Reaction, batch continuous

In ionic polymerizations termination by combination does not occur, since all of the polymer ions have the same charge. In addition, there are solvents such as dioxane and tetrahydrofuran in which chain transfer reactions are unimportant for anionic polymers. Therefore it is possible for these reactions to continue without transfer or termination until all monomer has reacted. Evidence for this comes from the fact that the polymerization can be reactivated if a second batch of monomer is added after the initial reaction has gone to completion. In this case the molecular weight of the polymer increases, since no new growth centers are initiated. Because of this absence of termination, such polymers are called living polymers. 

Reaction class Batch or fed-batch reactor characteristics Representative reaction time Continuous reactor requirements/benefits... 

Reusable in a long-term series of batch reactions or continuously in flow systems. 

Mode of operation (Semi)batch or continuous concurrent upward motion of phases Continuous concurrent upward motion of phases Continuous concurrent upwani or downward in different parts of the reaction zone Continuous concurrent upward motion of phases Continuous concurrent (1) or countercurrent (2) upward (a) or downw-ard (b) irickle-bcd (1 +b) Continuous countwcurrcni gas upward liquid downward Cominumis concurrent downward... 

The fine chemicals business is characterized by a small volume of products manufactured. Therefore, batch production predominates and small-scale reactors are used. The need to implement fine chemistry processes into existing multiproduct plants often forces the choice of batch reactors. However, safety considerations may lead to the choice of continuous processing in spite of the small scale of operation. The inventory of hazardous materials must be kept low and this is achieved only in smaller continuous reactors. Thermal mnaways are less probable in continuous equipment as proven by statistics of accidents in the chemical industries. For short reaction times, continuous or semicontinuous operation is preferred. 

A simple experiment serves to demonstrate that flow introduces a range of conversions within this fixed bed. Following the standard pre-treatment of the bed, the bed was used (a) to perform a batch reaction (i.e., under zero flow conditions), and (b) flow was then introduced to the bed and the reaction operated continuously until steady state had been achieved, at which point the conversion... 

Figure 223. Types of chemical heat pump (a) reaction phase change batch type, (b) reaction reaction batch type, (c) reaction separation work continuous type...

Semi-batch hydrogenation involves feeding the nitrile to an autoclave, containing a slurry of catalyst in the reaction product, for a specified time period after which time the nitrile feed is stopped. After the nitrile feed is stopped, the reaction will continue for a short period of time while the residual unreacted nitrile is consumed. Close monitoring of the hydrogen uptake during the time period after the nitrile feed is stopped provides insight into the rate at which... 

Batch Decomposition of Acetylated Castor Oil 243 Dispersion Model for Chromatography Columns 483 Stagewise Model for Chromatography Columns 486 Complex Reaction 237 Continuous Flow Tank 406... 

Stoichacmetry and reaction equilibria. Homogeneous reactions kinetics. Mole balances batch, continuous-shn-ed tank and plug flow reactors. Collection and analysis of rate data. Catalytic reaction kinetics and isothermal catalytic radar desttpi. Diffusion effects. 

In this chapter we consider the fundamentals of reaction in continuous isothermal reactors. Most industrial reactors are operated in a continuous mode instead of batch because continuous reactors produce more product with smaller equipment, require less labor and maintenance, and frequently produce better quahty control. Continuous processes are more difficult to start and stop than batch reactors, but they make product without stopping to change batches and they require rninimum labor. 

The steady-state solutions for these reactions in continuous reactors have interesting characteristics. In a PFTR the solution is simply the solution for the batch reactor,... 

Gas-phase reaction in continuous and semi-batch operations... 

Biochemical reactors can be operated either batchwise or continuously, as noted in Section 1.5. Figure 7.1 shows, in schematic form, four modes of operation with two types of reactors for chemical and/or biochemical reactions in Uquid phases, with or without suspended solid particles, such as catalyst particles or microbial cells. The modes of operation include stirred batch stirred semi-batch continuous stirred and continuous plug flow reactors (PFRs). In the first three types, the contents of the tanks arc completely stirred and uniform in composition. 

Monoliths exhibit a large flexibility in operation. They are well suited for optimal semibatch, batch, continuous, and transient processing. Catalytic conversion can be combined with in situ separation, catalytic reactions can be combined, heat integration is possible, and all lead to process intensification. In the short term, catalytic monoliths will be applied to replace trickle-bed reactor and slurry-phase... 

Knowledge of these types of reactors is important because some industrial reactors approach the idealized types or may be simulated by a number of ideal reactors. In this chapter, we will review the above reactors and their applications in the chemical process industries. Additionally, multiphase reactors such as the fixed and fluidized beds are reviewed. In Chapter 5, the numerical method of analysis will be used to model the concentration-time profiles of various reactions in a batch reactor, and provide sizing of the batch, semi-batch, continuous flow stirred tank, and plug flow reactors for both isothermal and adiabatic conditions. 

The experimental study of solid catalyzed gaseous reactions can be performed in batch, continuous flow stirred tank, or tubular flow reactors. This involves a stirred tank reactor with a recycle system flowing through a catalyzed bed (Figure 5-31). For integral analysis, a rate equation is selected for testing and the batch reactor performance equation is integrated. An example is the rate on a catalyst mass basis in Equation 5-322. 

The four principal types of reactors used for bench-scale kinetic studies are batch, continuous stirred-tank (CSTR), tubular, and differential reactors. Which of these to choose is essentially a matter of the reaction conditions, available equipment, and the chemist s or engineer s predilections. The discussion here will focus on facets that pertain specifically to quantitative kinetic studies of homogeneous reactions. 

The simplicity and general utility of the Madon-Boudart criterion make it one of the most important experimental tests to confirm that kinetic data are free from artifacts. It can be used for heterogeneous catalytic reactions carried out in batch, continuous stirred tank, and tubular plug flow reactors. 

On the other hand, an industrial process may be operated in a continuous mode, rather than in a batch mode. To achieve this, either a single or a series of interconnected vessels may be used. The required raw materials are continuously fed into this vessel or the first vessel and the reaction products continuously removed from the last so that the volume of material in the reactor(s) stays constant as the reaction proceeds. The concentrations of starting materials and products in the reactor eventually reach a steady state. One or more tanks in series may be used to conduct the continuous process. Another option for a continuous process is to use a pipe or tube reactor, in which the starting material(s) is fed into the tube at one end, and the product(s) is removed at the other. In this case, the reaction time is determined by the rate of flow of materials into the tube divided by the length of the tube. 

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