Slurry Reactors1A list of symbols used in the text is provided at the end of the chapter.

Nedeltchev, Stoyan; Schumpe, Adrian

doi:10.1002/9783527610044.hetcat0113

Cited by 6 publications

(3 citation statements)

References 199 publications

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“…The particles, however, need to be large enough to be filtered. In industrial processes, the minimal particle size is 10 μm, but sizes between 50 and 150 μm are common …”

Section: Glucose Oxidation On Heterogeneous Catalystsmentioning

confidence: 99%

Glucose Oxidation in Slurry Reactors and Rotating Foam Reactors

Tschentscher

Nijhuis

Schaaf

et al. 2011

Ind. Eng. Chem. Res.

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Glucose oxidation using platinum promoted by bismuth was studied as a three-phase model reaction. Using catalyst nanoparticles and measuring the oxygen concentration in the bulk liquid, the kinetic parameters and mass transfer characteristics were determined at a temperature of 333 K. The overall reaction rate was studied experimentally using three different support types: slurry catalysts, pellets, and a solid foam stirrer. The glucose conversion rate and the deactivation rate of the catalyst depend strongly on the ratio between mass transfer and reaction rate. At low catalyst concentrations, the glucose oxidation process is liquid–solid mass-transfer-limited. The block stirrer shows a superior performance over the slurry catalysts due to the high liquid–solid volumetric mass transfer coefficient. The bimodal pore size distribution of the catalyst layer further increases the conversion rate. Using slurry catalysts, a loading of 1 wt % in combination with pure oxygen feed is required to achieve acceptable conversion rates. Under these conditions, the gas–liquid mass transfer and partially the liquid–solid mass transfer are the rate-limiting steps. The foam block stirrer shows good gas–liquid mass transfer rates and high liquid–solid mass transfer rates, which still increase at high power input. Working under external mass transfer control and using this stirrer type, the catalyst loading can be strongly reduced to loadings less than 0.4 wt %, while the conversion rate remains comparable to slurry particles with loadings of 1 wt %. As the catalyst is fixed, attrition and agglomeration in high viscosity liquids are circumvented. There is further no need for filtration, and the catalyst can simply be reused.

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“…The particles, however, need to be large enough to be filtered. In industrial processes, the minimal particle size is 10 μm, but sizes between 50 and 150 μm are common …”

Section: Glucose Oxidation On Heterogeneous Catalystsmentioning

confidence: 99%

Glucose Oxidation in Slurry Reactors and Rotating Foam Reactors

Tschentscher

Nijhuis

Schaaf

et al. 2011

Ind. Eng. Chem. Res.

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“…This amount has to be added periodically. In low shear reactor sections also, agglomeration of particles can lead to internal diffusion limitations and the formation of byproducts . Therefore, several research groups are working on the use of highly porous materials, such as fiber mats, monoliths, and solid foams both as catalyst supports and stirrers in catalytic stirred reactors.…”

Section: Introductionmentioning

confidence: 99%

“…Using slurry particles, this can be achieved by reducing the particle size. This is, however, limited by downstream filter requirements to a minimal particle size of 10 μm . Commonly, particle diameters of 50 μm are used.…”

Section: Introductionmentioning

confidence: 99%

Liquid−Solid Mass Transfer in Agitated Slurry Reactors and Rotating Solid Foam Reactors

Tschentscher

Spijkers

Nijhuis

et al. 2010

Ind. Eng. Chem. Res.

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The liquid−solid mass transfer rate is studied for two three-phase reactor configurations, a stirred reactor and a rotating solid foam reactor, using the dissolution of copper by potassium dichromate as a model reaction. For the stirred reactor consisting of a Rushton stirrer and a slurry with small particles, the particle density has a large influence on the liquid−solid mass transfer rate. Heavy particles show high slip velocities, as their path is less influenced by the liquid turbulence. Furthermore, the mass transfer is enhanced by neighboring particles passing each other. In the case of solid copper particles, a k LS value of 3 × 10−3 ms−1 was observed. For particles having a density comparable to industrial catalyst supports, the k LS value is 1 order of magnitude lower. For the rotating foam block stirrer also, high k LS values of 2.5 × 10−3 ms−1 could be achieved due to the high liquid velocity along the foam struts. The influence of several parameters on the hydrodynamics and the liquid−solid mass transfer was studied. Among these, the foam block height, the foam pore size, and the space above the foam block stirrer have a large effect on the liquid circulation, the bubble formation, and therefore on the liquid−solid mass transfer. The reduction of the foam pore size has two counterbalancing effects, resulting only in a slight increase of the rate of mass transfer: (i) the liquid−solid interfacial area is increased; (ii) the liquid circulation is, however, reduced due to the higher frictional pressure drop. Gas bubbles passing the foam struts affect the liquid−solid mass transfer by inducing liquid velocity fluctuations. For the foam block stirrer, a maximum k LS a LS value of 0.6 s−1 was obtained. This shows great potential for further optimization of the liquid flow and therefore the mass transfer. An additional advantage of the foam stirrer reactor is that the solid phase is fixed and the catalyst does not need to be separated downstream from the reactor.

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