SCR Catalyst Compositions and SCR Catalytic Articles Comprising Said Catalyst Compositions

Abstract

The present invention disclose catalyst compositions for the selective catalytic reduction of nitrogen oxides, consisting of at least one oxide of vanadium in an amount of 2.0 to 4.0 wt.-%, calculated as V.sub.2O.sub.5 and based on the total weight of the catalyst composition, at least one oxide of tungsten in an amount of 2.5 to 7.2 wt.-%, calculated as WO.sub.3 and based on the total weight of the catalyst composition, at least one oxide of antimony in an amount of 0.6 to 3.4 wt.-%, calculated as Sb.sub.2O.sub.5 and based on the total weight of the catalyst composition, at least one oxide of zirconium in an amount of 0 to 1.0 wt.-%, calculated as ZrO.sub.2 and based on the total weight of the catalyst, and at least one oxide of titanium in an amount of 84.6 to 94.9 wt.-% calculated as TiO.sub.2 and based on the total weight of the catalyst, wherein the weight ratio of the oxides of vanadium, tungsten, antimony, titanium and optionally zirconium, calculated as V.sub.2O.sub.5, WO.sub.3, Sb.sub.2O.sub.5, TiO.sub.2 and optionally ZrC.sub.2, respectively, add up to 100 wt.-%. Furthermore, SCR catalytic articles are disclosed wherein an SCR catalyst composition according to the invention is affixed in the form of a coating. Suitable catalyst carriers are corrugated substrates and cordierite monoliths. The SCR catalytic articles can be used in a method for the reduction of nitrogen oxides in exhaust gases of lean-burn internal combustion engines, and they can furthermore be comprised in an exhaust gas purification system for the treatment of diesel exhaust gas.

Claims

1. A catalyst composition for the selective catalytic reduction of nitrogen oxides, consisting of at least one oxide of vanadium in an amount of 2.0 to 4.0 wt.-%, calculated as V.sub.2O.sub.5 and based on the total weight of the catalyst composition, at least one oxide of tungsten in an amount of 2.5 to 7.2 wt.-%, calculated as WO.sub.3 and based on the total weight of the catalyst composition, at least one oxide of antimony in an amount of 0.6 to 3.4 wt.-%, calculated as Sb.sub.2O.sub.5 and based on the total weight of the catalyst composition, at least one oxide of zirconium in an amount of 0 to 1.0 wt.-%, calculated as ZrO.sub.2 and based on the total weight of the catalyst, and at least one oxide of titanium in an amount of 84.6 to 94.9 wt.-% calculated as TiO.sub.2 and based on the total weight of the catalyst, wherein the weight ratio of the oxides of vanadium, tungsten, antimony, titanium, and optionally zirconium, calculated as V.sub.2O.sub.5, WO.sub.3, Sb.sub.2O.sub.5, TiO.sub.2, and optionally ZrO.sub.2, respectively, add up to 100 wt.-%.

2. The catalyst composition according to claim 1, wherein the at least one oxide of titanium is titanium dioxide TiO2, and it comprises at least 95 wt.-% of anatase.

3. The catalyst composition according to claim 1, consisting of at least one oxide of vanadium in an amount of 2.0 to 4.0 wt.-%, calculated as V.sub.2O.sub.5 and based on the total weight of the catalyst composition, at least one oxide of tungsten in an amount of 2.5 to 7.2 wt.-%, calculated as WO.sub.3 and based on the total weight of the catalyst composition, at least one oxide of antimony in an amount of 0.6 to 3.4 wt.-%, calculated as Sb.sub.2O.sub.5 and based on the total weight of the catalyst composition, and at least on oxide of titanium in an amount of 85.6 to 94.9 wt.-% calculated as TiO.sub.2 and based on the total weight of the catalyst, wherein the weight ratio of the oxides of vanadium, tungsten, antimony and titanium, calculated as V.sub.2O.sub.5, WO.sub.3, Sb.sub.2O.sub.5, and TiO.sub.2, respectively, add up to 100 wt.-%.

4. The catalyst composition according to claim 1, consisting of at least one oxide of vanadium in an amount of 2.0 to 4.0 wt.-%, calculated as V.sub.2O.sub.5 and based on the total weight of the catalyst composition, at least one oxide of tungsten in an amount of 2.5 to 7.2 wt.-%, calculated as WO.sub.3 and based on the total weight of the catalyst composition, at least one oxide of antimony in an amount of 0.6 to 3.4 wt.-%, calculated as Sb.sub.2O.sub.5 and based on the total weight of the catalyst composition, at least one oxide of zirconium in an amount of 0.2 to 1.0 wt.-%, calculated as ZrO.sub.2 and based on the total weight of the catalyst, and at least on oxide of titanium in an amount of 84.6 to 94.7 wt.-% calculated as TiO.sub.2 and based on the total weight of the catalyst, wherein the weight ratio of the oxides of vanadium, tungsten, antimony, titanium and zirconium, calculated as V.sub.2O.sub.5, WO.sub.3, Sb.sub.2O.sub.5, TiO.sub.2, and ZrO.sub.2, respectively, add up to 100 wt. %.

5. An SCR catalytic article comprising a catalyst substrate onto which an SCR catalyst composition according to claim 1 is affixed in the form of a coating.

6. The SCR catalytic article according to claim 5, wherein the catalyst substrate is selected from corrugated substrates and cordierite monoliths.

7. The SCR catalytic article according to claim 6, wherein the catalyst substrate is a cordierite monolith selected from wall-flow filters and flow-through substrates.

8. A method for the reduction of nitrogen oxides in exhaust gases of lean-burn internal combustion engines, comprising adding a reducing agent to the exhaust-gas containing nitrogen oxides, and passing the resulting mixture of exhaust-gas containing nitrogen oxides and reducing agent over a catalytic article according to claim 5.

9. An exhaust gas purification system for the treatment of diesel exhaust gas, comprising an oxidation catalyst, a diesel particle filter, and a catalytic article according to claim 5.

10. An exhaust gas purification system for the treatment of diesel exhaust gas, comprising an oxidation catalyst, and a diesel particle filter on which a catalyst composition according to claim 1 is present as a coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0127] FIG. 1 shows the NO.sub.x conversion at 200 C. in the fresh and the aged state as a function of the amount of V.sub.2O.sub.5 in wt.-% in catalyst compositions comprising 3.6 wt.-% WO.sub.3 and 1.6 wt.-% Sb.sub.2O.sub.5 compared to a catalyst comprising 2.7 wt.-% V.sub.2O.sub.5, 4.0 wt.-% WO.sub.3 and 0 wt.-% Sb.sub.2O.sub.5.

[0128] FIG. 2 shows the N.sub.2O formation at 550 C. in the fresh and the aged state as a function of the amount of V.sub.2O.sub.5 in wt.-% in catalyst compositions comprising 3.6 wt.-% WO.sub.3 and 1.6 wt.-% Sb.sub.2O.sub.5 compared to a catalyst comprising 2.7 wt.-% V.sub.2O.sub.5, 4.0 wt.-% WO.sub.3 and 0 wt.-% Sb.sub.2O.sub.5.

[0129] FIG. 3 shows the NO.sub.x conversion at 200 C. in the fresh and the aged state as a function of the amount of WO.sub.3 in wt.-% in catalyst compositions comprising 2.4 wt.-% V.sub.2O.sub.5 and 1.6 wt.-% Sb.sub.2O.sub.5 compared to catalysts comprising 2.7 wt.-% V.sub.2O.sub.5, 0 wt.-% Sb.sub.2O.sub.5.

[0130] FIG. 4 shows the N.sub.2O formation at 550 C. in the fresh and the aged state as a function of the amount of WO.sub.3 in wt.-% in catalyst compositions comprising 2.4 wt.-% V.sub.2O.sub.5 and 1.6 wt.-% Sb.sub.2O.sub.5 compared to catalysts comprising 2.7 wt.-% V.sub.2O.sub.5, and 0 wt.-% Sb.sub.2O.sub.5.

[0131] FIG. 5 shows the NO.sub.x conversion as a function of the amount of Sb.sub.2O.sub.5 for fresh catalyst compositions.

[0132] FIG. 6 shows the NO.sub.x conversion as a function of the amount of Sb.sub.2O.sub.5 for aged catalyst compositions.

[0133] FIG. 7 shows the NOx conversion and the N.sub.2O formation at 550 C. for a sample containing 0 wt.-% ZrO.sub.2.

[0134] FIG. 8 shows the NO.sub.x conversion and the N.sub.2O formation at 550 C. for a sample made with the one-pot method.

EMBODIMENTS

Embodiment 1: Preparation of SCR Catalytic Articles Having Corrugated Catalyst Substrates

[0135] SCR catalytic articles according to the present invention were prepared. Corrugated substrates were used as the catalyst substrates, and SCR catalyst compositions according to the present invention as well as some comparative catalyst compositions where affixed to them.

Preparation of the Catalytic Articles Having Corrugated Catalyst Substrates

[0136] A water-based slurry containing TiO.sub.2 (anatase) and ZrO(NO.sub.3).sub.2 having a dry matter content of 57 to 59 wt.-% was applied on a corrugated substrate with a cpsi of 260, wherein cpsi stands for cells per square inch. The substrate was then calcined at 580 C. Subsequently, impregnation solutions were prepared by mixing A grams of a water-based solution containing vanadyl oxalate (7.15% V), B grams of an aqueous solution of ammonium metatungstate (39.36% W), C grams of deionized water, D grams of tartaric acid and E grams of antimony acetate (Sb(OAc).sub.3) in different amounts (see Table 1). The substrate was then dipped into the impregnation solution for 20 seconds, dried and then thermally treated at 450 C. resulting in a catalytic load of % V.sub.2O.sub.5, % WO.sub.3, % Sb.sub.2O.sub.5, % ZrO.sub.2 based on the total weight of the catalyst composition, as shown in Table 1.

TABLE-US-00001 TABLE 1 Preparation of the catalytic articles having corrugated catalyst substrates and V.sub.2O.sub.5, WO.sub.3 and Sb.sub.2O.sub.5 contents of the catalytic articles obtained A: B: D: % % % % Wash- g[V g[W g E: V.sub.2O.sub.5 WO.sub.3 Sb.sub.2O.sub.5 ZrO.sub.2 coat Ex. stock stock C: (Tartaric g (Sb [wt.- [wt.- [wt.- [wt.- loading No. solution] solution] g(H.sub.2O) acid) (OAc).sub.3) %] %] %] %] [g/L] 1 160 0 290 60 24 2.5 0.0 1.6 0.4 420 2 156 58 236 60 24 2.5 3.5 1.6 0.4 440 3 152 114 184 60 24 2.4 7.2 1.6 0.4 460 4 218 0 232 60 24 3.4 0.0 1.6 0.4 430 5 213 58 179 60 24 3.4 3.6 1.6 0.4 450 6 207 113 129 60 24 3.4 7.2 1.6 0.4 460 7 161 0 289 0 0 2.7 0.0 0.0 0.4 450 8 157 59 234 0 0 2.7 4.0 0.0 0.4 420 9 153 115 183 0 0 2.7 8.1 0.0 0.4 430 10 155 87 208 60 24 2.5 5.3 1.6 0.4 430 11 186 59 206 60 24 3.0 3.6 1.6 0.4 420 12 155 58 237 60 24 2.5 3.5 1.6 0.4 450 13 154 72 224 60 24 2.5 4.4 1.6 0.4 450 14 169 58 223 60 24 2.7 3.6 1.6 0.4 450 15 157 29 264 60 24 2.5 1.8 1.6 0.4 440 16 156 44 251 60 24 2.5 2.7 1.6 0.4 440 17 153 49 248 60 24 2.5 3.1 1.6 0.4 420 18 167 43 240 60 24 2.7 2.7 1.6 0.4 420 19 168 29 253 60 24 2.7 1.8 1.6 0.4 420 20 167 49 234 60 24 2.7 3.1 1.6 0.4 420 21 182 29 239 60 24 3.0 1.8 1.6 0.4 420 22 181 43 226 60 24 3.0 2.7 1.6 0.4 420 23 181 49 220 60 24 3.0 3.1 1.6 0.4 420 24 175 55 220 60 36 2.8 3.5 2.5 0.4 430 25 175 55 220 60 48 2.8 3.4 3.3 0.4 430 26 152 57 241 60 12 2.5 3.6 0.8 0.4 420

[0137] It has to be noted that Examples 1, 4, 7, 8 and 9 in Table 1 are comparative Examples, because they either do not comprise tungsten, or antimony, or neither tungsten nor antimony.

Embodiment 2: NOx Conversion and N.SUB.2.O Formation of the SCR Catalytic Articles Having Corrugated Catalyst Substrates

[0138] The NOx conversion and N.sub.2O formation of the Examples according to Embodiment 1 were tested in the fresh state and after aging at the following conditions:

[0139] NOx (250 ppm), NH.sub.3 (300 ppm), H.sub.2O (4%), O.sub.2 (12%), GSVH=100,000 h.sup.1, N.sub.2 to balance. The NOx conversion was measured at 200, 250, 300, 350, 400, 450, 500 and 550 C.

[0140] Aging was performed at 100 h at 550 C., H.sub.2O=(10%), GSVH=10,000 h.sup.1.

[0141] All percentages given above refer to volume percent.

[0142] GHSV is the gas hourly space velocity.

[0143] Based on the inlet and outlet NO.sub.x concentration, the NO.sub.x conversion is calculated as

[00001]$\begin{array}{cc}X=\frac{\left({\mathrm{NO}x}_{\mathrm{in}}-{\mathrm{NO}x}_{out}\right)}{{\mathrm{NO}x}_{\mathrm{in}}}*100\%& \left(5\right)\end{array}$ [0144] wherein [0145] X: NO.sub.x conversion in percent [0146] NOx.sub.in: NO.sub.x concentration at the inlet end of the SCR catalytic article [0147] NOx.sub.out: NO.sub.x concentration at the outlet end of the SCR catalytic article

[0148] The NO.sub.x concentrations at the inlet resp. the outlet end can be indicated in mol or as mass. The NO.sub.x and N.sub.2O concentrations were measured by FTIR.

[0149] The results of the NOx conversion and the N.sub.2O formation for the fresh and aged examples are shown in Tables 2 and 3.

[0150] X(T) indicates the NO.sub.x conversion at a temperature T in C. The N.sub.2O formation was measured at 550 C.

TABLE-US-00002 TABLE 2 NO.sub.x conversion and N.sub.2O formation at 550 C. of the fresh Examples 1 to 26 Ex. X X X X X X X X N2O No. (550) (500) (450) (400) (350) (300) (250) (200) (550) 1 0.44 0.69 0.74 0.75 0.72 0.65 0.43 0.15 0.032 2 0.44 0.78 0.89 0.92 0.91 0.87 0.72 0.39 0.062 3 0.44 0.80 0.92 0.95 0.94 0.89 0.73 0.38 0.095 4 0.31 0.72 0.86 0.89 0.89 0.85 0.72 0.39 0.075 5 0.23 0.72 0.91 0.95 0.95 0.92 0.82 0.55 0.119 6 0.18 0.68 0.88 0.92 0.92 0.89 0.78 0.49 0.140 7 0.28 0.63 0.78 0.81 0.79 0.71 0.49 0.19 0.068 8 0.24 0.63 0.81 0.85 0.85 0.82 0.68 0.35 0.104 9 0.25 0.72 0.90 0.95 0.94 0.89 0.74 0.39 0.142 10 0.25 0.75 0.92 0.96 0.95 0.91 0.77 0.40 0.120 11 0.13 0.70 0.92 0.96 0.96 0.92 0.81 0.48 0.127 12 0.38 0.78 0.91 0.94 0.94 0.89 0.75 0.40 0.081 13 0.36 0.78 0.92 0.95 0.94 0.90 0.77 0.42 0.089 14 0.33 0.76 0.91 0.94 0.94 0.90 0.78 0.45 0.091 15 0.41 0.76 0.87 0.90 0.90 0.85 0.69 0.34 0.058 16 0.43 0.79 0.91 0.93 0.93 0.88 0.73 0.38 0.071 17 0.37 0.77 0.90 0.93 0.93 0.89 0.75 0.39 0.090 18 0.31 0.76 0.92 0.95 0.95 0.91 0.77 0.42 0.096 19 0.32 0.76 0.91 0.94 0.94 0.90 0.75 0.40 0.086 20 0.34 0.76 0.90 0.93 0.92 0.87 0.72 0.37 0.115 21 0.29 0.75 0.91 0.94 0.94 0.90 0.77 0.43 0.095 22 0.26 0.74 0.91 0.95 0.94 0.91 0.79 0.46 0.104 23 0.27 0.74 0.91 0.95 0.94 0.91 0.79 0.46 0.105 24 0.12 0.69 0.91 0.95 0.96 0.92 0.81 0.46 0.109 25 0.14 0.70 0.90 0.94 0.95 0.91 0.78 0.43 0.095 26 0.42 0.80 0.92 0.95 0.94 0.90 0.75 0.40 0.10

TABLE-US-00003 TABLE 3 NO.sub.x conversion and N.sub.2O formation at 550 C. of the aged Examples 1 to 26 X X X X X X X X N2O Ex. (550) (500) (450) (400) (350) (300) (250) (200) (550) No aged aged aged aged aged aged aged aged aged 1 0.41 0.74 0.83 0.85 0.85 0.80 0.63 0.27 0.081 2 0.36 0.77 0.91 0.93 0.93 0.87 0.72 0.38 0.107 3 0.38 0.77 0.89 0.92 0.92 0.87 0.71 0.37 0.112 4 0.04 0.54 0.83 0.91 0.92 0.89 0.78 0.47 0.168 5 0.00 0.59 0.87 0.93 0.93 0.88 0.74 0.43 0.156 6 0.02 0.60 0.88 0.93 0.93 0.88 0.73 0.41 0.160 7 0.11 0.41 0.71 0.78 0.80 0.73 0.52 0.22 0.127 8 0.04 0.52 0.83 0.91 0.90 0.82 0.62 0.29 0.149 9 0.02 0.55 0.84 0.90 0.90 0.82 0.62 0.29 0.147 10 0.26 0.75 0.92 0.95 0.94 0.90 0.74 0.38 0.130 11 0.02 0.63 0.89 0.94 0.94 0.89 0.73 0.40 0.153 12 0.36 0.77 0.91 0.93 0.93 0.87 0.72 0.38 0.107 13 0.30 0.75 0.91 0.94 0.93 0.88 0.73 0.38 0.119 14 0.21 0.71 0.90 0.93 0.93 0.88 0.73 0.39 0.133 15 0.30 0.74 0.88 0.91 0.91 0.86 0.69 0.34 0.113 16 0.34 0.76 0.90 0.93 0.92 0.87 0.72 0.37 0.115 17 0.31 0.76 0.90 0.93 0.92 0.88 0.71 0.35 0.125 18 0.21 0.72 0.90 0.94 0.93 0.88 0.73 0.38 0.136 19 0.22 0.71 0.89 0.93 0.93 0.88 0.72 0.37 0.132 20 0.23 0.73 0.91 0.94 0.93 0.88 0.73 0.38 0.131 21 0.12 0.67 0.89 0.93 0.93 0.88 0.73 0.39 0.150 22 0.09 0.65 0.88 0.92 0.92 0.87 0.72 0.38 0.147 23 0.11 0.67 0.90 0.94 0.93 0.88 0.72 0.39 0.148 24 0.18 0.71 0.90 0.94 0.94 0.90 0.77 0.42 0.125 25 0.24 0.73 0.90 0.94 0.94 0.90 0.75 0.41 0.104 26 0.20 0.69 0.89 0.92 0.92 0.86 0.68 0.33 0.15

Embodiment 3: NO.SUB.x .Conversion and N.SUB.2.O Formation as a Function of the Amount of V.SUB.2.O.SUB.5

[0151] The NO.sub.x conversion at 200 C. in the fresh and the aged state as a function of the amount of V.sub.2O.sub.5 in wt.-% in catalyst compositions comprising 3.6 wt.-% WO.sub.3 and 1.6 wt.-% Sb.sub.2O.sub.5 is shown in FIG. 1. For comparison a catalyst comprising 2.7 wt.-% V.sub.2O.sub.5, 4.0 wt.-% WO.sub.3 and 0 wt.-% Sb.sub.2O.sub.5 is also shown. All amounts given for the respective oxides refer to the total amount of the catalyst composition. The balance to 100 wt.-% is represented by TiO.sub.2.

[0152] The aging of the catalyst composition and the measurement of the NOx conversion were carried out as described above.

[0153] Table 4 lists the catalyst compositions and the Nox conversions.

[0154] The results are shown in FIG. 1.

TABLE-US-00004 TABLE 4 NO.sub.x conversion at 200 C. in the fresh and the aged state as a function of the amount of V.sub.2O.sub.5 in wt.-% in catalyst compositions comprising 3.6 wt.-% WO.sub.3 and 1.6 wt.-% Sb.sub.2O.sub.5 compared to a catalyst comprising 2.7 wt.-% V.sub.2O.sub.5, 4.0 wt.-% WO.sub.3 and 0 wt.-% Sb.sub.2O.sub.5. V.sub.2O.sub.5 WO.sub.3 Sb.sub.2O.sub.5 NO.sub.x NO.sub.x Example (wt.-%) (wt.-%) (wt.-%) (fresh) (aged) 2 2.5 (3.5) 1.6 0.39 0.38 5 3.4 3.6 1.6 0.55 0.43 8 2.7 4.0 0.0 0.35 0.29 11 (3.0) 3.6 1.6 0.48 0.40 12 2.5 (3.5) 1.6 0.40 0.38 14 2.7 3.6 1.6 0.45 0.39

[0155] The N.sub.2O formation at 550 C. in the fresh and the aged state as a function of the amount of V.sub.2O.sub.5 in wt.-% in catalyst compositions comprising 3.6 wt.-% WO.sub.3 and 1.6 wt.-% Sb.sub.2O.sub.5 is shown in FIG. 2. For comparison a catalyst comprising 2.7 wt.-% V.sub.2O.sub.5, 4.0 wt.-% WO.sub.3 and 0 wt.-% Sb.sub.2O.sub.5 is also shown. All amounts given for the respective oxides refer to the total amount of the catalyst composition. The balance to 100 wt.-% is represented by TiO.sub.2.

[0156] The aging of the catalyst composition and the measurement of the N.sub.2O formation were carried out as described above.

[0157] Table 5 lists the catalyst compositions and the N.sub.2O formation.

[0158] The results are shown in FIG. 2.

TABLE-US-00005 TABLE 5 N.sub.2O formation at 550 C. in the fresh and the aged state as a function of the amount of V.sub.2O.sub.5 in wt.-% in catalyst compositions comprising 3.6 wt.-% WO.sub.3 and 1.6 wt.-% Sb.sub.2O.sub.5 compared to a catalyst comprising 2.7 wt.-% V.sub.2O.sub.5, 4.0 wt.-% WO.sub.3 and 0 wt.-% Sb.sub.2O.sub.5. V.sub.2O.sub.5 WO.sub.3 Sb.sub.2O.sub.5 N.sub.2O N.sub.2O Example (wt.-%) (wt.-%) (wt.-%) (fresh) (aged) 2 2.5 (3.5) 1.6 0.06 0.11 5 3.4 3.6 1.6 0.12 0.16 8 2.7 4.0 0.0 0.104 0.149 11 (3.0) 3.6 1.6 0.13 0.15 12 2.5 (3.5) 1.6 0.08 0.11 14 2.7 3.6 1.6 0.09 0.13

Embodiment 3: NO.SUB.x .Conversion and N.SUB.2.O Formation as a Function of the Amount of WO.SUB.3

[0159] The NO.sub.x conversion at 200 C. in the fresh and the aged state as a function of the amount of WO.sub.3 in wt.-% in catalyst compositions comprising 2.4 wt.-% V.sub.2O.sub.5 and 1.6 wt.-% Sb.sub.2O.sub.5 Is shown in FIG. 1. For comparison, catalysts comprising 2.7 wt-% V.sub.2O.sub.5, 0 wt.-% Sb.sub.2O.sub.5 and variable amounts of WO.sub.3 are also shown. All amounts given for the respective oxides refer to the total amount of the catalyst composition. The balance to 100 wt.-% is represented by TiO.sub.2.

[0160] The aging of the catalyst composition and the measurement of the NOx conversion were carried out as described above.

[0161] Table 6 lists the catalyst compositions and the NOx conversions.

[0162] The results are shown in FIG. 3.

TABLE-US-00006 TABLE 6 NO.sub.x conversion at 200 C. in the fresh and the aged state as a function of the amount of WO.sub.3 in wt.-% in catalyst compositions comprising 2.4 wt.-% V.sub.2O.sub.5 and 1.6 wt.-% Sb.sub.2O.sub.5 compared to catalysts comprising 2.7 wt.-% V.sub.2O.sub.5, 1.6 wt.-% or 0 wt.-% Sb.sub.2O.sub.5 and variable amounts of WO.sub.3 V.sub.2O.sub.5 WO.sub.3 Sb.sub.2O.sub.5 NO.sub.x NO.sub.x Example (wt.-%) (wt.-%) (wt.-%) (fresh) (aged) 1 2.5 0.0 1.6 0.15 0.27 2 2.5 3.5 1.6 0.39 0.38 3 2.4 7.2 1.6 0.38 0.37 7 2.7 0.0 0.0 0.19 0.22 8 2.7 4.0 0.0 0.35 0.29 9 2.7 8.1 0.0 0.39 0.29 10 2.5 5.3 1.6 0.4 0.38 12 2.5 3.6 1.6 0.4 0.38 13 2.5 4.4 1.6 0.42 0.38 15 2.5 1.8 1.6 0.34 0.34 16 2.5 2.7 1.6 0.38 0.37 17 2.5 3.1 1.6 0.39 0.35

[0163] The N.sub.2O formation at 550 C. in the fresh and the aged state as a function of the amount of WO.sub.3 in wt-% in catalyst compositions comprising 2.4 wt.-% V.sub.2O.sub.5 and 1.6 wt.-% Sb.sub.2O.sub.5 Is shown in FIG. 4. For comparison, catalysts comprising 2.7 wt.-% V.sub.2O.sub.5, 0 wt.-% Sb.sub.2O.sub.5 and variable amounts of WO.sub.3 are also shown. All amounts given for the respective oxides refer to the total amount of the catalyst composition. The balance to 100 wt.-% is represented by TiO.sub.2.

[0164] The aging of the catalyst composition and the measurement of the N.sub.2O formation were carried out as described above.

[0165] Table 7 lists the catalyst compositions and the N.sub.2O formations.

[0166] The results are shown in FIG. 4.

TABLE-US-00007 TABLE 7 N.sub.2O formation at 550 C. in the fresh and the aged state as a function of the amount of WO.sub.3 in wt.-% in catalyst compositions comprising 2.4 wt.-% V.sub.2O.sub.5 and 1.6 wt.-% Sb.sub.2O.sub.5 compared to a catalyst comprising 2.7 wt.-% V.sub.2O.sub.5, and 1.6 wt.-% or 0 wt.-% Sb.sub.2O.sub.5 and variable amounts of WO.sub.3 V.sub.2O.sub.5 WO.sub.3 Sb.sub.2O.sub.5 N.sub.2O N.sub.2O Example (wt.-%) (wt.-%) (wt.-%) (fresh) (aged) 1 2.5 0.0 1.6 0.03 0.08 2 2.5 3.5 1.6 0.06 0.11 3 2.4 7.2 1.6 0.09 0.11 7 2.7 0.0 0.0 0.068 0.13 8 2.7 4.0 0.0 0.104 0.15 9 2.7 8.1 0.0 0.142 0.15 10 2.5 5.3 1.6 0.12 0.13 12 2.5 3.5 1.6 0.08 0.11 13 2.5 4.4 1.6 0.09 0.12 15 2.5 1.8 1.6 0.06 0.11 16 2.5 2.7 1.6 0.07 0.12 17 2.5 3.1 1.6 0.09 0.13

Embodiment 4: NO.SUB.x .Conversion and N.SUB.2.O Formation as a Function of the Amount of Sb.SUB.2.O.SUB.5

[0167] Examples 2 and 26, containing antimony, show a higher stability and higher fresh performance than examples 8 and 9, not containing antimony.

[0168] Example 9 demonstrates that fresh performance can be compensated for by increasing the tungsten content in formulations not containing antimony. However, the thermal stability cannot be achieved without adding antimony.

[0169] Table 8 shows the NO.sub.x conversion and N.sub.2O formation as a function of the amount of Sb.sub.2O.sub.5 for the fresh catalyst compositions. The results for the NO.sub.x conversion are shown in FIG. 5.

[0170] Table 9 shows the NO.sub.x conversion and N.sub.2O formation as a function of the amount of Sb.sub.2O.sub.5 for the aged catalyst compositions. The results for the NO.sub.x conversion are shown in FIG. 6.

TABLE-US-00008 TABLE 8 NO.sub.x conversion and N.sub.2O formation as a function of the amount of Sb.sub.2O.sub.5 for fresh catalyst compositions 2, 8, 9 and 26 Ex. X X X X X X X X N2O No. (550) (500) (450) (400) (350) (300) (250) (200) (550) 2 0.44 0.78 0.89 0.92 0.91 0.87 0.72 0.39 0.06 26 0.42 0.80 0.92 0.95 0.94 0.90 0.75 0.40 0.10 8 0.24 0.63 0.81 0.85 0.85 0.82 0.68 0.35 0.104 9 0.25 0.72 0.9 0.95 0.94 0.89 0.74 0.39 0.142

TABLE-US-00009 TABLE 9 NO.sub.x conversion and N.sub.2O formation as a function of the amount of Sb.sub.2O.sub.5 for fresh catalyst compositions 2, 8, 9 and 26 Ex. X X X X X X X X N2O No. (550) (500) (450) (400) (350) (300) (250) (200) (550) 2 0.36 0.77 0.91 0.93 0.93 0.87 0.72 0.38 0.11 26 0.20 0.69 0.89 0.92 0.92 0.86 0.68 0.33 0.15 8 0.04 0.52 0.83 0.91 0.9 0.82 0.62 0.29 0.149 9 0.02 0.55 0.84 0.9 0.9 0.82 0.62 0.29 0.147

[0171] The embodiments above show that the addition of antimony improves the thermal stability of the catalyst compositions. If antimony is present in the catalyst composition, lower amounts of vanadium and tungsten, respectively, are required to obtain a denitrification activity in range of a catalyst comprising only vanadium and tungsten, but no antimony.

[0172] In contradiction to the prior art, is has been shown that WO.sub.3 is necessary to achieve a good fresh performance of the catalyst composition, as can be seen from FIG. 2.

Embodiment 5: NO.SUB.x .Conversion and N.SUB.2.O Formation of a Sample Containing 0% ZrO.SUB.2

[0173] A water-based slurry containing TiO.sub.2 (anatase) having a dry matter content of 55% was applied on a corrugated substrate with a cpsi of 260. The zirconium free substrate was then calcined at 580 C. Subsequently, impregnation solutions were prepared by mixing 215 grams of a water-based solution containing vanadyl oxalate (7.15% V), 72 grams of an aqueous solution of ammonium metatungstate (39.36% W), 151 grams of deionized water, 59 grams of tartaric acid and 28 grams of antimony acetate. The substrate was then dipped into the impregnation solution for 20 seconds, dried and then thermally treated at 450 C. resulting in a catalytic load of % V.sub.2O.sub.5, % WO.sub.3, % Sb.sub.2O.sub.5, based on the total weight of the catalyst composition, of 3.1, 4.0 and 1.7%, respectively. The sample labelled 27 was measured at:

[0174] NOx (250 ppm), NH.sub.3 (300 ppm), H.sub.2O (4%), O.sub.2 (12%), GSVH=100000 h.sup.1, N.sub.2 to balance. The NOx conversion was measured at 200, 250, 300, 350, 400, 450, 500 and 550 C.

[0175] Aging was performed at 100 h at 550 C., H.sub.2O=(10%), GSVH=10000 h.sup.1.

[0176] The results are shown in FIG. 7 and Tab. 10.

TABLE-US-00010 TABLE 10 NO.sub.x conversion and N.sub.2O formation for fresh and aged catalyst 27 X X X X X X X X N2O (550) (500) (450) (400) (350) (300) (250) (200) (550) 27 0.25 0.71 0.90 0.94 0.94 0.92 0.81 0.48 0.11 FRESH 27 AGED 0.11 0.63 0.87 0.92 0.92 0.87 0.72 0.38 0.13

Embodiment 6: NOx Conversion and N.SUB.2.O Formation of a Sample Made with the One-Pot Method

[0177] A water-based slurry containing TiO.sub.2 (anatase), VO.sub.2, Sb.sub.2(glycolate).sub.3, WO.sub.3 and having a dry matter content of 55% was applied a corrugated substrate with a cpsi of 260 and then calcined at 580 C. resulting in a catalytic load of % V.sub.2O.sub.5, % WO.sub.3, % Sb.sub.2O.sub.5, based on the total weight of the catalyst composition, of 3.2, 4.0, and 2.0%, respectively. The sample labelled 28 was measured at:

[0178] NOx (250 ppm), NH.sub.3 (300 ppm), H.sub.2O (4%), O.sub.2 (12%), GSVH=100000 h.sup.1, N.sub.2 to balance. The NOx conversion was measured at 200, 250, 300, 350, 400, 450, 500 and 550 C.

[0179] Aging was performed at 100 h at 550 C., H.sub.2O=(10%), GSVH=10000 h.sup.1.

[0180] The results are shown in FIG. 8 and Tab. 11.

TABLE-US-00011 TABLE 11 NO.sub.x conversion and N.sub.2O formation for fresh and aged catalyst 28 X X X X X X X X N2O (550) (500) (450) (400) (350) (300) (250) (200) (550) 28 0.28 0.78 0.93 0.96 0.95 0.92 0.81 0.51 0.12 FRESH 28 0.13 0.70 0.90 0.94 0.93 0.89 0.75 0.42 0.16 AGED

Embodiment 7: Sample Made with the One-Pot Method on a Cordierite Substrate

[0181] A water-based slurry containing TiO.sub.2 (anatase), VO.sub.2, WO.sub.3, Sb.sub.2O.sub.5 and having a dry matter content of 55% was applied on a cordierite substrate with a cpsi of 300 and then calcined at 580 C. resulting in a catalytic load of % V.sub.2O.sub.5, % WO.sub.3, % Sb.sub.2O.sub.5, based on the total weight of the catalyst composition, of 3.2, 4.0, and 2.0%, respectively.

[0182] The sample labelled 29 was measured at:

[0183] NOx (250 ppm), NH.sub.3 (300 ppm), H.sub.2O (4%), O.sub.2 (12%), GSVH=100000 h.sup.1, N.sub.2 to balance. The NOx conversion was measured at 200, 250, 300, 350, 400, 450, 500 and 550 C.

[0184] Aging was performed at 100 h at 550 C., H.sub.2O=(10%), GSVH=10000 h.sup.1.

[0185] The NOx conversion and the N.sub.2O formation are comparable to that of Embodiment 6.