Catalytic converter arrangement with optimized surface for producing phthalic anhydride

Abstract

A catalytic converter arrangement for producing phthalic anhydride by means of a gas phase oxidation of aromatic hydrocarbons, comprising a reactor with a gas inlet side for a reactant gas, a gas outlet side for a product gas, a first catalytic converter layer made of catalytic converter elements, and at least one second catalytic converter layer made of catalytic converter elements. The first catalytic converter layer is arranged on the gas inlet side, and the second catalytic converter layer is arranged downstream of the first catalytic converter layer in the gas flow direction. The catalytic converter elements have an outer layer of an active compound. The invention is characterized in that the active compound content in the first catalytic converter layer and/or in the second catalytic converter layer is below 7 wt. %, based on the total weight of the catalytic converter elements, and the ratio of the total surface of the active compound to the volume of the catalytic converter layer is preferably 10000 cm?1 to 20000 cm?1, in each catalytic converter layer.

Claims

1. A catalyst arrangement for preparing phthalic anhydride by gas-phase oxidation of aromatic hydrocarbons comprising a reactor having a gas inlet end for a feed gas and a gas outlet end for a product gas, a first catalyst zone made up of catalyst bodies, at least one second catalyst zone made up of catalyst bodies, where the first catalyst zone is arranged at the gas inlet end and the second catalyst zone is arranged downstream of the first catalyst zone in the gas flow direction and the catalyst bodies have an outer layer of active composition, wherein the active composition content in the first catalyst zone and/or in the second catalyst zone is less than 7% by weight, based on the total weight of the catalyst bodies, and the ratio of the total surface area of the active composition to the volume of the catalyst zone in the respective catalyst zone is from 10 000 cm.sup.?1 to 20 000 cm.sup.?1.

2. The catalyst arrangement as claimed in claim 1, wherein the active composition content, based on the total weight of the catalyst bodies, of the first and/or second catalyst zone is less than 6% by weight.

3. The catalyst arrangement as claimed in claim 1, wherein the ratio of the total surface area of the active composition to the volume of the catalyst zone in the first catalyst zone differs from that in the second catalyst zone by less than 15%.

4. The catalyst arrangement as claimed in claim 1, wherein the catalyst bodies of the first catalyst zone have a higher active composition loading than the catalyst bodies of the second catalyst zone, in each case based on the mass of the catalyst bodies.

5. The catalyst arrangement as claimed in claim 1, wherein the active composition of the catalyst bodies of the first catalyst zone has a lower BET surface area than the active composition of the catalyst bodies of the second catalyst zone.

6. The catalyst arrangement as claimed in claim 1, wherein the catalyst bodies of the first catalyst zone have an active composition having a lower percentage V.sub.2O.sub.5 content, based on the mass of the active composition, than the catalyst bodies of the second catalyst zone.

7. The catalyst arrangement as claimed in claim 1, wherein the catalyst bodies of the first catalyst zone have an active composition having a lower percentage promoter content, based on the mass on the active composition, than the catalyst bodies of the second catalyst zone.

8. The catalyst arrangement as claimed in claim 1, wherein at least one third catalyst zone is arranged downstream of the second catalyst zone in the gas flow direction and in the third catalyst zone the ratio of the total surface area of the active composition to the volume of the catalyst zone differs from that of the first catalyst zone by less than 15%.

9. The catalyst arrangement as claimed in claim 8, wherein the catalyst bodies of the second catalyst zone have a lower active composition loading than the catalyst bodies of the third catalyst zone, in each case based on the mass of the catalyst bodies.

10. The catalyst arrangement as claimed in either claim 8, wherein the catalyst bodies of the second catalyst zone have an active composition having a higher BET surface area than those of the third catalyst zone.

11. The catalyst arrangement as claimed in claim 8, wherein the catalyst bodies of the second catalyst zone have an active composition having a higher percentage V.sub.2O.sub.5 content, based on the mass of the active composition, than those of the third catalyst zone.

12. The catalyst arrangement as claimed in claim 8, wherein the catalyst bodies of the second catalyst zone have an active composition having a higher promoter content, based on the mass of the active composition, than those of the third catalyst zone.

13. The catalyst arrangement as claimed in claim 1, wherein the length of the first catalyst zone in the gas flow direction is from 5 to 25% of the length of the reactor in the gas flow direction.

14. The catalyst arrangement as claimed in claim 1, wherein the length of the second catalyst zone in the gas flow direction is from 30 to 60% of the length of the reactor in the gas flow direction.

15. A process for preparing phthalic anhydride by gas-phase oxidation of aromatic hydrocarbons, comprising the step of passing a feed gas containing an aromatic hydrocarbon through a catalyst arrangement as claimed in claim 1.

Description

EXAMPLES

(1) Catalytic measurements were carried out on four-zone catalyst arrangements made up of catalyst bodies. To synthesize the catalyst bodies, two different types of steatite rings designated as ring 8?6?5 and ring 6?5?4 were used as shaped bodies. The nomenclature of the geometric dimensions of the rings corresponds to external diameter (Da) [mm]?height (H) [mm]?internal diameter (Di) [mm]. The geometric dimensions of the uncoated shaped bodies can be seen in table 2. The uncoated shaped bodies were introduced into a coating apparatus and coated homogeneously with the active composition. During the coating operation, an aqueous suspension of the active components and an organic binder is sprayed through a plurality of nozzles onto the heated, fluidized support until an active composition layer of about 50-150 ?m has been formed. Table 3 gives an overview of the catalyst bodies used and the respective chemical constitution of the active composition.

(2) To form the catalyst zones, the respective catalyst bodies were introduced into a salt bath-cooled tube having an internal diameter of 25 mm and a length of 4 m. A 3 mm thermocoupled sheath having an installed withdrawable element for measuring the temperature was arranged centrally in the tube.

(3) To carry out the catalytic measurement, from about 3.7 to 4.0 standard m.sup.3 (standard cubic meters) per hour of air having a loading of from 30 to 100 g of ortho-xylene/standard m.sup.3 of air (purity of ortho-xylene >98%) were passed at a total pressure of about 1500 mbar from the top downward through the tube. The measurements were in each case carried out at a loading of from about 40 to 100 g of ortho-xylene/standard m.sup.3 of air and a salt bath temperature in the range from 350 to 390? C.

(4) The phthalic anhydride yield was calculated using eq. 8:

(5) $\begin{array}{cc}{Y}_{\mathrm{PA}}=\left[139.52-\left(800*\frac{A+B}{E}\right)+\left(100-F\right)-\left(1.25*H\right)-\left(1.1*G\right)\right]& \mathrm{Eq}.8\end{array}$ A=CO.sub.2 in the product stream [% by volume] B=CO in the product stream [% by volume] H=maleic anhydride in the product stream [% by weight] E=ortho-xylene loading in the feed stream [g/standard m.sup.3/h/tube] F=ortho-xylene purity of the ortho-xylene used [% by weight] G=ortho-xylene breakthrough based on the total ortho-xylene used [% by weight] Y.sub.PA=yield of phthalic anhydride (PAn) based on the total weight of the ortho-xylene used [% by weight]

(6) As can be seen from eq. 8, the phthalic anhydride yield is directly dependent on the formation of the three most important by-products CO, CO.sub.2 and maleic anhydride.

(7) TABLE-US-00002 TABLE 2 Geometric dimensions and properties of the uncoated shaped bodies Ring 8 ? 6 ? 5 Ring 6 ? 5 ? 4 External diameter ? height 0.48 0.30 [cm.sup.2] Volume [cm.sup.3] 0.184 0.079 Surface area [cm.sup.2] 3.063 1.885 Surface area/volume [cm.sup.?1] 16.7 24.0 Volume/surface area [cm] 0.060 0.042 Apparent density [g/cm.sup.3] 2.61 2.61

(8) TABLE-US-00003 TABLE 3 Catalyst bodies used Proportion Proportion of active Ring shape of binder composition TiO.sub.2 V.sub.2O.sub.5 Promoters (Da ? H ? Di).sup.1 [% by [% by BET [% by [% by [% by Designation [mm] weight].sup.3 weight].sup.2 [m.sup.2/g] weight].sup.3 weight].sup.3 weight].sup.4 Comparative test 1 A0 8 ? 6 ? 5 2.3 8.5 18 87.4 7.5 5.1 A1 8 ? 6 ? 5 2.3 8.5 18 87.4 7.5 5.1 A2 8 ? 6 ? 5 2.3 8.0 18 89.0 7.5 3.5 A3 8 ? 6 ? 5 2.3 8.0 27 90.6 9.0 0.4 Comparative test 2 B0 8 ? 6 ? 5 2.4 8.3 19 87.4 7.5 5.1 B1 8 ? 6 ? 5 2.4 8.6 18 87.3 7.6 5.1 B2.1 8 ? 6 ? 5 2.4 8.0 18 89.1 7.4 3.5 B3.1 8 ? 6 ? 5 2.2 7.9 26 90.6 9.1 0.4 Comparative test 3 B0 8 ? 6 ? 5 2.4 8.3 19 87.4 7.5 5.1 C1 8 ? 6 ? 5 1.3 3.1 17 88.0 7.7 4.3 B2.1 8 ? 6 ? 5 2.4 8.0 18 89.1 7.4 3.5 B3.2 8 ? 6 ? 5 2.4 7.9 25 90.2 9.4 0.4 Test 1 according to the invention B0 8 ? 6 ? 5 2.4 8.3 19 87.4 7.5 5.1 D1 8 ? 6 ? 5 2.3 5.2 27 83.6 10.7 5.7 B2.2 8 ? 6 ? 5 2.4 8.0 18 88.0 7.4 3.5 B3.1 8 ? 6 ? 5 2.2 7.9 26 90.6 9.1 0.4 Test 2 according to the invention B0 8 ? 6 ? 5 2.4 8.3 19 87.4 7.5 5.1 E1 6 ? 5 ? 4 2.2 5.3 24 83.7 10.7 5.6 B2.1 8 ? 6 ? 5 2.4 8.0 18 89.1 7.4 3.5 B3.2 8 ? 6 ? 5 2.4 7.9 25 90.2 9.4 0.4 .sup.1Da = external diameter, H = height, Di = internal diameter .sup.2based on the total weight of the catalyst body .sup.3based on the total weight of the active composition .sup.4predominantly Sb.sub.2O.sub.3 with smaller proportions of Nb.sub.2O.sub.5, P and Cs

(9) TABLE-US-00004 TABLE 4 Fill parameters for the comparative test 1 Surface area/volume Ring Fill height Bulk Apparent (of inert shape Catalyst L.sub.x density density body) (Da ? H ? Di) SA.sub.A/V.sub.x zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [cm.sup.?1] [mm] [cm.sup.?1] 1 A0 40.9 0.92 2.623 16.67 8 ? 6 ? 5 14 026 2 A1 160.0 0.91 2.664 16.67 8 ? 6 ? 5 13 947 3 A2 60.9 0.91 2.622 16.67 8 ? 6 ? 5 13 104 4 A3 59.5 0.91 2.663 16.67 8 ? 6 ? 5 19 667

(10) TABLE-US-00005 TABLE 5 Fill parameters for the comparative test 2 Surface area/volume Ring Fill height Bulk Apparent (of inert shape Catalyst L.sub.x density density body) (Da ? H ? Di) SA.sub.A/V.sub.x zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [cm.sup.?1] [mm] [cm.sup.?1] 1 B0 40.0 0.89 2.624 16.67 8 ? 6 ? 5 14 089 2 B1 135.3 0.91 2.610 16.67 8 ? 6 ? 5 14 065 3 B2.1 60.5 0.90 2.619 16.67 8 ? 6 ? 5 12 898 4 B3.1 64.9 0.92 2.643 16.67 8 ? 6 ? 5 18 884

(11) TABLE-US-00006 TABLE 6 Fill parameters for the comparative test 3 Surface area/volume Ring Fill height Bulk Apparent (of inert shape Catalyst L.sub.x density density body) (Da ? H ? Di) SA.sub.A/V.sub.x zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [cm.sup.?1] [mm] [cm.sup.?1] 1 B0 40.3 0.89 2.624 16.67 8 ? 6 ? 5 14 089 2 C1 155.0 0.90 2.610 16.67 8 ? 6 ? 5 4844 3 B2.1 60.5 0.90 2.619 16.67 8 ? 6 ? 5 12 898 4 B3.2 65.0 0.92 2.620 16.67 8 ? 6 ? 5 18 415

(12) TABLE-US-00007 TABLE 7 Fill parameters for test 1 according to the invention Surface area/volume Ring Fill height Bulk Apparent (of inert shape Catalyst L.sub.x density density body) (Da ? H ? Di) SA.sub.A/V.sub.x zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [cm.sup.?1] [mm] [cm.sup.?1] 1 B0 41.2 0.89 2.624 16.67 8 ? 6 ? 5 14 089 2 D1 154.5 0.90 2.600 16.67 8 ? 6 ? 5 12 492 3 B2.2 60.7 0.88 2.573 16.67 8 ? 6 ? 5 12 692 4 B3.1 65.4 0.92 2.643 16.67 8 ? 6 ? 5 18 884

(13) TABLE-US-00008 TABLE 8 Fill parameters for test 2 according to the invention Surface area/volume Ring Fill height Bulk Apparent (of inert shape Catalyst L.sub.x density density body) (Da ? H ? Di) SA.sub.A/V.sub.x zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [cm.sup.?1] [mm] [cm.sup.?1] 1 B0 39.7 0.89 2.624 16.7 8 ? 6 ? 5 14 089 2 E1 155.3 0.96 2.693 24.0 6 ? 5 ? 4 12 350 3 B2.1 60.9 0.90 2.619 16.7 8 ? 6 ? 5 12 898 4 B3.2 64.3 0.92 2.620 16.7 8 ? 6 ? 5 18 415

(14) TABLE-US-00009 TABLE 9 Catalyst performance in the comparative test 1 Loading with ortho- Yield of (CO + CO.sub.2)/ Volume flow ortho-xylene CO CO.sub.2 MAn Xylene PAn Loading TOS of air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by [Vol.-%/g/ [h] [Nm.sup.3] tube] [? C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 Nm.sup.3/h/tube] 178.6 4.0 33.7 379 0.337 0.781 5.0 0.01 108.7 0.0332 203.4 4.0 35.7 378 0.357 0.827 5.1 0.01 108.7 0.0332 705.1 4.0 46.3 371 0.465 1.115 4.9 0.02 108.0 0.0341 728.7 4.0 48.3 370 0.487 1.193 5.0 0.02 107.5 0.0348 752.2 4.0 48.3 370 0.490 1.137 5.0 0.02 108.3 0.0337 2821.4 4.0 79.9 359 0.749 1.785 4.5 0.03 110.5 0.0317 2847.0 4.0 79.9 360 0.752 1.798 4.5 0.03 110.3 0.0319 2867.2 4.0 81.4 360 0.757 1.810 4.5 0.03 110.7 0.0315

(15) TABLE-US-00010 TABLE 10 Catalyst performance in the comparative test 2 Loading with ortho- Yield of (CO + CO.sub.2)/ Volume flow ortho-xylene CO CO.sub.2 MAn Xylene PAn Loading TOS of air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by [Vol.-%/g/ [h] [Nm.sup.3] tube] [? C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 Nm.sup.3/h/tube] 254.3 3.7 73.1 368 0.758 1.712 4.9 0.02 108.4 0.0338 278.4 3.7 73.1 368 0.732 1.671 4.7 0.02 109.3 0.0328 302.5 3.7 73.1 368 0.726 1.670 4.7 0.02 109.5 0.0328 538.1 3.7 82.0 364 0.806 1.866 4.7 0.02 109.6 0.0326 562.1 3.7 83.9 363 0.820 1.958 4.7 0.03 109.2 0.0331 761.3 3.7 90.9 356 0.848 2.048 4.3 0.02 110.6 0.0319 785.3 3.7 90.9 356 0.848 2.056 4.3 0.03 110.6 0.0320 809.3 3.7 90.9 356 0.838 2.038 4.2 0.03 110.9 0.0316

(16) TABLE-US-00011 TABLE 11 Catalyst performance in the comparative test 3 Loading with ortho- Yield of (CO + CO.sub.2)/ Volume ortho-xylene CO CO.sub.2 MAn Xylene PAn Loading TOS flow of air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by [Vol.-%/g/ [h] [Nm.sup.3] tube] [? C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 Nm.sup.3/h/tube] 487.3 4.0 41.6 380 0.394 0.908 3.8 0.01 111.8 0.0313 580.4 4.0 52.1 372 0.464 1.147 3.6 0.02 112.3 0.0309 620.0 4.0 54.1 371 0.490 1.160 4.2 0.02 111.9 0.0305 938.0 4.0 54.1 364 0.509 1.199 4.0 0.02 111.3 0.0315 962.0 4.0 54.1 364 0.504 1.180 4.0 0.02 111.7 0.0311 1051.9 4.0 50.6 361 0.467 1.092 3.9 0.03 112.0 0.0308 1062.0 4.0 50.6 360 0.469 1.097 4.0 0.03 111.7 0.0309

(17) TABLE-US-00012 TABLE 12 Catalyst performance in test 1 according to the invention Loading with ortho- Yield of (CO + CO.sub.2)/ Volume flow ortho-xylene CO CO.sub.2 MAn Xylene PAn Loading TOS of air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by [Vol.-%/g/ [h] [Mm.sup.3] tube] [? C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 Nm.sup.3/h/tube] 647.4 4.0 68.0 378 0.604 1.390 4.1 0.02 112.9 0.0293 703.2 4.0 69.9 375 0.613 1.420 4.2 0.03 113.0 0.0291 742.4 4.0 71.0 373 0.599 1.393 4.1 0.02 113.9 0.0280 766.4 4.0 71.0 373 0.610 1.422 4.1 0.02 113.5 0.0286 799.1 4.0 72.1 372 0.573 1.342 4.2 0.03 115.0 0.0265 823.0 4.0 74.0 371 0.602 1.444 4.2 0.03 114.2 0.0276 847.6 4.0 76.0 370 0.634 1.517 4.2 0.03 113.6 0.0283 878.0 4.0 77.9 369 0.640 1.525 4.2 0.03 114.0 0.0278 903.0 4.0 80.1 368 0.649 1.483 4.2 0.02 115.0 0.0266 991.1 4.0 80.9 365 0.645 1.537 3.9 0.03 115.0 0.0270 1037.5 4.0 80.9 362 0.625 1.493 3.9 0.04 115.6 0.0262 1057.3 4.0 80.9 361 0.635 1.580 3.8 0.05 114.8 0.0274 1080.1 4.0 81.5 360 0.636 1.527 3.7 0.02 115.6 0.0266 1102.8 4.0 81.5 360 0.628 1.514 3.7 0.02 115.8 0.0263 1186.0 4.0 76.2 360 0.000 0.000 3.7 0.02 136.9 0.0000 1212.0 4.0 81.2 360 0.598 1.433 3.8 0.02 116.7 0.0250 1224.7 4.0 81.2 360 0.601 1.458 3.8 0.04 116.4 0.0254 1247.5 4.0 81.2 360 0.602 1.447 3.8 0.04 116.6 0.0252 1270.3 4.0 81.2 360 0.602 1.447 3.8 0.04 116.6 0.0252 1354.1 4.0 81.2 354 0.585 1.428 3.5 0.12 117.2 0.0248

(18) TABLE-US-00013 TABLE 13 Catalyst performance in test 2 according to the invention Loading with ortho- Yield of (CO + CO.sub.2)/ Volume flow ortho-xylene CO CO.sub.2 MAn Xylene PAn Loading TOS of air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by [Vol.-%/g/ [n] [Nm.sup.3] tube] [? C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 Nm.sup.3/h/tube] 156.2 4.0 43.0 387 0.463 1.019 4.6 0.01 108.2 0.0345 180.4 4.0 47.0 384 0.508 1.115 4.7 0.01 108.0 0.0345 204.3 4.0 51.0 381 0.560 1.230 4.8 0.01 107.5 0.0351 229.5 4.0 55.9 377 0.595 1.317 4.7 0.01 108.3 0.0342 250.5 4.0 59.9 373 0.581 1.318 4.3 0.02 110.7 0.0317 274.5 4.0 59.9 373 0.587 1.332 4.3 0.02 110.5 0.0320 298.5 4.0 59.9 373 0.585 1.335 4.3 0.02 110.5 0.0321 348.5 4.0 66.1 367 0.578 1.408 3.9 0.03 112.6 0.0300 1260.8 4.0 78.0 357 0.636 1.585 3.3 0.08 114.5 0.0285 1284.9 4.0 78.0 357 0.633 1.539 3.2 0.07 115.2 0.0279 1309.0 4.0 78.0 357 0.623 1.511 3.2 0.07 115.6 0.0274 1335.1 4.0 80.9 357 0.636 1.587 3.2 0.09 115.5 0.0275 1383.6 4.0 84.9 356 0.676 1.650 3.5 0.10 115.2 0.0274 1406.4 4.0 84.9 355 0.681 1.663 3.5 0.09 115.0 0.0276 1551.6 4.0 84.9 355 0.677 1.731 3.5 0.13 114.4 0.0284 1578.4 4.0 84.9 355 0.648 1.747 3.5 0.12 114.5 0.0282 1621.3 4.0 84.9 355 0.674 1.717 3.5 0.13 114.5 0.0282 .sup.1based on the total volume of the product stream .sup.2based on the total weight of the product stream .sup.3based on the total weight of the ortho-xylene used