Hydrogenation of a-methyl styrene

The Hydrogenation of a-Methyl Styrene in an Agitated Tank Slurry Reactor... 

The performance of a three-phase fluidised-bed is to be assessed in relation to a model reaction, the hydrogenation of a-methyl styrene at 50°C. The same catalyst will be used as in Example 4.6, excepting that the diameter of the spherical particles will be 2.0 mm. The liquid and gas flowrates will be such that the volume fraction of particles in the bed will be 0.50 and the volume fraction of gas 0.20 i.e. the relationship shown in Fig. 4.21 will apply, from which the estimated bubble size is 5.0 mm. 

Hydrogenation of a-methyl styrene containing a slurry of palladium black or alumina-supported palladium catalyst 37, 88. 96. 107, 110... 

The three-phase continuous countercurrent fluidized-bed reactor and the spouted-bed reactor have been used on the laboratory scale. Pruden and Weber88 have shown that the countercurrent mode of operation for hydrogenation of a-methyl styrene performs better than the cocurrent fixed-bed operation under similar reaction conditions. 

In general, the above equations are best solved in a computer. Goto et al.9 obtained a solution to the case where species C is in excess so that the reaction is pseudo-first-order. They used the solution to analyze the efficiency of reaction systems such as oxidation of ethanol, hydrogenation of a-methyl styrene, and hydrogenation of aniline. They defined... 

When both gas and liquid flow downward over a string of spheres, it can simulate a trickle-bed reactor if the liquid flows downward in the form of a thin film. The hydrodynamics for this type of reactor are reasonably well known. Both the hydrodynamics of the liquid flow over a single sphere and the phenomena taking place at the junctions of two spheres have been extensively studied. Flow maldistribution encountered in the pilot-scale trickle-bed reactor is eliminated in this type of reactor. Furthermore, good estimations of the various mass-transfer resistances can be ascertained. The reactor is successfully used by Satterfield et al.st) for the catalytic hydrogenation of a-methyl styrene. Their experimental setup is shown in Fig. 5-9. 

Snider and Perona3 measured Ksas, the volumetric liquid-solid mass-transfer coefficient, for the case of hydrogenation of a-methyl styrene on 3-mm alumina spheres coated with palladium catalyst. The results were obtained in the bubble-flow regime. The measurements of Ks, the liquid-solid mass-transfer coefficient in a nonreacting system, were first reported by Mochizuki and Matsui.20 They... 

The three-phase fluidized-bed reactor with countercurrent mode of operation was used by Pruden and Weber 10 to study the hydrogenation of a-methyl styrene to cumene in the presence of palladium black catalysts. They used low gas velocities so that the gas was dispersed as bubbles in the slurry. They showed that the countercurrent mode of operation was better than the slurry operation (with no liquid flow), due to improved catalyst usage and improved gas holdup characteristics. 

The liquid-phase hydrogenation of a-methyl styrene to cumene,... 

The hydrogenation of a-methyl styrene to cumene is a popular reaction for laboratory studies [43-45], and it can be either gas limited or liquid limited, depending on reaction conditions. With a 2.5% Pd/Al203 catalyst, the reaction was very rapid at 1 atm and 40°C, and the effectiveness factor was less than 0.1 for 0.3-cm particles [43]. Under there conditions, the reaction rate decreased by 25% as the liquid rate was increased about 10-fold. The decrease occurred because the effect of lower hydrogen concentra-... 

Pseudo first order reactions with respect to the gaseous reactant, i,e, in case of large excess of B, have been studied in detail to describe systems as oxidation of ethanol, hydrogenation of a-methyl styrene, hydrogenation of aniline etc. Limiting cases, such as plug flow of both gas and liquid phases [46] or a constant concentration in the gas phase [48], were analysed as well as the general case of finite values of dispersion coefficients in both phases [52,58],... 

The Stability of a conjugated radical accounts for the greater reactivity of vinylarenes and conjugated dienes versus that of unconjugated monoenes. A well-documented example of hydrogen atom addition to olefins by this radical pathway is the hydrogenation of a-methyl styrene by HMn(CO)j Halpem used CIDNP (cherrucally induced dynamic nuclear polarization) to establish this radical reaction path. 

The rate of hydrogenation of a-methyl styrene over a rotating string of catalyst particles was 5 to 7 times faster than that of the rate achieved in a gravity flow reactor. A 60x faster rate is achieved compared to a trickle bed of alumina beads that are 2.5 mm in size. An industrial trickle bed reactor of 60 m can be replaced with a 1-m rotating bed reactor. 

Satterfield et al. studied the liquid-phase hydrogenation of a-methyl styrene to cumene over a 1 wt.% Pd/alumina catalyst. The catalyst was spherical, with a diameter of 0.825 cm and a porosity e of 0.50. The tortuosity Tp was measured and found to be approximately 8. 

Hydrogenation of a methyl styrene to cumene Multi channel stmcture with T-configuration Useful for gas/ liquid or Uquid /liquid reactions... 

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