Mixtures for the adsorption of acidic gases

Abstract

The invention relates to mixtures containing basic anion exchangers and flow regulators, the use thereof for the adsorption of acidic gases and of carbon dioxide in particular, a process for continuous gas adsorption, and heat exchangers that contain the mixtures containing basic anion exchangers and flow regulators.

Claims

1. A mixture comprising: at least one basic anion exchanger having a water content of 0% by weight to 60% by weight based on the total mass of the ion exchanger and having a mean particle diameter of 100 to 1000 μm and at least one flow regulator that is different than the basic anion exchangers wherein said flow regulator has a mean particle diameter of 1 nm to 1000 μm.

2. The mixture as claimed in claim 1, wherein the anion exchanger is macroporous.

3. The mixture as claimed in claim 1, wherein the anion exchanger comprises primary amino groups.

4. The mixture as claimed in claim 1, wherein the anion exchanger has a water content of 01% to 40% based on the total mass of the basic anion exchanger.

5. The mixture as claimed in claim 1, wherein the basic anion exchanger comprises a macroporous crosslinked styrene/divinylbenzene polymer functionalized with primary amino groups.

6. The mixture as claimed in claim 1, wherein the flow regulators has a mean particle diameter of 1 nm to 500 μm.

7. The mixture as claimed in claim 1, wherein the flow regulators is selected from the group of silicon dioxides, colloidal silicon dioxide, silicas, fumed silicas, magnesium and aluminum silicates, talc or sodium aluminosilicate, calcium silicate, cellulose, powdered and microcrystalline cellulose, starch, sodium benzoate, calcium carbonate, magnesium carbonate, metal stearate, calcium stearate, magnesium stearate, zinc stearate, magnesium lauryl sulfate and magnesium oxide, and carbon black, gas black, lamp black, thermal black, acetylene black, and furnace black, graphite, and mixtures of said compounds.

8. The mixture as claimed in claim 1, wherein the flow regulators is graphite, silica or mixtures of said compounds.

9. The mixture as claimed in claim 8, wherein the mean particle diameter is 30 μm to 100 μm and 5 nm to 50 nm for graphite and silica, respectively.

10. The mixture as claimed in claim 1, wherein the mixture contains 0.01% to 10% by weight of the flow regulator and 90% by weight to 99.99% of the basic anion exchanger, based on the total mass of the mixture, wherein the basic anion exchanger is either dry or wet.

11. A continuous process for the adsorption of acidic gases, comprising: providing a heat exchanger containing the mixtures as claimed in claim 1, flowing of a gas stream containing acidic gases through the heat exchanger, and subsequently regenerating the basic anion exchanger into the mixtures as claimed in claim 1.

12. The process according to claim 11, wherein the acidic gases comprise carbon dioxide.

13. A heat exchanger containing the mixture as claimed in claim 1.

Description

EXAMPLES

Example 1

(1) Improvement in Flow Properties

(2) The improvement in the experimentally observed flowability is expressed by the Hausner ratio. The Hausner ratio describes the flowability of a bulk material and is used primarily in pharmacy. It is defined as:

(3) $A=\frac{{\rho }_{\mathrm{Tapped}}}{{\rho }_{Bulk}}=\frac{V_{Bulk}}{V_{\mathrm{Tapped}}}$

(4) where ρ.sub.Tapped is the tapped density and ρ.sub.Bulk the bulk density, V.sub.Bulk the bulk volume, and V.sub.Tapped the tapped volume. The closer the Hausner ratio is to 1, the better the flowability of the corresponding bulk material.

(5) In an experiment to measure the improvement in the flowability of the bulk material, 400 ml (212 g) of dried macroporous basic anion exchanger composed of a styrene/divinylbenzene copolymer with primary amino groups and having a residual water content of <10% was mixed with graphite and respectively with Aerosil® 200. The mean particle diameter of the anion exchangers used is 470 μm to 570 μm. The mean particle diameter of the flow regulator was 12 nm when fumed silica (Aerosil®) was used. The particle size of 85% of the graphite used was <75 μm. The amount of flow regulator that was added was between 0.01% by weight-10% by weight. The mixture of ion exchanger and flow regulator was then mixed for 2 h at a low rotation speed in a laboratory drum mixer, for example a Lödige L 5 laboratory mixer.

(6) After this, 100 ml of the macroporous basic anion exchanger mixed with flow regulator was transferred to a 100 ml measuring cylinder and the bulk density determined by weighing. The tapped density of the mixture was then measured using a JEL STAV 2003 jolting volumeter. This was done by applying 1250 taps with the jolting volumeter and then determining the volume of the mixture. The tapped volume and tapped density were determined in accordance with the pharmacopeial method “2.9.15 Bulk Volume/Tapped Volume” (Ph. Eur. 6th Edition). The ratio between the bulk density and tapped density was used to calculate the Hausner ratio and the optimized range for the amount of graphite or Aerosil® flow regulator to be added was determined as 0.01% by weight to 10% by weight.

(7) In addition to determining the flow-improving properties of graphite and Aerosil® on the improvement in flow properties, the effects on the adsorption capacity of the employed macroporous basic anion exchanger composed of a styrene/divinylbenzene copolymer bearing primary amino groups were also investigated. For the two flow regulators, addition of 0.01% by weight-10% by weight was found to have no adverse effect on the adsorption properties of the anion exchanger.

(8) The improvement in the adsorption capacity was confirmed by an adsorption isotherm measurement.

BRIEF DESCRIPTION OF THE DRAWINGS

(9) FIG. 1 shows the adsorption isotherms of the inventive mixture of a macroporous basic anion exchanger comprising a styrene/divinylbenzene copolymer having primary amino groups and 0.4% by weight of graphite.

Example 2

(10) Improvement in Adsorption Properties

(11) The dependence of the adsorption capacity on the temperature of the material used was determined by measurement of a number of adsorption isotherms at different temperatures. In the measurement described below, the macroporous crosslinked basic anion exchanger composed of a styrene/divinylbenzene copolymer bearing primary amino groups from example 1 was used as a mixture with graphite.

(12) The adsorption isotherms were determined by measurement of the adsorption capacity of the acidic gas CO.sub.2 at different temperatures and CO.sub.2 concentrations (see FIG. 1 and Table 1). For this, 15 ml (8 g) of dried macroporous basic anion exchanger composed of a styrene/divinylbenzene copolymer bearing primary amino groups and containing 0.32 g of graphite (mean particle diameter<75 μm) in a temperature-controlled column was subjected to a gas flow of 5% by volume to 50% by volume of CO.sub.2 and a number of breakthrough curves were measured for CO.sub.2 at 10° C. to 90° C. (see FIG. 1). The mean particle diameter of the anion exchangers used is 470 μm to 570 μm. Integration of the recorded breakthrough curves allowed the amount of CO.sub.2 adsorbed to be calculated. FIG. 1 and Table 1 show a number of adsorption isotherms for the mixture according to the invention at different temperatures. These show clearly that with increasing adsorption temperature there is an associated marked decrease in CO.sub.2 adsorption capacity. The use of the mixture according to the invention in a heat exchanger allows acidic gases, in particular CO.sub.2, to be adsorbed even at low temperatures, which means that higher adsorption capacities may be used. In the absence of a flow regulator, the adsorption needs to be carried out at considerably higher temperatures at which the adsorption capacity of the ion exchanger is considerably lower, since otherwise it is no longer possible to adequately dissipate the heat in the heat exchanger and the ion exchanger will become damaged with more protracted use.

(13) TABLE-US-00001 TABLE 1 Results of the experiments: Adsorption capacities at different temperatures and CO.sub.2 concentrations according to the isotherms in FIG. 1 CO.sub.2 Temperature concentration 10° C. 20° C. 40° C. 60° C. 80° C. 90° C. [% by volume] Capacity [mol/kg] 5 2.90 2.00 1.50 1.10 0.90 10 3.10 2.55 2.20 1.75 1.40 1.10 20 3.25 2.75 2.40 2.00 1.80 1.25 30 3.25 2.80 2.55 2.25 1.55 1.35 40 3.35 2.70 2.50 2.20 1.60 1.40 50 3.50 3.10 2.60 2.25 1.75 1.35