Method for producing metal exchanged metallo-aluminophosphates by solid-state ion exchange at low temperatures

Abstract

Method for the preparation of a metal exchanged crystalline microporous metalloaluminophosphate or mixtures containing metal exchanged microporous metalloaluminophosphates materials comprising the steps of providing a dry mixture containing a) one or more metalloaluminophosphates starting materials that exhibit ion exchange capacity, and b) one or more metal compounds; heating the mixture in a gaseous atmosphere containing ammonia to a temperature (less than 300 C) and for a time sufficient to initiate and perform a solid state ion exchange of ions of the metal compound and ions of the crystalline microporous material; and obtaining the metal-exchanged microporous metalloaluminophosphate material or mixtures containing the metal-exchanged microporous metalloaluminophosphate material.

Claims

1. Method for the preparation of a metal exchanged crystalline microporous metalloaluminophosphate or mixtures containing metal exchanged microporous metalloaluminophosphates materials comprising the steps of providing a dry mixture containing a) one or more metalloaluminophosphates starting materials that exhibit ion exchange capacity and b) one or more metal compounds; heating the mixture in a gaseous atmosphere containing ammonia to a temperature between 100? C. and 250? C. and for a time sufficient to initiate and perform a solid state ion exchange of ions of the metal compound and ions of the crystalline microporous material; and obtaining the metal-exchanged microporous metalloaluminophosphate material or mixtures containing the metal-exchanged microporous metalloaluminophosphate material.

2. Method according to claim 1, wherein the one or more metalloaluminophosphate starting materials contain one or more metals chosen from the group silicon, titanium, tin, zinc, magnesium, manganese, cobalt or iron.

3. Method according to claim 1, where the one or more metalloaluminophosphate starting materials have the framework code of CHA, AEI, AFI, AEL, AST, AFR, AFO and FAU.

4. Method according to claim 1, wherein the one or more metalloaluminophosphate starting materials are selected from the group consisting of SAPO-34, SAPO-44, SAPO-18, or combinations thereof.

5. Method according to claim 1, wherein the one or more microporous metalloalumino-phosphate starting materials are in the H.sup.+ or NH.sub.4.sup.+ form.

6. Method according to claim 1, wherein the one or more microporous metalloalumino-phosphates starting materials contain an organic structure directing agent.

7. Method according to claim 1, wherein the one or more metal compounds in the dry mixture are selected from the group of metal oxides, metal nitrates, metal phosphates, metal sulfates, metal oxalates, metal acetates or combinations thereof.

8. Method according to claim 1, wherein the metals in the one or more metal compounds are selected from the group of Fe, Co, Cu.

9. Method according to claim 1, wherein the one or more metal compounds consist of oxides of Fe and/or Cu.

10. Method according to claim 1, wherein the one or metal compounds are Cu(I) oxide and/or Cu(II) oxide.

11. Method according to claim 1, wherein the content of ammonia in the atmosphere is between 1 and 5000 vol ppm.

12. Method according to claim 1, wherein oxygen is contained in the atmosphere in amount of 10 vol % or lower.

13. Method according to claim 1, wherein the gaseous atmosphere contains 5 vol % water or less.

14. A metal exchanged microporous metalloaluminophosphate material or mixtures of metal exchanged microporous metalloaluminophosphate materials obtained by a method according to claim 1.

15. A method for the removal of nitrogen oxides from exhaust gas by selective catalytic reduction with a reductant, comprising contacting the exhaust gas with a catalyst comprising a metal exchanged crystalline microporous metalloaluminophosphate material or mixtures of metal exchanged crystalline microporous metalloaluminophosphate materials obtained by a method according to claim 1.

16. A method according to claim 15, wherein the reductant is ammonia or a precursor thereof.

17. A method according to claim 15, wherein the reductant comprises hydrocarbons.

Description

EXAMPLE 1

(1) A catalyst was prepared by mixing CuO and H-SAPO-34 material to a content of 12.5 wt % CuO. A sample of the catalyst was placed in a quartz-U tube reactor, and heated to 250? C. for 10 h in an atmosphere containing 500 ppm NH.sub.3 in N.sub.2. After heating, the catalyst was cooled down to 160? C. and exposed to a gas mixture of 500 ppm NO, 533 ppm NH.sub.3, 5 vol % H.sub.2O, 10 vol % O.sub.2 in N.sub.2. The temperature was then stepwise increased to 180, 200, and 220? C. and the conversion of NO was measured at a space velocity of 2700 NL/g cat h, as a record for the material's SCR activity.

(2) The measured NO conversions at different temperatures are given in Table 1. It is noted that the SCR-active SAPO-34 material has not been heated further than 250? C. after addition of the Cu. This example illustrates that the method of the invention provides a way to produce an active catalyst based on SAPO-34 without the need of activation at elevated temperatures (>700? C.), which is the case for conventionally ion-exchanged SAPO-34 materials [P. N. R. Vennestr?m, A. Katerinopoulou, R. R. Tiruvalam, A. Kustov, P. G. Moses, P. Concepcion, A. Corma, ACS Catal. 2013, 3, 2158-2161.] after addition of Cu to the microporous material.

(3) TABLE-US-00001 TABLE 1 NOx conversion at different temperatures following 10 h heating of a mixture of CuO and H-SAPO-34 at 250? C. in 500 ppm NH.sub.3. Temperature (? C.) NOx conversion (%) 180 4.8 200 8.0 220 15.0

EXAMPLE 2

(4) For comparison, a catalyst similar to the one mentioned in Example 1 was prepared by mixing CuO and H-SAPO-34 material to a content of 12.5 wt % CuO. A sample of the catalyst was placed in a quartz-U tube reactor, and heated to 250? C. for 10 h in a pure N.sub.2 atmosphere. After heating, the catalyst was cooled down to 160? C. and exposed to a gas mixture of 500 ppm NO, 533 ppm NH.sub.3, 5 vol % H.sub.2O, 10 vol % O.sub.2 in N.sub.2. The temperature was then stepwise increased to 180, 200, and 220? C. and the conversion of NO was measured at a space velocity of 2700 NL/g cat h, as a record for the material's SCR activity.

(5) The measured NO conversions at different temperatures are given in Table 2. The NOx conversions obtained after treatment of the mixture of CuO and H-SAPO-34 in pure N.sub.2 are much lower than those obtained after a comparable treatment in the presence of 500 ppm NH.sub.3, given in Example 1. This shows that the presence of NH.sub.3 is essential to be able to produce Cu-SAPO-34 by solid state ion exchange at low temperatures. As the measurement of the SCR activity implies exposure of the system to a low concentration of ammonia, some formation of Cu-SAPO-34 occurs during the measurement, and a low conversion of NOx is measured, entirely in line with the present invention.

(6) TABLE-US-00002 TABLE 2 NOx conversion at different temperatures following 10 h heating of a mixture of CuO and H-SAPO-34 at 250? C. in nitrogen only. Temperature (? C.) NOx conversion (%) 180 1.8 200 1.7 220 3.5

EXAMPLE 3

(7) This example shows that an active metal exchanged metalloaluminophosphate catalyst for SCR can be prepared below 300? C. by the method of the invention using Cu.sub.2O. A dry mixture of 10 wt. % Cu.sub.2O and a H-SAPO-34 zeolite was prepared by grinding in a mortar. A sample of this mixture was placed in a quartz U-tube reactor, and heated to a predetermined temperature between 100 and 250? C. in nitrogen. After reaching the desired temperature, 500 ppm NH.sub.3 was added to the gas stream for 5 hours. After this treatment the catalytic activity of the resulting material was determined by cooling to 160? C. in nitrogen, and exposing the powder mixture to a gas atmosphere consisting of 500 ppm NO, 533 ppm NH.sub.3, 5 vol % H.sub.2O, 10 vol % O.sub.2 in N.sub.2, and the NOx conversion was measured at a space velocity of 2700 Nl/g cat h, as a record for the material's SCR activity. Then, the reaction temperature was increased to 180 and 200? C. and at each temperature the NOx conversion was determined under the same conditions.

(8) The NOx conversion in the SCR reaction over the metal exchanged zeolite prepared at 100, 150, 200 and 250? C. respectively in 500 ppm NH3 is given in Table 3.

(9) TABLE-US-00003 TABLE 3 NOx conversion over Cu.sub.2O + H-SAPO-34 mixtures after treatment in NH3 for 5 h at various temperatures Pretreatment NOx conv. @ NOx conv. @ NOx conv. @ temperature ? C. 160? C. (%) 180? C. (%) 200? C. (%) 100 0.9 1.0 2.2 150 0.9 1.1 2.9 200 2.3 3.8 7.9 250 7.4 14.2 26.0