Catalytic titanium dioxide mixtures, catalysts and catalyst systems containing the same, processes for making the same, and uses therefor

1. A process for preparing a catalyst material, the process comprising:

(a) providing a first anatase titanium dioxide having a BET surface area greater than 15 m 2 /g and a hydrogen uptake for the reduction of Ti 4+ to Ti 3+ of from 5 to 20 μmol/m 2 ;

(b) providing a second anatase titanium dioxide having a BET surface area less than or equal to 15 m 2 /g, which is different than the surface area of the first anatase titanium dioxide, and a hydrogen uptake for the reduction of Ti 4+ to Ti 3+ of from 0.6 to 7 μmol/m 2 ; and

(c) admixing the first anatase titanium dioxide with the second anatase titanium dioxide to form a titanium dioxide mixture;

wherein the hydrogen uptake of the first anatase titanium dioxide and the second anatase titanium dioxide are determined by measuring hydrogen consumption of an amount of a sample of each of the first anatase titanium dioxide and the second anatase titanium dioxide by gas chromatography and normalizing hydrogen consumption to the amount and surface area of each sample.

2. The process according to claim 1 , wherein the first anatase titanium dioxide has a BET surface area of 18 to 90 m 2 /g.

3. The process according to claim 2 , wherein the first anatase titanium dioxide has a hydrogen uptake for the reduction of Ti 4+ to Ti 3+ of from 5 to 17 μmol/m 2 .

4. The process according to claim 3 , wherein the second anatase titanium dioxide has a BET surface area of 3 to 15 m 2 /g and a hydrogen uptake for the reduction of Ti 4+ to Ti 3+ of from 0.6 to 5 μmol/m 2 .

5. The process according to claim 4 , wherein the first anatase titanium dioxide and the second anatase titanium dioxide are admixed in a ratio of 0.5:1 to 6:1.

6. The process according to claim 1 , wherein the first anatase titanium dioxide has a hydrogen uptake for the reduction of Ti 4+ to Ti 3+ of from 5 to 17 μmol/m 2 .

7. The process according to claim 1 , wherein the second anatase titanium dioxide has a BET surface area of 3 to 15 m 2 /g.

8. The process according to claim 7 , wherein the second anatase titanium dioxide has a hydrogen uptake for the reduction of Ti 4+ to Ti 3+ of from 0.6 to 5 μmol/m 2 .

9. The process according to claim 1 , wherein the second anatase titanium dioxide has a hydrogen uptake for the reduction of Ti 4+ to Ti 3+ of from 0.6 to 5 μmol/m 2 .

10. The process according to claim 1 , wherein the first anatase titanium dioxide and the second anatase titanium dioxide are admixed in a ratio of 0.5:1 to 6:1.

11. A catalytic titanium dioxide mixture comprising: a first anatase titanium dioxide having a BET surface area greater than 15 m 2 /g and a hydrogen uptake for the reduction of Ti 4+ to Ti 3+ of from 5 to 20 μmol/m 2 ; and a second anatase titanium dioxide having a BET surface area less than or equal to 15 m 2 /g, which is different than the surface area of the first anatase titanium dioxide, and a hydrogen uptake for the reduction of Ti 4+ to Ti 3+ of from 0.6 to 7 μmol/m 2 ;

wherein the hydrogen uptake of the first anatase titanium dioxide and the second anatase titanium dioxide are determined by measuring hydrogen consumption of an amount of a sample of each of the first anatase titanium dioxide and the second anatase titanium dioxide by gas chromatography and normalizing hydrogen consumption to the amount and surface area of each sample.

12. The catalytic titanium dioxide mixture according to claim 11 , wherein the first anatase titanium dioxide and the second anatase titanium dioxide are present in a ratio of 0.5:1 to 6:1.

13. A catalyst comprising an active composition on a support material, wherein the active composition is present in an amount of 5 to 15% by weight, based on the catalyst, and wherein the active composition comprises 3 to 30% by weight of V 2 O 5 , 0 to 4% by weight of Sb 2 O 3 , 0 to 1.0% by weight of P, 0 to 1.5% by weight of alkali, calculated as alkali metal, and a catalytic titanium dioxide mixture according to claim 11 .

14. The catalyst according to claim 13 , wherein the first anatase titanium dioxide and the second anatase titanium dioxide are present in a ratio of 0.5:1 to 6:1.

15. A catalyst system comprising two or more superposed catalyst zones, wherein an uppermost of the superposed catalyst zones comprises a catalyst according to claim 14 .

16. A catalyst system comprising two or more superposed catalyst zones, wherein an uppermost of the superposed catalyst zones comprises a catalyst according to claim 13 .

17. A process comprising: (a) providing a compound selected from the group consisting of xylene, naphthalene and mixtures thereof; and (b) subjecting the compound to gas phase oxidation with a gas comprising molecular oxygen in the presence of a catalyst system according to claim 16 .

18. A process comprising: (a) providing a compound selected from the group consisting of xylene, naphthalene and mixtures thereof; and (b) subjecting the compound to gas phase oxidation with a gas comprising molecular oxygen in the presence of a catalyst according to claim 13 .

19. A catalyst system comprising at least three superposed catalyst zones;

wherein an uppermost zone of the at least three catalyst zones nearest a reactor inlet comprises a first catalyst comprising an active composition on a support material, wherein the active composition is present in an amount of 7 to 10% by weight, based on the first catalyst, and wherein the active composition comprises 6 to 11% by weight of V 2 O 5 , 0 to 3% by weight of Sb 2 O 3 , 0.1 to 1% by weight of alkali, calculated as alkali metal, and, as balance to 100% by weight, a catalytic titanium dioxide mixture according to claim 11 ;

wherein a next lower zone of the at least three catalyst zones comprises a second catalyst comprising an active composition on a support material, wherein the active composition is present in an amount of 7 to 12% by weight, based on the second catalyst, and wherein the active composition comprises 5 to 13% by weight of V 2 O 5 , 0 to 3% by weight of Sb 2 O 3 , 0 to 0.4% by weight of P, 0 to 0.4% by weight of alkali, calculated as alkali metal, and an anatase titanium dioxide, as balance;

and wherein a lowest zone of the at least three catalyst zones nearest a reactor outlet comprises a third catalyst comprising an active composition on a support material, wherein the active composition is present in an amount of 8 to 12% by weight, based on the third catalyst, and wherein the active composition comprises 5 to 30% by weight of V 2 O 5 , 0 to 3% by weight of Sb 2 O 3 , 0.05 to 0.4% by weight of P, 0 to 0.3% by weight of alkali, calculated as alkali metal, and an anatase titanium dioxide, as balance.

20. The catalyst system according to claim 19 , wherein the next lower zone comprises two catalyst subzones, wherein the upper subzone of the two catalyst subzones comprises an upper subzone catalyst comprising an active composition on a support material, wherein the active composition is present in an amount of 7 to 12% by weight, based on the upper subzone catalyst, and wherein the active composition comprises 4 to 15% by weight of V 2 O 5 , 0 to 3% by weight of Sb 2 O 3 , 0.1 to 1% by weight of alkali, calculated as alkali metal, 0 to 0.4% by weight of P, and an anatase titanium dioxide, as balance; and wherein the lower subzone of the two catalyst subzones comprises a lower subzone catalyst comprising an active composition on a support material, wherein the active composition is present in an amount of 7 to 12% by weight, based on the lower subzone catalyst, and wherein the active composition comprises 5 to 15% by weight of V 2 O 5 , 0 to 3% by weight of Sb 2 O 3 , 0 to 0.4% by weight of alkali, calculated as alkali metal, 0 to 0.4% by weight of P, and an anatase titanium dioxide, as balance.