — B Y 39 +44% 72% +6 C N 37 — 72% — D Y 42 +14% 74% +2 E Y 43 +16% 74% +2 F N 18 — 65% — G Y 33 +83% 69% +4 H N 11 — 57% — I N 11  0% 60% +3 J Y 40 +263%  72% +15  K N 35 — 73% — L Y 42 +20% 74% +1

(24) Acid washing of the mesoporous oxide matrix before impregnation of the element tantalum leads to increase the butadiene productivity and selectivity of the catalyst for all of the used mesoporous oxide matrices compared to the catalysts with identical tantalum contents but for which the mesoporous oxide matrix has not undergone any acid wash, or for which the mesoporous oxide matrix has only undergone a wash with water.

Example 7—Impact of Acid Wash on Catalysts Based on Niobium or Zirconium, not Containing the Element Tantalum

(25) TABLE-US-00005 TABLE 5 In accordance with the Butadiene Gain in Cat- invention? productivity productivity Gain in alyst Y/N (gC/gM/h) (%) Selectivity selectivity M N 33 — 57% — N N 40 +21% 45% −12 O N 60 — 63% — P N 72 +20% 63%  0

(26) Catalysts M and N are obtained by impregnating 2% Nb onto a Davisil 636 silica. It can be seen that acid washing the silica improves the productivity, but that the selectivity of these catalysts not containing the element tantalum is substantially degraded.

(27) Catalysts O and P are obtained by impregnating 2% Zr onto a Davisil 636 silica. An improvement in productivity is observed, but there is no effect of acid wash of the silica on the selectivity for these catalysts which do not contain the element tantalum.

(28) Thus, associating acid washing and the presence of the element tantalum results in a gain in selectivity and also in productivity for the production of 1,3-butadiene.

Example 8—Impact of the Order of the Preparation Steps for Catalysts Based on Tantalum

(29) TABLE-US-00006 In accordance with the Butadiene Gain in Cat- invention? productivity productivity Gain in alyst Y/N (gC/gM/h) (%) Selectivity selectivity C N 37 — 72% — D Y 42 +14% 74% +2 Q Y 39  +7% 74% +2

(30) Acid washing the solid after depositing the active phase based on tantalum further results in better performances. This result is surprising, because a change in the active phase would have been expected.