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US-12617726-B2 - Zirconia-based composite oxide and method for manufacturing zirconia-based composite oxide

US12617726B2US 12617726 B2US12617726 B2US 12617726B2US-12617726-B2

Abstract

The purpose of the present invention is to provide a zirconia-based composite oxide for making it possible to form a catalyst layer which, despite having a reduced thickness, has a sufficient quantity of catalyst to function in exhaust gas treatment on a wall of a honeycomb structure. The purpose of the present invention is also to provide a method for manufacturing said zirconia-based composite oxide. The present invention relates to a zirconia-based composite oxide characterized in that the tap bulk density thereof is 0.75 g/mL or greater, and the specific surface area thereof after heat treatment for three hours at 1000° C. is 45 m 2 /g or greater.

Inventors

  • Kazuya Matsumoto
  • Hiroshi Kodama

Assignees

  • DAIICHI KIGENSO KAGAKU KOGYO CO., LTD.

Dates

Publication Date
20260505
Application Date
20200714
Priority Date
20190730

Claims (14)

  1. 1 . A zirconia-based composite oxide having a tap bulk density of 0.90 g/ml or more and a specific surface area of 45 m 2 /g or more after heat treatment at 1000° C. for 3 hours, wherein the zirconia-based composite oxide comprises from 4% to 70% of oxides of one or more selected from rare earth elements other than Pm.
  2. 2 . The zirconia-based composite oxide according to claim 1 , wherein the tap bulk density is 0.90 g/ml or more and 1.3 g/ml or less.
  3. 3 . The zirconia-based composite oxide according to claim 1 , wherein the tap bulk density is 0.90 g/ml or more and 1.27 g/ml or less.
  4. 4 . The zirconia-based composite oxide according to claim 1 , wherein the specific surface area after heat treatment at 1000° C. for 3 hours is 47 m 2 /g or more and 100 m 2 /g or less.
  5. 5 . The zirconia-based composite oxide according to claim 1 , wherein the zirconia-based composite oxide has a specific surface area of 15 m 2 /g or more and 70 m 2 /g or less after heat treatment at 1100° C. for 3 hours.
  6. 6 . The zirconia-based composite oxide according to claim 1 , wherein the zirconia-based composite oxide has a specific surface area of 45 m 2 /g or more and 150 m 2 /g or less.
  7. 7 . The zirconia-based composite oxide according to claim 1 , wherein a ratio of a pore volume of pores having a diameter of 100 nm or more and 1000 nm or less to a total pore volume in a pore distribution based on a mercury intrusion method is 17% or less of the total pore volume.
  8. 8 . The zirconia-based composite oxide according to claim 1 , wherein the zirconia-based composite oxide has a particle size D 50 of 5 μm or more and 25 μm or less.
  9. 9 . The zirconia-based composite oxide according to claim 1 , wherein a content of zirconia is 30 mass % or more and 95 mass % or less based on 100 mass % of the entire zirconia-based composite oxide.
  10. 10 . A method for manufacturing a zirconia-based composite oxide according to claim 1 , the method comprising: a first step including a step of adding a sulfating agent to a zirconium salt solution having a temperature of 100° C. or higher while stirring the zirconium salt solution at stirring Reynolds number of 400 or more and 2000 or less, and a step of cooling the zirconium salt solution to which the sulfating agent has been added to 60° C. or lower to obtain a cooled solution; and a second step including a step of heating the cooled solution obtained in the first step to a temperature of 100° C. or higher while stirring the cooled solution at stirring Reynolds number of 10 or more and 350 or less.
  11. 11 . The method for manufacturing a zirconia-based composite oxide according to claim 10 , wherein the stirring Reynolds number in the second step is 50 or more and 300 or less.
  12. 12 . The method for manufacturing a zirconia-based composite oxide according to claim 10 , wherein the stirring Reynolds number in the first step is 600 or more and 1800 or less.
  13. 13 . The method for manufacturing a zirconia-based composite oxide according to claim 10 , wherein the temperature during stirring in the first step is 105° C. or higher and 200° C. or lower.
  14. 14 . The method for manufacturing a zirconia-based composite oxide according to claim 10 , wherein the temperature during stirring in the second step is 105° C. or higher and 180° C. or lower.

Description

TECHNICAL FIELD The present invention relates to a zirconia-based composite oxide and a method for manufacturing a zirconia-based composite oxide. BACKGROUND ART Exhaust gas discharged from internal combustion engines of automobiles and the like, or combustion engines such as boilers contains hazardous substances such as carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) which cause air pollution and the like. Efficient purification of these hazardous substances is an important issue from the viewpoint of preventing environmental contamination and the like. Exhaust gas purification techniques which can purify the three hazardous substances at the same time have been actively studied. Recent tightening of exhaust gas regulations provides advanced development of a honeycomb structure. The honeycomb structure includes a filter collecting particulate matters (for example, gasoline particulate filter (GPF) and diesel particulate filter (DPF)) and having ternary catalytic performance for purifying carbon monoxide, hydrocarbon, and nitrogen oxide. A catalyst material is used in a state where the honeycomb structure is coated with the catalyst material in a slurry state. Patent Document 1 discloses a zirconia-based porous body having peaks in pore diameters of 8 to 20 nm and 30 to 100 nm in a pore distribution based on the BJH method and a total pore volume of 0.4 cc/g or more, and a zirconia-based porous body having a peak in a pore diameter of 20 to 110 nm in a pore distribution based on the BJH method and a total pore volume of 0.4 cc/g or more (particularly see claim 1). Patent Document 1 discloses that a specific surface area after firing at 1000° C. for 3 hours is at least 30 m2/g (particularly see claim 6). Patent Document 2 discloses a zirconia-based porous body which has a total pore volume of at least 0.75 ml/g after heat treatment at 1000° C. for 3 hours and in which the pore volume of pores having a diameter of 10 to 100 nm after heat treatment at 1000° C. for 3 hours is at least 30% of the total pore volume (particularly see claim 1). Patent Document 2 discloses that a specific surface area after heat treatment at 1000° C. for 3 hours is at least 35 m2/g (particularly see claim 2). Patent Document 3 discloses a zirconia-based porous body having (1) a peak in a pore diameter of 20 to 100 nm in a pore distribution based on the BJH method, a P/W ratio of 0.05 or more, wherein W represents a half width of a peak obtained in a measured pore distribution curve and P represents a height of the peak, and a total pore volume of 0.5 cm3/g or more; and (2) a peak in a pore diameter of 20 to 100 nm, the P/W ratio of 0.03 or more, a specific surface area of at least 40 m2/g, and a total pore volume of 0.3 cm3/g or more, after heat treatment at 1000° C. for 12 hours (particularly see claim 1). Patent Document 3 discloses that the zirconia-based porous body has a specific surface area of at least 20 m2/g after heat treatment at 1100° C. for 12 hours (particularly see claim 2). PRIOR ART DOCUMENTS Patent Documents Patent Document 1: JP-A-2006-036576Patent Document 2: JP-A-2008-081392Patent Document 3: JP-A-2015-189655 DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The zirconia-based porous bodies disclosed in Patent Document 1 to 3 have a high specific surface area even after heat treatment. Therefore, when these zirconia-based porous bodies are used as a catalyst carrier, the catalyst can be said to have high catalyst performance even after being exposed to a high temperature. In Patent Documents 1 to 3, in order to obtain a high specific surface area even after heat treatment, the pore volume of mesopores (diameter: 2 to 50 nm) to macropores (diameter: 50 nm or more) of the zirconia-based porous body is increased. When the zirconia-based porous bodies of Patent Document 1 to 3 are used, a catalyst layer needs to have a certain degree of thickness in order to form an amount of catalyst sufficiently functioning for exhaust gas treatment on a wall of a honeycomb structure while having high catalyst performance even after being exposed to a high temperature. However, when the thickness of the catalyst layer increases, a pressure loss of exhaust gas occurs, whereby the ventilation amount of the exhaust gas in the honeycomb structure decreases, which disadvantageously causes reduction in engine output and deterioration in exhaust gas purification performance. Conventionally, studies have been made to reduce the thickness of the catalyst layer, thereby reducing the pressure loss, but it is necessary to keep exhaust gas purifying ability at a certain level or more in order to reduce the pressure loss, which has a limit to reduce the thickness. Also in Patent Documents 1 to 3, there is room for improvement from the viewpoint of achieving both the exhaust gas purifying ability and the reduction in the pressure loss. The present invention has been made in view of the above-described problems,