Reactor Types, Temperature Scanning

Wojciechowski, B., The temperature scanning reactor I reactor types and modes of operation, Catal. Today 1997,... 

The temperature scanning technique as currently understood is broadly applicable and can be applied to the study of reactions in all phases, as well as on catalysts, as long as certain readily verified requirements are met. The following text is intended as a guide to kinetic studies of reaction mechanisms. It reviews reactor types that may be applicable in various circumstances, data collection methods, methods of error removal, and the interpretation of data collected using temperature scanning reactors. It is our aim to revive kinetic studies as a useful approach to the understanding of reaction mechanisms, and so put catalyst development on a rational foundation. We dedicate this book to that aid. 

Gas solid interactions are difficult to study systematically in conventional reactors but can readily be studied in a specialized type of temperature scanning reactor intended for this type of process, the stream swept reactor (SSR). In principle this is a batch reactor containing the solid through which the fluid phase flows sweeping out any desorbed material or reaction products to a detector at the outlet. Reactors of this type are also potentially applicable in adsorption studies and will be discussed in Chapter 5 under the heading TS-SSR. 

The operation and description of a temperature scanning continuously stirred tank reactor (TS-CSTR) is, in principle, much simpler than for the TS-PFR. It turns out that rates can be calculated from each individual point in each run, and that flow rates and temperature ramping do not need the same careful control as the TS-PFR. Nevertheless, the operation of die reactor should approach the perfectly mixed condition very closely. Although in practice it may be difficult to make the necessary physical arrangements for complete and instantaneous mixing within the reactor, as with other TS reactor types there are verification procedures that will reveal if proper operating conditions are not being met. 

The less well known temperature scanning stream swept reactor (TS-SSR) has features that are particularly well suited to the study of fluid/solid interactions, such as the study of ore roasting or adsorption. The TS-SSR can be constructed in two variants the TS-PF-SSR based on the PFR and the TS-CST-SSR based on the CSTR. Since the data from liquid phase TS-PF-SSR is easier to understand and interpret, we will consider this type of TS-SSR first. 

The two previous examples dealt with gas phase catalytic reactions studied in a TS-PFR. Temperature scanning, however, is not limited to this type of reaction or reactor. It is a broadly applicable technique of experimentation, applicable to a variety of chemical reactions, in a variety of reactor types. It is rare, however, to find a reaction that can conveniently be carried out in a variety of reactors. One such reaction is the hydrolysis of acetic anhydride, a liquid phase reaction with particularly simple kinetics. This reaction can therefore be used to examine the consistency of data obtained from various reactors, as well as to provide an illustration of the application of the TSR technique to a homogeneous reaction in the liquid phase. 

The theory of temperature scanning allows us to ramp the inlet temperature to a TS-PFR independently of the temperature of the reactor, as long as certain conditions are observed (see Chapter 5). However, there seems to be no special advantage to following this type of operation. The optimum solution is then to ramp both the input feed and the reactor itself along the same trajectory. 

The metal coupons in the horizontal reactor were exposed at reactor temperature to either acetylene, ethylene, propylene, or butadiene for 120 minutes. The coupons were removed from the furnace, and pictures of the coke were taken using a JSM-U3 scanning electron microscope. Most pictures were taken using a magnification of 10,000. The type of metal in the coke was determined using EDAX Model 707, that was attached to the electron scanning microscope. 

Construction of Apparatus. The schematic of the apparatus for supercritical corrosion studies is shown in Figure 1. The important components include a type 396-89 Simplex Minipump which can accurately meter (between 46 and 460 ml/hr) a wide variety of solvents at pressures up to 6000 psi (about 400 atm) an EG G Model 362 Scanning Potentiostat the electrochemical cell an IBM PC computer with interface hardware for electrochemical potential and current, temperature, and pressure measurement and control and a 316 stainless steel reactor, which holds the supercritical fluid for the measurements. The alloy was selected for excellent corrosion resistance properties and relatively low cost when compared with other exotic alloys such as Hastelloy C. 

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