Reactors homogeneous liquid

Homogeneous reactions are those in which the reactants, products, and any catalysts used form one continuous phase (gaseous or liquid). Homogeneous gas phase reactors are almost always operated continuously, whereas liquid phase reactors may be batch or continuous. Tubular (pipeline) reactors arc normally used for homogeneous gas phase reactions (e.g., in the thermal cracking of petroleum of dichloroethane lo vinyl chloride). Both tubular and stirred tank reactors are used for homogeneous liquid phase reactions. 

An nth-order homogeneous liquid phase reaction is carried out in a batch tank reactor. 

Figure 12.3 illustrates some modes of operation of semibatch reactors. In Figure 12.3(a), depicting a homogeneous liquid-phase reaction of the type A + B - products, reactant A is initially charged to the vessel, and reactant B is added at a prescribed rate, as reaction proceeds. In Figure 12.3(b), depicting a liquid-phase reaction in which a... 

Esterification is the first step in PET synthesis but also occurs during melt-phase polycondensation, SSP, and extrusion processes due to the significant formation of carboxyl end groups by polymer degradation. As an equilibrium reaction, esterification is always accompanied by the reverse reaction being hydrolysis. In industrial esterification reactors, esterification and transesterification proceed simultaneously, and thus a complex reaction scheme with parallel and serial equilibrium reactions has to be considered. In addition, the esterification process involves three phases, i.e. solid TPA, a homogeneous liquid phase and the gas phase. The respective phase equilibria will be discussed below in Section 3.1. 

In typical industrial operations, TPA is not dissolved in EG or BHET but in prepolymer. The latter contains PET oligomers with one to approximately six to eight repeat units and a significant concentration of carboxyl end groups of between 200 and llOOmmol/kg. It was found [94] that the solubility of TPA in prepolymer is much higher than indicated by the values given in the literature. Nevertheless, the esterification reactor still contains a three-phase system and only the dissolved TPA may react with EG in a homogenous liquid-phase... 

The kinetics of a homogeneous liquid reaction are studied in a flow reactor, and to approximate plug flow the 48-cm long reactor is packed with 5-mm nonporous pellets. If the conversion is 99% for a mean residence time of 1 sec, calculate the rate constant for the first-order reaction... 

The correlations for as discussed above are for homogeneous liquids. Bubbling gas-liquid reactors are sometimes used for suspensions, and bioreactors of this type must often handle suspensions of microorganisms, cells, or immobilized cells or enzymes. Occasionally, suspensions of nonbiological particles, to which organisms are attached, are handled. Consequently, it is often necessary to predict how the values for suspensions will be affected by the system properties and operating conditions. In fermentation with a hydrocarbon substrate, the substrate is usually dispersed as droplets in an aqueous culture medium. Details of... 

Aluminum Chloride-Based Alkylation. An improved aluminum chloride-based process was developed by Monsanto in the 1970s. Using a presynthesized aluminum chloride complex and operating the reactor at higher temperature and pressure, the catalyst inventory is reduced to below its solubility in the reaction mixture. The reactants and the catalyst complex are mixed in the reactor to form a homogeneous liquid. The transalkylation... 

As an alternative to investigating the kinetics of a gas-liquid reaction on a laboratory scale, the mass transfer resistance may be minimised or eliminated so that the measured rate corresponds to the rate of the homogeneous liquid-phase reaction. This method of approach will be considered after first describing those reactors giving rise to controlled surface exposure times. 

Modeling of Chemical Kinetics and Reactor Design ACID-BASE CATALYSIS HOMOGENEOUS LIQUID PHASE... 

The holdups can play an important role in the reactor performance. For example, in a pilot-scale trickle-bed reactor, the liquid holdup can play an important role in changing the nature of the apparent kinetics of the reaction. When homogeneous and catalytic reactions occur simultaneously, the liquid holdup plays an important role in determining the relative rates of homogeneous and catalytic reactions. In a three-phase fluidized-bed reactor, the holdup of the solid phase plays an important role in the reaction rate, particularly when the solid phase is a reactant. The gas holdup, of course, always plays an important role in reactor performance when a gaseous reactant takes part in the reaction. 

Several advantages and disadvantages of a trickle-bed reactor are listed in Table 1-5. The commercial trickle-bed reactors are operated under plug-flow conditions. The catalysts are effectively wetted. These factors allow high conversion to be achieved in a single reactor. The liquid-to-solid ratio (or liquid holdup) in a trickle-bed reactor is small, thus minimizing the importance of homogeneous... 

High liquid holdup and liquid-to-solid ratio in an upflow reactor. High liquid holdup will offer more liquid-phase resistance to the mass transfer of the gaseous reactant to the catalyst surface. High liquid-to-solid ratio will give more importance to the role of possible homogeneous reactions. 

The analytical problems associated with differential reactors can be overcome by the use of the recirculation reactor. A simplified form, called a Schwab reactor, is described by Weisz and Prater . Boreskov.and other Russian workers have described a number of other modifications " . The recirculation reactor is equivalent kinetically to the well-stirred continuous reactor or backmix reactor , which is widely used for homogeneous liquid phase reactions. Fig. 28 illustrates the principle of this system. The reactor consists of a loop containing a volume of catalyst V and a circulating pump which can recycle gas at a much higher rate, G, than the constant feed and, withdrawal rates F. 

Fresh and recycled ethylene plus octane solvent are fed into the dimerization reactor operating at 100 atm. and 80°C. The dimerization takes place in a homogeneous liquid phase and proceeds rapidly at the rate of one mole of butene-1 formed per min. per mole of the catalyst. 

In the latest version of aluminum chloride plant designs, the alkylation reactions occur in a homogenous liquid phase at 160-180" C. The conditions of the alkylation reactor prohibit the recycle of PEB to the reactor. As a result, these plants have a separate transalkylation reaction zone. The recycle PEB stream is mixed with the alkylation reactor effluent and fed to the transalkylation reaction zone. The aluminum chloride present in the alkylation reactor effluent catalyzes the transalkylation reactions. 

There are many examples of the application of CD or RD for esterification.f" Esterification of methanol or ethanol with acetic acid forms methyl acetate or ethyl acetate, respectively. Methyl acetate is important in the manufacture of polyesters and is an important solvent for cellulose while ethyl acetate is used in inks, fragrances, and pharmaceuticals. The manufacture of high-purity methyl acetate is difficult because of the equilibrium limitation and also the formation of azeotropes. The production of methyl acetate by Eastman Chemical Co. was the first commercial application of RD using a homogeneous liquid acid catalyst. Only one RD column and two smaller columns for processing sidestreams are required while in the conventional methyl acetate synthesis, two reactors and eight distillation columns are required. 

A homogeneous liquid-phase polymerization is carried out in a completely mixed stirred-tank reactor which has an average residence time of 33.6 sec. The concentration of monomer in the feed stream is 1.0 x 10 - g mole/cm-. The polymerization reactions follow a two-step process ... 

Example 5-4 A first-order homogeneous (liquid-phase) reaction is carried out in an ideal stirred-tank reactor. The concentration of reactant in the feed is 3.0 g moles/liter and the volumetric flow rate is 60 cm /sec. The density and specific heat of the reaction mixture are constant at I.O g/cm and 1.0 cal/(g)(°C), respectively. The reactor volume is 18 liters. There is no product in the feed stream and the reactor operates adiabatically. The heat and rate of the irreversible reaction are... 

In the laboratory either integral or differential (see Sec. 4-3) tubular units or stirred-tank reactors may be used. There are advantages in using stirred-tank reactors for kinetic studies. Steady-state operation with well-defined residence-time conditions and uniform concentrations in the fluid and on the solid catalyst are achieved. Isothermal behavior in the fluid phase is attainable. Stirred tanks have long been used for homogeneous liquid-phase reactors and slurry reactors, and recently reactors of this type have been developed for large catalyst pellets. Some of these are described in Sec. 12-3. When either a stirred-tank or a differential reactor is employed, the global rate is obtained directly, and the analysis procedure described above can be initiated immediately. 

A continuous reactor is to be designed for a homogeneous liquid-phase reaction A R. The reaction is first order with respect to A, and the rate is given by... 

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