JPS596945A - Regeneration of titania catalyst - Google Patents

Abstract

PURPOSE:To regenerate a deactivated titania catalyst, by a method wherein the deactivated catalyst used in catalytic reducing reaction of nitrogen oxide due to ammonia and exposed to a high temp. gas is impregnated with a W-containing solution to support W in a specific contained ratio. CONSTITUTION:A catalyst which is a titania catalyst used in catalytic reducing reaction of nitrogen oxide due to ammonia and deactivated by exposing the same to a high temp. gas at 800 deg.C or more is immersed in a W-containing solution such as a monoethanolamine solution of WO3 to be impregnated therewith and the impregnated catalyst is taken out and dried to support W in an amount 0.37-6.6pts./TiO2 100pts. as WO3 on the basis of a wt. by the catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating a titania catalyst that has been deactivated by exposure to high temperature gas.

Nitrogen oxides (hereinafter abbreviated as NOx) emitted into the atmosphere from heat engines are the cause of photochemical smog, and in recent years there has been a great deal of interest in measures to deal with them.

Several NOx removal methods have been proposed in the past.

Among them, the method of catalytic reduction of NOx using NH3 as a reducing agent selectively reacts with NH3 or NOx even if oxygen coexists in the exhaust gas for at least one volumetric amount.
This is a cost-effective method regarding reducing agents.

500°C depending on the location of the heat engine
Rukotka may be required to remove NOx at ~700°C. Is a titania catalyst suitable for removing NOx from such high-temperature exhaust gas? As shown in the reference example below, the performance of titania catalysts significantly deteriorates when exposed to gases above 800°C for several hours. .

The present invention has been made in view of the above two points, and an object of the present invention is to provide a method for regenerating and reusing a titania catalyst that has been deactivated by being exposed to a gas at a temperature of 800° C. or higher.

The method for regenerating a catalyst according to the present invention is to impregnate a titania catalyst which is used for a catalytic reduction reaction of nitrogen oxides with ammonia and which has been deactivated by exposure to high-temperature gas with a tungsten-containing solution. This is a method for regenerating a titania catalyst, characterized in that 0.37 to 66 parts by weight of tungsten as WO3/0 parts of T i O2j O0 are supported on the titania catalyst.

In the above, as the titania catalyst, one prepared by calcining β-titanic acid obtained by hydrolysis of titanyl sulfate is often used, but it is of course possible to use one prepared by other manufacturing methods. Representative examples of tungsten-containing solutions include a monomethylamine solution of WO3 and a concentrated aqueous ammonia solution of WO3. The reason why the supported amount is limited to 037 to 66 parts/TiO2]00 parts by weight as WO3 is that the deactivated catalyst cannot be regenerated sufficiently at the lower limit of the above range, and at the northern limit of the range -1- This is because if it exceeds 100%, the pores of the tungsten or titania catalyst will be filled and the total pore volume will decrease, leading to a decrease in activity.

Reference Example β-titanic acid obtained by hydrolysis of titanyl sulfate,
The mixture was formed into agglomerates under pressure, and the agglomerates were crushed into powder particles of 8 to 4 meshes, and fired by a conventional method to obtain a titania catalyst. The catalyst was then heated for 3 hours to deactivate it.

Example 1 1 part by weight of the deactivated chikunia catalyst obtained in the reference example was mixed with WO3
monomethanolamine solution (34% by weight as WO3)
) to impregnate the catalyst with the same solution, and the catalyst was taken out and dried to support tungsten on the catalyst.

The supported amount is 66 parts by weight as WO3/T i O21
It was 00 copies.

Examples 2 to 4 As shown in Table 1, the operation of Example 1 was repeated using three types of WO3 monomethylamine solutions with different concentrations, and each deactivated titania catalyst was coated with different amounts shown in Table 1. Compatible with tungsten.

Comparative Examples 1 and 2 As shown in Table 1, the operation in Example was repeated using two types of monomethylamine solutions of WO3, one with a low concentration and one with a high concentration. Tungsten was supported by the supported poison and the high supported level.

Table 1 Activity Test The catalysts of Reference Examples, Examples, and Comparative Examples were subjected to activity tests using the method described above.

Using a fixed bed fluidized reactor equipped with a quartz reaction tube with an inner diameter of 30mm, the reaction tube was filled with catalyst (3,6me) and the test mixed gas shown in Table 2 was circulated at 11 f/m: ~11. I let it happen.

The NO concentration at the outlet of the reactor was measured, and the denitrification rate was calculated for each catalyst using a calculation formula. The results are shown in the drawing.

As can be seen from the figure, each of the regenerated catalysts of Examples exhibits excellent activity at high temperatures.

Table 2

[Brief explanation of drawings]

The figure is a graph showing the relationship between reaction temperature and denitrification rate for each catalyst. -1- Patent applicant Hitachi Zosen Corporation

Claims (1)

[Claims] A titania catalyst used in the catalytic reduction reaction of nitrogen oxides with ammonia, which has been deactivated by exposure to high-temperature stress, is impregnated with a tungsten-containing solution, and the catalyst is treated as WO3 with a weight of 0.37 ~66f!VTi021
1. A method for regenerating a titania catalyst, characterized by supporting 00 parts notanxsten.