A PARTICULATE MAGNESIUM ION-COMPRISING MATERIAL FOR NOX UPTAKE

Abstract

The present invention relates to a process for taking up one or more nitrogen oxide(s) from a medium using at least one particulate magnesium ion-comprising material, a particulate magnesium ion-comprising material obtained by the process as well as an adsorbing material comprising said at least one particulate magnesium ion-comprising material and the use of at least one particulate magnesium ion-comprising material having a BET specific surface area as measured by the BET nitrogen method in the range from 4 to 400 m.sup.2/g for taking up one or more nitrogen oxide(s) from a gaseous and/or aero

Claims

1. A process for taking up one or more nitrogen oxide(s) from a medium, the process comprising the following steps: a) providing a gaseous and/or aerosol medium comprising one or more nitrogen oxide(s), b) providing at least one particulate magnesium ion-comprising material having a BET specific surface area as measured by the BET nitrogen method in the range from 4 to 400 m.sup.2/g, and c) contacting the gaseous and/or aerosol medium of step a) with the at least one particulate magnesium ion-comprising material of step b) for taking up at least a part of the one or more nitrogen oxide(s) from the gaseous and/or aerosol medium onto the surface and/or into the pores of the at least one particulate magnesium ion-comprising material, wherein contacting step c) is carried out at a temperature ranging from 10 to +150 C.

2. The process according to claim 1, wherein the gaseous and/or aerosol medium of step a) is selected from the group comprising air, ambient air, exhaust fumes, factory fumes, household fumes, industrial fumes, vehicle exhausts, fog, smoke and mixtures thereof.

3. The process according to claim 1, wherein the gaseous and/or aerosol medium comprises one or more nitrogen oxide(s) selected from the group comprising NO, NO.sub.2, NO.sub.2.sup., NO.sub.3, N.sub.2O, N.sub.4O, N.sub.2O.sub.3, N.sub.2O.sub.4, N.sub.2O.sub.5, N.sub.4O.sub.6, and mixtures thereof.

4. The process according to claim 1, wherein the gaseous and/or aerosol medium comprises the one or more nitrogen oxide(s) with partial pressures of up to 200 mbar.

5. The process according to claim 1, wherein the at least one particulate magnesium ion-comprising material of step b) is provided in form of a powder, a pellet, a granulated powder, a suspension, a column, a cartridge, a paint, a coating, a filter material, a gabion, or a building material.

6. The process according to claim 1, wherein the at least one particulate magnesium ion-comprising material of step b) is selected from the group comprising a magnesium hydroxide-comprising material, a magnesium carbonate-comprising material, a magnesium oxide-comprising material and mixtures thereof.

7. The process according to claim 1, wherein the at least one particulate magnesium ion-comprising material of step b) has i) a volume median particle size d.sub.50 of <30 mm, determined by laser diffraction, and/or ii) a BET specific surface area as measured by the BET nitrogen method of from 4 to 200 m.sup.2/g, and/or iii) a particle size distribution d.sub.98/d.sub.50 of 2, determined by laser diffraction.

8. The process according to claim 1, wherein the at least one particulate magnesium ion-comprising material of step b) has a moisture content of at least 0.001 mg/m.sup.2.

9. The process according to claim 1, wherein contacting step c) is carried out at a temperature ranging from 0 to +80 C.

10. The process according to claim 1, wherein the process comprises a further step d) of washing the at least one particulate magnesium ion-comprising material obtained in step c) in one or more steps such as to remove the one or more nitrogen oxide(s) and/or reaction products thereof from the surface and/or from the pores of the at least one particulate magnesium ion-comprising material.

11. The process according to claim 10, wherein the washing step d) is carried out by contacting the at least one particulate magnesium ion-comprising material obtained in step c) with water, an organic solvent or mixtures thereof.

12. The process according to claim 10, wherein the at least one particulate magnesium ion-comprising material obtained in washing step d) is re-used in process step b) as the at least one particulate magnesium ion-comprising material.

13. A particulate magnesium ion-comprising material obtained by a process for taking up one or more nitrogen oxide(s) from a gaseous and/or aerosol medium according to claim 1.

14. An adsorbing material comprising at least one particulate magnesium ion-comprising material having a BET specific surface area as measured by the BET nitrogen method in the range from 4 to 400 m.sup.2/g or as defined in claim 5.

15-16. (canceled)

17. The process according to claim 3, wherein the one or more nitrogen oxide(s) is selected from NO and NO.sub.2.

18. The process according to claim 4, wherein the gaseous and/or aerosol medium comprises the one or more nitrogen oxide(s) with partial pressures of up to 100 mbar.

19. The process according to claim 5, wherein (i) the suspension is an aqueous suspension or suspension in organic solvents and/or (ii) the gabion is placed next to a motorway or a waste incineration plant.

20. The process according to claim 6, wherein the at least one particulate magnesium ion-comprising material of step b) is selected from the group comprising a natural hydromagnesite, a precipitated hydromagnesite, upsalite, magesite, dolomite, half-burned dolomite, natural magnesium oxide, synthetic magnesium oxide, natural magnesium hydroxide, and synthetic magnesium hydroxide.

21. The process according to claim 7, wherein the at least one particulate magnesium ion-comprising material of step b) has i) a volume median particle size d.sub.50 of from about 40 nm to about 2,000 m; and/or ii) a BET specific surface area as measured by the BET nitrogen method of from about 6 m.sup.2/g to about 175 m.sup.2/g; and/or iii) a particle size distribution d.sub.98/d.sub.50 of from about 3.2 to about 8.0, determined by laser diffraction.

22. The process according to claim 9, wherein contacting step c) is carried out at a temperature ranging from +10 to +55 C.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0212] FIG. 1 shows the adsorption of NO.sub.2 for inventive magnesium ion-comprising materials compared to a calcium ion-comprising material.

[0213] FIG. 2 shows the adsorption of NO for inventive magnesium ion-comprising materials compared to a calcium ion-comprising material.

[0214] The scope and interest of the invention may be better understood on basis of the following examples which are intended to illustrate embodiments of the present invention. However, they are not to be construed to limit the scope of the claims in any manner whatsoever.

EXAMPLES

1. Measurement Methods

[0215] In the following the measurement methods implemented in the examples are described.

Particle Size Distribution of a Particulate Material:

[0216] Volume based median particle size d.sub.50 (vol) and the volume based top cut particle size d.sub.98 (vol) as well as the volume based particle size d.sub.10 (vol) were evaluated in a wet unit using a Malvern Mastersizer 3000 Laser Diffraction System (Malvern Instruments Plc., Great Britain). The d.sub.50 (vol), d.sub.98 (vol) or d.sub.10 (vol) value indicates a diameter value such that 50% or 98% or 10% by volume, respectively, of the particles have a diameter of less than this value. The raw data obtained by the measurement was analysed using the Mie theory, with a particle refractive index of 1.57 and an absorption index of 0.005. The methods and instruments are known to the skilled person and are commonly used to determine particle size distributions of fillers and pigments.

[0217] The weight based median particle size d.sub.50 (wt) was measured by the sedimentation method, which is an analysis of sedimentation behaviour in a gravimetric field. The measurement was made with a Sedigraph 5100 or 5120 of Micromeritics Instrument Corporation, USA. The method and the instrument are known to the skilled person and are commonly used to determine particle size distributions of fillers and pigments. The measurement was carried out in an aqueous solution of 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and sonicated.

[0218] If not otherwise indicated in the following example section, the volume particle sizes were evaluated in a wet unit using a Malvern Mastersizer 3000 Laser Diffraction System (Malvern Instruments Plc., Great Britain).

BET Specific Surface Area of a Particulate Material

[0219] Throughout the present document, the specific surface area (in m.sup.2/g) of the particulate material is determined using the BET method (using nitrogen as adsorbing gas), which is well known to the skilled man (ISO 9277:2010). The total surface area (in m.sup.2) of the particulate material is then obtained by multiplication of the specific surface area and the mass (in g) of the particulate material prior to treatment.

Solids Content

[0220] The suspension solids content (also known as dry weight) was determined using a Moisture Analyser MJ33 from the company Mettler-Toledo, Switzerland, with the following settings: drying temperature of 150 C., automatic switch off if the mass does not change more than 1 mg over a period of 30 sec, standard drying of 5 to 20 g of suspension.

Moisture Content (Humidity)

[0221] A 10 g powder sample has been heated in an oven at 150 C. until the mass is constant for at least 1 hour. The mass loss has been expressed as wt.-% loss based on the initial sample mass. This mass loss has been attributed to the sample humidity.

2. Examples

2.1 Materials Used

NO.SUB.x .Gas

[0222] Synthetic air containing nitrogen dioxide was provided by Messer Schweiz AG (Switzerland). The indicated analytical value is 0.4 vol % of NO.sub.2 (uncertainty +/3%).

[0223] Nitrogen containing nitrogen monoxide was provided by Messer Schweiz AG (Switzerland). The indicated analytical value is 10 vol % of NO (uncertainty +/2%).

Hydromagnesite (Inventive Material)

[0224] The hydromagnesite was a precipitated hydromagnesite produced by Omya International AG based on published protocols (see e.g. M. Pohl, C. Rainer, M. Esser; Omya Development AG, EP2322581 A1). The hydromagnesite had a d.sub.50 (vol)=3.2 m, d.sub.98 (vol)=12.4 m, d.sub.98 (vol)/d.sub.50 (vol)=3.88, and a BET SSA=92.2 m.sup.2/g.

Milled Natural Brucite (Inventive Material)

[0225] The milled natural brucite from Russia had a d.sub.50 (vol)=1.98 m, d.sub.98 (vol)=14.3 m, d.sub.98 (vol)/d.sub.50 (vol)=7.22, and a BET SSA=9.15 m.sup.2/g.

SYNTHETIC Magnesium Hydroxide (Inventive Material)

[0226] The synthetic magnesium hydroxide was synthesized from sea water by precipitation and had a d.sub.50 (vol)=4.86 m, d.sub.98 (vol)=15 m, d.sub.98 (vol)/d.sub.50 (vol)=3.09, and a BET SSA=4.55 m.sup.2/g.

Natural Ground Calcium Carbonate (Comparative Material)

[0227] The natural ground calcium carbonate was ground marble, which is commercially available from Omya International AG. The natural ground calcium carbonate had a d.sub.50 (vol)=1.7 m, d.sub.98 (vol)=8 m, d.sub.98 (vol)/d.sub.50 (vol)=4.71, and a BET SSA=3.75 m.sup.2/g.

2.2 NO.SUB.2 .Adsorption

[0228] The adsorption experiments have been conducted using a Hiden Isochema IGA-002 gravimetric analyzer. The instrument allows to monitor changes in the gravimetrically determined mass of a sample exposed to a gas at controlled temperature and pressure. For the shown experiments a tainless steel TGA crucible with a volume of 120 l (supplied by Mettler-Toledo (Schweiz) GmbH, Greifensee, Switzerland) was filled to the top with the respective sample powder of the materials described above. The crucible was mounted to the balance inside the instrument reaction chamber. The temperature in the sample chamber was controlled by a Thermostat at 20 C. during the whole experiment. The chamber was closed and pumped out to a vacuum of less than 5 mbar. After the vacuum was achieved the reaction chamber was filled with artificial air containing 0.4 vol % of NO.sub.2 (supplied by Messer Schweiz AG, Lenzburg, Switzerland) at 100 mbar/min. The gravimetrical weight was monitored and the change was attributed to the adsorption of NO.sub.2 and converted to adsorption rates based on time and sample weight for comparison purposes.

[0229] The results for the tested materials are shown in FIG. 1. It can be gathered from FIG. 1 that the particulate magnesium ion-comprising material according to the present invention shows a higher adsorption for NO.sub.2 than the comparative material based on calcium carbonate, i.e. a calcium ion-comprising material.

2.3 NO Adsorption

[0230] The adsorption experiments have been conducted using a Hiden Isochema IGA-002 gravimetric analyzer. The instrument allows to monitor changes in the gravimetrically determined mass of a sample exposed to a gas at controlled temperature and pressure. For the shown experiments a stainless steel TGA crucible with a volume of 120 l (supplied by Mettler-Toledo (Schweiz) GmbH, Greifensee, Switzerland) was filled to the top with the respective sample powder of the materials described above. The crucible was mounted to the balance inside the instrument reaction chamber. The temperature in the sample chamber was controlled by a Thermostat at 20 C. during the whole experiment. The chamber was closed and pumped out to a vacuum of less than 5 mbar. After the vacuum was achieved the reaction chamber was filled with artificial air containing 0.4 vol % of NO.sub.2 (supplied by Messer Schweiz AG, Lenzburg, Switzerland) or nitrogen containing 10 vol % of NO, respectively, at 100 mbar/min. The gravimetrical weight was monitored and the change was attributed to the adsorption of NO and converted to adsorption rates based on time and sample weight for comparison purposes.

[0231] The results for the tested materials are shown in FIG. 2. It can be gathered from FIG. 2 that the particulate magnesium ion-comprising material according to the present invention shows a higher adsorption for NO than the comparative material based on calcium carbonate, i.e. a calcium ion-comprising material.