Catalytically active body for the synthesis of dimethyl ether from synthesis gas

Abstract

The invention relates to a catalytically active body for the synthesis of dimethyl ether from synthesis gas. In particular, the invention relates to an improved catalytically active body for the synthesis of dimethyl ether, whereby the components of the active body comprise a defined particle size distribution. Furthermore, the present invention concerns a method for the preparation of a catalytically active body, the use of the catalytically active body and a method for preparation of dimethyl ether from synthesis gas.

Claims

1. Catalytically active body for the synthesis of dimethyl ether from synthesis gas, comprising a mixture of: (A) 70-90% by weight of a methanol-active component, selected from the group consisting of copper oxide, aluminium oxide, zinc oxide, amorphous aluminium oxide, ternary oxide or mixtures thereof, (B) 10-30% by weight of an acid component, selected from the group consisting of aluminium hydroxide, aluminium oxide hydroxide, -aluminiumoxide, and combinations thereof, with 0.1-20% by weight of Niobium, Tantalum, or Boron, related to component (B), or mixtures thereof, (C) 0-10% by weight of at least one additive, whereby the sum of the components (A), (B) and (C) is in total 100% by weight; wherein the component (A) has a particle size distribution characterized by a D-10 value of 5-140 m, a D-50 value of 40-300 m, and a D-90 value of 180-800 m, whereby the component (B) has a particle size distribution characterized by a D-10 value of 5-140 m, a D-50 value of 40-300 m, and a D-90 value of 180-800 m and the article size distribution of components (A) and (B) being maintained in the catalytically active body.

2. Catalytically active body according to claim 1, wherein component (B) is aluminium oxide hydroxide and -aluminiumoxide in a ratio of 3:7 to 6:4.

3. Catalytically active body according to claim 1, characterized in that component (A) comprises 50-80% by weight of copper oxide, 15-35% by weight of ternary oxide and 15-35% by weight of zinc oxide and the sum of which is in total 100% by weight.

4. Catalytically active body according to claim 1, characterized in that component (A) comprises 50-80% by weight of copper oxide, 2-8% by weight of amorphous aluminium oxide and 15-35% by weight of zinc oxide and the sum of which is in total 100% by weight.

5. Catalytically active body according to claim 1, wherein component (A) comprises 50-80% by weight of copper oxide, 2-8% by weight of aluminium oxide and 15-35% by weight of zinc oxide and the sum of which is in total 100% by weight.

6. Catalytically active body according to claim 1, wherein component (B) has a surface area from 70-270 m.sup.2/g with a pore volume in the range from 0.35-1.45 ml/g.

7. Catalytically active body according to claim 1, wherein component (B) comprises boehmite.

8. Catalytically active body according to claim 1, wherein the catalytically active body is a pellet with a size in the range from 11 mm to 1010 mm.

9. Method for the preparation of a catalytically active body, comprising the step: d) preparing a physical mixture comprising: (A) 70-90% by weight of a methanol-active component, selected from the group consisting of copper oxide, aluminium oxide, zinc oxide, amorphous aluminium oxide, ternary oxide or mixtures thereof, (B) 10-30% by weight of an acid component, selected from the group consisting of aluminium hydroxide, aluminium oxide hydroxide and/or -aluminiumoxide with 0.1-20% by weight of Niobium, Tantalum, Phosphorus or Boron, related to component (B), or mixtures thereof, (C) 0-10 Gew.-% by weight of at least one additive, whereby the sum of the components (A), (B) and (C) is in total 100% by weight; wherein the component (A) has a particle size distribution characterized by a D-10 value of 5-140 m, a D-50 value of 40-300 m, and a D-90 value of 180-800 m, whereby the component (B) has a particle size distribution characterized by a D-10 value of 5-140 m, a D-50 value of 40-300 m, and a D-90 value of 180-800 m and the particle size distribution of components (A) and (B) being maintained in the catalytically active body.

10. Method for the preparation of a catalytically active body according to claim 9, further comprising: a) precipitation of a salt of copper, zinc or aluminum or a mixture thereof, b) calcination of the product obtained in step a), c) calcination of a salt comprising Niobium, Tantalum, Phosphorus or Boron with a mixture of aluminium hydroxide, aluminium oxide hydroxide and/or -aluminiumoxide.

11. Method for the preparation of a catalytically active body according to claim 9, wherein a pellet is formed.

12. Method for the preparation of a catalytically active body according to claim 9, wherein the components (A) and (B) are independently pressed through at least one sieve, whereby the sieve exhibits a mesh size from 0.005 to 5 mm in order to obtain a particle size distribution characterized by a D-10 value of 5-140 m, a D-50 value of 40-300 m, and a D-90 value of 180-800 m.

13. Method for the preparation of a catalytically active body according to claim 9, wherein at least three different sieves are used, whereby the components (A) and (B) are pressed in direction from the sieve with the biggest mesh size to the sieve with the smallest mesh size.

14. Method for the preparation of a catalytically active body according to claim 9, wherein in step a) at least a part of the component (A) is prepared by precipitation reaction and/or calcination.

15. Method for the preparation of a catalytically active body according to claim 9, whereby at least one part of component (A) is precipitated and whereby at least another part of component (A), which is not subjected to the first precipitation, is added to the precipitate.

16. Method for the preparation of a catalytically active body according to claim 9, wherein the method further comprises adding a mixture of hydrogen and nitrogen to component (A) and/or (B).

17. Method for the preparation of dimethyl ether from synthesis gas comprising: f) reducing the catalytically active body according to claim 1; and g) contacting the catalytically active body in a reduced form with hydrogen and at least one of carbon monoxide or carbon dioxide.

Description

A) SYNTHESIS OF THE METHANOL-ACTIVE COMPOUNDS

1. Example

(1) Two solutions are prepared for the precipitation of the components:

(2) Solution 1:

(3) A solution of 1.33 kg copper nitrate, 2.1 kg zinc nitrate and 0.278 kg aluminium nitrate are solved in 15 L water.

(4) Solution 2:

(5) 2.344 kg sodium bicarbonate is dissolved in 15 L water.

(6) Both solutions are separately heated to 90 C., followed by the fast addition of solution 1 to solution 2 within 1-2 minutes under stirring. Afterwards 15 min is stirred and the precipitation is filtered and washed with water till it is free of nitrates. The filter cake is dried at 110 C. and is calcinated for 4 h at 270 C. under nitrogen atmosphere. The metal content of the catalyst is in atom-%: Cu 38.8; Zn 48.8 and Al 12.9.

2. Example

(7) Two solutions are prepared for the precipitation of the components:

(8) Solution 1:

(9) A solution of 2.66 kg copper nitrate, 1.05 kg zinc nitrate and 0.278 kg aluminium nitrate are solved in 15 L water.

(10) Solution 2:

(11) 2.344 kg sodium bicarbonate is dissolved in 15 L water.

(12) The same procedure as described in the 1. Example, whereby the metal content of the catalyst is in atom %: Cu 61.6; Zn 28.1 and Al 10.9.

3. Example

Preparation of Me30

(13) i. Precipitation:

(14) A sodium bicarbonate solution (20%) is prepared, whereby 11 kg sodium bicarbonate is dissolved in 44 kg demineralised water. Also a Zn/Al-solution is prepared consisting of 6.88 kg zinc nitrate and 5.67 kg aluminium nitrate and 23.04 kg water. Both solutions are heated to 70 C. A template filled with 12.1 L demineralised water is also heated to 70 C. Both solutions are added in parallel to the template at a pH=7, till the Zn/Al-solution is consumed. Afterwards 15 h is stirred at a pH=7. After this the suspension is vacuumed and washed to a content of sodium oxide <0.10% and the water is free of nitrate. The product is dried for 24 h at 120 C. and calcinated for 1 h at 350 C. under air flow.

(15) ii. Precipitation:

(16) A sodium bicarbonate solution (20%) is prepared, whereby 25 kg sodium bicarbonate is dissolved in 100 kg demineralised water. Also a Cu/Zn-nitrate solution is prepared consisting of 26.87 kg copper nitrate and 5.43 kg zinc nitrate and 39 kg water. Both solutions are heated to 70 C. After the Cu/Zn-nitrate solution has reached a temperature of 70 C., the product of the 1.precipitation is added slowly and the pH-value is adjusted to pH=2. Also a solution of nitric acid (65%) is provided (650 g conc. HNO.sub.3 and 350 g demineralised water). A template filled with 40.8 L demineralised water is also heated to 70 C. Both solutions (sodium bicarbonate and Cu/Zn-nitrate solution) are added in parallel to the template at a pH=6.7, till the Cu/Zn-nitrate solution is consumed. Afterwards 10 h is stirred whereby the pH-value is adjusted to pH=6.7 with the nitric acid (65%). After this the suspension is vacuumed and washed to a content of sodium oxide <0.10% and the water is free of nitrate. The product is dried for 72 h at 120 C. and calcinated for 3 h at 300 C. under air flow. After cooling to room temperature the material is ready for use.

B) SYNTHESIS OF ACID COMPOUNDS

Synthesis of an Al2O3/AlOOH-Mixture Doped with Niobium (0.255% by Weight)

(17) An impregnated solution is prepared that consists of 0.5 g ammonium niobate(V) oxalate and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Niobium (1.02% by Weight)

(18) An impregnated solution is prepared that consists of 2 g ammonium niobate(V) oxalate and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Niobium (2.04% by Weight)

(19) An impregnated solution is prepared that consists of 4 g ammonium niobate(V) oxalate and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Niobium (3.06% by Weight)

(20) An impregnated solution is prepared that consists of 6 g ammonium niobate(V) oxalate and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Niobium (8.16% by Weight)

(21) An impregnated solution is prepared that consists of 16 g ammonium niobate(V) oxalate dissolved in 100 ml water. An 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite) is added in portions under stirring and afterwards 10 min stirred. In the following step the suspension is exhausted by a Nutsche Filter. Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Samarium (2.04% by Weight)

(22) An impregnated solution is prepared that consists of 2.61 g samarium(III)-acetate hydrate and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room tem

Synthesis of an Al2O3/AlOOH-Mixture Doped with Tin (2.04% by Weight)

(23) An impregnated solution is prepared that consists of 2.39 g tin(II)-acetate and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Tungsten (2.04% by Weight)

(24) An impregnated solution is prepared that consists of 1.25 g ammonium metatungstate hydrate and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Yttrium (2.04% by Weight)

(25) An impregnated solution is prepared that consists of 3.59 g yttrium(III) acetate hydrate and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Cerium (2.04% by Weight)

(26) An impregnated solution is prepared that consists of 2.72 g cerium(III) acetate hydrate and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Boron (2.04% by Weight)

(27) An impregnated solution is prepared that consists of 6.86 g boric acid and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of an Al2O3/AlOOH-Mixture Doped with Gallium (2.04% by Weight)

(28) An impregnated solution is prepared that consists of 6.32 g gallium(III) acetylacetonat and 27.4 ml demineralised water. With spray-watering this solution is applied onto 40 g Al.sub.2O.sub.3/AlOOH-mixture (crushed extrudates consisting of 60% gamma-Al.sub.2O.sub.3 and 40% boehmite). Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of Boehmite Doped with Niobium (2.04% by Weight on Plural SCF 55)

(29) An impregnated solution is prepared that consists of 4.00 g ammonium niobate(V) oxalate and 20.9 ml demineralised water. With spray-watering this solution is applied onto 40 g Plural SCF 55. Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

Synthesis of Al2O3 Doped with Niobium (2.04% by Weight on Pluralox SCF A230)

(30) An impregnated solution is prepared that consists of 4.00 g ammonium niobate(V) oxalate and 25.6 ml demineralised water. With spray-watering this solution is applied onto 40 g Pluralox SCF A230. Afterwards this material is dried for 12 h and 90 C. in the drying oven. After drying the material is calcinated in a rotating tube for 3 h at 450 C. under nitrogen atmosphere (30 nl/h). The heating rate is 5 C./min. After cooling to room temperature the material is ready for use.

C) PREPARATION OF THE FINAL CATALYTICALLY ACTIVE BODY

(31) The methanol-active compound and the acid compound are compacted separately in a tablet press and/or pelletizing machine. The obtained molding (diameter=ca, 25 mm, height=ca, 2 mm), is squeezed through sieves with an appropriate mesh size, so that the desired split fraction is obtained. From both fractions the proper quantity is weight in (9/1, 8/2, or 7/3 methanol-active/acidic compound) and mixed in a mixing machine (Heidolph Reax 2 or Reax 20/12). If required the compound C is added in advance.

D) TESTING CONDITIONS FOR NON-PELLETIZED MIXTURES

(32) The catalytically active body (5 cm.sup.3 by volume) is incorporated in a tubular reactor (inner diameter 0.4 cm, bedded in a metal heating body) on a catalyst bed support consisting of alumina powder as layer of inert material and is pressure-less reduced with a mixture of 1 Vol.-% H.sub.2 and 99 Vol.-% N.sub.2. The temperature is increased in intervals of 8 h from 150 C. to 170 C. and from 170 C. to 190 C. and finally to 230 C. At a temperature of 230 C. the synthesis gas is introduced and heated within 2 h up to 250 C. The synthesis gas consists of 45% H.sub.2 and 45% CO and 10% inert gas (argon). The catalytically active body is run at an input temperature of 250 C., GHSV of 2400 h.sup.1 and a pressure of 50 bar.

E) TESTING CONDITIONS FOR PELLETIZED MIXTURES

(33) Tests for pelletized materials are conducted in a similar test rick compared to the setup described above for non-pelletized materials using the same routine. Only no_tubular reactor with an inner diameter of 0.4 cm is used but a tubular reactor having an inner diameter of 3 cm. Tests for pelletized materials are done with a catalyst volume of 100 cm.sup.3.

(34) Results:

(35) According to table 1 the different mixtures are listed.

(36) Methanol-Active Component:

(37) Me30: Consists of 70% by weight of CuO, 5.5% by weight Al.sub.2O.sub.3 and 24.5% by weight of ZnO.

(38) In the following table 1 the results are presented. Me30 and D10-21 (mixture from boehmite and gamma-Alox in a ratio of 4:6), Pluralox and Plural are used.

(39) The compositions of the catalytically active body (the corresponding D-10, D-50, and D-90 values of Me30 and of the acid component are presented in table 2) show different CO-conversions. The comparison experiments C1 to C9 showing a lower turnover, whereby the inventive experiments V1 to V9 showing an increased value.

(40) TABLE-US-00001 TABLE 1 CO- Mixture Me30: conversion Nr. (Z = acide component) Z: (doped)acid component [%] S(MeOH) S(DME) S(CO.sub.2) S(Others) C1 Me30:Z (4:1) D10-21 (Mixture from Boehmite and gamma-Alox (40:60)) 49.00 32.42 30.96 35.72 0.90 C2 Me30:gamma Alox (4:1) Puralox (gamma Alox) 59.60 9.09 45.30 45.36 0.24 C3 Me30:Boehmit (4:1) Pural (Boemit) 12.56 97.00 0.47 0.00 2.53 V1 Me30:Z (4:1) Ammonium niobate(V) oxalate on D10-21 (0.255 82.86 4.37 47.86 47.43 0.34 Gew % Nb) V2 Me30:Z (4:1) Ammonium niobate(V) oxalate on D10-21 (1.02% by 78.54 7.14 46.03 46.61 0.22 weight Nb) V3 Me30:Z(4:1) Ammonium niobate(V) oxalate on D10-21 (2.04% by 81.44 2.62 48.25 49.06 0.06 weight Nb) V4 Me30:Z (4:1) Ammonium niobate(V) oxalate on D10-21 (3.06% by 81.20 6.50 46.24 46.95 0.32 weight Nb) V5 Me30:Z (4:1) Ammonium niobate(V) oxalate on D10-21 (8.16% by 82.91 4.42 47.47 47.68 0.44 weight Nb) C4 Me30:Z (4:1) Samarium(III) acetat hydrate on D10-21 (2.04% by 67.86 21.16 38.65 39.74 0.45 weight Sm) C5 Me30:Z (4:1) Tin(II) acetat on D10-21 (2.04% by weight Sn) 67.86 15.53 41.81 42.29 0.38 C6 Me30:Z (4:1) Ammonium metatungstate hydrate on D10-21 (2.04% 67.80 17.74 40.81 41.02 0.43 by weight W) C7 Me30:Z (4:1) Yttrium(III) acetate hydrate on D10-21 (2.04% by 59.66 28.27 34.28 36.68 0.77 weight Y) C8 Me30:Z (4:1) Cerium(III) acetate hydrate on D10-21 (2.04% by 53.67 30.58 33.30 35.38 0.74 weight Ce) V6 Me30:Z (4:1) Boric acid D10-21 (2.04% by weight B) 82.14 4.33 48.45 46.86 0.35 C9 Me30:Z (4:1) Gallium(III)acetylacetonate on D10-21 (2.04% by 41.62 4.94 49.41 45.22 0.44 weight Ga) V7 Me30:Z (4:1) Tantal(V)nitrat on D10-21 (2.04% by weight Ta) 77.59 3.57 49.57 46.49 0.37 V8 Me30:Z (4:1) Ammonium niobate(V) oxalate on Pural (2.04% by 79.11 6.61 46.68 46.34 0.36 weight Nb) V9 Me30:Z (4:1) Ammonium niobate(V) oxalate on Puralox (2.04% by 79.03 5.53 47.48 46.80 0.19 weight Nb) All gaseous streams were analyzed via online-GC. Argon was used as internal standard to correlate in and off gas streams. CO conversion is given as follows: (CO.sub.in (CO.sub.out * Argon.sub.in/Argon.sub.out))/CO.sub.in * 100% S(MeOH) = Volume (MeOH) in product stream/Volume (MeOH + DME + CO.sub.2 + Others without hydrogen and CO) in product stream * 100% S(DME) = Volume (DME) in product stream/Volume (MeOH + DME + CO.sub.2 + Others without hydrogen and CO) in product stream * 100% S(CO.sub.2) = Volume (CO.sub.2) in product stream/Volume (MeOH + DME + CO.sub.2 + Others without hydrogen and CO) in product stream * 100% S(Others) = Volume (Others) in product stream/Volume (MeOH + DME + CO.sub.2 + Others without hydrogen and CO) in product stream * 100% Others are compounds that are formed out of H.sub.2 and CO in the reactor that are not MeOH, DME, or CO.sub.2.

(41) TABLE-US-00002 TABLE 2 D-10 D-50 D-90 [m] [m] [m] Me30 5.42 46.57 189.14 D10-21 (Mixture from Boehmite and gamma- 7.53 114.87 189.23 Alox) Puralox (gamma Alox) 5.06 57.96 396.86 Pural (Boehmite) 6.33 79.13 243.57 Ammonium niobate(V) oxalate on D10-21 11.51 65.55 217.44 (0.255 Gew % Nb) Boric acid D10-21 (2.04 Gew % B) 8.49 98.36 197.83 Tantal(V)nitrat on D10-21 (2.04 Gew % Ta) 13.98 131.69 345.25