Catalysts stirring speed

Liquid-liquid biphasic reaction was carried out in a 70-mL autoclave at a stirring speed of 1600 rpm with a catalyst charge of c(Rh) = 0.018x10"5 mol in 4mL ionic liquid. 

Fig. 3. Dependence of fcobsd on stirring speed and particle size (mesh) of 2% CL catalysts I for reaction of 1-bromooctane in to-hienewith 10 molar equiv of NaCN in water and 0.02 molar equiv of catalyst at 90 °C. (Reprinted with permission from Ref. 73). Copyright 1981 American Chemical Society)...

The dependence of kobsd on stirring speed for Br-I exchange reactions with polymer-supported crown ethers 34 and 35 has been determined under the same conditions as with polymer-supported phosphonium salts 1 and 4149). Reaction conditions were 90 °C, 0.02 molar equiv of 100-200 mesh catalyst, 16-17% RS, 2% CL, 20 mmol of 1-bromooctane, 200 mmol of KI, 20 ml of toluene, and 30 ml of water. Reaction rates with 34 and 35 increased with increased stirring speed up to 400 rpm, and were constant above that value. This result resembles that with polymer-supported onium ion catalysts and indicates that mass transfer as a limiting factor can be removed in experiments carried out at stirring speeds of 500-600 rpm, whatever kind of polymer-supported phase transfer catalyst is used. 

Fig. 10. Dependence of on mean particle size of 2% CL catalyst for reaction of 1-bromo-octane in toluene with 10 molar equiv of KI in water and 0.02 molar equiv of catalyst at 90 °C 16% RS catalyst 34 (A), 17% RS catalyst 35 ( ), 14% RS catalyst 41 (O) stirring speed 550-600 rpm...

The kinetics of the reaction of solid sodium iodide with 1-bromooctane were studied with a 95 % RS graft of polyethylene oxide) 6-mer methyl ether on 3 % CL polystyrene as catalyst (51)176). The rates were approximately first order in 1-bromooctane and independent of the amount of excess sodium iodide. The rates varied with the amount of the solid catalyst used, but there was not enough data to establish the exact functional dependence. All experiments employed powdered sodium iodide, magnetic stirring, and 75-150 pm catalyst beads. Thus the variables stirring speed and particle size, which normally are affected by mass transfer and intraparticle diffusion, were not studied. Yanagida 177) favors a mechanism of transfer of the sodium iodide by dissolution in the solvent (benzene) and diffusion to the catalyst particle... 

At the chosen acetophenone concentration (0.3mol.l ), the reaction is not limited by gas-liquid transfer for a stirring speed comprised Detween 1500 and 2000 rpm and the reaction rate is independent of the catalyst weight (0.1[Pg.246]

Describe the processes involved in the synthesis of the drug substance. The description synthesis should include information on the following (a) pieces of equipment used (b) quantities of starting material(s) reagents, solvents, catalysts (c) workup and isolation procedures (d) reaction conditions such as temperature, pH, and time (h) purification procedures (i) manipulative details including addition rate, stirring speed, pressure, and order of addition and (j) yields (crude and/or purified weight and percent). 

With the Co(II)EDTA and Co(III)EDTA system [254] the experiments were carried out at pH 2 where the main cobalt(III) species was Co(EDTA) (99%) while the main cobalt(II) species were Co(HEDTA) (H20) (86%) and Co(ED-TA)2 (11%). Platinum black surfaces were employed as catalysts but some problems were experienced with gradual loss of activity. The catalysis was again surface-controlled since the rates were independent of stirring speed... 

Effect of agitation on the rate of 2-propanol dehydrogenation to acetone at 355 K over Ni catalysts. [Rates are calculated at constant conversion level from the data in D. E. Mears and M. Boudart, AIChE J., 12 (1966) 313.] In this case, increasing the stirring speed increased the rate of acetone diffusion away from the catalyst pellet and decreased product inhibition. 

The reaction takes place on the catalyst housed in three stationary beds in the reactor. The catalyst used for the l-hexene isomerization reaction is a commercial E-302 reforming catalyst, supplied by Engelhard corporation. The bifunctional catalyst is composed of 0.6 wt% Platinum supported on 1/16" right cylindrical gamma-alumina extrudates. To minimize external mass-transfer resistances and to achieve CSTR behavior, the fluid phase containing the reactants is kept mixed by an impeller powered by a 0.75 hp MagneDrive assembly that can provide stirring speeds up to 3,000 rpm. Unconverted reactant, product and the SCF medium exit via a port located at the top of the reactor. 

Microporous (gel-type) substrates are prepared by bead polymerization. In this process, the two monomeric compounds, styrene and divinylbenzene, are suspended as small droplets in water by rapid, even stirring. The polymerization is initiated by appropriate catalysts and leads to uniform particles, which have a microporous structure and a size distribution depending on the stirring speed. In general, a decrease of the average particle size is observed with increasing stirring speed. 

Hint Defining [M]o = monomer concentration at the gas-liquid interface, [M] = average concentration of monomer in solution, [cat] = concentration of catalyst, = mass transfer constant (dependent on stirring speed), and = polymerization rate constant, the mass balance for the... 

Initially, a simple Mariotte volumetric method was used to investigate the mass transfer behavior in the catalyst activation. The experimental Mariotte apparatus is represented schematically in Fig. 5 and consisted of a stirred vessel (300 mL) containing acetic acid (200 mL used as reactant and solvent) and the (salen)Co(II) complex to be oxidized. The system was hermetically in contact with pure oxygen at atmospheric pressure. Oxygen consumption was volumetrically determined over time for activation reactions using three different stirring speeds. The use of... 

Now imagine the problem with nuclear waste. We cannot alter the rate at which it decays. This is defined by the half-life. We can t heat it, stir it, or add a catalyst to speed up the process as we can with chemical reactions. Furthermore, the half-lives of many nuclear waste products are very long plutonium, for example, has a half-life in excess of 24,000 years. Ten half-hves are required for the radioactivity of a substance to reach background levels. So we are talking about a very long storage time. 

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