Reactor laboratory

The large number of gas liquid solid reactors used in the laboratory can be classified into two main categories. 

Reactors to obtain accurate intrinsic kinetic rate data which are needed for design, scaleup, and optimization purposes. In these reactors the fluid dynamics and various heat and mass-transfer resistances are either known or amenable to rigorous calculations. 

Reactors to simulate closely large-scale reactors so that the information is useful and directly relevant for the proper design of a large-scale reactor. 

The laboratory reactors can also be further divided into three sections (see Table 5-1) some reactors are presently used for gas-liquid-solid reactions, some reactors are largely used for gas-solid reactions, and these can potentially be used 

Gas-solid reactors which can easily be adapted to three-phase systems  

The success of designing industrial reactors greatly depends on accurate and reliable laboratory data. These data are derived from the 

Sampling of a two-fluid phase system containing powdered catalyst can be problematic and should be considered in the reactor design. In the case of complex reacting systems with multiple reaction paths, it is important that isothermal data are obtained. Also, different activation energies for the various reaction paths will make it difficult to evaluate the rate constants from non-isothermal data. 

Measurements of the true reaction times are sometimes difficult to determine due to the two-phase nature of the fluid reactants in contact with the solid phase. Adsorption of reactants on the catalyst surface can result in catalyst-reactant contact times that are different from the fluid dynamic residence times. Additionally, different velocities between the vapor, liquid, and solid phases must be considered when measuring reaction times. Various laboratory reactors and their limitations for industrial use are reviewed below. 

The differential reactor is simple to construct and inexpensive. However, during operation, care must be taken to ensure that the reactant gas or liquid does not bypass or channel through the packed catalyst, but instead flows uniformly across the catalyst. This reactor is a poor choice if the catalyst decays rapidly, since the rate of reaction parameters at the start of a run will be different from those at the end of the run. 

If the catalyst decays during the experiment, the reaction rates will be significantly different at the end of the experiment than at the 

If the intrinsic chemical kinetics cannot be separated from transport processes at the conditions relevant for technical operation we speak of macrokinetics or effective apparent kinetics. Investigation of effective kinetics alone, that is, disregarding transport phenomena, sometimes also makes sense if the laboratory reactor intended for investigation of specific operating conditions is hydrodynamically similar to the technical reactor so that the transport parameters in both systems can also be assumed to be similar. For example, the response of a multi-tubular reactor (featuring up to 30 000 individual tubes) can easily be simulated in the laboratory, if a single tube is used, with which the response of the actual reactor under various conditions can be investigated. Unfortunately, this approach is in most cases not applicable, and so we have to determine all parameters of the micro- and macrokinetics. 

Laboratory reactors should preferably be operated (for each experiment) isother-mally to discriminate between temperature effects (activation energy) and concentration effects (reaction orders). The reaction conditions should be chosen in such a way that chemical and transport phenomena (microkinetic and macrokinetic effects), which are equally important in an industrial process, can be investigated separately. 

Two types of laboratory reactors are most suitable for kinetic investigations  

for example, the rate is first order with respect to A (which has to be proven by variation of the inlet concentration) the rate constant k is easily determined by. 

Integral evaluation means that the measured data are compared with the integrated form of the rate equation, for example, for a constant volume first-order 

There are four ideal reactors the batch reactor (real counterpart stirred tank reactor), semibatch reactor,1 continuous stirred tank reactor (CSTR), and the plug flow tubular reactor (PFTR) (real counterpart tube reactor). For production applications, there are also numerous other reactors [7-9], An overview of typical and advanced laboratory reactors was given by Kapteijn and Moulijn [6], 

The choice of the appropriate reactor applied for kinetic measurements is determined by the type of reaction (simple, parallel, or consecutive), the reaction heat and the phase state of the reaction mixture. In general, reactors with simple, almost ideal mixing behavior are preferred in order to obtain simple material balances. 

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Bosch and co-workers devised laboratory reactors to operate at high pressure and temperature in a recycle mode. These test reactors had the essential characteristics of potential industrial reactors and were used by Mittasch and co-workers to screen some 20,000 samples as candidate catalysts. The results led to the identification of an iron-containing mineral that is similar to today s industrial catalysts. The researchers recognized the need for porous catalytic materials and materials with more than one component, today identified as the support, the catalyticaHy active component, and the promoter. Today s technology for catalyst testing has become more efficient because much of the test equipment is automated, and the analysis of products and catalysts is much faster and more accurate. 

The criteria for selection of laboratory reactors include equipment cost, ease of operation, ease of data analysis, accuracy, versatility, temperature uniformity, and controllabihty, suitability for mixed phases, and scale-up feasibility. 

Many configurations of laboratory reactors have been employed. Rase (Chemical Reactor Design for Proce.s.s Plants, Wiley, 1977) and Shah (Ga.s-Liquid-Solid Reactor Design, McGraw-Hill, 1979) each have about 25 sketches, and Shah s bibliography has 145 items classified into 22 categories of reactor types. Jankowski et al. (Chemlsche Tech-nik, 30, 441 46 [1978]) illustrate 25 different lands of gradientless laboratory reactors for use with solid catalysts. 

Developments in experimental and mathematical techniques in the 1970s have initiated an interest in the development of better laboratory reactors for catal5d ic studies. Besides the many publications on new reactors for general or special tasks, quite a few review articles have been published on the general subject of laboratory reactors for catalytic studies. 

Both reactors used 38.1 mm 0 tubes. The commercial reactor was 12 m long while the length of the laboratory reactor was 1.2 m. Except for the 10 1 difference in the lengths, everything else was the same. Both reactors were simulated at 100 atm operation and at GHSV of 10,000 h-1. This means that residence times were identical, and linear gas velocities were 10 times less in the lab than at the production unit. Consequently the Re number, and all that is a function of it, were different. Heat transfer coefficients were 631 and 206 in wattsWK units for the large and small reactors. 

In gradientless reactors the catalytic rate is measured under highly, even if not completely uniform conditions of temperature and concentration. The reason is that, if achieved, the subsequent mathematical analysis and kinetic interpretation will be simpler to perform and the results can be used more reliably. The many ways of approximating gradientless operating conditions in laboratory reactors will be discussed next. 

The ROTOBERTY internal recycle laboratory reactor was designed to produce experimental results that can be used for developing reaction kinetics and to test catalysts. These results are valid at the conditions of large-scale plant operations. Since internal flow rates contacting the catalyst are known, heat and mass transfer rates can be calculated between the catalyst and the recycling fluid. With these known, their influence on catalyst performance can be evaluated in the experiments as well as in production units. Operating conditions, some construction features, and performance characteristics are given next. 

Berty, J.M., 1983, Laboratory Reactors for Catal34ic Studies, chapter 3 in J. Applied Industrial Catalysis 1, B.E. Leach, ed., pp. 41-67, Academic Press, New York. 

Figure 4-17. Differential reaotor. (Source V. W. Weekman, Laboratory Reactors and Their Limitations/ A ChEJ, Vol. 20, p. 833, 1974. Used with permission of the AlChEJ.)...

Example 4. Depolymerization under Pressure.62 PET resin was depolymerized at pressures which varied from 101 to 620 kPa and temperatures of 190—240° C in a stirred laboratory reactor having a bomb cylinder of2000 mL (Parr Instrument) for reaction times of 0.5, 1, 2, and 3 h and at various ratios of EG to PET. The rate of depolymerization was found to be directly proportional to the pressure, temperature, and EG—PET ratio. The depolymerization rate was proportional to the square of the EG concentration at constant temperature, which indicates that EG acts as both a catalyst and reactant in the chain scission process. 

Which are the main traps when studying NEMCA in a laboratory reactor ... 

The main experimental traps when studying electrochemical promotion in a laboratory reactor are ... 

Figure 2. Diagram of laboratory reactor (1) glass reactor vessel (2) inlet port (3) outlet port (4) thermocouple port (5) propeller impeller (6) turbine impeller (7) impeller shaft (8) stainless steel center plug (9) Teflon center plug (10) center bolt (11) interface plate (12) flange assembly (13) Chemco reactor support (14) Chemco reactor top closure plate (15) Chemco reactor impeller shaft bearing housing (16) reactor blead port...

The micro-mixed reactor with dead-polymer model simulated the product of the laboratory reactor well within experimental accuracy. 

In spite of visual indications of at least partial segregation, the concept of micro-mixing proved to be most useful in modeling the laboratory reactor. 

Figure 5.7. Cold-wall laboratory reactor for tungsten deposition.

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