초록 ▼

In a method for the preparation of pyromellitic acid or its anhydride by catalytic vapor phase oxidation of a tetra-C1-C4-alkylbenzene using a catalyst comprising catalytically active material composed of 1 to 20 parts by weight of V2O5, 99 to 80 parts by weight of TiO2 and/or SnO2 and/or ZrO2, and

In a method for the preparation of pyromellitic acid or its anhydride by catalytic vapor phase oxidation of a tetra-C1-C4-alkylbenzene using a catalyst comprising catalytically active material composed of 1 to 20 parts by weight of V2O5, 99 to 80 parts by weight of TiO2 and/or SnO2 and/or ZrO2, and per one hundred parts by weight of V2O5, TiO2 and/or SnO2 and/or ZrO2 0.02 to 10 parts by weight, calculated as P2O5, of a phosphorus compound, 0.01 to 5 parts by weight, calculated as Nb2O5, of a niobium compound, 0 to 1.2 parts by weight, calculated as oxide, of at least one metal selected from the group consisting of potassium, cesium, rubidium and thallium, and 0 to 10 parts by weight, calculated as Sb2O3, of an antimony compound, and an inert carrier supporting said catalytically active material thereon, the improvement in which said catalyst is divided into at least two layers, a layer on the gas inlet side and a layer on the gas outlet side, and (i) the content of potassium, cesium, rubidium or thallium is higher in the catalyst layer on the gas inlet side than in the catalyst layer on the gas outlet side, or (ii) the content of the phosphorus compound is lower in the catalyst layer on the gas inlet side than in the catalyst layer on the gas outlet side, or (iii) the surface area of TiO2 and/or SnO2 and/or ZrO2 is lower in the catalyst layer on the gas inlet side than in the catalyst layer on the gas outlet side.

대표청구항 ▼

In a method for the preparation of pyromellitic acid or its anhydride by catalytic vapor phase oxidation of a tetra-C1-C4-alkylbenzene using a catalyst comprising catalytically active material composed of 1 to 20 parts by weight of V2O5, 99 to 80 parts by weight of TiO2 and/or SnO2 and/or ZrO2 , and

In a method for the preparation of pyromellitic acid or its anhydride by catalytic vapor phase oxidation of a tetra-C1-C4-alkylbenzene using a catalyst comprising catalytically active material composed of 1 to 20 parts by weight of V2O5, 99 to 80 parts by weight of TiO2 and/or SnO2 and/or ZrO2 , and per 100 parts by weight of V2O5, TiO2 and/or SnO2 and/or ZrO2, 0.02 to 10 parts by weight, calculated as P2O5, of phosphorus compound, 0.01 to 5 parts by weight, calculated as Nb2O5, of a niobium compound, 0 to 1.2 parts by weight, calculated as oxide, of at least one metal selected from the group consisting of potassium, cesium, rubidium and thallium, and 0 to 10 parts by weight, calculated as Sb2O3, of an antimony compound, and an inert carrier supporting said catalytically active material thereon, the improvement in which said catalyst is divided into at least two layers, a layer on the gas inlet side and a layer on the gas outlet side, and (i) the content of posassium, cesium, rubidium or thallium is higher in the catalyst layer on the gas inlet side than in the catalyst layer on the gas outlet side, wherein the total amount of potassium, cesium, rubidium and thallium, calculated as K2O, Cs2O, Rb2O and Tl2O3, respectively, is 0.01 to 1.2 parts by weight in the catalyst layer on the gas inlet side and 0 to 0.8 part by weight in the catalyst layer on the gas outlet side, or (ii) the content of the phosphorus compound is lower in the catalyst layer on the gas inlet side than in the catalyst layer on the gas outlet side, wherein the content of the phosphorus compound calculated as P2O5 is 0.02 to 1.2 parts by weight in the catalyst layer on the gas inlet side and 0.04 to 10 parts by weight in the catalyst layer on the gas outlet side, or (iii) the surface area of TiO2 and/or SnO2 and/or ZrO2 is lower in the catalyst layer on the gas inlet side than in the catalyst layer on the gas outlet side, wherein the surface area of TiO2, SnO2 and ZrO2 is 1 to 40 m2/g in the catalyst layer on the gas inlet side and 5 to 100 m2/g in the catalyst layer on the gas outlet side.