A PARTICULATE EARTH ALKALI CARBONATE-COMPRISING MATERIAL AND/OR PARTICULATE EARTH ALKALI PHOSPHATE-COMPRISING MATERIAL FOR NOx UPTAKE

Abstract

The present invention relates to a process for taking up one or more nitrogen oxide(s) from a gaseous and/or aerosol or liquid medium using at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material as well as an adsorbing material comprising said at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material.

Claims

1. A process for taking up one or more nitrogen oxide(s) from a gaseous or aerosol or liquid medium, the process comprising the following steps: a) providing a gaseous or aerosol or liquid medium comprising one or more nitrogen oxide(s), b) providing at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material having a BET specific surface area as measured by the BET nitrogen method in the range from 10 to 200 m.sup.2/g, and c) contacting the gaseous and/or aerosol or liquid medium of step a) with the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-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 or liquid medium onto the surface and/or into the pores of the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material, and d) optionally providing at least one particulate calcium carbonate-comprising material and contacting the at least one particulate calcium carbonate-comprising material with the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material of step b) before and/or during and/or after step c).

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

3. The process according to claim 1, wherein the gaseous and/or aerosol or liquid medium comprises one or more nitrogen oxide(s) selected from the group comprising NO, NO.sub.2, NO.sub.2.sup., NO.sub.3.sup., 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 or liquid medium comprises the one or more nitrogen oxide(s) in a total amount of up to 1 500 ppm, preferably of up to 700 ppm and more preferably in a total amount ranging from 1 to 600 ppm, based on the total volume of the gaseous and/or aerosol or liquid medium.

5. The process according to claim 1, wherein the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material of step b) and/or the at least one particulate calcium carbonate-comprising material of step d) is provided in form of a powder, granulated powder, suspension, such as aqueous suspension or suspension in organic solvents, column, cartridge, paint, coating, filter material, gabions, preferably gabions placed next to a motorway or a waste incineration plant, building material, in admixture with solid materials differing from the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material of step b) and/or the at least one particulate calcium carbonate material of step d), mica, clay, talc and the like.

6. The process according to claim 1, wherein the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material of step b) is surface-modified calcium carbonate, or surface-modified calcium carbonate in admixture with apatite, magnesium carbonate, hydromagnesite and/or dolomite.

7. The process according to claim 1, wherein the at least one particulate calcium carbonate-comprising material of step d) is at least one natural ground calcium carbonate (NGCC), and/or at least one precipitated calcium carbonate (PCC) having i) a volume median particle size d.sub.50 of <30 mm, more preferably from 40 nm to 2 000 m and most preferably from 60 nm to 400 m, determined by the light scattering method, and/or ii) a BET specific surface area as measured by the BET nitrogen method of from 0.5 to 200 m.sup.2/g, more preferably of from 15 to 175 m.sup.2/g and most preferably of from 25 to 100 m.sup.2/g, and/or iii) a particle size distribution d.sub.98/d.sub.50 of 2, more preferably 3, preferably in the range from 3.2 to 5.5, determined by the light scattering method.

8. The process according to claim 1, wherein the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material of step b) is at least one surface-modified calcium carbonate (MCC) having i) a volume median particle size d.sub.50 of 1 m, more preferably from 1 m to 100 m and most preferably from 1.5 m to 20 m, determined by the light scattering method, and/or ii) a BET specific surface area as measured by the BET nitrogen method of from 15 to 200 m.sup.2/g and most preferably from 30 to 160 m.sup.2/g, and/or iii) a particle size distribution d.sub.98/d.sub.50 of 1.1, more preferably 1.3, preferably in the range from 1.5 to 3, determined by the light scattering method, and/or iv) an intra-particle intruded specific pore volume from 0.150 to 1.300 cm.sup.3/g, and preferably from 0.178 to 1.244 cm.sup.3/g, calculated from a mercury intrusion porosimetry measurement.

9. The process according to claim 1, wherein the at least one particulate calcium carbonate-comprising material of step d) and/or the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material of step b) has/have a moisture content of at least 0.001 mg/m.sup.2.

10. The process according to claim 1, wherein the process comprises a further step e) of exposing the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material to UV and/or visible light during and/or after step c).

11. The process according to claim 1, wherein the process comprises a further step f) of washing the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material obtained in step c) or if present step e) 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 earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material.

12. The process according to claim 11, wherein the washing step f) is carried out by contacting the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material obtained in step c) or if present step e) with water, an organic solvent, an aqueous solution of at least one basic reacting salt, preferably Na.sub.2CO.sub.3 or Li.sub.2CO.sub.3, or at least one base, preferably lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, ammonia, ammonium hydroxide, organic amines or mixtures thereof.

13. The process according to claim 11, wherein the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material obtained in washing step f) is re-used in process step b) as the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material.

14. A particulate earth alkali carbonate-comprising material and/or particulate earth alkali phosphate-comprising material obtained by a process for taking up one or more nitrogen oxide(s) from a gaseous and/or aerosol or liquid medium according to claim 1.

15. An adsorbing material comprising at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material as defined in claim 1.

16. Use of at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material as defined in claim 1 for taking up one or more nitrogen oxide(s) from a gaseous and/or aerosol or liquid medium, preferably the gaseous and/or aerosol or liquid medium comprises one or more nitrogen oxides is selected from the group comprising NO, NO.sub.2, NO.sub.2.sup., NO.sub.3.sup., 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.

17. The use according to claim 16, wherein the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material is in form of a powder, granulated powder, suspension, such as aqueous suspension or suspension in organic solvents, column, cartridge, paint, coating, filter material, gabions, preferably gabions placed next to a motorway or a waste incineration plant, building material, in admixture with solid materials differing from the at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material and the like.

Description

EXAMPLES

[0307] 1. Measurement Methods

[0308] In the following the measurement methods implemented in the examples are described.

[0309] Particle Size Distribution of a Particulate Material:

[0310] Volume based median particle size d.sub.50(vol) and the volume based top cut particle size d.sub.98(vol) was evaluated using a Malvern Mastersizer 2000 Laser Diffraction System (Malvern Instruments Plc., Great Britain). The d.sub.50(vol) or d.sub.98(vol) value indicates a diameter value such that 50% or 98% 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.

[0311] 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.

[0312] Porosity/Pore Volume

[0313] The specific pore volume is measured using a mercury intrusion porosimetry measurement using a Micromeritics Autopore V 9620 mercury porosimeter having a maximum applied pressure of mercury 414 MPa (60 000 psi), equivalent to a Laplace throat diameter of 0.004 m (nm). The equilibration time used at each pressure step is 20 seconds. The sample material is sealed in a 5 cm.sup.3 chamber powder penetrometer for analysis. The data are corrected for mercury compression, penetrometer expansion and sample material compression using the software Pore-Comp (Gane, P. A. C., Kettle, J. P., Matthews, G. P. and Ridgway, C. J., Void Space Structure of Compressible Polymer Spheres and Consolidated Calcium Carbonate Paper-Coating Formulations, Industrial and Engineering Chemistry Research, 35(5), 1996, p 1753-1764.).

[0314] The total pore volume seen in the cumulative intrusion data can be separated into two regions with the intrusion data from 214 m down to about 1-4 m showing the coarse packing of the sample between any agglomerate structures contributing strongly. Below these diameters lies the fine interparticle packing of the particles themselves. If they also have intraparticle pores, then this region appears bi modal, and by taking the specific pore volume intruded by mercury into pores finer than the modal turning point, i.e. finer than the bi-modal point of inflection, define the specific intraparticle pore volume. The sum of these three regions gives the total overall pore volume of the powder, but depends strongly on the original sample compaction/settling of the powder at the coarse pore end of the distribution.

[0315] By taking the first derivative of the cumulative intrusion curve the pore size distributions based on equivalent Laplace diameter, inevitably including pore-shielding, are revealed. The differential curves clearly show the coarse agglomerate pore structure region, the interparticle pore region and the intraparticle pore region, if present. Knowing the intraparticle pore diameter range it is possible to subtract the remainder interparticle and interagglomerate pore volume from the total pore volume to deliver the desired pore volume of the internal pores alone in terms of the pore volume per unit mass (specific pore volume). The same principle of subtraction, of course, applies for isolating any of the other pore size regions of interest.

[0316] pH of an Aqueous Suspension or Solution

[0317] The pH of a suspension or solution is measured at 25 C. using a Mettler Toledo Seven Easy pH meter and a Mettler Toledo InLab Expert Pro pH electrode. It is appreciated that the temperature of 25 C. means 25 C.2 C. A three point calibration (according to the segment method) of the instrument is first made using commercially available buffer solutions having pH values of 4, 7 and 10 at 20 C. (from Aldrich). The reported pH values are the endpoint values detected by the instrument (the endpoint is when the measured signal differs by less than 0.1 mV from the average over the last 6 seconds).

[0318] BET Specific Surface Area of a Particulate Material

[0319] 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.

[0320] If the particulate material is a MCC, the specific surface area is measured via the BET method according to ISO 9277:2010 using nitrogen, following conditioning of the sample by heating at 250 C. for a period of 30 min. Prior to such measurements, the sample is filtered within a Buchner funnel, rinsed with deionised water and dried overnight at 90 to 100 C. in an oven. Subsequently the dry cake is ground thoroughly in a mortar and the resulting powder placed in a moisture balance at 130 C. until a constant weight is reached. The specific surface area is measured before any surface treatment. We assume that the surface treatment does not alter the BET surface area.

[0321] Solids Content

[0322] 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.

[0323] Moisture Content (Humidity)

[0324] 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.

[0325] Ion Chromatography

[0326] Cations and anions were measured by ionic chromatography (882 Compact IC plus, Metrohm). Anion mobile phase: 1.0 mmol/L NaHCO.sub.3 and 3.2 mmol/L Na.sub.2CO.sub.3. Flow of 0.7 mL/min.

[0327] Cation mobile phase: 1.7 mmol/L HNO.sub.3 and 0.7 mmol/L DPA. Flow 0.9 mL/min. The different ions are measured using a conductivity detector.

2. EXAMPLES

[0328] NO.sub.x Gas

[0329] Synthetic air containing nitrogen dioxide was provided by Pan Gas AG (Switzerland). The indicated analytical value is 10 ppm nitrogen dioxide (uncertainty +/10%).

[0330] Surface-Modified Calcium Carbonate: [0331] a) Surface-modified calcium carbonate 1 (MCC1):

[0332] MCC 1 had a d.sub.50(vol)=7.1 m, d.sub.98(vol)=13.65 m, d.sub.98(vol)/d.sub.50(vol)=1.9, SSA=66.0 m.sup.2/g with an intra-particle intruded specific pore volume of 1.018 cm.sup.3/g (for the pore diameter range of 0.004 to 0.51 m) and humidity=1.5%.

[0333] MCC 1 was obtained by preparing 8 litres of an aqueous suspension of ground calcium carbonate in a mixing vessel by adjusting the solids content of a ground limestone calcium carbonate from Orgon, France, having a weight based median particle size of 1.2 m, as determined by sedimentation, such that a solids content of 10 wt.-%, based on the total weight of the aqueous suspension, is obtained.

[0334] Whilst mixing the slurry, 0.3 kg phosphoric acid was added in form of an aqueous solution containing 30 wt.-% phosphoric acid to said suspension over a period of 10 minutes at a temperature of 70 C. Finally, after the addition of the phosphoric acid, the slurry was stirred for additional 5 minutes, before removing it from the vessel and drying.

[0335] pH (10 wt % suspension in deionised water)=7.9 [0336] b) Surface-modified calcium carbonate 2 (MCC 2):

[0337] MCC 2 had a d.sub.50(vol)=6.6 m, d.sub.98(vol)=15.1 m, d.sub.98(vol)/d.sub.50(vol)=2.29, SSA=144 m.sup.2/g with an intra-particle intruded specific pore volume of 0.811 cm.sup.3/g (for the pore diameter range of 0.004 to 0.23 m) and humidity=6.77 wt.-%.

[0338] MCC 2 was obtained by preparing 450 litres of an aqueous suspension of ground calcium carbonate in a mixing vessel by adjusting the solids content of a ground marble calcium carbonate from Hustadmarmor, Norway, having weight based median particle size distribution of 90% less than 2 m, as determined by sedimentation, such that a solids content of 16 wt.-%, based on the total weight of the aqueous suspension, is obtained.

[0339] Whilst mixing the slurry, 47.1 kg phosphoric acid was added in form of an aqueous solution containing 30 wt.-% phosphoric acid to said suspension over a period of 15 minutes at a temperature of 70 C. After the addition of the acid, the slurry was stirred for additional 5 minutes, before removing it from the vessel and drying.

[0340] pH (10 wt.-% suspension in deionised water)=7.5 [0341] c) Surface-modified calcium carbonate 3 (MCC 3):

[0342] MCC 3 has a d.sub.50(vol)=6.9 m, d.sub.98(vol)=24.4 m, d.sub.98(vol)/d.sub.50(vol)=3.5, SSA=26 m.sup.2/g with an intra-particle intruded specific pore volume of 0.449 cm.sup.3/g (for the pore diameter range of 0.004 to 0.32 m) and humidity=1 wt.-%. pH (10 wt % suspension in deionised water)=8.4.

[0343] MCC 3 was obtained by preparing 1 000 litres of an aqueous suspension of ground calcium carbonate in a mixing vessel by adjusting the solids content of a ground marble calcium carbonate from Hustadmarmor, Norway, having a d.sub.50(wt.) of 1.7 m and a d.sub.98(wt.) of 5 m, as determined by sedimentation, such that a solids content of 20 wt.-%, based on the total weight of the aqueous suspension, is obtained. Whilst mixing the slurry, 46 kg phosphoric acid was added in form of an aqueous solution containing 30 wt.-% phosphoric acid to said suspension over a period of 30 minutes at a temperature of 70 C. After the addition of the acid, the slurry was stirred for additional 5 minutes, before removing it from the vessel and drying.

Example 1

NO.SUB.x .Adsorption from Ambient Air

[0344] 100 g of modified calcium carbonate 1 was homogeneously distributed over the surface of an aluminium dish (2417 cm). The material was stored open inside the laboratory bench over several weeks. After the certain period 5 grams of the material were removed and mixed at room temperature with 30 g of deionized water (MiliQ water; resistivity 18 Mcm; TOC<3 ppb) and shaken for 10 minutes. The suspension was filtrated and analysed by ion chromatography as described hereafter,

[0345] The results are shown in the table 1 below:

TABLE-US-00001 TABLE 1 Modified calcium carbonate 1 Time [hours] NO.sub.2.sup. [mg/kg dry material] NO.sub.3.sup. [mg/kg dry material] 0 2.64 7.51 65 5.63 7.78 90 6.78 8.07 120 7.99 7.87 287 15.15 10.02 431 18.89 10.05 931 32.99 13.44 1 412 42.61 22.99 2 108 62.17 40.93 3 260 71.73 86.94

Example 2

[0346] Adsorption of concentrated artificial NO.sub.x gas:

[0347] 5 grams of modified calcium carbonate 1 were put in an Erlenmeyer. NO.sub.x gas of 10 ppm was flowed using a wash bottle system over the sample for 1 minute. 30 g of water were added and the solution was shaken. The solution was then filtrated and analysed by IC.

[0348] The results are outlined in table 2 below.

TABLE-US-00002 TABLE 2 NO.sub.2.sup. [mg/kg dry material] NO.sub.3.sup. [mg/kg dry material] Before contact After contact Before contact After contact with artificial with artificial with artificial with artificial air air air air 2.5 5.0 7.5 10.0

Example 3

[0349] Experimental Setup

[0350] The experimental set-up is outlined in FIG. 1 below.

[0351] A drying tube Scienceware (Sigma Aldrich, Ref. Z118559-12EA) was used as a gas column and filled at both ends with around 1 cm of glass wool (Supelco, Ref 2-0384). The column was closed at one end with the corresponding tip. The sample was added in the column. The other end of the column was closed with another identical tip, both having a gas inlet.

[0352] The column was then connected to a NO.sub.x gas bottle (10 ppm NO.sub.x gas in artificial air) and on the other side to a recipient containing a Drager NO.sub.x gas detector. Finally, this recipient was connected to a flowmeter in order to know the flow of gas going through the column.

[0353] The gas was flowed through the column over 26 hours at around 200 mL/min. The NO.sub.x amount was measured by the Drager instrument and manually recorded over time. Measurements were performed at room temperature (23+/2 C.).

[0354] Gas flowmeter: FlowMark, Perkin Elmer, Part N9307086, Serial N PE200904. Measuring range 0-600 mL/min.

[0355] Drager NO.sub.x gas detector: Drager PAC 7000 NO.sub.2 (ref 8318977, Serial N ARHA-2302). Measuring range 0-50 ppm.

[0356] Trial 3A Reference (Column with Glass Wool)

[0357] The filter column was filled with loosely packed glass wool NO.sub.x containing gas was passed through with a flow rate as indicated in table 3 below. After a few minutes the measured NO.sub.x concentration at the outlet of the filter column was 6.3 ppm which corresponds to the concentration in the original NO.sub.x containing gas. This shows that no NO.sub.x is adsorbed by the glass wool packed filter column.

[0358] Trial 3B (Column with 5 g of MCC1+NO.sub.x Gas)

[0359] The filter column was filled with MCC1. 5 g of loosely packed powder filled the whole column. Glass wool was put on the inlet and outlet of the column in order to avoid that the powder material was flowing out of the cartridge.

[0360] The NO.sub.x containing gas was passed through with a flow rate as indicated in table 3 below. The measured NO.sub.x values are reported below. This example illustrates the removal of NO.sub.x out of the gas stream.

[0361] Trial 3C (Column with 5 g of MCC2+NO.sub.x Gas

[0362] The filter column was filled with MCC2. 5 g of loosely packed powder filled the whole column. Glass wool was put on the inlet and outlet of the column in order to avoid that the powder material was flowing out of the cartridge.

[0363] The NO.sub.x containing gas was passed through with a flow rate as indicated in Table 3 below. The measured NO.sub.x values are reported below. This example illustrates the removal of NO.sub.x out of the gas stream.

TABLE-US-00003 TABLE 3 Trial 3A Trial 3B Trial 3C Air flow NO.sub.x NO.sub.x Air flow NO.sub.x Air flow Time [mL/min] [ppm] [ppm] [mL/min] [ppm] [mL/min] [hours] (1) (2) (1) (2) (1) (2) 0.00 200.0 0.0 0.0 200.0 0.0 198.0 0.02 1.2 0.0 199.0 0.0 226.0 0.03 198.0 2.3 0.0 194.0 0.0 211.0 0.05 3.3 0.0 200.0 0.0 200.0 0.07 4.2 0.0 200.0 0.0 212.0 0.08 201.0 4.7 0.2 196.0 0.3 208.0 0.17 5.9 0.4 206.0 0.4 207.0 0.25 6.2 0.4 199.0 0.4 205.0 0.5 202.0 6.3 0.5 192.0 0.4 208.0 1.0 6.3 0.5 192.0 0.4 197.0 2.0 200.0 6.3 0.4 179.0 0.4 200.0 3.0 0.4 203.0 3.6 0.5 255.0 4.0 0.5 194.0 0.4 200.0 5.0 0.4 194.0 0.4 220.0 6.0 0.3 185.0 7.0 0.4 214.0 20.0 21.0 0.4 225.0 22.0 0.5 240.0 23.0 0.4 206.0 0.3 199.0 24.0 0.4 210.0 0.3 206.0 25.0 0.4 221.0 0.3 218.0 26.0 0.4 215.0 0.4 225.0