Alumina Bismuth Catalyst Support and Method for Its Production

Abstract

The invention provides for a method to prepare an alumina catalyst support comprising bismuth for emission control applications, to an alumina catalyst support prepared according to the method of the invention and to an alumina catalyst support comprising bismuth and having a specific crystallinity value that leads to improved technical effects.

Claims

1. A method to prepare an alumina bismuth catalyst support, the method comprising the steps of: i) providing an aluminum containing composition, wherein the aluminum containing composition comprises boehmite or a silica containing aluminum oxide; ii) providing a bismuth aqueous solution, the bismuth aqueous solution comprising a bismuth salt and a base comprising nitrogen and having a pH value of between 4 and 9; iii) contacting the aluminum containing composition with the bismuth aqueous solution to form an aluminum bismuth intermediate, wherein the contacting is carried out: in case of process step i) involving the aluminum containing composition comprising boehmite by mixing the aluminum containing composition in dried powder form or in the form of a suspension with the bismuth aqueous solution to form an aluminum bismuth intermediate, or in case of process step i) involving the aluminum containing composition comprising silica containing aluminum oxide by impregnating the aluminum containing composition in dried powder form with the bismuth aqueous solution to form an aluminum bismuth intermediate; and iv) calcining the aluminum bismuth intermediate to form an alumina bismuth catalyst support.

2. The method of claim 1, wherein the aluminum containing composition further comprises at least one dopant, wherein the at least one dopant comprises oxides or water soluble salts of alkaline earth metals, transition metals, rare-earth metals or mixtures thereof.

3. The method of claim 1, wherein the aluminum containing composition comprising boehmite further comprises silica.

4. The method of claim 1, wherein where the aluminum containing composition comprises silica, the silica content is between 1 wt.-% and 40 wt. % based on the oxide mass of silica and the aluminum oxide, aluminum oxide hydroxide and/or aluminum trihydroxide.

5. The method of claim 1, wherein the suspension includes the aluminum containing composition and at least water.

6. The method of claim 1, wherein impregnation of the aluminum containing composition comprises incipient wetness impregnation.

7. The method of claim 1, wherein the aluminum oxide in the silica containing aluminum oxide composition is or comprises one or more transition aluminas.

8. The method of claim 1, wherein when the aluminum containing composition comprising boehmite provided in dried powder form or in the form of a suspension is mixed with the bismuth aqueous solution the method comprises the further step of drying the aluminum bismuth intermediate to form a dried aluminum bismuth intermediate that will then be calcined.

9. The method of claim 1, wherein the aluminum bismuth intermediate or the dried aluminum bismuth intermediate is calcined at a temperature of between 500° C. and 1000° C. for a period of at least 0.5 hours.

10. The method of claim 1, wherein the base comprising nitrogen is ammonia.

11. An alumina bismuth catalyst support obtainable according to the method of claim 1.

12. An alumina bismuth catalyst support comprising: i) at least 80 wt.-% of a transitional alumina based material; and ii) between 1 wt.-% and 20 wt.-% of a bismuth oxide, characterized by a crystallinity value CBi below 10, wherein the crystallinity value CBi is determined from X-ray diffraction pattern of the alumina bismuth catalyst support using Cu K alpha radiation and using equation 1
C.sub.Bi=[(I.sub.28−I.sub.24)/(I.sub.67−I.sub.72)]/m.sub.Bi  (equation 1) with I.sub.28: Intensity of the reflex around 28° I.sub.24: Intensity of baseline near the reflex around 24° I.sub.67: Intensity of the reflex around 67° I.sub.72: Intensity of baseline near the reflex around 72° m.sub.Bi: mass of Bi.sub.2O.sub.3/(mass of Bi.sub.2O.sub.3+mass of transition alumina based material”.

13. The alumina bismuth catalyst support of claim 12, wherein the transition alumina based material comprises alumina, and optionally in addition silica and/or dopants.

14. The alumina bismuth catalyst support of claim 11 further characterized by at least one of the following characteristics: a) a BET specific surface area between 50 and 300 m.sup.2/g; and/or b) a pore volume of between 0.1 and 1.5 ml/g, wherein the pore volume is measured with N.sub.2 physisorption according to DIN 66131.

15. An alumina bismuth catalyst support of claim 12, wherein the alumina bismuth catalyst support is obtainable according to the method comprising the steps of: i) providing an aluminum containing composition, wherein the aluminum containing composition comprises boehmite or a silica containing aluminum oxide; ii) providing a bismuth aqueous solution, the bismuth aqueous solution comprising a bismuth salt and a base comprising nitrogen and having a pH value of between 4 and 9; iii) contacting the aluminum containing composition with the bismuth aqueous solution to form an aluminum bismuth intermediate, wherein the contacting is carried out: in case of process step i) involving the aluminum containing composition comprising boehmite by mixing the aluminum containing composition in dried powder form or in the form of a suspension with the bismuth aqueous solution to form an aluminum bismuth intermediate, or in case of process step i) involving the aluminum containing composition comprising silica containing aluminum oxide by impregnating the aluminum containing composition in dried powder form with the bismuth aqueous solution to form an aluminum bismuth intermediate; and iv) calcining the aluminum bismuth intermediate to form an alumina bismuth catalyst support.

16. (canceled)

17. The alumina bismuth catalyst support of claim 12 further characterized by at least one of the following characteristics: a) a BET specific surface area between 50 and 300 m.sup.2/g; and/or b) a pore volume of between 0.1 and 1.5 ml/g, wherein the pore volume is measured with N.sub.2 physisorption according to DIN 66131.

Description

[0050] The invention will now be described with reference to the following non-limiting examples and Figures in which:

[0051] FIG. 1 is a powder XRD of the composition obtained in Example 1 and Example 2 compared to Comparative Examples 1-3 showing the difference in crystallinity of Bi.sub.2O.sub.3; and

[0052] FIG. 2 is a powder XRD of the composition obtained in Example 3 compared to Comparative Example 4, together with a simulated XRD pattern of Bi.sub.2O.sub.3 showing the difference in crystallinity of Bi.sub.2O.sub.3.

EXAMPLES

Example 1 (Aluminum Containing Composition Comprising Boehmite and Silica)

[0053] A bismuth oxide doped silica-alumina with 3 wt.-% Bi.sub.2O.sub.3 was prepared according to the present invention.

[0054] A Bi-Citrate solution was prepared by adding 516 g Bi-Citrate to 1.7 kg H.sub.2O. 190 g of a 25 wt.-% NH.sub.3 solution was added to obtain a clear solution with pH 7. The Bi-Citrate solution was added to an alumina suspension containing boehmite and silica in a 95:5 weight ratio calculated as per the oxides (SIRAL 5). The mixture was spray dried and calcined at 950° C. for 3 h.

Example 2 (Aluminum Containing Composition Comprising Silica Containing Aluminum Oxide)

[0055] A bismuth oxide doped silica-alumina with 3 wt.-% Bi.sub.2O.sub.3 was prepared according to the present invention.

[0056] A Bi-Citrate solution was prepared by adding 12.2 g Bi-Citrate to 148 g H.sub.2O. 4.1 g of a 25 wt.-% NH.sub.3 solution was added to obtain a clear solution with pH 7. The Bi-Citrate solution was impregnated by incipient wetness impregnation on 234 g of a silica-alumina, SIRALOX 5, containing 5 wt.-% SiO.sub.2 (in dried powder form). The product was calcined at 550° C. for 3 h.

Comparative Example 1

[0057] A bismuth oxide doped silica-alumina with 3 wt.-% Bi.sub.2O.sub.3 was prepared according to U.S. Pat. No. 7,611,680 B2 Example 2.

[0058] A solution of 1 g Bi-Citrate in 7.7 g water with a pH value of 2.8 was prepared. This solution was intensively mixed for 15 minutes with 19.7 g of a silica-alumina, SIRAL 5, containing 5 wt.-% SiO.sub.2, dried at 120° C., ground into a fine powder and calcined at 500° C. for 2 h.

Comparative Example 2

[0059] A bismuth oxide doped lanthanum doped alumina with 4 wt.-% Bi.sub.2O.sub.3 was prepared according to U.S. Pat. No. 7,611,680 B2 Example 3.

[0060] To 2 g of a La doped alumina was added a solution of 0.111 g Bi-acetate in 4 ml H.sub.2O and 1 ml glacial acetic acid. The resulting paste was mechanically mixed at room temperature for 60 minutes, dried at 130° C. for 2.5 h, ground into a fine powder, and calcined at 500° C. for 1 h. The material contained 3 wt. % La.sub.2O.sub.3.

Comparative Example 3

[0061] A bismuth oxide doped silica-alumina with 3 wt.-% Bi.sub.2O.sub.3 was prepared according to WO 2017/064498 Example 3.

[0062] An aqueous suspension of 40 g silica-alumina containing 5 wt.-% SiO.sub.2 was wet-milled to a d90 of 19 μm. Then a solution of 2.1 g bismuth-nitrate in diluted nitric acid was added. The mixture was spray dried and calcined at 500° C.

Example 3 (Aluminum Containing Composition Comprising Silica Containing Aluminum Oxide)

[0063] A Bi-Citrate solution was prepared by adding 3.7 g Bi-Citrate to 16, 1 g H.sub.2O. 1.2 g of a 25 wt.-% NH.sub.3 solution was added to obtain a clear solution with pH 7.

[0064] The Bi-Citrate solution was impregnated on 18 g of a dried powder of silica-alumina, SIRALOX 5, containing 5 wt.-% SiO.sub.2. The product was calcined at 550° C. for 3 h.

Comparative Example 4

[0065] A bismuth oxide doped silica-alumina with 10 wt.-% Bi.sub.2O.sub.3 was prepared according to WO 2017/064498 Example 15.

[0066] 3.88 g Bi-nitrate pentahydrate were dissolved in 2M nitric acid and impregnated on 18 g of a silica-alumina containing 5 wt.-% SiO.sub.2. The product was dried at 105° C. and calcined at 500° C.

[0067] The results are summarized in FIGS. 1 and 2 and Table 1. The compositions prepared according to the present invention are characterized by substantially smaller crystallinity values regarding the Bi.sub.2O.sub.3 when compared to the compositions prepared according to the prior art.

TABLE-US-00001 TABLE 1 mBi.sub.2O.sub.3 in Bi.sub.2O.sub.3 crystallinity Examples wt. % value C.sub.Bi Example 1 3 1 Example 2 3 1 Comparative Example 1 3 130 Comparative Example 2 4 108 Comparative Example 3 3 18 Example 3 10 2 Comparative Example 4 10 14