Separation Process Principles- 2n - Seader & Henley - Solutions Manual

For the formation of mtbe from isobutene and methanol

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Unformatted text preview: cled. Exercise 11.21 (continued) Analysis: (continued) Exercise 11.22 Subject: Reactive distillation of isobutene (IB) with methanol (M), in the presence of n-butene (NB) to produce MTBE. Effect of the feed stage location for methanol. Given: Mixed butenes feed of 195.44 mol/s of IB and 353.56 mol/s of NB entering stage 11 as a vapor at 350 K and 11 bar. Methanol feed of 215.5 mol/s at 320 K and 11 bar. Column operates at 11 atm and has 15 equilibrium stages, with a total condenser and partial reboiler. Reflux ratio = 7 and bottoms flow rate is set at 197 mol/s. Catalyst for the reaction is provided in the amount of 204.1 kg/stage only at stages 4 through 11. Kinetic data are given in Example 11.9. Use UNIQUAC method for liquid-phase activity coefficients, with the binary interaction parameters in Example 11.9, and RK EOS for vapor-phase fugacities. Find: Distillate and bottoms products as a function of feed stage location for methanol. Analysis: Chemcad can be used, but here, the calculations were made with Aspen Plus version 10.1, but convergence was not easy to achieve. The initial case was run with the methanol fed to stage 7 from the top, counting the total condenser as the first stage. The input data, which are given on the next two pages, differ slightly from the listing for Example 11.9. With this feed stage, the overall material balance in mol/s are: Component Feed 1 Feed 2 Distillate Bottoms Methanol 215.50 0.00 31.26 0.13 Isobutene 0.00 195.44 8.25 3.08 n-butene 0.00 353.56 343.69 9.87 MTBE 0.00 0.00 0.19 183.92 Total: 215.50 549.00 383.39 197.00 To obtain the results for the other methanol feed-stage locations, the following procedure was used. Starting from Stage 7 and using the previous results to start each new run, results were obtained for methanol feed stages of 8, 9, 10, and 11. Working backward from Stage 7, results were obtained for methanol feed stages of 6 and 5. Then, results were obtained, starting from Stage 2, for methanol feed stages of 2, 3, and 4, where the input on the next two pages were modified under BLOCK B1 RADFRAC to: X-EST 17 MEOH 0.01 / 17 MTBE 0.95 Y-EST 17 MEOH 0.02 / 17 MTBE 0.875 To obtain results for methanol feed stages 12 to 16, the input data on the next two pages were first modified under BLOCK B1 RADFRAC to: X-EST 17 MEOH 0.90 / 17 MTBE 0.00 Y-EST 17 MEOH 0.90 / 17 MTBE 0.00 This gave results for methanol feed stages of 12, 13, 14, 15, and 16; and 12 back to 11. The values for % conversion of isobutene were as follows, and compare well with Fig. 11.39. Stage 2 3 4 5 6 7 8 9 10 11 11 12 13 14 15 16 %Conv 89 91 92 93 94 94 95 95 96 96 0.7 0.7 0.6 0.6 0.6 0.6 Analysis: (continued) Exercise 11.22 (continued) Analysis: (continued) Exercise 11.22 (continued) Exercise 11.23 Subject: Reactive distillation of isobutene (IB) with methanol (M), in the presence of n-butene (NB) to produce MTBE. Use of activities instead of mole fractions in the kinetic equations. Given: Mixed butenes feed of 195.44 mol/s of IB and 353.56 mol/s of NB entering stage 11 as a vapor at 350...
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