Dynamic analysis of homogeneous reactions in a stirred bubble reactor: Oxidation of sulfite

Fu, Chen‐Chen; Smith, J. M.; McCoy, Benjamin J.

doi:10.1016/0009-2509(88)85094-2

Cited by 9 publications

(3 citation statements)

References 24 publications

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“…The value of k L , calculated using the mean diameter of 0.5 mm, is 0.13 cm s –1 . This is close to a value of 0.1 cm s –1 given by Fu, Smith, and McCoy for a well-stirred agitated vessel …”

Section: Resultssupporting

confidence: 88%

“…This is close to a value of 0.1 cm s −1 given by Fu, Smith, and McCoy for a well-stirred agitated vessel. 24 Observation of bubble formation vs pressure drop revealed that, as the driving pressure increased, the main effect was the increase in the number of sites on the frit from which bubbles emerged. A comparison with water as the liquid showed a significantly higher pressure was required to obtain the same flow rate, and that, at the same flow rate, the number of bubble forming sites was much less, resulting in a larger bubble size.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Scale-down of Heterogeneous Catalytic Reduction Using a Bubble Column: Controlled Mass Transfer down to 3 cm³ Working Volume

Atherton

Elmekawy

Hall

et al. 2015

Org. Process Res. Dev.

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Best practice for scale-down of gas−liquid reactions requires control of the volumetric mass transfer coefficient, k L a. It is demonstrated that the use of small bubble columns can provide well-controlled k L a and catalyst dispersion down to a scale of 3 cm 3 . This scale is several times less than has been previously demonstrated for heterogeneously catalysed reduction using gaseous hydrogen and is more easily reproduced than small scale stirred vessels. Measurements have been made at a fixed total gas flow, with the effective mass transfer rate being adjustable by dilution of the hydrogen flow with either helium or nitrogen. ■ INTRODUCTIONDuring the early stages of chemical process development, the quantity of available starting material often restricts the scale on which development work can be conducted. This can be problematical in the case of gas−liquid reactions, in particular hydrogenation, where selectivity is often sensitive to the solution concentration of hydrogen and consequently to the relative rates of reaction and mass transfer. In these cases control of the volumetric mass transfer coefficient, k L a, is necessary to ensure that laboratory experimentation can properly simulate the processing conditions expected on the manufacturing scale. There are many examples of the sensitivity of hydrogenation processes to operating conditions. Sun et al. 1 first pointed out the interplay between hydrogen pressure, the volumetric mass transfer coefficient and the intrinsic chemical kinetics in determining the rate of a hydrogenation process and further pointed out that, in the case of parallel competing processes, relative rates and hence selectivities could be a function of these three variables. A range of examples confirms the generality of this principle with respect to olefin and ketone hydrogenation. 2−4 Merck workers also encountered the effect in the catalytic hydrogenation of an imine, in which some defluorination of an aryl fluoride occurred under "hydrogen starved" conditions, 5 and were able to devise satisfactory manufacturing conditions based on a knowledge of the volumetric mass transfer coefficient under operating conditions. In the hydro-dechlorination of a benzyl chloride, dimerization instead of reduction occurred under hydrogen starved conditions. 6 Hydrogen starvation is implicated in problems with the reduction of nitro compounds, where azo and azoxy byproducts can be formed, 7 and where leaching of metal from the catalyst support can occur. 8 Reduction of nitriles is extremely sensitive to the processing conditions, and formation of secondary 9 and tertiary amines via trapping of the intermediate imines with the first-formed primary amine is well-known, and avoidance of hydrogen starvation is one component of strategies used to achieve a good yield of primary amine products. 10 As a consequence of these considerations, it is now accepted in major pharma and agrochemical companies that "best practice" in the design and scale-up of hydrogenation processes using molecular hydrogen (as op...

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Section: Resultssupporting

confidence: 88%

Section: ■ Results and Discussionmentioning

confidence: 99%

Scale-down of Heterogeneous Catalytic Reduction Using a Bubble Column: Controlled Mass Transfer down to 3 cm³ Working Volume

Atherton

Elmekawy

Hall

et al. 2015

Org. Process Res. Dev.

View full text Add to dashboard Cite

show abstract

“…These results address the microscale phenomena taking place close to the gas-liquid interface. As such, they may be incorporated into the design models by Pandya (1983), De Leye and Froment (1986), Yu and Astarita (1987), Fu et al (1988), Tontiwachwuthikul et al (1989), and Carey et al (1991). …”

Section: Discussionmentioning

confidence: 99%

Role of liquid reactant volatility in gas absorption with an exothermic reaction

Al-Ubaidi

Selim

1992

AIChE Journal

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A film-theory model is presented for nonisothermal gas absorption with a secondorder In trod uc t ionMany industrially important gas-liquid reactions, such as oxidation, sulfonation, nitration, halogenation, and alkylation, are highly exothermic in nature. In these processes, two types of heat are generated: the heat of solution that is generated at the gas-liquid interface; the heat of reaction that is generated within the mass transfer film near theminterface for fast reactions or within the bulk liquid for slow reactions. The release of the heat of solution and reaction during absorption may result in significant temperature increase at the interface, which in turn affects the absorption rate behavior. Thus, in heating the liquid, it increases the rate of reaction and diffusion further steepening the concentration gradient near the gasliquid interface and thereby increasing the absorption driving force. But it also decreases the solubility of the gas in the liquid, thereby decreasing the absorption driving force. Hence, the overall rate of absorption is a result of the combination of these two opposing effects.Such an interfacial temperature rise has been observed by Basil Al-Ubaidi is with The M. W. Kellogg Company, Houston, TX, several investigators. For instance, Mann and Clegg (1975) and Mann and Moyes (1 977) indirectly measured temperature rises up to 53°C for chlorination and 58°C for sulfonation using a laminar jet technique, whereas Ponter et al. (1974) measured the interfacial temperature rise directly by an infrared technique and found a 20°C rise for sulfonation. Increases of this magnitude will significantly affect the solubility; hence, this phenomenon needs to be understood for the design of absorption-reaction systems. For first-order reactions, the interfacial temperature rise and the relevant enhancement factor have been analyzed theoretically by several investigators. These were mainly carried out using either the film or the penetration models (Danckwerts, 1953;Shah, 1972;Mann and Moyes, 1977;Asai et al., 1985;Chatterjee and Altwicker, 1987). The more general case involving a second-order bimolecular reaction was analyzed using the film theory by Bhattacharya et al. (1987) and more recently by Al-Ubaidi et al. (1990). A penetration theory analysis of the same case was also attempted by Evans and Selim (1990).

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Slurry reactor studies of homogeneous and heterogeneous reactions

McCoy

Smith

1989

AIChE Journal

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A dynamic model is derived for simultaneous, homogeneous and heterogeneous, first-order reactions in a slurry reactor. The theory is applied to experimental data for the oxidation (with gaseous oxygen) of aqueous sulfite solutions which is first order in oxygen and zero order in sulfite. The homogeneous reaction is very slow at low pH (2-3) where the sulfur exists as dissolved SO, or HS03-, even when cobalt is added as a homogeneous catalyst. At higher pH (7-8.5), considerable homogeneous reaction occurs with and without cobalt ions. Here the predominant species are SO3' and HS03-. Activated carbon is not a heterogeneous catalyst at pH 7 or 8.5, but is responsible for nearly all the reaction at the low pH values. Analysis of the heterogeneous data indicates that the surface reaction between adsorbed oxygen and SO2 controls the rate rather than adsorption of oxygen.

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Dynamic analysis of homogeneous reactions in a stirred bubble reactor: Oxidation of sulfite

Cited by 9 publications

References 24 publications

Scale-down of Heterogeneous Catalytic Reduction Using a Bubble Column: Controlled Mass Transfer down to 3 cm³ Working Volume

Scale-down of Heterogeneous Catalytic Reduction Using a Bubble Column: Controlled Mass Transfer down to 3 cm³ Working Volume

Role of liquid reactant volatility in gas absorption with an exothermic reaction

Slurry reactor studies of homogeneous and heterogeneous reactions

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Dynamic analysis of homogeneous reactions in a stirred bubble reactor: Oxidation of sulfite

Cited by 9 publications

References 24 publications

Scale-down of Heterogeneous Catalytic Reduction Using a Bubble Column: Controlled Mass Transfer down to 3 cm3 Working Volume

Scale-down of Heterogeneous Catalytic Reduction Using a Bubble Column: Controlled Mass Transfer down to 3 cm3 Working Volume

Role of liquid reactant volatility in gas absorption with an exothermic reaction

Slurry reactor studies of homogeneous and heterogeneous reactions

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Product

Resources

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Scale-down of Heterogeneous Catalytic Reduction Using a Bubble Column: Controlled Mass Transfer down to 3 cm³ Working Volume

Scale-down of Heterogeneous Catalytic Reduction Using a Bubble Column: Controlled Mass Transfer down to 3 cm³ Working Volume