Attainable product

Even though the simple distillation process has no practical use as a method for separating mixtures, simple distillation residue curve maps have extremely usehil appHcations. These maps can be used to test the consistency of experimental azeotropic data (16,17,19) to predict the order and content of the cuts in batch distillation (20—22) and, in continuous distillation, to determine whether a given mixture is separable by distillation, identify feasible entrainers/solvents, predict the attainable product compositions, quaHtatively predict the composition profile shape, and synthesize the corresponding distillation sequences (16,23—30). By identifying the limited separations achievable by distillation, residue curve maps are also usehil in synthesizing separation sequences combining distillation with other methods. 

The maximum attainable production was sought that did not cause thermal runaway. By gradually increasing the temperature of the water, boiling under pressure in the reactor jacket, the condition was found for the incipient onset of thermal instability. Runaway set in at 485.2 to 485.5 K for the 12 m reactor and at 435.0 to 435.5 K for the shorter, 1.2 m reactor. The smaller reactor reached its maximum operation limit at 50 K lower than the larger reactor. The large reactor produced 33 times more methanol, instead of the 10 times more expected from the sizes. This... 

In the Riser Simulator, an impeller rotating at very high speed on the top of the reaction chamber keeps the catalyst fluidized between two metal porous plates, inducing the internal circulation of the reacting mixture in an upward direction through the chamber. When the reactor is at the desired experimental conditions, the reactant is fed through an injection port, and immediately after the set reaction time is attained, products are evacuated and analyzed by gas chromatography. Of particular importance to the experiments performed was the ability to extend reaction... 

Conditions bulk polymerization in 1 liter of liquid propylene at 70°C, Al/Zr molar ratio = 15000. The results illustrate the broad range of attainable product properties (155). 

As demonstrated by means of residue curve analysis, selective mass transfer through a membrane has a significant effect on the location of the singular points of a batch reactive separation process. The singular points are shifted, and thereby the topology of the residue curve maps can change dramatically. Depending on the structure of the matrix of effective membrane mass transfer coefficients, the attainable product compositions are shifted to a desired or to an undesired direction. 

For example, the separations d,h, and d2h2 are sloppy splits with different amounts of A in the distillate, and accordingly with different recoveries. The separation of pure A at the top is represented by the split d h, which corresponds to a direct sequence . Accordingly, the separation of B/C in a second column is represented by the edge BC, on which h is the feed. Similarly, the first split in an indirect sequence , in which C is separated in bottoms and A/B at the top, is shown by the segment d"b". The locus of all splits between the above limit cases allows the regions of attainable products to be defined. 

Detailed design of fluid spray dryers must, however, be accompanied by experimental work. It has been noted [22] that even quite similar materials may behave very differently in a spray granulator. Experimental work will indicate such information as the natural mechanism of particle growth (coalescence vs layering), attainable product sizes, the preferred temperature and moisture conditions for the bed material, suitable ranges of bed voidage... 

Some trajectories pass through the transition state and return to the reactants without reaching products. Others may recross the transition state several times before attaining products. 

Figure 13 Attainable productivity and selectivity with various catalyst geometries. On each curve the thickness and load of the catalyst decrease from left to right. ki = 40 mol/m sec, k2 = OA k. Volumetric catalyst loads TBR, 4.0-55% MR incorporated type (inc) 15.1-35.5%, washcoated (wc) 8.6-28.6%, and washcoated with all active material in the comers (comers only) 0.6-6.6%. (From Ref. 26.)...

To calculate the maximum attainable production, the above procedure is repeated for different assumed levels of production. The results are shown in Table CSlO.l. However, for levels above... 

Fig. S.IO. Attainable product compositions (solid lines = distillate dashed lines = bottom product) for process configuration in Fig. 5.3...

As shown above, reaction kinetics have a significant influence on RD process performance in binary mixtures and the same is true for multicomponent mixtures. In the following, the attainable products of kinetically controlled RD processes are analyzed, first for ideal ternary mixtures, then for non-ideal ternary mixtures occurring in industrially important fuel ether synthesis, and finally for an extremely non-ideal system with potential liquid-phase splitting. In all cases, reversible reactions of type A + B o C are considered. 

Recently, the effect of interfacial mass-transfer resistances on the location of the attainable products of a reactive separation process was analyzed considering the simple model A - - B o C [23]. The analysis was based on the calculation of the top and bottom products of a separative reactor of infinite height at infinite reflux ratio (oo,oo-analysis). The products of this reactor are obtained from the following equations in matrix-vector notation... 

If [k j is a diagonal matrix, the attainable products will not be affected by interfacial mass-transfer phenomena. In contrast, if the off-diagonal elements of the [k j matrix are not vanishing, mass transfer can have a strong influence on the products. As a consequence, the attainable product region of a membrane reactor, for instance a pervaporative reactor, can be shifted by tailoring the membrane material and/or its pore structure. 

When k c = kg = 1, the off-diagonal elements of [k ] are equal to zero and the RD process discussed in Section 5.3.2 (case b) is recovered. Then, the location of the attainable product composition only depends on the vapor-liquid equilibria. In Fig. 5.24, singular point curves for the attainable bottom products of the depicted counter-current pervaporative reactor are given as a function of ky c (Fig. 5.24a) and kg (Fig. 5.24b). For each set of membrane permeabilities there is one curve of possible singular points. The ftill circles on the singular point curves indicate stable nodes, that is th mark attainable bottom products. For the system considered, stable nodes are only obtained below the chemical equilibrium line. 

The kinetics of a chemical reaction have a significant influence on the products that can be attained from a RD process. The attainable products of counterinfinite reflux ratio can be obtained as singular points of a reactive reboiler batch process (bottom product) or a reactive condenser batch process (distillate product). The compositions of both products are located on a unique singular point curve. This curve is independent of any special type of reaction kinetics. However, the locations of the top and bottom products on this curve depend on the structure of the rate equation and on the intensity of the reaction (Damkbhler number) in the considered reaction system. 

Assumptions [Given ci and C2 are two attainable product compositions] ( ) every composition that lies on the segment line belongs to the AR ( ) on the AR boimdary the reaction vector points inward, is tangent or is zero and in) in the complement of AR no reaction vector intersects the AR. 

TBD, which is practically insoluble in /j-heptane at 20 C), the base-catalyzed racemization of the ester takes place within the syringe and rac-110 is continuously returned to the reaction flask. A schematic representation of the process flowsheet is shown in Scheme 57.30. Following this procedure, highly efficient DKR of substrate rac-110 was attained, product (/ )-lll being obtained with very high yield and ee. 

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