BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a honeycomb shaped porous ceramic body in which generation of cracks is inhibited, a manufacturing method for the same, and a honeycomb shaped ceramic separation membrane structure including a separation layer.

2. Description of Related Art

In recent years, ceramic filters have been used to selectively collect only a specific component from a mixture (a mixed fluid) of multiple components. The ceramic filter is more excellent in mechanical strength, durability, corrosion resistance and the like as compared with an organic polymer filter, and hence the ceramic filter is preferably applied to removal of a suspended substance, bacteria, dust and the like from a liquid or a gas, in a wide range of fields of water treatment, exhaust gas treatment, pharmaceutical, food, or the like.

In such a ceramic filter, for the purpose of improving a permeation performance while maintaining a separation performance, it is necessary to enlarge a membrane area (the area of a separation membrane), and for that, the membrane preferably possesses a honeycomb shape. Furthermore, the filter of the honeycomb shape (a honeycomb shaped ceramic separation membrane structure) has advantages such as resistivity to breakage and achievement of cost reduction as compared with a tube type. In many cases, the honeycomb shaped ceramic separation membrane structure includes a porous substrate whose outer shape is columnar and which has therein a large number of parallel through channels (referred to as cells) formed in an axial direction thereof. Furthermore, the separation membrane (a separation layer) having smaller pore diameters than the porous substrate is formed on an inner wall surface provided with the cells.

In the honeycomb shaped ceramic separation membrane structure (a precision filtration membrane, an ultrafiltration membrane, a pervaporation membrane, a gas separation membrane, or a reverse osmosis membrane), a permeation flow rate is preferably increased by applying a high pressure during operation. Particularly, in the ultrafiltration membrane, the gas separation membrane and the reverse osmosis membrane, a permeation coefficient of the separation membrane is small, and hence it is necessary to perform separation and purification under a high operation pressure.

In Patent Document 1, a ceramic porous membrane having a bonding portion made of titania is disclosed. There is provided a porous body which can be prepared by performing firing at a low temperature and which has a practicable strength and a corrosion resistance.

In Patent Document 2, a porous ceramic body including frit (titania or the like) and fine particle aggregates is disclosed. A raw material including aggregates and frit is sintered, thereby providing a porous ceramic body having a higher strength than before.

In Patent Document 3, a porous alumina body which is excellent in acid resistance and alkali resistance is disclosed. The porous alumina body includes 5 to 30 mass % of titania and 1.5 mass % or less of an oxide of at least one element selected from the group consisting of copper, manganese, calcium and strontium. There is provided a porous alumina body which includes one of four elements including titania and copper, and hence has a high strength and is excellent in corrosion resistance against an alkali solution or an acid solution.

CITATION LIST

Patent Documents

[Patent Document 1] JP-A-H10-236887

[Patent Document 2] JP-A-2003-176185

[Patent Document 3] JP-A-2010-228948

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

In a honeycomb shaped ceramic separation membrane structure, a porous intermediate layer having a smaller average pore diameter as compared with the surface of a substrate is preferably disposed on a substrate, and a separation membrane is preferably disposed on the intermediate layer. Furthermore, when the honeycomb shaped ceramic separation membrane structure has slit cells which are not provided with the separation membrane in addition to separation cells provided with the separation membrane (a separation layer), a fluid allowed to permeate the separation membrane passes through the slit cells and is discharged to the outside, and hence a pressure loss can be decreased, which is advantageous for membrane separation.

However, when the honeycomb shaped ceramic separation membrane structure has two types of cells, i.e., the separation cells and the slit cells, there has been a problem that a crack (a slit crack) is easily generated in a portion adjacent to each of the slit cells. When the slit cracks are generated, deterioration of strength easily occurs. In particular, there is a possibility that the cracks extend due to long-term use, thereby deteriorating the strength. Furthermore, when the slit crack is generated between the slit cell and the separation cell, a defect is generated in the separation layer due to the cracks, which causes a problem that a separation performance cannot sufficiently be exerted.

In Patent Documents 1 and 2, there is not any description concerning the slit cells, and when the porous body has the slit cells, it is not clear in which range any slit cracks are not generated and a porous body having a high internal pressure breaking strength can be prepared. Also in Patent Document 3, there is not any description concerning the slit cells, and it is necessary to surely include one of four elements including copper.

An object of the present invention is to provide a honeycomb shaped porous ceramic body in which slit cracks are not easily generated, when the porous ceramic body has separation cells which have a separation layer above a disposed intermediate layer and slit cells in which the intermediate layer is not disposed, a manufacturing method for the porous ceramic body, and a honeycomb shaped ceramic separation membrane structure.

Means for Solving the Problem

The present inventors have found that slit cracks are easily generated when a thermal expansion coefficient of a bonding material of fine particles included in an intermediate layer is smaller than that of aggregates of the intermediate layer. When the thermal expansion coefficient of the bonding material is small a portion around each separation cell having the intermediate layer does not easily shrink though sintered at a high temperature and cooled. On the other hand, the aggregates noticeably shrink in the vicinity of each slit cell that does not have the intermediate layer. Therefore, tensile stress acts between a portion including more separation cells and a portion including more slit cells, and hence the slit cracks are generated. To solve the problem, according to the present invention, there are provided a honeycomb shaped porous ceramic body, a manufacturing method for the same, and a honeycomb shaped ceramic separation membrane structure in the following.

According to a first aspect of the present invention, a honeycomb shaped porous ceramic body is provided including a honeycomb shaped substrate which has partition walls made of a porous ceramic material provided with a large number of pores and in which there are formed a plurality of cells to become through channels of a fluid passing through the porous ceramic body by the partition walls; separation cells wherein an intermediate layer made of a porous ceramic material provided with a large number of pores and having a smaller average pore diameter as compared with the surface of the substrate, and disposed at the surface of the substrate is disposed; and slit cells in which the intermediate layer is not disposed, wherein the intermediate layer has a structure where aggregate particles are bonded to one another by an inorganic bonding material having a thermal expansion coefficient equal to or higher than that of the aggregate particles.

According to a second aspect of the present invention, the honeycomb shaped porous ceramic body according to the above first aspect is provided, wherein aggregates constituting the substrate and the intermediate layer are alumina, and the inorganic bonding material which bonds the aggregates of the intermediate layer is titania.

According to a third aspect of the present invention, the honeycomb shaped porous ceramic body according to the above first or second aspects is provided, which has an internal pressure breaking strength of 8 MPa or more.

According to a fourth aspect of the present invention, the honeycomb shaped porous ceramic body according to any one of the above first to third aspects is provided, wherein a content ratio of a component of the inorganic bonding material in an inorganic solid content of the intermediate layer is from 5 to 15 mass %.

According to a fifth aspect of the present invention, the honeycomb shaped porous ceramic body according to any one of the above first to fourth aspects is provided, wherein on the intermediate layer, a top layer made of a porous ceramic material having finer particles than the intermediate layer is disposed.

According to a sixth aspect of the present invention, the honeycomb shaped porous ceramic body according to the above fifth aspect is provided, wherein the top layer includes alumina as a main component.

According to a seventh aspect of the present invention, a honeycomb shaped ceramic separation membrane structure in which a separation layer is further disposed in the separation cells of the honeycomb shaped porous ceramic body according to any one of the above first to sixth aspects is provided.

According to an eighth aspect of the present invention, a manufacturing method for the honeycomb shaped porous ceramic body according to any one of the above first to sixth aspects is provided, in which a slurry for the intermediate layer including the aggregates and the inorganic bonding material to become the intermediate layer is adhered to the substrate, and fired at 1150 to 1300° C., to form the intermediate layer.

Effect of the Invention

In a honeycomb shaped porous ceramic body of the present invention, cracks are hardly generated in portions adjacent to the slit cells (portions between the slit cells or portions between the slit cells and the separation cells), and the porous ceramic body has a high strength. Therefore, the separation layer (separation membrane) having a high separation performance can be prepared.

