Search

CA-3172357-C - COMPOSITIONS CONTAINING ZIRCONIUM AND CERIUM AND METHODS FOR PREPARING SAME USING OXALIC ACID AND AN ALCOHOL

CA3172357CCA 3172357 CCA3172357 CCA 3172357CCA-3172357-C

Abstract

Disclosed herein are mixed oxide compositions comprising zirconium and cerium having a surprisingly small particle sizes. The compositions disclosed herein contain zirconium, cerium, optionally yttrium, and optionally one or more other rare earths other than cerium and yttrium. The compositions exhibit a particle size characterized by a D90 value of about 5 um to about 25 µm and a D99 value of about 5 µm to about 50 µm. Further disclosed are processes of producing these compositions using oxalic acid and an alcohol and heating in the process. The compositions can be used as a catalyst and/or part of an automobile exhaust system.

Inventors

  • Barry Huang
  • Perlyn KOH
  • SZU, HWEE NG
  • Jesline TANG

Assignees

  • NEO PERFORMANCE MATERIALS (SINGAPORE) PTE. LTD.

Dates

Publication Date
20260505
Application Date
20210219
Priority Date
20200227

Claims (20)

  1. 16 What is claimed is: 1. A composition comprising zirconium, cerium, optionally yttrium, and optionally one or more rare earths other than cerium and yttrium, having a particle size characterized by a D90 value of about 5 μm to about 25 μm and a D99 value of about 5 μm to about 50 μm, wherein the composition exhibits a total mercury intrusion volume of from 0.5 to 4.0 cc/g after calcination at 1000 degree Celsius for 10 hours in an oxidizing environment, wherein the composition is produced by a process comprising the steps of mixing aqueous oxalic acid, zirconium solution, cerium solution, optionally yttrium solution, and optionally one or more rare earth solutions other than cerium and yttrium solution to provide a mixture, and dewatering with alcohol and dispersing and heating in alcohol, to form a precipitate from the mixture.
  2. 2. The composition of claim 1, having a particle size characterized by a D90 value of about 5 μm to about 18 μm and a D99 value of about 5 μm to about 40 μm.
  3. 3. The composition of claim 1 or 2, having a D50 value of from about 1 μm to about 10 μm.
  4. 4. The composition of claim 3, having a D50 value of from about 1 μm to about 5 μm.
  5. 5. The composition of any one of claims 1-4, having a D10 value of about 0.5 μm to about 3 μm.
  6. 6. The composition of any one of claims 1-5, wherein the composition comprises: (i) one or more other rare earths wherein the other rare earths are selected from the group consisting of lanthanum, praseodymium, neodymium, and mixtures thereof; and/or (ii) yttrium.
  7. 7. The composition of any one of claims 1-6, having a total mercury intrusion volume of from about 0.5 to about 3.0 cc/g after calcination at 1100 degrees Celsius for 10 hours in an oxidizing environment. 17
  8. 8. The composition of any one of claims 1-6, having a total mercury intrusion volume of from about 0.5 to about 3.5 cc/g after calcination at 1000 degrees Celsius for 10 hours in an oxidizing environment and a total mercury intrusion volume of from about 0.5 to about 2.0 cc/g after calcination at 1100 degrees Celsius for 10 hours in an oxidizing environment.
  9. 9. The composition of any one of claims 1-6, having a total mercury intrusion volume of from about 1.0 to about 1.8 cc/g after calcination at 1000 degrees Celsius for 10 hours and a total mercury intrusion volume of from about 0.7 to about 1.0 cc/g after calcination at 1100 degrees Celsius for 10 hours.
  10. 10. The composition of any one of claims 1-9, having a surface area of about 40 m2/g to about 100 m2/g after calcination at 1000 degrees Celsius for a period of 10 hours in an oxidizing environment and about 20 m2/g to about 85 m2/g after calcination at 1100 degrees Celsius for a period of 10 hours in an oxidizing environment.
  11. 11. The composition of any one of claims 1-9, having a surface area of about 40 m2/g to about 75 m2/g after calcination at 1000 degrees Celsius for a period of 10 hours in an oxidizing environment and about 20 m2/g to about 50 m2/g after calcination at 1100 degrees Celsius for a period of 10 hours in an oxidizing environment.
  12. 12. The composition of any one of claims 1-9, having a surface area of about 40 m2/g to about 50 m2/g after calcination at 1000 degrees Celsius for a period of 10 hours in an oxidizing environment and about 20 m2/g to about 30 m2/g after calcination at 1100 degrees Celsius for a period of 10 hours in an oxidizing environment.
  13. 13. The composition of any one of claims 1-12, comprising cerium and zirconium in a ratio of approximately 15-60 wt% / 40-75 wt% on an oxide equivalent weight basis.
  14. 14. A process of producing a composition of any one of claims 1 to 13, comprising the steps of: CA 3172357 18 (a) mixing aqueous oxalic acid, zirconium solution, cerium solution, optionally yttrium solution, and optionally one or more rare earth solutions other than cerium and yttrium solution to provide a mixture; (b) adding the mixture to a basic solution to form a precipitate; (c) dewatering with alcohol and dispersing and heating in alcohol; and (d) calcining the precipitate to provide a composition comprising zirconium, cerium, optionally yttrium, and optionally one or more rare earths other than cerium and yttrium.
  15. 15. The process of claim 14, wherein in step (a) aqueous oxalic acid, zirconium solution, cerium solution, and one or more rare earth solutions selected from the group consisting of lanthanum, praseodymium, neodymium, and mixtures thereof are mixed to provide the mixture.
  16. 16. The process of claim 14 or 15, wherein in step (a) a yttrium solution is mixed to provide the mixture.
  17. 17. The process of any one of claims 14-16 further comprising washing the precipitate with water after precipitation.
  18. 18. The process of any one of claims 14-17, wherein the oxalic acid is added in an amount of approximately 25% to approximately 100 % by weight with respect to equivalent oxide content.
  19. 19. The process of any one of claims 14-18, wherein the basic solution comprises an aqueous ammonia hydroxide solution and is approximately 4.5M.
  20. 20. The process of any one of claims 14-19, wherein the alcohol is isopropanol.

Description

Compositions Containing Zirconium and Cerium and Methods for Preparing Same Using Oxalic Acid and an Alcohol [0001] This application relates to compositions containing zirconium and cerium having small particle sizes and desirable mercury intrusion volumes and surface areas. These compositions also can have narrow particle size distributions. Also disclosed herein are processes for making these compositions. The compositions disclosed herein contain zirconium, cerium, optionally yttrium, and optionally one or morn rare tiarths other than cerium and yttrium. INTRODUCTION [0002) Cerium and zirconium oxide (Ce02- Zr02) based materials have been used in catalytic applications. Introduction of zirconium into the cerium (IV) oxide lattice or cerium into the zirconium oxide lattice greatly enhances and facilitates oxygen mobility. This fact has been readily adapted by the automotive pollution control catalyst industry where cerium and zirconium oxide (Ce02- Zr02) containing materials are ubiquitous in use as washcoat components. These materials catalyze oxidation of carbon monoxide and hydrocarbons and reduction of nitrogen oxides as shown in the below equations: 2CO + 02---+ 2C02 Cx.H2x+2 + [(3x+l)/2]02---+ xC02+ (x+l)H20 2NO + 2CO ---+ 2C02 + N2 [0003) Cerium and zirconium oxide (Ce02- Zr02) based materials also have been used in catalytic applications as supports to disperse active metal catalysts so as to enhance the activity of the catalyst resulting in high tum-over numbers. To this, the support plays a major role in maintaining the active metal catalyst's high dispersion state even at severe operating conditions such as high temperatures and hydrothermal environments. A support that fails to maintain its structural integrity under severe conditions may result in the occlusion or sintering of the active catalyst metal sites which results in diminished activity of the catalyst on a per molecule basis. Since many of these catalysts utilize expensive precious metals, such as platinum, palladium and/or rhodium, loss of catalyst metal activity directly impacts the cost of such catalysts requiring the use of increased precious metal loadings in order to maintain the desired catalyst activity. Parallel to this, the use of a structurally stable support allows for reduced precious metal use whilst maintaining or improving catalyst activity. I [0004] These cerium and zirconium catalysts are useful in contributing to the lowering of harmful vehicle exhaust gases. They provide high surface areas and oxygen buffering capacity, which are useful in these applications. The materials contribute to the enhancement of a catalytic system's ability to lower the emissions of gases such as hydrocarbons, carbon monoxide, and nitrogen oxides. [00051 In general, the catalytic material is required to have a sufficiently large specific surface area and a sufficiently high oxygen buffering capability, even at elevated temperatures. [0006] A variety of synthesis methods for the production of the cerium and zirconium oxide (Ce02- Zr02) based materials also have been reported. [0007] It is an object of the present application to provide cerium and zirconium based materials with excellent catalyst characteristics useful in catalysis and processes for synthesizing these materials. That is, as a catalyst/catalyst support having a high surface area, a stable surface under oxidizing, reducing and hydrothermal and redox conditions, with stable crystallographic characteristics under severe aging conditions, high and stable porosity with high mercury intrusion volume, with selective porosity/mercury intrusion volume, with high activity at lower temperatures and with low mass transfer resistance and high dynamic oxygen storage and release characteristics. A small particle size and a narrow particle size distribution are also desirable. SUMMARY [0008] As disclosed herein, the present compositions comprise zirconium, cerium, optionally yttrium, and optionally one or more rare earths other than cerium and yttrium These compositions have a small particle size characterized by a Dr;o value of from about 5 μm to about 25 μrn and a D99 value of about 5 ~rm to about 50 μm. These compositions having small particle sizes also have narrow particle size distributions and further have desirable mercury intrusion volumes and surface areas. [0009] In certain embodiments of the above-described compositions, the composition may also have a total mercury intrusion volume of from about 0.5 to about 4 cc/g after calcination at 1000 degrees Celsius for 10 hours in an oxidizing environment and a total mercury intrusion volume of from about 0.5 to about 3.0 cc/g after calcination at 1100 degrees Celsius for 10 hours in an oxidizing environment. [0010] In other embodiments of the above-described compositions, the composition further may have a surface area of about 40 m2/g to about 100 m2/g after calcination at l 000 degrees 2 3 Celsius for a period of 10 hours in an oxid