Honeycomb carrier for improving DOC catalyst coating firmness

Abstract

The invention provides a honeycomb carrier for improving DOC catalyst coating firmness, the honeycomb carrier comprises a honeycomb carrier with straight-flow honeycomb holes, the wall of each honeycomb hole of the honeycomb carrier is provided with an aluminum oxide coating, the thickness of the aluminum oxide coating is 10-30 g / L, the aluminum oxide coating is coated with aluminum oxide sol with the average particle size of 1-30 nm and sintered at the temperature of 400-450 DEG C, the thickness of the aluminum oxide coating is 10-30 g / L, the thickness of the aluminum oxide coating is 10-30 g / L, and the average particle size of the aluminum oxide sol is 1-30 nm. When the non-noble metal catalyst is coated, the firmness degree of the non-noble metal catalyst can be obviously improved, in the coating process of the non-noble metal catalyst, it can still be guaranteed that the catalyst is firmly attached to the honeycomb hole walls of the honeycomb-shaped carrier through a small amount of aluminum oxide sol, and the falling-off rate is reduced to 1% or below.

Description

TECHNICAL FIELD

[0001] The present application relates to a honeycomb carrier with straight flow honeycomb holes for use in exhaust gas aftertreatment systems of diesel internal combustion engines, in particular for coating a non-noble metal catalyst into an oxidation catalyst (DOC). BACKGROUND

[0002] The carriers used in the existing oxidation catalysts DOC are basically of cordierite material, and the catalysts coated on the carriers are roughly of two types, a noble metal catalyst with platinum, palladium and rhodium as active components, and a non-noble metal catalyst with a composite oxide of rare earth and manganese, iron, nickel and copper as active components. The noble metal catalyst generally loads the noble metal on alumina solid powder, mixes with water and alumina sol to form a coating liquid, and coats the inner hole surface of the honeycomb carrier. Since the alumina has good surface compatibility with the cordierite, the combination on the cordierite surface is relatively firm after sintering. For the non-noble metal catalyst, since the catalyst composition is generally a composite oxide of rare earth and manganese, iron, nickel and copper, although alumina sol is also added to the coating liquid, the amount of alumina sol added should not be too much. The weight ratio of alumina after sintering to the catalyst should not exceed 20%. Too much alumina will embed the catalyst, causing the catalytic performance to decrease, and too little alumina sol will cause the catalyst to not firmly combine with the surface of the cordierite, and the catalyst is prone to falling off. SUMMARY

[0003] The present application aims to provide a honeycomb carrier for improving the coating firmness of a DOC catalyst, to solve the problem of easy falling off of the non-noble metal catalyst after coating the honeycomb carrier.

[0004] To achieve the above-mentioned purpose, the honeycomb carrier for improving the coating firmness of a DOC catalyst of the present application comprises a honeycomb carrier with straight flow honeycomb holes, and the honeycomb hole walls of the honeycomb carrier have an alumina coating layer with a thickness of (10-30) g / L, which is coated with alumina sol with an average particle size of (1-30) nm and sintered at (400-450) °C.

[0005] Preferably, the thickness of the alumina coating layer is (16-24) g / L.

[0006] Preferably, the average particle size of the alumina sol is (2-5) nm.

[0007] The honeycomb carrier coated with the alumina coating layer of the present application can significantly improve the firmness of the non-noble metal catalyst when coating the non-noble metal catalyst. During the coating process of the non-noble metal catalyst, the catalyst can still be firmly loaded on the honeycomb hole walls of the honeycomb carrier with a small amount of alumina sol, and the falling off rate is reduced to below 1%. DETAILED DESCRIPTION

[0008] Example 1: Alumina sol with solid content 20%, average particle size 3nm, add 3 times weight of water to dilute, make coating solution with solid content 5wt%. Coating the coating solution on straight flow honeycomb carrier with diameter 118mm, length 76.2mm, hole density 400mesh / square inch, dry at 110°C, then heat up to 420°C at the rate of 100°C / hour, keep temperature for 1 hour, cool down, then repeat coating for the second time, dry at 110°C, then heat up to 420°C at the rate of 100°C / hour, keep temperature for 2 hours, cool down to form honeycomb carrier with alumina coating layer about 16g / L.

[0009] The carrier is tested for non-noble metal catalyst coating comparison with honeycomb carrier without alumina coating. Catalyst ingredient is LaMnOx composite oxide, make coating solution by mixing catalyst with water and alumina sol according to the weight ratio in the table below, coat on multiple honeycomb carriers of Example 1 and multiple honeycomb carriers without alumina coating, sinter at 600°C, repeat coating and sintering until the carrier coating amount reaches 140-150g / L.

[0010] After coating and sintering are completed, weigh the carrier while it is hot at 120°C, record the weight data, use air pressure 0.6MPa air gun to blow each honeycomb hole of the carrier at a distance of 1cm from the end face of the carrier until all the holes have been blown. After blowing is completed, the carrier is sent to the oven for drying at 120°C for 4 hours, then weighed while hot, and the data obtained by the algorithm of (weight before blowing - weight after blowing) / weight before blowing * 100% is taken as the catalyst shedding rate in the carrier.

[0011]

[0012] As can be seen from the data in the table, the honeycomb carrier of Example 1 can reduce catalyst shedding and improve the firmness of catalyst and carrier combination.

[0013] Example 2: Alumina sol with solid content 20%, average particle size 4nm, add 2 times weight of water to dilute, make coating solution with solid content 6.7wt%. Coating the coating solution on straight flow honeycomb carrier with diameter 118mm, length 76.2mm, hole density 400mesh / square inch, dry at 110°C, then heat up to 420°C at the rate of 100°C / hour, keep temperature for 1 hour, cool down, then repeat coating for the second time, dry at 110°C, then heat up to 420°C at the rate of 100°C / hour, keep temperature for 2 hours, cool down to form honeycomb carrier with alumina coating layer about 24g / L. The carrier is tested for non-noble metal catalyst coating comparison with honeycomb carrier without alumina coating. Catalyst ingredient is LaMn 0.95 K 0.05Ox composite oxide, the catalyst and water, alumina sol were mixed to form a coating solution according to the weight ratio in the table below, and were coated on multiple honeycomb carriers of Example 1 and multiple honeycomb carriers without alumina coating. After sintering at 600℃, the coating and sintering were repeated until the carrier coating amount reached 140-150g / L.

[0014] After the coating and sintering were completed, the carrier was weighed while hot at 120℃, and the honeycomb channels of the carrier were blown one by one using a pneumatic gun at a gas pressure of 0.6MPa at a distance of 1cm from the end face of the carrier until all the channels had been blown. After the blowing was completed, the carrier was sent to an oven for drying at 120℃ for 4 hours, and then was weighed while hot. The data obtained using the algorithm (weight before blowing - weight after blowing) / weight before blowing * 100% were used as the catalyst shedding rate in the carrier.

[0015]

[0016] As can be seen from the data in the table, the honeycomb carrier of Example 1 can reduce the shedding of the catalyst and improve the firmness of the catalyst and the carrier.

Claims

1. A honeycomb support for improving the coating adhesion of DOC catalysts, comprising a honeycomb support having direct-flow honeycomb pores, characterized in that, The honeycomb carrier has an alumina coating on the walls of the honeycomb pores. The alumina coating has a thickness of (10-30) g / L and is formed by coating with alumina sol with an average particle size of (1-30) nm and sintering at (400-450) °C.

2. The honeycomb carrier according to claim 1, characterized in that, The thickness of the alumina coating is (16-24) g / L.

3. The honeycomb carrier according to claim 1 or 2, characterized in that, The average particle size of the alumina sol is (2-5) nm.

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