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EP-3995449-B1 - METHOD OF PREPARING SCR CATALYST

EP3995449B1EP 3995449 B1EP3995449 B1EP 3995449B1EP-3995449-B1

Inventors

  • YOON, DALYOUNG
  • CHO, SUNG JUNE
  • PARK, SOON HEE

Dates

Publication Date
20260506
Application Date
20210503

Claims (11)

  1. A method of preparing a SCR (Selective Catalytic Reduction) catalyst, comprising: preparing a synthetic mother liquid that includes a source of silica and alumina including zeolite A and silica, a structure-inducing material, a complexing material, and a solvent; reacting the synthetic mother liquid to prepare CHA zeolite; and ion-exchanging the prepared CHA zeolite with a transition metal, wherein the zeolite A is NH 4 -exchanged zeolite A, and wherein the structure-inducing material comprises trimethyladamantyl ammonium hydroxide (AdaOH).
  2. The method of claim 1, wherein the silica is fumed silica or colloidal silica.
  3. The method of claim 1, wherein the complexing material is an alkali hydroxide solution including sodium hydroxide.
  4. The method of claim 1, wherein the synthetic mother liquid comprises about 5 mol% to about 30 mol% of the zeolite A and about 70 mol% to about 95 mol% of the silica based on a total amount of the source of silica and alumina.
  5. The method of claim 1, wherein the synthetic mother liquid comprises: about 0.1 parts by mole to about 0.4 parts by mole of the structure-inducing material; and about 0.1 parts by mole to about 0.4 parts by mole of the complexing material based on 1 part by mole of the source of silica and alumina.
  6. The method of claim 1, wherein in the second process, the reaction is performed under conditions of about 120 °C to about 140 °C, about 2 days to about 6 days, and about 0 rpm to about 60 rpm.
  7. The method of claim 1, wherein in the second process, after the reaction, the method further comprises firing at about 500 °C to about 600 °C for 4 to 12 hours.
  8. The method of claim 1, wherein the CHA zeolite prepared in the second process has a Si/Al mole ratio of about 15 to about 30.
  9. The method of claim 1, wherein the transition metal comprises Cu, Fe, Co, Ti, Zn, Ag, Mn, or a combination thereof.
  10. The method of claim 1, wherein the SCR catalyst comprises about 1 wt% to about 5 wt% of the transition metal based on the total catalyst.
  11. The method of claim 1, wherein in the third process, the ion-exchanging is performed at about 25 °C to about 80 °C for about hour to about 24 hours.

Description

CROSS-REFERENCE TO RELATED APPLICATION BACKGROUND (a) Field The present disclosure relates to a method of preparing an SCR catalyst, and more particularly, to a method of preparing an SCR catalyst having improved thermal durability and NOx purification performance. (b) Description of the Related Art Zeolite is a porous material that fine pores with unique and regular shapes and sizes are well developed. Acidity of the zeolite may be controlled within a wide range by varying an amount of aluminum present in the skeleton and zeolite has a large specific surface area and may exchange cations, and therefore the zeolite is widely used as a catalyst or an adsorbent in the field of fine chemistry. Recently, a selective catalytic reduction (SCR) reaction has been commercialized in a post-treatment device for removing nitrogen oxides from automobile exhaust gas according to environmental regulations. As a catalyst for the reaction, copper ion-exchanged Cu/CHA exhibits high activity over a wide temperature range and excellent hydrothermal stability, compared with other zeolites, and thus draws a great interest. In addition, recently, a technology of coating the SCR catalyst on a diesel particulate filter (DPF) to increase NOx purification performance has been developed, but in order to apply the SCR catalyst to DPF, a catalyst having higher thermal durability and excellent NOx purification performance is required. However, when the aluminum present in the zeolite skeleton is exposed to hot water vapor, the aluminum may be eluted out of the skeleton and thus the structure of the zeolite may collapse, resulting in deteriorating catalytic activity. In addition, since various types of cations present in the zeolite also affect hydrothermal stability, the contents of these components should be controlled in order to increase the hydrothermal stability of the zeolite. US2019/300375 Al discloses a method of preparing an SCR catalyst comprising preparing a synthetic mother liquid that includes a source of silica and alumina including zeolite Y and silica, a structure-inducing material, a complexing material and a solvent; reacting the synthetic mother liquid to prepare CHA zeolite; and ion-exchanging the prepared CHA zeolite with a transition metal. SUMMARY An object of the present disclosure is to provide a method of preparing an SCR catalyst having a Si/Al mole ratio of greater than or equal to about 15, maintaining a zeolite structure even after degradation, and having excellent thermal durability and NOx purification performance. According to an embodiment of the present disclosure, a method of preparing a SCR (Selective Catalytic Reduction) catalyst includes preparing a synthetic mother liquid that includes a source of silica and alumina including zeolite A and silica, a structure-inducing material, a complexing material, and a solvent, reacting the synthetic mother liquid to prepare CHA zeolite, and ion-exchanging the prepared CHA zeolite with a transition metal. The zeolite A is an NH4-exchanged zeolite A. The silica may be fumed silica or colloidal silica. The structure-inducing material is trimethyladamantyl ammonium hydroxide (AdaOH). The complexing material may be an alkali hydroxide solution including sodium hydroxide. The synthetic mother liquid may include about 5 mol% to about 30 mol% of the zeolite A and about 70 mol% to about 95 mol% of the silica based on a total amount of the source of silica and alumina. The synthetic mother liquid may include about 0.1 parts by mole to about 0.4 parts by mole of the structure-inducing material and about 0.1 parts by mole to about 0.4 parts by mole of the complexing material based on 1 part by mole of the source of silica and alumina. In the second process, the reaction may be performed under conditions of about 120 °C to about 140 °C, about 2 days to about 6 days, and about 0 rpm to about 60 rpm. In the second process, after the reaction, the method may further include firing at about 500 °C to about 600 °C for 4 to 12 hours. The CHA zeolite prepared in the second process may have a Si/Al mole ratio of about 15 to about 30. The transition metal may include Cu, Fe, Co, Ti, Zn, Ag, Mn, or a combination thereof. The SCR catalyst may include about 1 wt% to about 5 wt% of the transition metal based on the total catalyst. In the third process, the ion-exchanging may be performed at about 25 °C to about 80 °C for about 1 hour to about 24 hours. The preparation method of the SCR catalyst according to the present disclosure may provide an SCR catalyst having a Si/Al mole ratio of greater than or equal to about 15 and maintaining the zeolite structure after the degradation and thus having high thermal durability and excellent NOx purification performance. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow chart showing a method of preparing an SCR catalyst according to an embodiment of the present disclosure.FIGS. 2, 3, and 4 are electron microscope photographs showing CHA