Reactor Distillation

The reactor combinations for the two reactors in series consist of two fixed-beds for the Arco process an expanded bed followed by a catalytic distillation reactor for lEP a fixed-bed followed by a catalytic distillation reactor for CDTECH and two fixed-beds for Phillips. The Huls process uses an adiabatic reactor for the second reactor. 

CD-Cumene A process for making cumene for subsequent conversion to phenol and acetone. The cumene is made by catalytic alkylation of benzene with propylene in a catalytic distillation reactor. Developed in 1995 by CDTech. 

Distillation processes, 26 61-73. See also Distillation(s) freeze-desalination, 26 71 materials and scaling issues in, 26 71-73 multi-effect distillation, 26 65-67 multistage flash evaporation, 26 61-65 vapor compression distillation, 26 67 Distillation reactors, 21 332 Distillation region diagrams (DRD), 22 302, 303, 331... 

Figure 12-18 Catalytic distillation reactor in which catalyst in the distil- t. lation column combines chemical reaction with vapor-liquid equilibrium in the column to achieve conversions higher than obtainahle with a reactor alone.

The catalytic distillation reactor is in effect a multistage reactor, where each tray achieves equilibririm at its temperature and composition, with the temperature being lower at the top, where there is more B and higher at the bottom, where there is more C. With a high reflux ratio in the condenser to return any or C to the column, one can attain essentially complete reaction and separation of the products from each other. 

As with the catalytic distillation reactor, the chromatographic reactor functions as a multistage reactor. The chromatographic reactor is essentially a batch reactor, and we need to adapt this configuration into a continuous process to develop a large-scale and economic process. 

The residue in the distillation reactor is then reconstituted with water, refiltered and sent on for iron removal. The iron is removed by conversion to jarosite (NaPe3 (SO4) 2 (CH) 6). The jarosite is filtered away and converted back to ferrous sulfate (FeS04) far sale to the fertilizer and water treatment industries. Approximately 1000 lbs of FeS04 7H20 are generated from each 20 ton batch. 

Because pH of the medium is so essential for the alcoholysis of triace-toxyphenylsilane, at this stage the acidity of the reactive mixture is monitored. pH should be about 1+2. If pH >2, reactor 5 is filled with an additional quantity of phenyltrichlorosilane from batch box 2, reducing the temperature to 30-40 °C prior to that. After phenyltrichlorosilane has been added, the mixture in the apparatus is held at 45-55 °C at least for 1 more hour and then checked for acidity and appearance. If the analysis is positive (pH 1+2), the mixture is sampled and sent to the laboratory, where tri-acetoxyphenylsilane is subjected to alcoholysis with methyl alcohol to determine the onset temperature for the distillation of methylacetate (58-68 °C in the reactive mixture). If at this temperature methylacetate does not distil, reactor 5 is filled from batch box 2 with an additional amount of phenyltrichlorosilane. The sample is chosen in such a way that the solid and liquid phases are approximately 1 1. 

In case if at 67-75 °C methylacetate is not distilled, reactor 1 receives from weight batch box 4 an additional quantity of organochlorosilanes to create an acid medium in the reactive mixture after that the reactive mixture is heated to 67 °C and methylacetate is distilled. 

Distillation reactor (Fig. 1.1c)—A batch reactor where volatile products are removed continuously from the reactor during the operation. 

Figure 1.1 Batch operations (a) batch reactor, (b) semibatch reactor, and (c) distillation reactor.

Figure 2.2 Various reactor Configurations (a) semibatch, (b) distillation reactor, (c) split feed, (d) cascade, (e) recycle reactor, and (/) side injection.

In this chapter, the analysis of chemical reactors is expanded to additional reactor configurations that are commonly used to improve the yield and selectivity of the desirable products. In Section 9.1, we analyze semibatch reactors. Section 9.2 covers the operation of plug-flow reactors with continuous injection along their length. In Section 9.3, we examine the operation of one-stage distillation reactors, and Section 9.4 covers the operation of recycle reactors. In each section, we first derive the design equations, convert them to dimensionless forms, and then derive the auxiliary relations to express the species concentrations and the energy balance equation. 

A distillation reactor is a liquid-phase ideal hatch reactor where volatile products are generated and continuously removed from the reactor, as shown schematically in Eigure 9.4. Because species are removed, the volume of the reacting fluid reduces during the operation. 

This is the differential design equation for a distillation reactor, written for the mth-independent chemical reaction. Note that Eq. 9.3.2 is identical to the design equation of an ideal batch reactor. The difference between the two cases is in the variation of the reactor volume and species concentrations during the operation. 

Equation 9.3.12 is the dimensionless, reaction-based design equation for distillation reactors, written for the mth-independent reaction. To describe the operation, we have to write Eq. 9.3.12 for each independent reaction. 

Due to evaporation, most distillation reactors operate isothermally. To determine the rate, heat is transferred to (or from) the reactor, we also have to solve the energy balance equation. We modify the energy balance equation (Eq. 5.2.8) by adding a term to account for the enthalpy removed from the reactor by the evaporating species ... 

Example 9.4 The dehydration of two heavy organic species, reactants A and B, is carried out in a distillation reactor where the water, product C, is being removed continuously. The reactor is initially charged with a 60-L organic solution that contains 200 mol of reactant A and 300 mol of reactant B. The reactor is operated isothermally at 200°C, and the following reactions take place in the reactor ... 

The analysis of chemical reactor operations is limited to simple reactor configurations (i.e., batch, tubular, CSTR), with little, if any analysis, of other configurations (i.e., semibatch, tubular with side injection, distillation reactor),... 

The reaction was carried out in both batch and distillation reactor. 0.5 g catalyst (0.2-0.3 mm grain) was used for the catalyst activity test in a stainless batch reactor with 6 1 ratio of methanol to propylene carbonate. After the reaction proceeded for 2h at 160°C under constant stirring, the reactor was cooled down to room temperature and the products were then analyzed on a gas chromatograph with a TCD after centrifugal separation from the catalyst. 

For stability investigation, the reaction was continuously carried out in a reactive distillation reactor. The catalyst (0.71-1.0mm grain) was filled in the reactive column. Before reaction, N2 was introduced into the reactor and compressed to desired pressure. The products of both tower top and bottom were taken out each 12h for analysis. 15g catalysts were used for the distillation reaction with LHSV of 0.03h at 160 C and 0.6MPa. 

A catalytic distillation reactor system including three zeolite catalyst layers or their ion-exchanged varieties was used for oligomerization of all kinds of olefins, not only a-olefins. 

Catalytic distillation reactor system, temperature range from ca. 150"C to approx. 350 °C depending on catalyst type Zeolite catalyst samples were tested over a range of temperatures (140-300 °C) in a batch reactor for 4h... 

Parker (12) recommended the use of a distillation reactor for hydrolyzation of ethylene oxide to ethylene glycol. Miller (13), and subsequently Corrigan and Miller (14), analysed this process using a crude plate model and concluded that increased temperature in the distillation reactor adversely affected selectivity of the process as com )ared to the two-stage Shell process. However, this was disproved by Sive (15) who found no effect on selectivity of operating pressure or feed composition when modelling a packed distillation reactor for this process. 

Geelen and Wijffels (19) investigated the reaction of vinyl acetate with stearic acid in a distillation column to form vinyl stearate and acetic acid. A modified form of the McCabe-Thiele diagram was employed to obtain the number of theoretical plates for a given conversion. This was tested experimentally using a bubble-cap Oldershaw column for the distillation reactor followed by a packed column for separation of top products (vinyl acetate acetic acid). Theoretical considerations agreed reasonably well with experimental findings. 

Hirata (22) also studied the behaviour of an Oldershaw column, a packed column and a sieve-tray column as distillation reactors for the esterification of ethanol and acetic acid. He found reflux ratio to be an important factor affecting not only separation but also conversion. 

Nelson (24) studied theoretically the general case of countercurrent equilibrium stage separation with chemical reaction and applied his technique to describe distillation reactors. His model relied on the assumption of each stage being a perfectly mixed reactor and also an equilibrium stage. 

Pilavakis (20, 29) investigated the esterification of methanol by acetic acid in a packed column. He assumed the reaction to be pseudo-first-order with respect to either methanol or acid over certain specified concentration ranges and incorporated the effect of heat of reaction not only in the enthalpy balances but also in the flux equations. The column was calculated by numerical solution of a set of differential equations. The top product was an azeotropic mixture of methanol and ester which could, however, be broken by introduction of acetic acid high up in the column rather than further down as a mixed feed with methanol. Consequently, in practice such a column will consist of a rectifying section, an extractive distillation section with acetic acid as the extractive solvent and a distillation reactor section. Good agreement was obtained between theory and experiment which, however, suffered from the fact that the hold-up of liquid in the column was small in comparison to the reboiler hold-up so that most of the reaction occurred in the latter location. 

---