Catalytic reactions solid-liquid

For a liquid-solid catalytic reaction the common technique for determining the adsorbed amount of a species dissolved in the solution is that of performing experiments in a batch not-reacting system and of measuring ... 

Several reactors are presently used for studying gas-solid reactions. These reactors should, in principle, be useful for studying gas-liquid-solid catalytic reactions. The reactors are the ball-mill reactor (Fig. 5-10), a fluidized-bed reactor with an agitator (Fig. 5-11), a stirred reactor with catalyst impregnated on the reactor walls or placed in an annular basket (Fig. 5-12), a reactor with catalyst placed in a stationary cylindrical basket (Fig. 5-13), an internal recirculation reactor (Fig. 5-14), microreactors (Fig. 5-16), a single-pellet pulse reactor (Fig. 5-17), and a chromatographic-column pulse reactor (Fig. 5-18). The key features of these reactors are listed in Tables 5-3 through 5-9. The pertinent references for these reactors are listed at the end of the chapter. 

For a gas-liquid-solid catalytic reaction, suggest laboratory reactors to carry out... 

Proper scaleup of a reactor is always a difficult but very important prohlem. What system parameter would you consider to be important in the proper scaleup of a trickle-bed reactor for a gas-liquid-solid catalytic reaction if the reaction is occurring in the liquid phase and is controlled by... 

It is propoposed to study the intrinsic kinetics of a gas-liquid-solid catalytic reaction in a bubble-column in which the catalyst is packed in a vertically hung basket. The reaction between the gaseous reactant (say hydrogen) and a liquid reactant occurs at the catalyst surface. It is, therefore, essential that possible mass-transfer resistances for hydrogen transfer to the catalyst surface are made negligible. Derive the conditions for eliminating the possible mass-transfer resistances. Assume that... 

Recommendations All existing literature data on gas and liquid holdups for countercurrent flow systems are for packings normally used in absorption towers or gas -liquid reactors. The validity of these data for small packings that would normally be used in gas-liquid-solid catalytic reactions needs to be checked. 

Example 12-3 A pilot plant for a liquid-solid catalytic reaction consists of a cylindrical bed 5 cm in radius and packed to a depth of 30 cm with 0.5-cm catalyst pellets. When the liquid feed rate is 0.2 liter/sec the conversion of reactant to desirable product is 80%. To reduce pressure drop, a radial-flow reactor (Fig. 12-5) is proposed for the commercial-scale unit. The feed will be at a rate of 5 ft /sec and will have the same composition as that used in the pilot plant. The inside radius of the annular bed is i to be 2 ft, and its length is also 2 ft. What must the outer radius of the bed be to achieve a conversion of 80% ... 

Liquid-solid (catalytic) reactions. Heat transfer is likely to be more important within the pellet than in the surrounding film, and mass transport more important in the film than within the pellet. In other words, intraphase heat transfer and interphase mass transfer would normally be the dominant transport processes. 

We now consider 12 case studies that include simple homogeneous liquid-phase reactions, complex homogeneous gas-phase reactions, gas-solid catalytic and noncatalytic reactions, gas-liquid simple and complex reactions, gas-liquid-solid (noncatalytic) reactions, gas-liquid-solid (catalytic) reactions, and solid-solid reactions. The scope and coverage of each case study are summarized in Table 11.27. In the first, homogeneous reactions are considered. For these relatively simple reactions, the possibility of optimum design is discussed. 

Case Study 11.11 Gas-Liquid-Solid (Catalytic) Reaction ... 

This case study is concerned with a three-phase gas-liquid-solid (catalytic) reaction. A systematic stepwise procedure has been described for determining the rate-controlling step, which depends on the catalyst type, particle size, operating pressure and temperature, mass transfer coefficient, and concentrations of reactants and products. As indicated, the rate-controlling step may change with location in a continuous reactor and with time in a batch reactor. 

Table 17.3 Examples of LHHW models for gas-liquid-solid catalytic reactions in organic synthesis (from Mills and Chaudhary, 1997)... 

---