Alkylation Process Optimization

Alkylation process has been described in Sec. 1.4. Two optimization problems referred in Chap. 1 as Case A (Maximize Profit and Maximize Octane Number) and Case B (Maximize Profit and Minimize Isobutane Recycle) are solved using NSGA-II and SAEA to illustrate the benefits of SAEA. Variable bounds for optimization problem Case A is the same as those 

For both optimization problems a population of size 40 is evolved over 31 generations. The results of Case A are shown in Fig. 5.7(a). SAEA performed 426 actual evaluations and NSGA-II was run with 440 evaluations. The non-dominated solutions obtained by SAEA have a much better spread as compared to the non-dominated solutions obtained by NSGA-II. 

In order to maximize the use of information from all actual evaluations, the algorithm maintains an external archive that is used to train the RBF model, periodically after every S generations. In order to maintain prediction accuracy, a candidate solution is only approximated using the 

RBF model if at least one solution exists in the archive that is within a distance threshold. This distance threshold plays an important role in the early stages of evolution where more candidate solutions are evaluated using actual computations even during the surrogate phase. Furthermore, a candidate solution is only evaluated using the surrogate model if the MSE of the surrogate on the validation set is below an user defined threshold. 

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Table 1.2 Variables, Bounds and Optimum Values in the Alkylation Process Optimization...

Fig. 5.7 Results obtained by SAEA and NSGA-II for alkylation process optimization, (a) Case A. (b) Case B.

The first chapter of the book provides an introduction to MOO with a realistic application, namely, the alkylation process optimization for two objectives. The second chapter reviews nearly 100 chemical engineering applications of MOO since the year 2000 to mid-2007. The next 5 chapters are on the selected MOO techniques they include (1) review of multi-objective evolutionary algorithms in the context of chemical engineering, (2) multi-objective genetic algorithm and simulated... 

Optimization of a process or catalyst by experimental design such as two-factorial design can lead to significant reduction in time required to achieve the goal. In their excellent work, Mylroie et al. (3) reduced the time required for the optimization of the reductive alkylation process conditions by a factor of 10. Here, we turn our attention to the optimization of the catalyst rather than the process. 

Nitro-attached ketone dianions generally suffer from rapid proton transfer during the alkylation process. However, the reaction conditions have been optimized by using HMPA or TMEDA, which enhanced the reactivity of the dianions toward the alkylating agents19. Examples are shown in Table 10. 

Yu, R. H. Schultze, L. M. RohIoff,J. C. Dudzinski, P.W. Kelly, D. E., Process Optimization in the Synthesis of 9-[2-(Diethylphosphonomethoxy)ethyl]adenine Replacement of Sodium Hydride with Sodium tert-Butoxide as the Base for Oxygen Alkylation. Org. Process Res. Dev. 1999,3, 53. 

As with HF alkylation, an excess of benzene is required. 10. The reaction occurs in the liquid phase and under mild conditions to achieve optimal product quality. The reactor effluent flows directly to the fractionation system, which is similar to that for the HF alkylation process. 

Optimize the alkylation process for two objectives (cases A and/or B) using the e-constraint method and Solver tool in Excel. Are the results comparable to those in Figures 1.5 and 1.6 ... 

Optimize the alkylation process for two objectives (cases A and/or B) using the weighting method. One can use the Solver tool in Excel for SOO. Try different weights to find as many Pareto-optimal solutions as possible. Compare and comment on the solutions obtained with those obtained by the -constraint method (Figures 1.5 and 1.6). Which of the two methods - the weighting and the e-constraint method, is better ... 

Optimize the alkylation process for two objectives (cases A and/or B) using a MOO program (e.g., see Chapters 4 and 5 for two programs provided on the attached CD). Note the computational time taken for each of the two cases. Compare the results obtained with those presented in this chapter. Also, optimize the alkylation process for three objectives maximize profit, maximize octane number and minimize isobutene recycle, using the same program. Compare and discuss the results obtained with those for cases A and B. Does three-objective optimization require comparable or more computational time than two-objective optimization ... 

PetroChina announced a commercial alkene alkylation process (Scheme 2.8) using composite ionic hquids, [(C2)3NH]C1-A1C13 (X(AlCl3) = 0.67) mixed with CuCl to tune the acidity of the ionic hquid for process optimization [131]. In 2006, this process was retrofitted into an existing 65 000 ton per year sulfuric acid alkylation unit in China [132]. The process operates at ambient temperature and moderate pressure, with increased yields and greater process unit capacity (40%... 

Ionic liquid synthesis is usually performed solvent-free by means of the Menschut-kin reaction, i.e. the two reactants (typically abase and an alkyl derivative with leaving group) are mixed and react in the liquid state and yield the liquid product, with almost complete conversion. The challenge for some of these reactions, such as the conversion of methylimidazole and diethyl sulfate (adiabatic temperature rise 173 K) is the high exothermicity under the high reaction rate [25]. This leads to considerable hot-spot formation with sudden temperature jumps of 100 °C and more. This adversely affects the product quality, as is easily visible by a coloring to yellowish or even brown, and places restrictions on safe process optimization. For these reasons, the reactions may be carried out more slowly than kinetically possible to allow for sufEcient heat transfer. 

The transalkylation reaction is essentiaHyisothermal and is reversible. A high ratio of benzene to polyethylbenzene favors the transalkylation reaction to the right and retards the disproportionation reaction to the left. Although alkylation and transalkylation can be carried out in the same reactor, as has been practiced in some processes, higher ethylbenzene yield and purity are achieved with a separate alkylator and transalkylator, operating under different conditions optimized for the respective reactions. 

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