Catalyst Arrangement With Optimized Void Fraction For The Production Of Phthalic Acid Anhydride

Abstract

The invention relates to a catalyst arrangement for preparing phthalic anhydride by gas-phase oxidation of aromatic hydrocarbons, which comprises a reactor having a gas inlet end for a feed gas and a gas outlet end for a product gas and also a first catalyst zone made up of catalyst bodies and 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 length of the first catalyst zone in the gas flow direction is less than the length of the second catalyst zone in the gas flow direction, characterized in that the first catalyst zone has a higher gap content compared to the second catalyst zone.

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 and also a first catalyst zone made up of catalyst bodies and 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 length of the first catalyst zone in the gas flow direction is less than the length of the second catalyst zone in the gas flow direction, wherein the first catalyst zone has a higher gap content compared to the second catalyst zone.

2. The catalyst arrangement as claimed in claim 1, wherein the higher gap content is due to the catalyst bodies of the first catalyst zone differing in terms of one or more geometric dimension(s), their geometric shape from the catalyst bodies of the second catalyst zone or both.

3. The catalyst arrangement as claimed in claim 2, wherein the catalyst bodies of the first catalyst zone and the catalyst bodies of the second catalyst zone are ring-shaped and the catalyst bodies of the second catalyst zone have smaller geometric dimensions than those of the first catalyst zone.

4. The catalyst arrangement as claimed in claim 1, wherein the gap content of the first catalyst zone is at least 0.6% higher than the gap content of the second catalyst zone.

5. The catalyst arrangement as claimed in claim 1, wherein the gap content of the first catalyst zone is at least 1.5% higher than the gap content of the second catalyst zone.

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

7. 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.

8. 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.

9. 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.

10. The catalyst arrangement as claimed in claim 1, wherein a third catalyst zone which has a higher gap content compared to the second catalyst zone is arranged downstream of the second catalyst zone in the gas flow direction.

11. The catalyst arrangement as claimed in claim 10, wherein the catalyst bodies of the second catalyst zone have, based on the mass of the catalyst bodies, a lower active composition loading than the catalyst bodies of the third catalyst zone.

12. The catalyst arrangement as claimed in claim 10, 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.

13. The catalyst arrangement as claimed in claim 10, 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.

14. The catalyst arrangement as claimed in claim 10, 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.

15. 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.

16. The catalyst arrangement as claimed in claim 10, 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.

17. 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.

18. A phthalic anhydride obtained by a catalyst arrangement as claimed in claim 1.

Description

EXAMPLES

[0067] Catalytic measurements were carried out on four-zone catalyst arrangements made up of catalyst bodies. To synthesize the catalyst bodies, three different types of steatite rings designated as ring 8×6×5, ring 7×7×4 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.

[0068] 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 μm has been formed. Table 3 gives an overview of the catalyst bodies used and the respective chemical constitution of the active composition.

[0069] The gap content GC of the catalyst zones was calculated using eq. 6.

[00005]$\begin{array}{cc}\mathrm{GC}=\left[1-\frac{{\rho }_{\mathrm{bulk}}}{{\rho }_{\mathrm{cat}}}\right]*100.Math.\%& \mathrm{Eq}..Math.6\end{array}$ [0070] ρ.sub.bulk=bulk density of the catalyst bodies [g/cm.sup.3] [0071] ρ.sub.cat=apparent density of the catalyst bodies [g/cm.sup.3] (about 2.5 g/cm.sup.3) [0072] GC=gap content [%]

[0073] To determine the bulk density, a tube having a diameter close to the internal diameter of the reactor tube (internal diameter 2.7 cm) was filled with the appropriate catalyst, in each case to a fill height of 100.0 cm. To ensure uniform filling, the catalyst bodies were introduced individually into the tube. Uniform filling could be visually monitored since a transparent plastic tube was used. After successful filling, the tube was completely emptied and the mass of the catalyst bodies which had been introduced was determined by means of a balance. The bulk density of the catalyst bodies was calculated therefrom according to eq. 7 below:

[00006]$\begin{array}{cc}{\rho }_{\mathrm{bulk}}=\frac{m_{\mathrm{cat}}}{\pi .Math.\frac{d^2}{4}.Math.h}& \mathrm{Eq}..Math.7\end{array}$

ρ.sub.bulk: bulk density of catalyst bodies [g/cm.sup.3] [0074] m.sub.cat: mass of catalyst bodies introduced [g] [0075] d: internal diameter of tube [cm]=2.7 cm [0076] h: fill height of tube [cm]=100.0 cm

[0077] The bulk density was determined three times for each type of catalyst body in order to calculate therefrom the arithmetic mean used in the further text.

[0078] The apparent density of the catalyst bodies corresponds to the ratio of the total mass of the catalyst body (i.e. including the mass of the steatite ring and the applied active composition) to the total volume of the shaped body taking into account the outer surface. The total volume of the shaped body corresponds to the volume of the shaped body including the volume of any pores present. The apparent density was determined by means of a mercury porosimeter; owing to the fact that mercury does not wet the walls of a solid sample, pressure is required to intrude into any pores in the sample. This enables the total volume to be determined, since the system of sample+mercury is under reduced pressure and mercury therefore cannot penetrate into the interior of the pores and so then covers exclusively the external surface.

[0079] The apparent density of the various catalyst bodies in table 3 varies by values of <0.05 g/cm.sup.3.

[0080] 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.

[0081] 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.

[0082] The phthalic anhydride yield was calculated using eq. 8:

[00007]$\begin{array}{cc}{Y}_{\mathrm{PA}}=\left[139.52-\left(800*\frac{A+B}{E}\right)+\left(100-F\right)-\left(1.25*H\right)-\left(1.1*G\right)\right]& \mathrm{Eq}..Math.8\end{array}$ [0083] A=CO.sub.2 in the product stream [% by volume] [0084] B=CO in the product stream [% by volume] [0085] H=maleic anhydride in the product stream [% by weight] [0086] E=ortho-xylene loading in the feed stream [g/standard m.sup.3/h/tube] [0087] F=ortho-xylene purity of the ortho-xylene used [% by weight] [0088] G=ortho-xylene breakthrough based on the total ortho-xylene used [% by weight] [0089] Y.sub.PA=yield of phthalic anhydride (PAn) based on the total weight of the ortho-xylene used [% by weight]

[0090] 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.

TABLE-US-00002 TABLE 2 Geometric dimensions and properties of the uncoated shaped bodies Ring 8 × 6 × 5 Ring 7 × 7 × 4 Ring 6 × 5 × 4 External diameter × height 0.48 0.28 0.30 [cm.sup.2] Volume [cm.sup.3] 0.184 0.104 0.079 Surface area [cm.sup.2] 3.063 1.901 1.885 Surface area/volume [cm.sup.−1] 16.7 18.3 24.0 Volume/surface area [cm] 0.060 0.055 0.042 Apparent density [g/cm.sup.3] 2.61 2.61 2.61

TABLE-US-00003 TABLE 3 Catalyst bodies used Proportion of active Proportion of composition TiO.sub.2 V.sub.2O.sub.5 Promoters Ring shape binder [% by BET [% by [% by [% by Designation (Da × H × Di).sup.1 [mm] [% by 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 Test 1 according to the invention B1 8 × 6 × 5 2.4 8.6 18 87.3 7.6 5.1 D1 6 × 5 × 4 2.3 5.3 19 84.7 7.2 8.1 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 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 Test 3 according to the invention B0 8 × 6 × 5 2.4 8.3 19 87.4 7.5 5.1 F1 7 × 7 × 4 2.2 5.3 27 83.0 10.6 5.6 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 .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

TABLE-US-00004 TABLE 4 Fill parameters for the comparative test 1 Fill Ap- Gap height Bulk parent content, Ring shape Catalyst L.sub.x density density GC (Da × H × Di) zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [%] [mm] 1 A0 40.9 0.92 2.623 65.1 8 × 6 × 5 2 A1 160.0 0.91 2.664 65.8 8 × 6 × 5 3 A2 60.9 0.91 2.622 65.3 8 × 6 × 5 4 A3 59.5 0.91 2.663 65.8 8 × 6 × 5

TABLE-US-00005 TABLE 5 Fill parameters for the comparative test 2 Fill Ap- Gap height Bulk parent content, Ring shape Catalyst L.sub.x density density GC (Da × H × Di) zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [%] [mm] 1 B0 40.0 0.89 2.624 66.0 8 × 6 × 5 2 B1 135.3 0.91 2.610 65.2 8 × 6 × 5 3 B2.1 60.5 0.90 2.619 65.8 8 × 6 × 5 4 B3.1 64.9 0.92 2.643 65.2 8 × 6 × 5

TABLE-US-00006 TABLE 6 Fill parameters for test 1 according to the invention Fill Ap- Gap height Bulk parent content, Ring shape Catalyst L.sub.x density density GC (Da × H × Di) zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [%] [mm] 1 B1 39.8 0.84 2.610 65.2 8 × 6 × 5 2 D1 154.5 0.91 2.631 62.6 6 × 5 × 4 3 B2.1 60.5 0.84 2.619 65.8 8 × 6 × 5 4 B3.2 64.8 0.84 2.620 65.0 8 × 6 × 5

TABLE-US-00007 TABLE 7 Fill parameters for test 2 according to the invention Fill Ap- Gap height Bulk parent content, Ring shape Catalyst L.sub.x density density GC (Da × H × Di) zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [%] [mm] 1 B0 39.7 0.89 2.624 66.0 8 × 6 × 5 2 E1 155.3 0.96 2.693 64.5 6 × 5 × 4 3 B2.1 60.9 0.90 2.619 65.8 8 × 6 × 5 4 B3.2 64.3 0.92 2.620 65.0 8 × 6 × 5

TABLE-US-00008 TABLE 8 Fill parameters for test 3 according to the invention Fill Ap- Gap height Bulk parent content, Ring shape Catalyst L.sub.x density density GC (Da × H × Di) zone x Catalyst [cm] [g/cm.sup.3] [g/cm.sup.3] [%] [mm] 1 B0 41.0 0.89 2.62 66.0 8 × 6 × 5 2 F1 155.0 0.93 2.60 64.1 7 × 7 × 4 3 B2.2 60.5 0.88 2.57 65.7 8 × 6 × 5 4 B3.1 64.5 0.92 2.64 65.2 8 × 6 × 5

TABLE-US-00009 TABLE 9 Catalyst performance in the comparative test 1 Loading with ortho- ortho- Yield of (CO + CO.sub.2)/ Volume flow xylene CO CO.sub.2 MAn Xylene PAn Loading TOS of air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by [Vol.- [h] [Nm.sup.3] tube] [° C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 %/g/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

TABLE-US-00010 TABLE 10 Catalyst performance in the comparative test 2 Loading with ortho- ortho- Yield of Volume flow xylene CO CO.sub.2 MAn Xylene PAn (CO + CO.sub.2)/ TOS of air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by Loading [h] [Nm.sup.3] tube] [° C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 [Vol.-%/g/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 .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 xylene used

TABLE-US-00011 TABLE 11 Catalyst performance in test 1 according to the invention Loading with ortho- ortho- Yield of Volume flow of xylene CO CO.sub.2 MAn Xylene PAn (CO + CO.sub.2)/ TOS air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by Loading [h] [Nm.sup.3] tube] [° C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 [Vol.-%/g/Nm.sup.3/h/tube] 318.6 4.0 38.9 382 0.390 0.830 4.1 0.01 111.3 0.0313 342.5 4.0 39.9 380 0.398 0.854 4.0 0.01 111.5 0.0313 532.7 4.0 45.9 372 0.436 0.958 3.7 0.01 112.6 0.0304 557.9 4.0 48.1 370 0.447 0.989 3.7 0.01 113.1 0.0299 579.6 4.0 50.1 369 0.458 1.033 3.6 0.02 113.2 0.0298 680.8 4.0 54.0 365 0.479 1.089 3.6 0.02 113.8 0.0290 698.9 4.0 56.0 364 0.494 1.136 3.6 0.02 113.8 0.0291 916.5 4.0 63.9 362 0.530 1.321 3.6 0.03 113.8 0.0289 .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 xylene used

TABLE-US-00012 TABLE 12 Catalyst performance in test 2 according to the invention Loading with ortho- ortho- Volume flow xylene CO CO.sub.2 MAn Xylene Yield of PAn (CO + CO.sub.2)/ TOS of air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by Loading [h] [Nm.sup.3] tube] [° C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 [Vol.-%/g/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

TABLE-US-00013 TABLE 13 Catalyst performance in test 3 according to the invention Loading with ortho- ortho- Volume flow xylene CO CO.sub.2 MAn Xylene Yield of PAn (CO + CO.sub.2)/ TOS of air [g/Nm.sup.3/h/ SBT [% by [% by [% by [% by [% by Loading [h] [Nm.sup.3] tube] [° C.] volume].sup.1 volume].sup.1 weight].sup.2 weight].sup.2 weight].sup.3 [Vol.-%/g/Nm.sup.3/h/tube] 164.3 4.0 40.6 386 0.465 0.900 4.5 0.01 109.0 0.0336 184.2 4.0 43.2 382 0.480 0.944 4.5 0.01 109.5 0.0330 207.6 4.0 46.2 378 0.511 1.072 4.3 0.02 108.7 0.0343 231.6 4.0 46.2 378 0.506 1.060 4.3 0.02 109.0 0.0339 255.6 4.0 46.2 378 0.506 1.070 4.3 0.00 108.8 0.0341 279.6 4.0 51.2 374 0.559 1.197 4.3 0.02 108.8 0.0343 309.8 4.0 55.3 370 0.567 1.229 4.2 0.03 110.3 0.0325 333.8 4.0 61.3 367 0.637 1.417 4.1 0.03 109.6 0.0335 351.5 4.0 65.4 365 0.657 1.470 4.2 0.04 110.2 0.0325 387.6 4.0 71.4 363 0.705 1.608 4.1 0.03 110.4 0.0324 404.3 4.0 71.4 363 0.684 1.559 3.9 0.03 111.5 0.0314 428.3 4.0 71.4 363 0.671 1.534 3.9 0.03 111.9 0.0309 452.3 4.0 79.5 362 0.793 1.839 4.2 0.04 109.8 0.0331 474.4 4.0 82.5 362 0.814 1.902 4.2 0.04 109.9 0.0329 498.4 3.9 87.9 361 0.870 2.053 4.2 0.05 109.6 0.0333 522.4 3.9 87.9 360 0.855 2.032 4.1 0.05 110.0 0.0329 546.3 3.9 89.9 359 0.849 2.028 4.0 0.07 110.8 0.0320 570.4 3.9 89.9 359 0.846 2.039 4.0 0.07 110.8 0.0321 618.4 3.9 93.9 358 0.891 2.171 4.0 0.11 110.3 0.0326 based 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 xylene used